GK MB115 and acoustic damping foam

blmeier7 · #1 01-02-2011, 10:25 AM

I've noticed that playing my MB115 at lower volume levels produces a very nice full sound but in a full band setting it starts to get a little boomy and looses some of it's tightness. I've heard of a couple of people adding the acoustic damping foam to this box but can't find any specifics after searching.

The internal bracing of the MB115 looks pretty good but it does not have any damping foam anywhere.

My question is: does anyone have any experience with adding damping foam to a cab and what to expect? Any suggestions will be helpful.

I did order some 1/2" acoustic damping foam that should arrive tomorrow. Basically I was going to apply it just like it is in my Genz Benz cab (back and side walls only).

billfitzmaurice · #2 01-02-2011, 10:36 AM

Quote:

Originally Posted by blmeier7

The internal bracing of the MB115 looks pretty good but it does not have any damping foam anywhere.

Unbelievable.

Quote:

My question is: does anyone have any experience with adding damping foam to a cab and what to expect? Any suggestions will be helpful.

Just opened up my 210MBE...

Quote:

I did order some 1/2" acoustic damping foam that should arrive tomorrow. Basically I was going to apply it just like it is in my Genz Benz cab (back and side walls only).

All of the interior should be lined, with the exception of near the entrance to ports and near crossover components.

Slowgypsy · #3 01-02-2011, 10:52 AM

Now I'm curious. GK makes good stuff. Is it written in stone that all interior sides of a cab should be lined... or is there a valid tech reason why this was not done on their cabs? And please don't say "to save money"... I'm looking for technical science based reasons why this wasn't done. Thanks....

blmeier7 · #4 01-02-2011, 04:12 PM

Thanks! That was the thread I was looking for.

So it seems there is about a 50/50 mix on those that think there should be damping foam and those that are on board with Bob Gallien's comment that the cab sounds great without it.

Since I already have the foam on order I'm going to give it a try and see how it sounds. If I like it better without the foam I can always take it back out.

Should I be concerned that the 1/2" foam on all interior walls will reduce the interior volume of the already small cab, or is this not an issue?

billfitzmaurice · #5 01-02-2011, 04:21 PM

Quote:

Originally Posted by Slowgypsy

I'm looking for technical science based reasons why this wasn't done.

If you want a cab to be boomy and have uneven midrange response, leave it bare. There's no technical reason to leave a cab undamped, only the economic one.

rpsands · #6 01-02-2011, 05:29 PM

The 50/50 mix is between "people who know what they are talking about" and "people who are playing devil's advocate because they don't know any better."

I am sorry if that sounds harsh but until you have set two cabs next to each other and played them lined and unlined, or read studies that describe the effects of lining, I don't think you should comment on it one way or the other. I have done both and would always line bass cabinets. Always.

craig.p · #7 01-03-2011, 06:27 AM

G-K amp electronics tend toward the dark+heavy side, frequency balance-wise, so maybe this is why it's possible to leave a G-K cab unlined and have the SYSTEM sound acceptable as a whole. If you line the inside of your cab, it will sound better at higher volumes, but in general it will have marginally less presence, and you may have to boost the mids a little. I did some experimentation in this area with a Peavey cab and an MB200, trying the cab both unlined (the factory way) and lined. Lined, the cab sounds a lot less "blatty" in the midrange, especially at high volumes, but it also sounds darker in general. I would never go back to unlined.

GRAHAM SG1 · #8 01-03-2011, 07:10 AM

I lined the back wall including the shelf for the amp (GKMB210) with 40mm accoustic egg crate foam and it has made some difference, it has tamed the boominess of the amp .
I wonder if the amp shelf protrusion inside the amp makes any difference to the sound as the sound waves are not hitting a totally flat surface, I wonder if they focus on the corner of the overhang where the shelf meets the back wall ?

tombowlus · #9 01-03-2011, 07:21 AM

Quote:

Originally Posted by Slowgypsy

Now I'm curious. GK makes good stuff. Is it written in stone that all interior sides of a cab should be lined... or is there a valid tech reason why this was not done on their cabs? And please don't say "to save money"... I'm looking for technical science based reasons why this wasn't done. Thanks....

I had a conversation with Bob Gallien about this very topic, and it most definitely was not done to save money (the increased cost of adding it would be inconsequential). Bob is aware of the impact of damping material inside of a speaker enclosure, and he and his crew did try a variety of materials. But when they playtested them, everyone thought that the undamped enclosures sounded better, so they left it out intentionally.

Please note, I am not saying that in any or all cases an undamped cab will sound better, nor am I saying that I subscribe to the theory that any or all cabs would sound better without damping material. I am merely passing on some comments I had from a discussion with Bob.

As many of you already know, Bob Gallien is a highly competent designer/engineer, and he is very passionate about his work. This was an intentional call on his part.

Tom.