2245H reconed as 2240H what is the result

[mbottz]

I am looking at a speaker which has the 2245H reconed as a 2240H. What is the effect of such a transplant? Is it good or bad? Anyone know the answer?

Thanks

MB

[spkrman57]

I'm fairly sure that 2245 and 2240 are same cores.

I have 2245 cores that have been reconed as 2240's arriving next week and will let you know how the results are when I have a chance to play them awhile.

Ron

[Guido]

A 2245H reconed as 2240H is a 2240H.
Ok, except the foilcal. :)

[mbottz]

As a subwoofer is the 2245 superior? Is it something that if played side by side in the same type enclosure I could hear a significant difference? What does it do to the value of a B460?

Thanks

MB

[grumpy]

As a subwoofer is the 2245 superior?

For home use? I'd say yes.


...hear a significant difference?

or feel, ... most likely.


What does it do to the value of a B460?

Current price of a 2245H recone ;)

[spkrman57]

These are freshly reconed and have not been broke in yet:

I listed the serial nrs that were used for the 2245 since I wanted to keep both identifiable.


JBL 2240H #24026 2240H #24010
Fs 31.68hz ---31.2hz
Qes .32 ---.31
Qms 7.2--- 6.8
Qts .31 ---.3
Le .87mH--- .87mH


It will take me a few weeks and break them in before they each get their own 8 cubic ft ported cabs for LF duty between 40hz and 200hz.

My room is so small that I don't worry about loading down below 35hz. The living room will not energize with those low notes, but the garage, kitchen and outside will!!!

Ron

[spkrman57]

I see the Qms values I measured with WT2 are higher than the JBL 2240H specs.

Does anyone have ideas on what caused that figure to be off???

Could it be from the voice coil not being in the exact location in the gap???

Or will it decrease upon break-in???

Thanks for all comments/opinions!!!

Ron

[JBL 4645]

I guess it’s the foam surround that you find discouraging and ribbon cloth surround reinsures you with easy of mind and conference.

[pos]

Here is a simulation of a 2245H (green) and a 2240H (red) in the B460 (8ft 26Hz)

group delays are also higher for the 2240H

[grumpy]

Hi Ron,

Change in compliance (Cms) will affect Fs (more compliance, lower Fs).
Change in Fs will affect Qms in direct proportion.

So... I'd expect a break-in to increase compliance, lower Fs, ... and therefore Qms.

http://en.wikipedia.org/wiki/Thiele/Small

As to what's 'normal' for a newly reconed 2240, perhaps you already have the
best information. :)

-grumpy

[spkrman57]

That is the info I was hoping for.

I have to wait until I get some cabinets fixed up for them(3.8 cu ft tuned to 48hz result of F3 of 61hz per JBL sheet I found).

I plan to use them with 2235 subs to fill in the bottom end.

Regards, Ron



Hi Ron,

Change in compliance (Cms) will affect Fs (more compliance, lower Fs).
Change in Fs will affect Qms in direct proportion.

So... I'd expect a break-in to increase compliance, lower Fs, ... and therefore Qms.

http://en.wikipedia.org/wiki/Thiele/Small

As to what's 'normal' for a newly reconed 2240, perhaps you already have the
best information. :)

-grumpy

[grumpy]

That'll be an interesting setup. I hope the 2235's can keep up :)

I'd be curious to see how/if the 2240's actually do drop Fs after some use,
...if you have time (and feel like bothering) to remeasure later.

[spkrman57]

grumpy,

I will be running the JBL 18" as a 2-way with compression driver and horn on top driven by either a single ended (triode-strapped EL34 monoblocks - 6 watt output) or a McIntosh MC-240 tubed amp. The 2235's will get a much larger SS amp to fill in the bottom.

My listening room is very small, so not much wattage required.

I will post results after burn-in when time permits.

Thanks, Ron




That'll be an interesting setup. I hope the 2235's can keep up :)

I'd be curious to see how/if the 2240's actually do drop Fs after some use,
...if you have time (and feel like bothering) to remeasure later.

[spkrman57]

In a few weeks I'll have a pair of 4 cu ft cabs w/6" dia port 7" long for approx 40hz tuning.

Crossover will be 500hz to 2441 on 350hz Edgar tractix horn with bullet tweeter on top.

I will post when all the goodies come together and get installed.

Regards, Ron

[robertbartsch]

POS:
The graph you posted is interesting.

I have a couple of 2245Hs and was told they are not suitable for two-way systems since they cannot play flat much over 100Hz. According to your graph, this is not true, I suppose.

[pos]

This simulation does not tell you much about the real response and the way it behaves, other than in the LF.
There are many things to consider: cone breakups, off axis response, mass of the cone/power of the magnet, etc.

Here is the mesured frequency response:
http://audioheritage.org/vbulletin/showthread.php?t=10654

The 2245 was used up to 320Hz in the 4345. Using it above that frequency looks like a bad idea.

http://www.audioheritage.org/vbulletin/showthread.php?t=16898
http://www.audioheritage.org/vbulletin/showthread.php?t=14587