Rear of cabinet resonance

OldmanSRS

Having read the Fun With Foam thread and how it reduces ringing, has anyone applied accoustic foam to the read of the SRS speaker cabinet? The back of the very large cabinet has some resonances that might be more audible than the baskets ringing. Just wondering since you guys seem to improve on everything.

hearingimpared

I wouldn't foam or Dynamat the cabinets. Spiking them will help rid you of the cabinet resonance.

Mye-sound spikes are the best!

https://myesound.com/Points_n_pads.html

nadams

How does spiking get rid of cabinet resonance?

I think what the OP needs to look into is adding more bracing to the cabinets.

hearingimpared

nadams wrote: »

How does spiking get rid of cabinet resonance?

I think what the OP needs to look into is adding more bracing to the cabinets.

It plants the cabinet firmly to the floor thus decoupling it from floor vibrations, if you can make sense of that. More bracing would be a good method too.

Face

Additional bracing may help.

skrol

I covered the interior of my RTA11TL's with a Dynamat like material and it does seem to reduce the cabinet resonance. I did not take measurements with an SPL meter but it was evident in the "Thunk Test" (tapping on the cabinet) and acoustically when I did an A-B comparison. I had also replaced some of the Daycron batting with foam behind the MW's.

Is there a down-side, other than cost, to covering the cabinet interior with Dynamat?

I had originally planned to improve the cabinet bracing (and may some day) but the Dynamat seemed to improve things enough for now.

I have also covered the interior of cheap unworthy speakers with "Peal And Seal" and have heard vast improvement in SQ.
Stan

hearingimpared

skrol wrote: »

I covered the interior of my RTA11TL's with a Dynamat like material and it does seem to reduce the cabinet resonance. I did not take measurements with an SPL meter but it was evident in the "Thunk Test" (tapping on the cabinet) and acoustically when I did an A-B comparison. I had also replaced some of the Daycron batting with foam behind the MW's.

Is there a down-side, other than cost, to covering the cabinet interior with Dynamat?

I had originally planned to improve the cabinet bracing (and may some day) but the Dynamat seemed to improve things enough for now.

I have also covered the interior of cheap unworthy speakers with "Peal And Seal" and have heard vast improvement in SQ.
Stan

Wow that is really interesting. What improvements or changes did you notice?

I always thought that Dynamating the inside walls of the cabinet would really make everything sound muddy and dead. I also thought that the speaker designer took the cabinet resonance into consideration in the manufacturing process.

I remember asking someone, maybe Jesse or Ken S., about Dynamating the inside walls of my 1.2TLs when I was doing my MW & PR baskets and got a resounding NO!

Sorry Jess or Ken if that wasn't you.

halo71

Both threads are interesting. Just the other night at work I was on some website where a dude was modding some old DCM TimeFrames (might have been TimeWindows don't remember now). But anyway, he had installed modeling clay inside the cabinet of the back panel. He even put the clay on the back of the baskets and magnets of the drivers!

I have never heard of anyone doing that.

OldmanSRS

The amount of resonance for such a large surface is really remarkably low meaning the cabinets are well made. Placing an ear next to the rear at moderate levels one hears tones in the 200-500 htz range at certain times. I was thnking more along the lines of using some velcro tabs to install a peice of 2" thick convoluted accoustic foam to the entire exterior rear of the cabinets and see what were the results, if any.

Face

I wouldn't use Dynamat for deadening a cabinet either.

Sonic Barrier: http://www.parts-express.com/wizards/searchResults.cfm?FTR=Cabinet_damping&search_type=main&WebPage_ID=3&searchFilter=Cabinet_damping&x=0&y=0

Blackhole 5: http://www.soniccraft.com/products/damping/blackhole5.htm

You can also add ribs to the inside of the cabinet. Here's a thread on that and other techniques: http://techtalk.parts-express.com/showthread.php?t=216067

By deading the cabinet, you're removing what's called box coloration. It shouldn't make the low end muddy, if anything it should improve the low end. But by overdamping the cabinet/enclosure, you can make it sound dead/lifeless though.

For a nice example of a dead cabinet: http://www.tidal-audio.de/english/startenglish.htm

kcoc321

Wow, where does one even GET 4" MDF?







They must special order it, or make it themselves.
Those things must weigh a TON

dorokusai

I've used Blackhole on some vintage Polk's....great stuff.

skrol

I am not sure why Dynamat would make the sound muddier. It seems that it would do the opposite. To be fair, the foam that I used is the Sonic Barrier and was added at the same time as the damping material to the cabinet and baskets. Therefore, it is the combination that I am really reporting. The lower mid-bass seems cleaner and more defined.

Before I started this project I consulted my friend who is a former Polk engineer from the late 80's - early 90's. He had no issue with adding the Dynamat and encouraged me to damp the baskets.

I follow the idea that the cabinet resonance can be part of the speaker design and add to its SQ properties. However, if adding Dynamat to the cabinet changes these properties, how much more would additional bracing?

When I added the Sonic Barrier and damping I borrowed a friends computer and mic with RTA software (SigView I believe). The spectral display showed that the cabinet still resonates with an impulse signal or tapping the cabinet. It just does not ring as long. My thinking is that the ringing / resonance is adding something to the music that probably should not be there (coloration?).

I am not looking to argue. I'm just stating my observations. It is certainly possible that I have gone wrong with damping the cabinet and I will respectfully ponder any advice. As all of us, I am always looking for ways to improve.

dorokusai

I wouldn't use Dynamat inside a loudspeaker since there are much better choices for that application as mentioned by Face. The stamped baskets sure but notthe actual cabinet.

kcoc321

Picture of the Tidal "dead speaker" Face refereed to.
I mistakenly deleted the pic before.
Some serious dampening

skrol

dorokusai wrote: »

I wouldn't use Dynamat inside a loudspeaker since there are much better choices for that application as mentioned by Face. The stamped baskets sure but notthe actual cabinet.

If I get a little extra spend money, and mainly time, I may try upgrading from the Dynamat. Actually, I am quite satisfied with the SQ of my RTA11TL's, for now anyway.

I thought about covering most of the interior with Sonic Barrier but was not sure if it was a good idea as it absorbs as well as damps cabinet vibrations.

On the opposite end if the spectrum from the Tidal "Dead Speaker" is the Onkyo D-TL10 which was designed in conjunction with Takamine (who make wonderful guitars). The idea is that the cabinet is built like a guitar where the cabinet is designed to resonate. Seems like a very novel idea.
http://www.onkyousa.com/model.cfm?m=D-TK10&class=Speaker&p=i

I wonder which sounds better?

dorokusai

I'm all for a little resonance control just don't overdo it and feel that's every panel has to be covered. A single piece is enough to let you know what the sonic impact will be, especially for a vintage loudspeaker.

I replaced the foam in my DQ10's with a single slab of Blackhole.

skrol

I'll probably leave well enough alone with the speakers. I really want to shift focus to upgrading my amplification.

OldmanSRS

Any mods done to the speaker might cause a change. The challenge is to make it a positive change. I don't think we have the data on hand that indicates how the designer took into account speaker enclosure or basket resonance when he designed the crossovers, and other things that influence the overal tone of the speaker as a complete system. At this point in time, it's trial and error when we seek an improvement.