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post #1 of 8 Old 11-07-2019, 06:18 PM - Thread Starter
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DIY Soundgroup Build Issue

Alright guys I need some help. I'm having an issue with the response on some Helix Dome MTMs I built, and I'm not sure what is wrong. This is my first speaker build, so I'm not very versed on trouble shooting.

I'm thinking the roll-off on the low end could be overstuffing/blockage of ports, but the 6 db rise up top has me for a loop....or is all this because I am awful at soldering?

Note -- Response is in a shoe box of a room, using a UMIK and the 9 placement response.

Any help would be greatly appreciated.
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post #2 of 8 Old 11-07-2019, 06:25 PM
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post all available info about the room and placement of everything

and build pics

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post #3 of 8 Old 11-07-2019, 06:38 PM - Thread Starter
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Room set-up is odd to say the least. They are on the long wall of a rectangular room that is ~8' x 12' and are touching the TV and about a foot off the back wall...I don't have the room to move them at the moment.

Powered by an Outlaw 976 to Mini-DSP 88A/BM to Outlaw 7000x
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Last edited by Darrel Drake; 11-07-2019 at 06:41 PM. Reason: It didn't like my pictures...
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post #4 of 8 Old 11-07-2019, 06:42 PM
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Is that polyfill covering the port opening inside the box? If so, that would be a problem.

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post #5 of 8 Old 11-07-2019, 08:58 PM
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The rise above 2k certainly isn't correct. The drop below 250 could be placement/room/SBIR rather then an issue with the speaker. 1/4 wavelength at 150hz is ~22.5" so if the front of the baffles are around that distance from the wall that would be why you see a cancellation in that range.

Can you take a measurement with the mic placed about 1.5-2' in front of just one speaker centered on the tweeter? Even better pull the speaker out into the room and place it on a chair or stool to do this.

You are using the miniDSP to take the measurements correct?
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post #6 of 8 Old 11-07-2019, 09:56 PM - Thread Starter
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Quote:
Originally Posted by mtg90 View Post
The rise above 2k certainly isn't correct. The drop below 250 could be placement/room/SBIR rather then an issue with the speaker. 1/4 wavelength at 150hz is ~22.5" so if the front of the baffles are around that distance from the wall that would be why you see a cancellation in that range.

Can you take a measurement with the mic placed about 1.5-2' in front of just one speaker centered on the tweeter? Even better pull the speaker out into the room and place it on a chair or stool to do this.

You are using the miniDSP to take the measurements correct?
This measurement is taken about 2' in front of the speaker--only a single pass. I did pull quite a bit of the stuffing out and try to keep it out of the way of the ports.

Yes, I am measuring with the minDSP, and this room is definitely a nightmare for room response.


I appreciate the help!!
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post #7 of 8 Old 11-07-2019, 11:19 PM
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Are both woofers wired in phase? You don't have the wiring to one reversed do you?
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post #8 of 8 Old 11-08-2019, 11:29 AM - Thread Starter
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Originally Posted by mtg90 View Post
Are both woofers wired in phase? You don't have the wiring to one reversed do you?
That was definitely the issue. I managed to do it on both speakers

Lesson learned: Use wire with super obvious tracers.

Also, super-slow video makes it really easy to tell if something is wired out of phase.

I will update when a new set of measurements later this weekend.
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