Enclosure Liner?

[Greg_M]

The other day I had my KLF-20s apart and saw that it had some foam rubber type material behind the woofers.

Anyone know what this is? Is it just simple foam rubber or is it a special material?

[SWL]

Pics?

Sent from my SM-G950U using Tapatalk

[Greg_M]

I've got them back together now.

It just looked like plain old creme colored foam rubber, spongy stuff. Maybe an inch or so thick.

 

[JohnA]

It is damping material that helps tune the cabinet resonance.  By compressing and absorbing energy, it makes the cab behave like it is larger than it is. 

 

Don't add damping to a cab designed without it or change or remove it from one that has it. 

[pzannucci]

Added mainly to stop standing waves and internal box resonances. 

That piece really doesn't do much for pretend increases in box volume.

[SWL]

Added mainly to stop standing waves and internal box resonances. 
That piece really doesn't do much for pretend increases in box volume.

This just got me thinking. I remember those pieces of foam in the RF-7's that I used to own but can't remember any ever being in my KLF-30's.

I'm positive that after recently fixing up both pairs of my 30's that there definitely isn't a loose piece of foam at the bottom.

Should I call Klipsch to get some and put it in there.....or what could I buy locally that would work?

Sent from my SM-G950U using Tapatalk

[SWL]

Let me clarify by saying that there IS foam behind the tweeters, mids and from what I remember....down to somewhere behind the top woofer(?).

But definitely not a loose piece laying on the bottom like the RF-7's had.

Sent from my SM-G950U using Tapatalk

[Greg_M]

I'm trying some NuFoam Pad - 27" x 10 Yards x 1" thick from Joann fabrics who has it on sake at the moment. It supposed to be the real deal taking the place of fiberglass insulation. Their blurb.....

The versatile Fairfield Poly-Fil NU-Foam 27" x 1" x 10Yds. has something for everyone, from little ones to young campers and elderly. Besides being an ideal choice for playpen mats and crib bumpers, this densified polyester batting is great for sleeping pads, recreational vehicle accessories and comfy chair cushions. This 100% polyester batting is non-allergenic and mildew-resistant, making it a safe choice over traditional foam. Plus, it doesn't turn yellow or disintegrate over time.

 

People are saying mice things about it for this application.

https://www.joann.com/nufoam-pad-27in-x-10-yards-x-1in-thick/14195788.html#start=1

Their website ordering page really sucks and I had to call them and sit on hold for an hour or so because the webpage wouldn't let me order.

We'll see how this stuff works out.

[PrestonTom]

If that material is open cell foam, then it might work (although the density might not be optimal). If it is closed cell foam, then it will make things worse. The material that is best (and recommend by JBL) is the 1 inch pressed fiberglas (or "blanket") that is used for lining HVAC plenums and ducting. 

 

Also, it is claimed by JBL (in their recommendations for sound installations etc) that lining the 5 sides (not the baffle) with 1 inch material will cause the cabinet volume to act as if it was 10% larger. So a 5 cu ft cabinet would now be 5.5 cu ft. For a sealed cabinet, this may not matter much, but for a ported cabinet this should be included in the initial calculation of the port geometry (and later verified and tuned by means of an impedance plot). I understand that some of the above posts negate this view. 

 

As far as the lining  absorbing the back wave from a woofer, I have always taken that argument with a grain of salt if you are talking about a woofer. The wavelengths over much of their spectrum are simply too large to be impacted very much by a 1 inch piece of material. I would guess the effect would only work at the highest frequencies (shorter wavelengths).

 

Good luck,

-Tom

[pzannucci]

20 hours ago, SWL said:

This just got me thinking. I remember those pieces of foam in the RF-7's that I used to own but can't remember any ever being in my KLF-30's.

I'm positive that after recently fixing up both pairs of my 30's that there definitely isn't a loose piece of foam at the bottom.

Should I call Klipsch to get some and put it in there.....or what could I buy locally that would work?

Sent from my SM-G950U using Tapatalk
 

Most open cell egg-crate foam, like cheap mattress toppers, works pretty well.  Also folded polyfill for like blankets and other crafts (Hobby Lobby/Joanne/Walmart).  Adjust amount to suit.
I know my first KLF-30s I tried the "more makes the box bigger" to try and extend bass.  It killed the bass.  Try differing amounts.

 

17 hours ago, PrestonTom said:

If that material is open cell foam, then it might work (although the density might not be optimal). If it is closed cell foam, then it will make things worse. The material that is best (and recommend by JBL) is the 1 inch pressed fiberglas (or "blanket") that is used for lining HVAC plenums and ducting. 

 

Also, it is claimed by JBL (in their recommendations for sound installations etc) that lining the 5 sides (not the baffle) with 1 inch material will cause the cabinet volume to act as if it was 10% larger. So a 5 cu ft cabinet would now be 5.5 cu ft. For a sealed cabinet, this may not matter much, but for a ported cabinet this should be included in the initial calculation of the port geometry (and later verified and tuned by means of an impedance plot). I understand that some of the above posts negate this view. 

 

As far as the lining  absorbing the back wave from a woofer, I have always taken that argument with a grain of salt if you are talking about a woofer. The wavelengths over much of their spectrum are simply too large to be impacted very much by a 1 inch piece of material. I would guess the effect would only work at the highest frequencies (shorter wavelengths).

 

Good luck,

-Tom

The bass wavelengths are usually too long so you wouldn't necessarily be absorbing the low frequencies but changing how the box acts and the reflected higher frequencies.
Many believe that the % increase of the box size is more with sealed vs ported cabinets and from the speakers I have built and tuned, it really depended on how the box and woofer behave as a whole.
An old pair of Paradigm Studio monitors I had (original before Studio 100) had barely any open space in the bass reflex cabinet.  With that cabinet and Vifa dual 8" woofer combination, was very punchy and the extension trounced k-horns that sat next to them.

Measure and listen.  See what actually works with the combo.  Don't kill the life of the speaker trying to gain extension.

[Greg_M]

On 2/26/2020 at 8:10 AM, SWL said:

I'm positive that after recently fixing up both pairs of my 30's that there definitely isn't a loose piece of foam at the bottom.
Tapatalk
 

 

It's not loose, it's attached to the back of the box.