Dumb Question About Ohms ??????

[scasarano]

OK so the manual for my current receiver (Sony STRDE575) says the speakers should be 8 ohms. My speakers (Yamaha satellites 100 W max) are rated at 6 ohms. Can anyone explain to me the importance of ohms in speaker / receiver setup? Also, I am looking into purchasing the Onkyo 503 (or 502). Will this receiver work better w/ my speakers? Please bear with me as I am pretty new to the science behind setting up a home theater.

 

[wafflebird]

A quick explanation

I was over in the other thread and saw the problem you are having with the surrounds cutting out.

In a nutshell the lower the ohm rating of a speaker the more power must be given to it to produce sound. You will see a lot of posts here discussing "Power hungry" speakers. An 8 ohm speaker will be easier for a receiver to drive than a 4 ohm speaker. The 4 ohm speaker will require more wattage to produce the same volume as the 8 ohm. Now do not make the mistake and thing that low ohm speakers must be bad, as a lot of the really, really great speakers are 4 ohm speakers, thus the need for amplification other than from the receiver, as most standard receivers simply would be working to hard to drive these power hungry speakers.

I am sure that the ohm difference in your speakers and receiver is not the problem, as a lot of people (more than are aware of it) have the same set-up, an 8 ohm receiver driving 6 ohm speakers.

My suggestion is play a movie with a lot of surround effects, at high volume, wait for the cutting out problem to begin, then disconnect each of your surrounds 1 at a time, that way you will be able to determine if it is a problem with the wire/speaker or the receiver. If it still does it with one of them connected, then disconnect that speaker and reconnect the other. If it still does it then it is very possible it is the receiver. If it only does it with one connected and not the other, then you will be able to identify the one with the problem. Check/change the wire to that speaker, then see what happens.
Also do not be afraid to switch the speakers around as well. It is possible, although unlikely there could be a problem inside one of the speakers.

Sometimes it can save you some money by doing a through troubleshooting assessment. If all of this still points to the receiver, well then there you go. But in doing this you may be able to identify a cheaper culprit, and if not..... Well time to go shopping!!!!!!!!!

Let me know if this helps.

 

[voriand]

Simplified: Watts law => Watts = current (amps) * resistance (ohms)

Lower the resistance and the current goes up at a given power. The higher the current, the harder the amp has to work to maintain clean power. This also generates heat. Too much heat, the amp breaks. Too much crappy power and the speakers sound like crap. Too much current and you can actually melt the speakers (done that).

But that is all worse case. 2 ohms is not going to hurt. Just maintain good ventalation of the receiver. If the receiver gets hot, turn down the volume a bit.

Those speakers are not power hungry.

 

[MBauer]

Ohm's Law

Simplified: Watts law => Watts = current (amps) * resistance (ohms)

Lower the resistance and the current goes up at a given power. The higher the current, the harder the amp has to work to maintain clean power. This also generates heat. Too much heat, the amp breaks. Too much crappy power and the speakers sound like crap. Too much current and you can actually melt the speakers (done that).

But that is all worse case. 2 ohms is not going to hurt. Just maintain good ventalation of the receiver. If the receiver gets hot, turn down the volume a bit.

Those speakers are not power hungry.

The difference between 6 or 8 ohms should not matter in most cases. There are always gotchas but given what you are trying to do and your other post regarding speakers cutting out, the fact the Yamahas are rated at 6 ohms will not affect your performance, nor should it be causing your intermittent operation of the surround speakers.

The clicking you hear (since it is only the surrounds) is most likely a relay cutting in and out. It is impossible to tell with a schematic or putting it on a bench. There are lots of possible reasons. You have been given some good advice and tips. Isolation and simplification is the best bet. Using identical material - First no surrounds, only the front pair. Add the center, add a surround, add another surround, etc. You may want to just run the surrounds. Doing a bit of trouble shooting in advance of buying a new receiver may save time and trouble later. There have been a few times in my life I have considered buying new equipment to solve a problem, most times the problem was how I implemented the system, not the hardware, so when I am trouble shooting I always look in the mirror first.

 

[scasarano]

Thanks for all of the advice, guys. I still may get a new receiver simply because the Onkyo I am looking at is only $120 refurbished on ubid:

http://www.ubid.com/actn/opn/getpage.asp?AuctionId=10484253#prod_desc

One thing I noticed with my problem is that when I tap the top of the receiver, I can hear it "clicking", on and off. Not sure if that means anything to you experts. I removed the rear speaker wires to check the connections and they were fine.

 

[scasarano]

So I guess the 85 w/ch on the 602 would suit me a little better then huh?

 

[j_garcia]

It's not so much the wattage as much as it's the receiver's ability to handle a low impedance load, which draws more current from the receiver. Though the 602 has a seemlingly low rating, it's power supply is very decent for the price range and it should not be a problem. I installed a 601 for a customer earlier this year and it had plenty of power.

 

[scasarano]

Cool I just bought the 602 on Ubid. Thanks for all of the advice. I'll be checking in with set-up questions when it gets delivered. I've never used my reciever for switching video inputs and I am thinking about doing it when I set up my new receiver. What are some of the advantages of using your receiver for video switching?

 

[voriand]

Never having to change the video input on the tv ever again.

 

[j_garcia]

And the disadvantage to that is, you have to have it on to watch anything....

 

[scasarano]

Right now my TV is set up w/ Tivo in Video 1 and cable direct from the wall in the TV cable input. I use this to watch one program while Tivo records another. I guess even if I use the receiver for video switching, I'll still have to use the TV remote to switch from video 1 to Cable. Does this make sense? This is the reason I have my TV audio going from the TV to the receiver as opposed to connecting the cable box to the receiver.

 

[CaliHwyPatrol]

I think the 602 is the best receiver for the money from Onkyo. You get decent power, a good amount of inputs, zone 2, component up-convert, and some other goodies for under $500. (yes I know, it retails for 500, but it is almost always on sale at CC for 475 or 450). It has significantly more features than the 503 and it is a lot cheaper than the 702, mainly because of the THX certification of the 702 and 15 more watts/channel. 602 = good buy!

~Chuck

 

[MDS]

The 602 does not convert composite or s-video to component - you have to step up to the 702 for that. The 702 also has pre-outs for each channel whereas the 602 does not. I personally think the 702 is the sweet spot for receivers from Onkyo, although the 602 is not far behind.

I was waiting for the 703 and now I see that it will be available in October. The pattern with Onkyo is that they migrate features from the higher numbered models down to the lower numbered models everytime they release something new. So now the 603 has component upconversion when the 602 did not. They make incremental changes with each new model; eg the 601 had only two component inputs, but the 602 has three.

 

[CaliHwyPatrol]

Oh... poo on me... I thought it did do up convert...

The main reason I sell the 602's at work is because you get a pretty decent receiver for the price. Most of the people I am selling to are not on very big budgets and they can't readily put out the 750 for the 702. I'll probably be getting the 703 when I get my discount on them through Onkyo

Do you know if the 603 will have pre-outs? If it does I might just go with that, but we'll see!

~Chuck

 

[scasarano]

OK so about this upconversion. I would like to input all of my video inputs (including my xbox component video) into the receiver. And then connect my receiver component video out to my TV's component video in. Will this work with the Onkyo 602? I'm not as much concerned with the picture quality diff between SVideo and Component (non HDTV) as I am with the convenience of not having to change the input on my TV. I guess if I can't do it w/ the Component outs on the XBox, I can use the Svid's. Am I starting to sound like I know what I am talking about yet. I've definitely learned a lot from the people on these boards in the past week. I'm planning on drawing a one-line schematic of my set up for you guys to check out. Might as well get it right when I connect the new receiver. Already bought the 602 on ubid for $240.

 

[CaliHwyPatrol]

The thing about not having an up-convert to component is that you have to run a component cable <i>and</i> an s-video cable (if you are using s-video or composite) if you want to use anything but component. The upconvert makes it so you only have to run one set of cables. You can get along without it, but it is handy to have.

~Chuck