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Multi-Way Conventional loudspeakers with crossovers

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Old 7th August 2007, 12:15 PM   #1
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Join Date: Mar 2004
Location: Albury NSW Australia
Default SPL Matching

Hi
I have some 12 inch wooofers i want to use in a 3 way system which have an SPL of 93db.
I want to match the 93db output in the mids i plan to use and they have an efficiency of 88db. Since the mid in question only comes in an 8ohm spec, i would need to wire up 4 of these in a series parallel configuration to keep impedance near 8 Ohm. NOw depending on what i have read i get a 3db increase for 2 mids so with 4 would the output be 94db?
Its probably a dumb question but i need clarification
Thanks
Nick
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Old 7th August 2007, 01:19 PM   #2
AndrewT is offline AndrewT  Scotland
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Join Date: Jul 2004
Location: Scottish Borders
Hi,
just put 5db less power into the bass drivers.

Fit a sensitivity control with more than 5db attenuation range. Set up the bass to match the mid and treble ranges.

100W into your mid will give maxSPL of about 108db =~103db at your seat.

32W into your bass will give maxSPL of about 108db =~103db at your seat.

Allow an average to peak range of 20db and your maximum listening volume for both speakers will be about 83db.

Double up the speakers (at the same total power) gives an extra 3db IF the drivers are close together.
Double the power into the pairs of drivers and you get another 3db of SPL.

Double mid and double bass give the potential of 89db at your seat. That is LOUD and still only 64W of bass power.
It is odd that so many tell you to increase the power into the bass drivers?

What I have conveniently overlooked is that an efficient bass driver cannot get really low into the bass. It will be very good and ideal for music reproduction where almost everything is 40Hz and above. If you want 20Hz for film sound effects and the few audio tracks with weirdly low frequencies, then all the above goes out the window with the 12inchers that will struggle down there, unless designed specifically for low frequency use and of necessity lower efficiency.
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Old 7th August 2007, 05:26 PM   #3
sreten is offline sreten  United Kingdom
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Join Date: Nov 2003
Location: Brighton UK
Default Re: SPL Matching

Quote:
Originally posted by duderduderini
Hi
I have some 12 inch wooofers i want to use in a 3 way system which have an SPL of 93db.
I want to match the 93db output in the mids i plan to use and they have an efficiency of 88db. Since the mid in question only comes in an 8ohm spec, i would need to wire up 4 of these in a series parallel configuration to keep impedance near 8 Ohm. NOw depending on what i have read i get a 3db increase for 2 mids so with 4 would the output be 94db?
Its probably a dumb question but i need clarification
Thanks
Nick

Hi,

read up on baffle step compensation and check where your woofers
sensitivity is measured, for bass design it might be lower. As it stands
the bass unit will be fine with the mid unit including 5dB of BSC, if
the 12" is a little lower real sensitivity in the bass you will get lower
amounts of BSC. You not need multiple mid units.

:0/sreten.
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