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** Originally posted on 12/27/2010 on our other forums **
After getting several e-mails and calls about Sensitivity of subwoofers and seeing quite a bit of forum action regarding sensitivity I've decided to post this up...
Sensitivity does not = Efficiency on a subwoofer on LOW bass.
Hoffman's Iron Law dictates that out of sensitivity, small box size, and low-end extension you can pick two and the other suffers.
In car audio, especially, you want small box and good low-end so sensitivity will typically be lower than a home audio woofer -- where you can use a large box and then have both high sensitivity and good low-end.
Some recent SA-8 testing results to demonstrate this... measured in Sean's CRX in a box tuned in the mid 30s:
SA-8 / CCAW Coil (83.42 dB 1w/1m) D2 :
Frequency / Power / SPL
25 - 430 - 123.9
30 - 400 - 127.4
35 - 300 - 129.0
40 - 210 - 129.6
45 - 120 - 128.7
50 - 90 - 128.5
SA-8 / Copper Coil Stock (78.6 dB 1w/1m) D2 :
25 - 470 - 125.0
30 - 240 - 131.1
35 - 140 - 132.9
40 - 100 - 132.6
45 - 170 - 130.7
50 - 270 - 129.3
Take note low-bass fans... at 30 Hz the copper driver with nearly 5 dB less sensitivity is using 60% of the power and is 3.7 dB louder.
So... which one is more EFFICIENT on sub-bass by the real definition... output per watt.
The CCAW coil doesn't pull ahead in real efficiency until out of the really low sub-bass region @ 50 Hz.
So... sensitivity should at least pan out in maximum SPL, right ? We put in the SPL box tuned very high and still... not as much effect as you might imagine... the CCAW coil achieved 151.0 dB @ 1310 watts and the copper 149.9 dB @ 1600 watts -- not nearly as much as one would imagine by the 5 dB sensitivity different, huh ?
Even at lower power... both drivers at 250-watts we have 144.9 on the CCAW and 143.3 on the Copper -- just 1.4 dB down at 68 Hz... for a HUGE gain down low.
Is the higher sensitivity driver a better choice for peak SPL ? Yep -- that extra 1.5 dB will win the show... but is it worth a nearly 5 dB loss at 30 Hz (adjusted for power difference the actual loss is about 5dB) for a daily system ? In the minds of most car audio enthusiasts that would be a HUGE "NO SIR!"
-----------------------------------------------
This testing was done in-house for my own purposes of product development and not to simply prove a point... but since the point needs to be made I have decided to share it.
Product design is a balancing act... with an 8" woofer on a standard landing you need a certain amount of stiffness to hold up to what people do to drivers in the real world. On a driver like the SA-8 by the time you get to that level of stiffness a bit of additional mass is needed so we used a copper coil to get there.
Can I soften up the CCAW driver spider a bit and help the low-end ? Sure can -- and we'll be testing that too. The sacrifice is you end up with a less rugged driver that, in terms of VAS, wants a bigger box while at the same time the bigger box further compromises mechanical power handling.
Big balancing act... and we keep doing testing to see if we can improve on the formula of the SA-8 -- so far the combination we have is the most effective for what most people need / want. If we end up improving on it without sacrificing durability then a v.2 SA-8 will be born.
After getting several e-mails and calls about Sensitivity of subwoofers and seeing quite a bit of forum action regarding sensitivity I've decided to post this up...
Sensitivity does not = Efficiency on a subwoofer on LOW bass.
Hoffman's Iron Law dictates that out of sensitivity, small box size, and low-end extension you can pick two and the other suffers.
In car audio, especially, you want small box and good low-end so sensitivity will typically be lower than a home audio woofer -- where you can use a large box and then have both high sensitivity and good low-end.
Some recent SA-8 testing results to demonstrate this... measured in Sean's CRX in a box tuned in the mid 30s:
SA-8 / CCAW Coil (83.42 dB 1w/1m) D2 :
Frequency / Power / SPL
25 - 430 - 123.9
30 - 400 - 127.4
35 - 300 - 129.0
40 - 210 - 129.6
45 - 120 - 128.7
50 - 90 - 128.5
SA-8 / Copper Coil Stock (78.6 dB 1w/1m) D2 :
25 - 470 - 125.0
30 - 240 - 131.1
35 - 140 - 132.9
40 - 100 - 132.6
45 - 170 - 130.7
50 - 270 - 129.3
Take note low-bass fans... at 30 Hz the copper driver with nearly 5 dB less sensitivity is using 60% of the power and is 3.7 dB louder.
So... which one is more EFFICIENT on sub-bass by the real definition... output per watt.
The CCAW coil doesn't pull ahead in real efficiency until out of the really low sub-bass region @ 50 Hz.
So... sensitivity should at least pan out in maximum SPL, right ? We put in the SPL box tuned very high and still... not as much effect as you might imagine... the CCAW coil achieved 151.0 dB @ 1310 watts and the copper 149.9 dB @ 1600 watts -- not nearly as much as one would imagine by the 5 dB sensitivity different, huh ?
Even at lower power... both drivers at 250-watts we have 144.9 on the CCAW and 143.3 on the Copper -- just 1.4 dB down at 68 Hz... for a HUGE gain down low.
Is the higher sensitivity driver a better choice for peak SPL ? Yep -- that extra 1.5 dB will win the show... but is it worth a nearly 5 dB loss at 30 Hz (adjusted for power difference the actual loss is about 5dB) for a daily system ? In the minds of most car audio enthusiasts that would be a HUGE "NO SIR!"
-----------------------------------------------
This testing was done in-house for my own purposes of product development and not to simply prove a point... but since the point needs to be made I have decided to share it.
Product design is a balancing act... with an 8" woofer on a standard landing you need a certain amount of stiffness to hold up to what people do to drivers in the real world. On a driver like the SA-8 by the time you get to that level of stiffness a bit of additional mass is needed so we used a copper coil to get there.
Can I soften up the CCAW driver spider a bit and help the low-end ? Sure can -- and we'll be testing that too. The sacrifice is you end up with a less rugged driver that, in terms of VAS, wants a bigger box while at the same time the bigger box further compromises mechanical power handling.
Big balancing act... and we keep doing testing to see if we can improve on the formula of the SA-8 -- so far the combination we have is the most effective for what most people need / want. If we end up improving on it without sacrificing durability then a v.2 SA-8 will be born.
