Amplifier FAQ - Page 4

Thanks Mike:
I would think that for double the price there would have to be some advantages over the lower priced unit's. IDK

Thanks Michael J Human

Very informitive. I have been considering adding an amp to my setup and I needed more information when I stumbled across your thread.

So based on your thread here I could use a 50watt amp to power efficent speakers for a small to med size room. If I had a large room with vaulted celiengs then a 100watt amp would do.

Now if I had very inefficent speakers a 100watt amp would do a small room and a larger amp for larger rooms.

This is my understanding at this point of my learning curve, please correct me if I am wrong.

Thanks

Michael, this is very interesting reading on your first post but i would like to suggest a correction.
You say that every doubling of distance from the speakers decreases the SPL by 6 dB;
i think that this is exact for anechoic spaces, but for a home living room, it should be more like 3 dB's or so, depending on the size of the room and it's type of construction.

Very large rooms will have a comparatively (all else being equal) higher drop in SPL than small rooms.

The reason for this is the fact that sound in a room does not get lost in infinite space like in an anechoic room or outside on top of a pole, but is bounced back to the room by the room boundaries (walls/floor/ceiling).
Most of the loss happening in a room will then come from those reflecting surfaces absorbing a certain percentage of the sound, but will never approach the loss happening in open spaces or anechoic conditions.

Do you agree to that?

Have a nice day! :-)

you say essentially the same thing as me, and i agree with you.

i wrote in my previous post: "...depending on the size of the room and it's type of construction."
The type of construction i was referring to includes sound absorptive material of any kind.

i would add only one thing; in a room, the loss in SPL should almost never be as much as 6dB; it that would happen, it would be caused by such heavy sound absorption that the room would, in effect, be an anechoic room and all but unusable for enjoying A/V.

a balance of absorbtion and reflection is required - in-room specifications will always be higher than anechoic

It has been an absolute pleasure to read this OP as well as many of the later Q&A posts. I have a Denon AVR2808 and I have been contemplating whether I should be looking to upgrade my speakers next, or if I should upgrade to a separate amp for the fronts and use the Denon for only the rears, and this thread really helped me learn and understand what exactly to look for in an amp, and what the numbers really mean when comparing.

I'm now starting to think the amp is a better idea to start with because on top of any clarity I may hope to gain from my existing system, I think moving forward an amp will prove useful no matter which direction I decide to move next.

Thank you for this post.

Just wanted to say great job by OP on this FAQ. It's written in layman's terms so that most readers who don't have advanced EE degrees can readily understand the points...not necessarily easy to do.

A few observations & comments for your consideration:

1. I would add to your factors determining needed PA power: typical ambient noise level in listening room; the type of source material you typically listen to (well recorded symphonic music usually has much higher dynamic range than rock or pop music); the type of loudspeaker (planar/dipole speakers do not follow the inverse square law); and the minimum impedance of your speaker.

2. On the last point, I think buyers can get too reliant on the nominal impedance rating of loudspeaker systems. In reality, the input impedance of most all systems varies greatly with frequency, both in magnitude and phase angle. If your speaker system impedance curve has substantial dips below 4 ohms, you'd better know that your PA can supply the corresponding current, even if only for a few 10s of msecs. A PA whose max power rating may appear sufficient on the surface may be inadequate if it is current limited for the volume peaks you wish to listen to with high energy transients in those frequency bands.

3. While I agree that the ACD spec is a good and necessary measure of a PA's maximum steady state capability, we don't listen to constant amplitude sine waves. Especially for source material with wide dynamic range, and with very inefficient speakers in large rooms, the transient capabilities of a PA become very important. One of my older systems consists of Carver Amazing panel speakers which are indeed very inefficient. When I originally purchased them many years ago, PAs and receivers rated in excess of 200 wrms/ch would clip when listening to symphonic music on these speakers at high levels. I ended up buying a Class G PA available at the time which, although rated at "only" 100 watts rms/CH, was measured as delivering up to 1800 watts into 2 ohm loads for 25 msec -- something the other "more powerful" 200+ watt PAs could never begin to approach. The Proton PA was the perfect match for these speakers, as I could drive the speakers to prodigious undistorted SPLs for a few 10s of msecs with the right recording...which happens to be about how long most musical transients last. Moral of the story is ACD rms doesn't tell you anything about how the PA will behave playing music unless the peak output remains below the max rms value.

There's a graph of actual data in Toole's book "Sound Reproduction" on p. 60, Chapter 4. It clearly shows a loss of SPL with distance of -3dB/DoubleDistance from several living rooms. The data is from a report by T. J. Schultz, "Improved Relationship between Sound Power Level and Sound Pressure Level in Domestic and Office Spaces" combined with some of Toole's own data. The loss curve seems very robust to room type and source type once you get past 1m.

As a side note, I would suggest anyone serious about HT to read Toole's book. It's an eye-opener.

Help. Hi i have a Yamaha RX-V1700 Receiver which has suddely lost all power, totally dead. i have changed fuse on the main plug but no luck. is there an internal fuse that is easily accessable? Any other suggestions to get sorted

MichaelJHuman and contributors:

This is a great thread. Fantastic start and then some really good stuff that attempts to civilize us savages follows. Thanks to all, especially MichaelJ.

In other news: A Vatican Spokesman Father Arrivederci today announced the formation of a Babel Commission whose stated goal is to begin beatification process of one MichaelJHuman whose unflagging efforts to audibly uplift the sonically downtrodden has saved many. And much.
The distinguishing characteristics of this soon to be noted saint of the Audiophilic Universal Belief (from which The All Resounds) have been shown to be extensive knowledge of this Wondrous World of Aural Phenomena, a willingness to extend himself in the delivery of this Knowledge in a conversational and accessible tone, and in a manner otherwise truly appreciative of said Wonders.
The success of this long awaited AVS beatification campaign is assured due to the proven and documented occurrances of "Extraordinary Patience" when confronted by by the dumbfounded, deluded and even the oft-repeated appearances of the dedicated (and much feared) OBLIVIOUS ONE, who comes in many guises. These miracles have been witnessed by hundreds, nay thousands of the aVsaithful and will assuredly yield reward in all of the Worlds.

Back to our regularly scheduled programming..

Sincerely,

MKard ---

EDIT: Read the whole article...saw you getting frustrated at others posting questions in the thread but too late

Anyways, informative FAQ thanks for taking the time to put it together. I'll leave my original post here below alone if you care to comment that's fine, if not no biggie.

hey I enjoyed reading this (actually I still am) but had a question in terms of what the receiver can really output. I read the section where you state they artificially inflate the total power of the receiver (e.g. 135 watt X 7) as in the unit isn't likely sending this much power to all 7 at once so how would you interpret this from the website...they list each channel somewhat separately and don't necessarily claim it as all at once.

Onkyo TX-NR807
http://www.onkyousa.com/model.cfm?m=...s=Receiver&p=s

Front L/R 135 W + 135 W (8 ohms, 20 Hz–20 kHz,
0.08%, 2 channels driven, FTC)

Center 135 W (8 ohms, 20 Hz–20 kHz, 0.08%,
2 channels driven, FTC)

Surround L/R 135 W + 135 W (8 ohms, 20 Hz–20 kHz,
0.08%, 2 channels driven, FTC)

Surround Back L/R 135 W + 135 W (8 ohms, 20 Hz–20 kHz,
0.08%, 2 channels driven, FTC)

Dynamic Power 300 W (3 ohms, 1 ch)
250 W (4 ohms, 1 ch)
150 W (8 ohms, 1 ch)

THD (Total Harmonic Distortion) 0.08% (Rated power)

Signal-to-Noise Ratio 110 dB (Line, IHF-A)

Per 1 channel ?? That's how I read it am I wrong?

I'm thinking about adding an amp to my RX-V1800 before the end of the year... but is the RX-V1800 "enough" (pre-out section) to add and amp like an emotiva or outlaw or should I consider upgrading to a mid-price newer AVR as well. I don't "need" HDMI 1.4 or 3D for now I just want to be in the separates league. Thanks!

But are there not OTHER distinct advantages provided by the additional power than just volume that justify going with more power?

cougar

Did you get that last sentence right?