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Author Topic: LAB_V1_&_V3 excursion tests  (Read 10691 times)

Michael_Elliston¶

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Re: LAB_V1_&_V3 excursion tests
« Reply #20 on: June 09, 2005, 04:51:08 pm »

TT wrote on Thu, 09 June 2005 20:50

Hi,

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


Tamas-The interesting thing about the 'ideal' Driver,is that changing BL only seems to only change the excursion peak below cutoff,so if one used a good subsonic filter one could use a low bl driver rather than go to high expense with large powerful motors. The other small effect is seemingly worse ripple in HF response from undersized horns with low BL drivers.

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Tamas Tako

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Re: LAB_V1_&_V3 excursion tests
« Reply #21 on: June 09, 2005, 05:05:57 pm »

Mike,

You are right, however what is in your view "lo BL" 15" driver?

I think around 20-25Tm... But reach some 2x 20-25Tm with two air gaps is not so easy, but possible...

Anyway the ADIRE's motor is quite clever...

If you know some concrete driver, please let me know!
Very Happy

In the meantime take a look to the BMS 15N840 15" Nd driver...
(1200W AES, +/-14mm Xmax ca. 30Hz Fs etc...)

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Michael_Elliston¶

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Re: LAB_V1_&_V3 excursion tests
« Reply #22 on: June 10, 2005, 08:13:54 pm »

TT wrote on Fri, 10 June 2005 09:05

Mike,

You are right, however what is in your view "lo BL" 15" driver?

I think around 20-25Tm... But reach some 2x 20-25Tm with two air gaps is not so easy, but possible...

Anyway the ADIRE's motor is quite clever...

If you know some concrete driver, please let me know!
Very Happy

In the meantime take a look to the BMS 15N840 15" Nd driver...
(1200W AES, +/-14mm Xmax ca. 30Hz Fs etc...)



Low BL for a 12" would be near 12TM

Locally all that is possible here is PAUDIO or EMINENCE.
Im not sure if a high Xmax HT type woofer will provide reliability in prosound-sudden destruction.
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Too Tall (Curtis H. List)

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Re: LAB_V1_&_V3 excursion tests
« Reply #23 on: June 12, 2005, 09:26:03 am »

Thanks for the careful work TT.
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Too Tall
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Gareth James

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Re: LAB_V1_&_V3 excursion tests
« Reply #24 on: July 02, 2005, 09:57:47 am »

Hi everyone,

I have been playing around with some figures for a possible prototype using the BMS 15N840 drivers, as mentioned earlier in the thread.

Sorry if sound stupid here but im having trouble interpreting the excursion data that Tamas measured and am trying to compare the benefits of the 15's.

Tamas, in your spreadsheet it states a 16mm p-p or +/- 8mm movement at 30hz for the V1 at 40v. Is this correct?

Am i missing something vital, the displacement i get in McBean is +/- 16mm which is 32mm overall?!? I read and re-read the help on McBean but it clearly states one way displacement. If it was peak-peak displacement this would make sense, (i think).

Just want to clear this up in my mind as its hampering my progress on a few projects im designing for possible prototyping in McBean.

Please someone help!

Gareth James
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Tamas Tako

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Re: LAB_V1_&_V3 excursion tests
« Reply #25 on: July 06, 2005, 03:55:04 am »

Hi,

I was waitin for that question.....
I did the tests 100% precise, so I am sure the test results are good.
If you can remember TOM DANLEY posted predictions for 4 and 6 LABSUBS halfspace @30Hz and at excursion limit (143dB rms, 149dB peak for 6 LABSUBS)
Well I measured 142-143 dB @30Hz for 4 LABsubs, which is very close to TOM's predictions.
However If you calculate with HORNRESP, at this level (143dB@30Hz for 4x LABSUBS in HALFSPACE), you would get an excursion, which is not real, becouse the driver units are not capable to move as big!!!
I also had a fellow, who made an AKABAK modell for 4x LABSUBS in HALFSPACE to see what Excursion this would predict, but this also was approx. the same as HORNRESP predicted.
So all I can say is, that in reality my results are true, but nor HORNRESP's nor AKABAK's prediction is true in this case!!!!
However TOM's prediction was TRUE!!!!!
This man knows something, you can belive me.........
Embarassed  Confused  Cool  Very Happy
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Gareth James

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Re: LAB_V1_&_V3 excursion tests
« Reply #26 on: July 06, 2005, 10:45:32 am »

thanks for the reply tamas,

Do you think the reason the actual excursion is so much lower than the predicted results (hornresp etc.) could be that these programs do not take into account the coupling effect of the cabinets accurately?

Your tests were all done for 4xLABs in an array, do you think the predicted would be closer for a single unit?

Cheers,

Gareth James
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Brad Litz

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Re: LAB_V1_&_V3 excursion tests
« Reply #27 on: July 06, 2005, 09:06:06 pm »

Hornresp is not a non-linear model (as far as I know). As such it will tend to predict too much driver excursion at high power.

Look at p17 of this article:

http://www.klippel.de/pubs/assesslargsign/assessing_large_si gnal_performance.pdf

This site has a lot of info on non-linear large signal (high power) driver performance.

http://www.klippel.de/background/default.asp
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Brad Litz

Gareth James

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Re: LAB_V1_&_V3 excursion tests
« Reply #28 on: July 07, 2005, 04:32:23 am »

Thanks brad,

I didn't realise about the other factors limiting displacement, its pretty complicated stuff!

Guess ill just wait til someone incorporates these klippel prediction parameters into a simulation..mr mcbean? Very Happy  Rolling Eyes

Gareth James
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Walt de Jong

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Re: LAB_V1_&_V3 excursion tests
« Reply #29 on: July 08, 2005, 07:52:09 am »

As for the difference with hornresp:

Please notice the theoretical difference between halfspace radiation and putting a cabinet on the floor. Normally we call the later one also halfspace but that ignores the fact that for a large stack the frontal area of the cabinets also starts to work as a boundary. A true halfspace measurement is a driver or cabinet flush mounted in a very large wall (infinite baffle)

By the way, using AJ-horn with the option 'floor' for placement gives +/- 8mm at 40V at 30Hz.

Best regards,

Walt

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