Best 3/4" tweeter options (small flange required!)

[fjhuerta]

After reading... and reading... about MTM's and their crossover requirements, I've decided that I need the closest CTC spacing possible. And using a 1" tweeter isn't helping me much.

Since I'm using the W4's now, the upper frequency response is not a problem anymore. So a good option may be using a 3/4" tweeter with the smallest mounting flange possible.

I have the following options...

1) Vifa D26 (I believe this is a favorite here, and the price is unbeatable).
2) SEAS 27TAFNC (I like this one, but distortion levels are higher than the D26)
3) Vifa XT25 (again - this would look great on an MTM, but distortion levels are higher).

I suppose the only "real" choice I have is the D26 - is there any other small 3/4" tweeter to consider besides this one?

[ahaik]

You could trim the tweeters face plate.

[Curt C]

What woofers are you using? Is your design intended to be used vertically or horizontally? Excuse me if you've explained this before an I missed it...

C

[jkrutke]

I don't think I'd ever use "best" and "3/4 inch tweeter" in the same sentence, but the real question is how low do you need it to go.

If you could live with 3kHz LR4, the recent version of Parts Express ND20FB-4 could work for you, and only set you back $6 too. The response curve is respectably smooth. I suspect this is the ferrofluid version of the earlier ND20TB I tested.



But otherwise, yeah the D26NC55 is pretty hard to beat if you need a small flange. I've never tested a Scan Speak 6000 or any of the "better" small Morels, so I can't comment on that.

[fjhuerta]

ahaik, trimming the faceplate of, say, an RS28 will not make it any smaller... the magnet is the real problem here, I believe.

Curt, the design uses the RS225's as outer woofers, the W4-1337s as midranges and (so far) an RS28 tweeter, in a WMTMW format. I'm trying to minimise CTC space, and the RS28 is a bit too big now that I switched from RS150s to the W4s (since the W4s don't have any issues playing higher than 1.8 KHz).

John, I'd definitely go for the D26, but I'm worried about future availability (I've already had a problem using a SEAS driver which I blew, just when I finished the crossover design. Out of stock - I had two switch to a different driver model and make a new crossover design). I know you don't generally like 3/4" tweeters, but I thought of them as a solution to minimise vertical distance between the mids in my design.

I'd suppose the 27TAFNC would be my choice (somehow, I feel the ND20FB-4 would look out of place between $50 midranges). But I see its distortion profile is quite a bit higher than the D26.

[John D]

The information provided is minimal .

You might want to consider crossing lower. A lower crossover frequency makes the response more uniform. Then larger tweeters come into the picture, like a Seas h1212. This tweeter is capable of going quite low, making it a good candidate for d'Appolito configuration.

EDIT: I started this post before TS posted his last one. The first line might be a bit out of place now ops: .

[Curt C]

Curt, the design uses the RS225's as outer woofers, the W4-1337s as midranges and (so far) an RS28 tweeter, in a WMTMW format. I'm trying to minimise CTC space, and the RS28 is a bit too big now that I switched from RS150s to the W4s (since the W4s don't have any issues playing higher than 1.8 KHz).

You shouldn't have to worry about the driver spacing with these drivers. The RS28 is usable at 1800 Hz 4th order acoustic. Other options are available as well, such as the Seas 27TBFC/G as John suggested.

Due to the low frequency limitations of the ribbon tweeters, I crossed the Statements much higher than the 'rule of thumb' would suggest, yet Jim reports no audible vertical response irregularities in that design. This just goes to show that some ideals can't stand up to the harsh demands of physical reality, and that all 'rules' can, and often must, be bent to obtain the best compromise for a given design.

C

[JoshK]

Buy extra's...then you have a backup if you blow one.

[Jonasz]

Maybe there's a way to (with some creativity) mount the Neo3PDR "behind" the faceplates of the W4s? I'm trying to do something similar with RS52 and Neo3...

[Jonasz]

I crossed the Statements much higher than the 'rule of thumb' would suggest

Maybe this is a subject for another thread but... how important is this CTC-spacing in reality? Is it more like a theoretically correct value or does it have a noticeably impact of the sound?

[peter_m]

W4 as in TangBand? If you are planning to x-over low (which I think you are since you are worried about center to center spacing) why not consider the less expensive Hivi B4N or M4N?

Peter

[Curt C]

Maybe this is a subject for another thread but... how important is this CTC-spacing in reality? Is it more like a theoretically correct value or does it have a noticeably impact of the sound?

I think, like most things it depends on your design constraints.

If the requrements as such that the listeners will all be at the same limited listening angle, it will probably matter little. Certainly there are many commercial and DIY designs alike that break the spacing rule of thumb and are widely accepted.

On the other hand, if you like to sit, stand, move about the room while listening, and are acutely attuned to response variations, you will likely want to weigh the spacing issue more heavily in your design parameters.

C

[fjhuerta]

Maybe there's a way to (with some creativity) mount the Neo3PDR "behind" the faceplates of the W4s? I'm trying to do something similar with RS52 and Neo3...

Check out Meniscus' Audio faceplates for the Neo3. They look pretty cool and they can be used the way you describe! I used them on my Miniliths... they work very good.

[fjhuerta]

I think, like most things it depends on your design constraints.

If the requrements as such that the listeners will all be at the same limited listening angle, it will probably matter little. Certainly there are many commercial and DIY designs alike that break the spacing rule of thumb and are widely accepted.

On the other hand, if you like to sit, stand, move about the room while listening, and are acutely attuned to response variations, you will likely want to weigh the spacing issue more heavily in your design parameters.

C

Thanks a lot, Curt. Your comment is very helfpul, especially since I did wonder why the Statements crossover was so high!

[thadman]

Maybe this is a subject for another thread but... how important is this CTC-spacing in reality? Is it more like a theoretically correct value or does it have a noticeably impact of the sound?

CTC distance will have a massive effect on power response (below approximations assume even order crossover slope)

At 1 WL (~170mm at 2000hz), the interference pattern will produce 3 lobes (1 @ 0*, 1 @ 90*, 1 @ -90*). 0dB at 0*, -12dB+ (huge null) @ 30*/30*, -1dB @ 60*/-60*, 0dB @ 90*/-90*

At 1/2 WL (~85mm @ 2000hz), the interference pattern will drastically narrow the beam of sound (one lobe, basically very little energy past 30* and no energy past 60*). 0dB @ 0*, -3dB @ 30*/-30*, -12dB @ 60*/-60*, 0dB @ 90*/-90*

At 1/4 WL (43mm @ 2000hz), the interference pattern produces little discontinuity in the power response. 0dB @ 0*, -1dB @ 30*/-30*, -2dB @ 60*/-60*, -3dB @ 90*/-90*

[Curt C]

Thanks a lot, Curt. Your comment is very helfpul, especially since I did wonder why the Statements crossover was so high!

The harmonic distortion plots I saw of the Neo3 indicated increasing distortion below 4K, so the decision was made to not push the (distortion) envelope any further than we did.

C