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Thread: 2470 Franken drivers

  1. #1
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    2470 Franken drivers

    I've been all over the forum looking for information on what to do with 2470 drivers without diaphragms. The general answer seems to be the original phenolic ones are discontinued, install 2425h diaphragms. This has me wondering:

    1) How will the different BL affect the sound? The 2470 motor is 19,000 Gauss and the 2425 is around 17,000.

    2) What are phase plug differences and how might that affect the frequency response? 2425 is 800 hz to 20,000.

    I understand there are limited options with drivers like these. The drivers were free and in pretty bad shape when I got them, dirty, missing screws and terminals. I cleaned them up and put them aside for years. They've been handy at filling empty shelf space. Its time to do something with them, but it just raises a lot of questions about what the result will be.

    Any input would be helpful. Maybe someone who has installed the 2425 diaphragms could chime in.

  2. #2
    Senior Member grumpy's Avatar
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    For $80/ea, a pair of radian dias will make those cores usable again. A bit more for titanium from JBL.
    Regardless, the phenolic drivers didn't warrant a impedance control ring on the pole piece to extend the
    frequency response, so I wouldn't expect them to turn into 2420 or 2425 equivalent drivers, but maybe
    close enough, depending on your application (i.e., might need a tweeter).

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    Thanks for the reply grumpy.

    This helps with my expectations. It'll be short on the high end.

    I'm planning to use these, for a while, in a man cave setup. I scored some 2226's in very good condition for mid-bass, am hunting for 2241's or something for subs, mids and possibly a tweeter. I've got a driverack px, but will upgrade to the driverack PA and run 3 way from crown x1000/xls 1002's. Something that could cover mids and highs would be good.

    So, I was looking at the 2470's and thinking mids and highs. I know I will want to upgrade at a later date. I would have to push the xover to 800 or above, which doesn't fit perfectly with the 2226's. It would be an ongoing project. I'm still relatively young! LOL

    I actually have some Radians in my 2410's and could upgrade those to free up the Radians. I had been thinking of that anyway.

    Thanks again. This should get me going.

    Jim

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    Dang. Amateur speakerdave's Avatar
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    According to the data sheets the 2420 and the 2470 both have the silver ring.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    SpeakerDave,

    You're right! Its right there on page one of the literature, just waiting for me to read it. Actually, I did read the sheet, but the part about the silver ring didn't really register. I'll be doing some more reading.

    I'll probably have to run a sine wave sweep and see what it can actually produce in the higher range. I'm curious to see how the stronger motor will affect the lower range as well. Its about 4000 Gauss bigger than my 2410's and it will be interesting to see how the Radian diaphragms behave. Testing will be a bit crude. I'm planning to run pink noise and record with RTA into Pro Tools 12, then run frequency/spectrum analyzer. The preamps tend to color the signal, but it should be good "ballpark" data. If I get anything useful, I will post it. I'll have to get new diaphragms for the 2410's first. I can try both diaphragms, just to get a reference.

    Now I'm excited to see what I get! It will take a few weeks for the new diaphragms.

    Thanks,

    Jim

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    Senior Member grumpy's Avatar
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    Always happy to be corrected
    May have had 2460 on the brain (shrug). Seems odd they’d bother trying to extend response with a phenolic diaphragm, but looking forward to your result.
    Maybe someone can confirm or debunk same motor/plug was in common to both 2420 and 2470? both being 19000 Gauss.

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    Quote Originally Posted by GoldcountryJim View Post
    I've been all over the forum looking for information on what to do with 2470 drivers without diaphragms. The general answer seems to be the original phenolic ones are discontinued, install 2425h diaphragms. This has me wondering:

    1) How will the different BL affect the sound? The 2470 motor is 19,000 Gauss and the 2425 is around 17,000.

    2) What are phase plug differences and how might that affect the frequency response? 2425 is 800 hz to 20,000.

    I understand there are limited options with drivers like these. The drivers were free and in pretty bad shape when I got them, dirty, missing screws and terminals. I cleaned them up and put them aside for years. They've been handy at filling empty shelf space. Its time to do something with them, but it just raises a lot of questions about what the result will be.

    Any input would be helpful. Maybe someone who has installed the 2425 diaphragms could chime in.
    I am using 2470 cores with 2425 diaphragm

    They are fine.

    If you look closely the difference in spec is 117 dB versus 118 dB plane wave tube

    Depending on prior use the age of the driver being alnico is possibly going to impact on the bl

    Clean them up that’s s what l did and see how you go

    Get all the dust and dirt out of the gaps.

    For religious reasons l prefer alnico over ferrite compression drivers

    I can post a FR response if you want on a 2307/2308

  8. #8
    Senior Member grumpy's Avatar
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    Thanks Ian. I’d be interested in your 2307/8 plots when you have time.

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    On the weekend.


    Of course a new diaphragm always sounds better than an old fatigued diaphragm...Lol.

    I had to really clean them out to get them working but they are good now.

    Maybe we should find Ken’s cleaning post?

    I think it was double sided tap, a solvent clean and compressed air?

    Then the diaphragm alignment. That’s the tricky bit as sometimes the holes needs a slight ream out to centre in the gap.

    Then check the pad on the back plate.

    That stuff matters

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    Ian,

    Plots would be great!

    Cleaning was a big chore on the motors and I'll probably go over them one more time just for good measure. Ken's cleaning post? Maybe I should look for this before starting.

    Foam is gone from the back caps, turned to crumbly mush when I last cleaned them, so replacement is needed before using them. Not entirely sure what the best replacement is.

    I was looking at the motors last night and saw screws taped on the inside of one of the caps, probably what I found with them. These were probably what was holding the fried diaphragms in. There are black oxide type and what looks like aluminum screws. What type of screws did you have holding your diaphragms? I'm also missing the screws for the back caps. Still a little work to be done here.

    You really do have to love this stuff and my wife jokes I love my speakers more than her!

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    Looks like the screws may be #6-32 by 3/4" for the diaphragm (non-magnetic) and #8-32, unknown length for the back cap. I found this elsewhere in the forum:


    For a 2410;

    The 3 screws ( machine bolts ) for the diaphragm are #6-32 by 3/4" long ( or @ 19 mm long )

    The 2 screws ( machine bolts ) for the back-cap are #8-32 by 1.5" long ( or @38 mm long )

    For a 2420/1; Don't have one to measure

    For a 2426;

    The 3 screws ( machine bolts ) for the diaphragm are #6-32 by 3/4" long ( or @ 19 mm long )

    The 3 screws ( machine bolts ) for the back-cap are #8-32 by .5" long ( or @ 13 mm long )

    The bolts that hold in the diaphragm should be nonmagnetic ( brass ) - if you can find them .

    regards <> Earl K

    Pretty cheap at Home Depot or Lowes'.

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    Ditto on the wife.

    No worries

    They all corrode

    I have seen this a lot. I think it’s moisture inside and non compatible metals.

    In the back cap foam or Felt

    What horn are you using?

    This is a ground plane measurement 10 dB per division @ 2 m using LinearX LMS
    2425 dusted diaphragm on 2307/2308 lens assembly
    Copyright Ian Mackenzie 2018
    Attached Images Attached Images  

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    Up late and saw the measurements. Awesome to see this. I'm surprised at the levels down to 500 hz, as I expected it to roll off at 700. Definitely not making it to 20K.

    I haven't decided on the horn. I've been using some 2410's with Smith horns I built for my main system, with O76/2403 above. Crossovers are 3110 and 3105's. I believe the xover is around 5k to the 076. I like the combination. I'm thinking an active xover and time delay might improve it a bit.

    I suppose, if I can't get above 16k with the 2470's, I may have add an ultra high driver. That would probably affect my choice of horn.

    On a fun note, I saw these mini Smith horns that use a 2404, on the forum and almost wanted to build a couple! LOL They are not as efficient as a stock 2404.

    http://www.audioheritage.org/vbullet...-Smith-Selsted

    Maybe a 2344 would work. The 2307/8's look smooth between 500 and 10k. I've heard 2370's can be harsh. On the other hand I've wanted to play with some modifications to the Smith horns and they would be less expensive, at least to get things going.

    If you have suggestions, I'm pretty open to looking at options.

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    Cool mate.

    Spin the wheel it’s up to you!

    The 2470 is not ideal on the 2 inch Smith horn. A 4 inch driver is better.
    A mini Smith horn might be better on the 2470 plus a uhf device.

    The 2 inch smith horn cuts off above 10000 and you will need a uhf device so it’s expensive.

    The 2344 bi radial horn based on personal experience is an excellent stand alone bi radial horn.horn for the 2470
    Designed to across over atv1000 it will mate well with a 10 -15 inch driver.
    It’s good up to 16 k hertz on the 2344 due to the narrow diffraction throat.

    The 2307/08 is imho a very accurate combination with the 2405 with the right crossover network using the 2123
    It’s strength precision but it’s not a CD horn.

    At the moment the 2344 is Big Bang for buck in your space.

    Look at Jamin Jersey for the 2344

    Have fun

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    Senior Member ivica's Avatar
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    Quote Originally Posted by Ian Mackenzie View Post
    Cool mate.

    Spin the wheel it’s up to you!

    The 2470 is not ideal on the 2 inch Smith horn. A 4 inch driver is better.
    A mini Smith horn might be better on the 2470 plus a uhf device.

    The 2 inch smith horn cuts off above 10000 and you will need a uhf device so it’s expensive.
    .........
    The 2307/08 is imho a very accurate combination with the 2405 with the right crossover network using the 2123
    It’s strength precision but it’s not a CD horn.
    ......
    Have fun
    Hi Ian,
    But 2307 WITH 2308 has very wide horizontal dispersion, and if listening in home room, it would be very useful, not to mention that
    it would produce almost flat response (due to its narrow vertical response on high frequency).

    regards
    ivica

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