4 ohm speakers with 8 ohm receiver - AVS Forum
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post #1 of 24 Old 02-03-2007, 12:45 PM - Thread Starter
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I have a pair of nice KEF speakers that I want to use as the front speakers in a surround sound setup. It turns out they are 4 ohms and the receiver I have is supposed to use 8 or 6 ohm speakers only. There are no adjustments on the receiver, a new Onkyo. Is there an easy way to make this work?
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post #2 of 24 Old 02-03-2007, 01:21 PM
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I may be mistaken but I'm almost certain you can't do anything but replace the speakers or get a different amp (or if you have pre-outs get a amp for just the 2 front speakers).
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post #3 of 24 Old 02-03-2007, 01:41 PM - Thread Starter
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I currently have a Niles product that switches between pairs of speakers and adds impedance to compensate for the resistance going down when you add speakers. If this device can add resistance why should it be so hard to do the same with just one pair?
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post #4 of 24 Old 02-03-2007, 01:57 PM
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Quote:
Originally Posted by Curious Cat View Post

I have a pair of nice KEF speakers that I want to use as the front speakers in a surround sound setup. It turns out they are 4 ohms and the receiver I have is supposed to use 8 or 6 ohm speakers only. There are no adjustments on the receiver, a new Onkyo. Is there an easy way to make this work?

4ohm speakers will make most receiver run hot and shut them down.

You can purchase a inexpensive seperate amp like the

Behringer A500

http://www.behringer.com/A500/

http://www.zzounds.com/item--BEHA500

Or

2200 Mono Block Outlaw

http://www.outlawaudio.com/products/2200.html
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post #5 of 24 Old 02-03-2007, 02:35 PM
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I've been using some 4 ohm speakers on my Onkyo 504. The manual states that using speakers less than 6 ohms for long and loud listening periods may cause the thermal shutdown protection to activate (or words to that effect).

So far I've had no problem with the receiver and I've played it for long and loud listening sessions for both music and movies in my small (2000 cubic feet) HT room. In fact the 504 has amazing sound for the $$ and doesn't suffer from dynamic compression with my setup.

The catch is that I'm using it in a 4.1 configuration and only the two main speakers are 4 ohms. They are also 92 db/w/m efficient and crossed over at 80hz. The 504 does run pretty warm, so I give it plenty of room to circulate air. YMMV.
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post #6 of 24 Old 02-03-2007, 02:40 PM
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Quote:
Originally Posted by steve71 View Post

I've been using some 4 ohm speakers on my Onkyo 504. The manual states that using speakers less than 6 ohms for long and loud listening periods may cause the thermal shutdown protection to activate (or words to that effect).

He had mentioned in another thread that his system was already shutting down while playing at high volumes. Just a fyi.
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post #7 of 24 Old 02-03-2007, 02:53 PM
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Originally Posted by GoodOmens View Post

He had mentioned in another thread that his system was already shutting down while playing at high volumes. Just a fyi.

Well, unfortunately I guess that's that then.... as you said, time for new speakers or a power amp

Perhaps he could try crossing over the speakers a bit higher and/or setting his mains to small if they're not already.
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post #8 of 24 Old 02-03-2007, 02:54 PM - Thread Starter
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Well this sucks! My speakers are about 10 years old but high quality and 4 ohm. Do they still sell 4 ohm speakers for home audio and if so, why?
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post #9 of 24 Old 02-03-2007, 03:08 PM
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Originally Posted by Curious Cat View Post

Well this sucks! My speakers are about 10 years old but high quality and 4 ohm. Do they still sell 4 ohm speakers for home audio and if so, why?

That is a bummer, but you should be able to get a 2 ch power amp for less than $200 that will get the job done (provided that your receiver has pre-outs).

Nothing wrong with 4ohm speakers, they just require more robust amplification.

Sometimes, High-end speakers require high-end electronics.
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post #10 of 24 Old 02-03-2007, 03:09 PM
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Quote:
Originally Posted by Curious Cat View Post

Well this sucks! My speakers are about 10 years old but high quality and 4 ohm. Do they still sell 4 ohm speakers for home audio and if so, why?

If you like your speakers then I would invest in that A500 amp.

And yes they still make 4 ohm speakers. I have a few pairs of Polk LSi9's and they are 4ohm speakers.
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post #11 of 24 Old 02-03-2007, 03:11 PM
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Quote:
Originally Posted by steve71 View Post

Perhaps he could try crossing over the speakers a bit higher and/or setting his mains to small if they're not already.


That actually could help. Its the deep bass that causes the power strain. Takes a lot of juice to move that air
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post #12 of 24 Old 02-03-2007, 03:18 PM
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Quote:
Originally Posted by Curious Cat View Post

Well this sucks! My speakers are about 10 years old but high quality and 4 ohm. Do they still sell 4 ohm speakers for home audio and if so, why?

They do still make 4 ohm speakers; however they are becoming more rare to more "efficient" 8 ohm speakers. Most new amps today can't play them due to constraints of power. It takes a lot of juice to drive 7 channels into 4 ohms. If you look at the 7 channel amps that can your talking a lot of electronics/ heat and lots of expense.

For instance if a receiver puts out 100 watts into 8 ohms and it's connected to a 4 ohm speaker ... it is now putting out 200 watts. Multiply that by 7 and you can see thats a lot of juice!

A example of what I am referening to is the NAD M25. That thing weighs over 110 pounds!
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post #13 of 24 Old 02-03-2007, 03:31 PM - Thread Starter
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Like always all my technical problems can be solved by throwing more money at it. My old receiver handles 4 ohms fine but it has just basic surround sound features, no Dolby anything. I guess I'll put these speakers back with the old receiver that is in another room where it's used just for stereo and get some other speakers to go with my surround setup. Thanks everyone for all the advice and bad news.
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post #14 of 24 Old 02-03-2007, 03:32 PM
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Maybe PartsExpress has something which can add impedance to the line level. I've seen some products there which look like male to male RCA barrels, but they are actually crossovers. Maybe there is something similar which adds electrical impedance.

But I would just get the outboard 2 channel amp.
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post #15 of 24 Old 02-03-2007, 04:53 PM
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Originally Posted by mhsens View Post

Maybe there is something similar which adds electrical impedance.

Doesn't work that way. If you add resistance to the wires they will still draw the same power as before from the amp. Instead of the extra power going to the speaker it will be released by the resistor in the form of heat.
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post #16 of 24 Old 02-03-2007, 05:25 PM
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Quote:
Originally Posted by GoodOmens View Post

For instance if a receiver puts out 100 watts into 8 ohms and it's connected to a 4 ohm speaker ... it is now putting out 200 watts. Multiply that by 7 and you can see thats a lot of juice!

In theory, yes.

In actual practice very few (if any) receivers and only some amps double their power output when the impedance drops in half.

Just because there is a knob doesn't mean you should turn it.
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post #17 of 24 Old 02-03-2007, 05:27 PM
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But I would just get the outboard 2 channel amp.

Assuming the receiver has pre outs....

Just because there is a knob doesn't mean you should turn it.
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post #18 of 24 Old 02-03-2007, 05:59 PM
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Quote:
Originally Posted by Curious Cat View Post

I currently have a Niles product that switches between pairs of speakers and adds impedance to compensate for the resistance going down when you add speakers. If this device can add resistance why should it be so hard to do the same with just one pair?

Agree, I to have speaker switches that change impedence for multiple speakers; would assume they could help.....I assume also the volume would be substancially lower as well..may be a problem for balance with the rest of system.
Foolish solution.....Get two more KEFs and stack them and wire them is series...a little expensive too.
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post #19 of 24 Old 02-04-2007, 06:06 AM
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I agree you should retire your older amp to another room for stereo listening. You will want to upgrade to the new HT sound formats for your theater. We all end up doing this...I'm trying to figure out where I'm going to retire some stuff to even as we speak.
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post #20 of 24 Old 02-04-2007, 06:42 AM
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Quote:
Originally Posted by Curious Cat View Post

Like always all my technical problems can be solved by throwing more money at it. My old receiver handles 4 ohms fine but it has just basic surround sound features, no Dolby anything.)

Hey there,

Why not just send pre-out signal from your new receiver to your old receiver. You will then only be using the amplifier section of the old receiver to power the KEFs. I did that (nice preamp to old receiver) when my amp was in the shop.

Just set the "old" receiver to "stereo" or "bypass" mode. Then, when you calibrate your speakers, you will set the volume knob to some level on the "old" receiver, and you shouldn't need to touch it after that.

You can upgrade to a bigger/better amp later, but this will get you by nicely for now.

This, of course, assumes that your new receiver has pre-outs (probably does) and that you want to keep it -- you mentioned that it was brand new, so perhaps you could return it for something that suits your needs better.

--Otto
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post #21 of 24 Old 02-04-2007, 06:48 AM
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Quote:
Originally Posted by GoodOmens View Post

Doesn't work that way. If you add resistance to the wires they will still draw the same power as before from the amp. Instead of the extra power going to the speaker it will be released by the resistor in the form of heat.

I disagree. If you have a 4 ohm load (the speaker; and yeah, it's not exactly 4 ohms across the frequency spectrum) and if you put another 4 ohms in series with it (some resistor able to handle the appropriate amount of power), you now have an 8 ohm load, and that's what the amplifier will see.

Yes, all the power coming from the amp is converted into sound and/or heat at some point. But the load seen by the amp is still 8 ohms, and the power delivered by the amplifier will be inversely proportional on that load, to the limits of the amplifier.

--Otto
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post #22 of 24 Old 02-04-2007, 08:52 AM
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Quote:
Originally Posted by Curious Cat View Post

I have a pair of nice KEF speakers that I want to use as the front speakers in a surround sound setup. It turns out they are 4 ohms and the receiver I have is supposed to use 8 or 6 ohm speakers only. There are no adjustments on the receiver, a new Onkyo. Is there an easy way to make this work?

The newer European models, like the on I have TX-SR674E, have a setting in the setup menu for 4 Ohm speakers that I use for my Canton Ergo 5.1 set. The North-American models (of 674) seems not to have this option. I bought the SR674E (I live in EU) because it could handle 4 Ohm speakers on all channels.

Note that adding a subwoofer, setting all speakers to "small" and a crossover at 80 Hz will ease the load on the receiver. Now I do not have to turn up the volume dial as much as before, and I have better dynamics.

As noted by others in this thread, the impedance is not constant, but changing with frequency. An example of this is some measurements of my floorstanders Canton Ergo 702 DC : http://www.canton.de/download-test-E...Stereoplay.htm

On audioholics.com there are comments about impendance, as in the review of a receiver:
http://www.audioholics.com/productre...aRX-V659p2.php
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post #23 of 24 Old 02-04-2007, 09:23 AM
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I use my 8 ohm receiver to power 4 ohm loads. It's never overheated, you just got to know what your doing. Power is power, and current is current. V = IR doesn't get any simpler. I = V/R. If your load is half of 8 ohms, you draw twice the current, thus twice the power at any particular Voltage, or Volume.

Since my receiver(Onkyo) goes between 0 - 70 in volume setting, I just make sure when running the 4 ohm load I don't push the volume beyond what the receiver can handle. Since those numbers are in dB, 60 vs 70 setting is 10 times less lound, or most likely 10 times less voltage. To be conservative, when running the 4 ohms load, I just make sure I don't go beyond 40. I'll make the assumption that Onkyo bloats the numbers and this receiver when operating under a 8 ohms load can safely provide current when the volume is set at 50-60. Switching to a 4 ohms load, I want to stay lear of that number so I keep my volume at no more than 40.

Usually when playing movies, I have the volume setting at 40 for the 8 ohms load. When driving the 4 ohms load for listening to music, I usually have it at 37, or 3 dB 1/2 volume down.
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post #24 of 24 Old 02-04-2007, 10:32 AM
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Quote:
Originally Posted by madeupfacts View Post

Since my receiver(Onkyo) goes between 0 - 70 in volume setting, I just make sure when running the 4 ohm load I don't push the volume beyond what the receiver can handle. Since those numbers are in dB, 60 vs 70 setting is 10 times less lound, or most likely 10 times less voltage. To be conservative, when running the 4 ohms load, I just make sure I don't go beyond 40. I'll make the assumption that Onkyo bloats the numbers and this receiver when operating under a 8 ohms load can safely provide current when the volume is set at 50-60. Switching to a 4 ohms load, I want to stay lear of that number so I keep my volume at no more than 40.

Usually when playing movies, I have the volume setting at 40 for the 8 ohms load. When driving the 4 ohms load for listening to music, I usually have it at 37, or 3 dB 1/2 volume down.

Just another data point, but I'm able to run my Onkyo 504 at 60/75 powering two mains at 4 ohms (crossed over at 80hz) + two 8ohm surrounds. Typically 45-50 is about as loud as my ears are comfortable with sitting in the sweet spot. But as I said before my speakers are very efficient and I'm listening in a small room.
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