Picolino downscaling

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voodooless

voodooless

Member
Joined 2004
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:

An externally hosted image should be here but it was not working when we last tested it.


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/speakers/vifa/xt/vifa-xt-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:

picolino.gif


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 :bawling:
 
J

joensd

Member
Joined 2002
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.
:D

It´s 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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voodooless

voodooless

Member
Joined 2004
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)
 
planet10

planet10

frugal-phile™
Joined 2001
planet10-hifi.com
Paid Member
4real said:
well, in this case, there realy is no difference with BR, so IMHO not worth a try (I would just make a BR then).
Click to expand...

A mass-loaded quarter-wave line will behave different than a similar volume (but more evenly proportioned) BR.

I would like to make a tapperd tml, like in the picture. The point is, mathcad cannot reproduce the measurements HH made
Click to expand...

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
 
voodooless

voodooless

Member
Joined 2004
joensd said:

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

Cheers
Click to expand...

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

An externally hosted image should be here but it was not working when we last tested it.


Simulates like this:

An externally hosted image should be here but it was not working when we last tested it.


-8 dB @ 40 Hz is not bad, and I even have room for my amp and FM receiver :)
 
voodooless

voodooless

Member
Joined 2004
joensd said:

now, where are you going?
wasn´t that supposed to be a christmas present for your parents?:D
Click to expand...


Yes it is :D, active wireless speaker, but I think I'll put some real terminal on it, too, for a real amp :). The thing I'm going to use now is 6 W TDA chipamp, not the best, but it will do...

you can fold the line and still keep the CSA constant.
Click to expand...

Sure I could, but it will not fit in the box. The resulting curve does not look very good either!
 
voodooless

voodooless

Member
Joined 2004
I hope te get the units this weekeind, and I might even get started with building it :)

Detailed plan with angles? Well, I'm not shure If there is realy going to be an actual detailed plan, but I might try to make something up tonight...

If it is realy going to sound as well as the simulations say, is just a matter of building and listening ;)

It will be my first TML project, so I'm very excited to get started with it :D

Pictures will be there when I have them :p
 
voodooless

voodooless

Member
Joined 2004
Just for the fans (and for my own ease), some drawings :angel:

I had to find a fairly decent pice of free CAD software to help me. I found QCAD, and it works very nice :D

At first a small png of the desgin:

An externally hosted image should be here but it was not working when we last tested it.
(don't expect to see any measurements on that picture ;) )

But here some PDF's

A2 format: http://deepspace9.xs4all.nl/~christiaan/picolina.pdf
A4 format: http://deepspace9.xs4all.nl/~christiaan/picolina_a4.pdf

All measurements in mm's

The lines are very thin, so your printer might not print very well.. I'll have to look into that.

I recommend that you don't build the thing befor I have no good results. You never now how bad I'm at designing stuff :smash:

I'll keep you posted!
 
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