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In Reply to: RE: Modified Tympani midrange driver posted by Satie on November 23, 2014 at 16:17:05
The BG drivers are very expensive in Eurpoe.
You will need 14 or 16 BG Neo8-S drivers to replace T-IVa mids. They are $2225-2580 in Europe. Rebuilding the mids were $410.
Follow Ups:
Yeah, that's true Roger :=(I have actually understood that 6 NEO-8's per side would be enough, but still it is a really expensive option in here. I don't know if there is any cheaper shop in Europe than this:
http://www.audax-speaker.de/index.php?module=shop_articles&index[shop_articles][action]=details&index[shop_articles][category]=11&index[shop_articles][data][shop_articles_id]=105
But, where did you get the new foil for your modification? Do you have any pictures or story about the whole modification process?
Edits: 11/26/14
Well, six Neo-8 are just 120 cm tall. I prefer the mid to have the same height as the ribbon tweeter, 7 or even 8 then. I have not seen any other distributor than Proraum (audax-speaker) in Europe. You can buy them from parts-express, 12 pieces for $1200+shipping+customs+VAT.A question: What size is the diaphragm of a Neo-8? The T-IVa is about 8x140 cm.
I bought the foil from Magnepan. It is their thinnest and it is equal to AWG 32 (as used originally in the T-IVAa mids). This foil is used in the mids of the 20-series. The foil is $35+shipping. The foil with adhesive is $50+shipping (not during the winter). The adeshive is available in Europe but under a different name.
Will give you the whole story later. Right now, the drivers are just resting in storage. My project will not continue until next year.
Edits: 11/27/14
I too would have put in 8 drivers rather than 6 in a T-IVa, even though the slot is a little short to allow the entire 8th driver's output surface to be active.
The free portion of the diaphragm is 6cm wide and the holes cover a near 5 cm width, which is what seems to determine dispersion. In the Neo8 PDR the radiating surface at higher freq is restricted mechanically and thus improves dispersion.
What exactly is the difference between NEO8, NEO8s and NEO8 PDR? Which one would be the best for IV's?
The Neo8 - when operating as a line array of 6 or more has a usable freq range of 250hz to 6khz with good dispersion and an additional output to 10khz with significant beaming as you rise in freq. Sensitivity is about 96 db.
The Neo8S is designed for a similar operating range but has better performance at the bottom end. It has bigger magnets, is heavier, it is 8 ohms vs 4 ohms for the other Neo8s and has a corrugated diaphragm. Sensitivity is about 2 db higher so expect > 98 db sensitivity for a line of 6 or more. It is also more expensive. The design is taken from the bigger Neo10 mids.
The Neo8 PDR is designed for use as both mid and tweeter. It does not play as low as the Neo8 but does play up to 14kz in a line array. It haa lower power handling and lower sensitivity. It really isn't appropriate for a T-IV midrange since you have a better HF unit in the ribbon.
The Neo8s is probably the better choice for a T-IV mid but considering that the original Neo8 is quite robust and plays fairly low, I think the plain Neo8 is good enough and significantly cheaper. You would prefer the Neo8s if you wanted the higher output (sensitivity) and were going to drive them hard with dense midbass material.
True, 6 are enough, 8 are better. If I was modding a T IVa I would have tried to fit 8 into the slot. If I get around to building new frames I will extend the line to 8 per channel. With 8 per channel I can lower the XO from 250hz to 200 hz. It might seem foolish to put in that much for such a small change but it is a rather critical point in the freq spectrum for fundamentals so you want this much faster driver to do the work rather than the bass panels.
Using Neo8-S I would have been able to cross over that low with 6 drivers per side. Extending to 8 drivers per side is not necessarily going to have the same useful extension at the bottom. At <200hz you have much higher energy content to music and this introduces large vibrations to the mid/tweeter panel and thus IMD to the ribbons. So this would require better isolation for the tweeter and a stiffer frame.
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