# Good high sensitivity speakers?



## alanranch (Feb 5, 2006)

Hi guys I own a panasonic tube head unit and would like to just hook up speakers straight to my head unit. What are the best sq high sensitivy speakers out there? Ill be going to Japan next week and would scout around for a replacement for my morel elate/seas ref combo speakers. I cant seem to find good high sensitive speakers. Would really appreciate your inputs. Thanks


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## invecs (Jul 30, 2005)

Hi Alan,

I'd suggest looking into Focal Access 6.5 or the Polyglass 165v1...those were designed to run well with the hu builtin amp. They might not be the best, but I think they would compliment your tubehead very well.


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## rush1 (Nov 18, 2007)

Hi Alan,

I have the same head unit mate. I would try the Focal 165 K2P. I once tried it with all tube amplifier, Milbert BaM235 (30watt/channel) and it sounded good.

Cheers,


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## Abmolech (Nov 2, 2006)

You should "bone up" on how senstivity ratings are derived before you decide on a particular driver.

Hint
The specifications are misleading, to the point where most are useless unless you can transfer them the same standard.

The sensitivity of a driver is the medium sound pressure between 125 Hz (or 250 Hz) to 4 kHz (or 8 kHz) when you have a constant voltage at a specific distance; measured in dB per watt and meter. The most common is the voltage of constant 2.83 volts and the distance is 1 meter at 8 ohms nominal impedance. For instance the sensitivity of a good 8 ohms driver could be 93 dB / 2.83 volts / 1 meter
Therefore power 
P = V^ 2 / R 
= 2.832 / 8
= 1 watt
With a 4 ohms loudspeaker you would generate 2 watts. 
P = V ^2 / R 
= 2.832 / 4
= 2 watts
Therefore to calculate the reference value of 1 watt, you have to subtract from the sensitivity 3 dB.
If the driver of 8 ohms nominal impedance has the same sensitivity rating as a 4 ohm driver (2.83 volts at 1 metre) then, the 8 ohm driver will produce 3 dB higher sound pressure level at the same watt. However you normally don't acquire this advantage because most power amplifiers produce half wattage (3 dB) less at 8 ohms compared to 4 ohms impedance.
In driver data you never find the efficiency in percent, but usually there is the sensitivity in dB/W/m. It is not the efficiency you get here, it is the sensitivity.
The very small value of the efficiency is never shown by a manufacturer. Usual values for home speakers and studio monitors are between 0.2 % and maximum 2 % - that is an efficiency of 0.002 to 0.02.
Efficiency is not the same as sensitivity, but it is possible to convert efficiency to sensitivity.
Sensitivity in dB = 112 + 10 log (efficiency)
Efficiency = 10^(Sensitivity in dB - 112)/10
The 112 dB is the 0 dB reference level, and for sound is 10^-12 watts.
1 acoustical watt therefore = 120 dB sound pressure level.

The standard measurement for loudspeakers is done with an infinite baffle sounding in a half room with a distance of radius = 1metre.
The resultant factor 2 π × r^2 (area of a half sphere or 2 π staradians, IE the area of a full sphere =4 π × r^2 = 4 π staradians) which therefore equals -8 dB. We can then calculate for an efficiency of 1 (full sphere) = 100 % a sensitivity of 120 - 8 = 112 dB. 
This calculation works correct if the loudspeaker radiates in a half circle 2 π staradians. Otherwise you must add the Q factor because of directionality.
There is no connection between the efficiency and the sound quality.


Example Calculate the maximum sound pressure level of a loudspeaker at 1 m distance, when the sensitivity level of 98 dB /1watt /1metre, and the wattage is 300 watts.

At 1 Watt you get 98 dBsound pressure level in 1 m distance. At 300 W there is 10 × log 300/1 = 24.77 dB more level, that means 122.77 dB sound pressure level.

Clue
The sensitivity rating on a sub woofer is farcical because the rating is between 125 Hz and 4 KHz. 

Welcome to the world of audio.


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## CMR22 (Feb 10, 2007)

Abmolech said:


> Clue
> The sensitivity rating on a sub woofer is farcical because the rating is between 125 Hz and 4 KHz.
> 
> Welcome to the world of audio.


What if the manufacturer states the rating is between 50hz and 100hz?

http://www.imagedynamicsusa.com/pdf/IDQ15%20D2%20V2.pdf


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## Abmolech (Nov 2, 2006)

94.2 dB sensitivity frequency range 50 -100 Hz.

At what voltage?
At what distance?
Do you think that this driver is better than normal tweeter sensitivity?

Note the nominal impedance is rated at 1 -4 ohms.

Let us ASSUME it is rated at 2.83 volts at one metre.


Therefore this is at 8 watts?

IE 2.83^2 =8 /1(?) = 8 watts.

Which possibly requires an 9 dB correction to get 1 watt @ 1 metre.
Therefore the sub is 85.2 dB @ 1 watt @ 1 metre?
This is quite clearly rated on some assumptions (4 π steradians), but this sounds like a more plausible rating.

It would be "interesting" to have the rating at 20 -80 Hz, which is considered by SPL competitions to be the sub woofer frequencies. I would expect to have in the high 70 dB @ 1 watt @ 1 meter as a more "genuine" figure if I was trying to calculate the required wattage for a power amplifier.


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## Steak (Mar 16, 2006)

(bump)

So if a 4 ohm woofer is rated at 94.7 dB W/m, would it be correct to assume that its sensitivity rating (for comparison to other woofers) would be 3 dB more, ie. 97.7 dB 2.83V/m ??


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