Fabulous Free Factory-Authorized Tweak!

jakepunk · « **Reply #40 on:** 15 May 2004, 11:50 pm »

I tweaked my Tower II PRs last night. I used Elmers "contractor grade" wood glue (oooo... ahhhh) because that's what I had on my workbench. I coated both sides, and I let it dry for about 16 hours. The bass is certainly richer, deeper, and fuller now. "Thunderous" would be the best way to describe it. I had to remove a significant amount of Mortite putty to prevent the new sound from sounding too "boomy".

Editorial: This tweak will significantly change the low-end sound of your speakers. If you like lean, tight bass then this tweak may not be for you. I like my bass to contribute to the overall sound but not overpower the other instruments. My new bass is now a prominent component of the overall sound whereas before it was merely the foundation. I am not a Big Bass kind of guy. It will take some getting used to.

Brian Cheney · « **Reply #41 on:** 16 May 2004, 01:36 am »

Paint the entire paper part of the cone with Elmer's; avoid the foam and the spider supporting the cone apex.

ekovalsky · « **Reply #42 on:** 16 May 2004, 01:56 am »

In case anyone didn't know, the "spider" is the circular, spongy brownish thing on the rear of the driver which limits the excursion of the woofer cone itself. If you don't remove the driver from the cabinet and only paint the outer face, you won't see it and don't have to worry about it.

Putty is tough to figure out... I have found it is not always a simple relationship with more putty = tighter bass. Too much can make the speaker sound a bit "constipated" as can too little. The glue solids probably end up weighing as much as a marble-sized piece of putty, particularly if both sides of the driver are painted. But mass applied at the apex of the driver may not have the same effect as mass applied to the entire surface of the cone. Also, by altering the physical properties of the driver itself, i.e. stiffening the diaphgragm, the effect of a given mass load would change.

Lots of variables are at work here! Brian, about how much putty are you removing (or adding) to compensate for the glue treatment ?

Zybar, have you done this yet?

tkp · « **Reply #43 on:** 16 May 2004, 02:55 am »

I painted the PR last night on both sides and performed tuning/listenning this afternoon. The bottom octave bass improved is there but there is no improvement on the midbass (I did not expect any considering the PR for frequency below 80Hz).

The scary thing is that I did not have to remove any additional putty at all. When I tried to remove a little bit of putty, I ended up with thinning the midbass. When I tried to add more putty, I ended up muddying the midrange.

One thing I ended up doing was that I put a 12" x 12" piece of marble tile on top of each speakers and let the tile extended beyond the face of the cabinet any where from 4" to 5". I put three marking lines on the tile: 4.0", 4.5" and 5". Depending on recording I moved the tile in and out. I got a pretty balanced sound (with decent midbass) and the cool thing is I can taylor the sound via this method without playing with putty or the pots. This was described by John Casler awhile back but I did not try it until now.

I plan to build two long piece of black marble tile with dimension of 22" x 12". This will allow the initial stick out position to be 4" (which I found to be the mininum I need) and I can move the tile out further depending on recording.

The above might have to do with the room the speakers are in. This room is basically the entire first floor of my 2400 squared foot house with 9 ft ceiling and tile flooring. Prior to painting the PR with Elmer glue, the RM40s were having difficult time putting out good bass in this room/floor.

John Casler · « **Reply #44 on:** 16 May 2004, 04:23 am »

Quote

One thing I ended up doing was that I put a 12" x 12" piece of marble tile on top of each speakers and let the tile extended beyond the face of the cabinet any where from 4" to 5". I put three marking lines on the tile: 4.0", 4.5" and 5". Depending on recording I moved the tile in and out. I got a pretty balanced sound (with decent midbass) and the cool thing is I can taylor the sound via this method without playing with putty or the pots. This was described by John Casler awhile back but I did not try it until now.

TKP,

Now you have the low bass and the upper bass tweaks down

They sure can make the RM40 even better.

The "Sonic Director" and the "PR Stiffner" (is that a word?)

tkp · « **Reply #45 on:** 16 May 2004, 04:35 am »

I think BC should offer some kinda matching veneer hood to put on top of the RM40 allowing this adjustment and at the same time decorating friendly. As for me, I will have to choose between MDF board or marble tile. I am leaning toward marble tile because the floor of my house is tile so this would balance between the top and bottom woofers.

Bob Wilcox · « **Reply #46 on:** 16 May 2004, 01:25 pm »

It is interesting to read the variety of effects reported from this mod. Thursday night I glue-painted the passive radiators on both sides. I have my RM-40s in a smallish room (13 x 15) with 4 RealTraps which greatly improve the ability to hear the bass through lower midrange articulation. I also previously did the woofer position swap.

What I hear with this mod is a general tightening of bass reponse with an improved focus and a little more punch in the lowest octave. Overall, my RM-40s have a leaner sound with improved deep bass. I believe some midbass peak might have been tamed a little but I need to replot room response to be sure. I would not rule out eventually lowering the level pots slightly but I will wait to see if the PRs will 'break in' as new drivers would through flexing. Also I may experiment with restoring the factory woofer positions. At this point the effect of putty adjustment seems much more subtle.

BTW, recordings that have overmodulated bass or where the studio bass amp speaker was doubling will stand out more. The RM-40s were the first speakers I have owned where some problems in the recording studio faked me out to think the was a problem with with my speaker. I have a remastered Byrds CD where some studio monitor output is mixed into a track and it is now clear that one of the studio monitor drivers was trashed. A first I thought it was an RM-40 problem.

zybar · « **Reply #47 on:** 16 May 2004, 02:37 pm »

Eric,

I haven't done the job yet (I do have the glue and brush).

Hopefully I will get to it in the next few days.

George

ekovalsky · « **Reply #48 on:** 16 May 2004, 04:26 pm »

Quote

wait to see if the PRs will 'break in' as new drivers would through flexing

I think new woofer 'break in' is mainly from stress effect on the rubber surrounds, which are stiff when new and become more supple with use. Unless the surrounds got glued

, there probably won't be much further change in the sound of the modified driver once the paper and glue "vitrify" (borrowing Big B's term here).

If you want to see some serious vitrification take a trip to the Trinity Site in New Mexico and check out what once was sand

pjchappy · « **Reply #49 on:** 16 May 2004, 05:33 pm »

Quote from: ekovalsky

Quote
If you want to see some serious vitrification take a trip to the Trinity Site in New Mexico and check out what once was sand

That's not still radioactive?

Brian,

I have a question about my sub. . .when I push in a driver, should the other driver stay out, or will it SLOWLY go back in? Mine slowly goes back. . .does this mean I have an air leak?

p

Brian Cheney · « **Reply #50 on:** 16 May 2004, 05:55 pm »

No leak. The air pressure slowly equalizes and the cone returns to its rest position.

pjchappy · « **Reply #51 on:** 16 May 2004, 06:23 pm »

Thanks B!

p

Marbles · « **Reply #52 on:** 16 May 2004, 09:09 pm »

Quote from: tkp

I plan to build two long piece of black marble tile with dimension of 22" x 12". This will allow the initial stick out position to be 4" (which I found to be the mininum I need) and I can move the tile out further depending on recording.
...

TKP, how do you plan to do this? Will you cut two pieces of 12" X 12" down to 10 X 12 then "glue" them to 12" x 12"?

What bonding material will you use? How will you cut the marble?

Thanks..I tried using ceramic marble tile today (12" x 12") and liked the results.

tkp · « **Reply #53 on:** 16 May 2004, 11:20 pm »

[quote="Marbles
TKP, how do you plan to do this? Will you cut two pieces of 12" X 12" down to 10 X 12 then "glue" them to 12" x 12"?

What bonding material will you use? How will you cut the marble?

Thanks..I tried using ceramic marble tile today (12" x 12") and liked the results.[/quote]

Marbles,

The only reason I decided to use marble tile is because a friend of mine own a tile bussiness so I can get odd pieces of marble tile for free. It might have worked out better because of the tile flooring of my house.

Any way, for each speaker I plan to cut two pieces of 10" x 12" tile plus two pieces of 12" x 12" tile and glue them over lapping each other. The bottom side will start with 10" x 12" and the top side will start with 12" x 12". I found out a long time ago that general glue at HomeDepot works great. I forgot the brand but I will recognize it when I see it at HomeDepot. I also plan to paint the edge with permanent blacker (black color). With black marble tile + painting the edges with black permanent marker will match the black finish of my pair of RM40s.

zybar · « **Reply #54 on:** 16 May 2004, 11:48 pm »

Is marble better than MDF?

I have heard that marble can ring.

George

Marbles · « **Reply #55 on:** 16 May 2004, 11:50 pm »

TKP ...Thanks...that makes a lot of sense...

zybar · « **Reply #56 on:** 16 May 2004, 11:51 pm »

Just "painted" both sides of my PR's from the two Larger subs.

As I want to use the speakers tonight, I won't do the 40's until tomorrow night (or maybe late tonight).

Will post some pics later.

George

tkp · « **Reply #57 on:** 16 May 2004, 11:54 pm »

Quote from: zybar

Is marble better than MDF?

I have heard that marble can ring.

George

I don't know which one is better. The only reason I used the marble tile is because I have few in the garage. One can experiment to see which one is best. Currently, I am considering:

a) Black marble/Granite cutting board
b) marble tile
c) MDF

I am learning toward black mable/granite cutting boards because if I decide not to play with this in the future then I can use them for the kitchen

.

MDF is also a nice choice but granite might have the weight advantage for the same thickness.

Marbles · « **Reply #58 on:** 17 May 2004, 12:00 am »

I have a friend who has a cabinet business, so I'm thinking of maybe having him make me some oak veneered mdf that I could paint to match the black oak speaker.

If I do that I was wondering if it would make sense for it to be in a 90 degree shape with a sonic director on the side as well as on top?

Maybe it would make sense to do both sides and the top? Has anyone tried this?

zybar · « **Reply #59 on:** 17 May 2004, 03:57 am »

Ok, couldn't wait till tomorrow to do the 40's. They are painted and they will dry until I put them after work tomorrow.

Pics will be posted sometime tomorrow.

George