Adding More Speaker insulation?
- Thread starter theoman
- Start date
Register to hide this ad
thomo57
Super Member
My story with damping
I had a pair of speakers built a couple of years ago.
Over that time l experimented with various materials.
The speakers were in and out of service over that time period because l wasn't happy with the sound until very recently.
It was a lot of work openening them pulling the old damping out and cut and install the new.
I tried various materials, egg crate foam, rock wool and finally on a shredded cotton matting that picked up some where.
They sounded very good until l thought they could sound better with some more which wasn't the case.
I went one step to far by adding the last sheet which l immediately removed.
Just trial and error with various materials and various amounts is what l found
I had a pair of speakers built a couple of years ago.
Over that time l experimented with various materials.
The speakers were in and out of service over that time period because l wasn't happy with the sound until very recently.
It was a lot of work openening them pulling the old damping out and cut and install the new.
I tried various materials, egg crate foam, rock wool and finally on a shredded cotton matting that picked up some where.
They sounded very good until l thought they could sound better with some more which wasn't the case.
I went one step to far by adding the last sheet which l immediately removed.
Just trial and error with various materials and various amounts is what l found
darkblue94
The Devil made me do it.
I would suggest that you look into adding some cross-bracing inside those enclosures. That would go a long way towards reducing panel flexing and vibration loss which in turn improves bass response.
Hirschp1
Member
+1 to what darkblue94 thomo57 posted. I have always had my best results in "tuning" with polyfill (e.g. https://www.amazon.com/Fairfield-Po...=1504096848&sr=8-1&keywords=polyfill+stuffing or just tear open a non-down filled / non-foam pillow and that's probably going to be the inside).
The way I was taught and understand this adding insulation thing is that the point is to slow the sound waves from reflecting off of the inside of the cabinet and bouncing back to the cone, which can and will muddy the sound of the woofer and even sometime return to the cone at a 180 degree "out of phase" position with what the cone is then producing, which will actually cancel the notes. The longer /bigger shape of the bass waves make sthem more susceptible to this effect. Adding the insulation/polyfill can help in a similar way to having a larger cabinet, which is to reduce the reflection by reducing these unwanted reflections.
I am not an expert, I am just repeating the condensed version of what I was taught and observed in the real world over the course of my roughly 10 years as a professional car audio installer. I am absolutely certain that I only understand bits and pieces and there are real-deal qualified people in this forum that make me look like a drooling idiot. But, I have seen and experienced the effectiveness of both bracing and polyfill/insulation. in the correct combo they WILL make a difference!
Try adding enough to loosely fill behind the woofer in equal height to the height of the woofer in the cabinet some, listen, then remove or add in quantifiable amounts (maybe you do it by weight maybe you just consistently pull or add a certain amount of "handfuls" it just needs to be a quantifiable amount).
The most obvious bracing that I would add is horizontal under the horn between the cabinet's two sidewalls. I imagine that bracing will significantly reduce the flex in that cabinet (maybe just a couple 1"-2" wide strips of 3/4" thick plywood would be a good cheap way to start and see what difference it makes).
The way I was taught and understand this adding insulation thing is that the point is to slow the sound waves from reflecting off of the inside of the cabinet and bouncing back to the cone, which can and will muddy the sound of the woofer and even sometime return to the cone at a 180 degree "out of phase" position with what the cone is then producing, which will actually cancel the notes. The longer /bigger shape of the bass waves make sthem more susceptible to this effect. Adding the insulation/polyfill can help in a similar way to having a larger cabinet, which is to reduce the reflection by reducing these unwanted reflections.
I am not an expert, I am just repeating the condensed version of what I was taught and observed in the real world over the course of my roughly 10 years as a professional car audio installer. I am absolutely certain that I only understand bits and pieces and there are real-deal qualified people in this forum that make me look like a drooling idiot. But, I have seen and experienced the effectiveness of both bracing and polyfill/insulation. in the correct combo they WILL make a difference!
Try adding enough to loosely fill behind the woofer in equal height to the height of the woofer in the cabinet some, listen, then remove or add in quantifiable amounts (maybe you do it by weight maybe you just consistently pull or add a certain amount of "handfuls" it just needs to be a quantifiable amount).
The most obvious bracing that I would add is horizontal under the horn between the cabinet's two sidewalls. I imagine that bracing will significantly reduce the flex in that cabinet (maybe just a couple 1"-2" wide strips of 3/4" thick plywood would be a good cheap way to start and see what difference it makes).
thomo57
Super Member
I just experience over doing the damping again today.
I have open baffle speakers homemade with 12 inch Goodmans front mounted and l cut another baffle and rear mounted them.
They have some polyfill in them.
I was recently given a roll of sound deadening foam which l thought I'd try as an additive to the polyfill.
After listening to them for a day or so l noticed a very big difference Which l attributed to the rear mounting because I'd forgotten I'd put the extra damping in a few days before l cut the new baffle.
I opened them up and pulled it out and the magic of these speakers returned.
I have open baffle speakers homemade with 12 inch Goodmans front mounted and l cut another baffle and rear mounted them.
They have some polyfill in them.
I was recently given a roll of sound deadening foam which l thought I'd try as an additive to the polyfill.
After listening to them for a day or so l noticed a very big difference Which l attributed to the rear mounting because I'd forgotten I'd put the extra damping in a few days before l cut the new baffle.
I opened them up and pulled it out and the magic of these speakers returned.
mark warren
Music Lover!
That makes sense there is a lot to know about speakers! 
I love all these different speakers AK members have!
I love all these different speakers AK members have!sum of sand
Active Member
Remove stuffing for more bass
More as in less taut flabbier midupper bass hump
but sometimes it helps. Make sure walls are covered but you can create a bit of a hollow section behind the woofer while stuffing tight the upper half of cabinet
More stuffing yields tighter bass
More as in less taut flabbier midupper bass hump
but sometimes it helps. Make sure walls are covered but you can create a bit of a hollow section behind the woofer while stuffing tight the upper half of cabinet
More stuffing yields tighter bass
What model Altec speaker is that?
In Altec vented enclosures such as the OP's the insulation is intended to absorb midrange from woofer so it's not reflected back through the cone--the insulation is not intended to have an effect on bass response. With a vented enclosure the best way to change the bass response is to change the venting or venting and enclosure size. Download a program that models vented enclosures and play around with it; see what various venting schemes will do with the enclosure size. These old Altec systems were designed before the days of T-S analysis and were the result of trial and error using formulas we now know were limited. But trial and error by very talented engineers. As a general rule with the Altec 416 woofer, which it appears the OP has, a bigger box, properly vented, is needed for deeper bass. Think of a box the size of the Altec Model 19.
One can experiment with stuffing the box I suppose, it's reversible. Who knows what might happen? Probably make things worse.
One can experiment with stuffing the box I suppose, it's reversible. Who knows what might happen? Probably make things worse.
Last edited:
