12" J-bin....

[Empee]

Hi !


I know there's been some talking about this but I
cannot seem to find any workable conclusions...

So my question is;
Can a J-bin / Scoop as used in PA, be made with a 12" driver ?

Off coarse it can, but will it work ?

Now I'm posting this in the Fullrange-forum, as I intend to make
a hifi-sorta scoop using the ol' Philips AD12202.
A terrific fullrange 12" although I'm a little worried of the high-ish
total Q (being somewhere in the range of 1.2 I guess)

My thoughts are as follows;
If I were to scale down the original J-bin, I'd alter the hornlength,
pushing the lower horn cut off frequency up.
But isn't it smarter to just narrow the design,
so keeping the hornlength the same ?

And if this is a way to go, how much would it be narrower ?


Maybe some of you backloaded-horn-masters can help me with
this please ?


Cheers,

Empee

[GM]

As Qts increases, so goes the filter chamber (Vr) and throat area (St), changing the horn profile, ergo horn size increases.

GM

[Empee]

hi GM,

That's usefull information!
So I get to learn something on a sundaynight :-)

But is a Qts of 1.2 any good for hornloading ?

what be your cabinet of choice for these 12" Philips drivers ?


Cheers,

Empee

[GM]

Greets!

Well, it would depend on the rest of the driver specs and what the performance goals are, but as a general rule a ~0.707 Qts is the upper limit.

If the Qts is this high, then either OB or a max flat impedance TL, but the latter requires specs to calculate it.

GM

[Empee]

Hi!

found in another thread:

Originally posted by edlye
I just found a spec sheet, but it is in German: http://www.rahaso.de/foren/msg.php?f...nge&idx=18657&

Here's a translation with the help of babel fish:

nominal impedance 8ohms
d.c. resistance of the moving coil 6.6ohms
load rating 100W
max load 150W
output 0.5W
resonant frequency 45Hz
through howling tension (lost in translation?) 9V
transmission range 50Hz - 19kHz
magnet material FXD
magnet diameter 124.6mm
magnet mass 990g
energy in the air gap 498mWs
magn. flow density 1110mT
air gap height 8mm
height of the moving coil 9.7mm
minor diameter 35mm
basket diameter 313.3mm
sound opening/free space 278/5mm
depth 135mm
mass of the loudspeaker 1650g

Unfortunatly, no Qts....

Can it be derived from other numbers ?


Cheers,

Empee

[GM]

No, it's like figuring out how fast your car will do 0-60 from how much your motor weighs and the size of the transmission's gears. We did learn Fs = 45 Hz, Re = 6.6 ohms and a minuscule 0.85 mm Xmax though.

GM

[Empee]

Hi !

hmmm, ok, I get your point

Seems there is no alternative then to try to measure Qts myself
Do you have any methods you'd like to recommend ?

I got some more speakers I'd like to measure so it would make
a nice session. Next weekend I'll have the time to do this...

By the way;
the "recomended enclosure" by Philips is "bassreflex or hornloading",
so I guess Qts isn't that high afterall...


Cheers,

Empee

[Scottmoose]

http://sound.westhost.com/tsp.htm

[Empee]

I got all specs' !

Qts is 0,8, wich is a wee bit too high for hornloading...

Would a BVR (yet another son of Chang) be a good way to go ?


Cheers,

Empee

[rcavictim]

Originally posted by Empee
I got all specs' !

Qts is 0,8, wich is a wee bit too high for hornloading...

Would a BVR (yet another son of Chang) be a good way to go ?


Cheers,

Empee

That chart is unreadable.