Author Topic: 2 Channel with Sub - optimum setup  (Read 11455 times)

ik632

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2 Channel with Sub - optimum setup
« on: January 24, 2008, 07:19:15 AM »
So, I've got the new/old receiver back and running but I have a new issue. I'm using Bose 201 with a Klipsch KSW10 sub to reinforce the bottom end. When I had it hooked up to my new technology HK receiver there was a dedicated sub output which varied with volume control of the receiver (as well as input signal change when I changed the SB volume). Now, I don't have a remote for the receiver and I'm using the SB for primary volume control. I have the sub hooked up to one of the tape outputs currently and it seams to work pretty well for SB use (using the volume control on the SB and keeping the amp set at one point). My problem is that I also use a tuner and when using that, the volume level of the sub does not change because it's hooked to the tape out.

After looking at the sub a bit more I noticed that it also had high level inputs so technically I could hook it up to the speaker b outputs of the receiver and have the benefit of level control from preamp or SB. My question for you guys is; is this a kosher setup and could I have any adverse affects connected this way? The sub has it's own internal amplifier, so the high level signal is just for signal and it won't be pulling much power from the amp. It seams the least elegant solution to this problem though,

miklorsmith

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Re: 2 Channel with Sub - optimum setup
« Reply #1 on: January 24, 2008, 07:31:28 AM »
Ah yes, the solution that leads to a problem.  Zis ees extreeemly common.   :D

I might be wrong, but I'm guessing the high-level inputs on the sub are just that - speaker level, bypassing the internal amp which runs solely off the line (low) level feed.  Somebody please correct if I'm wrong.  In any event, taking a speaker-level feed and reducing to line level then re-amplifying to power the sub is not ideal.

If true, this would mean you'd need another amp which would need its own line input and you're right back where you started.

If you're using your SB for volume, try an RCA splitter out of the SB where one output goes to the amp and the other to the line inputs on the sub.  I've used these in the past with mixed results.  If the SB has sufficient output, it will be able to drive both "amps".  I don't think there's any easy way to predict how it will sound but you're not in danger of blowing anything up, so give it a try.

I have an old Audiolab integrated that will power its own speaker terminals and also include a variable-volume RCA out for outboard subbing - a nice feature.

Side note on using the SB volume - try to tailor the receiver volume so you're using the SB above 80%.  Below that (according to Slimdevices) the digital attenuation starts having deleterious effects on sound quality.

Give 'er a go and let us know what you find.
« Last Edit: January 24, 2008, 07:34:40 AM by miklorsmith »

ik632

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Re: 2 Channel with Sub - optimum setup
« Reply #2 on: January 24, 2008, 07:47:51 AM »
The way you described with using a splitter off of the SB is almost like I have it now. The tape outputs are not level controlled by the volume of the integrated amp, so when I turn it up with the big shiny knob the level going to the sub doesn't change. However, when I change the SB volume, I get attenuation of the level going to the sub.

I just need to figure out how to get the tape output level to vary with the volume and I'm set.

Now, my other issue is that when I have the SB above 80, I can't turn the volume on the amp up past 1 without it being too loud. It's not a problem when I want to listen to things loud, but at dinner/background music levels, I have the volume setting just a wisker above 0.

Offline Carlman

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Re: 2 Channel with Sub - optimum setup
« Reply #3 on: January 24, 2008, 09:33:09 AM »
I think your A/B speaker outputs are the only solution available to have consistently variable output to both the speakers and sub.  There's no way to make the tape outputs variable with the preamp section... and if there are no variable outputs (pre-outs) then the circuitry just doesn't exist. 

Also... you could install a graphic eq and adjust volume with the equalizer.. and then you'd have 3 volume controls (SB, receiver's pre, and EQ).

Now if you really wanted to get your hands dirty... and risk it all on the big prize... ;)  You could try to find the preamp out section of the receiver, and tap into that to make a set of preamp-outs.  I don't know how to do this but I would think it'd be possible.

I don't see that there would much of a detriment using the method you've already considered.  Let your ears be the judge.  I would even consider running your A-channel to the sub and then running the output of the sub to the speakers to experience what the crossover does.  It won't cost anything to try.

-C
« Last Edit: January 24, 2008, 09:35:21 AM by Carlman »
I really enjoy listening to music.

Offline rollo

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Re: 2 Channel with Sub - optimum setup
« Reply #4 on: January 24, 2008, 09:37:17 AM »
   Try connecting the sub from your speaker terminals with speaker wire. Or directly from speaker output from receiver. Your gonna be suprised. Run the speakers full range and dial the sub in as required. Then put on a bass heavy recording [ use Ab on CDP remote to play approx. 30 seconds and set on repeat mode ] and determine proper phase [ polarity switch back of sub ].  Then be prepared for some kick ass bass.
    You should be in like Flynn. Tighter, lower and most important better focused. No yopu won't harm the amp or sub.

rollo
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miklorsmith

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Re: 2 Channel with Sub - optimum setup
« Reply #5 on: January 24, 2008, 09:49:51 AM »
The problem, if there be one, of using the speaker-level outs in the receiver is loading it down will tax the amp further.  This may or may not be a concern.

ik632

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Re: 2 Channel with Sub - optimum setup
« Reply #6 on: January 24, 2008, 10:15:44 AM »
I sent Klipsch an e-mail to find out what impedance will be seen by the amp when using this with A going to the left/right and B going to the sub. Also, the speaker inputs on that sub are only inputs, the amplification is separate so the amp shouldn't be working too hard, other than whatever load it sees.

I'll give this a shot this evening when I get home. Wife's out of town, so I can play as loud as I want :D

Offline richidoo

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Re: 2 Channel with Sub - optimum setup
« Reply #7 on: January 24, 2008, 12:11:31 PM »
I'm pretty sure your sub's high level inputs are used to drive the internal power amp. This is the best way to use a sub, with high level inputs, because your sub and speakers are receiving the same exact signal. It is said that the PRAT is better this way...  :roll: You have to try and see.  The receiver will send voltage only to the sub which will have a high input impedance, so it won't effect the sound of the BOSE sats.

The grit of the SB digital attentuator is not audible until you get down around 70 on a very high resolution system. 1 bit is thrown away for each 6dB of attenuation. If you are using mp3s, don't even worry about it. You can play a wav file with the Rx turned up loud and the SB turned down to 10 and compare to the reverse. Use a track with pretty tones, although even thrash will sound like crap at 10 when signal sent to DAC is reduced to 8 bits (telephone quality). Listen for the grit and blurred treble.

Also experiment with just sending one channel to the sub instead of both. On pop/rock the bass channels are usually almost identical, because bass instruments are almost always put in the center. The advantage can be seen when you count how many drivers the sub has, compared to the sats. ;)  Bass will be noticeably blurry when you sum the left and right signals in a track which has any appreciable stereo separation at low freqs, like jazz and classical, and some rock too. With the Bose sats you will probably want to play the sub up to a kinda highish crossover point, where you will find more and more stereo separation as you go up, and where your ears become more and more sensitive to blur and location. If the bass is located between the sats, you will not notice only one channel bass. Worth a try.

Wife's out of town, so I can play as loud as I want :D
Party at Nicks!!!!   :D

ik632

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Re: 2 Channel with Sub - optimum setup
« Reply #8 on: January 26, 2008, 12:41:35 PM »
Ok, got the mains hooked up to speaker A and the sub connected to speaker B. I have to say that I'm relatively surprised by the sound quality as you guys mentioned. Still needs some tuning, but I think it will work.

Offline richidoo

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Re: 2 Channel with Sub - optimum setup
« Reply #9 on: January 26, 2008, 05:01:55 PM »
That's great! Tuning a sub can be tricky for music, but you'll get it.

In contrast to your immortal Pioneer, I had a funny experience today with a new Rx. I helped a friend setup his HT. He has a new Yammy Rx, 100wpc classD's. We got it all hooked up, heard some music from all speakers, went to program the Rx, by the time I exited the menu the left rear channel went dead and never came back. Brand new!

EDIT: Neighbor reports it was the in wall wiring that is intermittant faulty, so Yamaha was blamed prematurely. Sorry!
« Last Edit: January 28, 2008, 04:12:35 PM by richidoo »

ik632

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Re: 2 Channel with Sub - optimum setup
« Reply #10 on: January 27, 2008, 09:19:58 AM »
I guess the nature of electronics is to break right away or after 30 years, but not usually in the middle.  8)

Offline rollo

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Re: 2 Channel with Sub - optimum setup
« Reply #11 on: January 28, 2008, 01:42:51 PM »
ROCK ON. Viva la Bass !

rollo
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