# REW First Time Graphs - Dual Subs - Questions



## RastusW (Jun 29, 2007)

I'm in the final stages of building a new theater.
REW seems like a great program. I've just begun to try and learn to use it. Any help is greatly appreciated.

Taking brucek's lead, I bought the Turtle Beach USB SRM sound card, Behringer ECM8000, and the Xenyx 802.

For the time being, I'd like to try and EQ my two Revel subs as much as possible using only the one filter located on the back of each (see pic). I took three measurements 1)Left Sub Only 2)Right Sub Only 3)Both Subs

*Left Sub*







*
Right Sub Only*








*Both Subs*









Do the graphs look reasonably correct?
What we the best way to create a filter on my subs regarding these graphs? 
I assume I have to pick my worst offending Hz number and try to smooth that out?

My speakers sit on a stage at the front of the room (see pic) so moving them is not much of an option. Black acoustically transparent cloth will be covering them soon.

*Subs outlined w/ white...*








*Revel Sub Controls*









Sorry for all the pics and thanks for any help or links to info.

Rastus


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## brucek (Apr 11, 2006)

In your case it probably wouldn't be appropriate to offer the standard advice of moving one of your subs into the room to locate the optimum response position and then co-locating the second sub, as I suspect aesthetics trumps good response. And don't take that the wrong way, because it sure does look good, but the trade off is that your speakers and subs are in about the worst possible positions I suspect. Really beautiful looking theater though. 

Your main problem with the subs response is at 30Hz, and the single filter on the Revels should be able to bring that down without any problem.

I would simply play with the (freq/gain/BW) controls on the two subs until the peak was reduced to the target line. You can accomplish this with successive measures, or simply use the REW RTA and do it dynamically while watching the REW graph.


The graph below is probably the best way for me to show you the controls to set in REW for the sub RTA plot. You can see the RTA plot as the bottom line, with the upper line showing the selected measurement plot as a comparison.
Select the Spectrum tab in REW and choose RTA 1/24 mode, and then start the REW Generator with Pink PN.










brucek


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## RastusW (Jun 29, 2007)

Thanks for your input brucek. 
You need a tip jar, or an amazon wish list.
I'm off to try try and do what you suggested.

Unfortunately, you are right in that moving subs is not much of an option. 
Would a Behringer unit help me substantially? 
If yes, on the subs, would I turn the level to nominal, low pass filter to off, the eq to off and adjust everything through the Behringer? If this is correct, this would be the best solution for me. Monday, the black cloth is going to be installed in front of the speakers and its going to be a big process to access the subs in the future. 

I may have more questions.

Again, thank you for all your input, 

Rastus


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## brucek (Apr 11, 2006)

> Would a Behringer unit help me substantially?


The response doesn't look like it would benefit that much with any more than the one internal filter you have in each sub. You need to lower the 30Hz peak...



> If yes, on the subs, would I turn the level to nominal, low pass filter to off, the eq to off and adjust everything through the Behringer?


But, I'm confused when you say _low pass filter to off_. Do you not have the low pass filter set to off at present, as the bass management and crossover are normally set with your receiver?

I would add that once you have your subs filters set, add the mains to the mix and do another measurement (using REW the same as if you were measuring the subs without the mains), and pay special heed to the crossover area, while switching the phase switches between 0 and 180 to obtain the smoothest response at the crossover area.

brucek


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## salvasol (Oct 31, 2006)

RastusW said:


> For the time being, I'd like to try and EQ my two Revel subs as much as possible using only the one filter located on the back of each (see pic). I took three measurements 1)Left Sub Only 2)Right Sub Only 3)Both Subs


Nice room ...:T

Does your AVR has a PEQ (Parametric Equalizer) to smooth the sub response??? ...my Yamaha RXV-2700 has one, is not the best but it helps ...

Like Brucek said, try the filter on the back of the sub and if your AVR has the PEQ use that one too :yes:


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## RastusW (Jun 29, 2007)

brucek-
Yes I have the low pass filter set to off. I'm using the Marantz 8002 for bass management and the crossover (80Hz). Thanks for asking though.

I was able to knock down the peak @ 30Hz quite a bit. I left the file on my laptop. I'll post it tomorrow.

salvasol-
That's a good idea regarding the AVR PEQ. I'll look into that. All of this is pretty new to me.

Thank you both for the complements on the theater. I'm realizing this audio thing has become an obsession.

Rastus


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## Wayne A. Pflughaupt (Apr 13, 2006)

Welcome to the Forum, Rastus!

Thanks very much for the room and back-of-sub pics - sure helps us evalaute your situation with minimal "guess work!" 

I'll generally agree with what the others have said, with maybe the exception of that broad hole you have between ~58-75 Hz. It would be a concern if you plan to do any music listening - a BFD could take care of that. But if this is exclusively a theater room, then it won't matter much, since the bulk of movie bass is all about "boom." Taming the 30 dB peak will be all you need if that's the case .

Let's talk a bit about extension, since that's an important aspect of a subwoofer and the movie-viewing experience. Judging from what I can see from the B12's specs, it looks like you'll be able to realize its rated extension even with the less-than-optimal locations. According to the specs, the sub starts rolling out at 28 dB and is down 10 dB @ 23 Hz. If you can flatten out your peak you should be able to get extension to about 25 Hz before response drops out.

I sure wish you had hooked up with us before you bought your gear. For the price of your Revels, or even less, there were other options that could have got your extension below 20 Hz or lower. As a general rule, 10" woofs are a bit small for a home theater sub, whereas it's easy to find 12-inchers that can get 20-25 Hz with no or minimal EQ. At least a couple of subs from SVS in your price range get down to 18 Hz, and probably some from Hsu. Probably not as pretty as the Revel, but you said they're going behind a cloth cover anyway, right?  There are passages in movies like _Lord of the Rings_, for instance, that get that low, and the difference between a 25 Hz sub and an 18 Hz sub is audible.

That said, you can certainly have an enjoyable movie experience with subs that only get down to 25 Hz. That's all the ones I'm currently using will do. But if I had a dedicated room and money to spend I'd sure be going for the depth!

Regards,
Wayne


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## RastusW (Jun 29, 2007)

Wayne-


> I'll generally agree with what the others have said, with maybe the exception of that broad hole you have between ~58-75 Hz. It would be a concern if you plan to do any music listening - a BFD could take care of that.


I like to watch concerts a lot, as well as movies. How would I utilize a BFD to take care of the hole between ~58-75 Hz? I never even seen a BFD much less studied how to utilize one. I'll look into it.

I think it would be fair to say I'm not much of a "bass head". I like the bass to be tight and accurate. 
When shopping for components I found subs and screens to be the most difficult. Without being able to do an A/B comparison it was hard to discern between different makes and models. In the end I decided to just stay w/ a product I like and trust. I don't doubt there are better subs. It just came time to make a decision and I went with what I felt was right. It's also was hard to find demonstrations of speakers that are only marketed online. Anyway, not trying to rationalize my decision, just letting you know my mindset. : )

Rastus


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## RastusW (Jun 29, 2007)

Last night I was not able to completely flatten my 30Hz problem. 

Again, I'm only pretending I know what I'm doing.
Common sense told me to adjust the sub dials as follows: *Frequency* to 30 (the Hz with problems), *Level* to -12 (87db-75db=12), *Bandwidth* - .36 I just tried different positions and wound up with that.
What is the bandwidth dial used for in relation to it's effect on the trace on a graph?
Did I use the dials correctly in theory?

Working blind, are there settings that could have possibly brought the trace @ 30Hz down further?
I'm just trying to learn the correlation between the sub dials, terminology, and each ones effect on the trace. Using trial and error had my head spinning after @ 20minutes.

I hate to just be asking for answers. If someone has and would rather post links to info that would be appreciated as well. 

Thanks,
Rastus


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## salvasol (Oct 31, 2006)

RastusW said:


> What is the bandwidth dial used for in relation to it's effect on the trace on a graph?
> Did I use the dials correctly in theory?
> 
> I hate to just be asking for answers. If someone has and would rather post links to info that would be appreciated as well.


I think you did it right :T

I'm not an expert too, but I think that bandwidth affect the frequencies near 30Hz, the lower the bandwidth it will affect less frequencies ...with a higher (wider) bandwidth it will affect more :huh: (last night I was reading the PEQ adjustments on my Yamaha and they mentiones Frequency, Band and Q Factor (Bandwidth perhaps).

Don't worry about asking questions, there's a lot of members her that love to help others :bigsmile:.


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## brucek (Apr 11, 2006)

> Did I use the dials correctly in theory?


Yep. The frequency and level are fairly obvious. The bandwidth is a bit trickier and will require you use trial and error. The bandwidth is simply the width of the filter (usually at the 3dB points). Too narrow, and you won't capture the entire peak Too wide, and you'll extend it too far on either side of the peak, resulting in a reducing of areas you don't want to reduce. 

Start narrow and work your way wider with trial and error by continuous remeasuring. Using the RTA is much easier in accomplishing this..

brucek


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## RastusW (Jun 29, 2007)

Thanks brucek.

When I tried to plot my mains last night I could hear some static. Especially when I moved my finger around on my laptop's track pad. Is this normal? Will it effect my readings?

Thanks,
Rastus


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## brucek (Apr 11, 2006)

Since you're using a USB soundcard, I assume you're driving it with a laptop.

If so, try and run the laptop from its battery (to avoid ground loop noise), and be sure to shut off the wireless ability.

There should be no static. Sometimes when the laptop is old and challenged, it has a problem running REW, so be sure to reduce the length and number of sweeps selections in the measure popup to as low as possible. You can also play with the buffer sizes in the settings popup also.

brucek


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