JBL 2205 or 2220, cab too small? - diyAudio
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Old 6th July 2011, 07:48 PM   #1
triode3 is offline triode3  United States
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Default JBL 2205 or 2220, cab too small?

I have a JBL 2245 in an 8 cubic foot enclosure tuned to about 25hz. It sounds nice and does well on a small 80W amp, but the box is just too large (stove like).

So, I have in my possession a JBL 2220B and a JBL2205A (or B, it is the Alnico). I would like to drop the HT sub and go for a nice sub that does not need a ton of power to do "hifi" bass to 40hz.

Here are the questions: I think I want the 2205 in this situation, due to the lower fs. Is that the correct choice? With either of these, my box calculations keep coming out strange. I get very small boxes if I choose sealed or ported enclosures (using DIY subwoofer formulas, or WinISD). I keep getting 1.1-1.5 cubic feet as a internal volume, which seems quite low to me (JBL is calling for 4 or 5 on up). Do I want sealed or ported with either driver? I do not think I want to go the horn route due to the size, I am looking to downsize...

Any input would be appreciated. Thanks.
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Old 6th July 2011, 08:07 PM   #2
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Hi -

Here's JBL's tuning recommendations for both:

http://www.jblpro.com/catalog/suppor...=219&doctype=3

Basically, JBL recommends a box size and tuning that is about the same as for the 2225 and 2226, E140, et al, but their Thiele-Small parameters for the 2205 show a Fs of 30hz, so you might be able to tune as low as 32hz with the 2205 with a little step down in response below 60hz (which may be made up by room gain, or can be readily eq'd out, depending on your installation). If you tune to 32hz in a similar size box as JBL recommends (by lengthening the port) , I think ported is not a problem SQ-wise, but I don't like what BR does to bass transients when tuned at 40 hz and above.

Both the 2205A and B are alnico. The A is supposed to be 8 ohm and the B is 16 ohm.

The 2220 is a great speaker (I'm using 2220A's in my Iron Lawbreakers), but they're not the best choice for subwoofer usage due to their very low Qts ( very high damping) and somewhat restricted Xmax. I'm getting full response to ~50 hz & they play to about 30 hz at port tuning before final roll off in 3 1/2 cu ft cabinets, but I'm using some out of the ordinary techniques to do so.

Last edited by thoriated; 6th July 2011 at 08:24 PM.
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Old 6th July 2011, 08:32 PM   #3
triode3 is offline triode3  United States
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Default That just brings about another question...

I looked at the JBL page before, just did not think to reference it... but it brings about another question.

If you look at the JBL page internal dimensions, that comes out to be 4.379 cubic feet, and the paper states 4.0 cubic feet. I have discussed with friends in the past the way to design cabs is to calculate the internal volume you need, then add in the volume consumed by the driver, then figure out a port volume.

But... everyone always says the port is critical in vented systems. I looked for answers on this a long time ago, and found no one could absolutely say "figure the size of the box from T/S, add the driver volume, calculate the port size" or "figure the size of the box, calculate the port size" or "figure the size of the box, calculate the port size, now add the driver volume to the size of the box when you build it" or "figure the size of the box, add the driver volume to the box, calculate the port volume then add the volume to the box".

What is the "proper" way?

Thanks.
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Old 6th July 2011, 09:05 PM   #4
djk is offline djk
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The calculated box volume is always net.
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Old 6th July 2011, 09:19 PM   #5
tb46 is offline tb46  United States
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Hi triode3,

You may want to measure the T/S parameters for the 2245H, and see how much smaller you can make the box, e.g.: in Hornresp. The 2245H seems more suited to subwoofer applications as it has a much heavier cone, and a much longer Xmax.

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Old 6th July 2011, 11:47 PM   #6
triode3 is offline triode3  United States
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Well, I tried to give that a go... I get to the part of the tutorial where it says hornresp will tell me that I have Invalid TH data. I make Vrc, Lrc, Vtc, Atc zero, but it still gives me an error. I got a nice response out of it with a normal horn, but I suppose I want to look at the tapped horn (to do that TH that everyone does around here to save space). The response looked good, although it fell like a rock after 60hz.

As for going for a smaller cab... the diysubwoofer excel sheet calls for a really small enclosure for it. Very odd. JBL calls for 8cubic feet minimum. I suppose if I could get the TH to perform in say 4 cubic feet I would do it. I will try to play with this hornresp thing more.
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Old 7th July 2011, 12:02 AM   #7
tb46 is offline tb46  United States
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Hi triode3,

I used the JBL T/S parameters, and came up with the attached vented enclosure model, it's still 160 L. I don't think this driver will work well in a TH of moderate size because of the low Fs.

Regards,
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Old 7th July 2011, 01:31 AM   #8
triode3 is offline triode3  United States
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Default Perhaps I need to change my question, or design.

Hrm, yes. The 2245 has a pretty low Fs.

Perhaps I am asking the wrong question... Lets step back and look at this for a second.

I have two JBL 2245H drivers, two JBL 2220s, one JBL 2205 and two JBL D130s. I have a 32' x 16' listening area. I am currently using the 2245 on a 90W amp, but I can build any amplifier I like (I build tube amps, own a company, blah blah). I have sold my two main speakers (monitors) and am building two FrugelHorn Mk3s with Fostex 4" drivers. I am moving away from HT and going back to HiFi. I have one JBL 2245 in an 8 cubic foot enclosure, but it is a little too large (WAF). I would like to get a smaller sub, or two. Again, it does not have to do HT.

So, having that info, what would the sub-gurus suggest? Smaller sealed box for the 2245? A single 2205? A pair of 2220s in small cabs? I am figuring that the D130s are pretty much out of the question with the high Fs and very small x-max. The reason I am looking at the JBLs is that I own them. Am I fooling myself and I need to purchase a ScanSpeak discovery 12" or the like? I think I need to stick with 15" or greater as the room has 18' ceilings (or multiple 12s?) Just not so sure. Any input is appreciated.

Thanks.
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Old 7th July 2011, 04:21 AM   #9
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Myself, I'd get a second 2205 or splurge and get ahold of two K145's (or LE15's, K145's or 2215's reconed to E145's - E145 cones have under spider VC side venting ) which all also have alnico magnets as well as underhung VC's (a good thing) and better Xmax, power handling capability and the underhung VC gives much improved resistance to demagnetization due to overpowering and has improved SQ, IMO, since the VC windings tend to all stay in the magnetic flux where they belong.

But I'm also a fan of coincident subwoofer and main speaker locations which not everybody is.

Last edited by thoriated; 7th July 2011 at 04:27 AM.
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Old 7th July 2011, 03:38 PM   #10
tb46 is offline tb46  United States
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Hi triode3,

It sounds to me as if you could do just fine with a lot smaller subwoofer driver than any of the JBLs on hand.

You need something to blend with the FrugelHorn Mk3s in a large volume space. Will the FrugelHorns be sufficient in that large a volume?

One thing that may be fun and easy is to try some of your JBLs in dipoles, or if you have a convenient location try the 2245H in an infinite baffle installation (in floor/wall/ceiling build-in).

Regards,
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