OHMS ? AMPS !!? SPEAKERS !!!??

Hi,
I dont really understand the 'Ohm' thing and I think I have just cocked up when buying some stuff that I thought was a bargain but we'll see. I'm pretty new to the home cinema thing, had an out of the box thing before and that was easy, but now I've bought myself a PS3 I thought I'd go the whole hog and get a surround amp. Marantz SR4300 AV Receiver, ebay, £80 thank you very much. Hmmm, speakers, Mission M70 x4 + MiC7 centre, no sub, ebay £51 thank you very very much.
This is my problem, the amp says 6 Ohm speakers, the speakers are 8 Ohms, what happens if I use them for any length of time? I only noticed the 6 ohms thing on the back of the amp when I was about to plug them in. I had already tested the amp with some old Pioneer speakers from my old hifi to see if it worked and they sounded ok to me. Listened to the radio for an hour or two without any explosions.
Can somebody try and explain the 'Ohm thing' to me, I'm not an idiot, I'm pretty good at building PC's but this has me stumped.

Any help will be much appreciated.

 

Hi Wilbow ... welcome to afterdawn! I'm a bit confused ... I just looked at the specs for your AVR in about six different sites and the all say that the receiver is 8 ohms. (What little I read of the reviews seem to indicate a nice piece of equipment). Anyway, double check your manual; I can't help but wonder is it isn't speakers A+B which = 6 ohms.

http://www.hometoys.com/htinews/feb04/articles/polk/impedence.htm

I also got the following information from the "Crutchfield Advisor" which is always a decent and easy to understand source of information:

Anyway, even if your amp is 6 ohm, which I question, you should still be o.k. with the 8 ohm speakers according to the explanation in the article.

 

Thanks for replying,
It says in the manual 'Be sure to use speakers with the specified impedance shown on the rear panel of this unit.'

I have took a photo:-

http://marantz-amp.mypicgallery.com/

Do they have to be the same? I wont be blasting the sound out, I dont want to annoy the neighbours, just watch a film and play games in surround at normal listening levels.

 

Sorry, I didnt notice the should be ok bit at the bottom, I have just played a bit of Resistance Fall of Man and watched a bit of Casino Rayale and they seemed perfect.

Many Thanks again

 

Hi Wilbow! I've read quite a number of articles and forum posts that say that 8ohm speakers with 6ohm amps is fine. I've also seen quite a number of amp and speakers packages (like some Kenwoods) that matched 6 ohm amps with 8 ohm speakers. What I would do though, just to make yourself feel more comfortable about it is to post your question in the following Marantz-Europe site which will answer tech questions about their products:

http://www.marantz.com/new/index.cfm?fuseaction=Company.Contact&cont=eu&bus=hf

 

Thanks very much for your time, it was a big help.

 

Hi again,
just tried watching a dvd with the sound a little louder, nothing harsh, but audiable from the next room say, a 'bassy' part of the film caused the amp to switch off. I am only using crap speaker wire at the moment (stuff from my old out of the box setup, not much better than bell wire) could this cause this to happen, or is it the amp speaker ohm mismatch thing?

Cheers

 

Hi Wilbow! Well, I'm really puzzled; every site I look at (even the UK sites) say your AVR is 8 ohms yet, I saw the pic you posted of the back of your amp. You've got me so curious that I contacted Marantz. Still, I don't think that a 6 ohm amp with 8 ohm speakers is an issue. I'm curious to know what Marantz will have to say and I'll speak to a friend at work tomorrow who is more familiar with the electronics end of home theater.

I do suggest two things: first, go into your amp's speaker set up menu and make sure that the "sub" is turned OFF and make sure that your mains are turned to "LARGE" ... otherwise, it will send the low frequency signals to the sub which isn't there. (Nice speakers by the way, I looked them up).

Also, you want to get rid of the crappy speaker wire ... they could be causing you power problems. You don't have to spend a fortune on "monster" speaker wire but you don't want crap either. Make sure your speakers wire is no thinner than 16 gauge (that could be an American measure though) anyway, you don't want "thin" speaker wire. Also, stick with a trustworth name even if its thicker wire because a lot of the cheapo/bargain brands might seem nice and hefty but 90% of the wire is cheap non conducting metal which makes looks deceiving because it looks hefty but conducts signals no better than the crappy thin stuff. Make sure that both ends of the speaker wire (at the back of the amp as well as the back of the speaker) ...make sure that both ends are cut nice and cleanly with only just enough of the insulation stripped. Make sure there are no stray wires sticking out and that none of the wire goes past the speaker posts touching the amp.

I'll get back to you tomorrow with what I find out...Gerry

I'll also ask a buddy here at AD to join in and give his opinion.

 

I think 6 ohm amp, with 8 ohm speakers, should be ok. If you were trying to push 2 ohm speakers, with a 6 ohm amp, then you could have a problem. Denon told a friend of mine, that 2-3 ohms, one way or the other, wouldn't hurt anything. But 4 ohms or more difference, with lower ohm speakers, should be avoided.

Amp/receiver turning off like that is usually because of a frayed speaker wire, touching something it shouldn't. Double check all the speaker connections, on both ends. One tiny strand of the wire can cause it.

Good luck!

 

Thanks JVC! Everything I've read said the same thing you did ... two or so difference won't make any difference especially when the impedance of the speakers exceeds that of the receiver which is exactly the case here.

@Wilbow .. I'll still ask just for the hell of it but I'm sure JVC and the articles I've read are correct. You've got some very nice equipment; I hope you get it all straightened out so that you can enjoy it without concern. When you can afford it, I would get a sub though.

 

Thanks alot guys for really taking an interest.

I have ordered some (hopefully decent) cable from a reputable Ebay seller, (11,000 + positive feedback) it should be here in a day or two. The amp only switches off if I turn the volume up, it'll work ok at low volume, so I am hoping its the crap cable. I'll keep you informed.
I did the setup thing before I tried the speakers, so it wasnt trying to run a sub. But I was a little unsure whether the speakers I had should be described as large or small? Is it physical size or wattage that counts?
I filled in the 'contact us' form you gave me a link to, I'll let you know what their response is when I get one.

Thanks again guys.

 

If your speakers are set to small, the LFE is sent to a subwoofer. If they're set to large, the LFE will be sent to the speakers. That's basically all that is.............

 

Well guys I'm back again, still having probs. Beginning to think that the amp is faulty now. I got my cable delivered today, it was like rope! lol. I think I could probably do with some slightly thinner stuff, only just managed to get it in the clamps ( no stragglers ). Anyway, it will tolerate slightly higher volume levels ( -23 dB instead of -32 dB ) but cuts out any higher than that.
Oh well you get what you pay for I suppose, I'll just have to look at a budget new amp, all I want is reasonable surround sound for dvd/blue ray and games.

Any suggestions?

Oh yeah, would it matter what model of Sub I went for?

 

@wilbow ... sorry to hear you're still having problems. I do have one other idea though; with the receiver at 6ohms, perhaps its pushing too much bass for the speaker to handle. I would try two things: try cranking the bass way down and see what happens. Also, try going into your speaker set up menu ... turn the sub to "on" (even if you don't have one) and switch the mains (fronts) to small ... that will route the lowest part of the mid range and the bass to the sub ... I know you don't have a sub but try it anyway (it could still turn off as the bass signal has nowhere to go but worth a try but I can do it on my Denon and Marantz and Denon are very much the same technology). The reviews on those speakers are really awesome, by the way.

Your receiver is 80w x 6. A sub at 150-200w should do you fine. You've got all matching speakers which was a smart thing to do; the make of the sub isn't important regarding the "timber" timber of the system so you're o.k. to buy any decent brand.

Perhaps it is the receiver, but I wouldn't give up on it quite yet; its a decent amp. Try what I suggested above and see what happens. If it still goes out, get the sub before you get a new receiver. Perhaps with the sub and the speakers set to small, you just might fix your problem. Out of curiosity, is your receiver still on warranty?

 

Thanks for replying, no warranty, bought from an Ebay seller with only 3 feedbacks, probably getting shut. I'll try what you said, I can use it at fair volumes, I wouldnt really want it much higher, it would just be annoying if it trips because of a loud sound effect on a film.

I have been looking at a couple of others in my price range that are new, what do you think?


http://www.pixmania.co.uk/uk/uk/313215/art/pioneer/a-v-ampli-tuner-5-1-vsx-4.html


Hmmm, having problems pasting the second link in, its a Sony
STR-DG510

Or should I look out for a good second hand one.

Cheers

 

Hi Wilbow! Try the things I suggested and see what happens. I'm really hoping that you're amp is o.k.; I've heard more horror stories in this one thread about ebay. I'll check independent reviews about the two models you listed ... both seem fine but its good to read independent reviews to get the real scoop.

I wouldn't buy a used receiver; a lot of people upgrade but a lot of them get rid of them because of problems. Don't buy a used one unless it has a hell of a good warranty. I'll get back with you tomorrow.

Gerry

 

Wilbow, I took a look at both the specs and reviews of the two receivers you mentioned. They're both good receivers and the audio specs don't have differences worth mentioning. The Sony is a bit more powerful; It is capable of 7.1 but unless you have a truly massive room, I'd use it in 5.1 anyway and 5.1 is what you're speakers are set up for. The one truly notable advantage of the sony is the HDMI features which will come in VERY handy in the future should you ever choose to upgrade your TV or buy a DVD player with hi-def upconversion. If I were buying, I'd go with the sony.

 

Hi Gerry,
I've had the amp in pieces and its grim in there I've added some pics, if you click on the photo on the left it will give you a high res photo.

http://Marantz-amp.MyPicGallery.com

there are 2 capacitors or transistors or whatever they do totally burnt out and the board looks to have been damaged also. Its a miracle it works atall really. The guy said he had no problems atall... yeah, right.

I think I will go with the Sony, the PS3 has a HDMI interface, and I'm pondering buying an LCD TV to go with it at the moment. The only thing is that ordinary tv looks ropey on them and prices are still dropping also.

Whats the chances of fixing the Marantz?

cheerio for now

 

Hi Wilbow! Sorry for the delay. How are you?

I took a look at your photos and while I'm no electrician, even I could see the damage. I'm sorry you got taken on ebay ... there are so many such incidents with ebay right here in this forum. How long ago did you but it? Do you think if you raise hell with ebay itself that they'd give you your money back? When you buy electronics of any kind from ebay, get it from one of their stores that has a warranty.

Whether or not its worth fixing is, I'm afraid, out of my area of expertise. I don't think it would do any harm to get a repair estimate though. Just be careful ... some of those repairmen are con artists too!

You wrote:

.Perhaps that's true of some but I have a 40 inch Sony LCD and the reg picture is fine ... certainly not as good as the HD channels, but the reg pic is fine but you're in the UK so I have no idea what your TV reception is like there.

Let me know how you make out, Wilbow! ... Gerry

 

Hi Gerry,
I contacted the seller but he hasnt replied yet, I wont hold my breath. Have to give him a few days before I complain to Paypal.
Anyway I went to a football match yesterday, the Manchester Derby. Its a big game here, superb atmosphere, but my team lost, so on the way home we stopped off at an electricals Shop and my girlfriend bought a 37" Toshiba LCD to cheer us up! Its excellent, I had the guy in the shop running standard signals and hd signals through the whole lot and I thought this was the best. 37C3030. I am gonna buy the Sony amp that I asked you about, seeing as its HDMI.

Cheerio for now