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Old 7th November 2004, 09:07 PM   #1
4real is offline 4real  Netherlands
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Default Picolino downscaling

Well, since the standard Loudspeakers forum doens't give me a lot of response, I'll try to get some help here.

Well, I'm about to make a nice small speaker for the kitchen with a Vifa BGS 119/8, based on the Picolino tml speaker, for the german DIY magazine HobbyHifi (HH).

The problem is, that this thing is just a bit to big So I have to make them smaller, thus a shorter TML. I know it will not get as deep down as the orriginal, but that is nog so important.

Ik should look something like this:

Click the image to open in full size.

The box is about 20x25x16 cm

The problem is, that I cannot het a decent simulation of this tml. I used the mathcad worksheets to simulate the original design, wich can be found here:

http://www.audiocomponents.nl/speake...t-line_eng.htm

TSP of the Vifa (according to HobbyHifi):
Re: 5,5
Le: 0,20 mH
Fs: 61 Hz
Qms: 3,4
Qes: 0,62
Qts: 0,52
SD: 36 cm^2
VAS: 4 L
Cms: 2,2 mm/N
Mms: 3,1 g
Rms: 0,35 kg/s
BL: 3,3 N/A
Xmax: 0,65 mm

The problem is, I cannot reproduce the results that HobbyHifi has measured, no matter what I try The steady drop starts @ about 150 Hz with mathcad, while HH has a steep drop at about 60 Hz:

Click the image to open in full size.

They use AJHorn to simulate, and the results are very close to the actual measurements: http://deepspace9.xs4all.nl/~christiaan/10bgs-7.jpg

Sadly, I don't have AJHorn, so I'm hoping that someone can help me with some simulations, or maybe give me some other hints, so that the mathcad worksheets work...

Please help me
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Old 7th November 2004, 09:37 PM   #2
joensd is offline joensd  Germany
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Hmm, even in a straight TL it sims down to ~60Hz.
How did you simulate the Picolino with the mathcad sheets?
Did you put in the proper geometry with all the bends/area changes?
If so, you could send me the file.


Its a bit of a contradiction to scale down a TL but you should get nice results with your size restrictions.
One fold should fit nicely.
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Old 7th November 2004, 09:41 PM   #3
4real is offline 4real  Netherlands
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Yes, sure, you're cheating with a TQWT Yes, with that one, i can get to 60 Hs, but there is no defference with a BR response (just a extra peace of MDF

I want a real TML
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Old 7th November 2004, 11:54 PM   #4
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Quote:
Originally posted by 4real
you're cheating with a TQWT ... I want a real TML
IMHO, a TQWT is just another flavour of TL...

dave
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Old 8th November 2004, 12:04 AM   #5
4real is offline 4real  Netherlands
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well, in this case, there realy is no difference with BR, so IMHO not worth a try (I would just make a BR then).

I would like to make a tapperd tml, like in the picture. The point is, mathcad cannot reproduce the measurements HH made (and also what AJHorn simulated)
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Old 8th November 2004, 01:49 AM   #6
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Quote:
Originally posted by 4real
well, in this case, there realy is no difference with BR, so IMHO not worth a try (I would just make a BR then).
A mass-loaded quarter-wave line will behave different than a similar volume (but more evenly proportioned) BR.

Quote:
I would like to make a tapperd tml, like in the picture. The point is, mathcad cannot reproduce the measurements HH made
I would guess that the parameters have not been input correctly -- i've seen too many simulations get real close to spot on the resulting measure.

dave
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Old 8th November 2004, 12:40 PM   #7
4real is offline 4real  Netherlands
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Well, as i see it, it the parameters were not wrong, but that is why I need your help...

Well, I tried again, and now, I do get something similar to AJHorn, so I'm on the right way
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Old 8th November 2004, 04:42 PM   #8
joensd is offline joensd  Germany
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Quote:
similar to AJHorn
with the MJK-sheets or another software?
would you mind posting your results?

Cheers
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Old 8th November 2004, 04:50 PM   #9
4real is offline 4real  Netherlands
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Quote:
Originally posted by joensd

with the MJK-sheets or another software?
would you mind posting your results?

Cheers
Yep the sheets. I'm now about to make a 100 cm line like this:

Click the image to open in full size.

Simulates like this:

Click the image to open in full size.

-8 dB @ 40 Hz is not bad, and I even have room for my amp and FM receiver
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Old 8th November 2004, 05:02 PM   #10
joensd is offline joensd  Germany
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Did you put in the proper geometry or simulating with a 100cm line and constant cross-section-area?
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