Connecting passive subs..and their placement...and: which rear surrounds?

A

Amarcarni

Audiophyte
Hi all, I just want to be sure I am doing this correctly!

These are my two receivers:
Yamaha RX-V2500
Onkyo TX-SV828THX
My speaker system is Jamo THX One.

The Yamaha is my main receiver, the Onkyo powers my subs.

Is this the correct way to connect the subs:
  • Subs are connected to the Onkyo "Front Speakers A" with speaker cable.
  • Yamaha's "Subwoofer Pre Out" is connected to Onkyo's "CD-in".
    • Now, must I choose between CD L or CD R or should I use both inputs, thereby using a male-to-double-male rca-cinch cable?
      • If I use only one channel (L or R (if yes, is there a preference?)), should I turn the balance dial on the Onkyo all the way to the corresponding side and set the Onkyo to mono?
  • On the Onkyo input selection (front) I must choose "CD".
    • Now, how high should I set the main volume on the Onkyo?

  • According to the audioholics recommendation I will place one sub in the middle of the front wall and one in the middle of the back wall.
    • That being said, this will cause a delay from the front sub, as it will be further away from me than the back sub. o_O Is this a problem, and if yes, how can I correct this?

  • And finally, I would like to complement my speaker setup with two back-surrounds. My present side surrounds are dipoles. Are there speakers you could recommend?


Thanks very much!!
 
WaynePflughaupt

WaynePflughaupt

Audioholic Samurai

Hi all, I just want to be sure I am doing this correctly!

These are my two receivers:
Yamaha RX-V2500
Onkyo TX-SV828THX
My speaker system is Jamo THX One.

The Yamaha is my main receiver, the Onkyo powers my subs.

Is this the correct way to connect the subs:


    • Subs are connected to the Onkyo "Front Speakers A" with speaker cable.
    • Yamaha's "Subwoofer Pre Out" is connected to Onkyo's "CD-in".
Yes, that is the correct connection scheme.


Now, must I choose between CD L or CD R or should I use both inputs, thereby using a male-to-double-male rca-cinch cable?
You mentioned “subs,” meaning more than one. If that’s the case and they’re connected to the Left and Right side of the “Speaker A” outputs, then yes you need to use a splitter to get the signal on the both Left and Right channels of the Onkyo’s CD input.


If I use only one channel (L or R (if yes, is there a preference?)), should I turn the balance dial on the Onkyo all the way to the corresponding side and set the Onkyo to mono?
Not relevant – since you’re using two subs you need both channels. Keep the balance control straight up.


On the Onkyo input selection (front) I must choose "CD".
Now, how high should I set the main volume on the Onkyo?
High enough so that the subs blend with the main speakers. Having the subs 10 dB louder is a good place to start, with fine tune adjustments from there. You’ll need a sound level meter for this, if you don’t have one you should consider getting one. If not, just adjust the subs to a level you’re comfortable with. You might start with the subs all the way down, and playing a familiar music track, slowly turn them up until they are heard well.


According to the audioholics recommendation I will place one sub in the middle of the front wall and one in the middle of the back wall.
I once took measurements of different locations in my room some years back, and middle-of-wall got worst results. Absolutely abysmal frequency response. Typically the best location is in or near a corner, with parametric equalization to smooth out any “hot” or peaking frequencies.


That being said, this will cause a delay from the front sub, as it will be further away from me than the back sub. Is this a problem, and if yes, how can I correct this?
Yes, if you put them in two asymmetrical locations, there will be a delay issue. There’s nothing you’ll be able to do about it with your present equipment. You can avoid the problem by putting them both in the same location.


And finally, I would like to complement my speaker setup with two back-surrounds. My present side surrounds are dipoles. Are there speakers you could recommend?
Another pair of the Jamo LCR One would work best, as they will be a perfect match for the other speakers in your system.

Regards,
Wayne A. Pflughaupt
 
A

Amarcarni

Audiophyte
Thanks very much, Wayne!
So I may need to reconsider placing the subs as above written. I could also place the subs diagonally.
My room will be rectangular, roughly 9.8 x 18.2 feet.
The distance from my sitting area to the front wall will be approx. 12.3 feet.
This means I could place one sub diagonally behind me in the corner of the room and the the other sub equidistant diagonally in front of me.

Basically I could choose from any of the four options on the audioholics page named "Subwoofer Connection Guide For A Multi Subwoofer System" (I can't post the link yet). In your own experience, which do you think is best?


Ah, and about the rear surround speaker, you are saying dipoles or bipoles are not good, so I should better choose a monopole speaker?
 
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WaynePflughaupt

WaynePflughaupt

Audioholic Samurai

Unfortunately Gene didn’t give much in the way of practical reasons for any of his preferred locations. What you want with sub location is the highest output (SPL), best frequency response, and the lowest extension. Typically it’s impossible to get all three (although not always). However, you can typically get the best output and lowest extension in a corner, where there are no openings in the wall in either direction. Both output, extension and response suffer with center-of-wall placement.


Adding a second matching sub in the same corner gets (IIR) a 6 dB increase in output, while placing in a symmetrical corner (e.g. both in front) gets a 3 dB increase in output. There’s typically at least one peak frequency to deal with, which is an easy fix for a parametric equalizer. Moving the sub a few feet down the wall away from the corner can sometimes tame the peak with minimal penalty to output and extension.

At the end of the day however, placement is a guessing game without taking measurements with a freeware program like Room EQ Wizard. If the hardware outlay and learning curve is daunting, it’s easy (but time consuming) to make response graphs with a sound level meter, 1/6-octave sine wave test tones and graph paper.


Ah, and about the rear surround speaker, you are saying dipoles or bipoles are not good, so I should better choose a monopole speaker?
If you’re talking about the back-wall speakers in a 7.1 arrangement, monopoles are better.


Regards,
Wayne A. Pflughaupt
 
A

Amarcarni

Audiophyte
Thanks again Wayne. Is it possible to make a generalization as to where the two ideal spots are for two subwoofers in a rectangular room? You said a room corner is good, so two subs along the long wall, short wall, or even diagonally?
 
A

Amarcarni

Audiophyte
Guess it's really hard to find a consensus here....on the THX-page, they also recommend to place two subwoofers in the middle of opposing walls....is it all trial and error, or can I not follow any guidelines? o_O
 
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tyhjaarpa

tyhjaarpa

Audioholic Field Marshall
Thanks again Wayne. Is it possible to make a generalization as to where the two ideal spots are for two subwoofers in a rectangular room? You said a room corner is good, so two subs along the long wall, short wall, or even diagonally?
There is no answer for best spot in room as every room is different acoustically. Your best bet is doing a sub crawl and find your best spots.
 
A

Amarcarni

Audiophyte
Thanks, yeah, I guess you are right, just, it's kind of hard to do a crawl, when setting up two subs, instead of one.
 
TheWarrior

TheWarrior

Audioholic Ninja
Thanks, yeah, I guess you are right, just, it's kind of hard to do a crawl, when setting up two subs, instead of one.
More than crawling, INCHES make a difference. Be very critical of what you are hearing, listen for when bass sounds boomy, and when it sounds thin. Your aim is tight and controlled!
 
A

Amarcarni

Audiophyte
Am surprised that inches should make such big differences, the wavelength of low frequencies being so wide!
 
TheWarrior

TheWarrior

Audioholic Ninja
Am surprised that inches should make such big differences, the wavelength of low frequencies being so wide!
This is true, but its the interaction of room boundaries that shapes the sound in such a way. Especially for corner loaded subs (meaning the corner of a room), this is an easy way to increase in-room bass response, but it can very easily 'bloat' the bass and make it sound boomy. From the listening position you should be able to discern 3-6 inch movements.
 
A

Amarcarni

Audiophyte
How about setting the subs away from the corners, but equidistant to my sitting point, diagonally to me? (left front, back right, for example)
 
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TheWarrior

TheWarrior

Audioholic Ninja
How about setting the subs away from the corners, but equidistant to my sitting point, diagonally to me? (left front, back right, for example)

Lol!

Try it, let us know what you think!
 
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