Jbl 2241h - 2235h

[kawmic]

Can anyone tell me what's good or bad, if I change the surround on my 2241 with one from a 2245?

[RMC]

Back later with a reply. No time right now.

Richard

[Eaulive]

What are you trying to achieve?
It'll probably work, but as far as predict the result, I'm not sure about that.
If you would have wanted to replace the surround of a 2240 with the surround of a 2245, I guess it would have been more predictable as they are the same series motor, and assuming the spiders are identical, one could assume that you effectively turned your 2240 into a 2245.
But a 2241.... uncharted territory :confused:

[RMC]

Hi kawmic,

First, your post doesn't say why such surround replacement? Damaged and 2245 one is the only available to you? Or just trying for possibly improved performance? Subject to this, here are some thoughts.

The driver's suspension system is made of two parts, the surround and the spider, both working together. As i understand it you'd have a 2241 spider and a 2245 surround on the woofer. Normally a driver is a coherent whole, but sometimes part(s) may be interchangeable.

Lets assume 2241 spider is comparable to 2245 spider, there's no guarantee it is, excursion data being different for the two drivers it might be a clue.

* 2241, cloth type surround, stiffer suspension, Vas parameter 310 L, Xmax 7.6 mm, sensitivity 98 db

* 2245, foam type surround, more compliant suspension, Vas parameter 820 L, Xmax 9.5 mm, sen. 95 db

At that point you still have the woofer compliance issue in your way. Usually compliance (Vas) allows for some leeway, somewhat more or less is not critical (e.g. EV, Keele, Eargle). However, here the difference is very large and this normally impacts the proper box size for a driver.

Moreover, the 2245 has about 2 mm more of cone travel. This may not be available IF the 2241 spider is stiffer than the 2245. As i recall, Cms is the parameter for suspension compliance but JBL doesn't provide that figure (not seen in 2241 and 2245 tech sheets, nor in the TS table).

As for driver sensitivity for both drivers (same 100-500hz range) the 3 db difference is notable. Checking Eargle's driver efficiency formula, well Vas is part of the equation, so that number may influence the sensitivity rating.

Good or bad? Replacing a surround with a similar one is a better bet in my view. In the case of your question its a flip of the coin type answer. You can't be sure the driver will behave the same or even sound the same. Will it be optimal, probably not, will it "work", probably yes up to a point. Although can't say the suspension's restoring force would remain as it was. "Frankensteining" the woofer should be as last resort.

I know The Speaker Exchange had/has a listing for a 2241 cloth surround but i don't know if its actually still available. Regards,

Richard

[jbl4ever]

Hello kawmic, some other things to consider. The 2245 has a FS of 20hz and the 2241 a 35hz with a big difference in moving mass. The 2245 moving mass is .185kg and the 2241 has a .145kg. It will not get the last octave as well 20-40hz. Another bigger one is the voice winding depth as the 2245 has a 24mm .96" and the 2241 a 19mm .75" With the softer surround and the shorter coil if you drive it hard into that last octave the distortion will rise as the coil is possible not centered in the magnetic field