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Hans
02-05-2005, 01:39 PM
Please give me some ideas about a proper box and vent for 2213H. The smaller box the better. Im going to use it for PA. I need internal net volume and vent length and internal area. Also interested in tips about lining(?) (stuffing)??.

Hans K
Sweden

GordonW
02-06-2005, 03:29 PM
Please give me some ideas about a proper box and vent for 2213H. The smaller box the better. Im going to use it for PA. I need internal net volume and vent length and internal area. Also interested in tips about lining(?) (stuffing)??.

Hans K
Sweden

Minimum of about 2.5 cubic feet (~70 liters), with a 4" (100mm) diameter round port/vent, 10 5/8" (~27cm) long. This will give an Fb of about 35 Hz, and an f3 (low frequency rolloff point) of around 36 Hz.

Line the box with about 2" (50mm) thick fiberglass insulation, on all sides except the front panel. No other stuffing should be required.

If necessary to get the port length into the box without infringing on the rear wall, you can use a pipe elbow in the length. Just make sure that the TOTAL length, INCLUDING that through the centerline of the elbow, adds up to about 10 5/8", or 27cm.

Regards,
Gordon.

Hans
02-08-2005, 05:23 AM
Thanks Gordon!

The L-100 and the monitor has a volume of around 44 liters!? Why do you recommend nearly twice as much?

Hans K

GordonW
02-08-2005, 11:42 AM
The 123A (alnico) and 2213 (ceramic) actually want FAR more air volume than even 2.5 cubic feet, to behave optimally. In fact, the S70 Alpha (which used the 123A-1) was MUCH closer to optimum at about 6 cubic feet (170 liters, plus or minus), with a passive radiator- and went very close to 20 Hz on the bottom end. According to most box programs, 10 cubic feet (284 liters!) isn't out of line!

Those drivers are relatively high Q- IIRC, the specs for all the 123A/123A-1/123A-3/2212/2213 models are all in this approximate range:

Fs= ~25 Hz
Qts= ~.49
Vas = ~ 4.5 cubic feet (~128 liters), IIRC.

Run those numbers, you'll see... in a big box, they go LOW. But, in a box more along the size of 2.5 cubic feet (70 liters), they will handle more power, and will still give good bass "whomp". A good compromise for high-power application.

I currently have a pair of 123A-1 drivers in about this exact cabinet- 2.4 cubic feet (66 liters, plus or minus), tuned to about 30 Hz with a 4" diameter, 8" long port. They definitely do have prodigious output, and don't require a lot of power to do it! Not "hi-fi flat" exactly, but lots of bass slam. Just the ticket for DJ/small PA...

Regards,
Gordon.

Zilch
02-08-2005, 12:16 PM
Illustrating that driver's capabilities in big boxes, Gordon's design for a TCB isobaric sub using 123A's is here:

http://audioheritage.org/vbulletin/showthread.php?t=3922&p=36262

Maybe build THAT instead! :D

I know, I know, :offtopic:

[Be neat if someone built it though....]

Hans
02-09-2005, 01:37 AM
Thanks Zilch, very interesting! But, now it's PA we're talking about. Gordon, in this case size matters. I need a small box with a 2213 and some small mid-hi driver-horn. The bass will be taken care of ( if needed ) by a 15" sub. So please give me the data for a smaller box. And, of course, the power handling is of great importance.


Regards
Hans K

GordonW
02-09-2005, 07:17 PM
Use the L100 box... 1.6 cubic feet (~44 liters), with a 3" (~75mm) diameter round port, about 9 inches (~180mm) total length. Tuning of about 30-31 Hz, f3 of about 43 Hz, nice "fat" midbass that will pound the #*&^% out of you at 80 Hz... :D

Should work well with a subwoofer... but one thing you might try, if you high-pass (transition to the subwoofer) the 2213 at say, 50-70 Hz, you might want to just stuff (block up) the port completely, and use it as a sealed box. With at least a 50 Hz, 18 dB/oct. highpass crossover (most better active pro crossover are 18 or 24 dB/oct. on both lowpass and highpass) on the 2213s in 1.6 cubic feet, they'll handle full power without excursion limitation... and sound a bit "cleaner" than the ported alternative, not to mention possibly "blending" with the subwoofer better. Worth trying, it'll depend on whether you need the extra 70-80 Hz "whammy" or not...

Regards,
Gordon.

Hans
02-10-2005, 01:29 AM
Thanks again Gordon!!! Isn't this great? I'm sitting in Sweden and get expert help from US! Fantastic!

Gordon, about the duct, is it 9" (~229 mm) or 7" (~180 mm)? Which configuration has the best power handling capacity, when not using HP-filter, the ducted or the sealed?

Regards
Hans K

GordonW
02-10-2005, 08:55 AM
Vented has better power handling, down to 30 Hz. Sealed will handle full power down to 50 Hz, but drops like a rock in acoustic output below that.

I'd use the 9" vent, it results in flatter response... power handling difference between 7" and 9" is pretty nil...

Regards,
Gordon.

duaneage
02-10-2005, 06:52 PM
For what it's worth I would use a speaker with a Qtc of .49 in a sealed box simply because it has a high efficiency bandwidth product. Anything above Qtc .38 and you start to get into sealed designs. With a large Vas you should get usable bass down to at least 40Hz
just my .02

I built a pair for a someone using Audax 12"s that had a Qtc of around .45 We really should have made 3 Cu Ft sealed boxes instead of the 6.5 Cuft monsters. Bass cutoff was around 26 hz but there was no room for his sofa.

I agree with the larger box idea though. Easier to tune and more forgiving of design differences. And you can use a 4 inch tube that doesn't have to be so long, reducing wind noises.

GordonW
02-11-2005, 07:49 PM
Agree in theory, high Q driver == usually sealed box, but JBL used this exact driver in the exact box I mentioned (1.6 cubic feet, 44 liters) with a 3" diameter, around 7-9 (depending on which revision) inch long port in the L100 and 4311 monitors. Worked well enough for a WHOLE BUNCH of people.

If he's looking for power handling as an ultimate goal, the ported design with the 9" long port in the 44liter box will out-slam every other option using this driver, and will have good control over the driver with respect to excursion, down to port resonance. I'd use a 25 or 30 Hz rumble filter on it (just below port resonance)... with that, you'd be hard-pressed to damage it, unless you simply tried to slam over 200 watts into the cabinet continuously or something (ie, sheer over-power, burning it to the ground and whatnot)...

Regards,
Gordon.