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Multi-Way Conventional loudspeakers with crossovers

Box design help please
Box design help please
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Old 13th February 2018, 01:03 AM   #1
nzlowie is offline nzlowie  Australia
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Default Box design help please

Hi all

Looking for some input for a new bass section to go with my mid-hf horn. I run the horn from around 500hz up, it uses a BMS coaxial driver. Currently I have the horn sitting on top of my Troels Gravesen DTQWT, these are feed from a class D amp and minidsp for crossover and delay. (Separate amp for the horns)

Iíd like to build new bass cabinets so I can use the DTQWT elsewhere. Heard good things about SB Acoustic drivers, good sound for the price. Emailed them the other day and they recommended the Satori 9.5Ē woofers as these would be a good match for the dynamics of the horns.
I donít have any box design software so would any of you be kind enough to run some numbers for these drivers and give me box volume? (Donít mind big if required)
From what Iíve read closed box gives the best dynamics but not the lowest response, true? As the finished product needs to be as efficient as possible to get closer to the horns I was thinking about using two drivers per channel. One box below the horn and the second above it, using two drivers lifts efficiency by 3db if I read correctly.

Appreciate any thoughts or calculations on this.

Cheers Dave
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Old 13th February 2018, 01:32 AM   #2
Ron E is offline Ron E  United States
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There is no need to have box software, there are literally hundreds of free calculators out there. If you want a box design, the very least you could do is post the parameters, otherwise you are a leech.

If you made it out of high school, figure it out yourself:

Sealed:
Qtc/Qts=Fc/Fs=sqrt(Vas/Vb+1)

Vented:
Vb=20*Vas*Qts^3.3
Fb=0.42*Fs*Qts^-0.96
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Old 13th February 2018, 02:08 AM   #3
nzlowie is offline nzlowie  Australia
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Thanks for your friendly reply....

Tried a couple of online sims and they gave different results thats why I thought I'd ask a friendly forum member.
Not trying to be a leech and I take offence to that, and yes I did make it past high school.
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Old 13th February 2018, 02:18 AM   #4
Ron E is offline Ron E  United States
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Consider that both sims may be correct What makes you think any other will be "more" correct? Compare their results with the "friendly" formulas I gave you... Asking for a sim without providing parameters is being a parasite on this forum whether it offends you or not.
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Armaments, universal debt, and planned obsolescence--those are the three pillars of Western prosperity. óAldous Huxley
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Old 13th February 2018, 02:37 AM   #5
nzlowie is offline nzlowie  Australia
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Quote:
Originally Posted by Ron E View Post
Consider that both sims may be correct What makes you think any other will be "more" correct? Compare their results with the "friendly" formulas I gave you... Asking for a sim without providing parameters is being a parasite on this forum whether it offends you or not.
The first post was to see if these was anyone that was prepared to help, not much point typing all the detail first up if no one is willing to help.
Just have to start the conversation.
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Old 13th February 2018, 04:16 AM   #6
PeteMcK is offline PeteMcK
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Models well in just about any sized box from 40 to 100 L, tuned to 24Hz.... depends how low you want to go
40L gives an F3 of 33Hz, 60L > 27Hz; 80L >23Hz; 100L 22Hz.....
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency

Last edited by PeteMcK; 13th February 2018 at 04:19 AM.
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Old 13th February 2018, 05:02 AM   #7
nzlowie is offline nzlowie  Australia
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Quote:
Originally Posted by PeteMcK View Post
Models well in just about any sized box from 40 to 100 L, tuned to 24Hz.... depends how low you want to go
40L gives an F3 of 33Hz, 60L > 27Hz; 80L >23Hz; 100L 22Hz.....
Thanks Pete

Is the size of the box the only compromise or does the size impact on the performance as a whole? Given the volume is tuned right of cause.

So all I really need to do is select the volume that will work for me then size the port to match? Or not that simple?

Also am I correct in thinking that if I build two of these enclosures and stack them I'll get a 3db output increase?

Do you think I'm asking too much to use the one driver to cover 30hz to 500hz?

Once again thanks for your help.

Last edited by nzlowie; 13th February 2018 at 05:17 AM.
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Old 13th February 2018, 05:19 AM   #8
PeteMcK is offline PeteMcK
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"So all I really need to do is select the volume that will work for me" - yes
"if I build two of these enclosures and stack them I'll get a 3db output increase?" - 6dB, 3dB from doubling the piston area, 3dB from halving the load to the amp (unless you put them in series - in which case no increase)
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Impedance varies with frequency, use impedance plots of your drivers and make crossover calculations using the actual impedance of the driver at the crossover frequency
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Old 13th February 2018, 07:46 AM   #9
nzlowie is offline nzlowie  Australia
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Thanks guys, appreciated.
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