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Thread: C-1200/1200H bass horn or transmission line

  1. #1
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    C-1200/1200H bass horn or transmission line

    I have 4 of these drivers, brand new never used. Got them on E-bay a number of years ago. They look and test perfect but the rims are badly cracked and dented. The solid seat past the outer perimeter where the gasket goes is still perfect so still usable. The damaged part could either be routed off, or they could be used out of sight. I was thinking I'd like to try my hand at a transmission line project. Thoughts?

    Peter

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    Dang. Amateur speakerdave's Avatar
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    This is just me wondering, but why not use them the way JBL used them?
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    They're Century Gold drivers but as I stated, damaged and don't look so good. In what other configuration were they used?

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    Senior Member pos's Avatar
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    They were used in the 50th anniversary century gold speakers.

    As you can see the rims of the drivers are covered and not meant to be seen, so the dented look might well be normal

    These are supposed to be very good drivers (evolution of the 128H), to be used as direct radiator in bass reflex boxes of around 40 or 50L tuned around 30 or 35Hz.
    You would probably need some 1200Fe to beat them.
    A pair per side would probably be a very good match for large horns like the TH4001 or A290.

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    Senior Member grumpy's Avatar
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    ... except I -think- those gold rims -are- the frame, and very exposed.

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    Quote Originally Posted by grumpy View Post
    ... except I -think- those gold rims -are- the frame, and very exposed.
    That is correct. So?

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    Senior Member pos's Avatar
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    That is strange as the 5" mid also used in the LSR32 does not have integrated gold rims.
    Anyway that is just an aesthetic matter: either add a rim yourself, or mount them from the rear of the enclosure and call it done.

  8. #8
    Dang. Amateur speakerdave's Avatar
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    Quote Originally Posted by pos View Post
    . . . or mount them from the rear of the enclosure and call it done.
    I don't think that's possible with that rim.

    It seems that for some reason there were a number of these that somehow were dinged up. I remember seeing them on the market a few years ago. I have a pair that are not dinged, but the "gold" is flaking off (another case of a poorly prepared surface, I'm guessing), and they are not attractive for that reason. But it looks to me like they cannot be mounted on the back of the baffle just as the many JBL squircle frames cannot. If there is a trim ring on the Century gold, maybe that can be obtained from JBL. Also, possibly the one from the LSR32 can be made to work.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    Quote Originally Posted by speakerdave View Post
    I don't think that's possible with that rim.

    It seems that for some reason there were a number of these that somehow were dinged up. I remember seeing them on the market a few years ago. I have a pair that are not dinged, but the "gold" is flaking off (another case of a poorly prepared surface, I'm guessing), and they are not attractive for that reason. But it looks to me like they cannot be mounted on the back of the baffle just as the many JBL squircle frames cannot. If there is a trim ring on the Century gold, maybe that can be obtained from JBL. Also, possibly the one from the LSR32 can be made to work.
    As you can see in the pic, the rim is integral and also the finished/presented surface. Did you not just state you have a pair? I don't see why you could not work out mounting them from the rear, but that would cause response problems with the baffle. Speakers are mounted with the frame either flush or proud of the baffle for this reason. Are they not?

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    Dang. Amateur speakerdave's Avatar
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    Quote Originally Posted by gasfan View Post
    As you can see in the pic, the rim is integral and also the finished/presented surface. Did you not just state you have a pair? I don't see why you could not work out mounting them from the rear, but that would cause response problems with the baffle. Speakers are mounted with the frame either flush or proud of the baffle for this reason. Are they not?
    I wasn't sure from the photo whether there is a trim ring or not. Mine are in boxes up on a shelf and I have not looked at them for a long time. I wasn't trying to debate about it really; just sharing my experience. You can mount them any way and any where you like.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    Quote Originally Posted by speakerdave View Post
    I wasn't sure from the photo whether there is a trim ring or not. Mine are in boxes up on a shelf and I have not looked at them for a long time. I wasn't trying to debate about it really; just sharing my experience. You can mount them any way and any where you like.
    My only intent is to be accurate. I don't mean to take you to task. I need you guys' help. I have yet to complete my first project. I'm presently deliberating with my cabinet maker on the altered 4345s I'm about to undertake. I love overkill. I want to sandwich 1/2" HDF between 2 layers of 1/2" baltic birch with a 1/16" layer of modified roofing felt between the innermost 2 layers. He tells me this is not doable without a cupping problem. It could be as much as 1/4" on a 5'x5' sheet. Will construction and bracing deal with this issue? On the other hand, 1 and 1/2" laminated baltic birch is no problem. But I want to seriously damp these cabs which are about 2cu.ft. larger than original. You guys' insight and experience is priceless to me here.

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    I have used damping glue from Swedish Swedac with great success. This kind of glue dampens vibrations. When knocking on a wook laminated with this glue the sound is dull.

    You must be able to get the same kind of glue in Canada. Importing from Sweden is serious overkill :-)

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    Quote Originally Posted by gasfan View Post
    My only intent is to be accurate. I don't mean to take you to task. I need you guys' help. I have yet to complete my first project. I'm presently deliberating with my cabinet maker on the altered 4345s I'm about to undertake. I love overkill. I want to sandwich 1/2" HDF between 2 layers of 1/2" baltic birch with a 1/16" layer of modified roofing felt between the innermost 2 layers. He tells me this is not doable without a cupping problem. It could be as much as 1/4" on a 5'x5' sheet. Will construction and bracing deal with this issue? On the other hand, 1 and 1/2" laminated baltic birch is no problem. But I want to seriously damp these cabs which are about 2cu.ft. larger than original. You guys' insight and experience is priceless to me here.
    With the 4345 design the main enclosure is band limited from f3 to 300 hertz. The issues with MDF are above that and normally only come into play when running a sans diy 2 way with a crossover point of 750- 900 hertz

    So attempting to damp reasonance above 300 hertz is a bit pointless.

    The dog box is so small that its naturally rigid anyways.

    Suggest you pick either 1 inch mdf or if affordable birch ply and brace liberally to avoid flexing.

    If you are going for a bigger box dont go over board unless you are making a 20 hertz sub only box.

    10.3 cu ft 3 net Vol @ 27.2 hertz fb is optimum unassisted alignment and will extol all the virtues of the 2245 and then some for use from Fb to 300 hertz

    If you go bigger then yes the box dimensions become a resonance control issue and so does the group delay of the associated tuning for "music" play back.

    The thing to understand with the 2245H is that it will boundary couple more than you will realize and with the added room gain you will have more low end bass lift then you know what to do with.

    I have personally found the above tuning a works very well domestically as it has a gradual fall below 100 hertz but the resulting "in room" response is smooth and extended with a lot of punch but without the bloating some users write about with the 4345.

    The actual factory boxes where perhaps smaller than they need be for marketing purposes and the smaller box tend to lift the 40-60 hertz range on paper which is not what you want domestically Free field or flush mounted this is not an issue but in a domestic room space and placement is always an issue with the 4345. So I tend to get the woofers up off the floor 6 inches if I can. Otherwise you end up resorting to parametric eq cutting the bass back as 2245 will excite all the room modes with its boundary coupling.

    I have a pair of Gold Century woofers too and I was considering using them like below my Tad's like GT did in his much loved ultimate diy home system.

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    Excellent, Ian. Thank you. 10.3 it is! Understanding and applying T/S parameters is a hard lesson to get my head around. Your explanation borne of experience is very generous of you. I've been accumulating components for a few years now but have been afraid to get started. No fault of the Lansing Heritage site. You do have to know what questions to ask. You've been very insightful indeed. As were a couple of others on this site last fall directing me towards a 4-way , 4345 type configuration. I now have a starting point. Where can I get a look at GT's system?

    Peter

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