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Old 23rd May 2003, 06:54 PM   #11
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If memory serves, the speaker efficiency with regards power transfer is a major factor. If you put out, or measure, 1 watt with a watt meter, or the non-inductive load, it may not be the same at the speaker.

I mean, you can have a speaker that is designed to handle 10 watts (1 inch voice coil, 5 ounce magnet) be 90dB/watt, and a speaker designed for 500 watts (2.5 inch coil, 10 pound magnet) be 90dB per watt. Will the 1 watt amp drive them to the same actual dB? Nope. That is because there is power loss in the bigger power speaker.

So, the rating really means that if you have enough power that the speaker processes 1 watt, you will get 90 dB. The 500 watt speaker may need 50-100 watts of amplifier power to give you close to 90dB.

In my opinion, if memory serves. Haven't read about this in 15 years. Could be starting another war!

Gabe
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Old 23rd May 2003, 07:08 PM   #12
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Default RE:Could be starting another war!

Hi,

Gabe, I don't think that's correct.

Speaker effeciency as stated by the manufacturer is, or shall we say should, be the same regardless of its size or powerhandling.

Actually the poweroutput capabilty of an amp should be calculated by using a resistance of say 8,4 or 16 Ohm to get the rating.
You can measure it with a speaker connected but that will only tell you how much the amp is delivering with that particular load.

I don't know the formula by heart but I'm sure it's derived from Ohm's law.

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Old 23rd May 2003, 10:05 PM   #13
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Default OHM.

Hi,

Tada....

P = I ^2 *R.

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Old 24th May 2003, 02:59 AM   #14
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Quote:
Originally posted by Gabevee
My

The 500 watt speaker may need 50-100 watts of amplifier power to give you close to 90dB.


I don't think anyone will be lining up to buy that driver. Don't know if this applies or not but the formula for wattage to db is: W=logx10. This is added to your 1 watt spl rating for db output at any given wattage. The formula for power is: power=logx20.
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Old 24th May 2003, 03:29 AM   #15
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Quote:
Originally posted by Gabevee
So, the rating really means that if you have enough power that the speaker processes 1 watt, you will get 90 dB. The 500 watt speaker may need 50-100 watts of amplifier power to give you close to 90dB.
That's incorrect. Read Theile and Small.
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Old 26th May 2003, 08:26 AM   #16
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OK, OK already, I did say if memory serves, doggoneit!

I also did a few searches on the web, and one place did say something similar to what I said. However, what the person said was that one has to look at the overall efficiency (I forgot the exact term). Remember that generally the speaker is tested for that SPL at 1kHz. It may not be 90 dB at other frequenies.

Now, I am sure we all know this.

Thanks for the correction. As I said, I read about this stuff 15 years or so ago, when I built my first pair of speakers,which BTW I still listen to. I haven't thought much about speakers since, except for the crossover networks, which I readily build and put into speakers I buy, improving their quality.

So... ignore what I said!

OTOH, one must not think that either one watt is enough or that 2 watts will give one 180 dB. Doubling the power only gives a 3dB boost, hardly loud enough to detect. Perceptible doubling required 10dB, if memory serves (Uh, oh, I am in trouble again! ).

Later!
Gabe
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