Help needed! Where to start with open baffle speakers

[vintage60]

Hi All

I've been inspired by a hifi friend of mine (Dave) to start my first "own build" hifi. Unlike me, he has been building his own speakers and turntables since he was 16 and is now an old hand. He's given me some pointers, but his plans and tech specs are too advanced for me.

I'm looking to build my own open baffle speakers with the help of 3 other hifi friends. All are called Dave (yes, it gets very confusing when 4 of your closest hifi pals are all called Dave) and all 3 are in the hifi/music business. None of us though have experience of building speakers. One is a guitarist in a band and repairs guitars, the second fixes amplifiers, turntables and CD players and the third fixes keyboards. I break things more often than fixing them so they will be doing most of the work.

So, there's our background and we motley crew are, at my instigation, tooled up to build our (I mean mine) first set of speakers and I have chosen to go down the open baffle route.

Do any AoS members have experience of building their own open baffles from scratch? I'm not looking to buy a kit and put it together - that's for wimps.

Any plans, pointers, useful websites to get data points/tech information and recommendations for woofers and tweeters would be gratefully received. I've seen a useful article on the Enjoy the Music website, but it does not have any pictures or plans and also some other articles - 6 Moons etc. I would like to start with a relatively simple and straightforward design please....I'm not up for trying to turn an abandoned old rowing boat into OBs.

Thanks in advance for any help anyone can give me.

[paulf-2007]

Audio circle have a dedicated section on open baffles, hundreds of threads. I have built open baffles with various drivers, lowthers being one with 15" eminence alpha bass drivers. I found making an open backed box for the bass was better. It's very easy to get good results with little knowledge. Trial and error is fun but audio circle will help.

[Infinitely Baffled]

These:
http://jelabsarch.blogspot.co.uk/2012/06/open-baffle.html
are absurdly easy to build, and you wouldn't belive how good they sound! They look sort of cool too in a nerdy, ironic kind of way.
IB

[fatmarley]

If I were to build an open baffle speaker It would probably be this - OBL-15 (http://www.troelsgravesen.dk/OBL-15.htm#SOUND)

What I wouldn't do Is use ONLY my ears to design the crossover. Lots of open baffle speaker designers do this, the frequency response will be all over the place and half your CD's will now be "recorded badly". Lampizator (http://lampizator.eu/SPEAKERS/PROJECTS/Speaker%20projects.html) Is probably the most famous guy for designing crossovers In this way.

Troels reverse engineers the Lampizator P17 somewhere here - P17 (http://www.troelsgravesen.dk/greencones.htm)

[RothwellAudio]

I'm not entirely sure what it is you want to know. Open baffle speakers are simply speakers on an open baffle instead of a box. The advantage is no boxiness and the disadvantage is reduced bass. The bigger the baffle, the closer they come to "infinite baffle" - which is the same as an extremely large box.
Whether to use a wide-range single driver or a two way or three way setup and how to design a suitable crossover are decisions/problems which are common to any loudspeaker design, not just open baffle.

Do you want to start completely from scratch with your own design or do you want to go with someone else's tried-and-tested design? Being an old cynic I'm wary of the thousands of speaker designs on the internet which all claim to deliver sound so fantastic that it's a revelation, though I'm sure lots of them are very good. But how do you tell which are the good ones?

This guy's website certainly looks impressive and he convinces me he knows what he's talking about:
http://www.troelsgravesen.dk/Diy_Loudspeaker_Projects.htm
A lot of his designs use expensive drivers and wouldn't be cheap to make, and most of his site is dedicated to reflex speakers, but there's some stuff about open baffles and lots of info about speakers in general.

My advice is to read as much as you can to build your knowledge base before you build your first speakers.

[walpurgis]

Being an old cynic I'm wary of the thousands of speaker designs on the internet which all claim to deliver sound so fantastic that it's a revelation

I agree.

If you have no experience of speaker building, start with something simple.

[vintage60]

Geoff - you are spot on. I want to start with something simple.

Andrew - you raise some very pertinent points. Its precisely because there are so many claims on the internet about peoples' designs being fabulous that I don't know where to start.

So I'm looking for an AoS member who has built his own OB that sounds nice or knows of a design which they have experienced which is positive. So yes, tried and tested would be great. I'm not looking for a revelation or absolute best since I don't believe in absolutes in HiFi.

In case it is relevant, I'm looking for a design that will work in a room that measures 18ft x 25ft although due to the design of the room, I'll be sitting around 12ft from the speakers. I have no problem giving them plenty of space behind as well as sides.

Soundwise, I am not a bass head so whilst bass is important, I'm not looking for something that will knock down the walls. Most important for me is a sweet and smooth midrange. I'm quite sensitive to high frequencies and find most modern speakers are too forward with their upper mids and highs which quickly becomes fatiguing to my ears. The best way I can describe the sound that I like is to say that I like the Harbeth sound, although I'm not trying to replicate a thin wall closed box design with an OB design. Just saying that neutrality, tonal balance, well controlled bass and honesty are my priorities.

So with that, any pointers as to woofers (how many should I have/make/size), tweeters, cross overs, size, shape etc., would be much appreciated.

I'll do research over the next few weeks to build my knowledge base.

Thanks all

[walpurgis]

Take a look at Fostex full range drivers. These are high quality speaker units. Wilmslow Audio stock a wide range and can probably advise on baffle or cabinet design.

http://www.wilmslow-audio.co.uk/fostex-56-c.asp

[paulf-2007]

Eminence alpha 15a are reasonably priced and sound very good. Something I learned from others on audio circle is to brace the drivers frame on the magnet, it gives cleaner sound up to 350hz, whereas without the bracing only to 200hz. Depending on which wide range driver you use with it will depend whether the bracing is needed, but then it may as well be done anyway.

[Ali Tait]

The Beta is better than the Alpha for OB. I'd use a pair of Betas per side up to 200hz, then cross over to something like Alpair 12P as in the below thread, or Visaton B200 is also a good choice.

Good info here-

http://www.audio-talk.co.uk/phpBB3/viewtopic.php?f=4&t=6916

I run my OB's actively, see thread here-

http://theartofsound.net/forum/showthread.php?49895-OB-Experiments

[struth]

full range speakers can be used as reflex type boxes. ive made several sets and they have all worked well. you can also add a simple tweeter with a cap if you wish if its not going high enough. just have to work out the reflex tube size.

[paulf-2007]

The Beta is better than the Alpha for OB. I'd use a pair of Betas per side up to 200hz, then cross over to something like Alpair 12P as in the below thread, or Visaton B200 is also a good choice.

Good info here-

http://www.audio-talk.co.uk/phpBB3/viewtopic.php?f=4&t=6916

I run my OB's actively, see thread here-

http://theartofsound.net/forum/showthread.php?49895-OB-Experimentsvisaton B200 are shouty, heard a pair in OB that usually were run active but as they were for sale I heard them passive. Not for me. I ran my alpha's up to 350hz with a front horn from 350hz - 2000hz, raal 140/15D ribbons at the top end with a deqx crossover.

Looked at your thread more about the otl than active ob's

[Ali Tait]

Cutting out the dust cap and using some Planet10 phase plugs sorts the shoutiness.

[bumpy]

Hi Thiha

I note you live in Essex. If you are any where near Bishops Stortford, you are most welcome to come over and listen to a very well constructed incarnation of the Endorphin P17 put together by Slawa at SW1X.

Cheers Chris

[ianlenco]

I've built a few OB's and enjoyed them all. Only downside is the size needed to get decent bass. Here's a few links that I found useful when I was getting started.



http://www.quarter-wave.com/Gallery/Gallery.html

http://www.iol.ie/~waltonaudio/ob.html

http://www.diyaudio.com/forums/multi-way/189847-introduction-designing-crossovers-without-measurement.html

http://www.diyaudioandvideo.com/Tables/XOver/1stOrder.aspx and links within the page

http://musicanddesign.com/tech.html

http://www.lotusgroupusa.com/Granada.htm

http://www.diyaudio.com/forums/full-range/ lots and lots of builds

http://www.quarter-wave.com/OBs/OB_Theory.html

http://www.quarter-wave.com/Project08/Project08.html MJK's build with Jordans

These were my favourites using Jordan full rangers and 15" Visaton woofers.

http://i.imgur.com/itf9weXh.jpg#gWPQG

[fatmarley]

Hi Thiha

I note you live in Essex. If you are any where near Bishops Stortford, you are most welcome to come over and listen to a very well constructed incarnation of the Endorphin P17 put together by Slawa at SW1X.

Cheers Chris


Did he design a proper crossover for these, or are they the standard ones from the Lampizator website?

I know someone (I wont mention his name) who heard a pair of the standard ones and described the sound as a "rollercoaster ride" (very far from a flat frequency response).

[RothwellAudio]

Just as an aside, I think it's worth pointing out that - although rarely referred to as such - Quad electrostatics are open baffle speakers. I'm not suggesting that the OP should make a pair of electrostatic speakers, just saying that panels/baffles of ESL size are capable of giving bass that satisfies most people. Well, I've never thought Quads were lacking bass, anyway.

[bumpy]

Did he design a proper crossover for these, or are they the standard ones from the Lampizator website?

I know someone (I wont mention his name) who heard a pair of the standard ones and described the sound as a "rollercoaster ride" (very far from a flat frequency response).

Believe me that Slawa would leave no stone unturned to get the best sound. He supplied his own crossovers using silver wiring throughout and top quality components such as Audionote capacitors etc. I cant give further details as

1. It would be unfair to plagiarise Slawa's IP
2. I don't really understand what was done :)

But they sure sound balanced across the frequency range.

[bumpy]

I know someone (I wont mention his name) who heard a pair of the standard ones and described the sound as a "rollercoaster ride" (very far from a flat frequency response).

Other approaches that I think are flawed in terms of musicality are

1. Going active on the base with masses of EQ
2. Boxing in, or partly boxing in, the base driver, thus moving away from the freedom of a true open baffle.

[Macca]

The bass is the bit that is hard to get right. Best I have heard were Gordon's with the dipole bass - think they were a Troel's design. Build some of them, you won't be disappointed.

[fatmarley]

Believe me that Slawa would leave no stone unturned to get the best sound. He supplied his own crossovers using silver wiring throughout and top quality components such as Audionote capacitors etc. I cant give further details as

1. It would be unfair to plagiarise Slawa's IP
2. I don't really understand what was done :)

But they sure sound balanced across the frequency range.

Sounds like he must have used a better crossover than the standard one.

[fatmarley]

Other approaches that I think are flawed in terms of musicality are

1. Going active on the base with masses of EQ
2. Boxing in, or partly boxing in, the base driver, thus moving away from the freedom of a true open baffle.

Very surprised at your comment on going active In the bass. Although I've never tried It (yet), It seems like the logical thing to do.

Yes, I've heard open baffle bass (and midrange) Is supposed to be hard to beat. Just a shame you need so much baffle/cone area to get decent bass. There's also the fact that you have to lose a huge amount of efficiency to get some deep bass (assuming you want a flat response down to low frequencies).

[vintage60]

Thank you everyone! Too many to thank everyone in person so a group thanks to you all for your inputs.

I'm on holiday from this weekend so won't bother buying any books at the airport. Plenty to read up on following your suggestions.

I've heard of Slawa at SW1X - he lives quite close to me so I had been thinking of going over to his place to hear his OBs and to get some pointers from him.

From what I've heard, he takes his hifi very seriously and uses only top grade parts and materials.

Chris - I'm only 20 minutes from Bishops Stortford so would love to drop by one day and hear your speakers. Thank you for the kind offer.

I think I will start with something absurdly simple and work my way up. My mate Dave has built 10 OBs over the years and it is only his later ones that he was happy with. As he says, you need to build up the experience and knowledge and learn from trial and error.

Thank you all!

[bumpy]

Thank you everyone! Too many to thank everyone in person so a group thanks to you all for your inputs.

I'm on holiday from this weekend so won't bother buying any books at the airport. Plenty to read up on following your suggestions.

I've heard of Slawa at SW1X - he lives quite close to me so I had been thinking of going over to his place to hear his OBs and to get some pointers from him.

From what I've heard, he takes his hifi very seriously and uses only top grade parts and materials.

Chris - I'm only 20 minutes from Bishops Stortford so would love to drop by one day and hear your speakers. Thank you for the kind offer.

I think I will start with something absurdly simple and work my way up. My mate Dave has built 10 OBs over the years and it is only his later ones that he was happy with. As he says, you need to build up the experience and knowledge and learn from trial and error.

Thank you all!

OK Thiha when you're ready :)

[bumpy]

Very surprised at your comment on going active In the bass. Although I've never tried It (yet), It seems like the logical thing to do.

Over the years I have seen how adding more and more complexity robs the music of its magic. Its probably more about timing, than getting the frequencies right.

I have run active subs before on a horn based system - pair of expensive 15 inch drivers in stereo boxes set up with a TACT preamplifier. Tuning frequency curves and time alignment gave plenty of scope for adjustment and impressed casual visitors with low frequencies but it never hit the spot in terms of magic, reality, or relaxed listening. I have heard sounds like this at a Hi Fi shows recently and in the main was not impressed.

The key for me is that in general adding complexity to a Hi Fi system cannot add magic, only rob it. So simplicity, but of the highest quality you can afford, is best.

[RothwellAudio]

Very surprised at your comment on going active In the bass. Although I've never tried It (yet), It seems like the logical thing to do.
It seems to me like a very illogical thing to do. The bass effectively disappears because the "positive" bass in front of the baffle and the "negative" bass behind it cancel each other out. Infinite baffles - or sealed boxes - were invented to prevent the cancellation. Simply sending more bass to the driver via heavy EQ will just create more "negative" bass to cancel the "positive" bass - hence no net gain, just more stress for the driver.

[walpurgis]

The ultimate OB would vent rearwards LF through an exterior house wall, but then it would cease to be OB, but a true IB. (well nearly) :)

[fatmarley]

It seems to me like a very illogical thing to do. The bass effectively disappears because the "positive" bass in front of the baffle and the "negative" bass behind it cancel each other out. Infinite baffles - or sealed boxes - were invented to prevent the cancellation. Simply sending more bass to the driver via heavy EQ will just create more "negative" bass to cancel the "positive" bass - hence no net gain, just more stress for the driver.


What you're saying Is, If you turn up the volume on an open baffle bass driver, the "negative" bass will cancel the "positive" and It wont go any louder.


I think you were trying to say, don't use positive EQ to fill In the "dips" In the low frequency response. That's not what I was suggesting. If you build an open baffle bass driver you will have to use EQ, whether active or passive, to get a flat response. Obviously, you lower the peaks In the frequency response down until you get something near flat.
With active bass you can make EQ and crossover/phase adjustments to suit any room. You can change your mid/tweeters and not have to buy new passive components to make the system work as a whole. The components to make passive low pass filters on bass drivers are usually big and expensive, so any mistakes here would be costly and time consuming (good quality, low DCR Inductors are often hand made).
The other advantage of active bass Is that you can make adjustment 'on-the-fly', so It's far quicker and easier to get the crossover sorted.

[SW1X]

Thank you everyone! Too many to thank everyone in person so a group thanks to you all for your inputs.

I'm on holiday from this weekend so won't bother buying any books at the airport. Plenty to read up on following your suggestions.

I've heard of Slawa at SW1X - he lives quite close to me so I had been thinking of going over to his place to hear his OBs and to get some pointers from him.

From what I've heard, he takes his hifi very seriously and uses only top grade parts and materials.

Chris - I'm only 20 minutes from Bishops Stortford so would love to drop by one day and hear your speakers. Thank you for the kind offer.

I think I will start with something absurdly simple and work my way up. My mate Dave has built 10 OBs over the years and it is only his later ones that he was happy with. As he says, you need to build up the experience and knowledge and learn from trial and error.

Thank you all!

Greetings,

Just noticed this thread.

Building speakers is easy- building speakers to reproduce music at its maximum musical performance is hard. If time and cost is not a constraint, I would highly recommend to start building your own speakers as every material and its environment contributes to its unique sound signature. On top of that everybody has different expectations anyway. So "one size fits all" approach does not really work with speakers. Open back speakers are heavily affected the room size & shape as the room becomes the extension of the speakers even more so than with closed cabinet designs.

Knowledge is everything and experimentation is the key. Having said that most of the OB speakers I have seen over the years have major flaws in either their design or their implementation, original P17 including.

The most common flaw is the choice of drivers, their position and the proportion/size of the cabinets resulting in thin, lame or/and dissonant sounding mid-bass- the most import frequency range when reproducing music.

Using active X-over, EQ compensation and active woofers to compensate the short comings of bass is a sub optimal approach. In 9.9 out of 10 cases, it results in dissonance in the mid-bass area.

S

[RothwellAudio]

What you're saying Is, If you turn up the volume on an open baffle bass driver, the "negative" bass will cancel the "positive" and It wont go any louder.
I'm really saying that the bass limit is set by the size of the baffle and trying to compensate for a tiny baffle by using massive EQ isn't a great idea.
Of course, you're quite correct that active EQ for crossover slopes and fine tuning etc. is perfectly valid.

[SW1X]

I'm really saying that the bass limit is set by the size of the baffle and trying to compensate for a tiny baffle by using massive EQ isn't a great idea.
Of course, you're quite correct that active EQ for crossover slopes and fine tuning etc. is perfectly valid.

Active EQ and/or boxed woofer design is too much of a compromise as it defies the purpose of the open back speaker design.

England is not an ideal country for open back speakers design as the OB needs to be massive in size (in order to sound appropriately) and requires larger rooms yet the space comes at premium in most living rooms.

These are some of the reasons as why people build small speakers and end up not liking them.

S

[RothwellAudio]

Active EQ and/or boxed woofer design is too much of a compromise as it defies the purpose of the open back speaker design.

Obviously, if you box in the woofer it is no longer an open baffle. I'm not sure how active EQ would defy the purpose of an open baffle though.

[SW1X]

Obviously, if you box in the woofer it is no longer an open baffle. I'm not sure how active EQ would defy the purpose of an open baffle though.

Generally, any type of active or passive equalization tends to deaden musicality because of the added complexity (by having additional passive components, resistors in particular and/or active components) in the equalizing circuits.

That defeats the purpose (of enhanced dynamics and the absence of bass overhang) of an open back speaker design. The major downside is the additional misalignment in timing because of the EQ processes.

The better solution is to match the drivers or/and to minimize their number.

S

[fatmarley]

I'm really saying that the bass limit is set by the size of the baffle and trying to compensate for a tiny baffle by using massive EQ isn't a great idea.

That's just another way of saying what I said In post #22

[fatmarley]

The better solution is to match the drivers or/and to minimize their number.

S

What do you mean?

[SW1X]

Those who are seeking flat response, especially in the bass on a finite OB are seeking it in vain. There is simply no "free lunch" here. Actively pursuing a flatter response by use of excessive filtering or equalization usually comes at a cost of musicality and is generally a bad idea. No X-over or EQ is able to compensate for short comings of a driver or speaker design without killing music!

S

[fatmarley]

Those who are seeking flat response, especially in the bass on a finite OB are seeking it in vain. There is simply no "free lunch" here. Actively pursuing a flatter response by use of excessive filtering or equalization usually comes at a cost of musicality and is generally a bad idea. No X-over or EQ is able to compensate for short comings of a driver or speaker design without killing music!

S

If that's aimed at me. That's not what I asked.

What do you mean by this? - Quote "The better solution is to match the drivers or/and to minimize their number."

[SW1X]

Matching drivers is a complex process. Not only do they need to have a close impedance behavior and similar sensitivity (taking into account 6dB/octave the roll-off) but must also be made of similar materials in order to complement each other.
Ideally drivers should sound great together without a X-over. If they do not, those drivers do not match. Has anyone tried to X-over AlNiCo with paper cone/copper voice coil driver and a Neodynium with platic cone and alu voice coil?

[fatmarley]

Matching drivers is a complex process. Not only do they need to have a close impedance behavior and similar sensitivity (taking into account 6dB/octave the roll-off) but must also be made of similar materials in order to complement each other.
Ideally drivers should sound great together without a X-over. If they do not, those drivers do not match. Has anyone tried to X-over AlNiCo with paper cone/copper voice coil driver and a Neodynium with platic cone and alu voice coil?

We were talking about the low frequency loss caused by the back wave of the driver wrapping round the front of the baffle. You said a better solution to EQ was to - Quote "The better solution is to match the drivers or/and to minimize their number." - What do you mean?

[SW1X]

The best (better) alternative to EQ is to make your OB infinitely large, i.e. make a hole in a wall and place a driver in it and customize the acoustic design of the room accordingly similar to the way Bernard Salabert, the owner of PHY drivers did.

http://www.6moons.com/industryfeatures/phy/phy.html

S

[walpurgis]

I said much the same.


The ultimate OB would vent rearwards LF through an exterior house wall, but then it would cease to be OB, but a true IB. (well nearly) :)

[fatmarley]

The best (better) alternative to EQ is to make your OB infinitely large, i.e. make a hole in a wall and place a driver in it and customize the acoustic design of the room accordingly similar to the way Bernard Salabert, the owner of PHY drivers did.

http://www.6moons.com/industryfeatures/phy/phy.html

S

Not sure what that's got to do with "matching drivers or minimise their numbers" but I agree that would be the best solution. If I could do It, I wouldn't think twice about It.
There was a guy over at diyaudio that bought some cheap fullrange drivers and fitted them Into the wall. He was shocked at how good they sounded. To my ears, most high efficiency loudspeakers sound more alive and realistic (especially at low volumes). I think the fact that you aren't losing 5 to 6db of efficiency when you flush mount a speaker In the wall Is a big part of what gives a better sound (also less components In the signal path)

I personally wouldn't build a open baffle bass speaker (I would mid and treble though) because of the huge loss In low frequencies. Active bass Is something I want to try sometime, but In a sealed box. I'm not Interested In active for midrange and treble because I know what damage more components In the signal path can do to those delicate frequencies.

[fatmarley]

I said much the same.

I was going to quote you on that but you didn't mention flush mounting the drivers (although I assumed that's what you meant)

[SW1X]

Not sure what that's got to do with "matching drivers or minimise their numbers" but I agree that would be the best solution. If I could do It, I wouldn't think twice about It.
There was a guy over at diyaudio that bought some cheap fullrange drivers and fitted them Into the wall. He was shocked at how good they sounded. To my ears, most high efficiency loudspeakers sound more alive and realistic (especially at low volumes). I think the fact that you aren't losing 5 to 6db of efficiency when you flush mount a speaker In the wall Is a big part of what gives a better sound (also less components In the signal path)

I personally wouldn't build a open baffle bass speaker (I would mid and treble though) because of the huge loss In low frequencies. Active bass Is something I want to try sometime, but In a sealed box. I'm not Interested In active for midrange and treble because I know what damage more components In the signal path can do to those delicate frequencies.

Not sure I mentioned it before but I am not a big fan a small & pure dipole designs because of the low frequency wave cancellation. I prefer large & folded (closer to open box) speaker design, which I call open back speakers. There is always some sort of trade off or a compromise in acoustic design. Personally, I would not go for closed boxes even for bass even if losses are huge. The sound of a driver in sealed box with a driver on an open back do not match harmonically- that is what I partly meant by matching. In my book, the least compromised (musically) but most feasible way, is to use a 2 sqm wall with folded sides design of larger size (but not too large relative to the front) or a really large horn folded WE type. 2 - 3 way max with minimum (and resistor-less) or no X-over based on field coil drivers.

If one does it right and the rest of the system is up to it, the sound one gets is to die for.

S

[vintage60]

As the OP who started this thread, I did not expect it to generate such a lively debate. Clearly there are many here on AoS with lots of knowledge...and diverse views!

I'm not ashamed to say this, but most of what you guys are saying has gone totally over my head, but hey, that just shows how much I have yet to learn.

Reading your various posts, I did have a few (more basic) questions:

1. given the wide range of driver/tweeter manufacturers out there - eminent technologies, fostex, seas, scanspeak, vifa etc., is there a combination of woofer and tweeter that goes well in an OB set up (without breaking the bank)?

2. for a first timer like me, should I start with just one woofer and one tweeter for each speaker or have more? (I recognise the answer might have a lot to do with the size of my room and acoustics etc.)

3. should I build my own X-over or buy a ready made one and tweak it? Or maybe no X-over at all and do what Slawa suggests, base on field coil drivers?

My room is about 18ft x 30ft although I sit facing the short length. Walls are fairly bare and ceiling around 15ft high. Floor is suspended wooden slats but largely covered with rugs. So quite a few hard surfaces, but quite airy.

Slawa - glad you joined the thread. It was seeing pictures of one of your OBs for sale on HiFi Wigwam last year that piqued my interest in OBs. Then talking to my friend Dave earlier this year gave me the encouragement to take the plunge. So you are the genesis of this project of mine. Would love to speak to you in person one day and maybe hear your OBs.

Thiha

[SW1X]

As the OP who started this thread, I did not expect it to generate such a lively debate. Clearly there are many here on AoS with lots of knowledge...and diverse views!

I'm not ashamed to say this, but most of what you guys are saying has gone totally over my head, but hey, that just shows how much I have yet to learn.

Reading your various posts, I did have a few (more basic) questions:

1. given the wide range of driver/tweeter manufacturers out there - eminent technologies, fostex, seas, scanspeak, vifa etc., is there a combination of woofer and tweeter that goes well in an OB set up (without breaking the bank)?

2. for a first timer like me, should I start with just one woofer and one tweeter for each speaker or have more? (I recognise the answer might have a lot to do with the size of my room and acoustics etc.)

3. should I build my own X-over or buy a ready made one and tweak it? Or maybe no X-over at all and do what Slawa suggests, base on field coil drivers?

My room is about 18ft x 30ft although I sit facing the short length. Walls are fairly bare and ceiling around 15ft high. Floor is suspended wooden slats but largely covered with rugs. So quite a few hard surfaces, but quite airy.

Slawa - glad you joined the thread. It was seeing pictures of one of your OBs for sale on HiFi Wigwam last year that piqued my interest in OBs. Then talking to my friend Dave earlier this year gave me the encouragement to take the plunge. So you are the genesis of this project of mine. Would love to speak to you in person one day and maybe hear your OBs.

Thiha

You are welcome, Thiha. I feel honored by your comments.

1. A definition of breaking a bank varies in high end audio significantly. Everything is being relative. (http://sw1xad.co.uk/high-end-audio-paradox/)
Of course there is a combination of drivers that matches harmonically and there are plenty that do not. Those combinations that match usually break the bank. :)
2. A woofer and a tweeter is a good starting point.
3. Build a simple 1st order or max second order filter. Experiment with different caps and choke values to get the feeling.

After familiarising myself with the OB and acoustic theory, I would start with a large prototype baffle made of MDF with normalised cut outs for different drivers if you really wanted to start from scratch. Once you get the right combination, I would experiment with baffle design and driver position. Eventually after 5-10 years of experimentation only then move to build a proper cabinet made of solid or high quality ply wood. There is no end in high end.

Otherwise I would choose a good design (unfortunately there are not many out there) and try to replicate it.

S

[fatmarley]

There is always some sort of trade off or a compromise in acoustic design. Personally, I would not go for closed boxes even for bass even if losses are huge. The sound of a driver in sealed box with a driver on an open back do not match harmonically- that is what I partly meant by matching. In my book, the least compromised (musically) but most feasible way, is to use a 2 sqm wall with folded sides design of larger size (but not too large relative to the front) or a really large horn folded WE type. 2 - 3 way max with minimum (and resistor-less) or no X-over based on field coil drivers.

If one does it right and the rest of the system is up to it, the sound one gets is to die for.

S

That Is your subjective opinion, not a fact. Look at all the flagship speakers designs from various manufacturers and they all use very different technologies and they all sound very different. There's absolutely wrong with mating a sealed bass driver with an open baffle midrange. Done properly, you wont hear the joins.

[fatmarley]

3. Build a simple 1st order or max second order filter. Experiment with different caps and choke values to get the feeling.


S

It's quite obvious you know nothing about crossover design.

[SW1X]

That Is your subjective opinion, not a fact. Look at all the flagship speakers designs from various manufacturers and they all use very different technologies and they all sound very different. There's absolutely wrong with mating a sealed bass driver with an open baffle midrange. Done properly, you wont hear the joins.

Everything is being relative. Are you speaking out of your own experience? Referring to flagship designs of some manufacturers does not prove anything nor offers any substance- your experience does.
Feel free to experiment and then come back to me to agree or to disagree.

S

[walpurgis]

It's quite obvious you know nothing about crossover design.

Argue your principles by all means Matt. But avoid personal comments like this! Thanks.

[SW1X]

It's quite obvious you know nothing about crossover design.

Obviously, you do know a lot and you know much better than me.

[bumpy]

There's absolutely wrong with mating a sealed bass driver with an open baffle midrange. Done properly, you wont hear the joins.

Its true what you say, but you no longer have an open baffle speaker. The lower frequecies are coming from a sealed box, so gone are the attributes that open baffles offer, such as an open non boxy sound and a vast reduction in room resonances.

[fatmarley]

Referring to flagship designs of some manufacturers does not prove anything nor offers any substance- your experience does.

S

It proves that all high end manufacturers have very different Ideas of what makes the best speaker. There are so many variables Involved In loudspeaker design, that to say your way Is the "least compromised" Is just your subjective opinion and carries no weight at all.

[fatmarley]

Argue your principles by all means Matt. But avoid personal comments like this! Thanks.

Ok, sorry Geoff.

I'll go back to that post and ask a sensible question.

[fatmarley]

3. Build a simple 1st order or max second order filter. Experiment with different caps and choke values to get the feeling.


S

Is that first order electrical or acoustic?

[walpurgis]

Is that first order electrical or acoustic?

Depending on interpretation, surely these are similar?

[fatmarley]

Depending on interpretation, surely these are similar?

No, they are two very different things.

[walpurgis]

I don't claim to be any kind of expert with crossovers, but have designed and built a few over the last forty years or so (probably not great ones :)) and the words 'acoustic' and 'electrical' have been interchangeable in my experience in this context.

[fatmarley]

I don't claim to be any kind of expert with crossovers, but have designed and built a few over the last forty years or so (probably not great ones :)) and the words 'acoustic' and 'electrical' have been interchangeable in my experience in this context.

They're definitely not Interchangeable.

[Macca]

As the OP who started this thread, I did not expect it to generate such a lively debate. Clearly there are many here on AoS with lots of knowledge...and diverse views!

I'm not ashamed to say this, but most of what you guys are saying has gone totally over my head, but hey, that just shows how much I have yet to learn.

Reading your various posts, I did have a few (more basic) questions:

1. given the wide range of driver/tweeter manufacturers out there - eminent technologies, fostex, seas, scanspeak, vifa etc., is there a combination of woofer and tweeter that goes well in an OB set up (without breaking the bank)?

2. for a first timer like me, should I start with just one woofer and one tweeter for each speaker or have more? (I recognise the answer might have a lot to do with the size of my room and acoustics etc.)

3. should I build my own X-over or buy a ready made one and tweak it? Or maybe no X-over at all and do what Slawa suggests, base on field coil drivers?

My room is about 18ft x 30ft although I sit facing the short length. Walls are fairly bare and ceiling around 15ft high. Floor is suspended wooden slats but largely covered with rugs. So quite a few hard surfaces, but quite airy.

Slawa - glad you joined the thread. It was seeing pictures of one of your OBs for sale on HiFi Wigwam last year that piqued my interest in OBs. Then talking to my friend Dave earlier this year gave me the encouragement to take the plunge. So you are the genesis of this project of mine. Would love to speak to you in person one day and maybe hear your OBs.

Thiha

You have a big advantage with that room but the best way to use an open baffle speaker is to have it firing down the length of the room, not across the width.

The big problem with open baffles is bass cancellation. Bass units go in boxes for a reason, because if you don't put the bass in a box you get cancellation from the return wave and.... no bass or heavily curtailed bass. With 30' to play with you can have the bulk of the room behind the speaker, giving the bass wave a chance to dissipate down the length rather than return. Unlike most rooms you should be able to get pretty good bass from an open baffle by setting them up like that. Have 15' to 20' of the room behind the speakers.

In general terms re open baffles, people do claim that bass sounds more natural etc without the box. I'm not so sure. The various monitoring speakers in studios are not open baffles. Recordings tend to be mixed to sound good on these speakers - not on open baffles. If you listen to a lot of music that has a lot of bass energy below 40 Hz (dance music, electronica, organ and so forth) then I wouldn't recommend going for an open baffle. At least not for the bass. The are not intrinsically better, they are, like all speaker designs, just another set of compromises.

[fatmarley]

As the OP who started this thread, I did not expect it to generate such a lively debate. Clearly there are many here on AoS with lots of knowledge...and diverse views!

I'm not ashamed to say this, but most of what you guys are saying has gone totally over my head, but hey, that just shows how much I have yet to learn.

Reading your various posts, I did have a few (more basic) questions:

1. given the wide range of driver/tweeter manufacturers out there - eminent technologies, fostex, seas, scanspeak, vifa etc., is there a combination of woofer and tweeter that goes well in an OB set up (without breaking the bank)?

2. for a first timer like me, should I start with just one woofer and one tweeter for each speaker or have more? (I recognise the answer might have a lot to do with the size of my room and acoustics etc.)

3. should I build my own X-over or buy a ready made one and tweak it? Or maybe no X-over at all and do what Slawa suggests, base on field coil drivers?

My room is about 18ft x 30ft although I sit facing the short length. Walls are fairly bare and ceiling around 15ft high. Floor is suspended wooden slats but largely covered with rugs. So quite a few hard surfaces, but quite airy.

Slawa - glad you joined the thread. It was seeing pictures of one of your OBs for sale on HiFi Wigwam last year that piqued my interest in OBs. Then talking to my friend Dave earlier this year gave me the encouragement to take the plunge. So you are the genesis of this project of mine. Would love to speak to you in person one day and maybe hear your OBs.

Thiha

1. Two drivers that get mentioned a lot on open baffle threads are the Visaton B200 and the Eminence Alpha 15a. QTS Is probably the most Important t/s parameter to look at (you'll find It in the manufacturers data sheets) for open baffle speaker. I'd be looking at a QTS of around 0.7 and higher. Ive heard some people say the Eminence Alpha 15A sounds boomy. I don't know If this Is because of the high QTS (1.26), bad crossover design or the fact that people often mount It almost touching the floor (maybe a combination of all three).
I would'nt worry about the matching the midrange/tweeters. Some of the best speaker designs ever made coupled different driver materials successfully - The old Epos ES14 used a metal tweeter and a plastic mid and Is still very popular now. As long as you use good quality drivers and the crossover Is done right, you shouldn't hear the joins between the mid/tweet.

2. Yes, keep It simple. More drivers will make crossover design much harder.

3. When I tell people crossover design Is hard (assuming you're a beginner), I feel It goes In one ear and out the other. I did some work for a speaker manufacturer once and It didn't matter how many times I told him or even showed him that simple crossovers, done by ear, don't work. He wouldn't believe me (Just to say that simple crossovers can and obviously do work with the right drivers but there was no chance with drivers he chose)
Off-the-shelf crossovers and online crossover calculators are a complete waste of time. They assume your drivers have a perfectly flat frequency response and that the Impedance Is also perfectly flat.
When I say crossover design Is hard, what I really mean Is, If you make one tiny mistake with the whole process of taking accurate measurements, Importing them Into your software and all the things that you need to Input. Your crossover model will not match reality.
If you like a challenge and are willing to put a lot of effort In, I can guide you In the right direction.
Most people just go active because It's so much easier to get the crossover right.

[bumpy]

You have a big advantage with that room but the best way to use an open baffle speaker is to have it firing down the length of the room, not across the width.

The big problem with open baffles is bass cancellation. Bass units go in boxes for a reason, because if you don't put the bass in a box you get cancellation from the return wave and.... no bass or heavily curtailed bass. With 30' to play with you can have the bulk of the room behind the speaker, giving the bass wave a chance to dissipate down the length rather than return. Unlike most rooms you should be able to get pretty good bass from an open baffle by setting them up like that. Have 15' to 20' of the room behind the speakers.

In general terms re open baffles, people do claim that bass sounds more natural etc without the box. I'm not so sure. The various monitoring speakers in studios are not open baffles. Recordings tend to be mixed to sound good on these speakers - not on open baffles. If you listen to a lot of music that has a lot of bass energy below 40 Hz (dance music, electronica, organ and so forth) then I wouldn't recommend going for an open baffle. At least not for the bass. The are not intrinsically better, they are, like all speaker designs, just another set of compromises.

Don't be put off by room restrictions. I have broken all the above guidance in that I fire across the narrow dimension of my room and listen in the near field. Baffles are barely 1m off the rear wall but are angled inwards which I think 'disrupts' the rear reflections reducing cancellations.

[walpurgis]

the fact that people often mount It almost touching the floor

I've noticed that tendency for folk to mount bass drivers very close to the floor. When you consider the wavelengths involved it really has no great benefit at low frequencies.

[fatmarley]

I've noticed that tendency for folk to mount bass drivers very close to the floor. When you consider the wavelengths involved it really has no great benefit at low frequencies.

That's right. According to my simulations. The boost from floor mounting a woofer Is centered around about 150Hz, so not really doing much to help.
Also, with a woofer that low, you can often feel the vibrations of the low frequencies coupling to the floor and adding distortion.

[bumpy]

I've noticed that tendency for folk to mount bass drivers very close to the floor. When you consider the wavelengths involved it really has no great benefit at low frequencies.

But is does maximise the height of the baffle :)

[Macca]

Don't be put off by room restrictions. I have broken all the above guidance in that I fire across the narrow dimension of my room and listen in the near field. Baffles are barely 1m off the rear wall but are angled inwards which I think 'disrupts' the rear reflections reducing cancellations.

I love breaking the rules. Especially in hi-fi where a lot of them are bollox to begin with. But for a dipole or open baffle you really need as much distance behind it as possible to get optimal performance.

[bumpy]

I love breaking the rules. Especially in hi-fi where a lot of them are bollox to begin with. But for a dipole or open baffle you really need as much distance behind it as possible to get optimal performance.

I am probably helped by the fact I only run my system at mid volume. At low volume late at night its still magic, but I do notice that when friends ask me to wind it up it can get a bit ragged. I do plan to try some sound treatments on the wall behind. The other advantage of running at modest volume with 2 watt monoblocks is that I can run the midrange driver without crossover restrictions above or below. Again a reduction in complexity.

[RothwellAudio]

I love breaking the rules. Especially in hi-fi where a lot of them are bollox to begin with.
Interesting. Which hi-fi rules do you consider to be bollox? I ask because I agree with Scotty when he says "ye canno' change the laws of physics, captain".

[vintage60]

Thank you all.

I went back into my old emails and found one from my friend Dave who tested 5 different woofers including eminent technology alpha 15a but concluded that the best ones were Acoustic Elegance Dipole 15. They are US$359 each is most definitely not cheap! He combined them with AER full range drivers.

Thanks for the advice about not buying ready made X-overs. That's saved me from wasting money.

Keep them coming!

[Arkless Electronics]

Thank you all.

I went back into my old emails and found one from my friend Dave who tested 5 different woofers including eminent technology alpha 15a but concluded that the best ones were Acoustic Elegance Dipole 15. They are US$359 each is most definitely not cheap! He combined them with AER full range drivers.

Thanks for the advice about not buying ready made X-overs. That's saved me from wasting money.

Keep them coming!

That's interesting that there is now a bass unit made specifically for OB use. The lack of suitable bass units and having make do with the limitations of the Eminence units is always a big problem! Back in history there was the Wharfedale SFB3 open baffle speaker which did have a 12" unit they designed specially for the application.

[Macca]

Interesting. Which hi-fi rules do you consider to be bollox? I ask because I agree with Scotty when he says "ye canno' change the laws of physics, captain".

One for a new thread I think.

[fatmarley]

That's interesting that there is now a bass unit made specifically for OB use.

Just had a quick look at the specs and It looks like a cracking driver for open baffle use. Couldn't see a frequency response graph though...

[vintage60]

Matt - may mate Dave said the same thing as you about the Eminence Alphas...they were boomy and had muddy bass. He also tried Lowthers (I don't know which ones) and some others. Said AE Dipole 15s were the best of the bunch (really, really good). He also said that the drivers in Voxativ speakers are great, but you need to be a millionnaire!

[Arkless Electronics]

Just had a quick look at the specs and It looks like a cracking driver for open baffle use. Couldn't see a frequency response graph though...

Yeah the big problem is that woofers for OB need pretty specific characteristics and as there is no market for such things beyond a few audiophiles non have been built... until this one it seems.... I would have thought a foam surround would make it better still but there's the old rot problem..

[petrat]

Don't be put off by room restrictions. I have broken all the above guidance in that I fire across the narrow dimension of my room and listen in the near field. Baffles are barely 1m off the rear wall but are angled inwards which I think 'disrupts' the rear reflections reducing cancellations.

Yes, Chris, but your set-up takes 'near-field' to a whole other level ... probably more accurate to describe your OBs as very large open-back headphones :lol:

[paulf-2007]

Has anybody measured the spl from the rear of a driver in open baffle and compared it to the measurement from the front. I suspect it would be less from the rear. A driver pushes air and due to the cone shape must move more air at the front than the rear, the rear is shaped more like an arrow head compared to the front. I ran open baffle bass 2' from the wall with no loss of spl. On the other hand I accidentally wired my zu omen speakers out of phase and lost the bass very noticeably. What seems logical in theory doesn't always work in practice.o

[fatmarley]

Matt - may mate Dave said the same thing as you about the Eminence Alphas...they were boomy and had muddy bass. He also tried Lowthers (I don't know which ones) and some others. Said AE Dipole 15s were the best of the bunch (really, really good). He also said that the drivers in Voxativ speakers are great, but you need to be a millionnaire!

Looks like you've got your woofers sorted then. Just need to decide on mids and tweeters (assuming you want to start with a 3 way)

[fatmarley]

I would have thought a foam surround would make it better still but there's the old rot problem..

Foamed rubber Is almost good apparently. Doesn't rot either.

[Macca]

Has anybody measured the spl from the rear of a driver in open baffle and compared it to the measurement from the front. I suspect it would be less from the rear. A driver pushes air and due to the cone shape must move more air at the front than the rear, the rear is shaped more like an arrow head compared to the front. I ran open baffle bass 2' from the wall with no loss of spl. On the other hand I accidentally wired my zu omen speakers out of phase and lost the bass very noticeably. What seems logical in theory doesn't always work in practice.o

Isn't there something in physics about an 'equal and opposite reaction'? You lose bass frequencies progressively as the out of phase return wave cancels the forward wave. So you lose bass, not spl. I think it works out that to cancel down to 40 Hz you need a 20' wide baffle. You'll get the harmonics which is why it will subjectively still have bass, but you won't get the fundamentals.

[fatmarley]

Yes, Chris, but your set-up takes 'near-field' to a whole other level ... probably more accurate to describe your OBs as very large open-back headphones :lol:

I like near-field listening. You get more of the direct sound with less reflections. Reflections really mess up the sound.

Some old Epos ES11 I had years ago were absolutely bristling with energy when I had them set up near-field (not at all harsh either). Moved them downstairs to the main system (mid to far-field) and they transformed Into dull, boomy, lifeless things.

[Macca]

I like near-field listening. You get more of the direct sound with less reflections. Reflections really mess up the sound.
.

They can, but they are also essential. Otherwise the optimal listening room would be an anechoic chamber. And that is demonstrably not the case.

[walpurgis]

Use headphones. They are about as 'nearfield' as you can get. With the driver/ear distances involved, non-subharmonic reflections will only have effects above maybe 20kHz.

[paulf-2007]

Isn't there something in physics about an 'equal and opposite reaction'? You lose bass frequencies progressively as the out of phase return wave cancels the forward wave. So you lose bass, not spl. I think it works out that to cancel down to 40 Hz you need a 20' wide baffle. You'll get the harmonics which is why it will subjectively still have bass, but you won't get the fundamentals. my brain hurts:)

[walpurgis]

Isn't there something in physics about an 'equal and opposite reaction'? You lose bass frequencies progressively as the out of phase return wave cancels the forward wave. So you lose bass, not spl. I think it works out that to cancel down to 40 Hz you need a 20' wide baffle. You'll get the harmonics which is why it will subjectively still have bass, but you won't get the fundamentals.

If only it were that simple. Room size and boundary positions and distances and angles and reflections may allow fundamentals to occur either from front or rear radiation. Don't forget, front and rear O/B output are separated by the size of the baffle and not all the output will necessarily directly meet the output from the other side of the baffle.

[Macca]

If only it were that simple. Room size and boundary positions and distances and angles and reflections may allow fundamentals to occur either from front or rear radiation. Don't forget, front and rear O/B output are separated by the size of the baffle and not all the output will necessarily directly meet the output from the other side of the baffle.

True but that all depends on the size of the baffle, and whether it has sides to it or not. Most OBs don't seem to have baffles much wider than the drive units so you are going to get pretty much full cancellation in the bass. Of course very few box loudspeakers can play bass fundamentals properly either so it isn't like there will be no bass compared to a typical box loudspeaker. Proper bass fundamentals are scary, you know when they are present.

[Paul Hynes]

I have been preparing content for a technical resource that I intend to include in a new website later this year and the following OB loudspeaker project I am including in the resource may be of interest on this thread. This is a work in progress so if anything does not make sense, please speak up so I can edit the text to ensure it does make sense.

How do you build your ideal loudspeaker? I faced this issue before moving out to the Isle of South Uist ten years ago. Of course, one mans ideal may not suit others but the information presented here may help others experimenting with loudspeaker design and build. I have built my own loudspeakers since playing in an impoverished rock/pop band in the late 1960s demanded adoption of low cost solutions for amplification and speakers.

This practice continued when I developed an interest in HiFi equipment for home use. I have tried all the drive unit loading methods through the years, and they all have their own compromises, but one method had stuck in my mind and this was the open backed line array we used for the PA in the band. It was efficient, dynamic and had low susceptibility to acoustic feedback from microphones and instruments.

American rock band The Greatful Dead took this concept to the extreme with each member of the band using individual line arrays in their stage rig. The also had a reputation for stunning sound quality when using these line arrays. Unfortunately the stage rig proved too costly to maintain on the road and it was eventually broken up.

Some of the problems with Open Baffle loudspeakers discussed in this thread can be alleviated, by adopting the line source array configuration for the loudspeakers. I had been experimenting with open baffle line source arrays for a number of years prior to the Uist move and had decided to build some line arrays with as little compromise as possible within my available budget at the time. I drew up a hit list of issues I wanted to address

1) Move enough air to give a convincing illusion of a large scale musical event. For a loudspeaker to create a convincing domestic illusion of a full scale concert orchestra playing large scale works effortlessly, or a rock band letting rip, requires the ability to move a lot of air. Horn loaded speakers can do this but they require a large horn mouth area for extended low frequency response and would be quite over powering physically in the new house lounge in Uist.

A single bass drive unit typically used in domestic OB projects is not going to do this. Those damn laws of physics again! I required a relatively small footprint for the loudspeakers. A vertical line array can do the small footprint and with enough drive units can move lots of air.

2) Minimise phase anomalies through the audio frequency range. This is something I am particularly sensitive to. I have worked with both passive and active crossover designs over the years and generally concluded that the Kiss principal pays dividends where phase response is concerned. In fact I wanted to lose crossover artefacts altogether, so no crossovers. This demands the use of full range drive units and decent ones with wide bandwidth can get quite expensive.

I did not want to buy 16 drive units without some clue about their sonic performance so I looked for suitable contenders and purchased a few that were within budget for trials on a standardised single drive unit OB baffle to compare performance. After suitable run in periods, which are absolutely necessary to allow drive unit performance to stabilise, I liked the overall coherence of the Visaton B200, so I based the line array OB on this drive unit.

I could accept the trade off of falling HF above 12 KHz in exchange for no phase anomalies that would occur with the addition of tweeter lines into project. There are now more options for OB drive units so some may provide better performance than the B200, but cost may well be an issue with some options I have seen.

3) High efficiency. A nice side effect of using multiple drive units in a line array is that the mutual coupling between adjacent drive units boosts efficiency by 3dB when you double the number of drive units. The B200 nominal efficiency in the mid band is typically 96dB for 1W @ 1 metre so eight in parallel take this up to 105 dB for 1W. Also a point source loudspeaker of the type typically used domestically would propagate a spherical wave front into the room with a SPL (sound pressure level) loss of 6dB with each doubling of distance from the source.

A line source however, propagates a cylindrical wave front into the room with a loss of only 3dB with each doubling of distance from source over typical seating distance from the arrays. This means that the line source SPL falls off less rapidly with distance, effectively boosting efficiency, which in my case, with a listening position approx four metres from the speakers, amounts to a further 6dB of efficiency gain over a point source loudspeaker.

4) Reasonable bass response without resorting to compensation. An additional benefit of the line source array on an open baffle is related to the cylindrical waveform propagation from the line. With more energy moving forward rather than to the sides, as would be the case with a typical single drive unit OB, there is less cancellation at low frequencies when the front and rear waves from the drive units meet at the edge of the line baffle.

This, and the mutual drive unit coupling, provides extended bass response from the line when compared to a single drive unit. With no drive unit enclosure resonances to muddle the bass waveforms, bass is very natural and expressive and the baffle is only 400mm wide.

5) Reduced room interaction. A point source loudspeaker propagates a spherical wave front into the room and as this spreads out there are room reflections from wall floor and ceiling. As these reflections mingle with the direct music wave front it causes cancellations at some frequencies and reinforcements at other frequencies. I wanted to avoid the requirement for room correction as it violates the Kiss principal.

Fortunately the cylindrical wave front propagated by the line array does not reflect off the ceiling or the floor so room interaction is considerably reduced. Wall treatments on left and right can reduce reflections from this source and rear reflections can also be treated with similar techniques.

6) Large low distortion dynamic range. With an overall efficiency approaching 110 dB for 1W very little power is required for concert hall levels. I use a pure class A current amplifier rated at around three Watts to drive each line. Each line is rated at 560 Watts so there is never going to be an overload situation and the actual drive unit travel with 3 Watts is still within the drive unit low distortion range. Large low distortion dynamic swings are possible with these arrays and they can be quite startling at times with suitable program and especially with some of the blockbuster movies around nowadays.

7) Avoid driving drive units via other series wired drive units as this causes distortion due to reactive effects between the drive units. Ideally, all of the eight drive units in each line should behave as one drive unit and this can be accomplished by wiring all the drive units in parallel using a symmetrical wiring arrangement.

Unfortunately, this creates a nominal load impedance of 0.75 Ohms, which will freak out most amplifiers. So I designed a low distortion current amplifier for low impedance loads to drive the arrays. A nice side benefit of this is that no voltage gain is required in the amplifier to deliver a few watts into 0.75 Ohms from normal line level signals. Less circuitry in the signal path to generate distortion!

[struth]

i take it they are wired series parallel ?

cancel that lol :doh: missed the bit at bottom

[Macca]

Hi Paul. hope you don't mind but I have edited your post to put in some breaks and paragraphs, makes it a lot easier to read since it is well worth reading. I think I recall you talking about your line arrays a few years back. I looked for more info on the web at the time and there wasn't much. What would you estimate the build cost at? (Excluding the amp.)

[Arkless Electronics]

"Those damn laws of physics again!" Don't worry Paul.. I'm "reliably" informed that they don't apply to audiophoolze... :D

Tim de Paravicini has/had some home made speakers in his listening room at home which I was pretty impressed with and which used a line source array of many (maybe 30 per side) small drivers which looked like nothing less than the things one found in small ghetto blasters etc! 3" or so paper cones with ally/silver plastic dust cover dome in middle... there were separate woofers IIRC.

[paulf-2007]

True but that all depends on the size of the baffle, and whether it has sides to it or not. Most OBs don't seem to have baffles much wider than the drive units so you are going to get pretty much full cancellation in the bass. Of course very few box loudspeakers can play bass fundamentals properly either so it isn't like there will be no bass compared to a typical box loudspeaker. Proper bass fundamentals are scary, you know when they are present.before I added sides to my baffles mine also only had 2" each side of the driver and 3" to the floor, I had excellent bass down to 50hz, so your statement of full cancellation is incorrect sir.

[walpurgis]

Never seen Martin addressed as "sir" before! ;)

[Paul Hynes]

Hi Martin,

No problem with the editing. I am still considering if additional information would be useful, and whether to provide the original drawings, if anyone wants to experiment. So the layout is yet to be finalised.

Sixteen B200s, custom machined baffles, aluminium extrusion frames, stands, wire and connectors cost me around £3000 in materials ten years ago. No labour factored in as I was doing this for myself. Expect 50% higher now. I have not felt the need to change these arrays for 10 years other than to consider what better full range drive units would bring to the table.

Hi Jez,

Yep, the world is full of speaker designs trying to get a quart out of a pint pot.

I experimented with smaller Visaton paper coned full range drivers with reasonably high Qts and these were quite good but not in the same class as the B200, and they definitely required sub woofers to fill out the low frequency end whereas the B200 array does not require a subwoofer.

[RothwellAudio]

Yeah the big problem is that woofers for OB need pretty specific characteristics...
It might be helpful and/or interesting to spell out what these requirements are so potential builders can look for suitable drivers in their chosen price range. It looks like the prices can go pretty stratospheric!