Subwoofer setup with 2 channel pre/power...? - AVS Forum
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post #1 of 16 Old 07-02-2011, 11:16 AM - Thread Starter
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Hi all!

My first post so be nice...

I'm buying an MJ Acoustics Reference 200 sub this week and having difficulty working out the best way to connect it to my current setup.

My system is:
Arcam rDac
Rotel RC-1550 Pre
Rotel RB-1552 Power
B&W CM5's
Chord Cadenza's to link and Chord epic speaker cable...

I have an idea of how the setup would be best, but i wanted that confirming...

Thanks in advance,

Nish
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post #2 of 16 Old 07-02-2011, 05:14 PM - Thread Starter
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Maybe i should explain a bit more....

I have three options as far as i'm aware....

- Use the second set of pre-outs on the preamp to connect straight to the sub.
- use the additional four speaker terminals on the power amp and run high level cable into the sub, although i've read that this will half the ohms rating and make the amp work possibly too hard....
-finally (the one i'm thinking of) is pre out from the preamp into the line input of the sub, then output from the sub backinto the power amp before the speakers.

My only issue with the final senario is when i'm listening to music with the sub turned on, will the speakers then loose out a bit of the bottom end or will the sub pass the lower frequencies in?

The only other thing i saw was on the setup guide from MJ, they show a senario by using both high level and rca connections....

So if anyone has any suggestions or advice.....
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post #3 of 16 Old 07-02-2011, 05:49 PM
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Quote:
Originally Posted by DrummerNish View Post

- Use the second set of pre-outs on the preamp to connect straight to the sub.

Could do, but it is tricky to set the LPF in the sub to complement the rolloff of the mains.

Quote:


- use the additional four speaker terminals on the power amp and run high level cable into the sub, although i've read that this will half the ohms rating and make the amp work possibly too hard....

It will not present any additional load on the amplifier. Those speaker inputs on the sub are high impedance. Same as a line input with a resistive divider to scale the signal down.

Quote:


-finally (the one i'm thinking of) is pre out from the preamp into the line input of the sub, then output from the sub backinto the power amp before the speakers.

Best idea. The sub's crossover then makes sure the splice to the mains is smooth.

Quote:


My only issue with the final senario is when i'm listening to music with the sub turned on, will the speakers then lose out a bit of the bottom end or will the sub pass the lower frequencies in?

The speakers will be rolled off where the sub takes over.
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post #4 of 16 Old 07-03-2011, 03:36 AM - Thread Starter
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Cool, looks like i'll need another Cadenza Then

I made a typo in that, sorry - i actually meant to say will i loose out on frequencies in the main speakers when listening to music while the sub is off? I plan on using the sub for games and films mostly so if the sub is off will it pass the rest of the frequencies through to the speakers like 'hdmi through' style devices, or will i just loose out on what ever frequencies are usually present by the sub?

Nish
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post #5 of 16 Old 07-03-2011, 07:59 AM
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Quote:
Originally Posted by Roger Dressler View Post

Best idea. The sub's crossover then makes sure the splice to the mains is smooth.

It should be noted that is your opinion.

Most high end guys would say the best way is to run the high level out of your amplifier as it is best to run your main speakers full range and to only augment their deficiencies with the subwoofer.

This way your entire signal is not degraded by going through the subwoofer before your main amp and so your subwoofer has the best chance for integration by receiving the exact same signal as the main speakers.
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post #6 of 16 Old 07-03-2011, 08:01 AM
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Quote:
Originally Posted by Harrypt View Post

It should be noted that is your opinion.

Most high end guys would say the best way is to run the high level out of your amplifier as it is best to run your main speakers full range and to only augment their deficiencies with the subwoofer.

This way your entire signal is not degraded by going through the subwoofer before your main amp and so your subwoofer has the best chance for integration by receiving the exact same signal as the main speakers.

Most? I do not believe there is a consensus on this, let alone a statistically valid survey. There is room for various (and valid) opinions on this and, fwiw, I do not share yours.

Kal Rubinson

"Music in the Round"
Senior Contributing Editor, Stereophile
http://www.stereophile.com/category/music-round

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post #7 of 16 Old 07-03-2011, 09:38 AM
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Quote:
Originally Posted by Harrypt View Post

It should be noted that is your opinion.

Most high end guys would say the best way is to run the high level out of your amplifier as it is best to run your main speakers full range and to only augment their deficiencies with the subwoofer.

All depends on what those deficiencies are. Lack of bass extension, lack of bass output with low distortion, lack of bass smoothness at the MLP. The optimal solution follows knowing which problems are to be solved.

Quote:


This way your entire signal is not degraded by going through the subwoofer before your main amp and so your subwoofer has the best chance for integration by receiving the exact same signal as the main speakers.

It should be noted that is your opinion.

But the integration will be better when using a proper crossover in this case. Note, the OP has no EQ to otherwise attend to integration issues that arise when running full range speakers with a sub.
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post #8 of 16 Old 07-03-2011, 09:39 AM
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Quote:
Originally Posted by DrummerNish View Post

I made a typo in that, sorry - i actually meant to say will i loose out on frequencies in the main speakers when listening to music while the sub is off? I plan on using the sub for games and films mostly so if the sub is off will it pass the rest of the frequencies through to the speakers like 'hdmi through' style devices, or will i just loose out on what ever frequencies are usually present by the sub?

If your main speakers do not have sufficient bass response for movies, I'd assert they do not have sufficient bass for music. You might not realize that until you hear what's missing.
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post #9 of 16 Old 07-03-2011, 02:00 PM - Thread Starter
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Fair point Roger, i may end up using the sub all the time - will just have to wait and see!


Quote:


All depends on what those deficiencies are. Lack of bass extension, lack of bass output with low distortion, lack of bass smoothness at the MLP. The optimal solution follows knowing which problems are to be solved.

I think what i'm lacking is the physical extension and smoothness of bass at higher volumes. Don't get me wrong, I love my CM5s to bits, but i just want more bottom end for certain cenarios.

I know audio is subjective, but i guess i just wanted to know if it was worth spending another £200 on another stereo interconnect or if i could do it with the highlevel lead supplied/a cheaper mono sub cable for the same or a better result....
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post #10 of 16 Old 07-03-2011, 03:05 PM
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Quote:
Originally Posted by DrummerNish View Post

Fair point Roger, i may end up using the sub all the time - will just have to wait and see!

Let us know!

Quote:


I think what i'm lacking is the physical extension and smoothness of bass at higher volumes. Don't get me wrong, I love my CM5s to bits, but i just want more bottom end for certain cenarios.

How about adding a sub?

Have you measured the response of the CM5s? Do they differ in the LF rolloff -- as may happen in real rooms? If you plan to run them full range, you will benefit from some sort of measuring kit, REW, XTZ, etc., to see how things are knitting together. If you do not have such kit, then the electrical crossover will help achieve good results with less fiddling.

Quote:


I know audio is subjective, but i guess i just wanted to know if it was worth spending another £200 on another stereo interconnect or if i could do it with the highlevel lead supplied/a cheaper mono sub cable for the same or a better result....

I am certain you can achieve the optimal outcome with normal interconnects.

Oh, that's just my opinion.
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post #11 of 16 Old 07-03-2011, 03:10 PM
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Quote:
Originally Posted by Roger Dressler View Post

Best idea. The sub's crossover then makes sure the splice to the mains is smooth.

If a sub has a line in and a line out - then the sub crossover has no affect on the line out. The line out can be used to another sub and is not high pass filtered. Some subs do have an extra high pass filter line out jack.

Subs that have speaker level input and output has the output filtered with the crossover though.
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post #12 of 16 Old 07-03-2011, 03:18 PM
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Originally Posted by Harrypt View Post

Most high end guys would say the best way is to run the high level out of your amplifier as it is best to run your main speakers full range and to only augment their deficiencies with the subwoofer.

This is how my 2ch system has ended up. Speaker level input with subs on 35hz to pick up from where my speakers leave off.
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post #13 of 16 Old 07-04-2011, 12:21 AM
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Quote:
Originally Posted by kiwi2 View Post

If a sub has a line in and a line out - then the sub crossover has no affect on the line out. The line out can be used to another sub and is not high pass filtered. Some subs do have an extra high pass filter line out jack.

Subs that have speaker level input and output has the output filtered with the crossover though.

Actually my sub has a fixed XO (80Hz or 100Hz user selectable) for both the line and speaker level outputs and the manual goes on to suggest connecting the main speakers directly to the amp if you want to bypass this crossover. Otherwise if the sub is off the lower frequency will be cut off. The OP needs to find out how his sub behaves in this regard.

Just shows there are different sub designs and what's best connection for one isn't necessarily always the best for all and may have to be limited by the design of a particular model.

Audiosceptics accept audio trials using 25 people. A recent Oxford study with over 353,000 patient records from 639 separate clinical trials shows for every 1,000 people taking diclofenac or ibuprofen there would be 3 additional heart attacks, 4 more cases of heart failure and 1 death every year.

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post #14 of 16 Old 07-04-2011, 12:59 AM
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Quote:
Originally Posted by kiwi2 View Post

This is how my 2ch system has ended up. Speaker level input with subs on 35hz to pick up from where my speakers leave off.

And doing it this way you get none of the distortion reduction in the mains by the midbass driver having to reproduce the LF which it still is in your set up.
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post #15 of 16 Old 07-04-2011, 03:19 PM
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When someone needs to go away from pure two speaker stereo, all concept of playback system changes. The only useful thing from your old setup is power amp. The rest is pretty much useless and should go. Instead of DAC and preamp you need to get pure digital preamp (both in and out are digital), it will provide you with volume control and source switching. It would be good if it can digitize analog sources for further processing. Then you need bass management device. There are many available in pro audio field. They are also usually have quite good DACs inside, so you do not need a separate DAC anymore. Connect sub and your power amp to bass management device and you are good. Do not forget to do calibration and tuning with room response management software (there are free available, but you will have to buy microphone and preamp for it).
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post #16 of 16 Old 07-05-2011, 11:16 AM - Thread Starter
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AP1, getting rid of my preamp and dac and getting a new digital preamp is all good and well and i know is ideal, but unfortuneatly i don't have the cash to be doing that right now!

Plus, i like the sound coming from the combo i have at the moment, i just want the added dimension of a subwoofer.... for now.... I appreciate the input though, thanks!

I've still not made a final decision, all have pros and cons for my setup when looking further into them...
I think all i can do for the time being is get it home, set it up with various connections and see what works best for the time being until i can figure something more permanent out.

I highly appreciate everyones input and suggestions, so thanks again guys!

I'll let you know how it sounds!
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