View Full Version : A speaker project
This will be a brief account of a mini project I embarked on in earnest last week but one that has had a gestation period spanning decades ...
In the early 80s I bought a pair of B&W DM-10 brand spanking new from a dealer in Amsterdam after auditioning a bunch of stuff (most beyond my means) The very young chap who assisted me was very patient but really wanted to sell me a pair of JAMO speakers that were apparently 'what everyone was buying' - he thought they were brilliant - I thought they were bloated crap and went for the B&Ws partly to irritate him, but actually because they were the only pair I could actually afford that I liked the sound of.
Fast forward to the early noughties and the DM-10 that had been my staunch sound buddies were relegated to the loft. Pressure of work and parenthood meant I had little time to listen to music and what listening I did do was computer based and through a pair of diddy bookshelf thingies or headphones. My Quad 33/303 were showing serious signs of age and also one tweeter in the DM-10s was playing up and I had no time or inclination to fix all the problems. Initially the speakers went to the loft but pressure on space a couple of years later meant they moved to garage storage where they pretty much stayed until I retired 5 years ago. One of the first things I resolved to do with my new found freedom was resuscitate my ailing HiFi set ... and this would include finally redeeming the DM-10 and fixing them up for service.
Unfortunately time (and the weather) had not been kind on them .....
To cut a long story short - one of the speaker cabinets had fallen victim of water ingress from a dodgy gutter connection (now fixed). Although not immediately apparent, when I took them out to have a better look the damage was obvious. The DM-10 were bottom of B&W's range when they came out and the cabinets were the typical cheap 'folded box' type made of laminated chip board which unfortunately does not take well to contact with water (basically the chip board swells up). At that point I pretty much gave up interest in them - obviously this would be a bit more than simply sourcing a replacement tweeter. They stayed in the garage and for a while I used them lashed up as they were with a Teac integrated. A year or so back, I removed the drivers, cut down both cabinets to remove the damaged section and put back the bass/mid drivers only; the working tweeter was passed on to an AoS member who needed one.
For a while I did consider putting the remaining two drivers on ebay - they sell for surprising money (about £40 each) which is a bit daft considering a complete pair of DM-10s don't fetch that :scratch:
https://farm1.staticflickr.com/923/43046985081_04f5eaa666_z.jpg (https://flic.kr/p/28zV3VX)B&W DM-10 (https://flic.kr/p/28zV3VX) by miktec101 (https://www.flickr.com/photos/138540546@N04/), on Flickr
However - I started to get other ideas ...
OK - I should stress at this point that this project was no more than simply having a bit of fun and maybe learning a little along the way (without getting a headache from thinking too much)
My knowledge of all things speaker related is basic (to say the least) and my woodworking skills haven’t progressed much since failing to make a working mortice and tenon joint at school but as I said, if it looks like fun, I’ll give it a go. I also didn't want to spend any money .... at all.
First thing I did was to remove the driver and terminal plate and strip out the remnants of the crossover. I then took a jigsaw to the cabinets and reduced them to baffle and bottom plate. I re-mounted the drivers and created a primitive ‘open-baffle’ set up. =
https://farm1.staticflickr.com/841/43046991151_8f3c970770_z.jpg
Plugging into the garage system and playing a few tunes I have to say they actually sounded quite good - very bright, open and detailed with a great sound stage but (predictably?) totally devoid of bass.
Back to the drawing board ....
I spent a few happy hours looking into different types of speaker enclosures and their pros and cons and looked at a few project sites involving single 8 inch drivers (albeit full range rather than my limited example)
For a while I toyed with the idea of building horn cabinets - as off of the frugal type or similar - but the sheer enormity of it and the expense of the wood required killed that idea stone dead - hardly worth it in this particular case (I also couldn’t be bothered…).
Checking what bits and bobs and leftovers I had in the garage, I opted instead for a small enclosed cube. I had just about enough old shelving and crap for a roughly 30 x 30 x 30 cm effort entirely constructed from scrap 18mm ply. It would look something like this I hoped:
https://farm1.staticflickr.com/925/28202179927_9190e21ae5_z.jpg
According to B&W’s blurb about the Bass/Mid driver (officially a DW200/10) it was specifically designed to function in a ported enclosure - but what the hell, nothing ventured, etc, etc. :lol:
I also figured that if it sounded utterly shit I could try it with a port ..... (although usually that's Xmas only)
walpurgis
28-06-2018, 16:45
Cubic enclosures tend to have resonance problems and can display unfortunate colourations. You might be able to pick up a pair of empty speaker cabinets from ebay for a modest outlay that could be more suitable for adaptation.
ianlenco
28-06-2018, 17:04
I've got a pair of KEF Q15.2 speakers - dual concentric so only one opening in the baffle + port. I bought them for a project but they didn't suit so they are lying around doing nothing. The rubbers on the main drivers are distorted so they were cheapish. For you they can be very cheap - the cost of picking them up! Probably a long way for you but you're welcome to them if they suit your needs.
If a driver is specifically designed for a ported enclosure is there not a risk of damaging it in an infinite baffle? Or is it the other way around? I can never remember.
What are you going to do for tweeters? I've some Audax metal domes and some Motorola piezo-electric horn tweeters lying about, you can have them for the postage if it helps. (The Motorolas are better than you'd think and they don't need a protective capacitor either. You can't blow them).
Cubic enclosures tend to have resonance problems and can display unfortunate colourations.
Not doubting that for a minute Geoff - but nothing like finding out first hand ;)
You might be able to pick up a pair of empty speaker cabinets from ebay for a modest outlay that could be more suitable for adaptation.
That would defeat the 'no budget' clause ... and also rob me of a whole load of fun.
My last fun project was building a small set of drawers from scratch to store hard drives and such - I already have loads of drawer space (including 8 sets of 'mini-drawers')
Basically, I get bored just drinking coffee and picking my nose all day :lol:
I've got a pair of KEF Q15.2 speakers - dual concentric so only one opening in the baffle + port. I bought them for a project but they didn't suit so they are lying around doing nothing. The rubbers on the main drivers are distorted so they were cheapish. For you they can be very cheap - the cost of picking them up! Probably a long way for you but you're welcome to them if they suit your needs.
Thanks for the kind offer Ian - but this is just a fun project with what's at hand. If they work to my satisfaction they'll stay in the shed anyway :)
If a driver is specifically designed for a ported enclosure is there not a risk of damaging it in an infinite baffle? Or is it the other way around? I can never remember.
I thought an infinite baffle was basically an open baffle in a room rather than an enclosed one - now I'm confused :scratch:
I thought an infinite baffle was basically an open baffle in a room rather than an enclosed one - now I'm confused :scratch:
Infinite baffle - driver rear wave completely contained, sealed cab.
Open baffle - no rear wave containment - no cab at all.
walpurgis
28-06-2018, 17:31
I thought an infinite baffle was basically an open baffle in a room rather than an enclosed one - now I'm confused :scratch:
'Infinite baffle' is a general and not necessarily accurate term for a sealed box speaker. No open baffle in a room would be infinite. The nearest you could achieve would be mounting speakers in holes in the wall that are open to the outside environment (yes, it has been done).
Martin had a point earlier. Drive units designed for ported cabinets tend to have more powerful magnets than those for sealed boxes. Using them in a sealed box would likely produce an 'overdamped system', resulting in lost bass extension.
Infinite baffle - driver rear wave completely contained, sealed cab.
Open baffle - no rear wave containment - no cab at all.
Thanks for the explanation Martin, all the internet reading just confused me (information over load)
- see, I'm learning already ;)
'The nearest you could achieve would be mounting speakers in holes in the wall that are open to the outside environment (yes, it has been done).
Crazy - what did they do when it rained?
walpurgis
28-06-2018, 17:51
Crazy - what did they do when it rained?
Surely you've heard of 'speaker brollies'? ;)
Paull Messenger the hi-fi bloke, he had some 15'' Tannoy DC mounted in the walls of his house, but they vented into the adjoining room instead of to outside. Still do the job, though.
Using them in a sealed box would likely produce an 'overdamped system', resulting in lost bass extension.
By 'lost bass extension' I presume you mean a lack of bass?
Curious in that when they were mounted in effectively an open baffle - bass disappeared completely
(noting that the DM-10 never had much of a bass presence in their original form to start with)
Back to the project for a moment.
The first step in constructing my cubes inevitably involved a cock-up. I set too jigsawing the openings in what would become the baffles but unfortunately somehow managed to fuck up the measurements and got the radius wrong (always double check .. and then check again :doh: )
As a consequence my stock of scrap 18mm was diminished ... so back to the graph paper to revise sizes. The cube would now have an external 27 x 27 x 27 provided I made baffles from a piece of 15mm laminated chipboard instead:
https://farm1.staticflickr.com/915/29200864768_365c58c6a4_z.jpg
By 'lost bass extension' I presume you mean a lack of bass?
Curious in that when they were mounted in effectively an open baffle - bass disappeared completely
(noting that the DM-10 ever had much of a bass presence in their original form to start with)
The reason you have a cab is to imprison the rear wave, otherwise it comes out and you get cancellation between rear wave and front wave. The lower the frequency the more cancelation you get. That is the sole drawback of the open baffle principle. But it is quite a big one. There are work-arounds though.
If you put the B&W drivers in the centre of open baffles say 4 feet square you will get some bass out of them. The bigger you make the baffle the lower the bass will go.
walpurgis
28-06-2018, 18:27
By 'lost bass extension' I presume you mean a lack of bass?
Curious in that when they were mounted in effectively an open baffle - bass disappeared completely
(noting that the DM-10 ever had much of a bass presence in their original form to start with)
Yes. Bass will be compromised and deep bass missing altogether.
Open baffles are funny things. All suffer cancellation due to sound from the back of the cone meeting that from the front. This can be accounted for with equalisation to an extent, at the cost of sensitivity. But strangely some open baffles seem to work reasonably well without it.
Glueing it all together, after some shenanigans with a circular saw on the back lawn.
Dowel pegs for the ply joints and clamps for the rest:
https://farm2.staticflickr.com/1810/42354827654_e96e6a488c_z.jpg
https://farm2.staticflickr.com/1824/43024095962_f2cc091df1_z.jpg
That looks like you know what you are doing. You don't fancy knocking me up some Tannoy cabs do you?
The interior seams were sealed with silicon and the T nuts retrieved from the old cabs.
Despite the need to allow the silicon plenty of time to cure, curiosity got the better of me and had to give them a quick blast:
https://farm2.staticflickr.com/1764/43024198462_e04b04d499_c.jpg
The only material I had to hand was MP3 from an old iPhone connected to my Quad 303 but I have to say that the result was actually pretty impressive; bass was more than sufficient on a track like 'Protection' from Massive Attack or Portishead's 'It Could be Sweet'. More impressive was the very open nature of the sound which was infinitely better than when they were in the stock cabinets, limited by the crossover filters.
This was yesterday and today I have been letting the boxes breathe while I rustle up some grilles. If I get time tomorrow I'll put them back together and take my RPi out to the garage for some more serious listening
That looks like you know what you are doing. You don't fancy knocking me up some Tannoy cabs do you?
Cheers for that ... as to the Tannoy cabs, everything's possible at a price but I tend to fuck up more than I get right so I wouldn't recommend it :lol:
walpurgis
28-06-2018, 19:58
Not sure how those drivers might fare employed as full range units. Could work OK.
You've reminded me actually. I must set up my table saw for my own (next) speaker project.
Cheers for that ... as to the Tannoy cabs, everything's possible at a price but I tend to fuck up more than I get right so I wouldn't recommend it :lol:
The cab in the picture above suggests otherwise to me. :D
Not sure how those drivers might fare employed as full range units. Could work OK.
Cheers Geoff - my main concern is whether they pose a threat to the Quad in terms of load (I am a numpty in case you hadn't guessed) If the drivers eventually pack in it will be a slight sadness but not something I would lose sleep over. The lack of a tweeter doesn't bother me that much given that I always found the stock DM-10 a little too bright and also in the meantime my age has pretty much put paid to my ability to actually hear upper frequency ranges - if they were there I wouldn't notice .....
I want to experiment a bit with stuffing the boxes - at the moment I have just recycled the foam from the originals so any suggestions will be most welcome. I might also see what effect introducing a port has, I have saved the old port tubes but not sure how effective/appropriate they would be given the significant reduction in volume.
The drivers will be breaking up after 3khz and won't do much after about 5Khz so unless your hearing is really bad you'll be missing a fair bit.
walpurgis
28-06-2018, 20:14
You won't hurt the amp. They'll be an easy load for it.
If you put a port in, installing it in the base might be effective seeing as the boxes don't sit straight on the deck. Just put it towards the back so it doesn't foul the magnet.
As for wadding. Just experiment.
Is that cabinet open on the bottom?
No
[QUOTE=RothwellAudio]This page suggests that these drivers are optimised for ported enclosures, and of course the original DM10 enclosures were ported:
[QUOTE]
I know - I already cited the DM-10 promo blurb in post #4
= "According to B&W’s blurb about the Bass/Mid driver (officially a DW200/10) it was specifically designed to function in a ported enclosure - but what the hell, nothing ventured, etc, etc. "
Vented enclosures need to be carefully designed to avoid the port resonating at the wrong frequency and doing peculiar things to the bass. The easiest thing to do would be to use the same enclosure volume and port dimensions as the original cabinet.
No argument there (and already suggested earlier) - however, see initial posts in the thread about why this didn't happen - particularly post #3:
"OK - I should stress at this point that this project was no more than simply having a bit of fun and maybe learning a little along the way (without getting a headache from thinking too much)"
Sorting out some grilles with the only bit of 9mm MDF to hand (sorry Paul Klee - you had to go...)
https://farm1.staticflickr.com/920/29205812548_216d518354_z.jpg
Cladding them (oodles of scrim left over from my Quad 22L refit):
https://farm1.staticflickr.com/921/43041290892_abd653c7f9_z.jpg
A couple of bits of stick-on Velcro and 'up and away'
https://farm2.staticflickr.com/1789/43041296612_1c456b9959_z.jpg
Finally put them back together this afternoon and added some pillow stuffing (my wife magicked a Boyes' bag full from the spare room)
Into the shed and RPi plugged in for some AIFF renditions of popular tunes from the 90s (and even earlier). ..
How did they sound? ... well actually quite splendid, enough bass to satisfy my needs and a surprising amount of upper end definition. The sound was definitely an improvement on what I remember from years of listening to the DM-10s in their original form ... less woolly at the bottom end and with a fuller mid to high presence. As with the initial 'open baffle' experience the most noticeable improvement was a distinct sense of presence and space - a directness that really grabbed me.
As to to top-end roll off, I am not a great judge of that given that I get a pretty sharp fall off at about 8 - 8.5 kHz so I asked my wife to have a listen (her hearing range exceeds mine by a long chalk, being younger - and a woman). She couldn't detect anything miss with what she was hearing at all, listening to a range of tracks from Portishead and Massive Attack. Later I tried a few tracks from Art of Noise 'In Visible Silence' - the speakers handle stuff like 'Paranoimia' and 'Peter Gunn' with ease but also the more sensitive 'Camilla' was handled with aplomb.
Was it the last word in listening pleasure, audio nirvana and a giant killing solution? - of course not, and I never expected them to be. But for a total cost of £1.80 to replace two 2.8mm spade connectors that had rotted, I have a pair of worthy boxes that will enliven my summer days in the garage :)
https://farm1.staticflickr.com/915/28225993677_2857c2aaa0_c.jpg
Flickr (https://www.flickr.com/photos/138540546@N04/)
Bravo Mike! A good effort! And a great learning experience I’m sure. And, your project need not stop now. You could do some math, figure what length port they would need and drill a hole, and glue a paper towel roll into the hole. I’ve got books on the shelves around here somewhere with the equations for such things, from back before they made all the computer programs that calculate all this stuff for us. A properly installed port can give a bit of deeper bass, and less boxy or boominess to the sound.
Perhaps keep your eye out for some ratted out old car speakers? Coaxial, or triaxial types, with the tweeter suspended over the woofer. If the woofer is rotted out the tweeter may still be fine, as they are mostly plastic. And on car type speakers you’ll see a small capacitor glued right behind the plastic tweeter mount. You could simply wire it right in at the terminals and mount them right on the tops of your boxes. Instant two way speaker! B&W style, with the top mounted tweeter, enclosed in a shampoo bottle painted black or something.
Hind sight is 20/20, and you did a fine job. In the future you may want to observe the Golden Ratio on speaker dimensions. 3x6x9? Something like that, I’m sure a Google search would turn it up? And I really like your grills! And the stuffing, I was thinking some pillow fill, (polyfil), sells for $10 a bag at speaker parts stores, but you can buy the exact same stuff at the fabric shop for $2. Your wife was on the spot with that one!
I’m not sure why, but speakers you built yourself always sound a bit better than store bought, a little pride of ownership and sense of accomplishment could be causing a bias?
I’ve got notebooks full of fantastic speaker designs! All calculated to exacting tolerances with crossover designs, using expensive drivers, etc. etc.. but the difference between mine and yours, mine are still on paper and yours are up and running! Bravo!
And love the shop, looks like a place where things get done.
Russell
walpurgis
29-06-2018, 21:35
Perhaps keep your eye out for some ratted out old car speakers? Coaxial, or triaxial types, with the tweeter suspended over the woofer.
Yes. Car speakers can be extremely good, but seem to be looked down upon by the Hi-Fi fraternity (the usual 4 ohm load puts some off too).
Bravo Mike! A good effort! And a great learning experience I’m sure. And, your project need not stop now. You could do some math, figure what length port they would need and drill a hole, and glue a paper towel roll into the hole. I’ve got books on the shelves around here somewhere with the equations for such things, from back before they made all the computer programs that calculate all this stuff for us. A properly installed port can give a bit of deeper bass, and less boxy or boominess to the sound.
Thanks for the kind words Russell :)
To be honest I doubt I'll be doing much more of this - I like to keep active if only to give my finger joints some exercise (they get really creaky and crampy during the winter months..) but serious speaker design and construction doesn't quite rock my boat. I still can't quite get my head around the whole 'wave' business. If I hadn't had the speakers going begging I would probably have made a hat stand or something :lol:
I didn't get a lot of time to listen today because we had to be somewhere else but I was actually quite surprised they they didn't sound like complete shite given by what I had read beforehand and also what others have said earlier in this thread. I think they will be very music mode dependent - I did listen to a short piece of classical via BBC 3 on the RPi but they clearly aren't subtle enough for that, smooth jazz would also probably suffer (might try a little Coltrane though tomorrow if I get the chance)
As to adding a tweeter, if you look at the top of the bookshelves on the shed picture you might just make out a Harman Kardon SoundStick tweeter set; I picked up a pair from a junk shop a while back for £10 and I might lash them in at some point and see what they do ... but to be honest I don't really feel the need and also have some fairly urgent domestic paintwork to attend to ... (the balance is important)
The shop was a garage - only problem is it was built for very narrow cars. I had a mini for a while but if I drove it in there I could only just get out the car .... so now it just serves as a general dump for boxes in Winter and a place for me to tootle about in the Summer. Most of the time it looks like what we generally refer to in the UK as a 'shithole' :lol:
walpurgis
29-06-2018, 23:19
I still can't quite get my head around the whole 'wave' business
Talking of 'waves'. Now is the time to consider bunging those drivers in a quarter wave transmission line cabinet system with suitable tweeters etc.
Something like this:
http://i66.tinypic.com/2lzvc0.png
Those drivers are likely to be well suited and the bass response will blow your mind! :D
Talking of 'waves'. Now is the time to consider bunging those drivers in a quarter wave transmission line cabinet system with suitable tweeters etc.
Those drivers are likely to be well suited and the bass response will blow your mind! :D
No problem Geoff - you send me all the wood cut to size ... and I'll supply the glue :lol:
Thanks for the kind words Russell :)
To be honest I doubt I'll be doing much more of this - I like to keep active if only to give my finger joints some exercise (they get really creaky and crampy during the winter months..) but serious speaker design and construction doesn't quite rock my boat. I still can't quite get my head around the whole 'wave' business. If I hadn't had the speakers going begging I would probably have made a hat stand or something :lol:
I didn't get a lot of time to listen today because we had to be somewhere else but I was actually quite surprised they they didn't sound like complete shite given by what I had read beforehand and also what others have said earlier in this thread. I think they will be very music mode dependent - I did listen to a short piece of classical via BBC 3 on the RPi but they clearly aren't subtle enough for that, smooth jazz would also probably suffer (might try a little Coltrane though tomorrow if I get the chance)
As to adding a tweeter, if you look at the top of the bookshelves on the shed picture you might just make out a Harman Kardon SoundStick tweeter set; I picked up a pair from a junk shop a while back for £10 and I might lash them in at some point and see what they do ... but to be honest I don't really feel the need and also have some fairly urgent domestic paintwork to attend to ... (the balance is important)
The shop was a garage - only problem is it was built for very narrow cars. I had a mini for a while but if I drove it in there I could only just get out the car .... so now it just serves as a general dump for boxes in Winter and a place for me to tootle about in the Summer. Most of the time it looks like what we generally refer to in the UK as a 'shithole' :lol:
There’s certainly no hurry on jumping back on the speakers, as long as they make you happy. But, in a few months if you get curious attach those tweeters and perhaps it will handle a classical tune?
I too am one to work on projects as the urge arises, I’ve got two guitars that don’t belong to me waiting for work, I’ve had them several months, and I told the owner that he doesn’t want me to be straightening necks and leveling frets until I’m good and in the mood. So far he’s been patient.
Russell
Just to follow up on the latest ...
Having listened to them occasionally over the last couple of weeks and enjoyed what I heard, I decided that time was to pop in a port.
Following Geoff's suggestion earlier, I opted for a down firing one and did a quick scale sketch on graph paper to check for placement:
https://farm1.staticflickr.com/838/29461486668_c140f78087.jpg
... followed by some swift jiggerypokery with a jigsaw to fabricate a home for the original port tube:
https://farm2.staticflickr.com/1790/28462443487_d3f063175d_z.jpg
In the intervening time I have also done a complete re-arrange of the shed/garage so the speakers now have a spanking new (and very elegant) location:
https://farm2.staticflickr.com/1804/43365217971_0cb4cb90e1_c.jpg (https://flic.kr/p/29535tV)re-shedded (https://flic.kr/p/29535tV) by miktec101 (https://www.flickr.com/photos/138540546@N04/), on Flickr
Obviously, the port has opened up the bass a fair bit but also it added a bit more warmth to the mids - which is nice .... fortunately, opening the box hasn't done much damage to the overall sense of space and immediacy that I found initially such a buzz when I removed the crossover.
So all in all - very good stuff and a happy chappy. :LOL:
Note: the Harman Kardon thingummybobs aren't connected.
Nice work! I’ve been working on my speaker ideas, doing a bit of graph paper drawing myself. I must say you’ve inspired me. It may take me a month to get going on my project, but when I do I’ll create a post as you have to illustrate my work.
Impressive down firing port! Best way to go.
Russell
walpurgis
14-07-2018, 09:30
And I did spot the Mini instrument cluster to the right.
And I did spot the Mini instrument cluster to the right.
...thought you might ;)
- souvenir from a previous project:
https://farm2.staticflickr.com/1788/41597941560_484354c41b_c.jpg
Nice work! I’ve been working on my speaker ideas, doing a bit of graph paper drawing myself. I must say you’ve inspired me. It may take me a month to get going on my project, but when I do I’ll create a post as you have to illustrate my work.
Impressive down firing port! Best way to go.
Russell
Cheers Russell - quite chuffed if this has inspired you to get cracking on something :)
I’ve installed BassBox 6 on my computer! So my speaker project should be coming along soon! I’ll start a new post when I’ve got photos to share.
Russell
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