what current production tweeter(s) works well with a 1st order crossover?

[Alex S]

I'm looking into replacing the old Focal TC120K (kevlar) tweeters on my Impulse Lali (UK spkr company now defunct). The form surrounds have deteriorated badly.

The crossover has 3.3uF and 2.2R in series with a 15R across the tweeter. I would, of course, have to change the values to accomodate a different tweeter. But I hate to (and don't know how anyway) to start designing a higher order crossover.

Focal has stopped selling drivers, and I'd rather not use it's last released TD120 TD5 which has been sitting on the shelves for some time, and whose form surrounds may have started deteriorating in the box. In any case, the Lali's TC120Ks likely have been tweaked by Impulse (further damped) to work with the simple crossover, and there is no reason to believe the TC120 TD5 is a simple drop-in.

Any ideas? Thanks in advance!

[C37]

Hi Alex S

You might want to check this tweeter that is featured in Hobby Hifi this month: http://www.volkslautsprecher.com/html/mh1.html It's a drop in replacement of the TC120 with lower FS because it has a rear chamber , a sanwich voice coil for lower distortion, etc etc and has exactly the same looks ( the pic in their web page is horrible, it looks much better in the magazine). Might just be the ticket if you don't want to rework the front of your impulses to adapt different units.
regards

Tom

[C37]

better pic here: http://www.kir-hifi-audio.de/lautspr...jpg/ariana.jpg

[Alex S]

Tom,
thank you for you reply. I'll will add the Hochtontreiber MH1 to my options. By the way, your link was not directly clickable because of the extra "." at the end. For the convenience of others, here the link again:
http://www.volkslautsprecher.com/html/mh1.html

Also, earlier, I had found another third-party direct replacement for the TC120 from Clofis in Netherlands:
Celeritas TD130R

But all these direct replacements use foam surrounds. If possible, I would like to avoid foam surrounds. I stay in a hot and humid location, and, with foam surrounds, I may need to repeat this exercise every 3-4 years.

[C37]

Hi again,
I suppose there are many options available, seas tweeters come to mind, Dynaudio and scanspeak too but i am no expert so let some who has actually tried it advise you... The Lali's use a seas bass-mid driver. BTW, the tweeter they used seems to be TC 90 K not the 120. If you don't already know it, http://www.acoustica.org.uk/impulse/h6mods.html have some info on modding the lali's and the H6 which shared common drivers .


Zaph audio made a tweeter group test here: http://www.zaphaudio.com/tweetermishmash/

Have fun
Tom

[Alex S]

Tom,
thanks for the acoustica h6mods link. The series crossover connection looks very promising and I'll want to try it out in the future.

The original tweeter on the Impulse Lali is almost certainly the TC120K. The face plate is 120x120mm, not the 92x92mm of the TC90. And the magnet is humongous (for a tweeter).

From what little I know so far by looking at the specs sheets, the SEAS tweeters (e.g. the 27TDFC) look most suitable. The Fs is suitably low at 550Hz, and the impedence peak is also low and smooth. But the linear coil travel is only 0.5mm p-p; more would be better of course.

[m@]

the Vifa XT ring radiator has a lowish ~ 500 resonance. any other issues when using a 6dB xover?

[BigSmooth]

I wouldn't suggest the Vifa tweeter for your application. While the fs is low, harmonic distortion is high at frequencies below 2000hz. You would have to go with a higher order crossover on this one. Still a good tweeter.

My suggestion would be the Accuton C23-6 assuming you have some cash to spend. I have a pair w/ 1st order crossovers and they work great.

[Alex S]

hehe, embarrassed to say, I did try my luck earlier with the Vifa XT25. And no, it didn't work well, just as Big Smooth said in the preceding note.

XT25 fitted on 120x120mm face plate:


BigSmooth,
yes, the Accuton C23-6 was another on my list, and your note validates it. The impedence plot looks very good. The sensitivity at 89.5dB is just a bit lower than I like (the Impulse Lali is 91dB while the Focal TC120K itself is 93.5dB), but I can live with it. I still need to think more about the money part though

One question - beneath the grill can you tell if the Accuton's suspension is foam or rubber? Thanks.

[Andy G]

Basically ANY of the Seas tweeters with low Fs (around 500) will work very nicely with low order x-os !!