Zaph ZA5 in-wall MTM build - diyAudio
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Old 29th September 2014, 12:24 AM   #1
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Default Zaph ZA5 in-wall MTM build

Built a Left, Right, and Center channel of the ZA5 In-Wall MTMs for my living room using the Madisound kit (pre-assembled crossover) and Parts Express in-wall baffles. I put 1" of "Sonic Barrier" foam behind them and stuffed tightly rolled up pink insulation above and below them. I have to say, I'm unfortunately having some issues. They sound very.... boxy? Male voices can sound very honky. I tried to capture this by performing some measurements, but I'm not able to interpret anything useful out them. I really don't think the issue is with the design and I'm thinking that the crossovers were probably properly assembled by Madisound. I shudder to think I just could have wired them up wrong. I check that and I believe they are wired correctly. Wall cavity resonances? Room acoustical problems? Any ideas or advice?

First Picture: Shows speaker placements
Second Picture: Gated frequency response 1m from tweeter
Third Picture: Step response 1m from tweeter
Fourth Picture: Ungated frequency response at listening position
Fifth Picture: Step response at listening position
Sixth Picture: Ungated frequency response 1m from tweeter
Seventh Picture: "Pink Noise" RTA response 1m from tweeter
Eighth Picture: Impulse response 1m from tweeter
Attached Images
File Type: jpg IMG_0079.jpg (483.0 KB, 142 views)
File Type: jpg gated_FR.jpg (152.4 KB, 135 views)
File Type: jpg step_response.jpg (229.9 KB, 120 views)
File Type: jpg ungated_1_3_oct_FR_at_Listening_Position.jpg (161.4 KB, 112 views)
File Type: jpg step_response_w_sub_at_Listening_Position.jpg (221.8 KB, 108 views)
File Type: jpg ungated_FR.jpg (169.9 KB, 26 views)
File Type: jpg FR_Pink_Noise.jpg (218.4 KB, 29 views)
File Type: jpg impulse_response.jpg (159.0 KB, 26 views)

Last edited by wigginjs; 29th September 2014 at 12:53 AM.
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Old 29th September 2014, 07:51 AM   #2
Lojzek is offline Lojzek  Croatia
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Hi wigginjs,

The quote is from 2nd paragraph of ZA5.2iw

Zaph|Audio - ZA5 Speaker Designs with ZA14W08 woofer and Vifa DQ25SC16-04 tweeter

"There are however a different set of issues to be aware of with
typical in-wall installations. For starters, drywall does not make a
good baffle and wood is recommended. Enclosure rigidity is as
important as it is in a box design, however in-wall it is magnitudes
harder to have a rigid and non-resonant enclosure. For this reason,
I would really only recommend the in-wall design in new buildings.
That way the enclosure can be properly stiffened and damped as the
wall is built."

Maybe this has something to do with you experiencing honky sound.
Try making an impedance measurement with ARTA and if there are any
undamped cavity resonances, they would show up in the plot.
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Old 4th October 2014, 04:17 AM   #3
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I'd also agree-post an impedance plot, let's see.

What is the mounting? That is to say, what is the distance to the ceiling and to side walls? And what is the vertical angle vs. listening position? Does it still sound honky if you are standing up? I'm wondering if you are in an off-axis response lobe, causing a peak.


In-wall is nice in that it removes a set of reflections, but the "enclosure" is truly problematic
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Old 5th October 2014, 10:09 AM   #4
ODougbo is offline ODougbo  United States
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Wigginjs,

Basically you have the same set up as me with MTM's in the HT.

First question is obvious, can you go back and build boxes and use stands for the front three? [repair/paint walls]
As mentioned, with the MTM's, you'll need to be ear level with the center of the speakers; that's an easy test, just slide furniture out of the way and see if you can find a sweet spot.
I'm loving our MTM's here, although there is a noticeable change in the sound when sitting off to the side; dead center is really nice though.
(my center is on a stand, about 5 degree tilt)

That's a beautiful room but a lot of hard surfaces, see about damping the room with rugs, etc.

One other simple test, simply hook up two of the speakers to a stereo receiver/ CD - see if the sound/tone improves.
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Old 5th October 2014, 11:25 AM   #5
Lojzek is offline Lojzek  Croatia
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I would suggest, if proven to be the issue, to damp the wall surface
with bitumen pads from the side whatever more practical. If I were
in OP's shoes, I would try to damp from the inside in the way that
the whole part of the speaker baffle with the surrounding dry wall
be cut out, damped with a couple of layers and then installed back.

It could be fastened to pieces of timber which would serve as a
supporting frame and leave a seam to the rest of the drywall and
seal it off with silicone caulk and leave some space for the finishing
plaster. I don't know if that makes much sense.
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Old 5th October 2014, 12:11 PM   #6
spekr is offline spekr  United States
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Quote:
Originally Posted by wigginjs View Post
Built a Left, Right, and Center channel of the ZA5 In-Wall MTMs for my living room using the Madisound kit (pre-assembled crossover) and Parts Express in-wall baffles. I put 1" of "Sonic Barrier" foam behind them and stuffed tightly rolled up pink insulation above and below them. I have to say, I'm unfortunately having some issues. They sound very.... boxy? Male voices can sound very honky. I tried to capture this by performing some measurements, but I'm not able to interpret anything useful out them. I really don't think the issue is with the design and I'm thinking that the crossovers were probably properly assembled by Madisound. I shudder to think I just could have wired them up wrong. I check that and I believe they are wired correctly. Wall cavity resonances? Room acoustical problems? Any ideas or advice?

First Picture: Shows speaker placements
Second Picture: Gated frequency response 1m from tweeter
Third Picture: Step response 1m from tweeter
Fourth Picture: Ungated frequency response at listening position
Fifth Picture: Step response at listening position
Sixth Picture: Ungated frequency response 1m from tweeter
Seventh Picture: "Pink Noise" RTA response 1m from tweeter
Eighth Picture: Impulse response 1m from tweeter
Something's wrong.
Is your mic calibrated?
Looking at the gated response: The response falls off at 8kHz. It shouldn't. The wide peak between 2-3kHz would explain the "boxy" sound. How long is the gate by the way?
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Old 5th October 2014, 01:29 PM   #7
Lojzek is offline Lojzek  Croatia
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The 500 Hz resonance from pictures 4 and 5 looks suspicious to me.
A cavity of 0,34 m would cause such a standing wave.
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