Employing Damping to Mitigate Comb Filtering and lobing

rodman53

Hello all, new member here. Was reading an old post that was back in 2016 about Westmassguy's idea about employing damping to mitigate comb filtering and lobing. I was wondering if anyone has tried that to their monitor 10s? And if so did it help?

Voltz was starting to do it with his Monitor 10s, but i don't know what kind of results he got. I did'nt see where he got back with any comments about the mod. I would like to try it with mine if anyone has tried it with theirs and got good results.

Thank You

Gardenstater

@Jazzhead has done it and has made some comments on it very recently, if you take a look at his profile.

xschop

Hopefully he can post pics. He was also going to email them to take a look.

Jazzhead

@xschop I sent a message regarding mods to your private email address.

Here's the thread for the relevant mod (contains the only photos I have):

https://forum.polkaudio.com/discussion/196299/employing-damping-to-mitigate-comb-filtering-and-lobing

This mod works, although I've not done a sonic comparison with later RTA-12 models (with the rolled off driver). I've also not heard the results in a model 10 although theoretically, it should be effective. For me it improved imaging, enlarged soundstage, eliminated "shoutiness", and cleaned up midrange. Interestingly, beforehand there was was an audible "blip", void, dead space, in the soundstage "sweet spot" between my speakers - especially obvious if I played non-muted FM hash (the all-frequency static sound between stations). It was as if two images didn't want to merge. This "blip" totally disappeared after doing the mod. To be effective you have to go full-bore. Use the thickest Sonic Barrier/Black Hole 5 you can obtain. Extend the brace all the way to the bottom of the drivers, but not into the PR zone. Completely cover every surface of every side except the bottom. I also employed the same foam used in the @Gardenstater inner basket mod to cover the sides and back of the driver magnet. The goal is to soak up as much backwave as possible. @westmassguy understood (I learned this later) that this foam will soak up the upper-ish midrange frequencies and does not affect the bottom end which I found actually improved. Put the polyfill back behind the drivers, but in my case, my speakers had so much it would not all fit (I tried and it constricted air flow). Fit what you can without restricting air flow - keeping it out of the PR area. You can experiment with the amount until bass/SQ is optimized (trust your ears-think about live music you have heard). It's OK to have different amounts behind different drivers. Also, use a minimal amount of damping material behind the un-damped driver. I settled on a 4x4 inch piece. Originally I had a 4x5 piece, but removed part of it when I did the (very beneficial) inner basket foam mod. The goal is a sonic difference between the two drivers. One unintended sonic benefit of this mod (to my ears) is that having the damped brace between the drivers stops some side to side reflections that beforehand contributed to muddy midrange. This mod also helps a speaker retain composure at higher volumes. In a nutshell if you don't have the advanced crossover this is the best you can do.

rodman53

Thanks for your help guys!

Jazzhead

I posted the wrong link above... Try this one:

https://forum.polkaudio.com/discussion/173834/westmassguys-idea-employing-damping-to-mitigate-comb-filtering-and-lobing

rodman53

Thanks Jazzhead!

xschop

Maybe WMG can answer, but my question was going to be if extending the middle brace all the way down to the PR, but not adding dampening to the extra length, would this affect the driver's midrange? I know doing this would improve mid-bass by stiffening baffle as much as possible.

rodman53

That's a good question xschop. Where's that computer program so we can punch in these different parameters? lol

Jazzhead

I've not mentioned that extending the brace down between the dual drivers on my 12's totally eliminated a good bit of vibration I could feel in that area. There's not a lot of meat to the baffle there. I would imagine that could affect SQ. There's yet another benefit to doing westmassguy's mod. My speakers have nice midrange clarity.

rodman53

Midrange clarity with the 10s would be a big help.

Jazzhead

If you are so inclined, do this mod, do Gardenstater's foam inside the driver baskets, and the other standard mods outlined on the forum (Dynamat on outer driver baskets, seal the cabinet interior/air leak test, crossover upgrades) and you should have plenty of midrange clarity and other sonic improvements. In case you aren't aware, be sure to epoxy your driver magnets (search the forum). Vintage driver adhesive can/will fail and it would be unfortunate to spend time and effort doing mods and then have a magnet shift. There are plenty of other tweaks and upgrades further down the Rabbit Hole (lol).

westmassguy

xschop wrote: »

Maybe WMG can answer, but my question was going to be if extending the middle brace all the way down to the PR, but not adding dampening to the extra length, would this affect the driver's midrange? I know doing this would improve mid-bass by stiffening baffle as much as possible.

It would add stiffness to the front baffle. This should help reduce any sympathetic movement tied to the woofers frequency range.

rodman53

Thank you WMG! Sounds like i will be trying this in the near future.

rodman53

Thanks Jazzhead