Scaled down version of the 4355 possible?

[manley]

Hallo all

somtimes you get a good deal, so it change your plans for what you was planing to build and it happens to me.

Because I was so lucky to get hold on a set of 2202H in a good condition the other day :D
i also have a set of 2351j-1 incoming

but i i really want to make something whit the 2202H :D

So right now i have

2202H or 2251j-1 mid
2445J High
2404 Ultra High

So now i need to figure out have to make the bass section, the easy way will be to make a 4355 encluser but it is to big for my room.
i cut also build a set of 4345 cabinest, but i have read that i will run out of bass before to with the combination i have planed.

So if i what to go down to 30-35Hz with two 15" woofer in one cabinet, more or less a scaled down and compact version of the 4355

i wonder if i can make a cabinet with these dimension W70cm D45cm H120cm (around 370L) minus the space for the 2202H/2251J


Will it then be possible to go down to 35 Hz with two 2235H or do i have to look after other woofers?


BR
Manley

[manley]

Hallo


I can see that PBN audio only use around 340L in the M2!5 with two 2235H and a Frequency response from 25Hz

is that possible?



BR
Manley

[Riley Casey]

Or you could reinvent the 4343 using the 2202 in place of the 10" midrange. That would allow moving the low to mid crossover down slightly and probably lower the crossover point between the 2202 and the 2445. You'd want a horn on the 2445 that supported a crossover point as low as 1000-1200 hz and matched the pattern on the 2202 at that frequency. It will all require reinventing the crossover or going tri-amped. Modern FFT analysis tools make it a lot easier to build from a cold start he said as he listened to his 2202 mids between his 2226 low drivers and 2344 horns.

[manley]

Hallo Riley

Right now i have JBL 2311 horn (minus lens) for the 2445J driver


If we look at the crossover for the 4355 it cross at 290 Hz, 1200 Hz and 10 kHz, so it match with what you will do,

then i have been searching this forum for some input, and found this thread about it, http://www.audioheritage.org/vbulletin/showthread.php?34844-JBL-4350-minus-one-woofer/page4

one write:
You are losing 6db of bass by ditching one 2235... 3db for the woofer itself and another 3db from the (un)coupling. Not a good idea in my opinion.

another write:
Now to your question, just my opinion, I would not use the top end of 4350 with a single 2235, not only does this creates audible imbalance but the resulting single woofer will reduce the low end sensitivity to 93dB, down from 96dB for the pair of woofers, the sensitivity reduction (99dB for the high and 93dB for a single woofer) will certainly compromise the low frequency performance with respect to the high end in the resulting system.


I was also thinking about adding a Yuichi-a-480 horn, but will that not add more sensitivity to the 2445J driver? and therefor make the db difference between the top an low bigger?


BR
Manley

[Riley Casey]

Sensitivity of any given driver is not an issue. In an actively crossed over system its a quick adjustment of the gain setting for a passband. For a passive crossover its a simple addition of a few resistors in the path while designing the crossover. Your often leaving output capacity on the floor with differences in sensitivity between drivers and that was a major concern in the early days of 30 watt tube amps but it's not a significant issue with modern electronics used in home listening. If you're carrying several tons of sound gear from one city to the next for 50 concerts across Europe or North America it becomes something to pay attention to.

In choosing this path you're taking on the project of designing an entirely new speaker with new capabilities and design questions. The 18" driver in the 4343 was easily able to outstrip the other drivers in the enclosure so you have excess capacity in terms of SPL below 250 hz and you simply need to take that into account as you implement your new design. A good starting place would likely be to design a suitable vented enclosure for the 18, add a back box for the 2202 as used in the 4355. Probably add the Yuichi radial horn as a top mount rather than internal to the enclosure with the tweeter above the horn all oriented vertically so that your horizontal pattern remains consistent. Probably want to build a mock up enclosure out of MDF to test your design choices and arrive at your active crossover settings then build your final enclosures when you're happy with the results. There are no JBL made passive crossovers to meet all of these combinations so while you could almost certainly design some after arriving at the crossover curves desired with a DSP crossover you may find in the end that active processing between the 18 and the 12 is best even if the higher bands can be done passively. Could all be a daunting task but it will give you a new and different speaker than anything JBL created.



Hallo Riley

...

I was also thinking about adding a Yuichi-a-480 horn, but will that not add more sensitivity to the 2445J driver? and therefor make the db difference between the top an low bigger?


BR
Manley