Help With Ohms?????

Discussion in 'Archived Threads 2001-2004' started by Allen Gentry, Mar 25, 2002.

  1. Allen Gentry

    Allen Gentry Auditioning

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    I read the newbie section. I have a slight grasp on what's being discussed, but don't really understand it in real world meanings.

    I'm currently looking at replacing both my receiver and fronts, center, and subwoofer. The financials prohibit buying all at the same time. The components being replaced were from a Phillips HTIB. Currently, my speakers are rated at 4 ohms. The sub is passive. My room is small, square, with a raised ceiling and hardwood. We sit about 10 feet from the TV and SS.

    Most receivers seem rated at 8 ohms. I know there are receivers that can switch between 4-8 ohms, but within my budget, nothing is available. What happens if a buy an 8 ohm receiver and continue using my 4 ohm speakers?

    Some speakers I'm looking at are 6 ohm. Are those OK to use with an 8 ohm receiver?

    What about my sub? It's passive. Most receivers say they have a "pre-amp" out for the sub. Will mine not work since it relies on my current receiver for power? I'll need a new "powered" subwoofer?

    I wish I could aford some high dollar stuff, but this is all entry level. It's still a step up though. My receiver only decodes Pro logic, and my speakers only handle 40 watts or so.

    Opinions on the Aiwa AV-D58? That's what i'm looking at. Seems fine for my application. I'm also looking at Yamaha's NS-6390 3 way bookshelf speakers with the NS-AC40X center, or possibly going with a satellite/sub set up like Yamaha's NS-P220.

    Thanks for any help.

    Allen
     
  2. SanfordL

    SanfordL Stunt Coordinator

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    Hey Allen, I am currently undergoing the same process as you. I have already ordered my SVS 16-46PCi (hopefully gonna get it by the end of the month) and now am waiting to save up money for speakers. My current set-up is such that I needed the sub first and foremost (I have a JBL "mud-box" that I can't live with any longer.) If I was going to start from the ground up, I would definitely spend most of your money on speakers. I am sure some will disagree, but you will get the best bang for the buck if you spend alot for the speakers. The best signal is still going to sound like crud coming through a poorly made speakers where a fair signal is going to sound magical coming through a great pair of speakers. That's my 2 cents about how to do it.

    Next, how are you driving that sub? You say it is passive, are you running that off of your current receiver ( is that a speaker level output, or does it have a specific sub amp built in)? What I am getting at is, if you are going to keep your sub (and save some money,) you might want to keep the receiver just to drive the sub. If your new receiver has a sub preamp out, just use that as the in for your old receiver, and the signal out send to your sub. You would need to get a Y RCA addaptor to convert the single RCA to a dual, and then use that as an input to your current receiver assuming it has the ability to have RCA ins.

    But, if you get 4ohm speakers with your old receiver that can only drive at 8ohms, they (new 4 ohm speakers) might shorten the life of your current receiver, because (this is from memory, which is bad these days) when you run to 4 ohm's, but are trying to send 8 ohms, you get an increase in distortion. The distortion causes clipping, which eats amps for breakfast, particularly amps that are not very robust. As well, if you run your receiver like this, it is gonna get HOT, so ventilate, ventilate, ventilate.

    What is your budget like? Where are you looking at in the Chicago land area for the equipment? Oh, and also, what do you currently have, because you might find that if you have a few good things, you can build off of them instead of getting a whole new set-up.
     
  3. Allen Gentry

    Allen Gentry Auditioning

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    Sanford,

    Thanks for the response, that really helps confirm what I thought after reading the help section.

    8 ohm speakers on a 4 ohm receiver will make it work twice as hard, and possibly burn up the receiver. Or would that blow the speakers? I suppose the reverse could be true then too. 4 ohm speakers on an 8 ohm receiver wouldn't work the receiver very hard at all, but cause an excess of voltage and you might risk damaging the receiver. Does that sound right?

    My current receiver and speakers are kinda goofey. The fronts, center, and sub are rated at 4 ohms. The surrounds are 8 ohms. It's a Phillips Magnavox MX920P. Not really worth keeping, except for maybe in the basement or garage. I'll probably go with the temporary idea of using it for my sub.

    Well, thanks for that idea regarding the sub. Yes, it's just a passive sub. The amp is in the receiver, and just a speaker wire runs from the receiver to the sub. The sub doesn't turn off or on, and has no power cord. That may get me by for a while.

    My budget is very low. I think I'm gonna pick up the receiver and the Yamaha 3 way bookshelf speakers. Then I'll have an 8 ohm receiver, and 4 speakers at 8 ohms. My center speaker will still be a 4 ohm piece, so I may not use it at all for a while. Then I can get a matching Yamaha center and powered sub. I'll be using some Bose 501x for surround. I already have those, otherwise I might have considered something else.

    Allen
     
  4. Mark R O

    Mark R O Stunt Coordinator

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    Allen,

    The lower the impedence of a speaker, the easier it is for an amplifier to send it power (current). The words used when discussing "ohms" are literal. Impedence and resistance. The higher the speakers ohm load, the more it resists the power coming down the wire. Higher ratings impede the current delivery more than a lower ohm ratings. Amplifier power will generally increase as the ohm value gets smaller. A good analogy is to think of the speaker as spray nozzle on the end of a hose. Say the nozzles "8 ohm" setting is a wide spray. It gets that pattern by blocking the amount of water it lets out of the hose. Say that a "4 ohms" setting is a jet stream, it accomplishes that pattern by letting more water out. 2 ohms would be a blast, but what happens if you have a "0 ohm" setting. There is the rub. "0" means nothing holding the water back, so now instead of being able to squirt over and nail the neighbors' cat and kids, you have zero pressure, not even enough to get the water down the hose...

    In an amplifier, that is a direct short. While most good quality amps have no problem with 4 ohm loads, few do well with 2 ohms, and fewer still will handle 1 ohm. It takes very high quality (more expensive) parts to build an amp that will double or triple it's rated power as ohms decrease, so some manufacturers tell you not to use less than 8 ohms, a load cheaper parts can handle.

    These days most reputable receivers can handle 4 ohm loads with no problems. The ones that can will give you a power rating into 8, 4 and sometimes even two ohms. Denon used to, don't know if they still do. Yamaha and Onkyo did too, so check and see. The king (2 years ago, anyway) was Marantz. Their 120 watt receiver would hump out 400+ watts a channel before finally going nuke! Bottom line, if it's not rated into 4 ohms (regardless of what speakers you own) don't buy it! Last tip, always remember that in hi-fi,

    heavy is good!

    Thanks for lettin' me ramble...

    Good Listening,

    Mark
     
  5. SanfordL

    SanfordL Stunt Coordinator

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    Allen, listen to Mark, he has the technical stuff pretty nailed down, and seems to know a whole lot more about this than I do.
    My main recommendation would be to spend the greatest portion of your money on the speakers. In fact, I'd upgrade one thing at a time, and buy the best you can for each item. And, this definitely makes sense if you don't have money to burn, but want the best your money can get you. Of course, this is assuming you buy into my "get it once and be done with it" ~ for a while a least ~ program. Depending on your budget, you might take a look at Swan Diva's, although I've never heard them, but just read great things about them ( http://www.av123.com ). Also, as the software driving your receivers change, you might spend $700.00 on a receiver, only to find that a year later, your receiver doesn't do everything you need it to. Whereas, if you get good speakers, they will ride along as you upgrade your system. I still have my Boston Accoustics A40's I bought way back in the 80's. I am going to get rid of them in the next 2 years, but I've owned them for nearly a quarter of a century too. Also, remember, most receiver manufacturers are starting to make upgradable (that must be spelled wrong) receivers that you can download new software as it's developed. All hail the upgrage bug.
    Good luck Allen, and post your questions looking for buying recomendations, as if you give folks your budget, most can help you work up to a system you will be proud of.
     

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