Yamaha RX-V2400 vs. Denon AVR 3805 (1 Viewer)

[Brent_j]

Oh thats good to know Shiu, I just did not want to end up shooting myself in the foot. Thanks!

Another question to whomever...

I should have asked this a few days ago, but I was flipping through my Yamaha manual and the 2400 can drop my speaker impedance to 6 ohm instead of the usual 8, According to the manual if I do this I could get around 150 to 160w per channel, Should I consider this option?? and does anybody know if my Polks could even do this?? my speaker manuals and information I have been able to gather from the Polk web site mention nothing about dropping the impedance, they just have "recommended 8 ohms"


Thanks!
Brent.

 

[MuneebM]

Brent, all I can say is don't run the AVR at 6 ohms if your speakers don't support it. Be sure your speakers are able to go down to 6 or 4 ohms before you try it or it could have very adverse effects. I don't know about your Polks but my JBL Studios are strictly 8 ohms.

 

[Brent_j]

yea, thanks for the heads up Muneeb, I was not going to do anything like that without some information first. I just sent off an e-mail to Polk about this. But I am sure I wont hear back for a few days..:frowning:

 

[Shiu]

Brent, I think what Yamaha may be saying is that the 2400 is rated for 150W if the "nominal" impedance of your speaker is 6 ohms. The impedance of most speakers vary quite a bit over the frequency spectrum. The RTi series are rated 8 ohms nominal but at certain frequencies it could drop even below 6 ohms. There is really nothing you can do to drop its impedance, it simply varies somewhat as the signal frequency varies.

I bet you Polk will response to your email within 48 hours.

 

[Bob*S]

Brent-

You should run your receiver at 8 ohms to match your speakers which also have a nominal impedance of 8 ohms.

You don't run speakers to match an amp's impedance, rather you find an amp that can handle the speaker's lower nominal impedance. Or conversely, you find speakers that will not overtax the amp which usually will result in the the protection circuit kicking in. The impedance switch on receivers allows a amp to more easily drive 6 ohm speakers (which frequently will hit 3 ohms somewhere within their frequency range) at the cost of some dynamics and, perhaps, distortion (no free rides here).

Many people cringe when they see these switches on amps/receivers since a well-designed output stage will drive the lower-impedance speaker through its better high-current design without the need for such a switch.

Bob

 

[Brent_j]

I just got this response from Polk regarding the speaker impedance.

Bob, the Yamaha does not have a switch on the receiver, its all done through the on-screen display, I dont know if that still makes you cringe or not.

"Brent,
This 6 Ohm setting will work just fine with your speakers.
This will not cause any damage to your speakers. The only
way to damage the speakers is to over drive the amplifier
into clipping and distortion. It is the clipping and distortion
that causes speakers to fail."

 

[Bob*S]

Brent-

Glad you got an answer from Polk.

A switch, be it electronic or physical, is still a switch in my book but I don't cringe at them at all. You might want to search the forums though and see if you can find more information on the trade-offs. The extra power comes at the expense of something (I believe it's mostly dynamic range). I'll search for some more info for you, as well, when I get finished up with some work here.

Sounds like you're going to REALLY appreciate those Polks soon.

Bob

 

[Shane Martin]

From what I'm able to find, the Yamaha RXV2400 doesn't have 3 component ins like the Denon. That can be a deal breaker for some.

 

[Brent_j]

Thanks Bob, I will check out the other forums as well to see what I can find. Thanks!!

Shane, Yes, the Yamaha only has 2 Comp. inputs. Not a big deal for me at the present as I only connect my DVD player and cable receiver in to the Yamaha. That might change but not for a long time.

Thanks!
Brent.

 

[Ben Stern]

Not very likely he'd miss the YPAO since the 3805 has a similar feature

I was at my dealer yesterday getting stands for my new Studio 20's v3. We started talking about the Yamaha 2400 and the Denon 3805. While he has them on order, he hasn't actually heard the 3805 yet. He did mention, however, that the microphone that is needed to do the automatic speaker calibration, will have to be purchased separately, in addition to the Denon 3805. The microphone is already included in the purchase price of the Yamaha 2400.

 

[Jeff O.]

I am not an expert on this but there may be some confusion.



I think the 6 (or 4) ohm switch on the back of receivers actually limits the amount of current that the power supply can deliver. This prevents possible damage to the power supply and speakers. One side effect of this is that it limits the dynamic range that can be produced. For this reason I have seen some audiophiles suggest leaving at 8 ohms even if you are using speakers with less than 6 ohm impedance or less. I think it is a standard that is used by one of the consumer electronics agencies.

 

[Bob*S]

Jeff-

I'm not an expert either and I should have said "allows a amp to more safely drive 6 ohm speakers".

I know there is an issue with limiting dynamic range, but it doesn't seem like it's just the issue of limiting current since the amps have higher power ratings into lower impedance loads. Since voltage remains constant while watts increase, amps should also increase (if I remember any of my high school physics). I wonder if it has to do with some increase in the "floor" output since the lower ohms suck more amps which, in conjunction with the protection circuits on the amps, limits the delta between the floor and the ceiling currents. I guess I need to go read up on this now that my interest is piqued...or maybe I'll be lucky and someone here can inform me.

Bob

Well, I just found this little tidbit. Well, I remembered some of those HS physics but forgot that potentiometers usually regulate voltage. DUH!!

 

[Shiu]

If you read the HK's specfications (not sure about the 7200), their models are capable of high current but are not designed to drive 4 ohms speakers. Of course most receivers can drive 4 ohms speakers if you make sure you do not exceed the receivers power rating by simply not crank up the volume high. That means you need to be a little more carefual than if you were using 4 ohm capable receivers such as some of the NAD, Rotel model etc. Other than that, you would have to either go separates, or in the case of receivers that has the 6, or 4 (Sony ES) ohm selector switch you accept (I won't) the limited dynamic range and not realy gaining any power. I cannot understand why if the yamaha has such a switch and yet still give you more power. As Bob pointed out, you cannot drop the voltage and get more power, that defies physics. I have to assume either that switch does something different than we think, or Yamaha simply means if you keep the switch in the 8 ohm position you will get more power if you drive 6 ohm speakers. That I buy because it makes more sense, given that Yamaha does claim to have high current capability.

 

[Bob*S]

Shiu-

Upon researching this further, it's pretty clear that using the voltage switch is a means to protect the amps rather than doing anything to improve the speaker performance (as Jeff suggested). The general agreement is to not use it unless your amp's protection circuit is kicking in frequently or you amp is running really hot.

After thinking about this for a bit, I realize that I already knew the answer: The stated power output into 6 ohm loads reflects the high-current capability of the unit. An amp that is rated at 100w into 8 ohms but only 120 into six ohms has a lesser ability to drive lower impedance speakers than one which will reach 140 ohms into 6 ohms. This is important because a speaker's impedance changes at different frequencies. The added power as the impedance drops means that the speakers will play as loud (in theory anyway) as the ohms drop. I'm wondering if this is what is meant by peak-to-peak power.

I'm sure I only got a portion of this right and hope I can learn more about it.

Bob

 

[Shiu]

Bob, I agree with you. I just posted these numbers on another thread:

Sony 4ES test results (S&V)
Output at clipping:
1 channel - 171 (8ohms) 271 (4ohms)
2 channels - 140 (8ohms) 209 (4ohms)
5 channels - not tested, for reasons all those who dislike Sony have already cited. As for the 4 ohms ratings, I am sure the tests were done with the switch left in the 8 ohm position otherwise I doubt the Sony would produce such decent results.

This kind of results indicate some high current ability (perhaps better than the Yamaha 2400)but obviously not as good as something like an AVR7200 or separates, where one would expect the 4 ohms rating to be double that of 8 ohms rating. That's based on physics/electrical theory, power (watts)=current (Amps) square X impedance (ohms) X power factor (%). So if you half the ohms, double the current, the power doubles. Of course in real life applications things usually get much more complicated.

 

[Brent_j]

ok, you have my head spinning more ways than one. I think I am just going to wait until I get the Adcom, I am sure that is the missing component with my system.

I really do appreciate all the help in this matter guys!!!

Thanks!
Brent.

 

[DonnyD]

Yeah, I agree with you about adding an amp to your system to take care of the "main" duties........ I have an older Yamaha receiver (RX-V1) and although it is plenty stout on its own driving an a 9.1 channel config, when I put on an Acurus 200x3 to handle the mains and center duties, it seemed that the other channels were stronger or more dynamic...as it should be, since the Yami didn't have to drive as much..
BTW: I am counting 9 channels by:
2 mains, 2 rear surrounds, 2 rear centers, 2 front effects, 1 center.... and then of course a SVS Cylinder.....

 

[Shiu]

Brent, if the 3 channel Adcom you are looking at is rated 200W per channel into 8 ohms you will find that it can push 350 or more into 4 ohms because they are truly 4 ohms capable on a continuous basis, not just "high current" or "dynamic" power claimed by Yamaha and Denon. In fact, even my old GFA555 can drive 2 ohms speakers (again, continuous).

 

[Brent_j]

Thanks Shiu, After reading much on the subject, I am just going to leave everything at 8 ohms. It makes the most sense.

Thanks!
Brent.

 

[Shiu]

You're welcome, I am pretty sure you will get more power by selecting 8 ohms (i.e. no voltage reduction). Obviously if and when you get that 3 channel power amp (Adcom or whatever), you will appreciate your big RTi10 more.