What's wrong

[liberalz]

Here is my system & how it is been hooked up.

AVR: Yamaha RXV 740
DVD Player: Yamaha 550
Mains: Mordaunt-Short 908 (Floor stand, 3 way) - bi-wired using A/B
Centre: Mordaunt-Short 905 - bi-wired
Rear: Boston Accoustic - diffuse
Sub: Boston Accoustic - 12", down firing
All speakers are set to small

My problem right now is, there is a buzzing noise comming from all speakers even when no feed from the source is presented. Now the noise is not intrusive but when I switch of the reciever i can feel that it is switched off, something like a florecent lights. (i'm not sure whether i explained my self well). and for me to localize the noise i need to press my ear against the driver to picked it up (am i being fussy here).

So yesterday i tried to pin point the problem by examining the connection, the only pontential problem i could think of is since I did not have a "proper" subwoofer connection cord, i used a normall RCA cord (black & red) and used the red connection only, and the black end was just hanging.

So I replaced the RCA with a coxial cord, not much difference in the buzzing noise.

But what i found was the base got really tight, and i couldn't localize the base from the sweet spot. I had to run to the subwoofer & touch the driver to make sure that it is working. I need more listning before I could say the base is good. In my first immpression i did not feel i lost any base.

I also wouldn't mind some general thoughts on my system, the weakest link etc.

By the way thanks Clint DeBoer for setting me up in the forum.

 

[majorloser]

The Dreaded Ground Loop Hum

Sounds like you've got a ground loop problem.
Usually comes from satelite or cable receivers (damn cable guy).

Read this: http://www.audioholics.com/techtips/setup/avhardware/groundloopcableTV.php

 

[liberalz]

Is there a way to eliminate it . What about coxial cord being used as sub connection?

 

[jcPanny]

Sub connection

All subs cables are coaxial so that cable should be fine. A coax composite video cable will work just as well as a "sub" cable.

Check out the Ground loop FAQ. Having the sub or other devices on a different circuit and the cable box are common sources of the ground buzz.

 

[mtrycrafts]

Mains: Mordaunt-Short 908 (Floor stand, 3 way) - bi-wired using A/B
.

I don't think you want to bi-wire this way, if you are using the receiver's A and B terminals.

 

[liberalz]

I don't think you want to bi-wire this way, if you are using the receiver's A and B terminals.

what would be your suggestion. I read in What HiFi site that A/B connection is fine. I don't mind another point of view.

Cheers.

 

[mtrycrafts]

what would be your suggestion. I read in What HiFi site that A/B connection is fine. I don't mind another point of view.

Cheers.

If you insist on bi-wiring, use the same post A. But, there is no real benefit to bi-wiring to begin with.

 

[liberalz]

If you insist on bi-wiring, use the same post A. But, there is no real benefit to bi-wiring to begin with.

Is this b'cause of impedance.

Well my listening area (room) is not that large, and in fact i did notice some improvement in the mid range (a good punch ), and some clarity in the high range. Especially these improvements were noticebale when listening to some rock music.

i understand the controversy surronding bi-wire, i did not spend a penny to buy additional wire

Maybe the difference I saw could be due to me using post A & B and the impedance is cut to half due to parrallel connection of these posts in Yamaha.

 

[mtrycrafts]

Is this b'cause of impedance.
Well my listening area (room) is not that large, and in fact i did notice some improvement in the mid range (a good punch ), and some clarity in the high range. Especially these improvements were noticebale when listening to some rock music.
i understand the controversy surronding bi-wire, i did not spend a penny to buy additional wire
Maybe the difference I saw could be due to me using post A & B and the impedance is cut to half due to parrallel connection of these posts in Yamaha.

Yes, impedance is one of the issues, main issue.
Spending extra for the wire is not the concern. Knowing the truths is.

Without doing a careful comparison, controlled, level matched, we won't know why your perception is what it is.

 

[Seth=L]

when you have your surround sound going is both A and B on? I would certainly think that it either wouldn't allow it, or would force the B to shut off, and depending on how they are bi-wired it would shut off either your tweeter and midrange or the woofer (woofers).

The thing with receivers is when you bi-amp on most receivers, it won't make any difference. The output stage, transistors, are designed to handle sizable loads, and the power would be limited most by the Power supply or the capacitors, and not the transistors. So Bi-amping on most receivers won't make any difference.

When you look at a receiver's power ratings it is usually only rated for just one channel.

 

[MDS]

Bi-wiring is absolutely pointless.

Think about what bi-wiring is doing:
You are feeding the exact same full range signal over two different wires. The xover in the tweeters will reject the midrange and bass it cannot handle and the xover in the woofer will reject the higher frequencies it cannot handle - exactly the same thing as if you only used one wire.

On a receiver, the A and B terminals are wired in parallel. So not only do you get no benefit whatsoever from bi-wiring but you get the additional disbenefit of presenting the receiver with a lower impedance load than it can handle reliably.

I'm suprised mtrycrafts didn't call it 'buy-wire' because that is exactly what it requires - buying more wire for no purpose at all.

 

[mtrycrafts]

I'm suprised mtrycrafts didn't call it 'buy-wire' because that is exactly what it requires - buying more wire for no purpose at all.

That is step two
Don't want that as step one, for this post. Maybe next poster

 

[sivadselim]

All arguments regarding the benefits of bi-wiring aside, it's perfectly fine to bi-wire using the A and B terminals. It just makes it easier to wire.

"B" just represents extra binding posts on the same amp channels; they're not completely separate amp channels. In doing what he's doing he is simply bi-wiring, not bi-amping. He's still using 2 amps (R & L), not 4.

And there is no difference in impedance (or anything else) from simply bi-wiring off a single set of posts versus using both; it's identical. It's just convenient to do it this way if you have the extra set of binding posts.

 

[Seth=L]

All arguments regarding the benefits of bi-wiring aside, it's perfectly fine to bi-wire using the A and B terminals. It just makes it easier to wire.

"B" just represents extra binding posts on the same amp channels; they're not completely separate amp channels. In doing what he's doing he is simply bi-wiring, not bi-amping. He's still using 2 amps (R & L), not 4.

And there is no difference in impedance (or anything else) from simply bi-wiring off a single set of posts versus using both; it's identical. It's just convenient to do it this way if you have the extra set of binding posts.

How is it easier that way. In theory it should take about half the time and frustration to connect only 2 sets of cables vs. 4. Binding posts on receivers can be a real pain in the @ss, so I want to spend the least amount of time jacking with the binding posts on a receiver. Speakers are easy, because the terminals are easy to get to, and if it doesn't come with bridge straps you can just make you own from wire. And lastly, it is a waste of wire.

 

[sivadselim]

Bi-wiring is absolutely pointless.

Think about what bi-wiring is doing:
You are feeding the exact same full range signal over two different wires. The xover in the tweeters will reject the midrange and bass it cannot handle and the xover in the woofer will reject the higher frequencies it cannot handle - exactly the same thing as if you only used one wire.

On a receiver, the A and B terminals are wired in parallel. So not only do you get no benefit whatsoever from bi-wiring but you get the additional disbenefit of presenting the receiver with a lower impedance load than it can handle reliably.

I'm suprised mtrycrafts didn't call it 'buy-wire' because that is exactly what it requires - buying more wire for no purpose at all.

I don't really want to get into whether or not bi-wiring is beneficial.

But if you're going to argue against something, you should at least understand the other side's argument.

You're post doesn't really address the the purported reason for bi-wiring at all. Of course the same full-range signal is fed down both sets of wire.

And as far as the impedance is concerned, bi-wiring does not "present the receiver with a lower impedance load than it can handle reliably".

And no, I am not currently bi-wiring.

 

[sivadselim]

How is it easier that way. In theory it should take about half the time and frustration to connect only 2 sets of cables vs. 4. Binding posts on receivers can be a real pain in the @ss, so I want to spend the least amount of time jacking with the binding posts on a receiver. Speakers are easy, because the terminals are easy to get to, and if it doesn't come with bridge straps you can just make you own from wire. And lastly, it is a waste of wire.

Because you just connnect 4 sets of wires and your done. No twisting the ends together and trying to shove that fat wad into a binding post or a banana plug.

But, mainly, it makes it really easy to add the second wire set if you were already previously single-wiring.

I guess if you were setting up a bi-wire run, fresh out of the gate, it might not be necessarily simpler. So I see your point.

 

[Seth=L]

I don't really want to get into whether or not bi-wiring is beneficial.

But if you're going to argue against something, you should at least understand the other side's argument.

You're post doesn't really address the the purported reason for bi-wiring at all.

And as far as the impedance is concerned, bi-wiring does not "present the receiver with a lower impedance load than it can handle reliably".

I said nothing about impedance.

The issue was the humming noise, which I am aware no one has really addressed that issue full swing yet, then again what you posted also does not address the problem.

What made no sense about the post was you said it was easier to bi-wire, and it isn't easier. As far as offering advantages the only effective bi-anything is Bi-amplification. Since you can't bi-amp with a receiver such as his, then there is no reason to do that.

The biggest problem with bi-wiring using the A and B terminals is this. When you attempt to activate the surround sound on the OP's receiver it will do one of two things, it will not allow him to use surround sound or it will shut the B speakers off, meaning that one of the terminal on the speakers will be getting no juice. So that means either the tweeters or the woofers will not even be on when he is using surround sound.

Do you see the delima?

 

[Seth=L]

Because you just connnect 4 sets of wires and your done. No twisting the ends together and trying to shove that fat wad into a binding post or a banana plug.

But, mainly, it makes it really easy to add the second wire set if you were already previously single-wiring.

I guess if you were setting up a bi-wire run, fresh out of the gate, it might not be necessarily simpler. So I see your point.

OK, say that in theory that bi-wiring actually offers advantages, that still doesn't account for using the A and B terminals causing problems when using surround sound.

 

[sivadselim]

I said nothing about impedance.

I was speaking to those that did. Not you.

What made no sense about the post was you said it was easier to bi-wire, and it isn't easier.

No, I said that the extra set of posts makes it easier to biwire, especially if you are already single-wiring to begin with.

The biggest problem with bi-wiring using the A and B terminals is this. When you attempt to activate the surround sound on the OP's receiver it will do one of two things, it will not allow him to use surround sound or it will shut the B speakers off, meaning that one of the terminal on the speakers will be getting no juice. So that means either the tweeters or the woofers will not even be on when he is using surround sound.

No, that's not how his (or most) A/B connections work. As I, and others in the thread, said "B" is just an extra set of parallel binding posts on the same 2 (L&R) amps. "B" is not a separate set of amps from the "A" amps.

The OP's hum has nothing to do with his bi-wire set up and would be there even if he single-wired.

BTW, if he connected 2 pairs (4 total) of identical speakers to A and B, then he WOULD be presenting twice the impedance to the reciever. But bi-wiring that way with a single pair will not present any different impedance than if he bi-wired off the "A" posts only. It's the same thing.

 

[sivadselim]

OK, say that in theory that bi-wiring actually offers advantages, that still doesn't account for using the A and B terminals causing problems when using surround sound.

No it doesn't, as I explained in my previous post. Slow down.

He's not talking about "Surround B" amps.

He simply has the ability to connect 2 pairs of speakers to the front channel amps. The "B" connections are just parallel connections off the same 2 front channel amps.

If they were separate amps he'd be bi-amping and he's not. He's simply taking advantage of the extra set of binding posts to not have to twist his wires together. That's all.

And, no, it's not causing his hum.