# Connecting Subs & Mains



## Kix_N_Grins (Feb 14, 2015)

Hello,

I'm a newbie at room equalization using REW. I've used an equalizer for 35 years, but have always used them "by ear". I recently put together a 7.1 system and now trying to get the most out of it. From what I've read about REW and equalization, the most important frequency band to equalize is from ~20-250Hz.

My Outlaw Audio AVP has separate Front and Sub outputs. I have no equalizer for the two Velodyne subs that I have. The Velodynes themselves have built-in cross-overs and line-level outputs that could be used for the Fronts. So my question is this: Do I need to purchase another equalizer for the subs, or would I be better off connecting the AVR Fronts to my Velodynes and then the Velodynes to the Front? To use the AVP Sub output, I have to set my speaker size to "small" in the AVP set-up for the Fronts. If I want the full bandwidth to go to the Fronts, I can just change the AVR Speaker Size to "large". It seems like a waste to buy an equalizer for my Velodynes, as they only have a freq range of 20-120Hz. Do they make special "low-frequency" equalizers just for subs that I'm not aware of?

Thanks in advance for any advice you can give.

Kix


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

First, welcome to the Forum!

Although the frequency rage is limited, easiest and cheapest way to get optimal performance for the bass range is with equalization. The best equalizer for this task is a parametric equalizer, as they can be precisely adjusted to address peaks and troughs on response. The reason to use a separate EQ for the sub is that bass EQ typically requires 3-5 filters, and most good-quality parametric EQs don’t more than 5-6 filters, so there isn’t enough filters available to EQ both the subs and main speakers.

Regards,
Wayne


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## Kix_N_Grins (Feb 14, 2015)

Hi Wayne,

Thanks for the welcome, and thanks for answering my question above. What you're saying makes sense to me. Do they sell "low frequency" parametric equalizers that have 4-6 filters that focus on the 20-120Hz range (or thereabouts)? It's been about 25 years since I moth-balled my stereo and I'm just not up-to-date on the new equipment that's come out over that time.

Sorry if my post on the REW board appears the same as this thread, but the questions I'm asking are different. Above, I'm asking what's the best way to connect the subs/front speakers, which determines if I need to buy a dedicated "sub" equalizer. Below, I'll reword the questions I was asking on the Equalization|Calibration > REW board.

When equalizing a room:

From what I've read so far, the emphasis on room equalization is on the Subwoofers and Fronts. I have a 7.1 system, and I'm wondering why it isn't important to equalize the center channel, surrounds and rear speakers?

When using REW:

I'm using two left front speakers and two right front speakers, one set for lower-end freq. range and one for higher end. When I run REW to equalize them, should I EQ both left speakers at the same time, or should I EQ one left speaker first and then the second left speaker? I do have a separate equalizers and power amps for each set of front speakers.

Does a person run the subs and fronts separately, or are the subs and fronts done at the same time? If they are ran separately on REW, does it matter whether you EQ the Subs first versus the fronts first?

Again, thanks for your answer to my original post in this thread on connections. It's going to take me a bit to get back up to speed on all of this, and I appreciate the help.

Regards,
Kix


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

Kix, I apologize for “jumping the gun” on your other thread and not reading it carefully. I’ve re-opened it and will respond to the questions in the second part of your second post there. I’ll modify my original post, so there won’t be an e-mail notification.



Kix_N_Grins said:


> Hi Wayne,
> 
> Thanks for the welcome, and thanks for answering my question above. What you're saying makes sense to me. Do they sell "low frequency" parametric equalizers that have 4-6 filters that focus on the 20-120Hz range (or thereabouts)? It's been about 25 years since I moth-balled my stereo and I'm just not up-to-date on the new equipment that's come out over that time.


Most people use pro-audio parametric EQs for equalizing their subwoofers. They aren’t specifically dedicated to the low frequencies, but their filters can be set anywhere in the frequency spectrum, so if need be all the filters can be dedicated to the low end. 

There have been a few home audio companies in recent years that noticed the trend of home theater buffs using pro audio EQs and came out with dedicated subwoofer equalizers, but most have been discontinued. I guess they found out that the market wasn’t as big as they thought. Only one of them remains, the DSPeaker Antimode.

Regards,
Wayne


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## Kix_N_Grins (Feb 14, 2015)

Hey, no problem on the other thread. I used to moderate the MSN Money boards for a few years in the early 2000's, and understand how things can happen. In hindsight, I probably shouldn't have opened two threads with nearly the same introductory first paragraph.

But thanks again for the info. It's much appreciated. With the flexibility that pro-EQ's have that you're describing, I can understand why they'd be favored. I checked out the DSPeaker Antimode EQ. It looks nice, but might be over-kill in my case. I think I'm going to wait until I finish reading the REW EQ Wizard Help chapters, see what things look like on my subs/fronts using REW, and then figure out how to move forward on the sub equalizer.

I guess your answer did raise one more question, since I know absolutely nothing about pro audio equipment (aside from the connectors/outputs being different than home audio). Is it possible to inter-mix home and pro audio via some type of converters, or is it pretty much all one way or the other?

Thanks for helping/teaching,
Kix


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

No converters needed as a rule, just cables with RCA connectors on one end (i.e. for the consumer gear) and 1/4” or XLR on the other end (for the pro gear).

The only exception would be in the case of pro amps. Some receivers don’t generate enough voltage from their pre-amp outputs (in other words, the signal isn’t hot enough) to drive the amp to maximum output. The solution in that case is some kind of external signal booster. These cases seem to be fairly rare, though.

Regards,
Wayne


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## Stroh (Sep 14, 2010)

Wayne could you explain the signal booster a little more please, I think I just ran into this problem.


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

It’s a powered device that connects between the receiver and amplifier. The most common one used these days is the ART Clean Box. Just keep in mind that any signal boosting device will increase background noise as well as signal level. Not a big concern with subwoofers, but it definitely is for the main channels. See more in my article on gain structure, which you can find in my signature.

Regards,
Wayne


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## Stroh (Sep 14, 2010)

Thanks so much!


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## Kix_N_Grins (Feb 14, 2015)

Well, I bought my first piece of pro-audio gear this week. Actually bought two, but only received one so far. After you mentioning most people use pro-equip for equalizing their subs and reading your equipment review, I got a couple of the Yamaha YPD2006's.

I have two Velodyne HGS10 subs that are currently connected to my AVP using a Y cable. So my question is, can I use one YPD2006 for both subs? If I do, should I connect the Y cable between the equalizer and subs and use the equalizer as a mono 12 band (both subs getting the same signal)? Or should I use the Y between the AVP and equalizer, then separate cables (L & R) from the EQ to the subs, and using stereo 6 band?

Thank in advance for any help,
Kix


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## gdstupak (Jul 13, 2010)

Kix_N_Grins said:


> When equalizing a room:
> From what I've read so far, the emphasis on room equalization is on the Subwoofers and Fronts. I have a 7.1 system, and I'm wondering why it isn't important to equalize the center channel, surrounds and rear speakers?
> Kix


 Always EQ all speakers involved in the system. EQ'ing the main speakers and not EQ'ing the center/surround speakers will make them sound different which is very bad.



Kix_N_Grins said:


> When using REW:
> I'm using two left front speakers and two right front speakers, one set for lower-end freq. range and one for higher end. When I run REW to equalize them, should I EQ both left speakers at the same time, or should I EQ one left speaker first and then the second left speaker? I do have a separate equalizers and power amps for each set of front speakers.
> Kix


 I am not a professional, this just comes from many years of experimentation, so others may disagree with this...
My system is run very similar to yours, I have main full range speakers and subs that I run together instead of connecting the subs to the separate LFE channel. 
The main/center/subs all have individual equalizers. First I EQ all speakers separately to get them as flat as possible. This gets the EQ settings close to where they need to be but some tweaking needs to be done to get the main speakers to match properly with the subs. The final EQ'ing is done with the mains and subs all playing together so I can blend the low frequencies. If the mains and subs are not EQ'ed together, then the phase alignments/misalignments will cause bumps and dips.

A note on phase control... some believe that if your subs are out of phase with your mains, you simply turn the sub's phase control knob to make them match. Well it's not as simple as the whole sub is out of phase with the mains. In reality some frequencies will be in phase and other frequencies will be out of phase, adjusting the sub's phase control will just change which frequencies will be in phase and out of phase.


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## Kix_N_Grins (Feb 14, 2015)

Thanks or the reply!


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

Kix_N_Grins said:


> I have two Velodyne HGS10 subs that are currently connected to my AVP using a Y cable. So my question is, can I use one YPD2006 for both subs? If I do, should I connect the Y cable between the equalizer and subs and use the equalizer as a mono 12 band (both subs getting the same signal)? Or should I use the Y between the AVP and equalizer, then separate cables (L & R) from the EQ to the subs, and using stereo 6 band?


Typically you want to EQ all subs as a single entity. After all, that is the way you hear them, not each separately. So, a single set of filters for both. No “y” cable needed, the Yamaha will split the signal for you, if you use one of the “Mono 12-Band” memory settings. You’ll need to check the Utility menu to see which input is assigned for use (L or R), but it will send that input to _both_ outputs.

If for some reason you want separate filters for each sub, you will need to use your “y” cable. 

Regards, 
Wayne


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## Kix_N_Grins (Feb 14, 2015)

Thanks for the reply, Wayne. 

Taking this one step further, if it's found that only 6 (or less) bands are needed to equalize the subs, is it possible in stereo mode to use one channel for EQ'ing the subs and the other channel for EQ'ing a center channel (providing 6 or less bands are need for it)?

Thanks again for the help.

Kix


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

Yes, you could certainly do that. It would be uncommon to need more than 6 bands for the subs anyway. :T

Regards,
Wayne


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## Kix_N_Grins (Feb 14, 2015)

That's awesome!!! The two Yamaha's shaved 7" of total height from my stack of amps/EQs, while also adding an EQ for my subs. Now I'll be able to use my early 1990's oak cabinet again. I thought I was going to have spend some serious $$ for a new quality cabinet.

I'm going to use one of the Yamaha's to replace my front SAE 2800 EQ (2" vs 9" H). I'll use the other to replace my center Rolls REQ131 EQ and share between center/subs (2" vs 2"). 

Found a user manual on-line for the YDP2606 and now just need to learn how to use it.


Thanks for your help Wayne!!!


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## Kix_N_Grins (Feb 14, 2015)

Reading through the YDP2006 manual, and I found one reason for using a "Y" cable between AVP and EQ and EQ'ing left and right subs independently. The EQ has built in time-delay. If my subs end up in being placed at different distances from MLP, I can add some delay to the closest sub. The Rolls REQ131 that I was going to remove is only 2" high. I think I'll leave it as-is for now. I can always just use two shelves instead of three and still get everything squeezed into the cabinet. If I don't need the separate time-delays on the subs, I'll just remove the REQ131 and re-wire at that point in time.


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