Help with tweeter swap on Microberoject...

[jmillerdoc]

Hi,
I am planning to build pair of speakers for my brother in law this weekend and wanted to use what I had on hand.

I have a pair of the Dayton RS125-8 and a pair of Vifa XT25sc50-4 ring radiators.

I found this project, the Microbes, here:

Microbe

The tweeter used is the Tang Band T25-1166s, a 4 ohm neo driver that appears to be very similar on paper to the Vifa XT25sc50-40.

Basically I wanted to substitute the Vifa for the TB and wanted to know if I would be able to do so without much modification to the XO. Can someone offer some suggestions or advice on doing this? At first glance it appears the Vifa is a tad more sensitive (91.6 vs 90) but beyond that Qts is very similar (0.9 vs 0.87)....maybe a little more padding of the tweeter is all that is needed?

Thanks for your input in advance!
Jeff

[DrDyna]

I'm by no means an expert, as I just recently started trying to hone my skills designing proper crossovers, but it looks to me like it wouldn't be too much of an issue if their fs is similar, otherwise you may have to tweak with the parallel resistor on the tweeter.

[jmillerdoc]

Fs is very similar, one is 837hz (Vifa) and the other about 920hz (TB).....since the vifa will reach a little lower I would think it would be fine at this XO point (somewhere around 3000hz as I recall)...

[DrDyna]

It's worth a shot, anyway. In any case, the changes are going to be relatively small, the resistors will change slightly and the cap might change a little as well.

If you have speaker workshop, the designer of the microbe has posted the workshop file on the microbe site, you might want to snag it. I looked around but I couldn't find FRD/ZMA files for your new tweeter, perhaps someone here has it.

If they do, snag the workshop file, snag the FRD for the new tweeter and stick it in there instead of his existing tweeter and see what the sim looks like.

Edit: I wonder if that tweeter is the same as my TG30-04 but with a different face.

[DrDyna]

I tinkered with the design provided on the microbe page with the frd/zma I have for the XT25 I've got, which is slightly different from yours, so your mileage may vary, but this is what I got.

I'm still new at this, so if anyone wants to audit this...feel free!

[wolf_teeth]

I'm not sure where it's posted, but I bet it's on Roman's site....
'evilskillit' on PE's board built a pair of them.

Later,
Wolf

[jmillerdoc]

On your schematic above you have the 3.3 and 6.8 caps in series...are you sure this is correct?

[DrDyna]

Originally Posted by jmillerdoc

On your schematic above you have the 3.3 and 6.8 caps in series...are you sure this is correct?

That's kinda why I was hoping someone would look it over. When I opened the project file, I took the parallel coil away from the tweeter and re-ran the simulation and it appeared to be flat.

Technically, there should be another coil across the tweeter to make it a 2nd order crossover.

You're right, it's probably incorrect, but she looks flat, right? It may be best if you grab the project file and fiddle with the values with more care, as I'm not even sure that the tweeter that I imported into the project (XT25TG30) is identical to yours.

Edit: Again with less deleting

[jmillerdoc]

No the XT25TG30 is an entirely different beast....mine is neodymium the TG30 is not....
But thanks anyway, I see what you're talking about.