[ka7niq]

It is IMPORTANT to read the entire thread to follow completely my damping materials experiments !
Sometimes, problems ONLY show up in extending listening to varied recordings!





I recently did the mid woofer upgrade to my older Spiral TRT - RM 40's.
This was a BIG improvement.
This allowed me to turn the panels up w/o getting a hole in the response.
I have many years experience playing with the damping material inside of speakers.
And so, I decided to open the RM 40 mid range panels up.
I WAS prepared to add MORE Fiberglass, but the enclosures were stuffed to the gills with fiberglass already!
I decide to remove the fiberglass, and try some conventionally stuffed Dacron instead.
The Dacron sounded better.
So, that is when I decided to try a trick i learned.
I put 1/2 the amount of Dacron back in I took out, and compressed it as flat as I could against the back of the enclosure.
Then, I added  1/2 of what I had left into a second layer about 1/2 as compressed as the first layer.
Then, I added what was left to a loose layer right behind the ribbon drivers.
At NO time did I ever place any damping material behind the Tweeters in ANY of my experiment.
I simply left an "open space" behind the TWEETERS to  allow the ribbons to "breathe".
More on that later.

I re assembled the RM 40 with the new Dacron Variable Layer damping in it, and Oh My ....

It sounded so good, I did the other RM 40 just like it, and listened.
I liked what I heard .
A BIG improvement IMHO over the stock sound.

My single driver buddies have been raving lately about Kapok, an organic material made from the seeds of the  Kapok tree.
I read a Patent about it, and it worked GREAT in my Von Schweikert's.
I just bought a used set of older JBL L7's.
They are a 12" 4 way, and had a really bad lower midrange male voice coloration.
So, I damped the lower midrange with Kapok.
No luck!
Could NOT get rid of the lower male voice coloration.
THOUGHT Kapok "sucked" as damping material.
Even told Brian that my experiments were unsuccessful!

Fiberglass in the JBL lower midrange "got rid" of the lower male voice coloration.
And so I THOUGHT fiberglass was better.

I then found the designer of the older JBL on the Lansing Heritage Forum.
He told me what I was hearing was the upper range of the 12" driver, NOT the lower mid!
It seems he choose to cross over at 180 hz from the 12 to the 8" lower midrange!
What REALLY was happening was the fiberglass was choking the 8" lower mid so bad it SEEMED to clean up the voice, LOL

And so there I found myself with nice sounding, Dacron stuffed RM 40's, but wondering what IF I used the Kapok instead of Dacron ?

And so, I played one RM 40 down, unscrewed the mids, and in went the Kapok.
Relying on the data in the Patent, and my friends from the "single driver world's" advice, I used LESS Kapok then Dacron.
Kapok is supposed to be a superior damping material, meaning you can use LESS of it!
Theoretically, one can have his cake, and eat it too.
The "cake" being the lively sound of a driver NOT choked to death by an excess amount of damping material.

It is a FINE line between an overdamped condition and low coloration.

Ideally, one wants ONLY as much damping in a midrange enclosure to reduce coloration w/o sucking the very life out of a driver.

I put slightly less Kapok then Dacron in a variable density layer damping scheme, with ONE exception.
The very last loose layer I used Dacron to "keep" the Kapok "in place".
The improvement was drastic.
I listened to Tom Petty, Bob Seeger, and Lyle Lovett.
Passed Male Voice with flying colors.
Then, I listened to Eva Cassiday, Emmylou Harris, and Stevie Nicks on Fleetwood Mac.
I then listened to some Jewel and Pat Benatar.
Then Paula Cole.
No more "shout" at the top of female vocal range.
Satisfied,I then re did the other RM 40 with the Kapok/Dacron damping scheme, and set back to listen.
I was very pleased with the sound.
Suddenly the midrange had "life" again, with even lower coloration then before!

My friend Mike who also owns RM 40's was called to "bring me back to reality".
Mikes power was out, and he came over.
He thought they sounded better too.

I have NOT tried the Lambs Wool, but the Kapok/Dacron sure works.
It is my opinion that it takes so MUCH Fiberglass to lower coloration it "chokes" the midrange, robbing it of the life it is capable of.
More effective damping materials take LESSER amounts to lower coloration then Fiberglass, and thus give more air space to the midrange panels.
IMHO, this allows these wonderful drivers to Breathe, giving more warmth and immediacy to the sound.

Now, I can hear the BODY of guitars, instead of just the strings.
Some Bright female vocalists no longer "shout" like they did.
Trumpets sound like Trumpets, not Clarinets, and reediness in the Saxophone is more apparent.

Perhaps the Lambs Wool damping does as good or better, I haven't tried it ?
I am happy, so far with the sound of the Kapok/Dacron in my RM 40's.
We MIGHT do my friend Mikes like this, and if our friend Kevin wants, we can do his too ?
All 3 of us own older RM 40's here in Tampa.

Oh, almost forgot, I intentionally left the space right behind the tweeters OPEN w/o any damping.
The backs of the tweeters are enclosed, and I WANTED the mid panels to have as MUCH "breathing room" as possible.
Initially, with the first Dacron stuffing, I DID stuff that area too.
I understand WHY theoretically one might want that area stuffed as well.
But I trust my ears, and  it sounded "overdamped" with that area filled in.
I could detect NO coloration from NOT stuffing that area, but did notice a loss of midrange "life".
I left it unstuffed in all following experiments, and it remains that way.

I will leave you guys with this, I am going to go listen right now!

2.30 am EDT - Well,, after two hours of listening I must say I remain impressed!
The "Lean" tonal balance of the RM 40 is ALL gone now.
I have moved my levels up to 2.30 on my mids and 3 o'clock on my tweeters!

Here is what I THINK is going on.
In an attempt to damp the colorations out of the enclosed ribbon mids, a LOT of Fiberglass is required.
This DOES damp the backwave, BUT it also "robs" the mids of doing their  part of the crossover.
This places a lot of the burden on the upper woofer to 'fill in" for the missing lower range of the ribbons.
Since Kapok is a FAR superior damping material, as claimed in the Patent, it takes much less to do the same as a LOT of Fiberglass.
Now, with less total damping material in it's midrange chambers, the wonderful Neo Panels Q is altered from really overdamped and lean to a higher Q condition that is now "warm and rich".
This Higher Q lower range blends better with the midwoofer
allowing one to increase levels!

I find that in the stock condition I have to turn the levels way down to get a good blend between midrange and woofer.
This often resulted in a shouty quality in the upper midrange.

THINK about it ?
IF the lower range of the ribbon is LOW Q, it is lean, but the rest of it is FLAT !
So, when you adjust to compensate for the ribbons lower range leanness, as the driver flattens out as frequency increases a KIND of broad  "peak" forms.

This "highlights" the upper mids.
The combination of this lower range leanness, and broad, upper midrange "plateau" created by the over damped panels keep RM 40 from being all  it could be IMHO
Kapok  "frees" the RM 40 owner from this.

I have 40 lbs of Kapok, and will keep enough to do my friend Mikes RM 40's, and Kevins if he wants at no charge.

I want to have some Kapok  around because I am ALWAYS playing with speakers.
I AM going to send a bunch to Brian so he can try it.

The Neo Midrange Panels are wonderful drivers.
But because the diapraghms are so low mass, it is really important that reflections from  the rear wave be well damped, or severe coloration's result.
LOTS of Fiberglass works for damping, but lowers Q more then I like.
Kapok damps as well as Fiberglass with MUCH less amount.
It does not lower Q as bad, and so provided a warmer, fuller, more "organic" sound.

I give the credit for the Kapok "discovery" to my single driver friends over in Europe.
I "grew out of" Lowthers and Fostex and Jordan Modules years ago, LOL
But my old buddies are still "keeping the faith" with their crossover less single driver contraptions.
They SWEAR by Kapok damping, and told me about it.
I must say, THIS time they made a believer out of me!

[ka7niq]

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[Early B.]

Cool!

Where did you purchase the kapok?

[ka7niq]

I got mine here http://www.zafustore.com/kapok.html
They are in Texas.
They have some crazy pricing policy.
The more you buy the cheaper it gets.
I think the 40 lbs I bought was actually cheaper then 20 lbs, weird!
5 lbs should be enough to do both RM 40 midrange chambers with plenty left over for the bedroom speakers, friends, etc.

[Vapor Audio]

Sounds like a load of poo ...

[ka7niq]

Have YOU tried it ?
It sure made a BIG difference on my speakers.
It is very inexpensive to do as well.
I just listened to my RM 40's again this morning.
The RM 40 is a "different" speaker in this regard.
It is tunable.
Last night, I was listening to some real well recorded stuff.
This allowed me to increase the mid/tweeter levels.
This morning, I had to reduce the levels to make regular recordings sound better.
But, I am still able to run my levels well up past the point I used to run them with the fiberglass.

The sound is fuller, more alive, and more "weighted" to the lower midrange.
IOW, a warm, BBC Type sound with great transparency.
I was not getting this type of sound with the fiberglass.

Even Paula Cole sounded great, a SURE test of midrange damping.
IF Paula shrieks at you, it is often IME a result of inadequate damping.

Same with Abba and Heart.
On Hearts :Crazy on You" song, the guitar solo was rich and warm at the beginning of the song, and Anne Wilson voice was rendered w/o harshness.
I KNOW what Ann Wilson sounds like.
I lived In Seattle right across Lake Washington from her.
I have seen Heart many times in concert, and unplugged.
Her voice is powerful, and has a unique sound.
The Kapok damps it very well.
Kapok is also used in the manufacture of paper speaker cones.
And suprise, suprise, suprise, It is the stuffing used in my 57 inch wide screen rear projection TVs speakers, LOL

Believe it or not, I "went into" the TV Set's speakers and replaced a crossover cap with Poly, LOL

[jonbee]

I appreciate all your work on this. I've experimented with fill materials on many speakers, and it really does make a difference. It just takes a lot of trial and error to get the right balance.
I had been thinking about re-doing the damping on my RM30s, but didn't want to go through all the trials you did.
If you've got some kapok to sell, I'd like to participate- or if any others want a group buy, I'd go in on that too.

[ka7niq]

I appreciate all your work on this. I've experimented with fill materials on many speakers, and it really does make a difference. It just takes a lot of trial and error to get the right balance.
I had been thinking about re-doing the damping on my RM30s, but didn't want to go through all the trials you did.
If you've got some kapok to sell, I'd like to participate- or if any others want a group buy, I'd go in on that too.

Yes Jonbee, it made a HUGE difference in the sound.
Kapok is cheap, real cheap.
Here is where I got mine from http://www.zafustore.com/kapok.html


Like I said, I had my best results from putting a loose bunch in each enclosure, then smashing it down so it compresses against the back of the mids enclosure.
Then, I added a second looser layer only compressed 1/3 as much as the first layer, then finally a looser layer of Dacron on top of it all.
This almost completely took away the "overdamped" sound I was getting in my room with my equipment.
It was almost like adding a tube amp, w/o using tubes.

The sound sees to "breathe" and flow more, and generally sounds more alive.
The body of instruments are more apparent now, and the overall sound is more "BBC like" then Thiel like.

[jonbee]

The kapok looks very loose. Will it tend to slump to the bottom of the subenclosures over time?

[ka7niq]

It is not as loose as it looks, a handful of it is about like Dacron.
Once you compress it, it stays put.
I opened the RM 40's middle upper ribbon up to stuff some Kapok into the air space behind the two spiral tweeters in the old RM 40's.
I THOUGHT I heard a bit of coloration, and I purposely left this space empty of any damping.
I over did it this time JonBee.
Yes, the coloration is gone, but so is the Magic.
I will have to remove some.
Actually, if it was not such a PITA to remove all the screws in the ribbons, I would like to hear the ribbons with NO damping at all behind them !

I was in Walgreen's today Jon Bee, have you ever seen those foam water noodle things ?
I was thinking, why not cut one in half, and place it behind the ribbons ?
Curved side UP of course ?
It might act as a diffuser for the back wave ?
Damping is weird JonBee, ya never know what is going to sound best till ya play.

When you think about it, NOTHING can stop the back wave anyway, it's going to hit no matter what!

The "theory" on no damping at all is this.
ALL the back wave hits all the drivers at the SAME time.
Any Damping material in the enclosure is going to have different rates of absorption/reflection as the damping material "releases" sound.

Coincident Speakers designer Israel Blume does not believe in damping materials in his speakers.

I am "on the fence" as far as this debate goes.
I only care about good sound, how I get it is unimportant to me.

That Foam Water Noodle is looking better and better JonBee.
I want to pull ALL damping out from behind the panels, and listen ?
I will leave one speaker alone, and pull all damping from the other, and compare.

I know, THEORETICALLY, it should not work.
The ribbons have a thin membrane and reflections SHOULD get through the membrane.
But guess what ?
They are getting through anyway, even stuffed to the gills.
IF the RM 40 mid range enclosure were BIGGER, maybe enough damping could be used to almost eliminate this, but the enclosure is relatively  small.

Someone else reported best results with foam strips.
THAT makes sense to me because foam is more uniform, and would tend to 'release" it;s stored energy all at the same time compared to haphazardly compresses Dacron Fiberglass or even Kapok.

Nothing makes a failure JonBee but a try.
And so, I am going to keep playing with damping, or lack of it in my RM 40's.
Thank GOD I have a cordless screwdriver, LOL

[ka7niq]

Well, I did not try the "Foam water noodle diffuser" Jon Bee, but I did remove all the damping from one RM 40.
I compared it to the partially Kapok stuffed RM 40.
It was almost un listenable
But, I listened anyway, for a good while, to a lot of different recordings on the undamped RM 40.
I did this to familiarize myself with the sound of the back wave hitting the mid range ribbon driver.

Then I listened to the half Kapok stuffed RM 40.
MUCH, but not ALL of this coloration was gone.

And so I decided to stuff the undamped RM 40 to the gills with compressed Kapok.
I did, and almost ALL colorations were gone compared to the 1/2 Kapok stuffed RM 40.

The sound took on an almost eerie transparency on the completely Kapok stuffed RM 40.

Gone was ANY trace of shout in Ann Murray's or Stevie Nicks voice.
Voices were much smoother and organic sounding, and sibilance was lessened.

Strangely enough, this complete stuffing made the speaker less tolerant of some bad recordings.
Air Supply sounded positively dreadful.
But on the 1/2 stuffed RM 40 it was almost tolerable.

Styx's Dennis De Young singing "I'm Sailing away" and Mrs America are bright recordings, but Dennis's voice was clear and uncolored and sounded better completely stuffed.

Anne Murray sounded a LOT better completely stuffed, as did Mary Chapin Carpenter and Stevie Nicks.
All 3 of these girls are sometimes closely miked, and have low lower ranges.
You can HEAR the added warmth of the 1/2 stuffed RM 40 compared to full damping.

I prefer the fully stuffed speaker on these 3 girls.

Tom Petty was fuller sounding, but less transparent, on the 1/2 stuffed speaker, as was Eric Clapton.
Elton John sounded TERRIBLE on the 1/2 stuffed speaker, but wonderful on the full stuffed one.

Bob Seeger singing "Turn The Page" is a real BITCH to get right.
On the 1/2 damped speaker the Sax blared like a clarinet, and when he sang "East of Omaha" there was a distinct coloration on the first part of the word "East"

Full stuffing toned down the sax, and removed ALL coloration from Bob's voice.

It sounded so good, i listened 3 times!

On Stevie Nicks singing "Landslide" from the Fleetwood Mac Rumors album I noticed something strange.

I heard a small shout at the top of her voice on the fully stuffed RM 40.
I backed the tweeter down a couple of notches.

 have ALWAYS had to run my tweeters a BIT higher then my mids to "cover up" what I THOUGH was a small peak in the ribbons upper range.
I could NOT believe my tweeter level was a TAD lower on the fully stuffed RM 40.

Finally, I heard enough, and fully stuffed the other RM 40.

I backed it's tweeter level down and listened to the pair.

They are WAY, WAY more transparent fully stuffed.
Yes, a LITTLE "life" is gone, but great transparency appears.
They are a LITTLE less tolerant of bad recordings now since there is no coloration's to hide stuff anymore.

On GOOD recordings, they will drop your Jaw.
Bad recordings you WILL hear.

!/2 stuffed makes em more tolerant of the bad stuff, but the great transparency is lost.

These are my findings from much experimentation and HOURS of listening.

IMHO, even 1/2 Kapok stuffed RM 40's sound vastly superior to the stock Fiberglass filled speakers.
Fully stuffed with Kapok, it is no contest.

A JBL Engineer from the Lansing Heritage forum told me that compressing Fiberglass ruins it;s damping effectiveness.
And IMHO and experience, Fiberglass is NO match for Kapok.

Kapok, like Dacron, likes to be compressed as long as one doesn't get TOO crazy.

Perhaps Wool is as good, or even better then Kapok, don't know.
But I can report there are GREAT sonic gains to be had by changing the damping materials in RM 40's.

If you are hearing "strange things" in your mid range, and it just don't "sound quite right" you MIGHT be hearing the limitations of the Fiberglass ability to really suppress the back wave of the mid range driver ?

Before you keep losing more money searching for the "magic amp" wire, interconnect, DAC, transport, etc, etc I would suggest you simply open up your mid range enclosures and stuff with Kapok.

Or, try the wool damping from Brian ?

It is my opinion backed by hours of listening that the VMPS mid range driver is very special.

It's high performance is due to a really light diaphragm in a powerful push pull magnetic field.

Because the diaphragm is thin and light for fast response, it is also really vulnerable to "attack" from it's own back wave.

The BETTER you can stop and absorb this back wave, the better it will sound, period.

I MIGHT still install a curved foam diffuser behind the Kapok, stay tuned to this thread.

But for RIGHT now, I am just going to enjoy the fruits of all my time spent, and just enjoy!

[JP78]

freak.

[jonbee]

Very interesting stuff.
I don't know what was used in my RM30s.
In general, I like the mid balance on them, but the top end of the mid panels do seem to have a rising character, causing too much sibiliance, for instance.
With the cdwgs in place, that is gone, but to me they are too polite, even with mids and highs all the way up.
I'm experimenting with grill cloth materials, to see if I can filter off the top end of the mids, without deadening the dynamics.
All in all, they are tantalizingly close to perfection, to my ears. Just a few more tweaks and...?

[ka7niq]

Very interesting stuff.
I don't know what was used in my RM30s.
In general, I like the mid balance on them, but the top end of the mid panels do seem to have a rising character, causing too much sibiliance, for instance.
With the cdwgs in place, that is gone, but to me they are too polite, even with mids and highs all the way up.
I'm experimenting with grill cloth materials, to see if I can filter off the top end of the mids, without deadening the dynamics.
All in all, they are tantalizingly close to perfection, to my ears. Just a few more tweaks and...?

Well, what I say may be controversial, but you KNOW me, LOL
The Panels are wonderfully flat, but REAL sensitive to rear wave reflections.
Thus, they require a LOT of damping material to stop and absorb the rear wave.
Further listening has convinced me that I went TOO far in overstuffing my panels with Kapok.

The TRICK is to get JUST ENOUGH damping that it absorbs the rear wave, but does not Choke the panels lower range!
What happens I think is too much damping chokes the lower response of the ribbons "creating" a slightly rising response that plays hell with the timbre of instruments.

I plan to remove some Kapok, and maybe I can get it just right.

BTW, the Kapok has a totally different sound then Fiberglass, it is warmer, and more "organic" sounding, less "sterile".

I really think it is the answer for the damping material in the RM 40's, although I have not tried wool.

Dacron lies in the middle between the sterile sound of fiberglass, and the warmth of Kapok.

[audiochef]

Hi guys, well I've been riding this (maxed out) midrange version for quite some time now. Since lining with acoustic foam and damped  with lambs wool, I've never looked back. Yes Chis I'm glad your also finally discovering this mod .These mids truly are special.

My opinion of a true test is to play any Sinatra. No need to explain what he SHOULD sound like. Incorrectly damped mids will just sound thin and harsh. My favorite female reference vocal is the outstanding recording of Wlldwood Flower by Reese Witherspoon on the Walk the line sound track. Properly reproduced,her voice should sound hauntingly rich with not a trace of glare. I never tire of this remarkable presence in my room.

The signal delivery is also crucial, with my very modded  Tube Audio designs Tad-60 driving the mids and tweets ,I don't envy anyone else's system. ......... Well maybe Houstous

[BrunoB]

The TRICK is to get JUST ENOUGH damping that it absorbs the rear wave, but does not Choke the panels lower range!
What happens I think is too much damping chokes the lower response of the ribbons "creating" a slightly rising response that plays hell with the timbre of instruments.

I can confirm  your observation with measurements of the frequency response of the mid range driver with an enclosure. Without stuffing: the FR shows several resonance peaks. With stuffing, the resonance peaks disappear but the low frequency response is not as good. I am using an open box 626, the mid range enclosure is much larger and open in the back. I still have to stuff it to eliminate resonances.

Kapok sounds like an exotic material. Has anyone tried cotton balls? Yes, I mean the cotton balls you can buy at CVS. I know that it performs well  but I haven't done a careful listening comparison.

Bruno

[jonbee]

Audiochef- can you describe the foam you used to line the walls? Also- how tightly did you stuff the wool?

Ka7- any further progress to report?

I may take a stab at this w/ my RM30s, although at this point I think the mids are very fine. I don't know what Bryan used for damping in my speakers.

I've been doing some other simple "mods" on my speakers, which I will report on soon. The sound is more breathtaking than ever.

[BobRex]

I'd have to pop a driver out to check, but I  thought the woofers were damped with fiberglass and the mids were damped with lamb's wool.  I think this is the case since B "discovered" (in quotes because it was actually a member of the circle that alerted B to the wool's advantages) wool, which was about the same time as the RM30s were developed.  I think all RM30s have the same internal filling.

[jonbee]

If B indeed uses wool, I'll probably leave them alone. I've used wool in the past, and it is indeed far better than synthetics I've heard. As I said, I have no problem with the mids now. I was bothered by the tilted up top end on the mids, but some simple experiments with slit grill cloth covers for the mids has allowed me to fine tune the top end of the mids, and has solved that issue for me. I'll post some pics of this soon.

[Early B.]

I just ordered some kapok to experiment with the mids on my Tower II SE's. I'll report back in a week or two.