Understanding power rating garble

[pemike1973]

Hi, this is my first post, and to start of I have a question that may seem a bit dah..

I have a yammy rx-v650, driving wharfedales 8.4 and 8.2 speakers with a rather low sensitivity (88 db).

The power ratings on the yamaha are as follows :

Maximum Output Power
(8 ohms, 1 kHz, 10% THD)
Front Channels 135 W + 135 W
Center Channel 135 W
Surround Channels 135 W + 135 W
Surround Back Channels 135 W + 135 W

Dynamic Power (1 kHz,)
86/4/2 ohms 130/165/195/240 W

Do I have enough "power" to drive these speaker at loud levels ?

Thanks

 

[Takeereasy]

Unless you are in a very small room I think you'll need a receiver with more power. Wherever you got those specs for the Yamaha provides some horrible info. Power should be measured in 20khz not 1khz. It should also be measured with a distortion rating of less than .1% not 10%. 10% distortion is an insane measurement. I don't know if I've ever seen a number that high yet used in a receiver measurement. The info that I found showed that Yamaha at 95w a channel, but the didn't say how that was rated either. Also the info I found on the wharfdale diamonds showed them as having a sensitivity of 86db and 6 ohms nominal 4 ohms minimal. Those are some power hungry speakers. The bookshelfs might be fine but those towers would be better served with some more power IMO. In a small, make that tiny, room you might be ok. Maybe.

 

[markw]

I'm both surprised & aghast that Yamaha publishes specs with 10% distortion ratings.

That's unheard of except maybe for boom boxes and car car audio.

This "so many watts at 1khz at 10% distortion" figure will always return a highly inflated figure.

What do the more stringent specs say? You know, with less distortion, across the full range, and things like that.

Offhand though, I'll take a stab and guess that unless you live in a stadium and want ear shattering levels constantly, you should do well.

 

[pemike1973]

after some searching on the net I came up with these specs for the yammy:

Number of Channels 7.1 Channels
Surround Mode Power 95 Watt @ 8 ohm, 20 Hz - 20 kHz, THD: 0.06%

do you think I would be able to power those "hungry" speakers ??

Thanks

 

[Buckeyefan 1]

As the others have said, and

If you are having trouble driving your Wharfdales, you'll need to upgrade your receiver to a near top of the line like the Yamaha 2500 (and that may not even be enough power since that unit is not rated to run 4 ohm speakers). Depending on your budget, and how long you've had your Wharfdales, you may be better served trading in your speakers for ones that are more sensitive with an 8 ohm rating.

As to your question "Do I have enough "power" to drive these speaker at loud levels ?"; I'm assuming you've already answered that question with your post, right?

 

[pemike1973]

If you are having trouble driving your Wharfdales, you'll need to upgrade your receiver to a near top of the line like the Yamaha 2500 (and that may not even be enough power since that unit is not rated to run 4 ohm speakers). Depending on your budget, and how long you've had your Wharfdales, you may be better served trading in your speakers for ones that are more sensitive with an 8 ohm rating.

As to your question "Do I have enough "power" to drive these speaker at loud levels ?"; I'm assuming you've already answered that question with your post, right?

Well to be frank, I´ve not gone over -6 db, and at that level the sound was "pretty" loud, not ear bursting loud but loud.

The db scale on the yamaha goes to +18 db, I do not know where the -6 db is situated with respect to power, is the amp at almost 100 % power ??

I am a newbie at this (as you´ve probably already figured out) and was used to having a dial on the hi-fi that went from 0 to 20 , can you shed any light on this matter. (Is -6 db "pushing" the amp) ??

Thanks

 

[Audiacc]

dB as such does not mean anything. It is a reference value. If you have proffesional equipment dB rating is differnet compared with home hifi - as the basic unit is different (e.g. 0.775 Volt vs. 1 Volt) Actual information on loudness would be referenced by dB SPL, in simple words: a meassure of air preassure in the distance of 1 meter from the speaker
Go check http://www.phys.unsw.edu.au/~jw/dB.html if you are interested, or simply rely on your ears. You know if it is loud

 

[Takeereasy]

If it plays loud enough for you and there is no audible clipping then you most likely are doing ok IMO. One quick test would be to play some multi-channel audio and movies for a few hours at whatever volume you usually listen at. Then feel the receiver. If it's hot enough to fry eggs on you're most likely over-working the poor guy. If it's only a little warm then you should be fine. The more juice you have to feed the speakers in order to get them to the desired listening level the harder the amp section is working. You just need to avoid working the receiver too hard and you'll be fine.

 

[pemike1973]

Thanks for the response, with regard to the speaker sensitivity, does buying a higher sensitivity speaker mean better sound quality, the wharfedales have very clean sound, although I have not gone over -6 db setting on the amp the sound they produce at this level is very neat and clear.


Thanks

 

[Audiacc]

"This now brings us to loudspeaker sensitivity, sometimes also erroneously called efficiency. Sensitivity is simply a spec that tells us how loud a particular speaker will play given a standardized amount of amplifier power. The industry standard is to present an 8-ohm speaker with a 1 watt (2.83 volts) input signal and measure its output in an anechoic chamber with a microphone at a one-meter distance (an anechoic chamber is a specially designed room that completely absorbs sound). The resultant spec will read something like 89dB @ 1W/1m. This means that for 1 watt of input of amplifier power the speaker will output a sound pressure level (SPL) of 89dB heard at a distance of one meter in front of the speaker. Speakers that output lower SPL levels for a given input have lower sensitivity, while speakers that output higher SPL levels have higher sensitivity"

copypasted from http://www.goodsound.com/howto/2001_07_01.htm

In other words: more detail is present

...or if you refer to the frequency range within which speakers are able to operate : yes, sensitivity would mean they are able to convey signals from the given range. The wider the better. Manufacturers know about that. So their specs read some absurd ranges like 20Hz-20kHz for 100$ speaker set...(biased measurements)

Again, your ear shall be the judge

 

[Buckeyefan 1]

Thanks for the response, with regard to the speaker sensitivity, does buying a higher sensitivity speaker mean better sound quality, the wharfedales have very clean sound, although I have not gone over -6 db setting on the amp the sound they produce at this level is very neat and clear.
Thanks

No, higher sensitivity does not equate to sound quality. Just sound pressure at a given distance. Some highly sensitive speakers sound great up to a given dB, then distort very quiclky thereafter. Some low sensitive speakers sound horrible at low volumes, but when fed enough current, open up and sound wonderful. One of the hardest things to do in the audio search is picking out speakers that compliment your receiver/amp. It's one thing to make sure your receiver/amp can properly power your speakers, it's another thing to enjoy how they sound coupled up with your unit. Most local retailers know this, and will allow you to bring home equipment to demo. I'm a proponent for higher amplification. The less distortion you introduce into a speaker, the better it will sound. Get as much receiver/amp as you can afford, then the search for speakers won't be as difficult as you now have the option of comparing 4/6/8 ohm speakers at lower sensitivity ratings. Entry level receivers won't do a set of Axiom towers justice. They may sound fine at low levels, but when you decide to crank it up or listen to H/T at higher volumes, they won't respond as they should.

 

[Takeereasy]

does buying a higher sensitivity speaker mean better sound quality

Not at all. Some of the most highly regarded speakers in the world have an impedence of 2 ohms and are 84db. That kind of sensitivity requires massive seperate amps to reach the speaker's potential, but what a potential it is. That is not to say that a high sensitivity speaker is inferior either. There are also very highly regarded speakers that are 8ohms and 98db that can fill a room with sound using a 10 watt amp. What you are looking at is just two very different design techniques. Your speakers tend to fall a little more into the inefficient bracket in my opinion, but not drastically so.

Your Wharfdales have a great reputation online, and the brand itself seems very well respected. I'd keep those guys if I were you. One thing you may want to do in the future though is add an outboard amp. I looked up your receiver's manual and the 650 has pre-outs. At a later date you might consider picking up a nice 125w a channel stereo amp off of ebay to run your two fronts and see if there is an improvement. I'm betting there would be.

 

[pemike1973]

Thanks, I will try and purchase a stereo amp for the fronts. Let me just get this straight, the yamaha will feed the two front channels through the pre-outs and the rest of the cahnnels I will leave to the yamaha, right ?

Do you have any make or model in mind ?

 

[Takeereasy]

Yes, you are correct about how this works. You will run two rca cables (nothing fancy, just 2 good quality 75 ohm rca cables) from the pre-outs to the ins on the amp. A good trick I've found to save cash is to purchase composite video cables to use as my RCA cables. I picked up a 14' Monster cable with the nice thick braided jacket for $4 once. Here's and Example of what I mean. I was suggesting this amp upgrade for later down the road though, don't feel a ton of pressure to do it now if you don't have the cash.

If you go used you might want to look at Marantz, Nad, Parasound, Adcom. All of these companies have decent stable receivers that last forever and can be had cheaply (sub $200). Check sites like audiogon.com and ebay.

Parasound
adcom
another adcom

 

[Buckeyefan 1]

Thanks, I will try and purchase a stereo amp for the fronts. Let me just get this straight, the yamaha will feed the two front channels through the pre-outs and the rest of the cahnnels I will leave to the yamaha, right ?

Do you have any make or model in mind ?

I was checking out the two channel power amps on ebay, and ran across this. Matching system!
http://cgi.ebay.com/YAMAHA-M-60-POWER-AMPLIFIER-AMP-200WPC-BEAUTY_W0QQitemZ5796481492QQcategoryZ71550QQrdZ1QQcmdZViewItem

Here's another little beauty.
http://cgi.ebay.com/Sansui-BA-F1-Stereo-Power-Amplifier_W0QQitemZ5796999614QQcategoryZ39783QQrdZ1QQcmdZViewItem

This will do well also with your Wharfdales:
http://cgi.ebay.com/Harman-Kardon-HK-870-Power-Amplifier-100WPC_W0QQitemZ5796714295QQcategoryZ71546QQrdZ1QQcmdZViewItem