Martin Logans and room acoustics

werd · « **on:** 23 Apr 2011, 06:21 pm »

Due to the speaker technology are ML's less dependant on room acoustics? I understand how conventional driver technology can benefit from treatments but are the same principles at play with ML technology? Do you even need room treatments?. I understand speaker placement and tilt is still a factor but what about dampening or comb filtering, are room treatments needed with ML speakers?

jtwrace · « **Reply #1 on:** 23 Apr 2011, 06:31 pm »

No. I've owned three pairs of ML's and they all required many hours of setup to get them right. Room treatments were a huge part of that.

bpape · « **Reply #2 on:** 23 Apr 2011, 07:59 pm »

Decay time control in the bass is still key. For any type of panel speaker, you also need to address comb filtering of the back wave. Usually, diffusion behind the panels is the best option.

Bryan

werd · « **Reply #3 on:** 23 Apr 2011, 08:14 pm »

Thanks....

BobC · « **Reply #4 on:** 23 Apr 2011, 09:04 pm »

Anyone have some links to good DIY Diffusion to locate behind ML panels?

DTB300 · « **Reply #5 on:** 24 Apr 2011, 05:22 pm »

Quote from: BobC on 23 Apr 2011, 09:04 pm

Anyone have some links to good DIY Diffusion to locate behind ML panels?

Not DIY, but GIK now has some very reasonably priced diffusors.

FYI, in my room and for my rig, I preferred absorption on front wall behind my ML's and diffusors on the rear wall (behind seating)

sleepysurf · « **Reply #6 on:** 24 Apr 2011, 11:21 pm »

Here's the custom solution I devised for my ML Summits... "acoustic bookshelves" (including built-in bass traps)...
http://www.martinloganowners.com/forum/showthread.php?t=7551

dlaloum · « **Reply #7 on:** 25 Apr 2011, 08:04 am »

Yes but panels have one advantage seldom mentioned...

They are relatively insensitive to side walls - you can place them close to side walls with minimal issues....

But you have to give them space behind and sometimes treat the wall behind them.... so swings and roundabouts.

I think the side wall thing makes them a lot easier to locate than most "boxes"...

bye for now

David

BobC · « **Reply #8 on:** 29 Apr 2011, 01:45 pm »

So I found the QRDude program for diffusion panel design. Got to admit I don't know what I'm doing.

Questions:

It looks like the number of wells determines the high frequency cut off. So the more wells the higher the frequency. I assume the "diffusion" take place above the cut off, correct? With my ML Ascent i's the cross over between the woofer and panel is 280 hz, which is much lower than the QRD. So how do I select a cut off frequency and therefore determine the number of wells? I'm guessing it's room dependent - but I'm not in a position to take a bunch or high tech measurements. Is there some sort of rule-of-thumb?

Also, given this is a cross-section profile, I assume I can make the panel as long as I want, correct?

Thanks!

BobC · « **Reply #9 on:** 5 May 2011, 12:08 pm »

bump please

bpape · « **Reply #10 on:** 5 May 2011, 01:30 pm »

In general, max depth determines low frequency cutoff. Well width controls high frequency cutoff. As the number of wells increases, generally the diffusion becomes more uniform.

Just understand that for placement purposes, the lower the frequency, the farther you need to sit away from it to allow it to develop fully. The length parallel with the wells can be whatever you want.

Bryan

BobC · « **Reply #11 on:** 5 May 2011, 04:46 pm »

OK, so 13 wells are better than 7. The deeper the better. Is there something magic about the numbers 7 or 13? Because that's what I see commonly available online.

Voncarlos · « **Reply #12 on:** 5 May 2011, 06:19 pm »

They are Prime Numbers, which, in mathematics are considered magical !!!

Quote from: BobC on 5 May 2011, 04:46 pm

OK, so 13 wells are better than 7. The deeper the better. Is there something magic about the numbers 7 or 13? Because that's what I see commonly available online.

bpape · « **Reply #13 on:** 5 May 2011, 06:25 pm »

Deeper is lower - not necessarily better. You also have to look at the relationship between well width and well depth. The tool has a function that lets you evaluate the design to show you what works and what you shouldn't do.

Bryan

Nyal Mellor · « **Reply #14 on:** 9 May 2011, 04:39 pm »

Take a look at the Planar / Dipole FAQ thread for some useful insights: http://www.whatsbestforum.com/showthread.php?3274-Planer-Dipole-speakers-FAQ&p=50287

Dipoles are no different than other speakers in requiring room treatment to sound their best. Their radiation pattern, however, is significantly different than a box speaker and they also interact differently with room modes. Both of these factors need to be taken into account when designing a room's acoustic treatment.

bpape · « **Reply #15 on:** 19 May 2011, 07:45 pm »

Except for hybrids like most of the ML's which mate a panel to a dynamic woofer which still has the same boundary interaction issues. Most of the lower harmonics of the room modes will be where the woofer is operating. I don't know where ML crosses to the panels but I would guess 100-200Hz.

Bryan

Nyal Mellor · « **Reply #16 on:** 21 May 2011, 02:40 am »

The higher end MLs use a very interesting woofer configuration where the two drivers are acting as a monopole low down and then transition to a dipole before crossing over to the panel. The transition from monopole to dipole is done by applying phase shift to one of the drivers. A very cool technique.

I believe even on the Summit they are using 270Hz or so as the xo point.

TONEPUB · « **Reply #17 on:** 21 May 2011, 03:15 am »

Another vote for GIK panels. We've had excellent luck with their stuff!

bdiament · « **Reply #18 on:** 24 May 2011, 06:34 pm »

Hi werd,

Quote from: werd on 23 Apr 2011, 06:21 pm

Due to the speaker technology are ML's less dependant on room acoustics? I understand how conventional driver technology can benefit from treatments but are the same principles at play with ML technology? Do you even need room treatments?. I understand speaker placement and tilt is still a factor but what about dampening or comb filtering, are room treatments needed with ML speakers?

Since every room has a fundamental resonance and its harmonics (for each of the three dimensions), every room requires these be addressed if one is to optimize playback in that room.

And every room (outside of a padded cell ;-}) will have reflection points (one for each speaker, per room boundary). These too need to be addressed for optimal playback.

What Martin Logans and other dipolar radiators have in common is that they tend to excite the room primarily in the front-to-back dimension. Planars will radiate very little energy to the sides or vertically.

This does not obviate the need for treatment but it does mean there is less room excitation in the side to side and vertical planes - with planars or with the planar section of MLs. However, since most of their models use quasi-omni monopole (i.e. box) bass, this puts those ML models in the same place as full-range quasi-omni monopoles in that all three dimensions will be excited.

Hope this helps.

Best regards,
Barry
www.soundkeeperrecordings.com
www.barrydiamentaudio.com

rollo · « **Reply #19 on:** 24 May 2011, 06:50 pm »

Quote from: BobC on 23 Apr 2011, 09:04 pm

Anyone have some links to good DIY Diffusion to locate behind ML panels?

Cheap enough are PI audio Groups Difussors. You can buy the unfinished ones and finish to your hearts content. Check out his site here in the Manf. Circle.

charles