Placement options – Impacts of location, orientation and treatments

MartinLogan Audio Owners Forum

Help Support MartinLogan Audio Owners Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
For those of us looking for a "ONE BOX" room/frequency response measurement tool, perhaps this new PC-based product will be the answer! Just saw this announcement on Enjoy The Music. It is slated for release in Jan, price?? Full product link here... http://www.xtz.se/produkt.php?allmant=true&mer=true&produkt=41&eng=true

I hope they put more time and effort into their product design than they did into proofreading their web page. I have never seen so many grammatical errors on a product website. Doesn't give me a warm fuzzy for the professionalism of the company or its products.
 
I have never seen so many grammatical errors on a product website. Doesn't give me a warm fuzzy for the professionalism of the company or its products.

LOL, that's what I think when I go to a software company's web site. Spelling is critical with computer programming! :D

--Ethan
 
Well, they're apparently a Swedish company, so I suppose we can cut them a little slack as English is not their native language. Anybody familiar with any of their other products?
 
Well, they're apparently a Swedish company, so I suppose we can cut them a little slack as English is not their native language. Anybody familiar with any of their other products?

Usually the Europeans have intimidatingly good English - I had thought it was a Chinese company on the basis of the blurb.

I am interested in this product too - wonder if they will be doing direct sales over the internet.

Kevin
 
Well, upon closer reading, they indeed appear to be a Chinese sourced, internet direct, company. I guess time will tell if they have decent engineering and support.
 
Hmmm - I will wait then. Some good stuff out of China but an awful lot of rubbish.

Kevin
 
First Drop arrived!

Yesterday (Saturday) FedEx pulls up at 5pm and starts to unload a literal truckload of boxes. And this is a partial order delivery, as about eight other pieces were shipped separately (and arrive the 2nd).

So, guess what I've been doing all day ;)

I got the bare room measurements done. A process that took hours, as I had to take down most of the old stuff, and do measurements at many positions.

Then I started placing a few RealTraps for testing, primarily a test of a MondoTrap vs a MinITrap HF behind the center. I'll post measurements in the morning. But the summary is: you really want the HF versions behind the speakers. The reflective elements in the regular traps cause a nasty reflection spike noted in the measurements of a bare wall. The HF versions are nice and smooth.

I later got all four minitrap HF's installed behind the screen area and the center speaker. I then added a Mondo Trap horizontally across the top of the screen over the center (and that big IB sub) to help with bass absorption under the front soffit. Still not convinced about that one. More measurements to substantiate a sense I have.

But the four MiniTraps are doing wonders for the front soundstage at this point. The clarity of vocals in the center is noticeably improved.

Also helping are two Large Mondo Traps in the rear of the room.

But that's only half the stuff I got. So more placements, installation and testing over the next two days.
 
Hi Jon,

When you get a chance could you post some of your thoughts regarding the choice of Ethan's Realtraps to treat your room. Clearly you have some confidence in the product/Ethan to have ordered the proverbial truckload.

I will be fascinated to hear your impressions and measurements.

Kevin
 
Hi Jon,

When you get a chance could you post some of your thoughts regarding the choice of Ethan's Realtraps to treat your room. Clearly you have some confidence in the product/Ethan to have ordered the proverbial truckload.

I will be fascinated to hear your impressions and measurements.

Kevin

Hi Kevin,

My choice was predicated on two things: One, that Ethan is an active and open member on many acoustics related forums. He readily shares his knowledge and helps those who want to DIY.
In so doing, he's demonstrated his understanding and abilities, as well as his character. I value both.
Secondly, the products have been tested and reviewed very well. Members like Rich give them high praise.

Now that I have some to see, feel and test myself, I concur that they are excellent products. The build quality is very good, and as we will see, they are quite effective.

The RealTraps use a lightweight metal (I assume Alu) frame to provide the box. This give them a much smaller profile than products made with wood or other materials, and also make them lighter.
The mounting options are very good and they provide all the necessary hardware.
I was even impressed with the packaging and shipping, all first rate.

It was a bit of a leap of faith to spend $7K on products I’ve never tried, but the results so far are substantiating the decision.
 
Last edited:
Are you having fun yet, Jon? :D:D:D

Well, hanging them was not so much fun, as I'm mostly thumbs when it comes to hammers and nails, but the wife helped out in critical points ;)

The rest of it has been very intersting, and yes, Fun :cool:

So here comes some real info, the measurements.
 
Here are the main listening position measurements.

All of these are taken by playing signals through my custom center. By using the Center, it will show more of the effects of the room tuning overall (especially since the bare wall behind the center is so detrimental).

Note that these will show the room effects the most. Later on, I’ll post 1 meter measurements of the center where we will better see the vast improvements the treatments have.

These measurements show the effects of only placing 4 MiniTrap HF’s behind the center channel and the screen area. I also placed a MondoTrap horizontally over the center area. See pics later on for what it looks like.

So here’s the Impulse response of the treated (red) vs Untreated (blue) from our listening position at 6 meters.

Important items to note:
  • Almost total cancellation of rear wall bounce via the MiniTraps HF (HF’s absorb more high frequencies)
  • The MondoTrap (which does have a reflective diaphragm element) seems to have contributed to increasing the strength of a spike in the vertical dimension.
  • - I’ll have to re-test without to confirm
  • In general, even waay out in the room, the response is indeed smoother.
 

Attachments

  • ImpulseResponse - BeforeAfter - Phase1.jpg
    ImpulseResponse - BeforeAfter - Phase1.jpg
    98.3 KB · Views: 447
Here is the Bode response of the room at 6m.

Pretty ragged as there are lots of room modes and resonances.

It’s these resonances that we will be trying to tame with the traps. Right now, there really are not enough traps installed to really affect the major room modes and resonances, but it does help.

Here is the comparison between treated (Red) and untreated.

Note that the treated state is improved, while still showing the same major room modes.
 

Attachments

  • Bode - BeforeAfter - Phase1.jpg
    Bode - BeforeAfter - Phase1.jpg
    94.7 KB · Views: 462
Last edited:
Next up are the waterfall plots, as these clearly show what room resonances do to the sound over time.

Ideally, one wants a rapid decay across the board. However, that only happens in an anechoic chamber, as most rooms impart their own ‘sound’ via modes and resonances.
A resonance is when a given frequency does not decay rapidly, or in some cases, increases in level over time as the room reverberation across the three axes reinforce each other.

My primary listening position is far from ideal in this room, as it is a large null at around 100hz, plus it seems to be reverb central without the treatments.

In this shot of the untreated room, note the long decay times (from resonances) pretty much across the board. Not good.
 

Attachments

  • Waterfall - Untreated BeforeAfter - Phase1.jpg
    Waterfall - Untreated BeforeAfter - Phase1.jpg
    139.7 KB · Views: 447
In this shot of the treated room, note some of the decays are shorter and the peaks in the response shallower.
Much better, but we still have a lot of resonances to deal with at the listening position.
 

Attachments

  • Waterfall - Treated BeforeAfter - Phase1.jpg
    Waterfall - Treated BeforeAfter - Phase1.jpg
    133.6 KB · Views: 446
Finally, a Psychoacoustic frequency response plot comparing the before and after state.

Not much change, but what is there is for the better.

Fundamentally, what many treatments do is fix time-domain resonances, (which impinge on frequency response). This is why treatments are more important than EQ, as no EQ can fix the in-room decay problems.
 

Attachments

  • PsychoAcoustic - BeforeAfter Phase1.jpg
    PsychoAcoustic - BeforeAfter Phase1.jpg
    82.8 KB · Views: 479
Now that we’ve looked at the listening position, time for a close-up of the speaker at 1 meter.

This will tell us more about the net effect of the treatments on the sound emanating from the speaker with fewer room modes and resonances affecting it. Therefore these results are more immediately transferable to your situation (assuming a similar config in terms of distance from wall).

First, the impulse response.

Here again we see the nasty effect of a bare wall behind a dipole ESL. That big spike at 4ms totally messes the time-domain of the unit. It must be treated.
Fortunately, the MiniTrap HF does a great job of that as we can see. The spike is pretty much gone.

While the trace is still a bit ragged due to being behind a screen, the treated trace is much cleaner.
 

Attachments

  • Inpulse - BeforeAfter - Phase1 1m.jpg
    Inpulse - BeforeAfter - Phase1 1m.jpg
    77.7 KB · Views: 475
In this Bode response, we can see that the treated surfaces behind the entire screen and center channel really help smooth out the variances in frequency response.
 

Attachments

  • Bode - BeforeAfter - Phase1 1m.jpg
    Bode - BeforeAfter - Phase1 1m.jpg
    86.3 KB · Views: 502
And here is the real critical difference, the time-domain now visible in this pair of waterfall plots.

The top plot is the before treatment. Note the long decays in the mid frequencies and how they will even increase in level.

The bottom plot is the treated surface, at 1m from the speaker. Note the quick decay across the board in the mid to high frequencies.
There are still a few resonances left, but no where near what was there before.

The low frequencies are still dominated by other room modes, although even those are slightly improved.

From these two plots, it should be fairly clear that treating the surface behind the speakers is critical.
 

Attachments

  • Waterfall - Untreated BeforeAfter - Phase1 1m.jpg
    Waterfall - Untreated BeforeAfter - Phase1 1m.jpg
    144.2 KB · Views: 443
  • Waterfall - Treated BeforeAfter - Phase1 1m.jpg
    Waterfall - Treated BeforeAfter - Phase1 1m.jpg
    141 KB · Views: 455
Back
Top