How many watts ?

stlrman · « **on:** 27 Dec 2011, 07:41 pm »

I am buying new monitors with a stated 86.5 db, 8 ohm.
How many watts do I need to REALLY drive 86.5 speakers? I want to be able to listen loud 95dbs for short amounts of time without clipping the amp.
Do I risk blowing the Raal Ribbon tweeter at these volumes? Can an underpowered amp lead to blowing a tweeter?
Should I be looking for high damping factor? What exactly is high damping factor? Should I be looking at 150 watts and up. I was hoping 80 watts would do it. I own a Jolida 1501RC 100 watts.
I want an integrated amp under $750.
I am looking at Onkyo 955a which is 85 watts. I am not sure about its damping factor. Another amp I am considering is Resolution Audio Opus 21 at 80 watts. I want a fast ,powerful ,amp, with little sound signature.
I am thinking of selling the Jolida to buy a class D amp.
I would appreciate any advice/suggestions.
Thanks,
Todd

Freo-1 · « **Reply #1 on:** 27 Dec 2011, 08:06 pm »

Keep in mind that you are more likely to damage a speaker by driving the amp into clipping than feeding it too many watts.

Given the speakers you are looking at, would recommed more wattage. Class D amps do provide a lot of drive for the cash. However, some people find the sound from them off putting, while others rave about them.

Damping has to do with control of the woofer. Most modern amps provide more than suffuicent damping.

Æ · « **Reply #2 on:** 27 Dec 2011, 08:13 pm »

For a second there, I thought you were saying that your loudspeakers are 86.58 ohms! Then I realized you meant 86.5dB, 8 ohms. Whew.
One can never have too much power, or one wishes he had more power.

Mike Nomad · « **Reply #3 on:** 27 Dec 2011, 08:14 pm »

Depending on what math you want to use, you can get a pretty wide swing on recommended power.

One rule of thumb on recommended amplifier power is to take the "RMS"/Continuous power rating of the speaker, and double it.

stlrman · « **Reply #4 on:** 27 Dec 2011, 08:40 pm »

Thanks for the replies folks!
So 150 watts sounds like a good starting point ? I am not sure my budget right now can afford that many watts.
Sometimes I put the amp up loud , say over 90spl and listen upstairs or from another room. When critical listening ,I would say I listen 85spl and under.
I thought d amps would sound clean, and not too much sonic signature.
Thanks,
Todd

Freo-1 · « **Reply #5 on:** 27 Dec 2011, 08:49 pm »

I tried a class D amp (Rowland Model 102). At first, it seemed pretty cool, as it sounded a lot different. However, as time wore on, I grew to notice that it had a lot of shortfalls, so I sold it and went for a Threshold S300 (which I restored, and was much happier with).

Here is a link to what the issues with class D amps entail:

http://www.hificritic.com/downloads/Class-D.pdf

Some folks do not agree with this, and that is O.K. Class D is one of those things that you either like it or do not like it.

JLM · « **Reply #6 on:** 27 Dec 2011, 10:22 pm »

80 watts = 19 dB of gain (add 19 to stated speaker efficiency). So you'll easily reach 95 dB in all but a really huge room.

Clipping (a nasty form of distortion) happens when amps are pushed too hard. Clipping is harder on speakers than over driving them with clean power. The double wattage recommendation is a good compromise between worry of clipping and the nearly limitless dynamics of digital sources.

Most references state that jazz/classical music peaks at 105 dB, rock at 110 dB. Most audiophiles I know listen between 80 and 90 dB (100 dB and above is damn loud).

timind · « **Reply #7 on:** 28 Dec 2011, 01:46 am »

What is your room size? That has to be considered, especially of the 80 watt amp is one of your choices.
I'm another one of those who tried class D amps, quite a few of them actually. I really liked some of them and others not so much. They do sound different, but that's the case with a lot of amps. No problem at all filling my small room.

stlrman · « **Reply #8 on:** 28 Dec 2011, 02:38 am »

Thanks guys!
My room is medium size living room, about 16x24.
I sit 8 to 10 feet away. I have a 12 inch servo sub sub with its own amp.
I am looking at a used Resolution Audio Opus 21 . 80 watts into 8 and 160 into 4
I can mellow with the volume a bit I'm thinking. I would rather have great quality sound to 95 spl
Thanks,
Todd

Chromisdesigns · « **Reply #9 on:** 28 Dec 2011, 02:42 am »

Consider buying used -- you'll save a lot of money by letting someone else take the depreciation. Use the difference to up the quality / power of the equipment you buy.

OOPS -- see you are already thinking this way. Smart!

timind · « **Reply #10 on:** 28 Dec 2011, 02:57 am »

Very interesting choice. I have been using a Resolution Audio CD-50 for about seven years now. Great cdp and a great company. If you go that route I would love to hear your impressions.

sturgus · « **Reply #11 on:** 28 Dec 2011, 03:14 am »

There are lots of ways to go. If it were me, I would use the Jolida for now and see what it does for you. You may find it works just fine. If you don't like the sound then you can start looking at different units. What speakers are you getting?
Sturgus

rodge827 · « **Reply #12 on:** 28 Dec 2011, 03:23 am »

Todd,
I could be wrong, but I think you need the Opus 21 CD player and Power Module to use the Resolution Audio 80 amp

. All the pieces except the CD player can only be used together. Contact RA about this they will be happy to help you out.

Where do the Monitors bottom out?
Where will the sub takeover?

I'm using a pair of monitors (86db/8ohms) that drop off at 100hz, and powered subs take over from there. The speaker maker suggested that 30 watts in class A, or good quality high current A/B would be plenty to drive them. Depending on where your monitors drop off you may not need all that much power.
My room is 15x21x8.25, and I listen at levels about the same as you.

Good luck,

Chris

JerryM · « **Reply #13 on:** 28 Dec 2011, 04:04 am »

Clipping has a lot to do with current draw. Also, a speaker's Ohm rating tends to be an average. (An 8 ohm speaker can drop to barely two ohms while playing some frequencies.) An amp that cannot provide enough current during these power-hungry passages will exceed its rated output and clip the sine wave.

Some amps clip gracefully, and kindly tell you to turn it down. Others go into full bore oscillation; when you finish crapping your pants about what's happening to your system (and then turn it down), one may may consider buying a high wattage, high current amplifier.

The moral of the story? 86.5 dB speakers are not models of efficiency. I, personally, would not be happy with 80 to 100 watts. I would want a high current amp that has at least 200 watts.

Congrats on the new speakers!!!

Have fun,

Jerry

Æ · « **Reply #14 on:** 28 Dec 2011, 12:25 pm »

Quote from: JerryM on 28 Dec 2011, 04:04 am

Also, a speaker's Ohm rating tends to be an average. (An 8 ohm speaker can drop to barely two ohms while playing some frequencies.)

A loudspeaker that drops to 2 ohms shouldn't be classified as 8 ohms, it's misleading, untruthful.
I always look at the DCR of the driver (midbass or woofer), it gives a better representation of the facts.
If you have a multi way loudspeaker and the woofer is 8 ohms but the tweeter is 2 ohms, I'd call that an 8 ohm loudspeaker, because the woofer is the dominant driver. If on the other hand the woofer was 2 ohms and the tweeter was 8 ohms, I'd call it a 2 ohm loudspeaker.

The trend I'm seeing is that a lot of loudspeakers should really be called 6 ohms, but they are still being referred to as 8 ohms.

Wayner · « **Reply #15 on:** 28 Dec 2011, 01:03 pm »

A loudspeaker's impedance is an average measurement. The impedance varies over the frequency range, usually rising quite high at the woofer's resonance frequency and, then it has a warble thru the rest of the frequencies. So, the end result is that the system, including cross-over effects, could vary from 35-40 ohms down to a couple of ohms, or more.

My Martin Logan reQuests will go down to almost 1 ohm at certain frequencies, and that makes most amps a miss-match with these speakers.

So speaker manfacturers post an "average" impedance rating. The other factor that has been touched on is efficiency. The higher the efficiency, the less power is needed to reach normal listening levels. So someone with a 90db/meter/watt rating could probably get buy with a 100 watt per channel amp. Someone with an 85db/m/w rating would need more power to achieve a relatively same SPL, so he may need 200 watts.

So, a balance of power is kind of important. But, my golden rule is to get the most watts per channel, and use your head about where the volume control is.

Wayner

JLM · « **Reply #16 on:** 28 Dec 2011, 01:38 pm »

Those nasty laws of physics can't be ignored. Increasing the volume (sound pressure level) by 3 dB (a perceived 50% increase) takes 2 twice the wattage and a 10 dB increase (a perceived doubling) takes 10 times the watage.

So you can see that wattage can quickly "get away from you". Unfortunately high efficiency speakers expose system noises, are typically "colored" (tonally distorted)/large/expensive, but that is the "easy" way around needing big amps. Besides low/average efficiency speakers typically aren't rated to handle gobs (a technical term) of power.

warnerwh · « **Reply #17 on:** 28 Dec 2011, 03:29 pm »

Yup you can go through the watts/current pretty fast. I'd not be happy with an 80 watt amp. It's always better to have a little more than you may need. I'd go with a 200 wpc amp. You can get them fairly inexpensively if you buy used. Same with a preamp. Look on Audiogon and the for sale section here. An Adcom amp or Rotel amp will work well and can be purchased for 500 or so. Of course you'll need a preamp but that can be also had for under 4-5 hundred for a decent one.

What also has to be considered is the distance from you to your speakers and room size. You'd be asking an awful lot from a little 80 watt amp. Every three feet you lose I think 3 db. So sitting at 9 feet from your speakers you lose an extra 6 db. You have to double the power for the first 3 db then double that for the next 3 db. Even a 200 wpc amp is just adequate if you ask me.

Btw damping factor is a non issue with almost all SS amps.

JLM · « **Reply #18 on:** 28 Dec 2011, 03:42 pm »

Try the Jolida first. Common wisdom says tube watts are worth twice as many solid state watts (mostly due to their "soft" clipping characteristics that provide some headroom).

Low damping factor amps have flabby/loose/exagerated bass. This can be an issue with tube amps, but if you have speakers without much deep bass - no problem. If you're used to that sound, solid state can sound downright anemic/constipated.

With your speakers and 80 wpc, you'll reach 105 dB. Extra wattage for headroom is valuable to provide an added degree of speaker control, but not a high value proposal. Better to invest in quality of sound or even a beefier power supply.

http://www.audiogon.com/cgi-bin/cls.pl?intatran&1328565986&/Edge-I3
http://www.audiogon.com/cgi-bin/cls.pl?intatran&1330130782&/Music-Hall-A15.2-L-1

Æ · « **Reply #19 on:** 28 Dec 2011, 04:04 pm »

Quote from: warnerwh on 28 Dec 2011, 03:29 pm

Every three feet you lose I think 3 db. So sitting at 9 feet from your speakers you lose an extra 6 db. You have to double the power for the first 3 db then double that for the next 3 db.

INVERSE DISTANCE LAW

In acoustics one usually measures the sound pressure at a given distance r from the source using the 1/r law. Since intensity is proportional to the square of pressure amplitude, this is just a variation on the inverse-square law.

In acoustics, the sound pressure of a spherical wavefront radiating from a point source decreases by 50% as the distance r is doubled; measured in dB, the decreases is 6dB, since dB represents an intensity ratio. The behaviour is not inverse-square, but is inverse-proportional.

http://www.sengpielaudio.com/calculator-distancelaw.htm