Picolino downscaling

[voodooless]

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:

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

 

[joensd]

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.
😀

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.

 

[voodooless]

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 😉

 

[planet10]

you're cheating with a TQWT ... I want a real TML

IMHO, a TQWT is just another flavour of TL...

dave

 

[voodooless]

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]

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.

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

 

[voodooless]

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 😀

 

[joensd]

similar to AJHorn

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

Cheers

 

[voodooless]

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:

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 🙂

 

[joensd]

Did you put in the proper geometry or simulating with a 100cm line and constant cross-section-area?

 

[voodooless]

Did you put in the proper geometry or simulating with a 100cm line and constant cross-section-area?

I simulated with a *SD from 3,6 tot 0,38 (as in the picture) . An constatnt cross section line is not very good, and won't fit the box 😉

I might do a more detailed sections simulation, but I think this one will do 🙂

 

[joensd]

and I even have room for my amp and FM receiver

now, where are you going?
wasn´t that supposed to be a christmas present for your parents?😀

An constatnt cross section line is not very good, and won't fit the box

you can fold the line and still keep the CSA constant.

 

[voodooless]

now, where are you going?
wasn´t that supposed to be a christmas present for your parents?😀

Yes it is 😀, 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.

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

 

[kyote]

Have you build this thing alreay?
How does it sound?

And would you mind to put a detailed plan (with angles and width) in here?
It looks real interesting.

And perhaps some Pictures?

 

[voodooless]

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 😀

Pictures will be there when I have them 😛

 

[voodooless]

Just for the fans (and for my own ease), some drawings

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

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

I'll keep you posted!

 

[kyote]

Ok. Im staying tuned in excitment of your results.😎

I hope my english is not too bad.

 

[voodooless]

Ok. Im staying tuned in excitment of your results.😎

I hope my english is not too bad.

No, I don't think so. I hope mine is not bad either 😀 . You can write in German to me, but I don't thinks that the majority of the diyaudio readers would understand that 😉

 

[kyote]

You can write in German to me, but I don't thinks that the majority of the diyaudio readers would understand that

Yeah, that's what I hink, too.

But it's a bit weird to write to e.g. Joens in english.
Lucky that there are german DIY forums.😀

 

[earsandeyes]

Workaround QCad

4Real,

How did you wordk around the 10 minute timelimit on the free software?


Regards,

E&E