# CSS-SDX15: 300l/15Hz or 400l/15Hz - please advice



## daxie (Nov 29, 2006)

Hello all,

I will be building an SLLT based on a CSS-SDX15 driver. (actually, I will be building two).

What would you prefer?

a) 300l volume, tuned @ 15Hz with a 16cm dia port of 77,40cm (FPR 222Hz) length (yellow)
b) 400l volume, tuned @ 15Hz with a 20cm dia port of 89,80cm (FPR 191Hz) length (grey)

(port diameters chosen because of available PVC-tube diameters)

(Both graphs are with 800W as input, a thomann tamp ta2400 will be driving them).

Option a has better group delay, better first port resonance, lower cone excursion, but the port air velocity is a bit high (is it?). The SPL I'm trading in is not needed. Option b has a good but slightly less good group delay (although equal until 18Hz), better air port velocity (under that 30m/s limit), but a first port resonance that is a bit on the border side...

My preference would go out to option a, but I'm worried about the port velocity? Is it an issue?

The room is 1400 cu ft (40 cubic metres) large. Do keep in mind that I will have two of these puppies there, so probably I won't be pushing them nearly as far as I'm modelling here. (Which adds to my preference of option a, since air velocity will be a lot lower when not pushing them to the max).

The winisd simulations:










































Thank you,


Wouter


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## Ilkka (Jun 8, 2006)

Definitely 300L with 15 Hz tuning. Port velocity isn't going to be problem with real world signals. Simulations always assume sine waves which few of us play regularly. :R

When you are building two of those monsters, you won't be hearing any port noise at sane (or not so sane) output levels - I guarantee it.


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## daxie (Nov 29, 2006)

that's clear, thank you


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