Pioneer telling me my B&W speakers (600-series) not compatible with my Elite SC-25 AVR - AVS Forum
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post #1 of 26 Old 11-13-2012, 01:37 PM - Thread Starter
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So I've been running two 685 bookshelf speakers, as well as the HTM62 center channel on my SC-25 for a few years. I noticed a slight distortion on the center channel during loud volumes, and have since attempted to correct this by changing the speaker setting inside the SC-25 menu from "Large" to "Small" - and as far as I can tell, everything has improved.

However, before I did this, I wrote Pioneer asking for technical support, and they needed my speakers impedance and power ratings. When I responded to them with information such as this: "Nominal impedance 8Ω (minimum 3.7Ω)" (685), and "Nominal impedance 8Ω (minimum 4.3Ω)" (HTM62) - they responded back saying that my speakers are "incompatible" with the Pioneer AVR because they fluctuate between 3.7 (in the case of the 685 speakers) and 4.3 (HTM62) to 8ohms.

They are saying when my Pioneer is pushing loud volumes, the speakers are closer to 4ohms than 8, and that by doing so, I may damage the SC-25 receiver, and again, my speakers are "incompatible" with this receiver.

Can anyone else shed some light on this, or reassure me that this is actually OK? I spent A LOT of money on my 3-channel system just for peace of mind if nothing else, and now it turns out I don't even have that! What's the deal??!!!
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post #2 of 26 Old 11-13-2012, 01:41 PM
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I have an SC-25 and been looking at getting new speakers. I was told by my dealer (local hi-fi place, not BB) that it should be just fine pushing a B&W CM9 with a CMC2 center. I have also read multiple SC-25 users driving much more difficult speakers like the PSB Sychrony 1's with an SC-25. I think the main thing is the SC-25 isn't rated to go down to 4ohms, while the newer Elites are (or at least some are) so that's why they tell you that.
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post #3 of 26 Old 11-13-2012, 01:50 PM
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The problem is that Pioneer receiver amplifiers (and many others), are designed with a marginal amount of current available to drive the speakers.

The simple fact is that they really cheap out on the power supply design, and this means that low-impedance speakers are not suitable.

It's sort of like trying to pull a 30-foot travel trailer with a Ford Fiesta; not gonna work out too well. It don't have the power under the hood.

The easy solution is to get rid of the speakers you have and get some speakers that do not go below 6 ohms at any frequency (you need to look at a published curve of the speaker impedance vs frequency).

If you really like the speakers, then you need to get a receiver with low-impedance drive capability, such as the Cambridge Audio 551R or the NAD T-777.

I personally recommend that you get the Cambridge 551R receiver, which will drive almost any speaker and has exceptionally low distortion compared to ANY of the other receivers that I know of.
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post #4 of 26 Old 11-13-2012, 01:55 PM - Thread Starter
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Well, this sucks. So I've been enjoying the system for 2 years now - what are the chances that I will actually harm the AVR if I haven't already? And would it be obvious that I had done harm if and when something occurs?
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post #5 of 26 Old 11-13-2012, 01:58 PM
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Quote:
Originally Posted by sebadooo View Post

They are saying when my Pioneer is pushing loud volumes, the speakers are closer to 4ohms than 8, and that by doing so, I may damage the SC-25 receiver, and again, my speakers are "incompatible" with this receiver.
That's what happens when you talk to customer service reps who aren't engineers. rolleyes.gif
There's no such thing as an 8 ohm speaker. That figure is, as B&W noted, nominally 8 ohms. The actual impedance varies with frequency, and while a minimum of 3.7 is a bit low, it's not a problem for most 8 ohm rated amps, let alone one rated for 6 ohm operation. And while they may dip to 3.7 or 4.3 ohms that only happens at one or two frequencies, and as the HTM 62 and 685 are vented cabs one of those frequencies is the box tuning frequency, which is well below where they operate when the size is set at medium or small.
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They are saying when my Pioneer is pushing loud volumes, the speakers are closer to 4ohms than 8,
At high volumes the voice coils get hot and impedance is increased as a result.
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post #6 of 26 Old 11-13-2012, 02:08 PM
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I have the same AVR as you do. Unfortunately it did not test well in Home Theater Mag with 4 Ohm or less loads. I run 4 Ohm Vienna Acoustics and had a similar problem. The good news is that the SC-25 has a full set of pre-outs and I installed a multi channel power amp to handle the Viennas. The SC-25 is resigned to strictly pre-processor duty and does a great job for me. I can now run my system at any volume I desire with no distortion and the amp, in my case a Parasound 5125, doesn't break a sweat.

So you can certainly look at new 8 Ohm speakers. But if you like the B&W 600 SERIES (and I do - I think the 685 & 683's are very good speakers), you can think about a 3 or 5 channel power amp. This should be cheaper than a 4 Ohm rated AVR like Arcam, Cambridge, NAD, etc. Look at the Emotivas for value. Then the next tier would be Rotel, Parasound New Classic, ETC. All of these have printed specs into 4 Ohms and will get the job done. Hope this helps and good luck.
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post #7 of 26 Old 11-13-2012, 02:22 PM
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It is unlikely that you will damage your receiver; it is just going to distort quite noticeably (as you have observed).

There ARE some speakers that do not go as low in impedance as the ones you have.

Personally, I suggest that you face up to the fact that the Pioneer receiver is a very limited poorly-engineered unit that will not drive 90% of the high-quality speakers on the market without distortion because of its really crappy power supply.

Then buy a good receiver, or get a separate power amplifier to drive the front 2 channels.

The other possibility is to buy something like the Marantz MM7025 power amplifier and use it to drive your front 2 channels. It has a power supply much much larger than your entire receiver...lol.

This will provide all the current you need for the front 2 channels, and the receiver will then have less load on it and will work much better with only the remaining center or and/or rear channels to drive.

Adding an amplifier lets you keep your receiver and speakers and will pretty much eliminate distortion and give you much better sound quality.


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Originally Posted by sebadooo View Post

Well, this sucks. So I've been enjoying the system for 2 years now - what are the chances that I will actually harm the AVR if I haven't already? And would it be obvious that I had done harm if and when something occurs?
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post #8 of 26 Old 11-13-2012, 02:25 PM
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Quote:
Originally Posted by Paraneer View Post

I have the same AVR as you do. Unfortunately it did not test well in Home Theater Mag with 4 Ohm or less loads..
No doubt, being rated for 6 ohms. But there's a big difference between a 4 ohm rated load and a 4 ohm minimum impedance load. The minimum impedance of 4 ohm rated loads averages between 2.5 and 3 ohms. The average minimum impedance of a 6 ohm rated cab runs between 3.5 and 4.5 ohms, so the OP shouldn't be having problems other than possibly pushing the speakers or receiver harder than than they care for. If there was an impedance mis-match it would have shown up in the first two hours, if not two minutes, of operation, not two years.

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post #9 of 26 Old 11-13-2012, 02:29 PM
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THX cert calls for the ability to drive a 3.2-ohm load. A center with limited bandwidth will distort when overdriven by bass frequencies it is not designed to handle, thus switching to "small" cured that problem. Many of us have Pioneers driving 4-ohm speakers without problems. If you like what you hear now, forgot what Pio and this thread said and just enjoy the system.

"After silence, that which best expresses the inexpressible, is music" - Aldous Huxley
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post #10 of 26 Old 11-13-2012, 03:53 PM - Thread Starter
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Thanks everybody! I feel much better now. I'm leaving the center (HTM62) set to it's new setting - 'Small' (down from 'Large') - but am going to keep the main L/R channels (B&W 685s) set to 'Large' because I am under the impression that since I don't have a subwoofer, setting the mains to 'Small' is basically going to remove the bass frequencies I'm used to hearing.

As long as I don't hear any distortion out of the 685s in this setting, I should be "good to go", right?

Also, maybe I should note, I have the front mains in "Bi-Amp" setting (connected both sets of terminals on each speaker to front mains, as well as rear surrounds, and changed the menu setting accordingly). Do I increase my risk of damage in this setting, lower the risk of damaging my equipment, or no change?

Thanks again everybody
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post #11 of 26 Old 11-13-2012, 04:26 PM
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Yes.

No change.
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post #12 of 26 Old 11-13-2012, 07:22 PM
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Quote:
Originally Posted by sebadooo View Post

since I don't have a subwoofer, setting the mains to 'Small' is basically going to remove the bass frequencies I'm used to hearing.
It will. Get a sub. Trying to get decent lows from those speakers is a bad idea; the distortion you were hearing was a warning sign.

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post #13 of 26 Old 11-13-2012, 11:52 PM
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There isn't really any such thing as an "incompatible reciever" it just isn't optimal.

Just set the speaker size to small and crossover to 80hz and NEVER crank ANY reciever. Even if it is capable of providing 10x as much power as the speakers require, the amp is not designed to be pushing its full capable current at all times and will clip if attempted. Rule of thumb for me is if you need to turn the reciever up past about 2/3rd on the volume dial to get your desired output, then you need either a more powerful reciever or a standalone amp.
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post #14 of 26 Old 11-14-2012, 04:30 AM
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^^^

that is simply not true...

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post #15 of 26 Old 11-14-2012, 10:45 AM
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The ironic part is their "Speaker Genius" speakers are 6 ohmers. Their speakers may be a tougher load than the B&Ws!
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post #16 of 26 Old 11-19-2012, 07:24 AM
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when I heard some b&w speakers at a best buy magnolia store in New York City they were using a pioneer elite receiver. The guy tried to say that it was the best receiver that they had for pushing those speakers. He thought that it was better bthen the marantz that he had. sorry that your speakers are clipping with the receiver. I guess keep it at low volumes since it isn't handling the speakers well. sometimes I think that music sounds better at lower volums anyway. When Circuit city was around a worker said that he agrees with me. We both agreed that with louder volume sometimes you get to much distortion.
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post #17 of 26 Old 11-19-2012, 08:23 AM
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^^^

the issue isn't the amplification section "handling the speakers well"... it's that the speakers were being overdriven.... the speakers were going into power compression... try to follow along, please...

as far as the last part... glad you and the circuit city guy agree... it flies completely in the face of proven science, but whatever floats your boat...

no kidding distortion doesn't sound good (with the exception of the vaunted euphonic clipping of tube amps)... rolleyes.gif

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post #18 of 26 Old 11-19-2012, 03:05 PM
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At the end of the day, you're dealing with speakers that are probably pushing your amp too hard. You've heard evidence of it, and as others mentioned, you probably need a subwoofer. I used to run mids in my car for many years without a sub, and cross over at 63hz, and found that most of the time the mids (they were 6.5" Boston Acoustics Pro drivers) would be destroyed after a moderate period of time, even with very high quality drivers. After I got a sub and crossed over at 80hz, the same drivers lasted for many years and didn't deteriorate in the same way.

You really should be running those B&W's at "small" setting, but that's just my opinion. No engineering here, just some street-tested advice.

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post #19 of 26 Old 11-19-2012, 06:17 PM
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good points thirdeye.
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post #20 of 26 Old 11-19-2012, 07:33 PM
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^^^^^^^
Not really

Regards,
Charlie

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post #21 of 26 Old 11-19-2012, 09:34 PM
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So far, point 1-set center speaker to small, point 2 let a sub handle the bass in the system. Many Impedace dips occurs in the 150-300 Hz range and it was pointed out the one critical frequency in at the box tunning. The heavy bass is where the amps power output is put to the test. If you have been running your setup for 2 years, I don't think you will damage it.

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post #22 of 26 Old 11-20-2012, 10:43 AM
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Quote:
Originally Posted by chashint View Post

^^^^^^^
Not really

Feel free to add to the discussion, as opposed to the opposite.
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post #23 of 26 Old 12-09-2012, 02:26 PM
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I would ask to speak with an engineer, it sounds like the people speaking to you are way over their heads.

http://www.churchsoundcheck.com/imp1.html

This is a typical impedance graph of a speaker and EVERY speaker will follow this graph in some way. The spike you see that is over a narrow band, is where the speaker performs most efficiently and acts more like a rigid piston. Every other frequency is outside of the mechanical "ideal" and so has a lower resistance. This is over simplified but it is to point out that every speaker is never really 8-ohms or 4-ohms. Nominal impedance is a joke and their customer support response is a joke as well. The distortion is a result of Pioneer design...either there is a Power Supply deficiency or an amplifier output impedance deficiency. You should look at Bi-Amp'ing if possible or getting an external amplifier for your front speakers to take off some of the load on the SC-25.

ERTW
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post #24 of 26 Old 12-09-2012, 06:06 PM
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^^^

at least one of the posters in this thread is a rather well respected speaker designer... and at least a few of us are far from "in over our heads"...

the fact that you threw "bi-amp" in there tells us you don't know as much as you think you do...

the speaker is going into power compression... the sc-25 will have no issues with those speakers... i am VERY familiar with the sc-xx models, and the problem doesn't lie with the avr...

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post #25 of 26 Old 12-09-2012, 07:25 PM
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Quote:
Originally Posted by ccotenj View Post

^^^
at least one of the posters in this thread is a rather well respected speaker designer... and at least a few of us are far from "in over our heads"...
the fact that you threw "bi-amp" in there tells us you don't know as much as you think you do...
the speaker is going into power compression... the sc-25 will have no issues with those speakers... i am VERY familiar with the sc-xx models, and the problem doesn't lie with the avr...

You might be correct in your guess or were you at his house with the OP???

ERTW
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post #26 of 26 Old 12-10-2012, 06:49 AM
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The OP got his answer back in Post #12, and hasn't made a reply since Post #10. This horse has been dead for a month now, why is it still being beaten? confused.gif

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