Which tweeter (TDFC or RS28)?

[Mazeroth]

I'm in the process of designing two speakers. One is a dipole with dual RS315HFs in an H-Frame, along with a single RS225 up top, similar to the Orion. The other speaker is an MTM with dual RS150s. I'm stuck on which tweeter to use and have narrowed my choices down to, but not limited to, the Seas TDFC and the Dayton RS28. I like the Seas because it's a known performer and is relatively inexpensive for what you get, but I could spring for the more expensive RS28, if you guys feel it's worth it?

Basically I'm looking for pros/cons for each tweeter and which one you would use if you were in my shoes?

Thanks. :T

[Davey]

Personally, I would go with the Seas tweeter.

I have four RS28 tweeters and every one of them measures differently with impedance/SPL/distortion testing. I know there was a lot of variability with these units early on so maybe some current ones would be fine.

Davey.

[Amphiprion]

My top three pics for my current Seas L15 based two-way were the 27TDFC, 27TBFCG, and the RS28. I went with the 27TBFCG but I haven't measured anything about it - I should have Praxis set up in 2-3 weeks at this rate. From the graphs at Zaph Audio, the 27TBFCG looks identical to the 27TDFC but with an ultrasonic resonance due to the metal dome.

But yeah, I think any of those would be great choices. The dark horse candidate would be the new Peerless HDS tweeter, which looks great on paper but I haven't heard any user reports yet.

[Mazeroth]

Thanks for the opinions!

I would have considered the 27TBFCG but I can't, for the life of me, get over that ugly hexagrid they use.

With the TDFC, how low can I cross that puppy? I'd like to keep the cost of the MTM to a minimal in the crossover department as I'll probably be building 2-3 sets of 5 speakers out of these for family members. They're not audiophiles by any means, and will just use them for watching movies. This will also be my first attempt at designing my own passive crossover. I purchased Soundeasy last weekend and will be devoting the next couple of weeks to learning it, to make sure I build something that works. With that, are there any recommended crossover frequencies/slopes I should try out to begin with? Just looking for a starting point.

Thanks.

[Amphiprion]

Which speaker? The RS225 one or the RS150 one? My recommended starting cross points and slopes could be very different for them, I haven't looked at the data in a while.

[Mazeroth]

The RS150s, in an MTM.

[Amphiprion]

That should be a pretty easy XO. As far as getting flat frequency response, that shouldn't be a big deal at all. I would start around 2k LR-4 and go from there. Make sure to simulate your baffle layout and superimpose that with the tweeter's anechoic response, you can save yourself some trouble with some big dips/peaking you might see otherwise in the tweeter response. Notch anything that looks troublesome in the woofer if it shows up at high enough amplitude in the roll-off response. Honestly it shouldn't be that hard.

Now crossing that 225 over is another matter entirely....

[cjd]

Hmm...

either for the RS150's. Cross at 1.8kHz 4th order. I've done versions for both tweeters and the RS150 in MTM.

RS225, unless we know it's been resolved, the low end on the RS28A can be up to the specific tweeter as to how much luck you'd have crossing to the RS225 where it needs to be crossed (~1.2kHz is probably the top, 8th order - C-E recommended) so in this case I would go with the Seas (which can cross that low also, and has a bit more consistency in doing so on its record).

C

[joecarrow]

Yes, crossing the RS225 to any tweeter will take special caution. The 8" woofer used in the Orion has a couple of concentrated breakup resonances, more easily addressed with a notch filter than the high frequency garbage from the RS225 breakup. The RS225 also starts to run into stored energy problems at a lower frequency.

I think that as long as your H frame isn't too deep, you should be able to cross your RS315s plenty high enough to get by with an RS180, or pair of RS150's at decent SPL. The driver itself has been said to be quite usable up past 300 hz.

Another note- why not go for the unshielded 4 ohm version of the midwoofer? I can't confirm, but my guess is that they're more open in the rear.

[mazurek]

You can have my 27tdfc tweeters I swapped out, that I have relegated to practive tweeters, to test with your terrific new soundeasy setup.

[BobEllis]

With the RS225 I think you'll need to go with a Millennium to allow crossing over down between 1,000 and 1,200 Hz, Jon Marsh hard roll off style. You might be able to tame the RS225 with a big notch, and use a 4th order filter a bit higher.

Maybe a TDFC in a waveguide would allow reasonable levels, but it would have to be longer than the one Zaph used to load the tweeter down to 1 kHz. I'm very slowly working this idea - I've got to get my lathe out of storage to turn the waveguides.

[Amphiprion]

What about the Neo3 PDR fo the RS225?

[cjd]

I'll second the suggestion to consider a pair of RS180's with either the Seas or the Dayton tweeter. The RS315's can definitely cross high enough to cover.

C

[BobEllis]

Hmm - Hadn't thought about the NEO3 PDR much. Distortion looks good (better than 27TDFC) down low in Zaph's tests, but the frequency response starts rolling off up at 2K. It would take lots of EQ somewhere to extend the response down to where you need it to be to avoid the RS225's breakup modes. Looks great for use with an RS180, though.

[Amphiprion]

Depending on how the baffle diffraction affects the tweeter response, you might just get a boost in the 1-2k range to help keep the Neo3's response up below 2k. That would take a little playing around with the baffle diffraction simulator and combining it with the anechoic results of the Neo3 to be sure though. I think PE has the anechoic results of the Neo3 posted, but I'm not sure.

That said, I agree the RS180 would be a much easier choice to work with. I think the 225 is more intended as a woofer in a three-way than a midwoofer that's to be crossed to a tweeter.