recone for E 140, does a 2225 fit?

[willy]

Hello all, I need to recone a JBL E140. Recone costs about 200 euro's at Thomann Germany.
But I have a recone for a 2225 on stock and it obviously fits well. Same coilsize etc..
Now i know that this is unusual but hey, i'm a little short on money right now.
Could this work out right?

[grumpy]

IIRC, yes... But then it would be more like a 2225, not an E140.
Seems like there was a magnetic strength difference that would
affect the response a bit, also. All that info is posted here somewhere...


OK... here you go:
http://www.audioheritage.org/vbulletin/showthread.php?7850-E140-2225&p=75791&viewfull=1#post75791

[willy]

thanks, I think its wise to order an original recone.... There are more K140-s in my system and there seems to be a considerable difference in sensitivity.
Thanks for helping me out here...

[Eaulive]

IIRC, yes... But then it would be more like a 2225, not an E140.
Seems like there was a magnetic strength difference that would
affect the response a bit, also. All that info is posted here somewhere...


OK... here you go:
http://www.audioheritage.org/vbulletin/showthread.php?7850-E140-2225&p=75791&viewfull=1#post75791

In light of the aforementioned thread, I wonder why the response varies with motor strength?
I would understand a variation in efficiency, but I really don't grasp the mechanism that makes the frequency response change.

I'm kind of concerned because I have four E140 frames that I was planning to recone as 2225 for a future 4520 project that I plan for next summer.
I was hoping the more linear 2225 would sound better and more natural than the E140 (reproducer vs producer) and would benefit from the added magnetic strengh of a 1.35T magnet but now I have some doubts.

Anybody could shed some light on the technical reason why a more powerful magnet would change the frequency response? :dont-know:

[grumpy]

I don't expect it would be much, which is why I said "a bit".

Seems like you'd 'wind' up with a change in BL, as they (E140/2225H) start out about
the same but have different flux specs (so the number of wire turns must be different, yes?).

I don't design drivers, so perhaps someone with more experience in this area could explain
in layman's terms the inter-effects of changing one physical parameter (Flux density) on the
electrical response (nominally T/S specs).

There are things I would heartily speculate don't change, such as Qms, Pe, Sd, Mms,
but Vas, Qes, and even Fs (maybe) are less clear to me.

I could be wrong, but I don't think it's quite a simple as just changing the efficiency
with no other effect. Of course, if I'm corrected, then I get to learn something :)

[subwoof]

As a general rule when you increase magnetic strength you gain efficiency but the freq response shifts higher. The E140 takes advantage of that plus adds a chrome dome. In addition the voice coil former is a lighter aluminum ribbon instead of heavy paper.

The E140 is considered a sound "producer" and is a bit colored in it's response.
The 2225 is considered a sound "reproducer" and is designed to be flat in it's bandwidth.

BTW I used both models in the single and doubles I used for SR and I preferred the E140. The horn itself and it's response says no matter the driver, it won't be flat but punch is everything...:)

I put a pair of E140/4530's onstage for a bass player once with a PSA2 in bridged mono and when he plucked that B string ( 5 string musicman ) he shook the room more than the entire PA.

sub

[1audiohack]

With loudspeaker diaphragm assemblies falling within the prescribed range of mass for good coloration and response, (reproducer vs producer) the other major design factor responsible for efficiency is the magnetic strength or flux density, B.

Bring to mind the sealed box response curve with a maximally flat Butterworth curve with the knee at 50 Hz
designed with a driver with optimum magnet strength.
If you double the magnetic strength you get the expected +6Db from about 500Hz on up. At low frequencies near resonance the results are perhaps the reverse of what might be expected. The larger magnet has actually halved the LF power at resonance through overdamping, and the mid-band has risen 6 Db the
effective bass loss totals 12 Db.

The motors you are talking about using yield an increase in magnetic flux density of about 12% and are going in an enclosure that pretty much let's go of the driver down stairs anyway. I would do it and not look back.

Four out of six of my 2234's are in E baskets and it's measurable, but not audible in vented enclosures. It's funny actually when you do driver parameters constant voltage (directly connected to a real amp with a VI box) that the resonant peak of a 2234 is almost not discernible. The motor is so strong and the cone is so light.

[ivica]

I don't expect it would be much, which is why I said "a bit".

Seems like you'd 'wind' up with a change in BL, as they (E140/2225H) start out about
the same but have different flux specs (so the number of wire turns must be different, yes?).

I don't design drivers, so perhaps someone with more experience in this area could explain
in layman's terms the inter-effects of changing one physical parameter (Flux density) on the
electrical response (nominally T/S specs).

There are things I would heartily speculate don't change, such as Qms, Pe, Sd, Mms,
but Vas, Qes, and even Fs (maybe) are less clear to me.

I could be wrong, but I don't think it's quite a simple as just changing the efficiency
with no other effect. Of course, if I'm corrected, then I get to learn something :)

May be some added mass of about additional 20~30gr ( 155gr+30gr on 2235, would reduce Mid.freq. amplification because of larger Bm ( 1.35T on E140 compare to 1.2T on 2235)

[Eaulive]

May be some added mass of about additional 20~30gr ( 155gr+30gr on 2235, would reduce Mid.freq. amplification because of larger Bm ( 1.35T on E140 compare to 1.2T on 2235)

Yes, but my question was with a 2225 cone in a E140 basket, the magnet strength is 1.35 instead of 1.2.
Wht exactly are the physics behind the change in frequency response when the motor strength in increased ?

[1audiohack]

An increase in motor strength increases the amplifiers ability to accelerate AND decelerate the cone mass. This shows up as increased hi frequency output due to increased acceleration against the mass and decreased low frequency output due to increased control of the mass as it approaches resonance as dampening is increased.
The magnitude is skewed toward the HF region as is the knee of the curve.

If you want an equation you will have to wait. :)

[Eaulive]

An increase in motor strength increases the amplifiers ability to accelerate AND decelerate the cone mass. This shows up as increased hi frequency output due to increased acceleration against the mass and decreased low frequency output due to increased control of the mass as it approaches resonance as dampening is increased.
The magnitude is skewed toward the HF region as is the knee of the curve.

If you want an equation you will have to wait. :)

No need for an equation, I can understand the process.
Makes sense to me, thanks! :)