Mid-woof to integrate with Vifa XT25SC90

[carlmart]

Which would be a nice mid-woofer mate for a small box, closed or vented, using the Vifa XT25SC90 as tweeter?

It should be something from 4" to 5.25".

[Michael Chua]

I mated it with Zaph ZA14. Great for vocals. You'll need a sub for bass though.

Build info

[carlmart]

Interesting combo. This whole project started with Madisound's ZA5.2 kit, based on the ZA14.

But I didn't like the kit's Vifa tweeter, so I looked for something different. Thought the SB29RDCN might a better choice, if I am going to listen to it all day.

As the xover would have to be re-designed anyway, I looked for other options to the ZA14. Simulated them in Bassbox 6 Pro, in closed and vented versions.

To my surprise, I got the better low end response prediction from another SB speaker: SB Acoustics SB12NRX2504. 56Hz for F3.

As so many projects are using radiator ring tweeters, I thought why not try one. And that's how I got to the Vifa XT25SC90.

And now you put the Zaph ZA14 once again into the picture. A complete circle.

You're right about the ZA14 lack of real bass, as BB6 diagnosed an F3 of 87Hz. In any case, we must not forget this is a near-field project.

So I ask, if , why not mate the XT25SC90 with the SB12NRX2504?

[Michael Chua]

The SB12NRX2504 is a perfect choice for the XT25SC90. This mid-woofer is very impressive. Loaded in BR box:
5.5L box ---> F3=55Hz
8L box ---> F3=47Hz

Best of all, the Voice Coil Linear Travel = 10mm p-p. With contouring, you can get this 4 inch to kick some bass.

The SB12NRX2504 can easily be crossed at 3,500Hz with the XT25SC90. I find that below 3,500HZ, the Vifa starts to strain. Try to keep the tweeter at 3rd or 4th order.

[carlmart]

That's very good news you are also impressed with the SB mid woof. My guess was the VC Xmax was a good place to start. I think that driver remains one to be discovered, as I think it's the best of SB's small drivers. I compared it to the new Vifa NE (very nice) and some Scanspeaks, and I think only the SS 5" Revelator improves on it. For a lot more money.

With your suggestion on where to cross it, which I agree with, I might simply use this 18dB/oct xover for the Vifa XT.

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I guess I can get away with a 12dB/oct for the SB too, but I'm still trying to learn how to simulate it all with FRD tools.

FRD Consortium

An 8-liter vented box is a very good suggestion, but modeling and first tests will be done on an existing 5 liter box I have: 220mm h x 120mm w x 120mm d. What do you think?

[Michael Chua]

Feel free to use the 18dB/oct crossover for the Vifa XT.

Though this tweeter is very good, I should mention that you won't get the "presence" in the vocals. For the mids/vocals to be forward, I have to resort to tweeters that can be crossed lower (in the region of 2kHz).

For tweeters like the XT that crosses at 3K~4K, I use them in speakers for general listening. Great for background music while on the computer.

The SB mid-woofer will be fine in a 5L box. According to modeling, 5.5L is optimum. This is about the same size as my Hafler M5 near field monitors. I'm sure your speakers will sound better. In my M5, the mids are muffled.

Apart from the crossover, I strongly recommend adding some contouring for bass. It will be a waste if there's no bass punch with these SB.

[carlmart]

Just now did I realize that the Swift project was your design. Congratulations!

I would love to listen to it, and it probably sounds better than the ZA5-2.

Your comments about the vocals presence might have to do with those "pits" in 1800 and 3000Hz. Zaph's roughness perhaps? Why shouldn't the main driver fulfill its mid functions as it should and be smooth there, providing all the presence you need?

OTOS, did you try crossing at 2500Hz? Or is the XT frequency spec wrong?

Should I consider going back to the SB29RDCN?

https://www.madisound.com/store/manu...DCN-C000-4.pdf

That one might be crossed at 2K me thinks...

[Michael Chua]

Thanks for the compliments. Even though I design amps, I enjoy designing speakers too.

I have not listened to the ZA5-2, so can't really comment. What I can say is after testing out Zaph's ZA14, they are quite good drivers. Fast and clean. Suitable for near field vocal monitoring where bass is not really required, or desired for that matter. For full range, they will work great as satellites, especially in closed box where F3 is about 100-150Hz. Below that, a sub can take over.

With regards to the lack of presence in the vocals, I don't think it has to do with the ZA14. It's not that there's no vocals or they sound muddy. Just that when I cross any mid-woofers at 3-4kHz, I don't get the kind of forwardness and clarity that a good compression driver and horn can give.

My initial test of the Vifa XT was at 2.5kHz at 18dB/oct. The tweeter sounded strained. Moved up to 3kHz. Still not right. Only at 3,500Hz, the XT sounded sweet. For other listeners, it may be fine at 2,500Hz. Different people hear differently. Maybe my ears are sensitive to tweeter resonance.

Personally, I would use the SB29RDCN with the SB12NRX2504. I have not tried the SB29 tweeter but judging from the specs, it should be able to cross at 2kHz to 2.2kHz. I know the Seas 27TDFC can do 2.2kHz at 18dB/oct. Did that with a Seas ER18RNX. When I crossed the 27TDFC actively at 18dB/oct, I even managed 2.0kHz. In fact, I'm listening to it now with my Biamp Kit.

[carlmart]

Very interesting amp design the Synergy. Congratulations too.

An active amp like yours allows trying different frequency points to cross before designing the passive xover. Very clever.

I'm also into amp design and built a pro portable microphone preamp some time ago, that sold in the US.

The Seas 27TDFC is a very nice tweeter, even if in Zaph's tweeter testing the simpler 27TDF looks cleaner. But both tweeters suffer a bit when compared to the SB29EDCN, which could be crossed at 2K with no strain.

It seems that my guess of using two SB units for this design was not bad after all. Pity it would cost me $44 more to see if I am right.

[carlmart]

An additional note.

Today I decided to investigate passive radiators a little to consider using them on this project.

Apparently the woofer's Qts should be less than 0.4 to get better results with a PR, and you don't need to use the same woofer's size for the PR.

So I may put a 5.25" Peerless 830880 with my SB 4" woofer, which does have a Qts = 0.4 and get better results than with vented box.

It seems like a nice icing on my cake, don't you think?