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Thread: 4320 Project

  1. #76
    Senior Member Woofer's Avatar
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    Quote Originally Posted by ritchie View Post
    Thanks for both replies..

    1) How would I tell if my remaining 075 tweeter is alnico or ferrite? It has the single side -bolted circular frame retainer, that slips over the front of the bullet and retains it in the port, and it's not the front- 4 x screw-mounting model.

    2) Is the Northridge JBL 2235H woofer so much different to the Northridge JBL 330757-001 woofer?

    advice really appreciated and thanks again..


    regards richard
    bg
    Unfortunately Richie, your location makes it tough, but yes, I too would recommend trying to source a single 075.
    Post a Wanted Ad here and see what happens. I'm sure someone here would have one. Worst case scenario, is that I know someone who might be persuaded to sell you one, but it's in Australia, so postage would be really expensive.
    I'll ask him in the meantime to see if there's one spare and the cost, but it'll be working at least and highly likely to have an original diaphragm. I'll know more tomorrow as it's night time here now, and everybody [except me] is in bed…..
    As far as what you have, it would have to be an AlNiCo, only because those boxes are older than when ferrites came out. [I think…. anyone feel free to correct me if I'm wrong.]

    Now as far as the 15" are concerned, try to locate a pair of JBL 2215. They come and go. They're actually one of only a couple of woofers from that series that have an fs of 20Hz.
    Depending on just how loud you want to take these things, I feel they'll be more than adequate, and the 4320 is actually tuned to them to start with.

    Forget about the Lenses for now. EVERYBODY I know, including myself has soon learnt that the box sounds great without them.
    If you're mainly a single person listener, then dispersion is the last thing you should be worried about, as you just end up sitting in the 'sweet spot' anyway, so no need to worry about what it sounds like 'off axis'.

    I'll get back to you in a day or so about the 075….

    Cheers.

    ps: I will add, that it's the box that makes the bass sound what it is. If you're a low level SPL listener, you could just about throw anything in the way of a 15" woofer in them, and they'd still sound great to a non-critical listener, and you just might be happy with it until you could find and afford the real things. At least you could still be enjoying the use of them while you're waiting….
    [let the arguments begin…. LoL]
    I might be deaf, but I can still hear da bells! (Quasimodo)
    .... Oh, and the Kick Drum.

  2. #77
    Senior Member ivica's Avatar
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    Quote Originally Posted by ritchie View Post
    Thanks for both replies..

    1) How would I tell if my remaining 075 tweeter is alnico or ferrite? It has the single side -bolted circular frame retainer, that slips over the front of the bullet and retains it in the port, and it's not the front- 4 x screw-mounting model.
    ...
    regards richard
    bg
    Hi ritchie,

    look !

    reagrds
    ivica
    Attached Images Attached Images  

  3. #78
    Senior Member Woofer's Avatar
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    Yes, do look at the above pics.
    …. and be aware, a JBL 2402 is the same as a JBL 075. Just a different foilcal [badge] and paint.
    The ferrite 2402 will have an 'H' suffix after the model number. e.g. JBL 2402H
    I might be deaf, but I can still hear da bells! (Quasimodo)
    .... Oh, and the Kick Drum.

  4. #79
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    Quote Originally Posted by Woofer View Post
    Yes, do look at the above pics.
    …. and be aware, a JBL 2402 is the same as a JBL 075. Just a different foilcal [badge] and paint.
    The ferrite 2402 will have an 'H' suffix after the model number. e.g. JBL 2402H
    Thanks so much for the valuable help to everyone..

    I have a ferrite 075 then, no black paint at all, only black paint on the rear dust cap.(but no rear suffix 'H' after the model number , and only 'Model 075'.) Impedance 8 ohms. and Serial Number 70325.

    Regarding the 15's, I'm totally confused :-(
    I looked up the frequency response graphs of both the JBL 2235H and the JBL 330757-001's (that I bought as replacement woofers) and I could not see much difference in the graphs at all. :-((

    The bottom end (on both) at around 20hz does not seem to kick in until 25hz or so, at negligible levels, and then more reasonably at 85db at 25hz or so (on both) and then they both jump to 90db (or a very more respectable 98db in the 330757-001's case.) at around 40hz.

    I see that the response of the 330757-001's is less linear and more peaky, and I recognise that the later-manufactured 330757-001's are generally used as low-powered PA sub-drivers, but I can't see much difference at all in the specs, or am I reading them incorrectly? Are the JBL 330757-001's so inferior to JBL 2235's??

    The 330757-001's seem to have a really solid bottom end, and they're certainly defined and tight (I'm driving them with a 300wpc rms Bose power amp, and at concrete building-shaking levels:-)

    The horns seem a bit washy and indefinite and the mid-range is a bit rubbish and ill-defined.. Recorded speech does not sound natural, and the top end is definitely absent..
    I can't understand how listeners could say that without the 075 tweeters, that they are listenable or usable at all.. Even with the horn crossover cranked up, crash and ride cymbals and hi-hats are almost non-existent.. :-(

    But I suppose I'm maybe trying to compare the sound of my 2 x pairs of control 5's and control 5 sb, and the 4320's are a generation older and possibly a bit lacking in comparison.
    But they look really good in their new textured grey livery, and their cleaned black front cloths and lovingly polished escutcheon plates, and I shall persevere !!
    Of course, the wife says that the 4320's are far too big.. but I realise that no-one ever said that life was going to be a bowl of cherries, so I just don't listen.. :-))

    thanks to all.

    ritchie
    bg

  5. #80
    Senior Member Woofer's Avatar
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    Just as an experiment, reverse the wiring [phase] on your 15", and see if your midrange improves at all.
    It's worth a shot…..

    Even with the horn crossover cranked up, crash and ride cymbals and hi-hats are almost non-existent
    …. but if you bypass the 075's x-over, [disconnect it completely, but only for now 'till u get a replacement ring] you may find the mid/highs will extend because the horns then aren't being rolled off by the high x-over.

    ps: I've forwarded a link to this thread to a mate. He may be able to help with a replacement ring.
    I've asked him to PM you direct.
    I might be deaf, but I can still hear da bells! (Quasimodo)
    .... Oh, and the Kick Drum.

  6. #81
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    Quote Originally Posted by Woofer View Post
    Just as an experiment, reverse the wiring [phase] on your 15", and see if your midrange improves at all.
    It's worth a shot…..

    I tried the phase coherence with a meter, and checked that bass response in the centre was reinforced and also in the 'sweet spot' so I think the 15"s are in phase, but I shall check the horns phase.


    …. but if you bypass the 075's x-over, [disconnect it completely, but only for now 'till u get a replacement ring] you may find the mid/highs will extend because the horns then aren't being rolled off by the high x-over.

    OK.. Thanks again Woofer. I shall try that.. It really makes sense when considering my mid-range symptoms and the washy sound and complete loss of top-end.. Great!


    ps: I've forwarded a link to this thread to a mate. He may be able to help with a replacement ring.
    I've asked him to PM you direct.
    Many thanks again... good people..

    regards

    richard

  7. #82
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    Do the crossover caps deteriorate?

    Is there anything more that I should know about the 4320 crossovers please?

    For example, would the capacitors or any other crossover components deteriorate after 45 years, and fluctuating storage temperatures over that time?
    Bulgaria gets down to minus 20 celsius and up to plus 38 celsius (over 100 farenheit) and the monitors have been stored for a lot of years in a non-air-conditioned building.

    I note from other 4320 posts that the mid-horns should be out of phase with the bass drivers and the tweeters?
    This is presumable to time-align the mid range at centre listening position?


    many thanks for everyone's help.

    regards

    ritchie
    bg

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