need commens on SPL dynamics ?

[odysse]

i have four of these ( spl car drivers ) at home ,
And interested in the views and how it looks in theory, i think they sound good but they need much power ( my current old lab amps feels way to small ) ,
Now in retrospect, I wonder if I would build them a little bigger and tuned them a bit lower ?
The boxes are mirrored so I can put them in the corners with the ports point to each other, how are the thoughts about it?

the effective volyme is about 77 L and they tuned to 38 hz ,

XTR-380D2
Power handling (RMS/Peak) 1000/2000 W
Nominal impedance 2 x 2 Ohm
Magnet weight 200 oz
Voice Coil diameter 76 mm ( 3 " )
Fs 32.5 Hz
Vas 60.6 L
Qts 0.467
Qes 0.534
Qms 3.755
Xmax (lin/peak) 13/26 mm
Re 3.8 Ohm
Mms 360 g
BL 23.26 TM
SPL (1W/1m) 88.3 dB

 

[Circlomanen]

You should build a pair of offset driver quarter wave pipes instead of the "kräkreflex" boxes you currently use.

http://oi68.tinypic.com/2m5kxti.jpg

A friend of my son has two large offset driver quarter wave pipes with Beyma 15K200, and they are very impressive and fun.





There is a thread about them in the Swedish forum Hififorum.nu:
HiFiForum.nu - Klart grabbarna skall ha bas!!

Cheers,
Johannes

 

[GM]

Now in retrospect, I wonder if I would build them a little bigger and tuned them a bit lower ?
The boxes are mirrored so I can put them in the corners with the ports point to each other, how are the thoughts about it?

Quite a bit bigger actually, assuming the published specs are reasonably accurate, though often not likely.

An easy '1st approximation' guide is that for a max flat alignment [Fb = F3] is when Fb = Fs, Vb = Vas, Qts' = ~0.403; with smaller cabs tuned higher with lower Qts', ergo larger cabs tuned lower for higher Qts' and when specs are off, Qts is invariably higher, so may either need some really large cabs tuned really low and/or make them sealed and in either case, damp to 'taste'.

Qts' = Qts + any added series resistance: mh-audio.nl - Home

From this we see that even just using published Qts, the cab needs to be > 60.6 L net/driver, tuned < 32.5 Hz and if corner loaded, then maybe lower still or even sealed since you're running essentially a 20-21" driver/corner.

The WLs coming out of the ports are so large it's a moot point as to whether they fire forward or to the side, though keeping them near the wall/floor boundaries does help a little.

Anyway, plug the numbers into a calculator and if you want to be reasonably sure the cab will be near enough optimal for corner loading, increase Qts = 0.707 and it is what it is size, tuning wise.

GM

 

[GM]

You should build a pair of offset driver quarter wave pipes......

Considering the peaking at Fb, what's the highest usable Qts' before tuning 'collapses' to Fp = Fs/Qts' like with regular [T] TLs?

GM