Audio Systems/power amplifier


QUESTION: i am running professional public address music system.
my question is that if my power amplifier give 1120 watts at 4 ohms and i connect 600 watts (300+300) at 4 ohms and i keep input signal maximum but just under clip light then is it safe for my speaker or more chances of burn out of speaker? in other way without clipping speaker burns?
and my second question is that i read following detail of transformer is it correct? and is it applicable to now a day power amplifier transformer?
if input level cut by db         power loss         efficiency
         0.5 db          12.5%          87.5%
         1.0 db          21.0%          79.0%
         1.5 db          30.0%          70.0%
         2.0 db          37.0%          63.0%
         3.0 db          50.0%          50.0%
if this is correct and applicable to power amplifier transformer then for 600 watts (300+300) at 4 ohms can i cut the input signal by -1.0 db and then out put reduce by 21.0% 1120 watts at 4 ohms reduce to 885 watts at 4 ohms. is it correct calculation and can i use high watt power amplifier to less watts speaker by doing this type of cut in input signal and match power amplifier output watts to the speaker watts?
all these question please answer in simple language so i can understand.

ANSWER: Yes, you are on the right track.  Also, keep in mind that -3db while giving half power does not translate into half sound level perception.  In fact, in order to reduce the sound level to a point that it is perceived by the human listeners to half sound loudness it must be reduced to about -9db.  And 9db is almost equal to 1/10 the power level.  It takes a reduction of about -2db of power to be just barely perceived by humans to detect that a change in acoustic level was made.  This may help you understand the system dynamics better.

If your speakers are properly specified and have power handling correctly and the volume level is set for normal listening levels (which we often call BGM or Background Music) rather than high performance rock concert level system they should handle powers you have outlined very well.

Hoping you have good luck with your design/system performance.

---------- FOLLOW-UP ----------

QUESTION: i also ask about if my power amplifier give 1120 watts at 4 ohms and i connect 600 watts (300+300) at 4 ohms and i keep input signal maximum but just under clip light then is it safe for my speaker or more chances of burn out of speaker? in other way using high output power amplifier without clipping speaker burns?

ANSWER: And I said you are doing fine; you are on the right track.  But, you are making it too scientific.  Music power varies greatly and peak clipping is more a function of controlling the levels than and volume settings than anything else.

Your amp and speakers are fine as you have described them.

Best wishes.

---------- FOLLOW-UP ----------

QUESTION: thanks for your reply.
but still i found difficult to understand it. so reply simply that whether the chances of burning speaker without clip in high watt power amplifier is more or no ? and answer the question in yes or no and with good explanation. thanks

Well, let me review more basics.  Power amplifier measurements are objective in nature; that is they are very precise for loading into a resistive load.

However, speaker specifications and testing is very subjective and a totally inaccurate science.  Speaker burnout can be from excessive average power, from short term high energy burst or power or from high frequencies which tend to blow out tweeters.  The question of proper matching of speaker to amplifier is a guessing game, not a scientific matter.

The main issue to watch is one) making sure the power handling of the speaker is as near as you can guess matches the speaker power being delivered. And two) the impedance loading on the amplifier is correct.

Now, if you are using a voltage line out of the amplifier (25v or 70v) then the tap on the secondary of the matching transformer is set to give the amount of power to that speaker.

The chances of blowing a speaker become higher with improper balance of delivered power from amp to speaker and mismatching of impedance loading of amps to speakers.  Matching a system of the type you are describing is more of a practice and industrial art than an engineering science.

Up to this point you have never revealed the speaker system(s) you are connecting up to the amplifier network.  That would help to know what they are.  

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Audio Design Engineer; systems, loudspeakers, cd/dvd players, etc. I am knowledgeable in all high end audio equipment and installations. MAKE SURE YOU GIVE A MAKE AND MODEL NUMBER AND CAR IF IT IS AN AUTO QUESTION. Note: I am getting some who ask good questions that take a lot of time to research but then the questioner fails to read the answer. Please don't ask questions unless you are seriously looking for an answer. If you find an answer to your question otherwise then let me know with your reply. Thank you.


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