Volume Controls better @ 11:00 and above

So that's why the studios were fitting Canford 35 watt utility amps regardless of speaker rating

"More power is always better" - great advertising slogan, as well as being utter BS.

Paul H wrote: Here's some advice I found on the net, just by way of example: Zak: But once you're aware of all this you still need to figure out just how much power you need to drive your speakers. The first thing to remember is that it's better to have more power. Ken: Right. You want your amp to be able to play all your music, loud and soft, without distortion, and be able to handle sudden changes in volume easily. Zak: Yeah, and more power gives you just that. It's something that we call "headroom." Ken: As a starting point consider the RMS power ratings of your speakers or subs. Match or better yet, exceed the speaker power ratings with your amplifier. Zak: For example, to get that headroom, if you have a subwoofer that handles 200-watts RMS, power it with an amp that puts out 250-watts RMS. Ken: It'll drive it cleanly and without distortion, especially when the volume is cranked and it'll do it better than an amp with less power. More power is always better.

The above is just the falsehood being promoted today that does not have any real basis in physics or sound reproduction engineering.

 Quoting myself: "The "old" knowledge is being whittled away by falsehoods in today's world. "More" of anything is not always better."
 The only fact supporting the "more power is better" idea is the fact that you can hear the almost "bottomless" sound coming from your speakers.
 This is ignoring the speaker's efficiency and thinking that the effortless delivery of sound is being controlled by the amplifiers power. The speaker is the final transformation of the electrical sound energy... it is the weak link. If the speaker cannot produce the sound you want to hear, the amplifier cannot make it sound any better.

 The "headroom" is not in the final power output rating of your amplifier, it is designed into the output circuitry and the power supply supplying it.
 A 100 watt amp would be able to deliver 200 to 300 watt instantaneous peaks, if well designed, and still have low distortion and no clipping.
 Power supplies that are well designed for power amplifiers will be designed to supply 10x the current required for the  designed power rating... giving more than enough "headroom".

 250 watts is not going to have any more control over driving your speakers than 50, 100, or 200 watts. It is the quality of the design that makes your amplifier sound as good as it does and how well it drives your speakers.

 Those who have more power than they need can keep their beliefs about power requirements. Just always remember to keep the volume down to avoid risking blowing your speakers... it can happen with one slip on the knob.

Here would be good for some "old" knowledge (I have stated elsewhere).

Old school of thought is: any power amp with less than 1 watt was considered low power,
 from 1 to 10 watts was considered medium power,
and any amp putting out more than 10 watts was considered high power.

Speakers are rated in power and decibels, so therefore we use the following formula to calculate a change in
Decibels related to power:
(found @ http://www.radio-electronics.com/info/formulae/decibels/decibel-formulae-equation.php )
 

Where:
    Ndb is the ratio of the two powers expressed in decibels
    P2 is the output power level (in watts RMS)
    P1 is the input power level (in watts RMS)

and "log 10"  shows this to be a logarithmic formula in base 10
If the value of P2 is greater than P1, then the result is given as a gain, and expressed as a positive value, e.g. +10dB. Where there is a loss, the decibel equation will return a negative value, e.g. -10dB.

P1 = 1watt in , P2 = 10watt out... then Ndb would be = 10 dB.

So how much louder in dBs is 100w over 10w? ... 10 db.          over 1w?  ... 20dB.

OK ... watts x 10 adds 10 dB, that is for each decade.
@   0.1 watts      we start at           0 dB (arbitrary point to start) 
0.1 x10 = 1.0watt add 10 dB              10 dB more than 0.1 watts
1.0 x10 = 10 watts add 10 dB            20 dB more than 0.1 watts
10 x10 = 100 watts add 10 dB          30 dB more than 0.1 watts
100 x10 = 1000 watts add 10 dB     40 dB and so on.....
(note that speaker SPL rated in dBs is directly related to this also)
My point is this... you are not going to get much more sound until you make your power 10x as much!
  3 dB is the smallest change in sound level that is determinable.
10 x 2 = 20 watts... add 3 dB
20 x 2 = 40 watts......"....."..........40 watts is only 6 dB louder than 10 watts.
Again, Old school of thought is: any power amp with less than 1 watt was considered low power,
 from 1 to 10 watts was considered medium power,
and any amp putting out more than 10 watts was considered high power.

Medium power, >1w, was good for paging systems, table radios, TVs, etc.
High power, >10w, was good for big venues like churches, auditoriums, schools, etc.
Those figures were considered enough for the intended uses.

BAK wrote: My point is this... you are not going to get much more sound until you make your power 10x as much!

Perfectly true. 10 times the power gives twice the loudness, and always has been and always will be.

Loudness is also known as sound pressure level (SPL) and to install public address (of any quality) you have to know how SPL works.

I've never met anybody in hifi who has even the basic understanding of sound pressure levels and how to calculate them.

If you go on an install it simply has to work right out of the box.

So to continue on from Bruce, twice as loud as 10 watts is 100 watts, and twice as loud as 100 watts is 1,000 watts (1kW).

As a youth I made a 2 watt/channel amplifier and mounted a couple of 4 inch car speakers in closed box enclosures (infinite baffles). The average sized lounge was filled with sound, but that isn't all that surprising when a five watt 100 volt line speaker can be heard all over a cash and carry warehouse. With 100 volt line a 5 watt speaker will only ever do 5 watts no matter the wattage of the amp (as long as it's above 5 watts that is).

And as for you needing 250 watts just because the speaker can handle it - what bullsh*t!

OK, if your lounge is the size of a lecture hall then maybe. I put a 250 watt / channel Inter-M power amp in one which it didn't really need but it looked good to the client. It mostly got used at half volume. And anyone understanding the audio taper of volume controls will be able to work out the wattage at half volume... 3 watts!

OK, so what about headroom? Well, recording studio PPM meters red line at +8dB which is two and one half times more in voltage terms. 3 watts into 8 ohms is 5 volts, so you need 12.5 volts for peaks. 12.5 volts equates to 20 watts into 8 ohms.

Ask the caretaker what Won't Get Fooled Again sounded like? We were both doing air guitar at the back of the hall when a guy came from the third floor to complain at the noise!!!

I could have rated the speakers at 4 Ohms and used a pair of Proprius to obtain 45 WPC (if they'd been around at the time) and still have had power to spare.

And that's why they used the Canford 35 watt utility amps in commercial broadcast studios throughout the land...

...and I designed that too!



Edited by Graham Slee - 24 Mar 2016 at 8:31pm