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JPW Tweeter upgrade ?

R

Rosie

pfm Member
Hi everybody ,

I'm a complete dunce when it comes to understanding electronics so I need to know if I can or should do the following .

I've got a pair of JPW Sonatas and I know there are a few old threads about tweeking and servicing them here on Pink-Fish , which I have read .
I would quite like to try replacing the tweeter with something a little smother , howerer just to contradict myself the one on there at the moment was all the rage back in the 80's and was used on the Moudant Short MS10 , a speaker I have fond memorys of .

My plan is remove the Audax TW6X9A 8ohm tweeter and replace with a pair of Audax TM025F15 8ohm tweeters . Can I do this without making alterations to the crossover ? Or am I a dweb for ever thinking about it .

On the plus side the TM025F15 will need new screw holes but will fit the tweeter cut out and if I decide to return to the original TW6X9A then the new srew holes will be covered by the slightly larger original tweeter . Both will be surface mounted so the 'woodwork ' is a walk in the park .
 
Personally, i think JPW did a great job with selecting/matching the drivers.

If you do decide to change out the tweeter to TM025F15, the existing 4.7Ohm resistor will have to be replaced, or paralleled with another, in order to bring the level (94dB @ 2.83V @ 1m) down to very near that of the existing TW6C9A (91.3dB @ 2.83V @ 1m).

The existing 3.3uF capacitor will be fine, as you'll want to continue to take advantage of the bass/mid drivers ability to go high, plus keep the crossover the same simple 1st order 6dB/octave on both low and high pass. IOWs, dramatically lowering the crossover frequency would require going 2nd order on the high pass to the tweeter in order to prevent it from being overdriven/overheated down low. The only change that may make that level of crossover rework worthwhile would be going for something like the 25mm Elac metal dome, as employed in Sonata Plus. This is more or less what I was musing about in the thread entitled 'JPW Sonata tweaking...', post #9.

FWIW, I don't think TM025F15 will sound any better, even with the level well matched. Despite it being a cheap unit, the TW6C9A behaves very well at >=5kHz. Also, the off-axis response of the smaller unit is superior.

Perhaps, a couple of fresh 3.3uF poly caps would be a good start?

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Hello Craig ,

First off thanks for taking the time and trouble to answer . Really appreciate it .
We all acquire little Hi-Fi prejudices over the years a preference for direct dive over belt drive for example . For me it's sealed box speakers over reflex ports and to a lesser extent a preference for speakers that have tweeters with wave guides .
Having read your reply I'm going to stick with what I have , which is a fantastic speaker in first class condition that cost me £15 !
However I will go for new 3.3 uF poly caps and thanks for the photo , where I am with electronics frankly a picture is worth a thousand words . So I'll drop a line to Falcon acoustics and order a couple .

Cheers Martin
 
Hi Martin
I'd totally agree - I'd just stick with the original unit and upgrade the crossover.
I had some success with some basic damping of the cabinet walls with bitumin sheets, and the driver chassis. I also played with the fill level of the stuffing (quite a bit more was better).

I too MUCH prefer a sealed box... :)
 
another one for sealed boxes. I'm building a 'speaker with two Sonata's per side, with a Fountek real ribbon tweeter. May also keep the original tweeters or swap them (not in or out, just swap) with Peerless (Vifa) XT25SC90-04 1" Dual Ring Tweeters which I have.

The Sonatas do sound very good, I have been using them with very cheap class D amplifiers, and they sound better than £1800 worth of amplifier/speakers I usually listen with.

I'll be doing some testing of the outside of the boxes (with a view to damping), and try different stuffing (Alpaca and sheep's wool, mineral wool etc.) Lastly, I am going to use a KEF paper coned (SP1139) 8" bass units, to match the Sonata paper cones. The Sonata drive units (made by Elac) look exactly the same as the KEF units, but smaller. Did Elac make drive units for KEF?
 
Those who like sealed loudspeakers with wave-guided tweeters should take a look at the Ergo E-IX. Stefan (orangeart) is offering a group buy for PFMers in the DIY room.
 
If you decide to swap the electrolytics for film capacitors you will need to add some series resistance to compensate for the lower ESR of the film caps.
 
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