Thats Mark Gander. He created the Cabaret series which kinda set JBL on its path to being as big as it is in pro / tour/ live sound
Thats Mark Gander. He created the Cabaret series which kinda set JBL on its path to being as big as it is in pro / tour/ live sound
Hi macaroonie,
Just to be MORE PRECISE: BMS 4590/92 has TWO annular diaphragms too,
but with different purpose:
one larger for mid section ( 3.5-inch vice coil), and
one smaller (1.75-inch) annular (NOT DOME type) for high section,
as can be seen on the attached figures.
They are working 'independently' with their 'own' phase plugs, but with 'common' short horn, while JBL D2 diaphragms are intended to be used to work 'together' (compound).....
But for either of the drivers it would be very difficult to construct the horn the would satisfy the dispersion for such large frequency range (say from about 1kHz to 20kHz), without introducing some kind of diffraction slots. So, it would be very interesting to see some 'independent' listening tests of JBL new horn (M2 monitor) connected to the D2 drivers. I will not be surprised, if over 12kH, that the dispersion of M2 would not be over 30 degs
Best Regards
Ivica.
The cabs were initially designed for a 12" Kef B300 at 80 litres capacity (2.8cft). Then I adapted the cab for a JBL 15" driver. I needed more area to fit the driver, as well as more volume. The extension allowed both. I initially tried the (now) 95 litre cabinet (3,4cft) with a 2235h. Sadly, the 2235 needed more volume. At least 50% more to feel at ease. Then I went with 2225s and it was better but the ideal volume of 75l was exceeded and the woofer felt too soft, not enough lively, not to mention it is not a bass reflex driver. Not there yet. I did some testing with a driver that I thought I hated : the 2226. But thinking about it, it was specifically designed for a small bass reflex enclosure with its higher Qts and lower Vas. Doing some modeling and using the Vab = 5.7 * Vas * Qts^2 = 94litre formula, I realized the match was perfect. I tuned the reflex port to 47Hz and am now quite delighted. Bass goes deep enough, yet it is tight on top. I slightly tamed the midrange though. The simple two-way system sounds very good and works on all kind of musics. I will add a 12cft 2245 sub and shall be done with it. Is the 2226 perfect? Not. It needs some processing, but it can take a lot of it.
That "forward cabin" design is something I may have seen in Europe in the mid 1970s. I always digged having that modular extension. I don't remember the brand though
BTW That little bugger of a cab was built with 1" presswood and lot of bracing. It weights a ton. Probably around 200lbs.
I bolted the aluminum stands to a piece of half inch thick Russian Birch plywood for extra stability, and that's probably how it is going to stay for a couple of years.
Can anyone help me calculate a proper capacitor to equals the 6db/octave compensation at 3.5Khz on a 16 Ohm driver? ;-)
Hi Lee,
Generally speaking C= 1/(6.2832*Fo*Zo),
so Fo=3500 Hz, Zd=16 ohm , attenuation of -6dB (Ro=16) ==> Zo = Zd*Ro/(Zd+Ro)= 256/32= 8 ohm ==> C= 5.7 uF,
but for different attenuation, different value of C would be get.
but such theoretical value has to be get AFTER the measurements,
in order to find out the real driver-horn response, and the sensitivity of the mid-bass (bass) driver in order to calculate the attenuation, and the influence of the 'high-pass" filter section.
Regards
Ivica
Hi Ivica. Thanks for the tech info. I am currently using an active crossover and two amps. Therefore levels can be infinitely altered. I know I can boost the frequency with the active crossover in order to get the CD correction (and that's what I am doing now) but using a passive way to attenuate the signal and replicate the CD curve is just a technical challenge. Also, so far I am quite happy with this simple two-way system. The next step is either to add a 2245 sub, or replace the two 2226 by a pair of 2245. I would loose midbass punch but would gain bottom end grunt. The result would probably be a more natural bass that I dont have to boost around 40Hz (where the 2226 dies).
I didn't try it because i should get about 15db boost at 20Khz from 3,5Khz. The graph you showed in the previous post isn't there.
Hi Lee,
Sorry, I have not been clear enough, so may be attached figure would explain:
with the suggested network I have taken that the 'Driver-Horn' response would start to decline from 3.5kHz ( -6dD/Octave), so under 'usual' expectation that Your driver can be 'modeled' as 12 ohm load suggested network would 'compensate' about 16dB at 20khz, relative to the 1kHz driver output).
So on my previous post expectable driver-horn response was presented.
Here with red line network with 12-ohm load response is presented.
Regards
Ivica
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