1970's TL remake help

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I agree with Linesource and System 7 regarding the mid. Keep it 5". It is not so much a loudness issue but small drivers tend to sound constricted and undynamic. when crossed over too low. I would probably look for a Seas MCA15. A good alternative may be the poly SB15MFC. I had some experience with the old KEF B139. You don't want to take that driver any higher than 350-400 Hz. There are some large breakup modes not too far above that.
 
Hi All,
Been too busy to post, but here is an update with photos.
I have taken on board your comments and decided to keep it simple, I am going to use the B139 and B110 and use the Vifa tweeter as the cut out is similar on the existing baffle.
Mini DSP for bass and mids. The reason I'm ditching the existing crossovers is that they were never designed for these cabinets, they are Cambridge Audio R50 4 way.

Unless the crossovers or any of the drivers are trashed, I'd be inclined to keep as close to stock as possible, and if you want to flush the baffle, simply add additional batten /spacers, refurbish the baffle with a skim coat of bondo filler and re-paint, and maybe a new grille?
Cutting an all new front baffle by hand will be rather a lot of work - particularly for the B139.

So far I have repaired the baffles, loads of filler, epoxy and sanding!
They are solid and the drivers fit flush and airtight.
I have made spacers to make the baffles flush with the cabinet front edges and cross braces really tight, they make a surprising difference to the rigidity of the cabinets.
Sprayed the baffles, no photos yet.....

Just wiring up the drivers and getting ready to listen, but can you suggest a few starting points please.
Crossover ideas / frequencies for the B139 and B110 using mini DSP;
Crossover for the Vifa D25AG-05-06, Can I use just a cap? Any Ideas for a starting value?

My plan is to start without stuffing the cab or mid enclosure, measure with REW to get started and report back;
Please do suggest any thought on how to proceed.

Many thanks
Ian
 

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frugal-phile™
Joined 2001
Paid Member
Crossover ideas / frequencies for the B139 and B110 using mini DSP;
Crossover for the Vifa D25AG-05-06, Can I use just a cap? Any Ideas for a starting value?

For the B110/B139 somewhere between 250 & 300 hz. I have found the TLS80 to hav ebaffle step starting at about 220Hz (so 200 Hz XO starting point) but these are narrower to higher will be needed. B139 has nasty resonances near 1kHz so you want them to be way down by then.

The B110 bextrene has some ugly stuff up high so it will likely need a low pass. I don’t know how low the VIFA can be taken, but i’d suggest 2.5-3k as a starting point. That low you probably can’t get away with 1st order.

dave
 
Thank you Dave, just what I was looking for.

The B110 bextrene has some ugly stuff up high so it will likely need a low pass. I don’t know how low the VIFA can be taken, but i’d suggest 2.5-3k as a starting point. That low you probably can’t get away with 1st order.

What frequency should I set the low pass for the B110?

Here are the Vifa specs;
Nominal impedance [ohm] 6
Voice coil resistance [ohm] 4.6
Nominal power [W] 100
Short term max power [W] -
Long term max power [W] -
Operating power [W] 4
Sensitivity [dB] 91
Frequency range [kHz] 2.5-35
Free air resonance [Hz] 1500
Voice coil diameter [mm] 25
Voice coil height [mm] 1.6
Air gap height [mm] 2
Voice coil inductance [mH] -
Eff. diaphragm Area [cm²] 7.1
Moving mass [g] 0.3
Magnet weight [g]/[oz] 240/8.5
Force factor [Bl] 3.5
VAS [l] -
Qms -
Qes -
Qts -

I have some 10uF caps on hand, If I calculate correctly, will give a crossover frequency of 2500Hz, is that right?
Thanks
Ian
 
frugal-phile™
Joined 2001
Paid Member
I gave up on dome tweeters a long time ago, and have no experience designing XOs for them. The only spec that really drives the XO point would be the Fs + the response curve. I’d guess one might be pushing them at 3k 2nd order.

Myself, i’d use an FF85wk or Alpair 5.2/6.2 or even 7.3 to replace the B110 and not use a tweeter at all.

dave
 
Thanks Dave, I need to work with what I have if possible.
I have these inductors available;
0.25mH x 4
0.6mh x 2
1.5mH x 2
3.4mH x 2
6mH x 2
playing with a few online calculator, I came to this;
3rd Order (18 dB per Octave)
2100Hz, 6 Ohm tweeter
C1=8.42 µF
C2=25.26 µF
L1=0.34 mH I have already;
or
2900Hz
C1=6.1 µF
C2=18.29 µF
L1=0.25 mH I have already
I think I will start with the 2900Hz, does this sound reasonable?

Should be able to make up cap values.
Time to warm up the iron!
 
Hi All,
Had a few issues getting them up and running.
Still need to spray the inside of theTL port as you can see, pleased with the baffle mod.

I setup the basic crossovers on the minidsp and tweeter, used the TC9's to check the amp outputs were putting out the right frequencies so that nothing was blown.
Turns out one of the Tweeter was faulty, I managed to re solder the fine wires that had broken, it worked!

My Initial observation is that the tweeter output will need padding down a bit.

So I'm ready to break out the UMIK and REW.
Some suggestions on what and how to measure would be useful?

Thanks
Ian
 

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