Seas CA21RE (H397)

[Arctophile]

Hello again,


After reading so much I've made myself cross-eyed, I've come to the conclusion that nothing I do with my xover or new tweeters is going to fix the biggest problem with my dipoles - ie the vifas.

Looking at local sources has thrown up just one real possibility for a sub-$100 replacement: the Seas CA21RE.

I've read on here (and noticed on the published curves) that the Seas L-series 8-inchers tend to die away even lower than 1kHz and that the latest CA22RNX has an obvious mode at 600Hz which doesn't bode well.

Now I'm looking at the plot for the CA21RE and I was wondering if someone more experienced can tell me whether it looks suitable:



I like the sound of its lower moving mass (22g vs ~30 for my Vifas) & higher Qts (0.48 vs 0.27), but am a bit concerned by its Xmax deficit (3mm vs 6).

What say ye?

TIA,

//Adam F

PS Sorry if this has been discussed, I tried every search I could think of for this particular driver.

[JonMarsh]

First, look at the impedance curve. (keeping in mind that it's inverted from the normal format here). There's a non-linear bobble/hump between 600 and 800 that indicates mechanical discontinuities- i.e., energy storage. A very common shortcoming for 8" midwoofers. I think you're also correct in that a 3 mm Xmax isn't very promising, especially not for a dipole application.

However, in spite of my misgivings, it might work pretty fair at moderate drive levels. How low are you talking about taking it? The CA21RE Fs is fairly high.

I'd feel more comfortable working with an L18 myself, or two RS180's for about the same money. Crossover takes a bit more care, but... BTW, you can do a HiVi M8a for about the same money, too. It's just a personal thing, I try to avoid using drivers in their first cone mode regions, even when it's not a peak. I like pistonic... (they're probably put that on my grave marker!)

[Arctophile]

Drat, I was hoping the impedance glitch might have been a non-issue since the FR curve at that point still looks good. I guess it would look different if they moved the mic a whole lot closer

I currently cross to a sub at 100Hz, so Fs of 31Hz shouldn't be a prob.

I'd definitely get some M8as or Daytons if I could source them here in Oz, but shipping from the states would cost me more than the 4 drivers themselves! As for peerless XLS or SS, we're talking over A$1000 for four 8-inchers - and W22s closer to 2 Gs!


//Adam F

[Arctophile]

Hmmm, how about this curve?




Am I seeing things or is there still a little blip at about 1k?

The main problem with this one (Vifa M21WJ) seems to be the Qts of 0.24.
HMM might be affordable AND available though, which would be a big plus.


//Adam F

[Arctophile]

Whaddya know...turns out the Aussie distributor doesn't stock that model. Of course, silly me.

What they do have which intrigues me is the M21WG-19-08, apparently a 1992 model!

Check out the specs:

Pole vent;
90dB Sensitivity;
MMs of just 16.6g;
Qts of 0.51



Sounds like this puppy's built for midrange.

A$100 sounds a bit steep for such an old design to me, but do you think it might be a good choice?

//Adam F

[TacoD]

The impedance curve also shows some cone modes @ 700 & 1000 Hz. I would not buy these drivers for $100, that's a lot of money for such an old unit. Good luck with your search.

http://www.wagner.net.au/pae/Data/Vifa/M21WG-19-08.pdf