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March 28, 2008 - 7:19pm
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Ohms...?
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It might. Take a look at the measurements JA does for any full speaker review in Stereophile. You'll see the manufacturer states a nominal impedance which is typically the "average" impedance for the entire frequency response bandwidth of the speaker. Looking at the first graph of the "Measurements" section you'll notice that the speaker does not actually remain at six or eight Ohms over much of its actual frequency response. A "nominal" eight Ohm speaker might dip down to below three Ohms at some point and rise as high as 60 Ohms at another.
The Denon guy was not so much practicing CYA as acknowledging the fact speaker manufacturers do not provide sufficient information about the load their products present to the partnering amplifier. Most but not all AV receivers have some form of current limiting which is meant to protect the amplifier from excessive current draw which occurs when a speaker's impedance drops. In this respect the Denon guy was saying don't be surprised if the amplifier we build cannot drive what the speaker makers build.
Check for reviews with measurements of the speakers you're buying. This can give you an idea of how difficult a load the speakers is. If the review suggests the speaker is a fairly simple load, you should be OK with your receiver at moderate volumes. If the speaker is a difficult load to drive, you can suck it and see whether your receiver can manage what the speakers require. If the amp shuts down repeatedly, you need to reconsider your plans.
I doubt you'll run into problems since you don't push your speakers all
that loud. Try to give your amp plenty of air circulation if you notice it
running hotter to the touch than normal. As JV said, you'll know for sure if
it starts shutting down from its protection circuitry.
Thanks for the quick responses. I appreciate you helping me and I think I understand, that the lower the ohms, the more electrical current "drag" as it were; the more power to drive the speaker at a comparable level. After reading over this I wanted to add that Denon does market this AVR, and lots of others, designed for bi-amping. So if the speakers I were using had a rating of 8 ohms instead of 6, there would be no issue and Denon would stand behind it...does Denon (amp manufacturers in general) provide more extensive and accurate information than speaker manufacturers regarding the load their products will sustain? I will check the site you mentioned, and try to get some more comprehensive info. Thanks.
Most manufacturers will repair a unit once as long as there are no obviuous signs of abuse or just plain stupidity. Rating the amplifier as capable to drive an eight Ohm resistive load in bi-wire connection is not the same as telling you the receiver will work with any reactive speaker load rated as eight Ohm nominal. Virtually all speakers will have a variable load when playing music. Some more than others and some should not even be considered as possibilities with certain amplifiers.
You should research bi-amping and bi-wiring. They are not the same and you cannot bi-amp a stereo pair of speakers with only one stereo amplifier. Unless the Denon has two independent stereo amplifiers in that one chassis, you can bi-wire but not bi-amp. Bi-amping would require the addition of another stereo amplifier.
You are, however, looking at the semantics of audio. How the amplifier is rated has nothing to do with how the amplifier will be used. You can argue with Denon if that's what it comes down to. But normally the manufactuer will make the final dicision based on what they see. If you continually shut the amplifier down due to what they would term misuse - if it continually shuts down, you should be smart enough to stop doing whatever is causing it to shut down - they have the right to not repair the amplifier. The bottom line remains, if the amplifier distorts or shuts down, you are over taxing the amplifier. Stop doing that!
Amplifier manufacturers are not responsible for the designs of speaker manufacturers and do not keep a file of which speakers are acceptable to pair with their product. Call the speaker manufacturer for the necessary information..
I had a quick look at the owner's manual for the AVR-2808CI and see that it has two outputs for Front A and B speakers each rated for 110W/8 Ohms and 140W/6 Ohms. I have no idea how they can spec the acceptable load range differently for an A or B connection differently that an A + B (bi-amp) connection. In a normal bi-amp configuration, there is no electrical connection between the amplifier outputs. There's no way the two amplifiers for each channel know that the speakers they're driving are in the same box. I'd guess that the specs are for each channel individually, not all channels driven (as it should be). I'd go with the recommendations you've received thus far - Try it and if the amp gets excessively hot or shuts down, don't do it again. On the other hand, driving the fronts with only the A outputs is likely to be perfectly acceptable.
Maybe we're not communicating well enough, but is this receiver capable of bi-amping or merely bi-wiring from the A+B hookup? A+B speakers suggests to me you are running both speaker outputs from one amplifier which would not be a bi-amped connection.
The front A speaker outputs have four posts (L and R channels), and the front B speaker outputs are identical. In the amp assign menu, both FrontA and FrontB must be assigned to Bi-Amp for bi-amp operation. The specs lists the capabilities of FrontA and B identically. Sure looks like this receiver is designed to support bi-amping.
Hi-
It's me; I'm back from work. Man, thanks so much for all the input. To answer that last post, 'yes, I think so...' The AVR is a 7.1 system, but is designed for use as a 5.1 with the option of having another pair of speakers (in place of the 'Back Surrounds', like in another 'zone', or for 'bi-amping' the fronts. If it makes it any simpler, (and I don't know for sure what's inside the unit - hamsters, I presume), but if I were to 'bi-amp' I would use two (2) full sets of speaker wires for each speaker from the amp as follows: LEFT FRONT A +; LEFT FRONT A -; RIGHT FRONT A +; RIGHT FRONT A -; and LEFT FRONT B +; LEFT FRONT B -; RIGHT FRONT B +; RIGHT FRONT B -; and then to the corresponding posts on the back of each front speaker; not the 2-into-1 variety for 'bi-wiring'.
Here's a response that I wrote back to someone else....Check this out:
I did want to add that Denon designs this, and many of their AVR's specifically to 'bi-amp' in 5.1 system instead of using all the jacks for a 7.1 system, including back surrounds. So, if the speaker said it was rated for 8 Ohms, instead of 6, the Denon guy would say this was OK I'm guessing, since it suggests that you can bi-amp in the Denon owner's manual? I know you can't answer for the Denon guy, and I'm sure I don't have nearly as much understanding of this as I'd like to think I do. I just find it hard to believe that the amp is rated at 110 watts @ 6 Ohms and designed for bi-amping, the speakers are designed for between 40 and 120 watts, 6 Ohms and designed to be bi-amped, and yet bi-amping these speakers with this amp could be catastrophic. I barely noticed the 'fine print' on the back of the unit next to the outputs. It says: Front A - 6 Ohms / Front B - 6 Ohms / Front A + B - 8 Ohms. Crazy. To do this proper would I need to get a second amp and use this as a pre-amp? Man, I was originally turned onto Monitor Audio Silvers in a 'Hi-Fi" shop by a very knowledgeable fellow who totally knew what AVR I planned to use and was pretty familiar with it. He said that the great benefit of that amp with these speakers was the ability to bi-amp. Of course, I saved a bundle and bought online; not really proud of it, but 600 bucks is 600 bucks (I'm a whore...). Oh well, thanks. I will certainly proceed (if I do proceed) with caution (that'll be a first)....I guess I'll at least proceed with Xanax.
And in a bit of a side matter, I am truly a noob, and wasn't sure quite what to do (I'm kind of a noob at blogs also) so I posted to a couple of other blogs and I just thought I would include the complete list of replies that I received from my original post (same as the first post on here) on another site. Here it is:
<<< No, the "ohm issue" won't matter in your situation. Neither will the biamplification in the first place. >>>
I said, "Thanks; care to elaborate?" but haven't seen any response yet, but I'm guessing there'll be yelling involved...
Just wanted to say that I won't really need to post elsewhere in the future. There seem to be a really dedicated and helpful crew posting here, open to looking for answers and learning as well as teaching. THANKS VERY MUCH ALREADY ! ! I still might blow my new receiver up, but I really appreciate your input, efforts and help...and patience. I think I'll go back to that other site and tell that guy that I tried it and my amp totally caught on fire, just to see what he says...I'll let you know.
Meantime, I'm still open to suggestions, as long as they involve bi-amping my speakers, having them sound great, and never having any more troubles. OK, I guess I'll just have to wait for the most prudent advise you have to offer and act responsibly. Anyway, thanks a bunch already...
This seems to make sense to me, which may not be a good thing. And of course, if my amp/reciever were to shut (oops, almost a serious mispelling) down, I would not try to keep running it in that configuration (at least not more than a couple or three times, probably). As with everything, there's a pretty serious learning curve with this AV thing...
OK, I'm pretty much replying to my own posts now, which instead of a noob, I think, makes me more of a 'goob'. Anyhow, I wanted to add that I found a review of my speakers (the fronts) on/in Stereophile. Following is the title and address; furthermore, the last address is for the specific testing of said equipment (ie: load, and etc.) I got a bad cramp in my lobe (and was drooling) when I started reading too far down, but I think it was mentioning that they do not present too much of a load, with the exception of a little in the mid-bass range. If it matters, I will be using a sub, which I think I can configure to handle the lower range exclusively. Anyway, you guys can probably make a bit more sense of it than me. I promise not to post anymore until I hear back from someone else.
Thanks again, and here is that info:
"Monitor Audio Silver RS6 loudspeaker" - By Robert J. Reina
I seriously doubt you are going to have any issues with the pairing. However,
even a kind amplifier and speaker load can give amps problems if they are
stuffed into a closed cabinet and can't get proper air circulation.
Don't stack anything on top of the amp and don't block the bottom by putting
it on the carpet. Keep at least a couple of inches above it for air circulation
and go for it.
I would mate the stuff up without so much as a second thought.
Yeah, I'm actually looking at some cabinet and component cooling devices, just in case there becomes an issue and to insure good air flow and exhaust. There's some interesting stuff by 'Cool Components' ; even a thermostatically controlled unit. Of course, it's not cheap and I am in the process of emailing to ask about noise from the unit.
I think I feel pretty confident now about this Ohm issue after reading through some of the items on Stereophile, and of course, the fantastic replies that I have recieved from everyone.
Oh, and just as an update ...I checked back on that "other site" and I did get another inspirational reply. I don't have the technical knowledge or expertise to give this guy a proper answering; maybe one of you guys should log on and give it a go...? Just a thought, it may be fun (although a complete waste of time, no doubt). In any case, here's the site and the reply to my question (it's kind of amusing):
Site: Audioholics.com
GoTo: Audioholics Home Theater Forums > Home Theater Hardware Hangout > Amps, Pre-Pros & Receivers > Help with Bi-Amping and Ohms...
Mr Sluggo: First reply to my original question/dilemna....
Mr Sluggo: No, the "ohm issue" won't matter in your situation. Neither will the biamplification in the first place.
Me: Thanks; care to elaborate?
Mr Sluggo: We went through this last week and the week before. There is is no benefit to to wasting an amp powering a tweeter. The result is likely a worse outcome.
Just connect your speakers normally, enjoy them, and forget you ever heard of passive biamping.
Well, he did reply...and of course, signed with one of those lists of all his huge equipment (contrasting with my puny speakers and such); I think I will tell my amp burst into flames. I can't help it. I'm a child...