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Pete B

Low Cost Advent Tweeter Replacement

10 posts in this topic

I'm looking for a low cost Advent Tweeter replacement and I've got a pair of the bargain ($36/matched pair) North Creek D25s. The D25's have a .5mm (1mm peak to peak) Xmax which should make them suitable for a low XO point. These have been tested and shown to be competitive with the "big (very expensive) boys" in low end distortion:

http://www.euphase.com/Design/DriverCompar...rComparison.asp

But remember they are low cost, one advantage is that you get response curves with them and George at North Creek is easy to deal with. The response above 10 kHz so far has some roughness, George says they smooth out with break in of the soft dome. I'm going to try to test this theory. George also mentioned to me that some customers were crossing over at 1 kHz first order, which is hard to believe, but then they might be using 10W amps so your milage may vary.

They sound very good (in the first order 3-way system that I'm trying them in, have not tried them in the Advents yet), even the extreme high end and I did not hear the 15 kHz peak that's shown in the data sheet, turned out that my samples did not have this peak. I'm comparing them to the well known metal dome Vifa D25AG and they are very similar. I have a slight preference for the more expensive Vifa above 10 kHz but it is a minor point, I could easily live with the North and the Vifa has about half the Xmax of the North indicating that it would probably not work very well with a very low crossover point. Distortion and reliability tests would be needed to determine if the Vifa might be suitable.

I'm planning, as time permits, to discuss details about the North D25s a bit more on my own speaker design discussion group in case anyone wants to join:

http://groups.yahoo.com/group/AspkD/

You have to have a yahoo ID to join and you can turn off email, and just visit the web page to read as you want if people prefer.

I'm waiting for woofer edge foam for the Advent woofers then will try the North D25s in the Advents and see if any crossover mods are needed.

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I'm going to post details like this at my own discussion group, I'm offering a sample here in case anyone is interested. I'll redo this test with the North Dome with the Advent XO. This is an example for the Vifa D25AG dome with a high 1st order XO:

-----------------

Forwarded Message:

I've had replacement Vifa D25AG domes around for many years and had

this idea many years ago, to simply hook up the replacement dome and

play a piece with a temperature probe on the windings. It's not

exact since there's no ferro fluid or thermal conduction to the

magnetic structure but it is a real world measurement as a worst

case.

I grabbed some compressed rock and roll, Roxanne by the Police at

party levels, 200W amp just hitting clipping, would not normally

play this loud but sound was still reasonably clean at this level.

1st order crossover about 5 kHz:

temp vs. time in minutes:

http://members.aol.com/basconsultants/D25AGROX.jpg

Goes from room temp 68 deg to about 106 deg F at end of song, data is

taken past end of song which is seen as the cool down period. Could

probably get thermal time constant from this data. This cut did not

seem to have a very high average level even though it is compressed,

some distorted electric guitar might be interesting. Also curious about what a complex classical piece might do.

One could get more accurate by dissasembling the magnet structure

and drilling/grinding to allow the probe to be inserted, this would

obviously be a non functional tweeter in the end. (I'd be curious to try the orange Advent and Layne replacement tweeters if anyone has dead ones they want to offer)

DCR goes from 4.5 to 5.1 measuring as fast as I can at the end of

song. The probe is somewhat larger than the VC wire it contacts, therefore I do not think the probe is tracking the temperature fully as there's some heat loss to the surrounding air. This is suggested by the fact that 5.1 ohms indicates a much higher copper temperature.

Wonder what a tweeter crossed over at 1 to 2 kHz does? Even 2nd

order, Ouch!

------------------

Here's a graph of the entire Police "Every Breath You Take" CD played

at the same level. I wore my woodworking ear plugs for this test.

I did not do a sanity check on the data, looks OK at a glance: Interesting that the aluminum dome helps dissipate the heat.

http://members.aol.com/basconsultants/D25AGALL.jpg

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Pete,

Any results with this tweeter yet?

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>Pete,

>

>Any results with this tweeter yet?

Hi Stan,

Sorry no, I work on these things as time permits, I'm busy at this point.

Pete B.

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>>Pete,

>>

>>Any results with this tweeter yet?

>

>Hi Stan,

>Sorry no, I work on these things as time permits, I'm busy at

>this point.

>

>Pete B.

I had given up on this tweeter because many stated that North was not selling it anymore, yet it is still in their 2007 catalog, and some here claim that it is still available:

http://www.diyaudio.com/forums/showthread....950#post1250950

I've not been able to get through to George at North.

Here are tests by Zaph on the $18 North D2506-S and it is interesting to compare it to the $87 Scan 9500, or the $160 SEAS Millenium. The Hi-Vi K1 for $9 is also interesting but he suggests it should not be used with a low crossover point:

http://www.zaphaudio.com/tweetermishmash/

An important question is if the Hi-Vi K1 uses tinsel lead in wires which are required for reliability with low crossover points.

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Here is the long story about North Creek:

http://www.northcreekmusic.com/North_Creek...d_Statement.htm

I think the story is that he intended to stop selling to the DIY community, seems all along he intended to keep his educational support going, and this tweeter was part of some of his educational kits. This seems to be their final conclusion, that they will continue to supply kits and hopefully replacement parts for them:

"I talked it over with the team, and the conclusion was that since we continue to produce the Okara II - North Spirits and the Kitty Kats as finished systems under the North Acoustics brand name, it makes business sense to continue them as kits as well."

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I heard back from George at North and he says that they still have stock on most parts in their 2007 catalog, and over 1000 of the D2506-S tweeters.

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Hi Pete;

Thank you for that link to, "Zaph".

I found the brief write-up/commentary of each tweeter really of value.

It does give some suggestions for us for alternative tweeters.

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Hi again;

After going back and looking at the graphs, very interesting, at Zaphaudio, I wouldn't mind seeing some of the classic tweeters tested for comparison using the same testing methods.

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Here are tests by Zaph on the $18 North D2506-S and it is interesting to compare it to the $87 Scan 9500, or the $160 SEAS Millenium. The Hi-Vi K1 for $9 is also interesting but he suggests it should not be used with a low crossover point:

http://www.zaphaudio.com/tweetermishmash/

An important question is if the Hi-Vi K1 uses tinsel lead in wires which are required for reliability with low crossover points.

Finally looking at a pair of K1 tweeters here, they do use tinsel lead in wires and I believe they would probably work fine in the 5002 design and perhaps with a 7 ohm resistor in parallel in the New Large Advent. Just a warning that I've not tried this, the K1 is slightly small for the 5002 tweeter cutout. Low crossover points and lower order crossovers are not suggested with this tweeter, however I don't see the basis for this suggestion. Try them at your own risk:

http://www.diyaudio.com/forums/showthread....552#post1570552

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