View Full Version : How Much is Enough?

01-18-2011, 02:14 PM
Hi All:
I've been having a on going discussion on power requirements to sufficiently drive a pair of L 112's. My neighbor ,says that 200-275 is needed to get there full potential. His reason being that there rated at 300 watts. But I run all of mine with way less, and they sound fine.
I've tried to tell him that I'm not in a concert hall,but my basement,and 85 wpc will produce more volume than what I want to hear,let alone what the neighbors want to hear. I've got 1 pair running on 85wpc,1 pair on 120wpc,and can't really hear any difference. They both get real loud. So all you L 112 owners let me know how much power are you running?

Thanks to all

01-18-2011, 02:53 PM
By analogy, I can say (and have said here, in years past) that going from a
high-current capacity 70w/ch (140 into 4 ohms) amp to a 200w/ch (measured
at more like 300w/ch) amp into a pair of L150A's was indeed a step up...
having nothing to do with how loud I could listen (never got anywhere close
to clipping with either amp).

Other variables include output device type (bipolar vs mosfet) and output
protection... the smaller amp may have had output limiting (transistor SOA)
where the larger amp was build more in the 'build it beefy, to hell with current
limiting' school of thought. Also, the smaller amp had "tighter" voltage rails,
where the MOSFET rails were allowed to float up a bit between current hits
(cheap increase in dynamic headroom).

I don't have a good explanation, as it's "only" a 6dB increase in capability,
but it was an experience noted by inexperienced listeners as well (at least
I don't think I was just being humored :)).

I'm actually "happier" with your result, in that it is more like what I would have
predicted if the same amp were just run with higher or lower voltage rails and
biasing kept essentially the same.

L112s? I'm running those with an old JCP 75w/ch receiver ... plenty loud in
a normal-sized room... even if I turn on the "loudness" switch :p.

01-18-2011, 03:22 PM
The purpose of powerful amps is not necessarely to play loud, but to have headroom.

If your musical program is 10W average (loud enough) and you want 3dB headroom, you need an amp that can deliver 100W.

In the SR world we use amplifiers that are more powerful than the rated musical power of the speakers.

01-18-2011, 03:35 PM
1) 10W would be 100+dB SPL at 1m ... average, if you like
2) +3dB is 2x power, not 10x
3) +10dB is roughly twice as loud (as we perceive it) ... perhaps that was what was meant above.

01-18-2011, 03:57 PM
So, it would be safe to say that at my listening levels which are relatively low,I'm not experiencing any distortion,or fuzziness out of the speakers,not even close to clipping,I should be fine with power I have?

01-18-2011, 06:23 PM
2) +3dB is 2x power, not 10x.

DANG! you're right that was a major brain fart from my part.
I am truly ashamed of myself :o:

10x is 10 dB.

I shall be whipped with oxygen free monster cable at dawn :o:

The worse thing is that I work with dB s everyday of my life!

01-18-2011, 06:24 PM
Now when I re-read my post it jumps right at my face :(

01-18-2011, 08:02 PM
How Much is Enough?

As much power it takes for you to enjoy your set-up. Me I tend to under power according to max power ratings as I don't really play things all that loud. As long as you have enough power to give you additional headroom so you don't start noticably clipping the amp you should be fine. In my active set-up I use 100 watts per driver which is less that the max power ratings on both the woofers and midranges. I can hit 115bd peaks cleanly which is 10db over reference level for HT where I sit. That's more than enough for me and with the headroom it's always clean as a whistle.


01-18-2011, 08:51 PM
Me, I tend to use the largest amplifier that is feasible. JBL recommends 3db above rated power but I find that some peaks, even when the program is fairly low, WILL cause an amplifier to go to maximum output and if it cannot reproduce that peak, WILL be noticable.

Therefore I make sure that 600 watts is available to each 15 in a biamped monitor..300 to the 10's and 150 to each 4" coil HF driver. it is noticable and consumer HIFI amplifiers are just not up to the task.

And forget about the 10%+ distortion micro powered tube amps. They are great for sound producing, not reproducing.


01-19-2011, 07:35 AM

I shall be whipped with oxygen free monster cable at dawn :o:

Naw, you would have to actually break something to deserve such punishment. You may have to go out and buy some however. ;)