[John Casler]

As I posted several days (weeks) ago, I was wondering what the RM40 would sound like with a "sculpted" baffle like the RM/x.

Well not being a wood worker and I wouldn't wreck my RM40s by trying it anyhow, I looked for a simple solution to reducing cabinet refraction, to see what it sounds like.

The only method I could come up with is to secure a sound blocking/absorbing substance like acoustic foam to absorb and block the sonic energy refracting off the cabinet face.

Does it work?  I say yes.  I have performed many listening tests with the tweak and the cleanliness to the soundstage seems much improved and it seems to have not introduced any negative effects.

I ran a frequency sweep and didn't find any suck outs or blips of any kind.

Now I found my RM40s (nearfield) and on axis were rather incredible anyhow, but this seems to take them one step further.

It is rather cheap and easy to do, and not a permanent tweak and will stay as long as you enjoy it.

I would say that I spent less than $45 tops (for materials such as the foam, tape, glue, etc) to get this result.

Now I am sure that "sculpting the cabinet would yield better and more significant results, but since Tyson ask the question, I tried to find a "fun" answer.

While I continued to experiment, I realized that I had always been slightly concerned with "ceiling bounce" since the upper woofer is "highly dispersive (compared to the neopanels) and it is rather close to the ceiling if you have standard 8-9 foot ceilings.

One option is to "acoustically treat" the ceiling, the other is to reduce the sound sent to the ceiling.

So I simply put a "hood" of the same material sitting on top of the RM40 to also block and absorb the energy lauched upward.  The hood in the picture can be moved forward as much as nessessary to experiment with this blockage.

Does it work?  Yes.  I played Stevie Ray Vaughan's Tin Pan Alley and the difference in "recorded" reverb and room generated reverb was clearly evident.  THE HOODED VERSION HAD MORE AND CLEARER REVERB!!!

The untreated ceiling (I have 9 foot, so 8 foot might be even worse) was "blurring" the reverb.

So I found these rather cool and VERY EFFECTIVE.

Now I cannot vouch for their appearance,  but the hood can be removed when "serious listening" is over.  I suppose if you were industrious enough to use velcro for the "lapels", they too could be put on and off at will.

Does this make the RM40 sound like the RM/x?  I doubt it, but it does offer a fun tweak to play with and to my ears it offers a good improvement.

It "does not" dramatically limit dispersion laterally as it might appear.

I used 3" acoustic foam found at most places that sell this stuff.  I used brown, although it looks a different color in the pictures.

I you decide to try this tweak, yo wil probably have to purchase a 24"x48" sheet and perform a little surgery.  

Acoustic foam can only be cut well with a "bread knife" or better yet an electric knife (nothing else will work)

I also picked up 12 sheets of this 24x48 foam and have placed it at various spots around my room to good effect too.

Will it work for other speakers?  I suppose it would.  In fact it wouild probably work even better for "high dispersion" speakers.  Like I said it didn't seem to change the dispersion of the VMPS, but they are limited anyhow.  In a "high dispersion" cone, it might offer significant improvement in focus and delineation, and "space" between instruments and vocals.  If you try it with that type of speaker let me know.

I even figured out how to make the sheets into BASS traps in the corners.

Since I don't have my act together in posting pictures to a post like this, I'll just have to add them to my gallery.

So to get an idea of what I just posted go here looks like go to the following URLs:



http://www.audiocircle.com/index.php?action=gallery;area=browse;album=75

http://www.audiocircle.com/index.php?action=gallery;area=browse;album=75

http://www.audiocircle.com/index.php?action=gallery;area=browse;album=75

[Tyson]

I'm thinking that black foam on the front of a full wrap black RM40 might look a little nicer  

But I know from personal experience that the "ceiling bounce" tweak does work nicely.  Unfortunately there is NO way I could get spousal approval to put foam on the front of my full wrap rotary cut white birch veneer. . .

[jethro]

John,

I was wondering what type of finish is on the RM40's in your pics ?

A bit off topic, I was also wondering if it is possible to get fire-retardent acoustic foam sheets ?

Thanks.

[John Casler]

I'm thinking that black foam on the front of a full wrap black RM40 might look a little nicer  

But I know from personal experience that the "ceiling bounce" tweak does work nicely.  Unfortunately there is NO way I could get spousal approval to put foam on the front of my full wrap rotary cut white birch veneer. . .

Hi Tyson,

The actual color of the foam is not what turned out in the photo (looks kinda maroon when it is actually a deeper brown - must be the flash)

I have changed the 3rd URL to show the hood for the top.

If one was a little more creative than myself, you could mount the foam on a small rigid strip and "plug it in" to the center speaker grill slot so that they were easily removable "without" any velcro "spots" on the speaker.

Jethro wrote:

I was wondering what type of finish is on the RM40's in your pics ?

The finish is Cherry Flambe

I was also wondering if it is possible to get fire-retardent acoustic foam sheets ?

I beleive most acoustic foams from the major suppliers "claim" to be flame retardent, but they also tell you not to test it.

It is rather inexpensive from Foambymail.com.

If your buying a lot, let me know I might be able to save you a couple dollars.

[jackman]

Thanks for the suggestion.  If I ever want to get divorced, I'll give you a call and purchase a pair of those with all that ugly foam and put them in my living room.   I can't think of a faster way of getting all my stuff thrown out on the lawn and the locks changed on my house.

Jman

[John Casler]

Thanks for the suggestion.  If I ever want to get divorced, I'll give you a call and purchase a pair of those with all that ugly foam and put them in my living room.   I can't think of a faster way of getting all my stuff thrown out on the lawn and the locks changed on my house.

Jman

I just sent a pair of RM40s to a great "marriage counselor" in your area.  Let me know when you need an appointment.  

[John Casler]

As an adjunct to the tweak.  I didn't mention in the post that I used the 3" foam because I wanted to further restrict lateral dispersion.  This would be valuable to those who have close side walls.

I think that for those who wish to only reduce cabinet defraction/reflection that a good strip of very thick "felt" will pretty much eliminate most refraction without much reduction in dispersion.

As I said, I didn't notice any specific decrease in lateral dispersion, but for those who might want to experiment, the thick felt might offer another tweak of value.

(Actually, any material with highly absorbative acoustical properties might offer an interesting result)

[BrunoB]

As I said, I didn't notice any specific decrease in lateral dispersion, but for those who might want to experiment, the thick felt might offer another tweak of value.

(Actually, any material with highly absorbative acoustical properties might offer an interesting result)...

I tried a week ago a tweak very similar to John's (I was inspired by the speaker tweaks page http://www.tweakaudio.com/Speaker%20Tweaks.html).

My speakers are 626R with black finish. Instead of using foam, I am using a black bathroom rug (microfiber, bought at SEARS, $30).  Presently, two cutted pieces of rug are hold with a rubber band on the each side of the mid panel of my 626R for testing. I plan to cover the whole front panel of the speaker using a complete rug with just holes big enough for the three drivers (the tweeter grey foam will be removed, the rug will then come close to the HET tweeter). I plan to attach the rug with strong velcro on the side.



I choose to use a rug over foam because it is thinner and has (much) more surface. Actually, I don't know if rug is a better material than foam or felt.  I covered my Ascend Acoustics CBM 170 with rug a year ago. I found that with a dome tweeter, the rug cannot be too close to the tweeter otherwise, the soundstage shrinks (but the focus improves), and the amount of treble decreases too much.
With the 626R, I did not observe a significant decrease in soundstage width or treble level. But the stereo focus has improved. However, I still have more A/B comparisons to do.


Just a funny idea that came to my mind after reading the thread about "Bearded" stands (http://www.audiocircle.com/index.php?topic=3340):  if the rug is long enough to reach the floor, you can have a 626R with a "real beard"   - it might work because the rug would not adsorb low frequencies.

Bruno

[Juan R]

Are you guys have any notion about aesthetic?

[tkp]

Are you guys have any notion about aesthetic?

My wife hates all speakers no matter how good or bad they look .  Currently my RM40s have no grill on.  I told my wife they came that way with no grill (I hid them under our bed ).  Since she hate them  all already so it does not matter any way.  I am going to put the acoustic foam on to see how they sound .

[Mad DOg]

Are you guys have any notion about aesthetic?

ROTFLMAO!!!

my thoughts exactly...

as great as the RM40s sound, my wife would NEVER allow those things into our home as long as Mark Schifter keeps producing speakers that look as nice as they do...

[mcm7]

My speakers are 626R with black finish. Instead of using foam, I am using a black bathroom rug (microfiber, bought at SEARS, $30).  Presently, two cutted pieces of rug are hold with a rubber band on the each side of the mid panel of my 626R for testing. I plan to cover the whole front panel of the speaker using a complete rug....

Bruno, please post pictures of your Rug-tweaked speakers!  

[John Casler]

Are you guys have any notion about aesthetic?

Hey Juan,  It's a freakin "AUDIO" tweak, not a custom designer, furniture upgrade.

[John Casler]

My speakers are 626R with black finish. Instead of using foam, I am using a black bathroom rug (microfiber, bought at SEARS, $30). Presently, two cutted pieces of rug are hold with a rubber band on the each side of the mid panel of my 626R for testing. I plan to cover the whole front panel of the speaker using a complete rug....

Bruno, sounds interesting.  Since Brian already "masks" the tweeters you shouldn't have a reduction in sound quality.

as great as the RM40s sound, my wife would NEVER allow those things into our home as long as Mark Schifter keeps producing speakers that look as nice as they do...

OK Mad Dog, for that comment you will have to stop by (when you return the Bryston), and "suffer"   the indignity   of listening to such atrocities, for at least a cut or two.

They are sounding pretty darn good right now.

Don't worry, I'll turn the lights out  

Give me a call

[Brian Cheney]

I considered foam masks on either side of the mid panels, but realized it would take a full 3" thickness to be effective down to 200Hz, cosmetically not an enhancement.

John has seen my soundroom where the ceilings are treated with 3" Sonex, and his idea for "capping" the system therewith is good, as are the thick foam strips down the sides.  

This is a hobby and I encourage such tweaking.  You will reap sonic rewards and the tweaks can be removed when the speaker is not playing.

[Tom]

John, the foam or felt trick on the baffle does indeed work well for speakers which, like the RM 40 and other VMPS models, are standard rectangular boxes without radiused edges to prevent edge diffraction.  This trick goes back at least to the Spica TC 50 with its felt blanket over the whole baffle except the driver cut outs.  

That said, I've tried this sort of thing on several speakers.  I've also tried arranging 3" thick sheets of Sonex around the near field of the  speakers in the old Watkins Echo-Muff arrangement in an attempt to eliminate wall reflections before they happen.  Yes, it works and is far better than no serious acoustic treatment of the room.

But what works even better, if your spouse allows it (and from the sound of things, you guys have a lot of problems with SAF), is to put the sound absorbing foam or fiberglass batts on the walls, floor, and ceiling at the 1st and 2d reflection points of the speakers as viewed from the listening seat.  I use 3" Sonex.  I also use small pieces of this Sonex pressed into all the rooms tricorners to kill off later reflections.  Compared to putting the foam in the near field or extreme near field (right next to or on the speaker) the sound is much more open and yet more focused.  With good recordings, a fine two channel system in a room so treated sounds like surround sound, but better in terms of image and staging specificity.  Of course, this is also more expensive since you need more sound absorbing foam or fiberglass.  It is also potentially yet uglier if you don't cover the foam or fiberglass with decorative cloth.

[Sa-dono]

OK Mad Dog, for that comment you will have to stop by (when you return the Bryston), and "suffer"   the indignity   of listening to such atrocities, for at least a cut or two.

Well I'm glad I don't have the Bryston anymore j/k John...I still want to give a listen one of these days.

[Horsehead]

Hi John,

I'm ready to try the tweak.  Did you adjust your speakers after applying the foam strips or leave everything as is?  What about toe-in? Same? Less?  Do you think some BluTack would work in attaching the foam to front baffle?  How about a straight hood up top, instead of the curved look?  Same effect?  Thanks for taking the time, effort, and ingenuity in developing these tweaks and sharing them with us- taking a great speaker and trying to make it even better!
What's the best source for the 3" wedge foam?  The website you provided seems to only sell the stuff in sheets of 20.  Do dj/instrument/pro music stores such as Sam Ash carry this stuff?

[John Casler]

I've tried this sort of thing on several speakers.  I've also tried arranging 3" thick sheets of Sonex around the near field of the  speakers in the old Watkins Echo-Muff arrangement in an attempt to eliminate wall reflections before they happen. Yes, it works and is far better than no serious acoustic treatment of the room.

But what works even better, if your spouse allows it (and from the sound of things, you guys have a lot of problems with SAF), is to put the sound absorbing foam or fiberglass batts on the walls, floor, and ceiling at the 1st and 2d reflection points of the speakers as viewed from the listening seat. ....

Hi Tom,

Yes I actually picked up several sheets of "acoustic foam" and also treated several wall surfaces too, to good effect.

Does sound like we have a few "whipped" Audiophiles here but peace and tranquility in the household goes a long way.

Since I set up on the "long wall" I don't have any "direct" side reflections, but since the walls are plaster and drywall, sound "is" still bouncing all over the place   and the acoustic treatments certainly help "tame"     some of the gremlins

This all started because of Tyson  

By the way Tyson, maybe some removable birch colored felt might give you a fun afternoon at the fabric store and then the hardware/hobby store.

[John Casler]

Hi John,

I'm ready to try the tweak.  ...

All right

Did you adjust your speakers after applying the foam strips or leave everything as is? What about toe-in? Same? Less?  

I did not have to make any adjustment to the speakers after the tweak, but YMMV.

Toe in stayed the same (on mine that is directly on axis/nearfield)

Do you think some BluTack would work in attaching the foam to front baffle?

Attaching the foam was the biggest problem since I didn't want to damage the finish and just regular tape would not stick to the foam strips.

I finally ended up applying rubber cement on the foam (letting it dry) then sticking about 1" squares of double sided tape to the foam then ataching it to the cabinets (which can be peeled off and cleaned off if nessessary.

Others might find better methods of attachment.  Biggest problem was getting something to "stick" to the foam

How about a straight hood up top, instead of the curved look? Same effect?

I curved the "hood" to also contain a small amount of the side reflections, but my original prototype was just made out of a rectangle of packing foam and had no curve.  When you're done listening these just go in the closet.

I should also mention that you can experiment with how much of the hood "overhangs" the front of the speaker and see what works best.  I found about 4"-5" was sufficient.

Thanks for taking the time, effort, and ingenuity in developing these tweaks and sharing them with us- taking a great speaker and trying to make it even better!

My pleasure, after all it is a hobby where set up and placement make significant differences.  Controling sound through room treatments and tweaks like these seem to have interesting effects, and are rather cheap in the scheme of things.

What's the best source for the 3" wedge foam? The website you provided seems to only sell the stuff in sheets of 20. Do dj/instrument/pro music stores such as Sam Ash carry this stuff?

If you look at that site closer, (scroll down) the 3" foam (24"x48") comes in an 8 sheet pack for around $166.  You can make the tweeks (Hood and Lapels) out of one sheet, and use the other 7 as follows:

3 on the front wall (behind the speakers)
2 on the side walls (for side wall reflections
2 in the rear corners as bass traps (all you have to do really is just push them into the corners and they stay.

Actually through my connection I get "12 sheets" (4 more) for only $179, so that is what I ended up doing.

If you want the dozen, let me know (any of the colors listed on the site)

I mounted the stuff on the wall with long thumbtacks   So it wasn't any big deal.