Hi, the usual wisdom for speaker cabinet building holds that the more one can eliminate cabinet resonance, the better. The theory is that the only thing than should resonate is the driver diaphragm/cone and everything else should be damped and as made rigid as possible.
Having recently done some reading on Bud Purvine's approach to cone treatment and some more reading on resonances at Mother Of Tone presents: The Altmann BYOB Site, I wonder if there are people in DIYAudio community who tried not to eliminate/reduce cabinet resonances but rather accepted them and tried to make the best use of this acoustic phenomenon.
Clearly, a speaker cabinet is different from a musical instrument which relies on resonances to achieve its characteristic sound, but there are still people who believe that using wood (e.g. birch plywood) makes speaker cabinet sound more "musical" than MDF or concrete or other artificial material...
In addition, there is the issue of lacquer/finish of wood which has impact on the sound.
Has anyone here done some off-the-mainstream experiements in this direction? What were your results?
Thank you for sharing...
Peter
P.S. I should mention that personally I prefer to listen with my ears than with measuring instruments. Therefore, I am not against "colored" sound if it is pleasing. Also, having wonderfully linear response curve in anechoic chamber (or other not real-life scenarios) is less relevant for me.
Having recently done some reading on Bud Purvine's approach to cone treatment and some more reading on resonances at Mother Of Tone presents: The Altmann BYOB Site, I wonder if there are people in DIYAudio community who tried not to eliminate/reduce cabinet resonances but rather accepted them and tried to make the best use of this acoustic phenomenon.
Clearly, a speaker cabinet is different from a musical instrument which relies on resonances to achieve its characteristic sound, but there are still people who believe that using wood (e.g. birch plywood) makes speaker cabinet sound more "musical" than MDF or concrete or other artificial material...
In addition, there is the issue of lacquer/finish of wood which has impact on the sound.
Has anyone here done some off-the-mainstream experiements in this direction? What were your results?
Thank you for sharing...
Peter
P.S. I should mention that personally I prefer to listen with my ears than with measuring instruments. Therefore, I am not against "colored" sound if it is pleasing. Also, having wonderfully linear response curve in anechoic chamber (or other not real-life scenarios) is less relevant for me.
Hi Chris,
the automatic suggestions of diyaudio when I started this topic were all related to *eliminating* resonances - I could not find anything similar to the topic of working with resonances. Your reaction would indicate you are able to direct me to some (perhaps controversial) threads on this topic... If so, that will be appreciated.
Peter
the automatic suggestions of diyaudio when I started this topic were all related to *eliminating* resonances - I could not find anything similar to the topic of working with resonances. Your reaction would indicate you are able to direct me to some (perhaps controversial) threads on this topic... If so, that will be appreciated.
Peter
Chris,
perhaps a sub-question closer to home to your views: some time ago I built a pair of Metronomes with enabled Fostex FE127eN drivers. I used 3/4" birch plywood.
All panels of plywood had a synthetic lacquer finish both inside and outside. What differences (if any) might be expected if a finish using natural resins would be applied (e.g. dammar lacquer or similar)? How about selective placement of enabl patterns on speaker panels?
Peter
perhaps a sub-question closer to home to your views: some time ago I built a pair of Metronomes with enabled Fostex FE127eN drivers. I used 3/4" birch plywood.
All panels of plywood had a synthetic lacquer finish both inside and outside. What differences (if any) might be expected if a finish using natural resins would be applied (e.g. dammar lacquer or similar)? How about selective placement of enabl patterns on speaker panels?
Peter
Run a search & you'll find dozens of the damn things all over the place, either in threads on other topics, or with dedicated threads.
Best discussion is here: http://www.diyaudio.com/forums/construction-tips/128681-wood-varnish.html
Eliminating cabinet resonance is a bit of a misnomer TBH, because you can't. Therefore, assuming that you wish your loudspeaker to reproduce what is on the recording and not add colourations of its own devising, it becomes a matter of controlling the panel resonance, i.e. pushing it to a region where there is less energy available to excite it, and it is thus more easily rendered inaudible. Effectively that means above or below the functional BW of the cabinet. Below is impractical for a bass enclosure since the lower the panel Fs the greater is its BW and amplitude. Typically it's easier to go for panels with a high stiffness to weight ratio which will lift their natural resonant BW above the box's operating zone, where there is very little energy available to excite them, and thus it is very easy to render it ~inaudible with a minimal amount of damping.
If we're talking about a box that is deliberately designed to resonante / designed like a musical instrument, we're into deep subjective territory. Since properly controlling such resonances is beyond the facilities of the average DIYer (and most speaker companies), the blunt fact is that any such resonances are thus a distortion / colouration of the original content. It might be euphonic distortion / colouration, but it's still distortion / colouration.
Best discussion is here: http://www.diyaudio.com/forums/construction-tips/128681-wood-varnish.html
Eliminating cabinet resonance is a bit of a misnomer TBH, because you can't. Therefore, assuming that you wish your loudspeaker to reproduce what is on the recording and not add colourations of its own devising, it becomes a matter of controlling the panel resonance, i.e. pushing it to a region where there is less energy available to excite it, and it is thus more easily rendered inaudible. Effectively that means above or below the functional BW of the cabinet. Below is impractical for a bass enclosure since the lower the panel Fs the greater is its BW and amplitude. Typically it's easier to go for panels with a high stiffness to weight ratio which will lift their natural resonant BW above the box's operating zone, where there is very little energy available to excite them, and thus it is very easy to render it ~inaudible with a minimal amount of damping.
If we're talking about a box that is deliberately designed to resonante / designed like a musical instrument, we're into deep subjective territory. Since properly controlling such resonances is beyond the facilities of the average DIYer (and most speaker companies), the blunt fact is that any such resonances are thus a distortion / colouration of the original content. It might be euphonic distortion / colouration, but it's still distortion / colouration.
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Thank you Scottmoose for your response. The discussion at the link you gave is very informative and very much what I was looking for.
Peter
Peter
If you buy into the laquer religion there are many faith healers around to pick from. From an engineering perspective there are several solutions/compromises. If the bassdriver is also the midrange driver you can have thin walls 9mm plywood and thick damping material like the Spendor BC1. The resonances are taken down from the very important midrange into the bass range were it does less harm. The price to pay is less definition in the bass range. In a 3 way system the bass can cabinet can be made very stiff to keep it above the used range. The german magazines Klang & Ton and Hobby &HiFi have done extensive measurements to measure the effect of different cabinet material, differerent braces and different laminations. There is also some on the net on this subject.
Apparently some people must hold some pretty strong opinions on this issue if it warrants the label of "laquer religion" 🙂 I never guessed simple curiousity could put someone at risk of being associated with this "religion"
Thank you for the reference to Klang & Ton and Hobby & Hifi.
It seems people are very particular where they direct their beliefs in the audio hobby - in measurements, crossover voodoo, cabinet varnish etc. etc. etc.
I love the sheer number of topics to be discovered as upgraditis develops 🙂
Thank you for the reference to Klang & Ton and Hobby & Hifi.
It seems people are very particular where they direct their beliefs in the audio hobby - in measurements, crossover voodoo, cabinet varnish etc. etc. etc.
I love the sheer number of topics to be discovered as upgraditis develops 🙂
My earlier eye-rolling was in anticipation of the thoughtful discussions and cheerful consensus that generally follow such an innocent query as in your OP 😉. In other words, "no, actually"
There are lots of folks with different reasons for sealing/finishing all exposed interior panel surfaces, whether overlaid with absorbent damping materials, mass loaded or constrained layers. As I've not experimented or auditioned any such, I can't comment other than "that'd be a lot of extra work".
Dammar varnish is part of Dave's treatment regime for certain Fostex drivers, but I've not personally experienced it for any other purpose. My use of lacquers is restricted to top coat on finishing of veneered speaker cabinets and furniture, and after trying a couple of water based and polyurethanes, have settled on sprayed catalyzed nitro-cellulose lacquer for ease of application and quality of finish.
Yes, I have heard what selective EnABL patterns can do on the front/side panels of speaker enclosure. At least when applied by Bud, they further assisted a Fostex FE127E/Fonken enclosure's "disappearing act". Quite a few others have reported the same experience with other designs.
Lacquer, varnish, or paint does not have nearly enough mass, stiffness, or damping effect to make any audible difference on something as heavy and stiff as a typical loudspeaker box. The only way I can think or that it might make a difference is by sealing out moisture. But that is a stretch.
I play saxophone. Many players believe the lacquer on a sax affects its sound. It does not. However, re-lacquered horns are suspect for good reason. The process requires buffing. Buffing enough to remove normal scratches can affect the sound. I know from experience. I told the @#$%^& guy not to buff the scratches out. A perfectly good vintage Selmer SBA tenor came back from the shop thin as an eggshell and ringing like a bell. I sort of got off track, didn't I?
I play saxophone. Many players believe the lacquer on a sax affects its sound. It does not. However, re-lacquered horns are suspect for good reason. The process requires buffing. Buffing enough to remove normal scratches can affect the sound. I know from experience. I told the @#$%^& guy not to buff the scratches out. A perfectly good vintage Selmer SBA tenor came back from the shop thin as an eggshell and ringing like a bell. I sort of got off track, didn't I?
I have found that the more effort i put into making the inevitable resonances inaudiable (ie higher in frequency, higher in Q) the more the box dissapears.
I too can see how a finish that crates even a very shallow stiffer layer on the surface of a panel could help achieve higher F, higher Q. Effect would be small and more likely (accidentily) pushing an audible resonace up just enuff to move the resonance out of the well-tempered scale. At this point i just brute force things.
dave
I too can see how a finish that crates even a very shallow stiffer layer on the surface of a panel could help achieve higher F, higher Q. Effect would be small and more likely (accidentily) pushing an audible resonace up just enuff to move the resonance out of the well-tempered scale. At this point i just brute force things.
dave
Yep- a mantra to live by. Very few experienced builders bother getting finnicky with the little stuff, recognizing that there are known big issues that need addressing in most any loudspeaker system.
I imagine practical considerations prevail when one builds dozens of speakers and knows what the big issues are (and cabinet finish is not one of them). But for a hobbyist with one or two pairs of speakers at home, I guess it is not surprising that also enclosure varnish gets some attention after room acoustics, cone treatment, capacitors, speaker cables, etc., have all been addressed already.
Thank you Dave for this info. In fact, I started looking into the varnish issue because the sounds "sticks" to the driver and BLH do not disappear enough... But I guess I am trying to achieve the impossible - find a cure for a lack of breathing space for the speakers... and it is not happening.
Thank you Dave for this info. In fact, I started looking into the varnish issue because the sounds "sticks" to the driver and BLH do not disappear enough... But I guess I am trying to achieve the impossible - find a cure for a lack of breathing space for the speakers... and it is not happening.
Yes you should try this.
I have been doing this with ports, vents, horn mouths, baffles, cabinet edges and internal cabinet walls for a number of years now. Using duct tape or self-adhesive vinyl or similar will address some of the issues you have with your BLH. Happy to help if you need it.
Cheers,
Alex
The SL600 loudspeaker by Celestion (UK) utilized a cabinet with Aerolam, an aluminum honeycomb construction. High frequency resonance and low mass for low energy storage, really oposite philosophy of Wilson Audio speakers that use a lot of mass to reduce vibration. Boxes of chipboard/MDF/plyood with braces and then lined with ceramic tiles and cheap floor carpet is really inert and way cheaper than oak plywood and the like
It's not a thread here, but I've owned Mordaunt Short loudspeakers which tuned their resonances to work with their drivers. Reading up on some TV21 Seas woofers I own, I came across some Troels Graverson comments regarding one of his designs for them, a thin walled unbraced one made to enhance their bass quality. It's not a new concept. Living Voice encourages cabinet resonances by using chip board in their speaker cabinet panels. Have a look around.
I'm finally satisfied with my satellites, and have started addressing my sub. My plate amp has a simple parametric equalizer , and I've found it benefits greatly with a narrow Q 6db cut at 60 Hz. It's a pretty even room for modes, according to large full range speakers I've had in the past, so I'm assuming it's limiting that frequency from exciting a panel resonance.
Wasn’t it the SL6000 that was aerolam and the SL600 was the same drivers in a more common cabinet?
anyway, I try to move the cabinet resonance up in frequency as far as possible where there is less acoustic energy to excite the resonance. That requires stiff, smaller pieces that resonate at higher frequencies as opposed to large heavy panels that resonate right where the most acoustic energy is. One way of doing that is to laminate panels with half inch Baltic ply with half inch of mdf that has been sliced into small irregularity shaped pieces that all fit together glued with a rigid glue to the ply. You end up with a one inch thick panel with multiple high resonances that are above the critical region that is prone to audible excitation. It’s a lot of work but if your looking for an inexpensive way to do it. Just one of many ways!
anyway, I try to move the cabinet resonance up in frequency as far as possible where there is less acoustic energy to excite the resonance. That requires stiff, smaller pieces that resonate at higher frequencies as opposed to large heavy panels that resonate right where the most acoustic energy is. One way of doing that is to laminate panels with half inch Baltic ply with half inch of mdf that has been sliced into small irregularity shaped pieces that all fit together glued with a rigid glue to the ply. You end up with a one inch thick panel with multiple high resonances that are above the critical region that is prone to audible excitation. It’s a lot of work but if your looking for an inexpensive way to do it. Just one of many ways!
Cabinet Resonances, I pretty much know what they do, and how they affect the overall sound of something.
My feelings are that only the speakers themselves should produce sound.
When I first got this lovely, virtually pristine 1960's console stereo, I naturally brought it back to working order, not that it had issues, but as a restorer I have extensive experience in vintage equipment.
The 106 year old lady that passed away three homes away from me owned it, and probably only dusted it over the decades, hardly used.
The side walls were walnut veneered 1/4 inch plywood, the front speaker baffle was 1/2 inch plywood, sporting 8 inch woofers and cone tweeters.... basic, mass produced stuff by RCA Victor.
The overall sound was sloppy-boomy, as it should have been. - AKA resonance......
People back then liked that type of sound as an upgrade to the typical table radios of the era.
But I wanted better, being a sort of audiophile that I am.
I wanted stellar response from that nice old cabinet, something remarkable as possible, within reason.
A few trips to Home Depot/Lowes, and brought home 3/4 inch solid pine panels.
I gutted the internals of the console to populate it with a better electronic chassis, and better larger speakers.
After designing on paper what was to be, and hoping for the best, I went to work and fired up the table saw.
Lining the whole cabinet with the pine panels - including gluing those thin veneered sides that boomed, I configured the internals to mount the guts, including a newer, nicer Garrard record changer.
12 inch woofers, midranges, and tweeters now lived inside, on a solid 3/4 inch baffle.
Certain additional modifications were needed, mainly a sub-sonic filter to prevent loud-volume feedback of the record changer (using a magnetic cartridge of course).
And tailoring the preamp/amp to suit the resulting sound took a few tries as well.
GUESS WHAT??
No more boomy RESONANCE! - even with the large woofers.
Clean, clear, rich, distortion-free room-filling lovely sound.
Even my audiophile friends that stopped to audition it by were impressed.
And some of them guys are picky-picky, moreso than I am.
So yeah, resolving cabinet resonace in my case was an excellent thing, and well worth the effort.
This is an early photo of the internals - those alnico woofers have been replaced by high-excursion cloth-roll ferrite monsters that dig deep and sound tremendous.
Also, added is rear panels with a port, internal polyfill stuffing, and proper crossovers.
My feelings are that only the speakers themselves should produce sound.
When I first got this lovely, virtually pristine 1960's console stereo, I naturally brought it back to working order, not that it had issues, but as a restorer I have extensive experience in vintage equipment.
The 106 year old lady that passed away three homes away from me owned it, and probably only dusted it over the decades, hardly used.
The side walls were walnut veneered 1/4 inch plywood, the front speaker baffle was 1/2 inch plywood, sporting 8 inch woofers and cone tweeters.... basic, mass produced stuff by RCA Victor.
The overall sound was sloppy-boomy, as it should have been. - AKA resonance......
People back then liked that type of sound as an upgrade to the typical table radios of the era.
But I wanted better, being a sort of audiophile that I am.
I wanted stellar response from that nice old cabinet, something remarkable as possible, within reason.
A few trips to Home Depot/Lowes, and brought home 3/4 inch solid pine panels.
I gutted the internals of the console to populate it with a better electronic chassis, and better larger speakers.
After designing on paper what was to be, and hoping for the best, I went to work and fired up the table saw.
Lining the whole cabinet with the pine panels - including gluing those thin veneered sides that boomed, I configured the internals to mount the guts, including a newer, nicer Garrard record changer.
12 inch woofers, midranges, and tweeters now lived inside, on a solid 3/4 inch baffle.
Certain additional modifications were needed, mainly a sub-sonic filter to prevent loud-volume feedback of the record changer (using a magnetic cartridge of course).
And tailoring the preamp/amp to suit the resulting sound took a few tries as well.
GUESS WHAT??
No more boomy RESONANCE! - even with the large woofers.
Clean, clear, rich, distortion-free room-filling lovely sound.
Even my audiophile friends that stopped to audition it by were impressed.
And some of them guys are picky-picky, moreso than I am.
So yeah, resolving cabinet resonace in my case was an excellent thing, and well worth the effort.
This is an early photo of the internals - those alnico woofers have been replaced by high-excursion cloth-roll ferrite monsters that dig deep and sound tremendous.
Also, added is rear panels with a port, internal polyfill stuffing, and proper crossovers.