Adding extra rear speakers

[George Bellefontaine]

I have a Yamaha A3090 integrated amp and presently have two rear speakers on the side walls.They are connected to a subwoofer which is connected to the amp's rear speaker terminals. Question is, if I want to add two more rear speakers to the back walls, do I have to add another power amp to drive all 4 rears speakers, or is there another way of wiring in two more speakers in the present setup.Any help would be appreciated.




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[Lexman]

George, several things enter into this equation. First, let me welcome you to htguide!

1. What is the "ohm" rating of your amplifier?
2. What are the ohm ratings for each pair of speakers involved?

For example. Some amplifiers are only rated to 4-6 ohms. say your amp is rated to 4 ohms. But your speakers are 6 ohms. The net effective load if you wired your speakers both off the amp terminals will be 3 ohms. (adding another set of like ohm rated speakers, effectively halves the load. Or is it doubles the load? I forget the correct terminology here, but I know what I am saying is correct.

What matters here is the amp. Once you get below the rated ohm load of the amp manufacturer, your into an area of great concern. You could certainly burn up a stressed out power supply to say the least, resisters, transformers.

Now some very good amplifiers are actually rated to 2 ohms. The best? even 1 is possible. But these amps have some REAL serious guts. Commercial receiver grade amplifiers are not up to this challenge and are at best usually 4 ohm rated.

Surround speakers of the dipolar or bipolar nature are frequently 6 ohms. This is a problem for the 4 ohm rated amp. (some receivers only really rated to 6!)

Additionally, remember that strong passages will even dip below this level. So, if you really pushed your volume, during demanding passages, your true 4 ohm rating could become 2. DANGER DANGER Will Robinson!

On the bright side, a fairly low power 2 channel amp or two small monoblocks shouldn't cost ya to much to do what you want to do the right way. Then just use an RCA splitter, split your rear signal going off the Yamaha. Send half to the "sub/2 speaker" group, and half to the new amp/speaker group. Of course, if the speakers are less than full range, you might need to eq the low end out. Alternative is if your sub allows both RCA output, and line level speaker connectivity.

Give us more info, and lets go from there.



Lex





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[George Bellefontaine]

Lex,
Thanks for the welcome. I got onto this site through Home Theater Talk. I like your site and expect to visit often. Also, thanks for the reply to my post.Now, I'll answer your questions as best I can. I have always been more savvy on the video end of things than audio, but here goes.
The only info I can find on the Yamaha specs is the following, in reference to the MAIN L/R:
8ohms 6 ohms 4 ohms.........100w/120w/160w
Also, I should point out that the rated output power per channel for the main,center and rears is 8 watts RMS.
All speakers in my setup are Boston Acoustics with 8 ohm ratings.
The sub I am using is wired paralled but it can also be connected line level. The Yamaha has split out sub jacks that sned left info to one sub and right ino to other sub. I wired sub parallel so I could add bass to the rear surround channels.
From what you are telling me, it sounds as though I should go with a small 2 channel power amp.The Yamaha has line level outputs for the rear channels so I expect I would connect the power amp inputs to these.
George




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[George Bellefontaine]

oops, that should have read 80 watts per channel.




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[ThomasW]

George

There isn't enough info to correctally answer your question.

Does the Yamaha amp have outputs for multiple rear configurations, or are you limited to 5.1 channels?

Regarding the sub, I assume that if it's wired in parallel to the rears it's passively powered? If so then It's important to know the load it places on the amp when in the same circuit as the existing rears. Meaning if the sub is 8 ohms/channel and each rear is 8 ohms then you have a 4 ohm load on each channel.




theAudioWorx
Klone-Audio

[George Bellefontaine]

Hi, Thomas,
The Yamaha is limited to 5.1. There is only one set of binding posts for the rear surrounds. The sub is a powered sub so there is no drain on the main amp.It's wired paralell in order to provide bass to the rears with the rears set at large in the amp.




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[ThomasW]

George

Well I'm even more confused now :?

If there is only one set of rear channel binding posts then the amp must be Dolby Pro Logic, as opposed to DD.

As far as I know it's not possible to run a powered sub from the rear channel outputs of an amp. Powered subs are run from line level outs. These are usually RCA plugs not binding posts. So either the sub amp is being bypassed, or the Yamaha amp signal output is being dropped to line level at the sub.




theAudioWorx
Klone-Audio

[Markj]

I know that M&K subs maybe connected via the binding post. This will allow the sub to do the crossover. This helps configuring your speakers because a lot of receivers don’t have good base management.

Why would having one set of binding posts equate to prologic only receiver?

I would not recommend wiring two sets of speakers to a receiver. This could cause the receiver to get too hot.

[ThomasW]

Mark

Dolby Digital and DTS have discrete L&R rear signals, so two sets of binding posts are necessary. Dolby Surround and Pro-logic I have "mono" rear channels.




theAudioWorx
Klone-Audio

[George Bellefontaine]

Sorry, Thomas. When I said set, I meant for left and right. I think Lex pretty much laid it out for me.Doesn't seem like a good idea to add another pair of rear speakers. I'll probably have to go with a small power amp.




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[Markj]

George, sounds like you got your answer.

Thomas: When I had an Onkyo prologic receiver it had binding posts for both of the rear speakers. I understand that Prologic is mono for the rear sound but the wiring is the same, left rear and right rear. Or maybe I am working to hard and my brain is fried.

[ThomasW]

George

Depending on how you wire the speakers, (probably need a series/parallel config), there may not be a problem. But you do need to know the impedance of each speaker, including the sub in order to calculate the load.

Mark

For convience some mfgrs put 2 sets of outputs on Prologic devices.




theAudioWorx
Klone-Audio

[Lexman]

George, glad you found us. Let me add, that I think it would be safe. Your Yamy would run hotter. Probably not great on the life of the integrated amplifier.

The extra amp will give you a lot more headroom on the rears. Of coruse, the rears aren't generally so active that this is a consideration all the time. But occasionally, I guess it could be.

I like the seperate amp approach myself.

Actually, I am not sure that many M & K have high level (speaker) inputs. Klipsch does, my KSW-200 certainly does. But this really isn't the preferred way of transmitting your signal. I would whole lot rather see RCAs used for the sub. Of course, in order to do that and transmit the signal to the side speakers from the rear outputs, you would need an EQ capable of splitting one RCA signal, into two, by adjusting the lower hertz to go to one channel, and all higher output to another. The seperate amp would work out great for this approach, as from that point, you simply take that RCA output straight to the new amps, and your good to go.

Lex

[George Bellefontaine]

Thanks,Lex, sounds like good advice.
George




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