Axiom Home Page Forums General Discussion Advice from Axiom Owners Help! I think I need more power.

I’m pretty sure my poor Denon 2807 is falling short of the task of powering my speakers now that I’m out of the apartment and in a larger living room.

First some basic questions:

Is the information about listening levels and headroom for various type of music given on this site reasonably accurate:

How Much Amplifier Power Do I Need?

If given good info is this calculator realistic:

Amplifier Power Required

Until I completely set up the room I won’t know the exact speaker distances I’ll end up with but these numbers are most likely how far they will be from the primary listening position:

Mains/Center = 10 feet
Surround Sides = 6 feet
Surround Backs = 8 feet

The side and back surrounds may even end up farther if I ceiling/wall mount them instead of using the stands.

The loudest average SPL I typically use is 80dB.

I listen to everything except country and rap but I think the classical is probably the most demanding. Crown claims that classical music can have up to 25dB peaks so I used this number for the amplifier head room.

I ran the numbers assuming both worst case sensitivity 91dB and best case 95dB and came up with the following:

91dB
3 x M80s = 279w
2 x QS8 sides = 100w
2 x QS8 backs = 178w

95dB
3 x M80s = 111w
2 x QS8 sides = 40w
2 x QS8 backs = 71w

So even in the best case I think I’m going to need help powering the 3 M80s up front and will likely in the worst case or even somewhere in between need more power for the surround backs and possibly the sides.


A couple ideas I’m considering are getting the Outlaw 997 paired with the Axiom A1400-8 or a mid level Denon Receiver paired with the Emotiva XPA-3.

Any suggestions on other options to look at and the relative advantages/disadvantages of them are greatly appreciated.

More power?

Where is Tim Taylor when you need him...

Looks like he's going to play with some huge nuts.

Dean, as I've commented here before, the Crown discussion appears to somewhat nonsensically attempt to relate suggested amplifier capacity to the power handling ability of the speakers, e.g., 2 or 4 times might be suitable. This makes no sense because far less than the amount which the speakers can handle(which typically are in the hundreds of watts)might be actually used in typical home use(not the pro applications they emphasize).

The calculator there also doesn't seem to give realistic results. In Dr. Toole's book he cites studies indicating that in typical listening rooms the overall volume loss is about 3dB per doubling of distance. If we use a 91dB sensitivity number for the M80s, the loss at about 10' would be about 4dB, i.e., a level of about 87dB per watt. You want to use a 105dB peak, although I can assure you that few if any of even the most dynamic classical recordings have a dynamic peak 25dB above the average level. In a recent issue of my AES Journal, a group of CDs was analysed for dynamic range. The highest shown was about 18dB and what was rather amusing was a very uniformly loud rock item which had a dynamic range of essentially zero.

Be that as it may, using the 87dB per watt number at 10', 100 watts on a peak having a duration of likely much less than a tenth of a second would allow for playing the peak at about 107dB.

Thanks John. I figured there little calculator was a bit too easy.

I’ve read these articles by Alan.

Surround Sound A/V Receiver Buying Guide

Secrets of Amplifier and Speaker Power Requirements Revealed

In one article Alan suggests that the SPL weakens by 6dB for each doubling of the distance which would be a drop of about 9dB at 10 feet which assuming worse case 91dB - 9dB = 82db with 1 watt. So even assuming the higher weakening of the SPL with distance 100 watts should be able to deliver about 102dB which is still above the 18dB peaks you mentioned.

If 100 watts per channel is sufficient to get the SPL I’m looking for how do I go about finding something that can actually deliver 100 watts to all channels simultaneously.

My 2807 seemed capable of diving 2 x M80s and 2 x QS8s in my apartment w/no speaker more than 6 feet away at the 80dB average while still sounding good during peaks like the cannon balls crashing through the decks in “Master and Commander.” However, here in the house with more distance running 3 x M80s and 4 x QS8s it’s painful to listen at an 80dB average when the peaks hit.

Besides finding a review of an AVR that tests it with all channels driven is there any way to ferret out the true “all channels driven” power rating of and AVR?

Using Denon as an example the price goes up very quickly as the power rating goes up. Obviously I would prefer to not have to pay for power I’m not going to need but I also don’t what to buy something and be left wanting.

The other factor I was considering is paying to buy power over and over again. I’m not sure what the lifespan of an amp is, but might it not be less expensive in the long run to buy separate amp power that’s sufficient and then just upgrade preamp/processors as desired to keep up with the latest and greatest technology thus avoiding paying for the power section of the AVR with each upgrade?

Thanks for the feedback.
Dean

As long as he brings Heidi he’s welcome

A good amp, built with quality components should last a very long time. That's the direction I'm headed. My Pioneer receiver has 7 (8 including the sub) pre outs, so once I'm done upgrading my speakers I'll be looking for an amp or amps to take over the heavy lifting. Then I can move to a straight pre/pro and never look back.

Hi Dean,

The figures I mentioned in my article are the theoretical decreases in SPL with a doubling of distance, but since Floyd Toole was (is. .) my mentor, I'll certainly yield to his research and the figures quoted in his excellent book.

However, I'd point out that there is a lot of variation in personal preferences of playback levels. Even when I was on the NRC listening panel with Floyd Toole, my colleagues, including Floyd, listened louder than I did. I'd often sit farther back in the room to reduce the SPL at my seat. On average, I'd estimate they preferred playback levels at least 3 dB louder than what I was comfortable with.

In terms of my Axiom colleagues, I joke about some of the playback levels they like, which I find "deafening", at least 6 dB to 10 dB louder than my preferred settings (a 10-dB increase in loudness is subjectively termed "twice as loud"). And the playback levels they like are not uncommon--visitors to the listening room at the factory (of all ages) tend to use higher playback levels.

So factor in your own preferences, as it seems you have.

Regards,

Alan

Just remember that Crown sells amps. Of course they want you to believe you need more.

I suggest you try your current amp in the new place and see if you like it. If it under performs, then replace it.

BTW, IMO, you will have plenty of power (I just love TLA's ).

Isn't this where Wid chimes in about Rotel?

No, wait, this is where Randy talks about being so satisfied with Odyssey.

All threads lead to ecommerce.