Some basic questions on EQing my sub - AVS Forum
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Old 02-09-2013, 07:04 AM - Thread Starter
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Just bought a Feedback Destroyer Pro and a digital SPL meter.

Was wondering when EQing the sub should I be playing sine waves from every frequency when calibrating or should I be going in say increments of 5, i.e. 20hz, 25hz, 30hz, 35hz, etc.?

Also what Db on the meter do you calibrate a sub to normally?

Thanks for any help guys!
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Old 02-09-2013, 08:04 AM
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You need measuring software and a USB mic to display in-room response as a chart. You could do it as you propose, but it would take forever.

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Old 02-09-2013, 08:15 AM - Thread Starter
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Like the Room EQ Wizard. I was looking into that. So you need a USB mic that plugs into the laptop, but do you also need any cables that run to the feedback destroyer pro from the laptop or mic?
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Old 02-09-2013, 08:23 AM
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See this thread: http://www.avsforum.com/t/1449924/simplified-rew-setup-and-use-usb-mic-hdmi-connection-including-measurement-techniques-and-how-to-interpret-graphs

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Old 02-09-2013, 08:48 AM - Thread Starter
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The only part I dont get is the loop cable for the feedback destroyer pro? So I need 2 sets of XLR cables then? One for the loop and one running to the amp? Totally confused there.
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Old 02-09-2013, 09:00 AM - Thread Starter
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Ok, have been reading and it appears now I need a sound card with the right audio outputs just to be able to calibrate. I think I will just do it the really long and tedious way because I already have enough money stuck into this. I cant see buying a soundcard JUST for a one use only ordeal.
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Old 02-20-2013, 03:03 PM - Thread Starter
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Well I went through the process the long and hard way. It didnt bother me.

What IS bothering me is that at 59hz I have a major drop in output , its reading 70db. Even cranking the gain on the FBQ to +15 on that frequency its still not reading over 84 db.

The average of the other frequencies is 88-92 db.

What do you suggest, that I lower the other freq down to around the 82-84 db mark to flatten it out?
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Old 02-20-2013, 03:33 PM
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Quote:
Originally Posted by TenTonBass View Post

Well I went through the process the long and hard way. It didnt bother me.

What IS bothering me is that at 59hz I have a major drop in output , its reading 70db. Even cranking the gain on the FBQ to +15 on that frequency its still not reading over 84 db.

The average of the other frequencies is 88-92 db.

What do you suggest, that I lower the other freq down to around the 82-84 db mark to flatten it out?
There is only so much you can do with one sub. Smoothing out room modes requires at least two.

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Old 02-20-2013, 03:38 PM
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Quote:
Originally Posted by TenTonBass View Post

I cant see buying a soundcard JUST for a one use only ordeal.

One use...LOL!
Quote:
Originally Posted by TenTonBass View Post

Well I went through the process the long and hard way. It didnt bother me.

What IS bothering me is that at 59hz I have a major drop in output , its reading 70db. Even cranking the gain on the FBQ to +15 on that frequency its still not reading over 84 db.

The average of the other frequencies is 88-92 db.

What do you suggest, that I lower the other freq down to around the 82-84 db mark to flatten it out?

You should EQ only to tame the peaks, not boost the dips. If you boost the dips too much (more than a few db), you risk damage to your equipment. FR dips are fixed with sub placement, multiple subs, and/or room treatment.

Sounds to me like you have a null at your MLP right around 59hz. Does the same null appear at different listening positions?
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Ok, have been reading and it appears now I need a sound card with the right audio outputs just to be able to calibrate. I think I will just do it the really long and tedious way because I already have enough money stuck into this.

Does your laptop do HDMI or have a headphone out jack? Either way, you are good to go with a USB mic (i.e UMM-6).

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Old 02-20-2013, 03:41 PM - Thread Starter
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Yeah good point. I will the do the best I can with what I have, it will be better than no equalization at least.
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Old 02-20-2013, 04:00 PM - Thread Starter
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I never knew that about only EQing to tame the peaks. I really didnt have any crazy peaks.

44-52 hz seemed to hit the highest at 95db but all the frequencies before and after that were around 90-92 db up to the dreaded 70db at 59hz. frown.gif

I have gigantic DIY 15" sub in a box just over 5 cubic feet. I dont have much choice but to put it where I have it. That;s ok, I mean it still sounds pretty damn good.

I just bought a Def Tech CS8080 center with a built in sub and now and I am considering the Def Tech towers with the built in subs.

I am considering running the crossover at 50hz with those speakers because the sub is rather nice and flat up to 50hz.
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Old 02-20-2013, 04:08 PM
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Originally Posted by Alan P View Post

One use...LOL!
You should EQ only to tame the peaks, not boost the dips.
I wouldn't go that far, up to 6dB of boost won't bother much, especially if it's above 40Hz. If so doing does result in over excursion or clipping you'll hear it long before causing damage, just don't ignore the warning sign of distortion. But more than 6dB indicates a problem that EQ can't fix, so don't try.

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Old 02-20-2013, 04:13 PM - Thread Starter
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Quote:
Originally Posted by Bill Fitzmaurice View Post

I wouldn't go that far, up to 6dB of boost won't bother much, especially if it's above 40Hz. If so doing does result in over excursion or clipping you'll hear it long before causing damage, just don't ignore the warning sign of distortion. But more than 6dB indicates a problem that EQ can't fix, so don't try.

Ok, sounds good, thanks for the help guys!
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Old 02-20-2013, 06:06 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

There is only so much you can do with one sub. Smoothing out room modes requires at least two.

I too had a terrible null, mine at 50Hz. Getting a second PB12 & adjusting the phase from 0 to 180 eliminated the null.
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Old 02-21-2013, 03:28 PM - Thread Starter
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IDK if I'm liking the FDP at all. I set some basic filters in the EQ with a few freq. at +2db and some others at -2db and it doesnt seem to hit at all like it did without the EQ.

Also when the sub is playing and I pause the source material the sub drones on faintly for a second or two after. I dont what that is called but its not cool.
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Old 02-21-2013, 04:28 PM
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Are you EQ'ing to try to get a perfectly flat response from your sub? Most people don't like a flat bass response but prefer a "house curve".

That "droning on" sounds like you may have some setting in the BFD turned on that you don't want, like reverb or sustain or something. I don't have one, but hopefully someone who does can jump in and help.

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Old 02-21-2013, 04:56 PM - Thread Starter
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yeah I was trying to flatten my response.
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