Optimum power

[02audionoob]

I saw a document on the JBL website that said you should choose an amp that can deliver twice the continuous power rating of the speaker system.

http://www.jblpro.com/pages/general_faq.htm#How%20do%20I%20choose%20the%20righ t%20amplifier%20power%20for%20my%20speaker%20syste m?

Any thoughts on that?

[Mr Peabody]

That's an interesting rule of thumb. It is true though that most speakers are blown by under powering them opposed to over powering them. As you turn your amp up, at some point it will begin to lose clarity, if you were looking at the amp's wave form on a scope you would notice the line of the curve becoming jagged. This distortion is called "clipping" and it's this distructive occurance that blows your speakers.

I guess they figure if you have enough power you will be satisfied before you blow the cones off their baskets :)

Also, what goes for JBL may not necessarily be for every speaker brand. But it is a fact that NO speaker likes or will with stand much clipping before damage will occur. Some entry level speakers build in protection circuits which will shut off the speaker before damage.

[Feanor]

I saw a document on the JBL website that said you should choose an amp that can deliver twice the continuous power rating of the speaker system.

http://www.jblpro.com/pages/general_faq.htm#How%20do%20I%20choose%20the%20righ t%20amplifier%20power%20for%20my%20speaker%20syste m?

Any thoughts on that?

The continous power rating of speakers is mainly relevant in a professional, sound reinforcement setting. For home use it is the perhaps the most irrelevant specification quoted for speakers. What is true, however, is that you can have an amp rated much higher than that max power rating and benefit from it.

The amount of power you need depends on the efficiency, (a.k.a. sensitivity), of your speakers, the size and furnishings in your room, and how loud you listen. The last is a factor that is sometimes over looked when advice is given. For example, my average listening level is never above 75 dB (and usually <70, though peaks might be 12-15 dB higher that average). A person who likes 80 db average will require about 3x the power.

[Mr Peabody]

I feel continuous, RMS, is important if it's a manufacturer you can depend on to tell the truth. Continuous is more a true power rating than "peak". If you mean in terms of purchasing a speaker, I don't think people get too caught up in power handling, especially when looking for more higher quality speakers. It would be sensitivity and if the speaker had a relatively stable impedance.

Some manufacturers tend to exaggerate and others are conservative. Off the top of my head I'm not even sure what the power ratings are on a Dynaudio Audience series but I've seen them driven by huge Krell amps to extreme levels without a crack in the sound. I know they weren't rated to handle that kind of power.

If a speaker was rated at 100 or 200 watts continuous, I don't think anyone would listen at that volume continuously. As I type I think I'm beginning to understand what you said Feanor.

[BRANDONH]

The pros say 4 x greater is ok preferred even
5 x the speaker rating power will surprise you.
I am running at least 5 x the driver rating and have not blown a driver yet and I drive the heck out of them.
When it was underpowered that is when I would blow tweeters and many drivers and melted networks.
The overhead gives you speaker control with the right amount of power the speaker can be driven and controlled better at low volumes
don't mistake power for loudness.

So yeah go for it.

[02audionoob]

When I was away at college my stereo stayed at my brother's house the first semester. It was a Marantz 2325 (125 wpc) and a pair of AAL 3-way speakers, which I think are rated at 75 watts. My brother tore them up and at the time I didn't understand what went wrong with the speakers so I took them back to the dealer over the holidays for warranty repairs. The dealer was kind enough to replace some of the drivers but the technician made a note on the receipt that they had been overdriven and wouldn't be covered for that issue again.

When I bought the speakers, I had no idea about the power rating of the Marantz or any rules of thumb...I just told the salesman what receiver I had and asked what speakers he recommended in my price range. I also didn't know my brother would turn it up so loud. That said, I've never had the Marantz volume above high noon, but I don't know how far it was turned up when the speakers were destroyed. I didn't ask...I just hauled it all up to my tiny, ratty apartment as soon as I got my speakers repaired.

[BRANDONH]

When I was away at college my stereo stayed at my brother's house the first semester. It was a Marantz 2325 (125 wpc) and a pair of AAL 3-way speakers, which I think are rated at 75 watts. My brother tore them up and at the time I didn't understand what went wrong with the speakers so I took them back to the dealer over the holidays for warranty repairs. The dealer was kind enough to replace some of the drivers but the technician made a note on the receipt that they had been overdriven and wouldn't be covered for that issue again.

When I bought the speakers, I had no idea about the power rating of the Marantz or any rules of thumb...I just told the salesman what receiver I had and asked what speakers he recommended in my price range. I also didn't know my brother would turn it up so loud. That said, I've never had the Marantz volume above high noon, but I don't know how far it was turned up when the speakers were destroyed. I didn't ask...I just hauled it all up to my tiny, ratty apartment as soon as I got my speakers repaired.

I should have added that a speaker can still be blown.
If driven hard enough and long enough the driver motors will become stressed and overheated.
Now with an amp that is at 125 watts per ch it does not take much more than 12:00 on the dial to clip that amp beyond its limits so it clips a lot sooner than a high powered amp will clip the longer the amp is driven beyond its limits the hotter is gets and then can damage the amp its self.

At 2:00 (well into the 2000 watt range) my unit does not clip but man at that volume it can damage your hearing and it can be heard clearly for a long way off (I live in the country) but it will not damage my drivers, but they were build for that sort of thing. :3:

At normal listening levels where I am not drawing full power, the amplifiers will drive the speakers with ease and reveal details that could be only heard at higher volumes from lower powered units...so I can hear it sooner at lower volumes but will not become distorted if I wish to crank it up.
But for the majority of people a 125 watt amp will suffice and will suit them just fine

[E-Stat]

I saw a document on the JBL website that said you should choose an amp that can deliver twice the continuous power rating of the speaker system.
Clipping is clipping - don't do it. Get enough power or weigh the qualitative vs. quantitative tradeoff for your situation. Power isn't everything. Your Adcom amp is a solid middle-of-the-road product designed (but not built) by Nelson Pass. Someday you might try listening to a Threshold or Pass Labs amp for comparison.

rw