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Author Topic: LAB_V1_&_V3 excursion tests  (Read 10705 times)

Tamas Tako

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Re: LAB_V1_&_V3 excursion tests
« Reply #10 on: June 07, 2005, 01:57:03 pm »

Hi,

I try to upload a zipped folder where you can find some pictures and excelsheets with the results and the measurement arrangement.

I also will attach some jpg screenshots of the measured responses.

There are some LAB12 VoiceCoil photos as well, showing the possibly most common failure reason and a solution for it.

The glue used for this purpose is a two component Araldite epoxy.
Type:Araldite Resin AW106 with Araldite Hardener HV953U (1:1 mix ratio)

I hope this is usefull information for all here.

Best Regards,

Tamas
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Brad Litz

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Re: LAB_V1_&_V3 excursion tests
« Reply #11 on: June 07, 2005, 06:30:59 pm »

Your measurement results show that the v3 design fills the dip between 30 and 50 hz which I measured as well. The displacement measurements also compare well with the predictions from Hornresp analysis.
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Brad Litz

Tamas Tako

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Re: LAB_V1_&_V3 excursion tests
« Reply #12 on: June 07, 2005, 06:44:15 pm »

Hi Brad,

Yes. I also mailed with Dave McBean about the results.
For very High power usage (and without your mouth extension) however the excursion starts to be too big around (and below)30Hz for the V3..

All measurements where done in halfspace using 4 enclosures to get a reasonable loading.

It would be great to have some 2x 15" version of the V3 to get less excursion down there.
(well the BT7 was a 2x15" box....)

Best Regards,

Tamas

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Brad Litz

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Re: LAB_V1_&_V3 excursion tests
« Reply #13 on: June 07, 2005, 07:16:39 pm »

It would seem to me that if you are OK with a high pass filter at 30 Hz you can get more output with v3 from 35 to 50 Hz.

I like the 12" drivers because the cone can be made very stiff and does not break-up into higher resonant modes.
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Brad Litz

Michael_Elliston¶

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E x c e l l e n t!
« Reply #14 on: June 07, 2005, 10:32:31 pm »

This is excellent,actual measurements to compare to simulation,we are fortunate people! Very Happy  Very Happy
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Bogdan Popescu

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Re: LAB_V1_&_V3 excursion tests
« Reply #15 on: June 08, 2005, 12:29:44 am »

Thank you TT

You have some nice tools there.

What is actualy the limit excursion where one would have to worry? Is it the 44mm mechanical limit or the Xmax ?

All the best,
Bogdan
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Tamas Tako

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Re: LAB_V1_&_V3 excursion tests
« Reply #16 on: June 08, 2005, 05:05:38 am »

Well there are several points of view:

1. Machanical demage:
You would demage the surround and/or the spider and/or the Voice coil when you exceed the mechanical limit of movement, what is 44mm If I remember correct.
However to reach such a large excursion one would need a big amount of power (current) which would burn the VoiceCoil.


2. Acoustical output:
The Magnetic Gap is ca. 10mm deep and the VoiceCoil is ca. 37mm long.
This gives a linear excursion of ca. 26mm (+/-13mm)
When I don't count with the magnet structure's (thermal)power compression (however I should!!) then exceeding this excursion gives me a decreased BL product and THEN all TS parameters changes...

This means for example that at 31mm(+/-15.5mm) excursion I just have the -3dB points of the BL product. While F= BxIL, this means that for reaching this excursion, you would need ca. 3dB more power than you would need normaly (if you where in the linear excursion range)

This also means, that above 27Hz you surely can't exceed the
-6dB BL points (+/-18mm) with an INPUT power that wouldn't burn the VoiceCoil. This point would be maybe the absolute non repeated peak.

So if you use a HPF at 30Hz with a slope of -24dB/oct, you surely will not reach the mechanical Xmax.

Brad,

I agree, the 12" cone is a great winner in this application.
BTW I think, one could get ca. 3-4dB more output @30Hz with a pair of good 15" drivers, where the cones should be very stiff...

Cheers,

Tamas

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Michael_Elliston¶

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XBL
« Reply #17 on: June 08, 2005, 04:45:54 pm »

Hi Tamas
Voice coil heating seems a worse problem than over excursion,when appropriate subsonic filtering is applied.

What about XBL2 - Good for high horn SPL?

http://www.adireaudio.com/TechInfo.htm
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Phillip_Graham

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Re: XBL
« Reply #18 on: June 08, 2005, 09:38:09 pm »

mike_nz wrote on Wed, 08 June 2005 16:45

Hi Tamas
Voice coil heating seems a worse problem than over excursion,when appropriate subsonic filtering is applied.

What about XBL2 - Good for high horn SPL?

http://www.adireaudio.com/TechInfo.htm


XBL is a cleverly designed gap structure that results in very linear BL product over a broad range.  Outside of this, it has the same basic other types of limitations (heat dissipation, cone stiffness, etc.) as any other driver.

One of the principles of Adire is Dr. David Hyre, formerly a researcher in NMR (nuclear magnetic resonance) at the University of Washington, and active back on the HiFi design lists in the mid 90's.

He was one of the first people I ran across who REALLY knew what was going on with designing loudspeakers, and I learned a lot from email conversations with him.  I am sure future products from adire will continue to be most impressive.
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Tamas Tako

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Re: LAB_V1_&_V3 excursion tests
« Reply #19 on: June 09, 2005, 04:50:25 am »

Hi,

I knew this Motor structure, and Yes this is a real good solution to have long excursion.
However there is a small disadvantage of this design:

While you have two air gaps (below each other), you need twice the B*A in the magnetic path to get the same air gap Flux density as you would get in a conventional Motor structure design.
This means double the B in the magnet (expensive magnet material) with the same surface, or the same Magnetic material with same B, but twice the surface (2*B)*A= B*(2*A)...

This means heavier and more expensive Assembly...
(this may be only expensive but not heavy by using high temp. NDy. magnets.)

Anyway, having such a 15" driver with good TS parameters and a quite stiff cone would make it possible to design "2x15" LABhorn" a la BT7. (Mike, you have the File on your website where Tom Danley was writting about the possibly TS parameters for the LABhorn if they were 15" drivers instead of the 12"...)

Cheers,
Tamas
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