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post #1 of 15 Old 08-08-2014, 09:52 AM - Thread Starter
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Y-Splitters & Subwoofers

Im sure this has been discussed thoroughly so I apologize but there are so many articles I could literally read for hours upon hours. I have a onkyo tx-nr609 which is a 7.1 receiver with two subwoofer outputs, and according to the manual the same signal is output over each. I have a klipsch sw-450 and a nxg nx-bas-500 for subs. Both with a LFE input as well as a R & L input. I have plenty of Y splitters and sub cables so with that being said what is the most optimum choice of connection? At one time I had a Y splitter from a single output of the receiver running to both subs with a Y splitter on each going into both L&R of each sub, as well as both outputs from receiver separately to subs using both inputs, basically any combination imaginable as I already have splitters. Should I use a single output from receiver split to each LFE of subs or use both inputs/outputs or toss em both through the tv and get a theater in a box
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post #2 of 15 Old 08-08-2014, 11:30 AM
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In general, the LFE input bypasses the subs internal low pass crossover. Even if the frequency is turned all the way up, this input should be superior if you are using the AVR to select the crossover frequency (which I'm sure you are). I believe that the LFE input also corrects for the 10dB boost needed for surround decoding (other correct me if I'm wrong). The R / L are just there for stereo input and use with legacy equipment that didn't have an LFE output.

Since the signal is split inside the AVR, it shouldn't matter if you use one output and split it further away - this would just be a matter of convenience. If the two subs were in opposite directions, I would use both outputs. If in the same direction, I would use one cable to the first sub, split the signal there, and run another cable to the second sub.
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post #3 of 15 Old 08-08-2014, 11:34 AM - Thread Starter
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Quote:
Originally Posted by mtn-tech View Post
In general, the LFE input bypasses the subs internal low pass crossover. Even if the frequency is turned all the way up, this input should be superior if you are using the AVR to select the crossover frequency (which I'm sure you are). I believe that the LFE input also corrects for the 10dB boost needed for surround decoding (other correct me if I'm wrong). The R / L are just there for stereo input and use with legacy equipment that didn't have an LFE output.

Since the signal is split inside the AVR, it shouldn't matter if you use one output and split it further away - this would just be a matter of convenience. If the two subs were in opposite directions, I would use both outputs. If in the same direction, I would use one cable to the first sub, split the signal there, and run another cable to the second sub.
Thank you, also technically since avr is sending identical signals to both outputs I shouldnt need to worry about phase for each sub if I were using both outputs? I read a article suggesting splitting 1 output to insure subs are receiving same signal as well rule out any phase issues
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post #4 of 15 Old 08-08-2014, 11:53 AM
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Whether or not you will need to adjust phase depends on sub placement. In general, if you have one in the front of the room and one in the back, the one in back should be set to "180".

The easiest way to know if your subs are "in phase" is to play pink noise and adjust phase on one of the subs until you get the highest SPL at the MLP.
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post #5 of 15 Old 08-08-2014, 02:20 PM
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The phase control of the sub in the front of the room will probably be set closer to "0" - but you should use the phase control of both subs to blend with the main left / right speakers at the crossover frequency - the phase of both subs depend completely on where it they placed in the room and the room itself.
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post #6 of 15 Old 08-08-2014, 02:21 PM
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The easiest way to know if your subs are "in phase" is to play pink noise and adjust phase on one of the subs until you get the highest SPL at the MLP.
That sounds right, but honestly there is no excuse for any of us not to be doing computer analysis of our room acoustics. The software REW (Room EQ Wizard) is free when you register at Home Theater Shack and now that there are USB mics the setup is ridiculously easy. Plus there is an entire thread on AVS to help figure it out.

MiniDSP UMIK-1 USB Measurement omnidirectional microphone
Dayton Audio UMM-6 USB Measurement Microphone

I am learning this right now as well and will be putting my new knowledge to use to improve my sub locations and improve my room acoustics - my current investment is less than $100 and I fully expect it to be the biggest improvement to my system regardless of cost. Just knowing where your issues are (even if you don't have the right kind of room or space to fix them) will help you get the most out of what you do have.
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post #7 of 15 Old 08-08-2014, 02:24 PM
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This should be a "sticky" thread, but it isn't yet - this is the REW setup and help thread:

Simplified REW Setup and Use (USB Mic & HDMI Connection) Including Measurement Techniques and How To Interpret Graphs
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post #8 of 15 Old 08-08-2014, 02:41 PM
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Quote:
Originally Posted by mtn-tech View Post
The phase control of the sub in the front of the room will probably be set closer to "0" - but you should use the phase control of both subs to blend with the main left / right speakers at the crossover frequency - the phase of both subs depend completely on where it they placed in the room and the room itself.
If you have a sub or subs up front they should always be set to "0". If you then get all subs in phase with each other, the distance setting in your AVR will take care of getting them in phase with the mains.

Quote:
Originally Posted by mtn-tech View Post
That sounds right, but honestly there is no excuse for any of us not to be doing computer analysis of our room acoustics. The software REW (Room EQ Wizard) is free when you register at Home Theater Shack and now that there are USB mics the setup is ridiculously easy. Plus there is an entire thread on AVS to help figure it out.

MiniDSP UMIK-1 USB Measurement omnidirectional microphone
Dayton Audio UMM-6 USB Measurement Microphone

I am learning this right now as well and will be putting my new knowledge to use to improve my sub locations and improve my room acoustics - my current investment is less than $100 and I fully expect it to be the biggest improvement to my system regardless of cost. Just knowing where your issues are (even if you don't have the right kind of room or space to fix them) will help you get the most out of what you do have.
I'm very familiar with REW and have been measuring my room for almost a year now...not everyone is willing to go down that rabbit hole though. However, I do agree that it's the single best "upgrade" you can do to your system (if you already have a quality sub).
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post #9 of 15 Old 08-08-2014, 03:43 PM
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If you have a sub or subs up front they should always be set to "0". If you then get all subs in phase with each other, the distance setting in your AVR will take care of getting them in phase with the mains.
I'm pretty sure that in most AVRs the distance setting in the speaker setup only adjusts time delays to each speaker output to maintain coherence. But then again most people aren't even doing that manually any longer - auto room EQ's adjust the distance automatically and some of them also adjust the phase of the subwoofers. If the OP is using an AVR with Audyssey Multeq XT he should be leaving both sub phase settings at "0" - right?.

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I'm very familiar with REW and have been measuring my room for almost a year now...not everyone is willing to go down that rabbit hole though. However, I do agree that it's the single best "upgrade" you can do to your system (if you already have a quality sub).
I'm sure that most on AVS are familiar with REW - sorry, that comment wasn't directed at you but was for the benefit of the OP. The old analog mics and all of the additional equipment needed to connect them to a computer seemed like a lot of work to acquire and setup, but the new USB mics directly to the computer don't really leave much of an excuse!
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post #10 of 15 Old 08-08-2014, 04:01 PM
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Originally Posted by mtn-tech View Post
I'm pretty sure that in most AVRs the distance setting in the speaker setup only adjusts time delays to each speaker output to maintain coherence. But then again most people aren't even doing that manually any longer - auto room EQ's adjust the distance automatically and some of them also adjust the phase of the subwoofers. If the OP is using an AVR with Audyssey Multeq XT he should be leaving both sub phase settings at "0" - right?.
Correct, if both subs are either up front or both subs are in back. You still need to adjust phase (for highest SPL at the MLP) on one of the subs if they are on opposite ends of the room.

Adjusting distance (delay) in the AVR is not really to maintain coherence, it's to time-align all speakers (including the sub) to the MLP. This has the added benefit of keeping the sub "in phase" with the mains. If you have REW, the "sub distance tweak" can help you get the best transition through the crossover by adjusting the sub distance in the AVR.

An important point - the sub distance set by Audyssey can vary greatly from the actual, physical distance. This is completely normal, but throws a lot of people for a loop when they see it. It has to do with how the sub is interacting with your room.

Quote:
Originally Posted by mtn-tech View Post
I'm sure that most on AVS are familiar with REW - sorry, that comment wasn't directed at you but was for the benefit of the OP. The old analog mics and all of the additional equipment needed to connect them to a computer seemed like a lot of work to acquire and setup, but the new USB mics directly to the computer don't really leave much of an excuse!
Still, regardless of how easy it is now (and I agree!), some people find REW too intimidating, or just plain don't have the time to dedicate to it. I know that I've spent countless hours in the last year running sweeps and staring at graphs....but I don't have kids.
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post #11 of 15 Old 08-08-2014, 09:16 PM - Thread Starter
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Thank you all for advice, I dont have a spl or rew mic, if they arent the same thing, I battled the dual placement for probably 2 months and 4-5 placements and settled on 1 subwoofer on the side wall (was left side but just today switched it to right side due to a air vent causing imaginary sound issues) and the other on the back wall behind main seating arrangement. I currently connected it using both outputs of the receiver to each LFE input of each sub and ran the full audyssey calibration through the onkyo. In 1 article I read the author suggested playing a bass tone and sit in the main viewing area while someone switches the phase from 0-180 and that whichever setting sounded louder that it would be the phase for that sub. With 2 I just muted 1 sub while listening and vice versa. I have klipsch reference rf-62ii for left and right and am hating to have them set to 80hz as suggested, avr sets at 40 after audyssey, is 80 still the way to go or would I need a spl to better balance the curve between subs and mains? Also 1 sub is a front firing and the other is a down firing, both rear ported, would it make any difference as to which I have on the side or rear? Sorry for clueless questions, I swear I thought I was content but that only left my mind to wonder how to make it better
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post #12 of 15 Old 08-09-2014, 06:41 AM
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I dont have a spl or rew mic, if they arent the same thing
A sound level meter is a hand held meter that displays the current SPL and can be a specialized meter or an app running on your smart phone. Obviously a dedicated meter, more so a calibrated one, will be more accurate of the true level, but even a cheap meter or a phone app can give a fair indication of relative (differences in) sound levels. This tells you when the sound is louder or quieter (without trusting our ears and memory which can be unreliable) and can help you decide on the best placement and phase settings for your subs.

The mic, REW and computer actually measure your speaker system response in your room and display it on a plot so that you can compare different placement and settings and see the changes over a wide range of frequencies.

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In 1 article I read the author suggested playing a bass tone and sit in the main viewing area while someone switches the phase from 0-180 and that whichever setting sounded louder that it would be the phase for that sub. With 2 I just muted 1 sub while listening and vice versa.
In years past without expensive, sophisticated test equipment (or today without REW) this was the best way to do this at home, a sound level meter helping with the "sounded louder" part at a single frequency. REW can do this for all frequencies and show you the results.

Automatic room EQ attempts to measure AND correct this all automatically, but many versions don't handle multiple subs. And at bass frequencies, room placement and room treatment (search for "bass traps") can correct issues that any amount of EQ cannot - so you are doing the right thing by getting the best sub placements before running your auto room EQ correction.

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post #13 of 15 Old 08-09-2014, 08:11 PM
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Thank you all for advice, I dont have a spl or rew mic, if they arent the same thing, I battled the dual placement for probably 2 months and 4-5 placements and settled on 1 subwoofer on the side wall (was left side but just today switched it to right side due to a air vent causing imaginary sound issues) and the other on the back wall behind main seating arrangement. I currently connected it using both outputs of the receiver to each LFE input of each sub and ran the full audyssey calibration through the onkyo. In 1 article I read the author suggested playing a bass tone and sit in the main viewing area while someone switches the phase from 0-180 and that whichever setting sounded louder that it would be the phase for that sub. With 2 I just muted 1 sub while listening and vice versa. I have klipsch reference rf-62ii for left and right and am hating to have them set to 80hz as suggested, avr sets at 40 after audyssey, is 80 still the way to go or would I need a spl to better balance the curve between subs and mains? Also 1 sub is a front firing and the other is a down firing, both rear ported, would it make any difference as to which I have on the side or rear? Sorry for clueless questions, I swear I thought I was content but that only left my mind to wonder how to make it better
Adjusting phase with one of your 2 subs muted will accomplish nothing....both subs need to be playing in order to get them in phase with each other.

Along with what mtn-tech said, I'd like to point out that if you have the UMIK-1 mic and REW, you will also have a very accurate SPL meter (built into REW, and the UMIK-1 comes with SPL calibration).
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post #14 of 15 Old 08-09-2014, 08:19 PM - Thread Starter
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Adjusting phase with one of your 2 subs muted will accomplish nothing....both subs need to be playing in order to get them in phase with each other.

Along with what mtn-tech said, I'd like to point out that if you have the UMIK-1 mic and REW, you will also have a very accurate SPL meter (built into REW, and the UMIK-1 comes with SPL calibration).
I plan on getting a spl meter in near future, probably still wrong but I just meant I checked the phase of each separately going off of which setting sounded louder but calibrated with audyssey while both subs were on. The avr I am using now is 7.1 with 2 preouts but same signal on each as well as audyssey only recognizing 1 sub. How much of a benefit would it be to upgrade to a 7.2 avr and if so what are some things I should look for. Ive looked and from what I can tell some of the 7.2s appear the same as my 7.1 in that there are just 2 pre outs with no specific labeling for each. Pioneer, yamaha, onkyo?
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post #15 of 15 Old 08-10-2014, 08:43 PM
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Adjusting phase while only one sub is playing should have little to no effect on SPL. You need to adjust phase with both subs playing.

If you're looking to upgrade AVRs for independent dual sub calibration, you need to look for "Sub EQ". These are the AVRs that calibrate each sub individually. I believe the only Sub EQ AVRs are XT 32 (Onkyo & Denon).

You could also consider a MiniDSP. It will allow you to independently EQ and set delay for multiple subs. But, if you plan on using a MiniDSP, a microphone + REW is pretty much required.
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