Cabinet dampening - to stuff or not to stuff?

How important is it really?

Some of my cabinets have sounded much better with it, some have sounded much better without it. While it adds resistance, I built some 4x2x2 cabs that will house dual 15's with aluminum cones. Some rather tough speakers. I have good foam rubber floor padding with the diamond texture to glue through out the entirety of the cabinets.

Generally to my ears, an undampened cabinet makes the music sound more alive and punchy, a dampened cabinet makes it sound more focused and defined. These are intended to be used to produce maximum volume for live band performance so I'm unsure whether punch or focus should be made the priority.
 

Elipse

Member
2010-09-19 11:52 am
London
I am pretty novice re speaker design but am just in the process of experimenting with some 50L cabinets, vented, with a 10" driver (for home use). In this instance approx 25%, loosely packed sounds the best balance of depth, punch and focus. Every case is different as you say.

However, for the use you state, in my opinion - "alive and punchy" every time!
 
I am pretty novice re speaker design but am just in the process of experimenting with some 50L cabinets, vented, with a 10" driver (for home use). In this instance approx 25%, loosely packed sounds the best balance of depth, punch and focus. Every case is different as you say.

However, for the use you state, in my opinion - "alive and punchy" every time!

That does seem to be the more logical feel the cabinets should produce since it will be live bands playing through them rather than movies, video games and CD's at home or the bar.

Maybe someone who does live sound on a regular basis will have some insight. I plan to finish these cabs Sunday or Monday and have to decide on how much bracing to add and if I should insulate these monsters.
 
It depends on the type of enclosure's rigidity. I tried stuffing some very solid enclosures, 75kg bookshelves, and the sound got dry and boring. A touch of natural harmonics from the MDF was missing.

For some of my smaller projects which use much thinner materials - 18mm MDF, the stuffing helps a lot in reducing some resonance and makes the bass a bit tighter.

Which of your cabinets exhibited negligible improvements after you added damping ?
 
It depends on the type of enclosure's rigidity. I tried stuffing some very solid enclosures, 75kg bookshelves, and the sound got dry and boring. A touch of natural harmonics from the MDF was missing.

For some of my smaller projects which use much thinner materials - 18mm MDF, the stuffing helps a lot in reducing some resonance and makes the bass a bit tighter.

Which of your cabinets exhibited negligible improvements after you added damping ?

A chipboard sub I built as well as a plywood sub both sounded like a fart when I stuffed them and playing with quantity didn't help. A couple of 80's possibly 70's salvage cabs of what seems to be a weird laminate and MDF hybrid greatly improved from stuffing as did the 1.4 cubic foot sub cab I built for my car last week out of 3/4 inch birch and loaded with a good quality but budget priced 15. A small set of full range bookshelf style speakers built out of 1/4 inch ply with dual 3 inch drivers greatly benefited from stuffing.
All my guitar cabs of course sound best empty.

Here's the new build ready to be cut for twin 15's and a plethora of peizo tweeters..either 5 or 7 haven't decided yet.
[IMGDEAD]http://i54.tinypic.com/70uj2f.jpg[/IMGDEAD]

I have to decide on dampening them with that colored foam rubber floor padding sold everywhere for kids to play on and, adding bracing. That stuff is the most ideal and cost effective dampening material I have come up with particularly with the diamond texture. The cabs are incredibly solid which can be expected at this size but if they get the heavy use of being carted from gig to gig as I intend, more strength is important and using pine 2x4's split down the middle for rib style bracing won't add much weight. I'll also add a single wheel in the center of the bottom at the rear so they can be maneuvered like wheelbarrows. Undecided on what I'll use for handles.

On top are the shells to the economy cabs using 10's from the same model line of woofers. I figured I need something more portable as well. These started out as a 4x10 cab I split in half last night. It was semi open back, no batting and at ear draining volumes, very clear and defined.
Maybe the issue of solid wood and good ply vs MDF and HDF has a lot to do with how much batting effects or even improves the sound. Maybe the primary benefit from adding dampening material is the ability to push a bit more volume without distortion?
 
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Thanks for the info. I can't figure out why the plywood/chipboard subs did not improve after the stuffing. Maybe natural wood resonance begs to be undamped !

Most of my speakers (hifi use) are made from MDF enclosures, and have fairly thick cones. Speakers such as fullrange type often have very thin and lightweight cones so if stuffing is not added, some reflections may return through the cone and smear the sound or create a "shout".

I bet your next gig is sure to sound great.
 
Thanks for the info. I can't figure out why the plywood/chipboard subs did not improve after the stuffing. Maybe natural wood resonance begs to be undamped !

Most of my speakers (hifi use) are made from MDF enclosures, and have fairly thick cones. Speakers such as fullrange type often have very thin and lightweight cones so if stuffing is not added, some reflections may return through the cone and smear the sound or create a "shout".

I bet your next gig is sure to sound great.

That leads me to assume I was correct in theorizing that since the cones are aluminum, I don't have to worry about dampening unless the cabinet itself has turbulance noise. Due to it's size, being 3/4 birch ply and dual venting, I probably don't need to dampen it or even bother with bracing the cab to handle gas pressure.

I guess the only thing left to do is cut my speaker holes, install everything then test it by ear. I can get away with taping in dampening material to compare to one without but not sure if I can come up with a way to test braces without screwing them in.
 
It depends on what you need to accomplish the design goals. It appears that there is a lot of misunderstanding on this thread. There is cabinet damping, which deals with spurious and harmonic vibrations of the cabinet itself. Bracing, added mass and good design usually will deal with these. Stuffing the box, or lining the box with acoustic absorbent material is for back wave attenuation or for "enlarging" the volume of the box as seen by the driver. Transmission lines present a different need for damping, etc,.

They serve different purposes and depend on a host of variables, including the "Q" of the driver.

Best Regards,
TerryO
 

ronin1953

Member
2008-06-24 9:58 am
Basics to the theme

I give the hint to read the basics in my pges at the thread related to twelve-way-crossovers this thread. the page on insultion is not finished in the moment- but it will be availible till the end of this week....
the disputed question is not only related to the resonace of the wood but it also touches the problem of "standing waves". taking a closer look to the pages might give better understanding to several aspects of the problem....
the titel at the moment in the thread is remaining Final Solution though you schould refer to the last entries of the thread.
hope this might help...
ronin1953
 

ronin1953

Member
2008-06-24 9:58 am
After all the time spent in repeating the definitions and getting a lesson to anglistic I thought by myself - it might be a good idea to turn back to the initial question. The Question can´t be answred that simple to stuff or not to stuff. If I understand the initial starting post correct the post targets more with the handling of the lower frequencies and does not bother the higher frequencies that much - so the reason to remind here in the thread to the standing waves and wave reflection within the speakercase is directly focusing to the fact that the precise legth of a soundwave or the precise half lenth or quater of a wavelength ( that results legths with values between few meters and going down to values of 50cm to 60 cm .... ) in a closed case causes special effects to the backside of the membrane of the operating speaker and that these effects take place beside the resonancefrequencies of the wood used to build the case. So for that reason i pointed to the pages at the thread Ultimate Solution due to the fact that there this question is treated and viewed in detail with respect to a close look to the "modus operandi" of electromagneticspeakers. The issue to answer the question in this thread is to do a little bit of mathwork before a speakercase is built and that the target of the mathwork will result measures that should be avoided when building a case for speakers with determined frequencyranges to avoid disturbing effects and I at least for myself answer to the given question in that way: stiffing in a speakercase has multiple effects to the sound by spreading and splitting up reflections with the target to lower risk of resonance and it also affects to the speaker by reducing working volume of air within the case that requires more electricity to run through the coil of the speaker to do same work and deliver same soundpressure as recognized in an unstiffened speakercase. Not stuffing is the better solution but in case that the Soundsystem has been determined with failure -i.e. it has mistakes in the construction that might leed up to resonacefrequencies stuffing the case might be the only solution to rescue the system to produce an acceptable sound.
 
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It depends on the type of enclosure's rigidity. I tried stuffing some very solid enclosures, 75kg bookshelves, and the sound got dry and boring. A touch of natural harmonics from the MDF was missing.

For some of my smaller projects which use much thinner materials - 18mm MDF, the stuffing helps a lot in reducing some resonance and makes the bass a bit tighter.

Which of your cabinets exhibited negligible improvements after you added damping ?

You can also get that wooden sound from rear facing speakers in a folded cabainet.

I would go for a amount of good filling.
 
dampening is the act of applying moisture to an object, while damping is the suppression, or quieting of somethin

Althou these are the most commonly used definitions for these terms, it had previously been determined that dampening & damping can be used as synonyms.

All other posts ref this subject have been deleted. Back on topic please.

dave :cop:
 
Generally to my ears, an undampened cabinet makes the music sound more alive and punchy

Typically caused by reflections & standing waves coming back thru the cone. This time smear does nothing good to fidelity of your speaker.

If severe enuff, this energy makes the speaker louder so it may seem better. It is not.

A speaker can be overdamped, and in any "vented" enclosure too much can change the alignment.

dave
 
Typically caused by reflections & standing waves coming back thru the cone. This time smear does nothing good to fidelity of your speaker.

If severe enuff, this energy makes the speaker louder so it may seem better. It is not.

A speaker can be overdamped, and in any "vented" enclosure too much can change the alignment.

dave

I did a "raw" sound test earlier on the single cabinet I've nearly finished.
I've proposed to only dampen the rear panel then on the corners where the top and bottom panels meet the rear panel, place large panels at 45 degree angles to bounce the sound more efficiently out my ducts.

Sounded great, minus the 1 dead piezo tweeter that was unfortunately new out of the box, but I really disliked how much sound was escaping through the rear panel. What was lost through the side panels I feel can be considered negligible.
I suppose this means dampening the top, bottom and rear panels while leaving the sides, corner "bounce" panels and baffle alone so I still get some nice punchy wood resonance.
 
Up to the point here there are still some facts not availible to clearly answer the initial question.
By example it might be usefull to post the thickness of the panels and if there are used different thick panels on different sides it schould be mentioned too - the postes covering different effects on different sides of the case seem to indicate that different thicknesses have been used.
next the range of frequencies the Speaker is determined to operate at might be usefull too.
At the first posts the Speaker seemed to be only determined for lower frequencies, but later posts indicating a piezo now beeing in that system make the impresion that the speaker shall cover higher frequencies too.
And next to indicate the reason to ask about the thickness of the wood and the kind of wood used - might be covered with a short hint:
In really satisfying Speakersystems the panels are made of hardwood ( i.e. beechwood or plywood of beech and at least 48mm thick ! ) because in larger cabins less thick wood ( for example from Pine or thin 28mm MDF ) is too soft and more working like an oversized membrane instead working as a solid case.
second to explain what shall be used within the case might be helpfull to - due to the fact that even that a piezo is itself in a "closed cabin" - integrating such a speaker in the case has mutiple effects.
Such a speaker also spreads out sound to its backside allthough it is closed there and therefor it issues soundwaves into the case too.... that might leed up to the decesion to give the piezo an seperated and stuffened "inner case" within the cabinet to avoid interaction with the other speakers
- and if the "inner cabinet" is designed well - that might also lower risk of standing waves and reflections....
i guess therefor it might be usefull to spot out that facts upfront to further speculations and predictions how a case might react....
 
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Parameters are 25.5" x 24" x 49.5"
3/4" birch ply, who's top layer is unfortunately a cosmetic veneer I discovered from sanding lol.
Front baffle is 42" long, 24" wide with 3" x 24" vents at the top and bottom.

Internal volume is exactly 15 feet.
What I noticed from my sound test was a lot of volume lost through the rear panel. I'm getting the impression I should just damp all the panels.