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Old 4th September 2013, 12:58 PM   #1
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Default Sub build questions

I built a subwoofer enclosure and I'm not getting the highs above 45hz through the LFE as I'm getting through the high lvl inputs. I know it's not going to be the greatest sub, but I have an extra amp from a Mirage Omni S8 subwoofer. I purchased an Infinity Reference 1062w subwoofer I got for cheap and built a 1.75 cu ft slot ported enclosure tuned to 26hz. I'm using a Yamaha RX-V565 receiver and the sub is wired in series for 8 ohm.

Attached are the box dimensions and the plot I got from WinISD.

Using the LFE connection, my frequency response doesn't sound right. The sub is fairly quiet down to about 45hz then gets about twice as loud between 45hz and about 25hz, and drops off quick after that.

Using the high level inputs I get about the same volume until about 25hz when it drops off.

In other words, the high level input gives me louder highs above 45hz than the LFE input.

Only settings changed when using high level:
sub amp low pass filter set to 100hz
receiver set to bass output to fronts and set to large.

using lfe input:
sub amp low pass filter off
receiver set to bass output to subwoofer with crossover set to 100hz and fronts set to small.

At first I thought maybe the box was built wrong, but it sounds good using the high lvl inputs.

Is this normal? If not, is the amp the problem or the receiver? Thanks.
Attached Images
File Type: jpg subwoofer_build.jpg (67.2 KB, 138 views)
File Type: jpg subwoofer_plot.jpg (124.1 KB, 136 views)

Last edited by oTRONo; 4th September 2013 at 09:22 PM.
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Old 4th September 2013, 04:41 PM   #2
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Quote:
Originally Posted by oTRONo View Post
I built a subwoofer enclosure and I'm not getting the highs above 45hz through the LFE as I'm getting through the high lvl inputs. I know it's not going to be the greatest sub, but I have an extra amp from a Mirage Omni S8 subwoofer.

Using the high level inputs I get about the same volume until about 25hz when it drops off.

In other words, the high level input gives me louder highs above 45hz than the LFE input.


Is this normal? If not, is the amp the problem or the receiver? Thanks.
Sounds like the Omni S8 and LFE filters in series combine to reduce frequencies above 45 Hz.
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Old 4th September 2013, 07:01 PM   #3
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I have the high pass filter on the amp turned off when using the LFE input. It shouldn't be filtering anything should it?
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Old 4th September 2013, 07:45 PM   #4
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Sorry, the 75 page manual is above my pay grade ;^).

Check on pages 39-41 to make sure all the settings are as you want.
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Old 4th September 2013, 09:21 PM   #5
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Thanks for the help. Yes, everything is set as it should. It's an older receiver, could it be sending a bad signal to the subwoofer? I wish I still had the original omni subwoofer, I didn't test it while I had it.

Mistake in op, the amp LOW PASS filter is set on or off, not the HIGH PASS. Sorry.
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Old 4th September 2013, 11:03 PM   #6
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Update, I just plugged the subwoofer into my computer's lfe out and I get the same type of response curve, low down to about 45hz then volume increases.

It's definitely something with the Omni S8 amp. I have 2 of them and they both behave the same. Seems odd that they are filtering higher signals even with the filter turned off, but only when using the lfe input and not the high level input.
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Old 5th September 2013, 06:41 AM   #7
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Hmm, something sounds strange here, the subwoofer amp cant possibly "know" if it is getting a signal from a LFE or a Mains channel from your receiver or computer, it can only process the what you send to it.

Have you tried to just change the input to the sub amp, without changing any settings on it? I know youŽd like to run a low pass filter on it, but for testing it would be good to change just one parameter at a time.

My guess would that either the settings on your receiver for the LFE channel is wrong or perhaps it is boosting the sub 45hz frequencys or something? Or, the lowpass on your sub amp is on when you think it is of and viceversa(or not working correctly)

Test with both settings, low pass on and off, with both signal sources and see where that takes you

Good luck!
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Old 5th September 2013, 07:22 PM   #8
dangus is offline dangus  Canada
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The amp might be designed with a built-in boost at low frequencies. Have you measured the electrical response? Feed the sub amp a sine wave, then measure the voltage going to the woofer.
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Old 6th September 2013, 01:05 AM   #9
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Yes, I believe you are right. It does seem to have a boost at about 35hz.

With a sweep from 120hz down to 0hz, I get a steady voltage increase until I hit about 55hz. It then increases dramatically and peaks at 35hz and begins to drop towards 0 at about 10hz. I did this without the subwoofer connected, or should I test with it connected?

Now the question is do I try it in a smaller, sealed enclosure? Or should I still go ported, with some modifications. As is, the lower end is just too much.

Sorry for all the questions, I haven't built a sub box since I was a teen, about 25 yrs ago and this is my first for in home.

Thanks.
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Old 6th September 2013, 01:29 AM   #10
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Quote:
Originally Posted by oTRONo View Post
Yes, I believe you are right. It does seem to have a boost at about 35hz.

With a sweep from 120hz down to 0hz, I get a steady voltage increase until I hit about 55hz. It then increases dramatically and peaks at 35hz and begins to drop towards 0 at about 10hz. I did this without the subwoofer connected, or should I test with it connected?

Now the question is do I try it in a smaller, sealed enclosure? Or should I still go ported, with some modifications. As is, the lower end is just too much.

Sorry for all the questions, I haven't built a sub box since I was a teen, about 25 yrs ago and this is my first for in home.

Thanks.
So let me understand. The Mirage Omni S8 subwoofer (8"?!) had this boost set, in the factory, for it's small driver and it can not be addressed/changed and you are using this same amp?
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