Cabinet dampening - to stuff or not to stuff?

[ViolenceOnTheRadio]

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]

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!

[ViolenceOnTheRadio]

Originally Posted by Elipse

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.

[chlorofille]

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 ?

[ViolenceOnTheRadio]

Originally Posted by chlorofille

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.


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?

[chlorofille]

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.

[ViolenceOnTheRadio]

Originally Posted by chlorofille

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.

[TerryO]

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]

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

[TerryO]

To make sure that we're all on the same page, dampening is the act of applying moisture to an object, while damping is the suppression, or quieting of something (ex. to damp your wood stove, is to adjust the venturi effect, using a damper, of the chimney).

Best Regards,
TerryO