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Old 7th November 2004, 11:02 AM   #1
dbargna is offline dbargna  United Kingdom
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Default re engineer Bookshelve - is this possible

Hi

I'm pretty much new to speaker design and would like to know if the following is possible,

I have recently aquired a pair of ALR Jordan Entry 3M bookshelves without the woofers. what I would like to do is make a new cabinet and produce a pair transmission line speaker. But there are couple of things in my way... I know ****** all about crossovers - so I would like to use the existing crossover (it's a Linkwitz Reiley) and I am missing a woofer so I need to replace it. All I know about the woofer is its a 160mm LF metal Cone.

is it possible what I want to achieve and could anyone recommend a woofer from the specs below? one that is cheap would be good, we are expecting our first child soon and money is tight!!

thanks


here are the specs for the Bookshelves

System : 2-way bass reflex
Frequency Response : 45 - 28.000 Hz
Nominal Power Handling: 80 watts
Musical Power Handling: 120 watts
Impedance : 6 ohms
Suggest Amp Power : 25 watts - 150 watts
Sensitivity : 90 dB
Crossover Frequency : 2.800 Hz
Filter Slope : 24 dB
Weight: 6,7 kg
Dimensions (WxHxD): 203 x 350 x 290 mm1
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Old 7th November 2004, 12:17 PM   #2
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By far the fastest way is to buy one other Jordan woofer. Not cheap, but otherwise you need to buy 2 new woofers, plus completely redesign the sytem including xovers. The Jordan drivers are quite specificf and I don't think there exists a drop-in replacement for them.

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Old 7th November 2004, 01:16 PM   #3
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Quote:
I have recently aquired a pair of ALR Jordan Entry 3M bookshelves without the woofers. what I would like to do is make a new cabinet and produce a pair transmission line speaker.
Hi dbargna,

So if I understand this right, as You want to build new enclosures anyway, all You have are the tweeters & crossovers.

As You need new woofer/mid drivers which very likely would require a complete redesign of the crossover also (IMO it`s unlikely that You find something which could be a dropin replacement), all what is virtually left is a pair of tweeters.


If You can`t find the original bass/mid drivers for this design and taken into account that You don`t have experience in speaker design my advice would really be: don`t mess with this any longer.

Instead, choose a new but complete design which You think is suitable, affordable and feasible for You.
I bet that finally this would be cheaper, faster and better than this what You´re intending to do.


IMO, it just doesn`t make much sense trying to design complete speakers around a pair of tweeters only just because You have them.
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Old 7th November 2004, 01:48 PM   #4
dbargna is offline dbargna  United Kingdom
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ok.

would it be possible then to find a woofer with similar specs to replace the missing one. THen I shouldnt have to rebuild the Xover. This should be possible in theory. But the thing is I dont know how to get the woofers details.


thanks
David
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Old 7th November 2004, 02:41 PM   #5
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Quote:
would it be possible then to find a woofer with similar specs to replace the missing one. THen I shouldnt have to rebuild the Xover. This should be possible in theory. But the thing is I dont know how to get the woofers details.
David,

I fear the "specs" You have for that driver are pretty useless except maybe the sensivity spec.

Take a look on how a real spec.-sheet of a driver looks like. Important specs to know would be at least fs and Qts. An impedance and a frequency plot would be also very useful.
Without this it`s really just guessing.

Of course You could substitude the original driver with something what appears to be similar but I guess the result would be rather unpredictable.

What about keeping the enclosures, selling the tweeters and find a complete project (which shouldn`t be too troublesome - there are virtually hundrets of 2-way bookshelf speaker designs on the net) that would fit into it?
To me this appears much easier.
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Old 7th November 2004, 03:03 PM   #6
dbargna is offline dbargna  United Kingdom
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Quote:
Originally posted by cocolino

Hi dbargna,

So if I understand this right, as You want to build new enclosures anyway, all You have are the tweeters & crossovers.

As You need new woofer/mid drivers which very likely would require a complete redesign of the crossover also (IMO it`s unlikely that You find something which could be a dropin replacement), all what is virtually left is a pair of tweeters.


If You can`t find the original bass/mid drivers for this design and taken into account that You don`t have experience in speaker design my advice would really be: don`t mess with this any longer.

Instead, choose a new but complete design which You think is suitable, affordable and feasible for You.
I bet that finally this would be cheaper, faster and better than this what You´re intending to do.


IMO, it just doesn`t make much sense trying to design complete speakers around a pair of tweeters only just because You have them.

ok then thanks for the info. I'll go back to the Klang & Ton CT 197
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