THX recommends filling Speaker cabinet with poly-batting?

[wfo1955]

I read in another forum that an audiophile dude that has 7 channel system with klipsch' speakers. It was either a monthly newsletter from Home Theatre Magazine or Monthly Audiophile Magazine. Beside the Klipsch' he had a 200w amp and an otherwise good preamp and other neat stuff. He stated that he had a problem with his RC 64II. A blog from several members stated that THX recommends installing a poly-batting, similar to pillow material behind the speakers n the cabinet. Not tight, but simply packing the batting surrounding the rear of the speakers. He didn't say how many hours the speakers had been used, nor any real problems, but that the speaker system just wasn't emitting great dialogue/punch.

Has anyone heard of this? Has anyone DONE this and what were the results.

[CECAA850]

I used sound deadening in the compartment surrounding my RC-7 but only because it is rear ported. I don't know what the benefit would be for a sealed speaker unless it was recessed in the opening and you were trying to reduce cabinet reflections.

EDIT I didn't see the "n" which I'm assuming you mean "in" the cabinet. I was referring to the cabinet my speaker sits in.

[mustang guy]

I have been told on good authority that microfiber towels crumpled up are the best. You can buy them in large packages at Sam's for pretty cheap.

"On Ralph Hellmer's suggestion, recently, I removed the "Acousta stuf" in the line and replaced it with 16 per cabinet cabinet "micro fiber towels" crumpled up. I got another octave of bass with this change. They now will shake the raised slab floor in my living room at medium volume." BassmanBruce

[Guest " "]

I have been told on good authority that microfiber towels crumpled up are the best. You can buy them in large packages at Sam's for pretty cheap.

"On Ralph Hellmer's suggestion, recently, I removed the "Acousta stuf" in the line and replaced it with 16 per cabinet cabinet "micro fiber towels" crumpled up. I got another octave of bass with this change. They now will shake the raised slab floor in my living room at medium volume." BassmanBruce

I have some old socks with holes in them that I was going to throw out....maybe I can use that....it looks like micro fiber?????

[mike stehr]

The socks are for blocking the ports.

[moray james]

You can also try perlite but you will need to contain it. B&W publishe an interesting paper on the use of activated charcoal but it is a mess to handle trust me perlite is so much cleaner. If you want to check out the concept for cheap and easy use rice crispies while not near as effective as perlite you will be surprised and youe speakers will be snap crackle pop approved. The micro fiber cloth sounds like a very good idea. I would suggest rather than scrunching them up that you layer and space the layers as the motion of a cloth layer itself will eat up a considerable quantity of energy on its own. TRY it out anf tell us what you find.Best regards Moray James.

[Chris A]

I wouldn't change anything inside a Klipsch speaker just because someone SAYS it's better. I'd do it because my ears told me that it was needed.

[bs] <-- that's my vote for the recommendation that you read somewhere else.

Chris

[moray james]

no harm in experimenting as you can easily put things back the way they were to begin with if you like that best. Damping which does a better job over a wider band is a bonus. Especially if it opens up the cavity volume to better resonate with your passive or ports. Thats one of the draw backs of volume stuffing with poly fill, you need the cavity to be free to resonate with the passive or vent at the tuned frequency with a good strong resonance so they will couple. The woofer has to drive the passive or vent into resonance then the passive or vent needs to couple to the woofer to damp its motion. That the reason why you used to only see damping on three of the inside walls of a cabinet or not at all.Best regards Moray James.

[Chris A]

I'll stand by my recommendation, above. If you want to believe that Klipsch didn't design and produce their speakers with enough internal damping, think again...I wouldn't mess around unless there is a noticeable issue. Most of the time, it's the room, the amplification chain, or the recordings, not the internals of Klipsch speakers...

Chris

[moray james]

I am not knocking Klipsch engineers one bit. Klipsch like any other company has to get the job done as cost effectivly as they can and good enough at the right price counts big time in production. Looking for that last ounce of performance can be very expensive from both a time and material point of view. Playing with internal damping is a good excercise for learning how and what to listen too. I think anything that gets you both interested and critically listening for a while is a good thing. As I said what ever damping that was in the cabinet stock can be put back any time with no harm done. I redamped a pair of small ATC monitors with perlite in place of the fiber stuffing and the difference was dramatic. Perlite like activated charcoal is a mess to deal with and must be contained. Micro fiber cloth stapled or glued in place spaced from the cabinet walls would likely be very effective. Open cell foam as inside my KLF20 has a limited band of absorption but it gets the job done just not as well as other options. The speakers are mine to play with as I choose and anybody who wants to play is free to do so and wise to keep the factory damping as a base reference point. More or less damping is not the issue here that is the effectiveness of the damping used. If you can achieve more bass extension with better articulation what`s wrong with that? Best regards Moray James.

[mustang guy]

I have been told on good authority that microfiber towels crumpled up are the best. You can buy them in large packages at Sam's for pretty cheap.

"On Ralph Hellmer's suggestion, recently, I removed the "Acousta stuf" in the line and replaced it with 16 per cabinet cabinet "micro fiber towels" crumpled up. I got another octave of bass with this change. They now will shake the raised slab floor in my living room at medium volume." BassmanBruce

FYI, he was not talking about Klipsch speakers, but one of Ralph Hellmer's older design speakers. They are about a 3' tall bottom ported design.

[DavidF]

I read in another forum that an audiophile dude that has 7 channel system with klipsch' speakers. It was either a monthly newsletter from Home Theatre Magazine or Monthly Audiophile Magazine. Beside the Klipsch' he had a 200w amp and an otherwise good preamp and other neat stuff. He stated that he had a problem with his RC 64II. A blog from several members stated that THX recommends installing a poly-batting, similar to pillow material behind the speakers n the cabinet. Not tight, but simply packing the batting surrounding the rear of the speakers. He didn't say how many hours the speakers had been used, nor any real problems, but that the speaker system just wasn't emitting great dialogue/punch.

Has anyone heard of this? Has anyone DONE this and what were the results.

Loose-fiber fill materials have been part of speaker building for decades. What exactly are you asking about, though? Whether anyone has experience with using poly fill or even this particular kind of poly material?; whether any enclosure could benefit from a poly fill (assuming it was not designed with same to begin with)?; whether THX actually drills down into specs so as to call out what kind of fill should be used?

[moray james]

damping is damping, not to say that it does not make a difference but that it can be applied to any design. I used microfiber sheets when I first saw them quite some years ago to make absorption donuts to place over the spiders in some Fostex full range driver I was working on. They were cut the diametre of the spider and layered up to about a half inch thick very light (which was what I was after) and they did an excellent job of eating up the spider talk. the finer the fiber the more fiber to fiber contact you will have and that means more friction and that means you will shift more acoustical energy int heat. That`s how fiber damping works. Best regards Moray James.

[wfo1955]

nah, I probably won't screw with my Klipsch', after reading the replies, I kinda think Mr. Paul knew his shi%, after all, I think he set the standard in the 40's.....heck, I haven't even set my system up yet....I just stare at them boxes, waitin' to build my mancave. I just read it and wondered if it truly is a problem at all, y'all would have known about it already. I think the best thing is to set up everything EQ, a fatty and dig in...thanks for the info as always....

WFO1955

[mike stehr]

There is a formula for the amount of polyfil used for a given volume cabinet. The larger the cabinet, (enclosure) the less effect the polyfil has.

If a speaker cabinet has a objectionable peak in the woofer response, (say 70Hz) polyfil can help knock down the peak/ring at that frequency.

If one has a way to input sine waves to the system's speakers, you can sweep the lower frequencies and easily discern the peak/peaks in the woofer response. Room response comes into play as well...sometimes that peak may be from the room.

This are my experiences with a pair of 4 foot volume ported cabinets with 12" coaxials. I get a smoother bass response using the polyfil...not a lower response. With the peak dampened down, I can now more easily hear the lower response.

Ramblings of a rank amateur.

[SWL]

Most of the time, it's the room, the amplification chain, or the recordings

I agree. However, there's probably no harm in experimenting with jamming a bunch of dampening material into a cabinet that wasn't designed for it....or is there? [:|]

[Don Richard]

Stuffing a box makes it appear larger acoustically. This could affect the tuning of the box. Unless you measure the resulting output of that box all you know is that it sounds different (or not).

[colterphoto1]

damping or polyfill does two things

1. Dampening is generally used on one of each of two parallel sides to reduce standing waves inside the cabinet. Cornwalls and Heresy cabinets are good examples of this. Back, Top and one side are normally covered, not the port opening. Klipsch used an open-cell foam on the Ref series and pro speakers to this same purpose although it's usually just a single panel of foam (stocked in 12" widths) curved around a side/back inside the cabinet.

2. stuffing loose poly fill inside a speaker cabinet has an entirely different purpose. Generally used in sealed 'acoustic suspension' designs (re: NOT most Klipsch), it effectively increases the overall density of the air inside a cabinet, making the volume of the cabinet appear larger to the drivers.

I would not attempt to modify any Klipsch designs (especially any bass ported or passive woofer designs) by installing loose polyfill inside the cabinet. Dampening the interior of any secondary cabinets that the speaker may inhabit (in an in-wall installation for example) would be very strongly advised to avoid any spurious vibrations and boxy sound. A problem with trying to A/B compare changes of this sort is that it doens't work well with center channels, our auditory memory is not long enough for a instantaneous comparison of the sort that is needed for an accurate listening evaluation. If you want to try something like this out yourself, modify ONE cabinet, then place them side by side in the same acoustic space, play a mono source to them and have someone else hit the A/B button as you listen from a usual listening position.

Michael

[BigBoxAudio]

Is there something missing in my Heresy's?

I just purchased a 1978 pair of Heresy's. When I looked inside, there is no acoustic batting. Did that come later, in the Heresy II or III versions?

[derrickdj1]

I would think there should be some type of damping material. Adding polyfil in the cabinet may increase the bass response. This is an old trick with subwoofers to make it behave as a bigger box.