In case you wanna give it a try yourself :
http://www.diyaudio.com/forums/multi-way/110583-fast-fun-inexpensive-ob-project-3.html#post1996185
Michael
8' no baffle pics
This was a bit disappointing.
In free air the driver just " was not there" sonically, i.e. massive gap in the frequency band.
In a small trapezoid baffle a single 8' Seas Excel was really good over the 60Hz to 400Hz band.
Next comes the 15' Precision Devices....!
Cheers
Derek.
This was a bit disappointing.
In free air the driver just " was not there" sonically, i.e. massive gap in the frequency band.
In a small trapezoid baffle a single 8' Seas Excel was really good over the 60Hz to 400Hz band.
Next comes the 15' Precision Devices....!
Cheers
Derek.
A bit back on topic.... the 21" woofers I use in H-baffles are capable of low distortion response to 30 Hz. I just wonder how much bigger they must be to go even lower.... say 25 Hz?
Anyway, I would like two of them per side! They produce the best bass I have ever heard, but I want MORE and LOWER.
Anyway, I would like two of them per side! They produce the best bass I have ever heard, but I want MORE and LOWER.
Precision Devices...
This is more like it.
Good down to 140Hz with no Eq.
Good to 100Hz with 6dB to 8dB Eq.
Now I know the driver to use.
Next step is to design a VPL baffle for it.
Will combine it with a 15' or 18' bass driver.
Stig Erik, I have some interesting results from soft mounting Vs rope suspension. Do you want me to post them here or start a new thread, I gather from your " A bit back on topic..."
you are focusing on the low bass from now on.
Cheers
Derek.
This is more like it.
Good down to 140Hz with no Eq.
Good to 100Hz with 6dB to 8dB Eq.
Now I know the driver to use.
Next step is to design a VPL baffle for it.
Will combine it with a 15' or 18' bass driver.
Stig Erik, I have some interesting results from soft mounting Vs rope suspension. Do you want me to post them here or start a new thread, I gather from your " A bit back on topic..."
you are focusing on the low bass from now on.
Cheers
Derek.
Regarding the mounting (suspension) of the drivers and the whole baffle, I'd like to share my observation.
My center OB sub was standing on the floor by thin felt pads (normally seen under various furnitures for preventing scratches...), about 2~3mm in thickness and slightly compressible. Shaked on top by hands, the whole baffle rocks back & forth slightly to a degree I could see and feel but not easy to measure... When playing hard with visible excursions on the cones, the vibration of the whole baffle was easily felt (but can't be seen).
We had discussed the suspensions of the drivers and baffle-less concept. I thought to myself, before I cut bigger holes on the baffle or throw them all away, why not give something else a try? -- something not so 'violent'.
So I tried some very soft supports under the baffle, which are stripe-type pads made of dense close-cell foam. Squeezing them by fingers, I feel they are very much softer than ordinary shoe pads. They are about 1cm in thickness before compression, and about 2~3mm thinner under the baffle. And then the whole baffle is very softly sprung. Shaking the baffle on top makes it rock back and forth by several mm to 1cm without displacement of its original postion. Now, at this fore-rear direction, it's like a freely rocking arm of a metronome. (OK, maybe not that 'freely'.... )
Feeding it with some sound effects of DVD movies, the cones start to move quite a lot while the baffle is largely calmed. The difference is very very much. The baffle is not dead still, though. There're still some sensible slight vibrations, but much much less than that of the previous, harder feet. By my own subjective sense and rough estimation, I'd say the residual vibration is only 1/5 or less.
Maybe not so ideal as a fully suspended 'swing', nevertheless, the soft feet indeed work quite well. (Not a very good analogy, but this makes me think of a soft fishing pole and the fish on the hook.... )
Sound quality-wise, sorry I can't tell much. I think it's mainly because this baffle is standalone and only working at the bottom octave. So I must say it just brings peace to my mind. I'd guess a wider range baffle could have more benefit and it's so easy to implement. By the positioning relation of the the vibrating sources and the supports, I think this soft support method can work much better on those baffles with drivers mounted higher up.
When there are so many dilemmas in designing and making all these, I'd suggest the soft feet are a very good compromise to take.
I'd foresee there must be a problem in these foam pads, though. They are quite easy to compress so I'd guess the life span wouldn't be long. Sooner or later they will be compressed to a degree and no longer provide enough compliance. So, maybe some air cushions would be better...
My center OB sub was standing on the floor by thin felt pads (normally seen under various furnitures for preventing scratches...), about 2~3mm in thickness and slightly compressible. Shaked on top by hands, the whole baffle rocks back & forth slightly to a degree I could see and feel but not easy to measure... When playing hard with visible excursions on the cones, the vibration of the whole baffle was easily felt (but can't be seen).
We had discussed the suspensions of the drivers and baffle-less concept. I thought to myself, before I cut bigger holes on the baffle or throw them all away, why not give something else a try? -- something not so 'violent'.
So I tried some very soft supports under the baffle, which are stripe-type pads made of dense close-cell foam. Squeezing them by fingers, I feel they are very much softer than ordinary shoe pads. They are about 1cm in thickness before compression, and about 2~3mm thinner under the baffle. And then the whole baffle is very softly sprung. Shaking the baffle on top makes it rock back and forth by several mm to 1cm without displacement of its original postion. Now, at this fore-rear direction, it's like a freely rocking arm of a metronome. (OK, maybe not that 'freely'.... )
Feeding it with some sound effects of DVD movies, the cones start to move quite a lot while the baffle is largely calmed. The difference is very very much. The baffle is not dead still, though. There're still some sensible slight vibrations, but much much less than that of the previous, harder feet. By my own subjective sense and rough estimation, I'd say the residual vibration is only 1/5 or less.
Maybe not so ideal as a fully suspended 'swing', nevertheless, the soft feet indeed work quite well. (Not a very good analogy, but this makes me think of a soft fishing pole and the fish on the hook.... )
Sound quality-wise, sorry I can't tell much. I think it's mainly because this baffle is standalone and only working at the bottom octave. So I must say it just brings peace to my mind. I'd guess a wider range baffle could have more benefit and it's so easy to implement. By the positioning relation of the the vibrating sources and the supports, I think this soft support method can work much better on those baffles with drivers mounted higher up.
When there are so many dilemmas in designing and making all these, I'd suggest the soft feet are a very good compromise to take.
I'd foresee there must be a problem in these foam pads, though. They are quite easy to compress so I'd guess the life span wouldn't be long. Sooner or later they will be compressed to a degree and no longer provide enough compliance. So, maybe some air cushions would be better...
It seems to me these projects are going the wrong way on the supposition that it is impossible to keep a speaker from vibrating in a baffle. Use a T shaped baffle with the rear leg cut out to fit the speaker magnets in addition to the front baffle. This will reduce speaker movement as much as needed. The front baffle could be triangular as in the original implementation with another triangular panel perpendicular to the center of the baffle. Perhaps it needs to be 700 mm long at the bottom. That should hold any woofer.
Ted
Ted
I tried bubble-wrap under one of my midrange/tweeter baffles.. it worked very vell, but it lasted for only a couple of days before the air was lost from the bubbles. I also tried some very soft rubber pads, they just collapsed.
There are soft suspension pads sold in hifi stores, most of them Sorbothan or similar material. Although quite expensive, those pads dont collapse over time. I think its worth a try.
When it comes to my 21" H-baffles, I'm going to try two things - stiffening the baffle with a matrix structure, and suspending it from the floor on soft pads. Even though the baffle vibrates quite a lot, it sounds very good - there is no sign of typical "box sound" or resonance.
There are soft suspension pads sold in hifi stores, most of them Sorbothan or similar material. Although quite expensive, those pads dont collapse over time. I think its worth a try.
When it comes to my 21" H-baffles, I'm going to try two things - stiffening the baffle with a matrix structure, and suspending it from the floor on soft pads. Even though the baffle vibrates quite a lot, it sounds very good - there is no sign of typical "box sound" or resonance.
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I found some air shock absorbers on the web, maybe for industrial usage. The smallest one I found is about 6cm high, still a little too big for me. They look very attractive, though, equipped with nozzle for pressure adjustment - inflation or leak.
Besides, I'm thinking of those air cushion pads used in shoes (yes, you all know that shoe marked as this magic word), should be ideal for this. 4 pads should be capable of supporting the weight of 2 adults. That's more than enough for me. I think this would be some kind of 'reinforced version' of bubble-wrap
I'll keep away from those cute-looking things in hi-fi stores.
Besides, I'm thinking of those air cushion pads used in shoes (yes, you all know that shoe marked as this magic word
), should be ideal for this. 4 pads should be capable of supporting the weight of 2 adults. That's more than enough for me. I think this would be some kind of 'reinforced version' of bubble-wrap I'll keep away from those cute-looking things in hi-fi stores.
There are actually two things that came together with my suggestion of swings.
I'm really interested if you may hear any difference with your H sub as well.
First I was after to "let the speaker move". (impulse compensation)
Second I was after to let the speaker move "freely"
What I meant with that is the issue of friction - that can be summed up to be an unpredictable leakage path of energy.
So - if you use any soft materials like foam pads or rubber balls or the like – there will be an unpredictable energy transformation into heat. Its basically like a break working unpredictable.
There was an interesting interview with a turntable manufacturer quite a while back – where he claimed that they have given a try to any (of the maaaaaaaaany) modifications suggested for their sub chassis turntables.
In the end they definitely dropped *all* of this modifications – and guess what – these mod's where almost entirely about dampening this or dampening that....
If you don't want to make a small swing (just the height of your H-sub) you could try to get
strong springs – like used for car valves for example and let your H-sub rest on three or four of them.
Steel springs have veeeery little inner friction and I guess you will end up at good = pretty low resonant frequency with such an assembly. You should come somewhere at least a decade below audio band - say 1 Hz or less
So I'm looking forward to your findings with soft balls etc...
Michael
I'm really interested if you may hear any difference with your H sub as well.
First I was after to "let the speaker move". (impulse compensation)
Second I was after to let the speaker move "freely"
What I meant with that is the issue of friction - that can be summed up to be an unpredictable leakage path of energy.
So - if you use any soft materials like foam pads or rubber balls or the like – there will be an unpredictable energy transformation into heat. Its basically like a break working unpredictable.
There was an interesting interview with a turntable manufacturer quite a while back – where he claimed that they have given a try to any (of the maaaaaaaaany) modifications suggested for their sub chassis turntables.
In the end they definitely dropped *all* of this modifications – and guess what – these mod's where almost entirely about dampening this or dampening that....
If you don't want to make a small swing (just the height of your H-sub) you could try to get
strong springs – like used for car valves for example and let your H-sub rest on three or four of them.
Steel springs have veeeery little inner friction and I guess you will end up at good = pretty low resonant frequency with such an assembly. You should come somewhere at least a decade below audio band - say 1 Hz or less
So I'm looking forward to your findings with soft balls etc...
Michael
You might want to try a heavy F3 1 inch thick felt sheet, like this one from McMaster-Carr
F3 Felt Sheet
This is what Siegfried recommends for the Orion's
-- Charles
Tonight I made some soft pads just to try it. The are made from 8 layers of foam gasket sheets. The pads became faily soft, I would guess the resonance frequency is below 2 Hz.
Big surprise - with the soft pads, the vibrations in the H-frame is much lower, just like CLS experienced with his baffles.
Big surprise - with the soft pads, the vibrations in the H-frame is much lower, just like CLS experienced with his baffles.
Did you hear any difference?
Last night I put some other foam pads under my main baffles. The woofers on main channels are mounted very low, and there're something quite heavy on top of the baffle (mid-high horns and drivers), so I made the supports even softer to get higher compliance.
It worked, again
But the effect on decrease of vibration was not so obvious as that of the sub. Maybe because the construction iteself is inherently stronger than the sub, and the vibration of original status was quite small already. It's like the vibrations on sub was changed from 5 to 1, and 2 to 1 on the main channels. Oh well, this is just very rough subjective impression, and I can not measure them objectively.However, I heard some minor difference this time
Maybe because the woofers on main channels cover larger range into the midbass. The bass notes are slightly clearer. The attack and decay of bass notes in those inferior recordings are now easier to distinguish. And there're slightly more details in those good recordings which are so enjoyable.Very intereting.
I think such thing works quite well on OB because of the simple construction and lacks of cavity resonances in nature, so the energy transfering paths are not that complex and it's easier to obtain positive results from these soft 'suspensions'.
BTW, my mid-high horns have already been isolated from the bass by steel wires suspension. The soft pads under the foundation doesn't affect them. So I think it's OK to say my listening impression was purely on the improvement of bass.
I did hear a difference. Even though the H-baffles work only in the 25-70 Hz range, I feel that the upper bass got cleaner. This might be because higher order resonance in the baffles are damped. I really dont know. My baffles are rather flimsy, made from just 19 mm MDF, and they still vibrate somewhat. But - to my ears they sound like the bass you get from headphones - very clean and well defined, no coloration.
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