Can this be Right?...Or did I mess something up?

Cheetodust

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This is my first time using REW but followed an instructional video by Home Theater Gurus on youtube to get started. I have a Dayton Audio 15" Subwoofer with SPA-1000 plate amp and an HSU STF-2 connected to a Mini-DSP HD. I took several measurements of both subwoofers and this is my result.
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32159


Can this actually be correct or do you think there is a setting somewhere that is causing such a steep and early roll off? Very disappointing to not even be below 40Hz. Thanks for any suggestions.
 

JStewart

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Something is amiss. By default the minidsp comes with crossovers on. Sure you got them bypassed?
 

Jean Ibarz

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Hi, yeah it seems that your subwoofer is high pass filtered. Do you hear anything when you play a sinus at 40hz ?
 

Cheetodust

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Went into Minidsp and made sure EQ and crossover are bypassed. Played with the tone generator and set at 40Hz. Was able to hear a "bump" that cycles like every 1-2 seconds. I keep hearing the sweep tone through my other speakers though. Could that be effecting anything? I set my receiver (Denon AVR-X6500H) crossover for all speakers at 250Hz with the LFE crossover at 120Hz for the testing. Have the sweep tone gong from 10 - 120Hz. Went into my laptop sound settings and made sure nothing was off there. Set to 7 channel instead of stero like default. Was able to view a slight bump at 40-50 Hz but nothing like it should be. Have my laptop set to output sound through HDMI to receiver with HDMI into AUX 1 on front. Really appreciate your help. I know it's not easy diagnosing this over the internet.
 

Jean Ibarz

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I think you have a problem with your amplifier. Try switching the analog output maybe, see if it sovles your problem.
 

JStewart

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I keep hearing the sweep tone through my other speakers though.
Just to be sure I understand, are you sending the sweep via hdmi to the sub channel AND hearing the sweep over other speakers too? If yes then something is getting downmixed. Perhaps in windows if you're using windows if the sound card is set to stereo.

You can try @Jean Ibarz suggestion or try sending the sweep to right or left only, with the right or left set to small, with the xo at 250 as you have done, and with the speaker wires disconnected from the back of the right or left that your sending the sweep to. Turn off any dsp processing (upmixers, downmixers, sound modes) in the AVR. Bass manaagement will route the signal to the sub.

Also what do hear or record in REW when you run a sweep past the low frequencies? 10,000Hz for example.
 

JStewart

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Went into my laptop sound settings and made sure nothing was off there. Set to 7 channel instead of stero like default.
Just to be sure I understand, are you sending the sweep via hdmi to the sub channel AND hearing the sweep over other speakers too? If yes then something is getting downmixed. Perhaps in windows if you're using windows if the sound card is set to stereo.
Missed that. My bad.
 

Cheetodust

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Turn off any dsp processing (upmixers, downmixers, sound modes) in the AVR. Bass manaagement will route the signal to the sub.
Yeah I have it set to Dolby Digital. Wonder if that's the issue? What do you set your AVR to when testing? Thanks for the help.

BTW, I disconnected the MiniDSP and ran straight from the AVR. No change in the pattern. I also changed the parameters for displaying the graph. Here is what is looks like.
Annotation 2020-06-01 175148.png
 

JStewart

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What do you set your AVR to when testing?
It's called different things on different AVRs. Check the owner's manual for whatever mode bypasses processing. Let us know brand and model and we can help.

On REW preferences soundcard tab check to be sure your UMIK is the specifically selected mic and it does not say "Default Device" for microphone. Otherwise you may be unintentionally using your laptop mic.

What channel where you sending the sweep signal to in post #8? What was the XO for that channel set to? Need more info to help.

Please do a sweep of one of your main speakers set to large if you haven't already and post the results. We need to narrow down the issue. Is it an AVR setting issue or is it a REW/Laptop setup issue?
 

Cheetodust

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Page 141 of the owners manual. "Direct" looks right.
Direct helped but still not great. I am not familiar with the capabilities of the Mini DSP HD. Is it still worth it to try and
and improve upon this until I am able to buy a better sub?

I think you have a problem with your amplifier. Try switching the analog output maybe, see if it sovles your problem.
I tried this and the wave was almost exactly the same. Maybe 1-2 decibels lower than the LFE channel otherwise exactly same.
 

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JStewart

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Here's a consumerS REW measurement I found for a Dayton SUB1500

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That's more in line with what I'd expect.

Still think something isn't right with taking the measurements. Don't know what though, obviously.
 

Cheetodust

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Been working on this and finally have a better measurement. Believe it or not, room treatments have helped a ton! My curve is still less than desirable though. I have been experimenting with the EQ in REW. As you can guess by the graph the bass is very boomy. How should I address this in REW? I tried cutting down the 120 - 75Hz but then sounds like there is no midbass. Have any suggestions for EQ this less than desirable curve? TIA!
32942
 

Jean Ibarz

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Gemini XP3000
Additional Amp
Samson SERVO 600
Other Amp
Samson SERVO 200 and Yamaha STR-DB840
Hi there,

Can you please provide the .mdat file ? In REW, file, save measurement.

Maybe we can try to figure out some things.
 

Cheetodust

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I just looked at the mdat file and there are a lot of measurement on it that I did no intend to save. The "no EQ" one is the final measurement prior to EQ. Thanks!
 

Jean Ibarz

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My AV System  
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Gemini XP3000
Additional Amp
Samson SERVO 600
Other Amp
Samson SERVO 200 and Yamaha STR-DB840
You have a distortion problem. The noise level is "ok" relative to the fundamental, but your total harmonic distortion (THD) is higher than your fundamental for some frequencies, so I suspect that the problem comes from your amplifier.

image.png

png file
 

Cheetodust

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Can you tell on the mdat file if it's the front sub or rear sub? There are separate measurements in the mdat file. Thanks again
 

Jean Ibarz

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My AV System  
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Computer
Main Amp
Gemini XP3000
Additional Amp
Samson SERVO 600
Other Amp
Samson SERVO 200 and Yamaha STR-DB840
The problem appears on both.
 

John Mulcahy

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Clipping the signal to the front sub, perhaps, seems mostly odd harmonics. Do you have boost filters in your EQ?
 

Cheetodust

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No EQ applied in the mdat file. This was my aligned readings just prior to applying EQ. I'm not sure if this will help but when running the sweep at the beginning, the front subwoofer sounds very.......floppy. I don't really know how else to describe it. You can kind of see it on the graph down low. Obvious struggle to produce the low tones.
 
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