Help needed! Where to start with open baffle speakers

[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.
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.