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Discussion Starter · #1 ·
Hey guys, I picked up an 1124p last week. I have the downfiring version of the Elemental Designs a5-350 sub. I finally got around to downloading v5 of REW and dialing the eq in today. I must say I really like the new version! :T With the -10dBv setting on the 1124p I had to dial my sub level way back in my receiver to around -14 to stay out of the red, so I switched it to the +4dBu. It now maxes out at the top of the green LEDs to keep me away from digital distortion. From what I have read there should be no issue to doing that, am I right?

Here is what the sweep looked like with no eq. I have tons of natural room gain between 27 and 48 hz. I have also changed the graph limits, since I cross over my system at 100hz I don't really care what is going on above 100hz. So I know it's out of the normal specs for displaying graphs. :)



Using 4 filters via the 1124p and REW I ended up with this. I did not boost any levels, just cut. Can anyone explain what the phase graph means?



Here it is without the phase graph.



All in all I am very happy with how this has turned out! And better yet I haven't had the hum issue with my 1124p!
 

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Discussion Starter · #2 ·
I forgot to add something I found quite funny. My wife saw the eq and she says that it looks quite fancy, so she calls it 'The Business Maker'!

So from now on it's new name is The Business Maker! :rofl2:
 

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That's a very nice looking response, good job with the EQ. The phase stays mostly around -180/180 degrees (those are actually the same point, phase wraps around from -180 to 180) which means through that region the sub is inverting. You need to look at measurements of the sub plus each main speaker in turn to establish whether that is the best phase for the sub by looking at the response through the crossover region.
 

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Discussion Starter · #4 ·
That's a very nice looking response, good job with the EQ. The phase stays mostly around -180/180 degrees (those are actually the same point, phase wraps around from -180 to 180) which means through that region the sub is inverting. You need to look at measurements of the sub plus each main speaker in turn to establish whether that is the best phase for the sub by looking at the response through the crossover region.
Thanks John. Ok from what I understand, my sub is flipping from -180 to 180 (where it goes from bottom to top and vice versa) which is reletively the same phase. As far as the phase alone is sitting is that alright? Should the phase not be inverting like it is? And as far as measuring the sub + each main, I should check that through the crossover point to make sure it's not creating a null, right?
 

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as far as measuring the sub + each main, I should check that through the crossover point to make sure it's not creating a null, right?
Right. Whether the sub is better inverting or not depends on what the mains are doing and where you sit relative to the sub and mains, easiest is definitely to measure and see what works best. You can also vary the sub distance setting to tweak the result.
 

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Discussion Starter · #6 ·
Right. Whether the sub is better inverting or not depends on what the mains are doing and where you sit relative to the sub and mains, easiest is definitely to measure and see what works best. You can also vary the sub distance setting to tweak the result.
Ok. Will playing around with the phase have any adverse effects on the response? I don't think it would with varying the distance, but I'm unsure with the phase. Would I have to re-eq if the phase is altered?
 

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Altering the phase will have no effect on the sub alone, but will affect how it interacts with the mains. Even before you do anything with phase you need to see how the sub behaves with the mains, as there can be a fair degree of overlap which can change things quite a bit - peaks that were there with the sub alone can disappear when the mains come in, or new ones can appear. All gets very tricky :)
 

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Discussion Starter · #8 ·
Altering the phase will have no effect on the sub alone, but will affect how it interacts with the mains. Even before you do anything with phase you need to see how the sub behaves with the mains, as there can be a fair degree of overlap which can change things quite a bit - peaks that were there with the sub alone can disappear when the mains come in, or new ones can appear. All gets very tricky :)
Thanks again for your help John. I'll mess around with this next weekend and see what I can do. :) I'll update this thread when I have the results.
 

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I switched it to the +4dBu. It now maxes out at the top of the green LEDs to keep me away from digital distortion. From what I have read there should be no issue to doing that, am I right?
Correct.


Using 4 filters via the 1124p and REW I ended up with this. I did not boost any levels, just cut.
You can see more on the topic here, but basically boosting vs. cutting is largely academic (unless we’re talking about nulls). When you look at the equalizer’s electrical response (you can do that with REW by checking the “Filters” box), using a boosted filter you can see a big hump in the signal, right? Well, use only cuts instead, and what do you have between the cuts? Big humps in the signal.

Looking at your two graphs it appears that you applied some really severe EQ filters, some probably on the order of -15 dB or more, to get response as flat as the second graph shows: Where initially you had response dropping about 15 dB/octave below ~30 Hz, you now have response that doesn’t start a serious drop until ~18 Hz. So even employing only cutting filters, you’ve ended up severely boosting response <30 Hz. Looking at REW’s filter response plot would confirm this.

So – it’s great that you were able to flatten response, just don’t think it was accomplished with no boosting. :D

Regards,
Wayne
 

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Where initially you had response dropping about 15 dB/octave below ~30 Hz, you now have response that doesn’t start a serious drop until ~18 Hz. So even employing only cutting filters, you’ve ended up severely boosting response <30 Hz. Looking at REW’s filter response plot would confirm this.

So – it’s great that you were able to flatten response, just don’t think it was accomplished with no boosting. :D
[FONT]


This makes absolutely no sense to me.

Is there a greater load on the amplifier at 18 Hz after filters than there was before filters? Will he now clip the signal below 30Hz easier than he did before? I don't see how this would be the case so I don't see how you can call it "boosting". :huh:
 

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Is there a greater load on the amplifier at 18 Hz after filters than there was before filters? Will he now clip the signal below 30Hz easier than he did before?
Well, take a look at his two graphs. Before EQ, 18 Hz was 20 dB lower than the peak in response at ~48 Hz. After EQ, 18 Hz is only ~5 dB lower than the (new) response peak at ~36 Hz. He's going to have to increase his sub's volume level to make up for the ~15 dB in audible gain lost to equalizing. This means that there will now be ~15 dB more power delivered/required at 18 Hz than before (i.e. the difference between 18 Hz's level relative to the pre- and post-EQ peaks). So the answer is “yes and “yes.”

It’s all explained to greater detail, with graphs, in post I linked in my previous post. Did you study it?

Regards,
Wayne
 

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Discussion Starter · #12 · (Edited)
Correct.


You can see more on the topic here, but basically boosting vs. cutting is largely academic (unless we’re talking about nulls). When you look at the equalizer’s electrical response (you can do that with REW by checking the “Filters” box), using a boosted filter you can see a big hump in the signal, right? Well, use only cuts instead, and what do you have between the cuts? Big humps in the signal.

Looking at your two graphs it appears that you applied some really severe EQ filters, some probably on the order of -15 dB or more, to get response as flat as the second graph shows: Where initially you had response dropping about 15 dB/octave below ~30 Hz, you now have response that doesn’t start a serious drop until ~18 Hz. So even employing only cutting filters, you’ve ended up severely boosting response <30 Hz. Looking at REW’s filter response plot would confirm this.

So – it’s great that you were able to flatten response, just don’t think it was accomplished with no boosting. :D

Regards,
Wayne
Well, what I meant by no boosting was I didn't apply gain in the filters anywhere in my response. :)

The only reason my graphs are so different is because running with no EQ I start clipping in REW because of that peak so I have to lower the level. With the EQ going I can actually run sweeps at the level I should be able to without clipping. I really didn't have to boost levels on my sub or avr too much from before the filters were applied to after. My sub is rated to +/- 3db at 19hz, so I should be able to have usable extension that low.

Actually my filters are as follows...

Filter 1 - Frequency 48.00 = 50 -4 Gain = -14 BW = 6
Filter 2 - Frequency 29.88 = 32 -5 Gain = -9 BW = 9
Filter 3 - Frequency 42.50 = 40 +5 Gain = -8 BW = 10
Filter 4 - Frequency 88.00 = 80 +8 Gain = -5 BW = 6
 

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Discussion Starter · #13 ·
Well, take a look at his two graphs. Before EQ, 18 Hz was 20 dB lower than the peak in response at ~48 Hz. After EQ, 18 Hz is only ~5 dB lower than the (new) response peak at ~36 Hz. He's going to have to increase his sub's volume level to make up for the ~15 dB in audible gain lost to equalizing. This means that there will now be ~15 dB more power delivered/required at 18 Hz than before (i.e. the difference between 18 Hz's level relative to the pre- and post-EQ peaks). So the answer is “yes and “yes.”

It’s all explained to greater detail, with graphs, in post I linked in my previous post. Did you study it?

Regards,
Wayne
Isn't clipping audible? The levels I listen to movies at max is -10 below reference. I have demoed some pretty heavy bass scenes, i.e. Master and Commander, etc. I have had no issues with chuffing from the ports, no mechanical clanking sounds, or anything else abnormal. So my question is am I driving this sub at unreasonable levels with the EQ?
 

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I've read your posts and appreciate the content. I still don't understand this statement...

He's going to have to increase his sub's volume level to make up for the ~15 dB in audible gain lost to equalizing.
Why? Does your logic assume that the +15dB peak was at the correct level and everything else too low? This is where I don't understand your argument. Perhaps he was already at the correct 18 Hz level before equalizing. He certainly would not need to adjust his amplifier gain by 15 dB to maintain the same output at 18 Hz that he had before eq. Your graphs do no include the effect of the room modes that the filters were put in place to tame.

I know my room has a huge gain at 36 Hz. I put in a big filter to get rid of that big peak. I did not have to adjust my gain but just a tad to get levels where I needed them after eq. Certainly nothing close to the amount of negative gain in my filter...
 

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Isn't clipping audible? The levels I listen to movies at max is -10 below reference. I have demoed some pretty heavy bass scenes, i.e. Master and Commander, etc. I have had no issues with chuffing from the ports, no mechanical clanking sounds, or anything else abnormal. So my question is am I driving this sub at unreasonable levels with the EQ?
Doesn’t sound like it. Believe me, if you overdrive the sub, you’ll know it! It’ll bottom out and make all kinds of rude noises.

However, a lot of subs these days, especially high-performance models, have built in limiting to prevent overdriving them.

Wayne I have another question. Where in REW do I find the filter response plot?
I’m not using V5 yet, but in V4 there are several boxes below the measurement – “Target,” “Corrected,” “Mic/Meter Cal,” etc. Look for the one that says “Filters + Target” (which will show the effect of the filter and your electronic crossover together). Un-check the other boxes, especially for the measurement, and you will see the electronic response of the filters used (from the EQ panel).

Regards,
Wayne
 

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I've read your posts and appreciate the content. I still don't understand this statement...

He's going to have to increase his sub's volume level to make up for the ~15 dB in audible gain lost to equalizing.
Why? Does your logic assume that the +15dB peak was at the correct level and everything else too low?
Essentially, yes. Before EQing, a peak in response (caused by the room) is naturally the loudest thing you are hearing. As such, the level the sub was initially set at was based on that peak: If you used an SPL meter to adjust your 5.1 levels, for instance, the dB reading you get for the sub will be the loudest frequency it’s generating.

Naturally, if you cut down the peak via equalization, the sub will now sound noticeably quieter than before. You’ll have to increase the sub’s volume to compensate.


I know my room has a huge gain at 36 Hz. I put in a big filter to get rid of that big peak. I did not have to adjust my gain but just a tad to get levels where I needed them after eq. Certainly nothing close to the amount of negative gain in my filter...
Even if only a minor adjustment was needed in your case or even none at all, the situation is that your sub now has relatively flat response. This means all frequencies above and below your 36 Hz peak are now acoustically equal to the former peak, when before they were below it. In other words, they technically have been boosted, even if you used no positive-gain filters.

The point is, using boost or cut filters gets the same acoustic results. There is no inherent advantage to using cut-only filters, as is commonly (and wrongly) circulated on the various forums.

Regards,
Wayne
 

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Discussion Starter · #19 ·
Wayne,

I really appreciate your explanations and comments. You have definately helped me understand more about eq'ing and helped me look at it from different angles.


Also, thanks to vann_d as well for asking for clarification!

:T
 
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