Axiom Home Page Forums General Discussion Home Theater Bi-amping Denon 3805 in 5.1 to L/R(240watts@8ohms)

I was reading a review on the Denon 3805 in regards to purchasing M80 mains with the 4ohm power concerns at higher volumes. What I get out of the 7.1 Denon receiver is that when running on a 5.1 setup, you can
bi-amp the L/R front mains using the rear amps as the low biamp source and the L/R amps for the high biamp source. With the combined 120 watts into 8ohms it will provide 240 watts to each main @ 8ohms.
Is my thinking right here that you would guess to gain around 350 watts into M80's 4ohm speaker? Is that not a bad combination from a single receiver.

Your opinions would be great to hear.

Yes you can do it but take it from one who has done it; the achieved actual output power has been greatly exaggerated. I noticed very little difference when I did it.

Some have reported a night and day difference. It wasn't there for me.

I imagine if you went the whole hog, picked up a good electronic crossover, and fed different signals into the two amps there would be more difference -- not saying that's worth DOING, just agreeing that "simple bi-amping" (both amplifiers get the same signal) probably isn't worth the effort.

No, it'll actually still only provide 120 watts to the speaker (I don't remember the math).

Maybe I read this wrong but, check the following review out;

http://www.audioholics.com/productreviews/avhardware/Denon-AVR3805_review04.php

Correct me if I didn't get the right info from this review, but if you are not using the 2 rear amps to run the rears and instead use them for half of the L/R fronts, at a minimum would you not reduce the heavy load draw on the amps normally regulating the main L/R speakers from the 4ohm, M80's. This in turn would allow you to provide cooler running on the original L/R amps, sharing the load.

Winterpeg,

Interesting question. Off the top of my head, I'd say there wouldn't be significant advantage, because the Denon's power supply still has to come up with the current into the low impedance that it "sees." But I'll ask my colleagues on Monday. And if you really want tons of current, get a big, fat separate stereo power amp for the M80s, or a couple of monoblocs.

I've never recommended bi-amping for typical home installations (there are applications for professional monitoring at extremely high playback levels where it can make a difference) because I've never heard significant audible differences in a normal-sized room (2,500 cu ft) with either bi-amping or bi-wiring.

Regards,

Peg, I believe that the consensus of the previous replies is correct. Although that site is generally a very reliable source of information, that particular point seems questionable at best. The outputs aren't "combined" and 240 watts don't result. Each half of the speaker is driven by a separate 120 watt amp section and can't "borrow" from the other amp in the unlikely situation that more was needed. As Alan points out, there's still just one power supply section in the 3805 to supply all of its amp channels. It would appear that at most there would be a reduction in the total load carried by the output transistors in two amp sections, but this wouldn't create any audible benefit and it would be uncertain if the service life of the sections involved would be significantly lengthened. In my view not worth the bother; in most setups the 3805 should be fine with the M80s as is.

It is looking pretty much like an absolute majority. It was probably an error in understanding. I guess it just looked a little to good to be true.

I'm sure the 3805 will do just fine as well. I have seen plenty of posts that say just that. I guess if it doesn't, then some future savings could be put aside for a couple of Outlaw mono's, which should cure any desire.

It's always good to explore these things, just remain suspicious about "too good to be true". Now if the extra amps in the Denon could be *bridged* to make one big amp that would probably be a different story

In reply to:

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Now if the extra amps in the Denon could be *bridged* to make one big amp that would probably be a different story

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Even if the amps could be bridged you couldn't run a set of M80s with them.When you bridge an amp the amp will see the load as a 2 ohm load not 4.

Hmm. Seemed (don't make me say it ) too good to be true...

Yeah man .You are right if it seems to good to be true.................you know the rest.

I received a reply from the source of my 3805 bi-amping information.

Reply as stated;

That is correct. Of course you are not getting 240WPC or bridging the Denon using this method, you are merely supply the high and low with its own 120WPC. The main advantage is in gaining 3dB more headroom and having two dedicated amplifiers for each speaker...


We used the 240 number as an illustration of having two 120 W amps going to each of the main speakers, not to suggest there were actually 240WPC. Certain people latched on to this and misread the article prompting us to change it (months ago) to read "2 x 120W":

http://www.audioholics.com/productreviews/avhardware/Denon-AVR3805_review04.php

I am sure Alan will confirm this as well on tuesday.

"It sure sounded good though"

Troy

Possible future owner of;
M80ti &/or M60ti
VP150
QS8
EP350 &/or EP500
Amp still to be determined (Denon 3805, Outlaw?/Rotel)

I love that "we use 240 as an illustration" bit. In other words, "We're lying marketing division bastards."

Ken that was right to the point.I do agree with ya though

One of my major pet peeves is misleading (or outright untruthful, as this appeared to be) marketing materials. Can't stand it. They already push us and push us to buy stuff, then they have to lie about it too. Screw that! If it's a good product (as I'm sure the Denons are) they should stand on their own merits.

Amen Brother!!!

I think winterpeg's source of info on the bi-amping came from the Audioholics web site and not from Denon. In fact, I read somewhere that Denon discourages the bi-amp procedure with the 3805.

Troy, that reply you received was in part self-contradictory . Although it acknowledged that 240 watts wouldn't be obtained, it claimed 3dB more "headroom". 3dB more headroom over 120 watts would be 240 watts. The increase in headroom is 0dB.

Exactly... mathematically - 3dB is a doubling of current. Acoustically, 6dB "sounds" twice as loud.

Bren R.

Look a new Bren.

Yeah, yeah... me wearing a ClearCom. Figured I was due for an update.

Bren R.

Bren,

What's a ClearCom? That thing on your head? And don't ask me to update my picture!

Regards,

Yes.... a communications headset.

It's gonna take some time to get used to the new photo. In this one you look almost benign. No more satanic evil look. Could this indicate a kinder, gentler Bren? NAH!

In reply to:

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What's a ClearCom? That thing on your head? And don't ask me to update my picture!

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Brand name for the ubiquitous "broadcast party line communications device"... I believe my right hand is molded exactly to the shape of the RS-501 beltpack:

And I have a permanent dent from wearing their CC-95 single muff headset:

And yes, I do have my own headset for working on road crews. Something pretty unhygienic about wearing a silk sock on your ear for 6 hours at a time. Makes you question who wore it before you.

Bren R.

Not realizing our emails would turn into public domain, I thought I would come in here and offer a response to this inquiry.

First off, we never claimed biamping would yield total output of 240wpc but instead said that the LP and HP portions of each speaker would receive 120wpc each, thus the amp had the potential of delivering a grand total of 240wpc to each main speaker. This is not the same as bridging where you would double the total power to the entire speaker load.

In reality you don’t see a 3dB gain in headroom with biamping like you would with bridging and I apologize if I caused confusion in my quick email reply. However, biamping can improve the sound quality of the system since each amp is delivering bandwidth limited amplification to their respected loads also reducing the potential of back EMF ingress from the other drivers that are now being amplified independently. Of course the true benefits of biamping cannot be realized without replacing the passive crossovers with actives, but that doesn’t mean no benefits exist for passive biamping.

In the case of a receiver amp with finite output impedance, this could be an advantage assuming the power supply is up to task for delivering full power into 4 channels instead of just two. The AVR-3805 is capable in this respect. Don’t forget that the HP portion of the speaker system usually consumes far less power than the LP portion so in a two way system the tweeter will at best consume a few watts since music above 8kHz is harmonic in nature. We have found that passive biamping of tower speakers with receivers does improve system bass control, which is likely to do more with the output impedance of the amps than actually furnishing additional power. We plan on doing more testing in the future to confirm our subjective listening assessments. Stay tuned…

Thanks very much for your clarification.

Just to clarify your statement; "Not realizing our emails would turn into public domain".

Only the "technical information" and "system parameters" were mentioned. This information was brought forward to clarify the earlier information request I sought. I required verification from the very knowledgable folks on this site who up to now have been very helpful. I am not as knowledgable about these things, as many here are.

The end result is to aid myself and others in correctly purchasing HT systems, whether speakers and receiver and/or amplifier and processor equipment to match my/our needs. As I am about to spend a fairly large amount of money on this purchase, I need to know how these particular electronics components will work together.

The technical information and system parameters that I brought back to this site were brought forward to correct the inaccurate information I had posted earlier in regards to the Denon 3805.

With your help and theirs I possibly avoided purchasing equipment that would not have matched my expectations. I would like to thank all those who provided their input in this matter.

Thanks,
Troy "winterpeg"