Is it possible to drive 2 subs from a 7.1 receiver? - AVS Forum
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post #1 of 12 Old 09-23-2012, 07:46 AM - Thread Starter
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I have a 7.1 receiver in my theater and would like to add a second sub. It's not worth replacing my receiver though, so I'm wondering if there's a way to add a second sub using my 7.1 receiver.
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post #2 of 12 Old 09-23-2012, 07:51 AM
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yessir...just grab a y-splitter at radio shack, plug into your "sub out" on yer receiver and plug yer 2 subs into the other end
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post #3 of 12 Old 09-23-2012, 08:10 AM - Thread Starter
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Thanks Luke for the quick response. Do you know if there's any loss of quality in doing that?
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post #4 of 12 Old 09-23-2012, 08:11 AM
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There's no loss of quality splitting the signal to two subs.
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post #5 of 12 Old 09-23-2012, 08:12 AM - Thread Starter
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Wow, you guys are quick. Thanks for the help.
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post #6 of 12 Old 09-23-2012, 10:34 AM
 
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What I'm not able to find is pre-out voltage specs. My understanding, if you're dividing up signals, then that's just what you're doing, dividing up the line signal strength.

My experience is with household current as the capacity of a circuit is set by the circuit breaker. If all things being equal, one has only so much amperage which can be drawn on a 20A breaker; momentary peak values aside.

Maybe somebody who's in the know can add some insight to what happens to the signal strength when the line voltage is divided up by the Y-splitter and how this might affect the final dB output of two subs as opposed to the un-split signal of using one sub.
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post #7 of 12 Old 09-23-2012, 09:59 PM
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In parallel you divide current, theoretically, not voltage. But what happens is that the two roughly 1000 ohm input impedances of the two subs, when connected in parallel, look like one 500 ohm input impedance to the preamp. At 2 volts, it's the difference between .002 and .004 amps.
Either way, though, a person will use the sub level setting in the receiver to cause the receiver to output the appropriate voltage to obtain a balance between subs and everything else. A typical fix for auto-on subs that won't wake up soon enough is to use a Y cable to connect both left and right inputs (if available) so a little more signal gets to the sub . . .
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post #8 of 12 Old 09-24-2012, 10:15 AM
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What he said.... Also even some of the "7.2" receivers just have a Y splitter on the inside of the AVR. That's how my Onkyo 808 works. The receiver doesn't know if I have 1 or 2 subs hooked up cuz its just the same signal going to both subs. Now newer or higher end AVRs with Audyssey XT32 that EQ both subs seperately actually have 2 different sub pre outs so the correct Room EQ can be applied to the correct sub.

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post #9 of 12 Old 09-24-2012, 11:06 AM
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strange replies.

I thought that when a receiver has 7.2 (2 sub capability), when you do the room correction run with Audessey or the like, it actually sets separate specs for each sub and thus the sound is WAY better. Am I off here?

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post #10 of 12 Old 09-24-2012, 11:18 AM
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There are different "flavors" of Audyssey MultEQ processing, but I believe that in order to EQ more than one sub (using an Audyssey product), you need an AVR/processor with Sub EQ HT:
Quote:
Audyssey Sub EQ HT ensures that the level and delay for each subwoofer is correct before integrating them into the equalization solution.

This new technology is a huge leap forward from the days when adding an additional subwoofer was accomplished by adding a y-chord to the subwoofer output of an AVR. Now, the process is automated and produces better results because it is fully integrated with MultEQ. The process takes only a few minutes and results in rich, full bass for everyone in the room.
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post #11 of 12 Old 09-24-2012, 04:39 PM
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Quote:
Originally Posted by Pianist718 View Post

strange replies.

I thought that when a receiver has 7.2 (2 sub capability), when you do the room correction run with Audessey or the like, it actually sets separate specs for each sub and thus the sound is WAY better. Am I off here?

yes, you are off... not your fault though, it's easy to be confused by marketing specs.

the truth is that the VAST majority of receivers that call themselves "7.2" are really just 7.1 units with an internal y-splitter feeding two identical sub outputs. The "point 2" part just designates that there are two outputs, but they receive the same signal.

among Audyssey equipped units ONLY those with MultEQ XT32 will have a "true" dual sub calibration, this is branded as "SubEQ HT" in the marketing specs. Note however that even these waters have been muddied by the introduction of the Onk 818, which has XT32 but does NOT have SubEQ HT.

all that being said, if you have the wherewithal to optimize your dual subs prior to running Audyssey, you can still achieve excellent results without this "dual sub calibration" software. The SubEQ HT just makes the job easier by level matching and time aligning them for you.
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post #12 of 12 Old 09-25-2012, 07:42 AM
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Quote:
Originally Posted by batpig View Post

yes, you are off... not your fault though, it's easy to be confused by marketing specs.
the truth is that the VAST majority of receivers that call themselves "7.2" are really just 7.1 units with an internal y-splitter feeding two identical sub outputs. The "point 2" part just designates that there are two outputs, but they receive the same signal.
among Audyssey equipped units ONLY those with MultEQ XT32 will have a "true" dual sub calibration, this is branded as "SubEQ HT" in the marketing specs. Note however that even these waters have been muddied by the introduction of the Onk 818, which has XT32 but does NOT have SubEQ HT.
all that being said, if you have the wherewithal to optimize your dual subs prior to running Audyssey, you can still achieve excellent results without this "dual sub calibration" software. The SubEQ HT just makes the job easier by level matching and time aligning them for you.


Awesome post and very informative.
I was looking at the Onkyo 818 and saw how everyone was praising it so much. Good info. Thanks.


Checkout my system in signature ..... what would you upgrade next?

I am thinking of going Emotiva XPA-3 (for my front speakers) and getting a new but cheap receiver that has Audyssey MultEQ XT32 (to help deal with my room acoustics ... bare walls) and to allow me to have custom presets ... one for music and one for movies. Also .... options like wireless, etc.
suggestions?

Denon AVR 4311ci, Ascend Sierra-1 NrT, Ascend HTM-200 (surrounds), Rythmik F12, Panasonic TH50PX60U, Samsung BD ES6000, Denon DVD-2910 SACD/DVDa, Monster HTS 5100 MKI, Monster Z2 Biwire, Logitech Harmony One, Sennheiser HD600, Schiit Modi/Vali
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