minor tweek for a pair(s) of vintage speakers

budgetaudio6

budgetaudio6

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ive thought about this for a while. and ive had the material to do the job. but i cant bring my self to do the project.

first it was to do it with my infinitys. then the corals(they sound like they need it). not so much with the infinitys.

ok to the point. ive been wanting to add some damping glued to the inside walls of the speakers. either pair. or both if i have enough left over.
i bought 2 camping bedding matts. doesnt say what theyre made of. but it feels like theyd provide the internal damping of resonances im looking for.

the brand is ozarks trail camping pad. has anyone tried a variation of this method. and how did the end results sound. with the infinitys they have the fiberfil in them. im wondering if i can achieve the same results with the padding glued to inside walls. ive been reluctant to deviate from the originality of the speakers. altho i think that it could only improve the sound. but i havent been able to bring myself to do it. so im wanting feed back of some of your experiances with this tweek. many thanks
 
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I'm far from the expert, but it looks like closed-cell foam. It'll dampen, but it'll also reduce the effective internal volume of the cabinet.
 
ive had that in consideration as well,echowars, thats why im on the reluctant side. ive tried to do the math on how much it would reduce the size internally on the infinitys. but im stumped. and factoring on how it would affect the bass responce. if i average out the amount used and cut it into foot sized squares i think it would come out to .13 to .18 cubic foot . per l and r side. though that is probably far off the mark.

now on the corals i think it wont matter as much. they have a resonance i can hear in the bass frequencys. gives them a nasal sound if i remember correctly. its a huge cabinet, with a ten inch woofer. currently they are stuffed with body pillows. the speaks are in my kids room. with bass boost and all we got some good spls out of them. quite surprising when it happened
 
Regarding your Corals, have you considered bracing them internally, side to side and front to back with wood studs? Put a couple of them in each plane, and you should reduce the resonance by a great amount at the lower frequencies.
 
If you can get it, dense-pack rock wool is stellar for damping. Otherwise, just staple a few layers of pillow batting to the walls.
 
Spasticteapot said:
If you can get it, dense-pack rock wool is stellar for damping. Otherwise, just staple a few layers of pillow batting to the walls.
Click to expand...

AFAIK, that rock-wool stuff is THE BEST material to use for dampening, and it will not reduce the effective interior size of the box. That said, it is nasty stuff to work with, and --as has been made famous with AR speakers-- can over time contribute to corrosion in metal crossover components. If you are putting it inside a speaker, be careful not to get it on your skin or to breathe dust from it, and consider housing your crossover to protect against it (or moving the crossover to an external location).

The dacron polyfill (pillow batting) mentioned is a more common substitute; it is much easier and safer to work with, but isn't quite as good. (Almost, and most people prefer it just because of the ease of use. I tend to prefer the rock wool, on the basis that after renovation you will rarely open the speakers again, and the stuff stays sealed harmlessly inside. Why not use the acoustically best stuff, if it only means a minor hassle every decade or two?

The only way to be really sure whether a dampening material will improve the sound of your speakers is to TRY IT. Put it in first in a way that is easy to remove/undo. Do one speaker first, so you can A/B compare the sound with an untreated one. Then unless the difference is really dramatic and it is obvious whether it is an improvement or not, listen for a while, to give your ears time to adjust to the "newness factor" and to see if there is increased listener fatigue. Only when you are sure you know which one you prefer, should you remove the treatment or treat the other speaker, as appropriate.
 
hifi_nut said:
Regarding your Corals, have you considered bracing them internally, side to side and front to back with wood studs? Put a couple of them in each plane, and you should reduce the resonance by a great amount at the lower frequencies.
Click to expand...

what thickness would be appropriate here. right now i dont have anything thats appropriate and wont for a while.
 
Arkay said:
AFAIK, that rock-wool stuff is THE BEST material to use for dampening, and it will not reduce the effective interior size of the box. That said, it is nasty stuff to work with, and --as has been made famous with AR speakers-- can over time contribute to corrosion in metal crossover components.
Click to expand...

Not to mention speaker driver frames. Ever see those old AR drivers on eBay and wonder how the hell speaker frames could rust inside a "sealed" cabinet? Rock wool is hygroscopic (absorbs moisture, in this case, from the humidity in the air). There's a reason why AR switched to fiberglas (which, technically, is still a mineral wool, since it's made of silica) in the 70's and stone-based mineral wool is widely used today as a root-supporting medium in hydroponic gardens
 
Acousta-stuff, rock wool, etc. are good damping materials, but they will not keep cabinet panels from vibrating. Bracing is very effective. It will reduce vibration and also raise the resonant frequency of the panel. They also won't reduce the volume significantly. 1x2 braces to break up the longer panels into smaller ones is easy to do and cheap. They can be lumber, mdf, particle board, etc. Panels that are glued the inside surface can be effective, but are not as effective as bracing. If you want to add panels to the inside surfaces carpet padding (the foam type made with various chunks of different color and density) is about as effective as anything. It needs to be glued (spray glue works OK) to the surfaces. Obviosly it will reduce the volume. The type of padding used for back packing mattresses is usually made to be light weight and probably won't be very effective.

Jon
 
all good suggestions here. but i think im going to stay away from the rock wool. in other news when i got my bozaks they had this yellowish brown stuffing. not sure what it is. but the contacts were quite corroded with some wierd colored corrosion.

i have 2 types of spray on glue i can use. and ill test one speaker with out gluing it and see how it performs. but used with the glue and without will have different results in regards to bracing...i gotta think about what i can use thats laying around.

im not concerned about reducing volume on the corals, theyre huge with a huge port. which i think is strange, wonder what they had in mind.

ive read around here that someone has used another type of foam to line the walls of his infinitys. cant remember the screen name tho. wonder what he thought of his results.
 
Whispermat, Black Hole 5 and Sonic Barrier (Parts Express) are the best for panel damping. They all need to be adhered to the walls. Carpet padding is cheap and works. Sometimes carpet padding can be gotten free if you ask at a carpet store. They may have some they have removed that is still OK for this use. Mass is crucial! Egg crate or light weight foam is a waste of time.

Jon
 
would this foam i have not work as well as id like it to? maybe a combination of using the bracing and this foam to reduce internal reflections be more benificial. either way it will be a week or two before i get this done. but i thought it would be better to plumb the depths of your knowledge before i proceed. my patience is key ive learned from previous threads i started:D


nor do i want to put too much money in them.
 
Bracing is the most effective. Some 1x2 on each panel. Glue the thin edge to the panel. This will stiffen it the most. Put it off center an inch or so, so that it divides the panel into unequal sections. This is to insure the panels resonate at different
frequencies (nothing you can do will completely stop them from vibrating). Bracing between opposite sides is also effective, but needs to be tight and secured well to both sides. I think the stiffening of each panel is easier and less likely to come undone. The idea is to decrease vibration of the panel by stiffening and making the resonance higher so that it is not excited as much by the power of the lower frequencies

I'm guessing the foam you bought is fairly light weight? If so, it will not be as effective as something more dense and heavy. The foam carpet padding, heavy felt carpet padding or the special pads I mentioned. The panels designed to do this are fairly expensive. Adding mass helps (inertia and all that). It is best too glue it to the panel. The foam, or whatever, is to absorb some of the backwave energy to decrease the effect on the panels. There is only so much you can do, but this will help significantly.

Rarely do vintage speakers have bracing. The bigger the speaker the more the panels will vibrate. Tests done on cabinets that are not properly damped or braced showed a significant amount of sound from the vibrating cabinets. Obviously, this isn't good.

Speaker stuffing is not very effective for decreasing cabinet vibration. It works well for acoustic suspension cabinets by making them effectively larger and of course in transmission lines to absorb higher frequencies and make the line effectively longer.

Jon
 
i like the bracing idea best. that sleeping bag pad is in the right direction , but lacks the
mass you'll need for absorbing resonance . a dense rubber mat would be more
appropriate, as would a jumbo tube of Liquid Nails or silicone caulk.
a series of heavy beads might fit the bill if you can't find rubber pads.

take a piece of plywood and experiment. glue different materials to it and rap on it
with your fist . choose the one that works best. i think a 1/2" or so dense rubber mat,
like a doormat..
or 1 x 2 bracing is your best bet.
good luck.

karlo
 
thanks for your insights, i think what itll come down to is to glue on te bracing, going with the 1x2 glue three of them onto one panel(on each panel) and then glueing on the foam padding onto the bracing and see if the glue will hold onto the foam. ive thought about the rubber mat approach and ive gone as far as asking for a price of how much ill need. but that was a while back and i dont remember the details. but its more than id like to pay for, these are bigger than the estimated size i got the quote for.
 
Arkay said:
AFAIK, that rock-wool stuff is THE BEST material to use for dampening, and it will not reduce the effective interior size of the box. That said, it is nasty stuff to work with, and --as has been made famous with AR speakers-- can over time contribute to corrosion in metal crossover components. If you are putting it inside a speaker, be careful not to get it on your skin or to breathe dust from it, and consider housing your crossover to protect against it (or moving the crossover to an external location).

The dacron polyfill (pillow batting) mentioned is a more common substitute; it is much easier and safer to work with, but isn't quite as good. (Almost, and most people prefer it just because of the ease of use. I tend to prefer the rock wool, on the basis that after renovation you will rarely open the speakers again, and the stuff stays sealed harmlessly inside. Why not use the acoustically best stuff, if it only means a minor hassle every decade or two?

The only way to be really sure whether a dampening material will improve the sound of your speakers is to TRY IT. Put it in first in a way that is easy to remove/undo. Do one speaker first, so you can A/B compare the sound with an untreated one. Then unless the difference is really dramatic and it is obvious whether it is an improvement or not, listen for a while, to give your ears time to adjust to the "newness factor" and to see if there is increased listener fatigue. Only when you are sure you know which one you prefer, should you remove the treatment or treat the other speaker, as appropriate.
Click to expand...

the corals have sometype of damping stapled to the panels i think its the carpet padding stuff or something similar. unfortunatly it will be a while before i can take the speakers apart to try anything on them. carpets are getting cleaned professionaly next weekend. ill be able to post listening pics then(when all the mess is gone):)
 
unless you're adamant on justifying a use for those blue mats..... i doubt they
will do anything but reduce the working volume of your speaker cabinets.
but, what do i know........try it out first.
 
I brace almost all my speakers that are bigger than 2-way bookshelves, and even those if the size of an EPI 100. 1x1 cut slightly under length and PL400 construction adhesive on both ends. It expands slightly as it sets so it will make up for slight under-cut. I also do the front back brace just above the woofer cut out. That way I can catch the brace with the top center speaker mounting screw (longer to go into the brace). Then one black headed drywall screw from the back into the brace and you are flex free. Makes a huge difference in cleaning up the bass and making the sound more coherent :)
 
Regarding the foam padding, I have a pair of Micro-Acoustics FRM-1ax speakers that have what looks like 1 1/2" to 2" open-cell foam stuffed inside. It was the original "filling." The dense, self-adhesive material used to dampen auto body panels can be pretty effective damping cabinet panels. It's considerably easier to apply than glued &/or screwed braces. Just my 2 cents.
Bob
 
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