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Old 28th November 2011, 11:40 AM   #1
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Default High efficiency speakers - how much power do they really need?

Hi,

I am now listening to an 8" SEAS fullranger with a sensitivity of 94dB per watt. The volume control of my tube amp is about a notch above the minimum volume.

Did a bit of reading up, it seems that 85dB or so if prolonged exposure could result in hearing loss, and vacuum cleaners are 70dB or so. At which point I am wondering how much power am I sticking into them?

By these definition, at 0.1W, I should be risking hearing loss... which is possible, looking at how low the volume control is turned down.

Makes me wonder, if one were to design an amp for such a speaker, would 1 watt have been enough?

Oon
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Old 28th November 2011, 12:00 PM   #2
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Unless you're using it for headphones I shouldn't worry, intensity drops off fairly quickly over distance. The inverse distance law 1/r for the sound pressure - no square - acoustic audio sound reduction free field particle amplitude volume loudness level distance laws dB decibel calculator distance dropratio- sengpielaudio Sengpiel Berlin

One watt may be giving you reasonable listening levels, but you always want as big an amp as possible-the ideal amp would have limitless power: Dynamic range is what makes music feel real. The wider the dynamic range the louder the loud bits are and quieter the quiet bits are, making the experience more visceral.
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Old 28th November 2011, 12:05 PM   #3
hm is offline hm  Europe
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Hello,
i need for my horns only less than 1 Watt, so
if you get a 3 Watt digital amp or tube amp it would be enough.
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Old 28th November 2011, 12:39 PM   #4
AndrewT is online now AndrewT  Scotland
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Oon,
have you measured the signal voltage at your speakers?
Use that to estimate the power the speakers are receiving.
Allow at least 100times your normal listening power to allow short term transients to pass through unclipped. That's the upper half of the dynamic range referred to in post2.

BTW, using 1W and 94dB/W @ 1m ends up with a maximum SPL at a 2.5m listening position of just 89dB from a pair of 1W amplifiers/speakers.

For good reproduction of dynamics one would normally expect transient peaks of 105dB at your listening position. 110dB would be excellent and some builders/listeners demand even more.
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Last edited by AndrewT; 28th November 2011 at 12:44 PM.
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Old 28th November 2011, 10:15 PM   #5
Bigun is offline Bigun  Canada
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Quote:
Originally Posted by oon_the_kid View Post
Makes me wonder, if one were to design an amp for such a speaker, would 1 watt have been enough?
With the right amp, I'd say 2W or so would be enough depending on the type of music you like. I don't buy the 'you need a gazillian watts for the transients' stuff myself, but maybe I just don't listen to the kind of music where this is important. The advantage of flea powered amps is usually that they enjoy different design tradeoffs that can make them very enjoyable to listen to - i.e. DHTs.
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Old 29th November 2011, 12:44 AM   #6
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Hi,

Thanks for all the replys....

Dear AndrewT,

While it is true that sound level falls off at inverse square, this won't be true in a room (non anechoic chamber) since there is reflection from the walls. I think it really depends on the size of the room and how much carpeting I have....

I suppose, my interest in this is I want to try out class A. Since efficiency is something like 10W DC in, 1 W power out, I would want to keep it as small as possible...

Maybe just build a class A of 1 or 2 W only...

Oon
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Old 29th November 2011, 01:02 AM   #7
Pano is offline Pano  United States
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If you can measure low AC voltages, that would be a great guide as Andrew suggests.
For example: With my system (not single driver) I get 85dB at the listening seat when both speakers are fed 1V RMS. That's 1/8th Watt. I need very little power to hit 110dB peaks. And 85dB average is pretty loud.

If you have a way to measure the voltage at your speakers, you can figure out how much power you need. I'll bet 5W RMS will be plenty.
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Old 29th November 2011, 03:02 AM   #8
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Hi Pano,

I figure I will also be using about that. I can always measure with a multimeter, just don't have a sine wave generator. But i suspect 1V is going to be plenty for me, and 1/10W is closer to what I need....

BTW, just out of curiosity, how are efficient are your speakers? 90+dB/watt

Oon
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Old 29th November 2011, 03:23 AM   #9
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by oon_the_kid View Post
Hi,

Thanks for all the replys....

Dear AndrewT,

While it is true that sound level falls off at inverse square, this won't be true in a room (non anechoic chamber) since there is reflection from the walls. I think it really depends on the size of the room and how much carpeting I have....

I suppose, my interest in this is I want to try out class A. Since efficiency is something like 10W DC in, 1 W power out, I would want to keep it as small as possible...

Maybe just build a class A of 1 or 2 W only...

Oon
I would go for at least 40 watts ....

Quote:
Originally Posted by Pano View Post
If you can measure low AC voltages, that would be a great guide as Andrew suggests.
For example: With my system (not single driver) I get 85dB at the listening seat when both speakers are fed 1V RMS. That's 1/8th Watt. I need very little power to hit 110dB peaks. And 85dB average is pretty loud.

If you have a way to measure the voltage at your speakers, you can figure out how much power you need. I'll bet 5W RMS will be plenty.
1v, That must be 85db narrow band .......
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Old 29th November 2011, 04:44 AM   #10
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Your 94 Db for the SEAS driver is just touching the lower band of the truly high efficient arena.......Ever wonder why garage bands seem so very loud?........and they are using 30 Watt or so guitar heads, times..three? Guitar drivers are around the 100 Db range......PA style Large format Horns are running around 108Db.
I recall long ago as a teenager, running a cassette (Walkman, early) thru a set of old tube era loudspeakers...of high efficiency(102 Db+)?? A casual listener who happened by was stymied by the lack of tuner, receiver......or SOMETHING that was the source for the loudspeakers....only when I picked up the cassette player off the top of the cabinet & flicked it off, did they know.
150 mW worth of power was enough for those drivers.

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