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Here are two pictures of my rebuilt Tympani IVa midrange drivers. As you can see modified with foil conductors (same as the 20-series.
http://www.forumbilder.se/DELEL/t4a-mid.jpg
http://www.forumbilder.se/DELEL/t4a-mid-close.jpg
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Roger It has been a while since I posted on this site, but you may recall that a friend and I built some "Frankenpans" using Tympani 1-D's for the bass and III-a's for the mids and tweeters. When I redid the III-a panels I also used foil and I can truly say it is pretty awesome. The mids have a kind of crystal clear sound, and I also think that the longevity should be pretty good as well. It has been over a year I believe since the build and they are still going strong. I just added a DCX2496 X-over which has improved the sound significantly so far. I know I can do better, but the budget is limited right now, and this one seems to have some good tweaks if I can figure it out. It appears to be a very flexible crossover, but the docs could use some improvement. I understand the computer based configuration tool is much better, and I have ordered a cable so that I can use it. Do you have any idea what the crossover points and slopes etc. should be using the foil mids and this crossover, given my set up? Any comments would be greatly appreciated.
In addition, I am moving and need to downsize. I am contemplating selling the Tympani's but I don't think the bass on the III-a's is near as good. I think i have a mylar issue or loose cross bar in one, so I have not really been able to do a good A/B test. Plus the crossover issue needs to be settled as well. We are pulling the panel on the III-and sending it back to the factory for diagnosis and repair. I hope it is something simple.
I always appreciate your posts as you seem to have a good handle on the Maggies and their performance. Thanks again
Edits: 11/24/14
Nice work Roger!
I have understood that many IV(a?) owners in here have gained better mids by replacing them with a line on B&G NEO-8's. Did you give any thoughts on this option..?
No! The cost is too high compared to rebuilding the original drivers.
As Roger said, it is a more expensive proposition than a repair. But it also improves on the performance of the original mids, particularly those of the T-IV. The T-IVA mids are lighter and more resolving so the benefit is relatively smaller.
The biggest difference is less distortion and far higher power handling/spl output. that was important to me but would not be for people who listen at moderate levels, as Roger does.
Cost for a line of 6 neo8 per ch. is $1200 and 4 neo10/ch is $1600 in the US, at least 20% more in EU. I think it is well worth it.
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.
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.
They look very cool.
Have you tested them out with music yet?
I have not tested them yet. They will not go back to the originsl baffels so it may take while. Will not happen in the near future, perhaps early next year...
very nice. that should help with the delam problem. i finally broke down and went with the bg driver for my mids last time they started buzzing.
Which BG's did you go for, Hemholtz? How would you describe the difference in sound..?
(Sorry Roger if this is totally off-topic, but I could not resist asking...;-)
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