Subwoofer to a stereo setup help. - AVS Forum
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post #1 of 15 Old 02-04-2012, 02:56 AM - Thread Starter
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Ok so this is my question:

I have a Sherwood setup with the RX-4109 stereo receiver (100w on each channel) and the Alto620's.

..and I'm looking to add a subwoofer to it but, I'm concerned on how to hook it up. If for example, I was to buy this active sub:

Wharfedale Diamond SW150

Since there is no LFE channel or separate channel for a sub on the amp, would connecting it like it shows on the manual (I've attached a snapshot to this post) affect the speakers in any way? Would the amp not put out the full power to the speakers because the sub is draining some of it and make the speakers softer? Would it mess up impedance and either make everything softer or make the amp work too hard?

This is obviously my first time doing this so I wanted to consult with people that know about this.

Thank you in advance for replies.

EDIT: If anyone would also like to recommend or suggest a sub, that would be very much appreciated Preferably sealed box, 10", at least 100-200wRMS, around $500AUD max. It would be for music only. Or would you recommend the Wharfedale?
LL
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post #2 of 15 Old 02-04-2012, 05:55 AM
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- L+R speaker-level outputs on the receiver to L+R speaker-level inputs on the subwoofer.
- L+R speaker-level outputs on the subwoofer to the left and right speakers.
- Adjust the crossover* on the subwoofer.

(*There doesn't appear to be any information on the FR of the Alto 620s - not even on the Sherwood website - but, given that they have a 6" driver, I'd start at ~80-100Hz and go from there.)
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post #3 of 15 Old 02-04-2012, 06:48 AM - Thread Starter
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Quote:
Originally Posted by eljaycanuck View Post

- L+R speaker-level outputs on the receiver to L+R speaker-level inputs on the subwoofer.
- L+R speaker-level outputs on the subwoofer to the left and right speakers.
- Adjust the crossover* on the subwoofer.

(*There doesn't appear to be any information on the FR of the Alto 620s - not even on the Sherwood website - but, given that they have a 6" driver, I'd start at ~80-100Hz and go from there.)

Yep I've got that part, what Im not sure about is will that drain some power away from the speakers? Would they get affected by that sort of connection?

The frequency response is 35-20kHz or so. The only place it says is on the packaging haha. I think 35Hz is probably exaggerating but I do hear some faint low frequencies. They just don't stand out as much as I would like; thats why Im going for a sub.
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post #4 of 15 Old 02-04-2012, 06:59 AM
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Quote:
Originally Posted by Fernand-7 View Post

Yep I've got that part, what Im not sure about is will that drain some power away from the speakers? Would they get affected by that sort of connection?

I didn't mean to state the obvious, but the diagram you posted shows the receiver running one connection to a speaker and one connection to the sub for each channel. This is different from what I wrote. I don't know what would happen with that type of connection you indicated, but with a receiver-to-sub-to-speakers connection, there should be minimal/negligible signal or power loss.

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The frequency response is 35-20kHz or so. The only place it says is on the packaging haha. I think 35Hz is probably exaggerating ...

35Hz is very optimistic.
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post #5 of 15 Old 02-04-2012, 07:13 AM - Thread Starter
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Quote:
Originally Posted by eljaycanuck View Post

I didn't mean to state the obvious, but the diagram you posted shows the receiver running one connection to a speaker and one connection to the sub for each channel. This is different from what I wrote.

Oh yes, I kinda skipped this part
"L+R speaker-level outputs on the subwoofer to the left and right speakers."
Very sorry.

The problem with that is, that sub doesn't have speaker outputs.
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post #6 of 15 Old 02-04-2012, 07:35 AM
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... that sub doesn't have speaker outputs.

Oh. Hmmm. Well, in that case, please disregard my comments.



-- Edit --
I noticed that the manual also suggests the following connection method per channel: Receiver-to-speaker-to-subwoofer. Perhaps that's worth a try...?
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post #7 of 15 Old 02-04-2012, 08:24 PM - Thread Starter
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Quote:
Originally Posted by eljaycanuck View Post

-- Edit --
I noticed that the manual also suggests the following connection method per channel: Receiver-to-speaker-to-subwoofer. Perhaps that's worth a try...?

Yeah I saw that too, but I don't have a sub yet. I was seeing if anyone here could tell me if they knew about power drainage from the speakers before I go out and spend $500.
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post #8 of 15 Old 02-04-2012, 11:51 PM
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All the connection methods presented here represent the same exact parallel connection to the sub and speakers. And they'd all be fine. Of course, the sub doesn't have speaker level outputs so that one's out.

The only difference that might theoretically exist between those methods is that sometimes a sub's speaker level outputs are high-pass filtered, in which case how you connected things would make a difference. But, again, the sub has no speaker level outputs so it's irrelevant, here.

Fernand-7, there is no power drainage from the speakers. The sub has its own amplifier and presents no load or power drain to the receiver, at all, with any of the connection schemes discussed in this thread.

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post #9 of 15 Old 02-05-2012, 12:09 AM
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Quote:
Originally Posted by eljaycanuck View Post

- Adjust the crossover* on the subwoofer.

(*There doesn't appear to be any information on the FR of the Alto 620s - not even on the Sherwood website - but, given that they have a 6" driver, I'd start at ~80-100Hz and go from there.)

Just as an aside and FYI, even when a subwoofer's speaker-level outputs are high-pass filtered, the sub's low-pass filter (it's not really a "crossover") setting does not affect what is sent to the speakers. The high-pass filter, on so equipped subs, is fixed at a particular frequency. Very few, if any, subs feature a true continuously variable "crossover".

So, if the sub's speaker-level outputs are high-passed, it is a fixed high-pass filter value (usually somewhere in the neighborhood of 80-120Hz) with a variable low-pass filter (sometimes incorrectly called its "crossover") setting that you adjust to taste and/or to the high-pass filter frequency that is being applied to the sub's speaker-level outputs. If the speakers roll-off above that fixed high-pass frequency, then you can usually, depending upon how high the sub's variable low-pass filter can be set, adjust the sub's variable low-pass to a higher setting that is more appropriate to the speaker's roll-off.

There ARE many subs whose speaker level outputs are not high passed at all, though, and in this case those speaker-level outputs simply represent pass-through connections that pass a full-range signal on to the connected speakers.

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post #10 of 15 Old 02-05-2012, 12:34 AM
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a quick google search turned up four 'line level to RCA converters' for less than $20. The most expensive of those was only eleven bucks on amazon, plus seven for shipping. If you have Prime it may be less...
seems like it might work, cheaply...
Joe

It's for 'wall hung dude', and no, I don't need any help to 'hook-up'.... sheesh ... dirty minds around these parts....
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post #11 of 15 Old 02-05-2012, 12:54 AM
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Quote:
Originally Posted by wlhungdude View Post

a quick google search turned up four 'line level to RCA converters' for less than $20. The most expensive of those was only eleven bucks on amazon, plus seven for shipping. If you have Prime it may be less...
seems like it might work, cheaply...

Unnecessary and will provide no advantage in this instance. Could even be detrimental. A speaker-level connection will work just fine, here.

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post #12 of 15 Old 02-05-2012, 01:18 AM - Thread Starter
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Quote:
Originally Posted by sivadselim View Post

All the connection methods presented here represent the same exact parallel connection to the sub and speakers.

First off, thank you for clearing everything up but, I have one last question

You mention the parallel connection. Wouldn't that mean, connecting a subwoofer (I'm guessing it also has impedance) in parallel with two 6 ohm speakers, halve the impedance and then make the receiver work with like 3 ohms or so.

This is a wild card I'm playing but I just want to be sure.
Thanks again.
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post #13 of 15 Old 02-05-2012, 01:28 AM
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Originally Posted by Fernand-7 View Post

You mention the parallel connection. Wouldn't that mean, connecting a subwoofer (I'm guessing it also has impedance) in parallel with two 6 ohm speakers, halve the impedance and then make the receiver work with like 3 ohms or so.

No. Because it has its own amplifier, the impedance that the sub presents is so high that it is irrelevant. It, essentially, presents no load. The receiver's amps will still operate at the same impedance were the sub not connected. So, don't sweat it.

BTW,with 6ohm speakers, the sub would have to present an impedance of 6ohms, too, for the parallel impedance to be half the value of the two impedances. Anything else and the calculation becomes more complicated than simply halving the two identical impedances.

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post #14 of 15 Old 02-05-2012, 01:34 AM - Thread Starter
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Originally Posted by sivadselim View Post

No. Because it has its own amplifier, the impedance that the sub presents is so high that it is irrelevant. It, essentially, presents no load. The receiver's amps will still operate at the same impedance were the sub not connected. So, don't sweat it.

BTW,with 6ohm speakers, the sub would have to present an impedance of 6ohms, too, for the parallel impedance to be half the value of the two impedances. Anything else and the calculation becomes more complicated than simply halving the two identical impedances.

Yeah I had no idea about active sub impedance so I was really just guessing. Thank you very much.
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post #15 of 15 Old 02-05-2012, 07:36 AM
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Quote:
Originally Posted by sivadselim View Post

Just as an aside and FYI ...

Thanks for the info. That is very interesting to know.

And I feel kinda foolish for having always assumed that a "crossover" on a subwoofer actually did what its name - in my mind - implied it did.
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