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View Full Version : 2 way center using 2251J?



emilime75
01-16-2017, 09:39 PM
Trying to determine the low end capability of the 2251J, and if it would suffice in a 2 way center channel. Has anyone played with this driver as a woofer? How low can it go? Enclosure size? Sealed or vented?

emilime75
01-17-2017, 10:27 AM
It looks like it's only been used in the HLA4985 and 4348...if you don't count the revised unit in the SK2-1000.

In the HLA and 4348 it's high passed at 300Hz. I was hoping I could get decent output from it down to about 90-100Hz.

Anyone?

baldrick
01-18-2017, 12:59 PM
I had the same idea, makeing someting similar to SK2-1000, I used dual 2251J and 2435. I've bearly listened to Sk2-1000 but can't understand that it give a similar result as it gave me because it didn't sound very good at all :(

My conclusion was that 2251J works as a dedicated midrange but not a "fullrange" woofer and probably there are quite a diffence compared to the woofer used in Sk2-1000 even though they seems very similar.

emilime75
01-18-2017, 06:31 PM
Hmmm, that's a bummer. Out of curiosity, could you share some more details about what you built?

Size of enclosure?
Sealed/vented? Tuning, if vented?
Active/passive?

I've been modeling the 2251J in WinISD a little bit tonight and it's looking pretty good, the only exception being is I don't know if JBL's excursion spec is Xmax or Xmech. If Xmax, all should be good. If Xmech, then I'm not so sure. Here's a few screenshots.
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emilime75
01-18-2017, 06:35 PM
I've got 1 new 2251J and D16R2451SL coming in the mail. I want to order the new STX F15 guide, but I'm really not looking forward to making an adapter for the 2447 core so I'll probably try it on my 2381, first.

Earl K
01-19-2017, 03:32 AM
Hi,

If you read 2251 Variants (http://www.audioheritage.org/vbulletin/showthread.php?17010-2251-Variants) you'll see that for HiFi use, the 2251 needs to have @ 20 grams added to the cone.

That will change the driver from a pure midranger to a midbass unit ( better suited to your application ) .

:)

pos
01-19-2017, 05:58 AM
EQing down the midrange will do basically the same thing as the added mass (see 2234 vs 2235 comparison in SPL) with less Watts burned into the VC.
Adding mass is a trick that is only really useful with passive crossovers.

bldozier
01-19-2017, 06:20 AM
Just curious what the hf is

emilime75
01-19-2017, 08:52 PM
Just curious what the hf is
As in what driver and guide I'll be using? Or how high will the 2251J play?


EQing down the midrange will do basically the same thing as the added mass (see 2234 vs 2235 comparison in SPL) with less Watts burned into the VC.
Adding mass is a trick that is only really useful with passive crossovers.
Yes, as long as excursion can be kept in check, which is something I am still not sure about. According to the model, it's below Xmax if, indeed, JBL's excursion spec is Xmax and not Xmech. Anyone know?

The excursion plot above also shows the filters modeled. A wide, 3 dB bump at 150Hz and and a highpass at 65. That's all it took to get the response shown.

emilime75
01-22-2017, 10:55 AM
Anyone see any problems with the above model? Does it look realistic? Will I destroy the driver?

emilime75
01-23-2017, 08:51 PM
1x D16R2451SL diaphragm and 1x 2251J are in. The more I think about it the more I'm leaning towards turning this into a 3 way with a 2226H. I'll build the above modeled enclosure first and see how the 2251 does, just afraid of damaging it by pushing too low.

The next question is what waveguide to use. I'd like to try the F15 guide, but I don't have a source for the adapters needed to mount the 2447 core to it. Thinking I might go big with the 2384.

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