Impedance and SPL..

TroelsM · 26th September 2005, 11:56 AM

Hi.

If a 8ohm speaker has an sens. of 93 dB (1W/1m) and a 4 ohm speaker has a sens. of 93 dB (1W/1m) will they make the same SPL if they are connected in parrallel to the same amp?

As I recall it the def of loudspeaker-sens. was something like the measured dB's with 1V across the terminals? - And that can´t lead to the same sensitivity as the W/m def.

Hope this makes any sense to you.

TroelsM

richie00boy · 26th September 2005, 12:06 PM

No they won't make the same SPL because the 4 ohm speaker will be drawing twice the current hence 4x the power, so 6dB louder.

What might trip things up is that a lot of manufacturers of 4 ohm speakers inflate their sensitivity levels by using the same 2.83V (which is 1 watt into 8 ohm) to drive their speaker. In that case then they should put out the same SPL.

TroelsM · 26th September 2005, 12:18 PM

Hi richie00boy.

I must admit that I dont get your point.

If a 4ohm speaker draws twice the current according to ohm's law then the power will be 2* not 4*!

Any Idea how Monacor does the sens-meas.?

TroelsM

soongsc · 26th September 2005, 12:37 PM

Quote:

Originally posted by TroelsM
Hi richie00boy.

I must admit that I dont get your point.

If a 4ohm speaker draws twice the current according to ohm's law then the power will be 2* not 4*!

Any Idea how Monacor does the sens-meas.?

TroelsM

Taken the amp volume is the same, thus for P=I*V, V is the same, with a doubled I you get twice the power.

soongsc · 26th September 2005, 12:43 PM

Quote:

Originally posted by TroelsM
Hi.

If a 8ohm speaker has an sens. of 93 dB (1W/1m) and a 4 ohm speaker has a sens. of 93 dB (1W/1m) will they make the same SPL if they are connected in parrallel to the same amp?

As I recall it the def of loudspeaker-sens. was something like the measured dB's with 1V across the terminals? - And that can´t lead to the same sensitivity as the W/m def.

Hope this makes any sense to you.

TroelsM

(1W/1m) is precisely what it means. Not the 1V as you think it is. For 8 ohm load, something like 2.83V is used, for 4 Ohm, something like 2V is used.

richie00boy · 26th September 2005, 12:52 PM

You're right, double the power. It's been a long weekend and too many I^2 x R calculations lately

26th September 2005, 11:56 AM	#1
TroelsM diyAudio Member Join Date: May 2003 Location: AARHUS. DK	Impedance and SPL.. Hi. If a 8ohm speaker has an sens. of 93 dB (1W/1m) and a 4 ohm speaker has a sens. of 93 dB (1W/1m) will they make the same SPL if they are connected in parrallel to the same amp? As I recall it the def of loudspeaker-sens. was something like the measured dB's with 1V across the terminals? - And that can´t lead to the same sensitivity as the W/m def. Hope this makes any sense to you. TroelsM

26th September 2005, 12:06 PM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	No they won't make the same SPL because the 4 ohm speaker will be drawing twice the current hence 4x the power, so 6dB louder. What might trip things up is that a lot of manufacturers of 4 ohm speakers inflate their sensitivity levels by using the same 2.83V (which is 1 watt into 8 ohm) to drive their speaker. In that case then they should put out the same SPL. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

26th September 2005, 12:52 PM	#6
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	You're right, double the power. It's been a long weekend and too many I^2 x R calculations lately __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

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26th September 2005, 12:18 PM	#3
TroelsM diyAudio Member Join Date: May 2003 Location: AARHUS. DK	Hi richie00boy. I must admit that I dont get your point. If a 4ohm speaker draws twice the current according to ohm's law then the power will be 2* not 4*! Any Idea how Monacor does the sens-meas.? TroelsM

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