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Thread: Mid range driver advice needed

  1. #16
    Administrator Mr. Widget's Avatar
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    This picture really puts it into perspective!


    Widget
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    Attached Images Attached Images  

  2. #17
    Senior Member richluvsound's Avatar
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    TD 4003

    Widget ,

    that looks like a tad profile . Cast me two of them ,will you

    Rich

  3. #18
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    What drivers do you in the bass horn
    5 Altec 515-16g per channel.The aim here was fast midbass rather than sheer extension.The system is flat to 23HZ ,3db down by 21Hz and more than 10 down by 19 Hz.Probably more due to horn cut-off rather than drivers

    how do you deal with the time alignment
    I assume you mean in the bass.Short answer is I don't.The crossover there is 24db/oct at 180 Hz.The 6ms delay here is not audible to either myself or any of my fellow testers.I personally can hear a 8-9 ms delay at that f but not shorter.Conversely,higher up the other horns are aligned to within a mm as it is painfully obvious at higher fs

    Also is that a Machine hat chamfers the edges of CD's in one of your pics
    No .

  4. #19
    Dang. Amateur speakerdave's Avatar
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    Quote Originally Posted by mafuta View Post
    . . . . higher up the other horns are aligned to within a mm as it is painfully obvious at higher fs . . . .
    mm really? or ms?

    David

  5. #20
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    Thanks to all of those who gave advice and those anonymous members who supplied more than advice.

    The final assembly of drivers are JBL 2440. JBL 2440 with 2450 dia,TAD 4003,Goto SG370 and JBL 2435(aquaplassed).So far the 2435 has been the firm favourite but the TADs arrived today and I may have a new permanent resident in the system

  6. #21
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    Quote Originally Posted by stephane RAME View Post
    I don't have any of the other gear, but I have many of those same vacuum tubes

  7. #22
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    Horn Information

    Hi. My name is Peter. I am in Perth in Western Australia. I have long been interested in large bass horn systems. My current system is a large electrostatic based system. - Soundlab.

    Would you be willing to share some information about your amazing bass system?
    I have seen the site for Marcel Roggero but cannot work out how to contact him.

    I intend to build a large dedicated listening room and would consider building bass horns similar to yours or some other design.

    Any help gratefully appreciated.
    Peter

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  9. #24
    Senior Member Odd's Avatar
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  10. #25
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    Quote Originally Posted by PerthPete View Post
    Hi. My name is Peter. I am in Perth in Western Australia. I have long been interested in large bass horn systems. My current system is a large electrostatic based system. - Soundlab.

    Would you be willing to share some information about your amazing bass system?
    I have seen the site for Marcel Roggero but cannot work out how to contact him.

    I intend to build a large dedicated listening room and would consider building bass horns similar to yours or some other design.

    Any help gratefully appreciated.
    Peter
    This is my second attempt at a response as the first disappeared on completion.
    Basically such a bass horn can only be designed for you by yourself using your own philosophies and preferences. As the perfect horn will have infinite length and size, every horn design has to be a compromise. Only you can decide where and how you are going to compromise.

    I can however tell you what I have done: In building a horn you have to decide on length size of mouth and throat, flare and cut-off. This is the total opposite sequence that one would use in say a midrange horn.

    Length: 3 Issues here: Firstly, available length. Secondly phase issues. If one is willing to use digital delay this is not an issue. In my system however I use mainly Mark Levinson and Studer A80 analogue recorders as well as a Thorens Reference turntable. I am simply not willing to digitise their output for signal manipulation. I therefore cannot have too long a horn. I spent months with an experimental set-up do decide what is acceptable to me. I finally concluded that I can hear a difference at 2.8 meter between bass and mid drivers at the 225Hz crossover. As the midbass and midhorns have their drivers some 700mm into the bass horn I decided on a depth of 3m. Taking the available mouth space and size of throat I came down on a21Hz horn. The third issue is how long must a horn be to function as a true horn at a certain frequency. Again this must be juggled against 1 and 2.From my measurement I am happy that this one functions as a true horn into the low to mid 20s
    Throat: I decided against the use of a front chamber so have a driver to throat surface of 1:1. As the roof of the horn slopes at a 6 degree angle towards the back (to avoid standing waves) I could accommodate 5 15 inch drivers.
    Flare. Before embarking on this I built several very large horns from wood. The Tractrix horn performed very poorly in the bass so I decided on a Hyperbolic- Exponential horn with a flare coefficient of 0.707. This mainly to accommodate all the above parameters.
    All of the above could only work if the horn was a 21Hz design. Please bear in mind that the horn has to be designed around the chosen drivers. In my case I used Altec 515 16Gs. They do not go as deep as other drivers but I feel can be used higher and has an appropriate efficiency. I have no proof for this but I always felt a speaker system would “track” input better if all parts have similar sensitivity I was aiming for 110db/W here. I believe M Rogerro used 515Bs in his system.
    Rear loading: In order to extend the horn as low as possible I used reactance annulling, giving a rather small sealed chamber behind the drivers. I believe Monsieur Rogerro use a more complex tapering tunnel set up that finally exists to outside.
    Was this done correctly? I don’t know. Should I have done it differently? Again I do not know. It is now almost 7 years since it was completed so Baranek’s law have had ample time to reverse but I am still happy. The tweeters have changed 3 times, 5 different mid drivers and 2 midhorns have been used but not a single thing in either bass or midbass transducers or horns.

  11. #26
    Senior Member Lee in Montreal's Avatar
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    Currently running knock-offs of JBL 4520 (twin 15" per cabinet) and currently designing an improved version that goes lower (27Hz) with a longer path, bigger mouth and twin 18".

    As was previously mentionned, a bass horn is all about compromise. Mostly size compromise. If you are willing to go up to a 5 or 6ft tall cabinet, then you can get some positively surprising results.

  12. #27
    Senior Member Eaulive's Avatar
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    Quote Originally Posted by Lee in Montreal View Post
    Currently running knock-offs of JBL 4520 (twin 15" per cabinet) and currently designing an improved version that goes lower (27Hz) with a longer path, bigger mouth and twin 18".

    As was previously mentionned, a bass horn is all about compromise. Mostly size compromise. If you are willing to go up to a 5 or 6ft tall cabinet, then you can get some positively surprising results.
    So Lee, did you learn to like them? it's been more than a month, give me a report. Mine are ready yet.

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