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subs in free air for testing
subs in free air for testing
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Old 12th February 2018, 09:42 PM   #1
robinlawrie is offline robinlawrie  United Kingdom
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Default subs in free air for testing

im currently in the first testing phase of my 6 channel 3255evm amp.

ive got a minidsp 2x4hd splitting the signal and two btl channels for subwoofers.

speaker cases are currently being cnc cut.

im quite worried as when i hook it all up for testing, the subwoofers sound distorted and awful, even at low volumes and excursions.

according to the minidsp plugin there is no clipping going on anywhere, ive tried analog and usb inputs, same story.

strangely if i run a tone generator, pure tones sound clean. but its a different story with music.

the other channels of the amp (running to old car speakers without cases for testing) with highpass at 100 hz, sound fine.
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Old 13th February 2018, 07:25 AM   #2
chris661 is offline chris661  United Kingdom
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Looks like it's time for some troubleshooting, then.

Drivers:
- Do the cones move smoothly when you push them?
- Is the DC resistance somewhere sensible? You want 2.9-3.5ohm DC for a 4ohm woofer, or 5-7ohm for an 8ohm woofer.

What happens when you take the MiniDSP out of the signal path?
What about using a different amplifier?

Swap things out, one at a time, until you find the culprit.

Chris
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Old 13th February 2018, 09:47 AM   #3
RobWells is offline RobWells  United Kingdom
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If the sub driver is not in a box then it won't take much to drive it past xmax ? Maybe try it in a box.
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Old 13th February 2018, 02:40 PM   #4
DiscoJones is offline DiscoJones  United States
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Quote:
Originally Posted by RobWells View Post
If the sub driver is not in a box then it won't take much to drive it past xmax ? Maybe try it in a box.
I agree. Some subs produce a lot of mechanical noise that you won't hear once mounted in an enclosure. Don't waste your time troubleshooting a problem that may not be.

Dan
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Old 13th February 2018, 02:46 PM   #5
robinlawrie is offline robinlawrie  United Kingdom
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Quote:
Originally Posted by DiscoJones View Post
I agree. Some subs produce a lot of mechanical noise that you won't hear once mounted in an enclosure. Don't waste your time troubleshooting a problem that may not be.

Dan

yes thats what im worried im doing!

however a) its definitely not xmax, i can hear the distortion clearly when the cone is only moving a mm or two (13mm xmax drivers)

b) wood is being cut for drivers now, but wont be here for a few weeks... i guess i could rough up a box from plywood...

c) i want to finish constructing the amp, and i cant do the final mounting of components until im sure its working properly..

anyway im going to do some initial testing of amp tonight.. ill report back.
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