E 140-8 recone to 2235H's??

[Kay Pirinha]

Hello,

I just found an offer here in Germany. Offered are one or two »2235H's« at € 345,- each. Not exactly cheap, I know. The vendor says these have been recently reconed professionally and provides plenty of pictures. But alas, two or more pictures clearly indicate that the C8R2235 kits have been installed into E 140-8 baskets! At least the badges on the magnets' backs tell so.

Yes, I do know that 2225 baskets can be successfully reconed to 2235H's (or 2234H's, resp.). I own such a pair by myself (which were even more expensive than € 690,- a year ago ). But E 140's? Do they also share the basket/motor assembly with 2225's, 2234's and 2235's?

Best regards!

[Dr.db]

I believe the E-140 shares the same basket and mechanical dimensions of the magnet.
BUT the magnet on the E-140 is supposed to be magnetized slightly stronger resulting in a higher BL product.
Such a woofer should have slightly less very low bass compared to the original 2235 or 2225 assemblies...

[1audiohack]

The Dr is correct.

The magnet is 1/16” of an inch thicker and has more strength. The top plate, pole piece and basket is identical so all the geometry for the coil, spider and surround landing is correct.

My personal favorite 2234-2235 is built with an E motor. I like the added dampening and the slight increase in mid range (just over 2dB SPL) is easily tamed with a tick of EQ.

Not a drop in for say a 4430 but for a DIY project, heck yeah.

Barry.

[Kay Pirinha]

Thanks to both of you ! Much appreciated !

Ok, drop-in into a stock 4430 doesn't do. OTOH, couldn't exactly a 4430 benefit from the woofer's slightly increased midrange performance? Apart from that, are there possibilities to tweak a 4430 (better, a 4430 DIY project) to fit this E140/2235H bastard? Would a slight variation in box volume and/or port tuning do to cope with the altered LF performance?

Best regards!

[Ian Mackenzie]

if you add mass it will behave like a 2235

[Kay Pirinha]

Even more mass than that 35 g ring? Wouldn't this decrease f_s?

Best regards!

[1audiohack]

In a proper 2234, the addition of the mass ring, making it a 2235, drops the Fs by an average of 2.4 Hz and drops the 1kHz Level by 2.7 dB SPL. This was measured when I built six 2235’s in one batch.

I personally like the 2234 better. That said when building for a well engineered system like a 4430, I use the right part, unless you want to tackle the crossover or insert an EQ in the signal chain.

Barry.

[Ian Mackenzie]

Even more mass than that 35 g ring? Wouldn't this decrease f_s?

Best regards!

The effect of the higher flux is to raise the mid range response.

The additional mass compensates for this.

I don’t have the detail here but Edgewound our reconer expert advised on this work around.

[Kay Pirinha]

Maybe I misunderstand you, but I assume the following: If someone fits a C8R2235 kit with it's mass ring into a proper 15" basket, this driver will show exactly the same cone mass and suspension stiffness, hence the same resonant frequency as a stock 2235H. If I'd increase the cone mass as suggested, the resonant frequency decreases, as the suspension's spring rate remains the same. Am I right?

OTOH, this lower f_s would allow for a somewhat larger box volume and/or lower port tuning. This would yield in a extended LF range, wouldn't it?

Anyhow, this pair of drivers is gone since yesterday evening. So, any discussion on them sadly will be of plain theoretical nature, including this posting .

Best regards!

[Ian Mackenzie]

As l said l don’t have the details.

This solution came from Edgewound who has a detailed understanding of cone and driver baskets (magnets)

All you need to understand is this is a last resort work around.

Send him a pm for more specific information.

[1audiohack]

...All you need to understand is this is a last resort work around.

Not for everyone, I personally prefer to build them this way for my own use.

Barry.

[RMC]

Hi Kay,

* My writing here was almost complete before seeing your post about "this pair of drivers is gone since yesterday evening." It may still be usefull if another pair ever shows up later... Its free anyway, lol

I'm wondering if you're not chasing two contradictory things. Here's a few principles to keep in mind, as explained by Eargle & Bullock. Reading further you'll see where I'm going.

Varying BL product (higher for E motor) is roughly equivalent to varying driver Qts (but in opposite direction). So increasing BL reduces Qts, but it increases the driver's piston band sensitivity. On the other hand, LF drivers designed for high piston band sensitivity (e.g. E-140), with their lower Qts values, will have more difficulty achieving extended LF response (John Eargle, Loudspeaker Handbook, Pages 61 & 69).

On the other hand, Bullock on Boxes has indicated a number of times that transient response improves as driver Qts goes down (e.g. P. 19); He has modeled and shown too that lower Qts drivers don't yield as extended bass, also said that flatter alignments have better transient response (P. 31); finally he concludes "By selecting a low Qt driver you can attain a flat alignment and the best transient response." (P. 34).

You can't really escape from the above. Adding mass partially defeats some gain from stronger motor for a little deeper bass.

But an interesting aspect in low Qts drivers (e.g. Sound producing E-120, 130, 140) is also their nice transient response. In the 22 series 2205, 2220, 2227 (SR, sound reproduction) are other e.g. low Qts drivers.

Take a stock E-140 for example, it has a very low Qts of 0.17, and by keeping it low with your "bastard" driver as you call it there's more chances you will enjoy great transient response, though maybe not the ultimate LF you might have expected.

I can't speak on Barry's behalf, but I tend to think the reason why his favorite is the E motor/2234 could well be because of the better transient response of that "hybrid", without the extra mass.

In my view you'll have to decide what's more important to you. Personnaly, if I were you I'd follow Barry's trail. My usage of the 2205H (Qts 0.21) indicates it doesn' t have the lowest bass, but its fast and sure has nice transient response, which is why I've kept them all along.

As for your question about tweaking Vb and/or Fb to cope with the altered LF performance, well you would need first to determine the T/S of the "hybrid" driver you plan to make in order to model some scenarios in speaker desing software. Regards,

Richard

[Kay Pirinha]

Thanks a lot, Ian, Barry and Richard !

Well, now I'm feeling itched a fortiori! Coincidentally, someone offers two empty E 130 baskets in eBay Germany right now. Assuming they're identical to empty E 140's and have the same magnetic properties, I'm gonna buy these, order a pair of 2234/35 aftermarket recones from Simply Speakers and do the reconing by myself. Admittedly I've never performed a reconing procedure before, but, well, it's always the first time for everything and I'm just a passionate DIYer . Then I'll follow the advice of measuring the new speakers' TSPs, put the average of both values each into the simulator and see what happens .

Finally, I'll compare them with my 2235H »originals« (as said before, they're 2225's with C8R2235 cones) in my 4430s that I'm gonna build *asap*.

Have a nice weekend!