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[Josh Sadler]

I am building two dual 18 reflex cabs for Peavey's Lowrider 18.
Each cab will be powered with a QSC PLX3402 (bridged 4 ohm)
I am using bass box pro for cab design so far.
I am looking for a nice flat response, but cant seem to find it without huge volume.
I think I would like to aim for Vb=13.5 cu ft or below.

Could someone maybe shed some light?

Speaker specs are...

Znom (ohms) 8
Revc (ohms) 6.21
Sd (Square Meters) 0.134
BL (T/M) 22.17
Fo (Hz) 28.9
Vas (liters) 288.0
Cms (uM/N) 113.3
Mms (gm) 198.20
Qms 9.07
Qes 0.451
Qts 0.429
Xmax (mm) 9.6
Le (mH) 0.87
SPL (1 W 1m) 96.0
no (%) 2.65
Vd (cubic inches/milliliters) 145 / 2375
Pmax (Watts pgm.) 1600
Disp (inches/milliliters) 235 / 3852

Also, some of these specs copied from the spec sheet dont add up?
Sd x Xmax does not equal Vd from their spec sheet.  It's almost double!
Also, Qes,Qms, Qts, BL are off slightly

Also, peavey recommends 6 cuft/driver tuned at 34 hz, but if you input their recommened port size and length, it doesnt add up either?

[Paul G. OBrien]

Also, some of these specs copied from the spec sheet dont add up?
Sd x Xmax does not equal Vd from their spec sheet.  It's almost double!

That's because Xmax is just the peak movement in one direction so Vd = 2*Xmax*Sd.

Also, Qes,Qms, Qts, BL are off slightly

Yeah that's common, don't worry about it and let the software pick the correct numbers.

Also, peavey recommends 6 cuft/driver tuned at 34 hz, but if you input their recommened port size and length, it doesnt add up either?

It does if you add the volume displaced by the driver and ports to bring the actual box volume to about 7.3cu/ft per driver.

[Josh Sadler]

That's because Xmax is just the peak movement in one direction so Vd = 2*Xmax*Sd.

If Im not mistaken, Vd = Xmax*Sd.  This is also how Bass Box Pro calculates it.  Check Thiele/Small on wiki.

Peavey may be trying to "boost" their figures, by multiplying Xmax peak-to-peak with Sd, which is not Vd
 2*Xmax = Xmax peak-to-peak

But again, I could be wrong.

Yeah that's common, don't worry about it and let the software pick the correct numbers.

I can understand some being off slightly, but some of these are way out there when plugging into formulas (and double checking units, of course)

 

It does if you add the volume displaced by the driver and ports to bring the actual box volume to about 7.3cu/ft per driver.

I already understood speaker and port displacement. Where I was messing up was only entering 2x 6" ports instead of 4x (since my box is double)

[Paul G. OBrien]

If Im not mistaken, Vd = Xmax*Sd.  This is also how Bass Box Pro calculates it.  Check Thiele/Small on wiki.

Peavey may be trying to "boost" their figures, by multiplying Xmax peak-to-peak with Sd, which is not Vd  2*Xmax = Xmax peak-to-peak

Yeah they state as much in the specs notes for Vd.. that they consider it to be a pk-pk measurement. Gotta read the fine print..

In any event you should be quite happy with boxes designed around this "medium" sized peavey spec, these drivers are really good performers for the $$ and will take full rated power in these boxes.. with appropriate low cut filters in place of course... ~30hz 4th order.

[Josh Sadler]

In any event you should be quite happy with boxes designed around this "medium" sized peavey spec, these drivers are really good performers for the $$ and will take full rated power in these boxes.. with appropriate low cut filters in place of course... ~30hz 4th order.

When I put in the Vb=13.5 and Fb=34 Hz and size my ports accordingly,
The drivers are overexcurion when I input 3200W by about 1.5 mm in the 50-60Hz range.  Looks like if I build the "medium" box and have it hooked up to my PLX3402 , I will have to limit that frequency range slightly in order to keep it from being slightly distorted.  Or will I even notice theis 1.5 mm overexcursion in sound quality?

I may end up going to go with a box that is in between the small and large enclosures. Say 11.5 cu ft tuned at 36.5 Hz

[Paul G. OBrien]

When I put in the Vb=13.5 and Fb=34 Hz and size my ports accordingly,
The drivers are overexcurion when I input 3200W by about 1.5 mm in the 50-60Hz range.  Looks like if I build the "medium" box and have it hooked up to my PLX3402 , I will have to limit that frequency range slightly in order to keep it from being slightly distorted.  Or will I even notice theis 1.5 mm overexcursion in sound quality?

Getting 3200w from those amps for anything more than a kick drum hit will be difficult.. very stable 20a AC circuits are required, and at the sound levels level you're talking about here you won't hear the relatively small increase in distortion caused by slightly exceeding xmax.

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