Visaton FRS8 Flat transmission line speaker - how to calculate?

[Schlumpfpeter]

@GM
I thought so as well, but I must admit that I did not understand the software when doing the first two calculations, and therefore those calculations are wrong (wrong driver in the dataset).

I will try to have a look at a teppered version with the real FRS8 dataset, but as far as I remember, the straight line was the best.

Have you seen this design? VIFAntastisch ! Der Wandlautsprecher, Projekte der Nutzer / Eigenentwicklungen - HIFI-FORUM

I think it might be similar to what you are proposing. I have built a pair of these and they perform very well.

Graham.

Hi Graham!

Thank you so much for bringing this link back to my mind! I remembered that I saw this link around half a year ago. Then I found the spare FRS8 and wanted to build something, remembered that I saw this link but could not find itanymore.... so I started modelling for myself.

Funny enough, my endresult is completely similar to those speakers in the link (except for the driver)!

Thanks again, you made my day

 

[Schlumpfpeter]

Would you guys consider this a better result? I basically copied the driver position from the link above. I also gave it a testrun with the Vifa drivers from the original project, the results where quite similar.



The big gap below 500 Hz disturbs me a little bit. But as it is also there in the Vifa version, on which everyone who build that agrees that they sound great, I think I can just ignore it and start building the speaker.

 

[GM]

The gap isn't as bad as predicted since no internal losses are accounted for plus the higher it's 'pushed', the less damping required to get it flat enough without excessive over-damping [loss] of the bass BW.

Having recommended, built similar alignments for ~near-field and small room apps, I can attest to it being a good alignment as long as the actual driver specs aren't too far off, so when these are unknown I typically increased net Vb enough to get a 5-6 dB peak at Fb to 'cover my bases' and then 'critically' damped the vent if I heard any 'ringing'/'boom' out of it.

GM

 

[Jerms]

Guys, thank you so much for all your help.

I have finally found the best solution for my Speaker, it is a single folded straight transmission line design. I wanted to tune it to around 65 Hz and and the length of a 120cm long straight pipe almost matches this to the spot.

I already got the foamcore board for one box, the other foamcore board will arrive shortly

The design is dead simple with a Din A 2 foamcore board, as it is only a single folded design with a straight pipe. The depth of the speaker will be 5 cm, so really a flat wall speaker.

I also considered a double folded BIB design, but for the ease of building, I ended up with the following straight TL design:

You can see a screenshot of the design below:
View attachment 526238

Thanks!

Um, so a TL for an 8cm speaker with a 1.2M length..... LOL....
Have you considered the Vifantastisch?

VIFAntastisch ! Der Wandlautsprecher, Projekte der Nutzer / Eigenentwicklungen - HIFI-FORUM

J.

 

[GM]

This is the same as in post #18, so did you mean something else?: http://www.diyaudio.com/forums/full...n-line-speaker-how-calculate.html#post4589186

GM

 

[Jerms]

This is the same as in post #18, so did you mean something else?: http://www.diyaudio.com/forums/full...n-line-speaker-how-calculate.html#post4589186

GM

D'oh! Nope, missed that one.

I caught on to the flat and 1.2M line length and posted too quickly.

At this point the OP has started playing with the software and formed an opinion so I thought no impediment to providing links to already invented there design.

J.

 

[Schlumpfpeter]

Um, so a TL for an 8cm speaker with a 1.2M length..... LOL....
Have you considered the Vifantastisch?

VIFAntastisch ! Der Wandlautsprecher, Projekte der Nutzer / Eigenentwicklungen - HIFI-FORUM

J.

Yes it seems a little bit overdosed, doesn´t it? But it is just for fun with minimal effort, so let´s do this!
The interesting thing is that I modeled the speaker and than found out that there is a similar design already existing, which is the Vifantastisch, you mentioned.


GM thanks again for your input, so let´s hear how they sound!

 

[Jerms]

Mine are currently taking shape in 5mm foam core. Will have the odd bit of ply/hardboard (speaker mount reinforcement) and possibly some aluminium bituminous flashing tape (panel damping).

J.

 

[Schlumpfpeter]

I will not use the hardboard, I think I will glue the speaker to the foamcore board but I will make this decision when I build them (so maybe tonight).

I will post some pics soon!

 

[Schlumpfpeter]

hi!

I have finished the build

The sound is very open, neutral and very impressive for the size of this tiny driver. It can do some bass as well! No subbass of course, but definitely something below 80hz. I can highly recommend this one.

Measurements:

Din A3, 60cmx40cmx7cm
TL 120cm tube, folded one time
Transmission line wall in the center of the speaker is 20 cm long
The opening is 20 cm wide.
Material is 1cm Foamcore board, this means that the room inside of the speaker is 5cm deep.

If you want to build this one, please use only half of the insulation I used... only use the insulation areound the driver, I used to much on the picture.

Enjoy!

Fotos attached!

 

[Schlumpfpeter]

Edit: The transmission line wall in the middle of the speaker is of course not 20 but 40 cm long!!!!!!

 

[Jerms]

I forgot the flashing tape in a rush of enthusiasm. It might have added an extra layer of dampening around the driver and on the back panel.

I'm beginning to quite like them. They are completely different to my Tannoy E11s though. Much less weight and bass and quite bright with the wrong material - e.g. Catatonia or Meatloaf.

I nearly stated your TL wasn't 120cm.... But it is.

J.

 

[GM]

The sound is very open, neutral and very impressive for the size of this tiny driver. It can do some bass as well! No subbass of course, but definitely something below 80hz. I can highly recommend this one.