Goal is 105 dB peaks @ 4m, 6 dB down @ 30 Hz, anechoic (or better!). Intended layout is per following drawing. Box dimensions and port details/tuning have some play and can be worked out later.
I am still considering AE and Volt speakers, but lack of availability here in India and long lead times (not to mention total cost) are bothersome.
I wonder how much average and peak SPL a duo of ported SB34NRXL75-8 can put out. Sensitivity is 91 dB (2.83V/m), "Rated Power Handling" is 200W per IEC 268-5. I am not able to translate this to Dolby requirements of 85 dB average and 105 dB peaks at monitoring position.
So, con this woofer do it (30 Hz - 300 Hz @ aforementioned SPLs). If not is there another 12" woofer which can be recommended (other than Volt and AE)...
I am still considering AE and Volt speakers, but lack of availability here in India and long lead times (not to mention total cost) are bothersome.
I wonder how much average and peak SPL a duo of ported SB34NRXL75-8 can put out. Sensitivity is 91 dB (2.83V/m), "Rated Power Handling" is 200W per IEC 268-5. I am not able to translate this to Dolby requirements of 85 dB average and 105 dB peaks at monitoring position.
So, con this woofer do it (30 Hz - 300 Hz @ aforementioned SPLs). If not is there another 12" woofer which can be recommended (other than Volt and AE)...
For this woofer, Fs= 22 Hz, Qts=0.28, Qes=0.29, Sd=508 cm^2, Xmax = 10mm 0-pk.
I don't know how big your box is, or what your tuning frequency will be... but you said -6 dB at 30 Hz. I quickly approximated a reasonable box as 60 liter for ONE woofer, tuned to 25 Hz. This will give a -3 dB at 40 Hz, and -6 dB at 30 Hz.
In this box, the single woofer would become displacement limited at 115 dB @ 1M with 273 W input. If we are limited to 200 W per woofer, the result is 113.5 dB @ 1M with 200 W.
With 2 woofers, we gain +3 dB due to twice as much area, and we gain +3 dB because we now have 400 W input (200 W per woofer). So the result is 119.5 dB @ 1 M with 400 W.
Increasing the distance from 1 M to 4 M in a 4-pi environment we loose 12 dB, so the result for 2 woofers, 200 W input each, is 107.5 dB @ 4 M.
If we account for speakers being near a wall, there will be a gain of +3 dB, resulting in 110.5 dB @ 4 M. A true 4-pi environment would require a very large room (theatre or auditorium sized), so this is a more reasonable estimate.
But either way, 4-pi or some room gain, it seems that a pair of these woofers will meet your 105 dB SPL requirement.
I hope someone can check my calculations.... j.
I don't know how big your box is, or what your tuning frequency will be... but you said -6 dB at 30 Hz. I quickly approximated a reasonable box as 60 liter for ONE woofer, tuned to 25 Hz. This will give a -3 dB at 40 Hz, and -6 dB at 30 Hz.
In this box, the single woofer would become displacement limited at 115 dB @ 1M with 273 W input. If we are limited to 200 W per woofer, the result is 113.5 dB @ 1M with 200 W.
With 2 woofers, we gain +3 dB due to twice as much area, and we gain +3 dB because we now have 400 W input (200 W per woofer). So the result is 119.5 dB @ 1 M with 400 W.
Increasing the distance from 1 M to 4 M in a 4-pi environment we loose 12 dB, so the result for 2 woofers, 200 W input each, is 107.5 dB @ 4 M.
If we account for speakers being near a wall, there will be a gain of +3 dB, resulting in 110.5 dB @ 4 M. A true 4-pi environment would require a very large room (theatre or auditorium sized), so this is a more reasonable estimate.
But either way, 4-pi or some room gain, it seems that a pair of these woofers will meet your 105 dB SPL requirement.
I hope someone can check my calculations.... j.
To achieve 105db spl at 4 metres will require a spl of 117db at 1 metre based on this calculator.
I suggest you download VituixCad and use the enclosure tool (it has the SB34NRXL75-8 in its database) to simulate the required power level to achieve 117db spl at 1 metre. I did a quick and dirty simulation with 2 drivers and it looks doable, only just (it's at the limit of max power per driver). It will be a large box at around 140 litres. These calculations are 2pi and without room gain.
I suggest you download VituixCad and use the enclosure tool (it has the SB34NRXL75-8 in its database) to simulate the required power level to achieve 117db spl at 1 metre. I did a quick and dirty simulation with 2 drivers and it looks doable, only just (it's at the limit of max power per driver). It will be a large box at around 140 litres. These calculations are 2pi and without room gain.
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