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Thread: Diaphragma 075 the same as 2405 Alnico?

  1. #1
    Member Dieter's Avatar
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    Diaphragma 075 the same as 2405 Alnico?

    Hi,
    is the diaphragma from the 075 the same as in the 2405 Alnico?
    If no, is it possible to replace the 2405 diaphragma in the 075 and change the horn for 2405?

    Thanks

    Dieter

    PS: Are there no comments for my crossover in
    http://www.audioheritage.org/vbullet...=&threadid=283 ?

  2. #2
    Administrator Mr. Widget's Avatar
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    The 2405 diaphragm is a lighter gauge of aluminum than the 2402/075. I believe the impedance is slightly different also. Don't be too concerned about the nameplate rating as all 2405s are the same whether rated 8 or 16 ohm and all 075s are the same also.

    JBL will sell you the two horn parts separately so that you can convert an 075 to a 2405 or vice versa. The magnet structure is of no consequence as both the alnico and ferrite versions are interchangeable.

    If you are considering turning a pair of 075s into 2405s, you might look in the "Marketplace" section as Mike Caldwell has some for sale at a very reasonable price.

    I did notice your schematic, but I must apologize for not taking the time to analyze it.

  3. #3
    Member Dieter's Avatar
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    Thank you Mr. Widget!

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    Hi Dieter, why change the 075/2402 to the 077/2405 tweeter?
    Yes, the dispersion of the 077 is better but then again, more dispersion is not necessarily good either. If you sit a reasonable distance from an 075 and if it is at a reasonable (ear) height and you are not interested in a large 'sweet spot', why bother with the change. After having lived with Quad ESL's with their directional characteristics for many years, I like hearing what is ON the record/CD rather than the changes my room provides. I have often thought of converting my 075 to a 077 but after extensive listening to both have decided, for me, it's just not worth the bother.
    re the system in your picture. I take it that is your se-up. How high is the center of that huge midrange horn? Does it work well in a living room in view that the 'throw' ie smooth response is often intended for larger distances than a typical living room size allows. I note that JBL _always_ uses the small slant plate lens in their older monitors and never the large horn or the diffraction horn many here appear to hold in high esteem. Am I missing something?? Presumably JBL does know best, no?
    - regards

  5. #5
    Member Dieter's Avatar
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    Hi Guenter,
    about the 075/077 it is a question for a friend.
    In my setup i use the 2405.

    The center of the 2360 is about 5' high and angeled to the listening-position.
    I've got this huge horn for less money and i will make the best of it.

    Regards
    Dieter

  6. #6
    Administrator Mr. Widget's Avatar
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    Guenter, you brought up a couple of issues that I find interesting.


    "I have often thought of converting my 075 to a 077 but after extensive listening to both have decided, for me, it's just not worth the bother."

    I prefer the 077/2405 when used above 10KHz as Deiter is doing. I think it has a bit more air and sparkle. When used at lower frequencies as in the L65 Jubal it has a harsh sizzley sound. As far as dispersion goes I feel they are both very directional and must be aimed directly at the sweet spot and be preferably at ear level.

    "I note that JBL _always_ uses the small slant plate lens in their older monitors and never the large horn or the diffraction horn many here appear to hold in high esteem. Am I missing something?? Presumably JBL does know best, no?"

    I think they used the slant plate and 2307-2311 horns for economic and convenience reasons. I am one of those fans of the large diffraction horns and they are a pain to design around. They must stick out through the grill cloth, and they are quite large, and if made in an attractive hardwood as in the Westlakes they are quite pricey. I do think the improvement in sound is worth it though.

    As far as directional vs. wide horizontal dispersion speakers are concerned, there are good arguments for both, and they can both sound great or not so great depending on the room and a host of other factors.

    Widget
    .

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    Mr Widget writes:

    * I prefer the 077/2405 when used above 10KHz as Deiter is doing. I think it has a bit more air and sparkle. When used at lower frequencies as in the L65 Jubal it has a harsh sizzley sound.*
    Essentially the same experience for me. Either set of tweeters were crossed over at about 4kHz and it was a mixed bag with either tweeter and no clear 'better' choice.

    *I am one of those fans of the large diffraction horns and they*
    I know, am severely tempted re those diffracton horns you are having machined from hardwood a la Westlake.

    *a pain to design around. They must stick out through the grill cloth, and they are quite large, and if made in an attractive hardwood as in the Westlakes they are quite pricey. I do think the improvement in sound is worth it though.*
    Indeed, I note though that you do not mention anything about the inherent time delay to either tweeter or bass, part and parcel of such a 'deep' horn. If the xover is at 800 Hz, ie 42 cm, the horn driver is almost a full lambda away from the other drivers. I am assuming the 'short' horn and slant plates with the 2" driver is used by JBL because of the technical advantage of at least minimizing this problem. Now, the question is: Is the time delay at low frequencies indeed a problem? I agree that at high frequencies, the tweeter xover, the problem is not as serious.

    - regards

  8. #8
    Senior Member GordonW's Avatar
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    Agreement here with Guenter and Mr. Widget, with regards to using 2405/077s or 2402/075s with crossovers. IMHO, the lowest one of these sounds good at, is the 7000 Hz crossover point of the JBL N7000 crossover, very frequently used with these.

    Yes, it's quite possible to use them lower, but IMHO, the durability and distortion issues just don't warrant it.

    However, I've used the 2404 (the biradial horn, much bigger mouth) lower with good results, which is understandable, given the bigger horn mouth. These tend to be only power-limited as far as low frequency limit goes... 5000 or 5500 Hz is usually fine, as long as decently steep slope is used.

    Regards,
    Gordon.

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