Any news from CES 2007 yet?

[bidland]

Originally posted by Paul W
Bjorn,
What are the main features and characteristics of the T29MF001?
Thanks,
Paul

The T29MF001 has a flatter frequency response than the T29AF001. We have used a shorter voice coil to get a lighter moving system, lower inductance and more linear excursion. It also has the Hexadym magnetsystem with low viscosity ferrofluid.

I see now a typo in the datasheet. The surround is from Sonomex (fabric), not Sonomax (polymer) as the datasheet says.

Even though the magnesium dome is much stiffer than the aluminum dome, we still see the break-up in the frequency response at 27 kHz. The reason for this is that the break-up frequency is not determined by the stiffness of the dome alone, but how the whole moving system interacts.

Bjorn

[noah katz]

Bjorn,

Perhaps you are in a position to answer a question I've had for many years.

Alumuminum, titanium, and magnesium all have similar stiffness/density ratios.

Making same-weight diaphragms from each material, the one with the lowest density will be the thickest and have the highest first resonance frequency because bending stiffness increases with the cube of thickness.

On that basis alone, magnesium should be the best diaphragm material, and additionally it has far greater internal damping.

Finally to the my question: Why therefore are there not more tweeters with magnesium diaphragms?

And why are there so many titanium tweeter diaphragms when aluminum would seem to be both better and les expensive?

Thanks very much.

[capslock]

Data sheets are up:

http://www.htguide.com/forum/showthread.php4?t=24231

I posted my thoughts on the new drivers in above thread:

Hmm, I have no idea what the surround of the new Mag cone drivers look like. If anybody could snap and post a pic, that would be highly appreciated.

The new tweeters look like winners. The Nd ring magnet seens to allow for much better airflow. Their impedance curves have much higher mechanical Q compared to the TBC and TDC which are also non-ferrofluid drivers. Actually, the TBC and TDC are closer to their ferro siblings TBFC and TDFC than to the new Nd cousins.

The new titanium TTNC dome has its supersonic breakup at exactly the same frequency (27 kHz) as the older AlMg dome used in the TBC and other models, but the breakup peak is much less severe (15 compared to 30 dB), as is the off axis 17 kHz dip.

Interestingly, they say they are using an aluminum VC former. If this is really the case, they are using a two piece design with a glue joint between former and dome (normally, metal domes are extended so that dome and former are made from one piece of metal). This and the higher density of Ti nonwithstanding, the lower mass of 0.32 g is actually less than the 0,33 g of the TBC.

With sensitivity being identical and fs close, the TTNC could be a drop in replacement for the TBC, but the front plate diameterhas also been reduced

Also, they have failed to answer my prayers for a version of the TAFNC that will actually fit inside the 38 mm VC of their 7 and 8 in. woofers


I am not a big fan of paper cones, but their new reed/paper ER series looks like a winner, too. FR is very extended, and there is comparatively little evidence of cone resonances.

The bigger ER18RNX is not as clean as the ER15, but the 6 dB peak at 4.8 kHz still looks reasonably benign, and exention to 7 kHz is not bad at all for a 7 in. driver.

They used the biggest motors availably and pretty long coils (+/- 5 resp. 6 mm linear travel is very unusual for a full range). The ER18 uses a lower shorting ring, a first in a non-Excel Seas driver, as far as I know. The pole piece is most likely identical to those in the L18RN and W18EX, and that means a full Excel grade SD motor can be retrofitted by just removing the dustcap and inserting the top ring (for the L18, one needs to disassembly and realign the magnet to insert the lower ring).

[bidland]

Originally posted by noah katz


Finally to the my question: Why therefore are there not more tweeters with magnesium diaphragms?

Thanks very much.

Hi Noah,

Magnesium is very difficult to shape from a flat foil to a dome compared with aluminum. That's the main reason. Another issue is the potential corrosion problems. Magnesium needs a good protective coating.


Eric,

The Prestige tweeters will be released with ferrofluid. I sent out the wrong file....

You are right about the use of copper rings in the ER18. It's the first outside the the Excel series. We wanted to lift this product to a level between the CA18RNX and the W18NX001.

Bjorn

[Michail Bugaria]

These new Seas look very interesting!
And the decision to equip that new midwoofer ER18RNX (H1456) from prestige series a short-circuited ring in magnet system seems to me very correct. For example, Peerless and Dayton in this price range show simply phenomenal productivity and in many respects owing to their advanced motor. Whether practice of equipment short-circuited rings in prestige series will be continued?

And Bjorn, check the magnet weight on W22NY001 driver. Similar on that is a mistake in the specification.

[hooha]

Very sweet...

[bidland]

Originally posted by Michail Bugaria


And Bjorn, check the magnet weight on W22NY001 driver. Similar on that is a mistake in the specification.

No, thats correct. It's a new magnetsystem. The largest we have for 1.5" drivers! OD=134mm and the height is 24mm.

Bjorn

[capslock]

Originally posted by bidland



The Prestige tweeters will be released with ferrofluid. I sent out the wrong file....

Pity, but I can always drain the fluid

Is it really true that the TTNC uses an aluminum former, i.e. an aluminum former is glued to the titanium dome?


Do you have any idea why the impedance curve of the TBC is so much broader than that of the TTNC? It looks like the TBC has ferro, but of course, the TBFC has an even broader curve.

Could be due to restricted air flow in the TBC or to eddy current losses in the aluminum former (assuming the TTNC really uses a titanium former which has lower conductivity).

[bidland]

Originally posted by capslock



Pity, but I can always drain the fluid

Is it really true that the TTNC uses an aluminum former, i.e. an aluminum former is glued to the titanium dome?


Do you have any idea why the impedance curve of the TBC is so much broader than that of the TTNC? It looks like the TBC has ferro, but of course, the TBFC has an even broader curve.

Could be due to restricted air flow in the TBC or to eddy current losses in the aluminum former (assuming the TTNC really uses a titanium former which has lower conductivity).

Hi Eric,

Yes, we glue an aluminum former to a titanium dome.

The difference in the impedance comes mainly from the differences behind the dome. The new ring-neo system has a very shallow polepiece compared to the ferrite magnetsystem in the 27TBC.

Bjorn

[nate]

My friend Mike posted a couple pics of the new Seas drivers here.

http://blog.speakergeeks.com/index.p...s-2007/page/2/


Nate