Small Thor ML-TL Transmissionline speaker project

[asliarun]

Hi Anil,

How are you measuring or calculating the driver brace depth so that it is an exact fit?

Thanks,
Arun

 

[Anil kumar]

wow anil,great goin!!!those drivers are very familiar indeed hyeah:!!!!am sure they will turn out beautiful,securamente!!!my exposure to DIY has been very limited,but the relative impact it has had on me..immeasureable.kudos and cheers

Thanks rallynut, you must have seen these drivers at sreekanth's place, thay are great performers

How are you measuring or calculating the driver brace depth so that it is an exact fit?

Hi Arun, i made a paper template after fixing the drivers. Driver depth was calculated from inside of the baffle to the end of the drivers magnet & the sketch was made on a paper, that i used as a template.

Lot of progress on weekend, holes on the braces were cut using jig saw, this job is pain in the neck :sad: As many as 80 holes were cut on the braces at the end of the day, this is the most tiring job in cabinet making :sad:
I was able to complete only one cabinet for testing, listening of the Small Thor will be done today. I will make final comments on the results after completing the second cabinet.


few progress pictures here......

Cutting the circular holes

Braces are ready to be fitted.........

Filled the upper half with DACRON fiber

 

[rallynut]

yeah anil,had seen them at sreekanths place.almost done??very nice indeed,and cant wait for your impressions.rock on!!!!cheers

 

[captrajesh]

few progress pictures here......

Filled the upper half with DACRON fiber

A Noob question. Is it ok to stuff the fibre without leaving any gap for air? (to enable backward movement of the cone)

 

[Anil kumar]

A Noob question. Is it ok to stuff the fibre without leaving any gap for air? (to enable backward movement of the cone)

Cabinet should be loosely filled, just enough to occupy the space, without tightly pack in, too much stuffing will really kill the bass. In transmission lines enclosures the rear wave coming off the woofer is routed along a path about the area of the woofer, and long enough so that the wave emerging from the othe end will reinforce the front wave. This is in the region where normally the woofer would begin rolling off. The line is heavily stuffed with dacron This forms a "low pass filter", allowing the lowest frequencies on through to reinforce the bass in that bottom octave. But higher up it is filtering enough to remove some or most of the first out of phase frequency range, and the higher you go, the better this works.



Regards,
Anil

 

[GeorgeO]

Excellent going so far.

 

[vivek.saikia]

Hi Anil,
Have you designed the crossover yourself or have got it readymade. If bought, then could you please share from where you have got it?

 

[gobble]

Mind boggling job with the holes!! 80 of them? One has to be an obsessive-compulsive disorder type of person go around poking so many holes in one day!

What is the axis around with your router rotates? Its not in the pic.

Cheers

 

[vivekphadnis]

Great work, Anil.
I too started a mass loaded transmission line speaker with Vifa TC18 drivers. But I have just cut up a MDF board but have not progressed further. I need to take inspiration from your work and finish my speakers.

Cheers,
Vivek

 

[Anil kumar]

Thanks George.

Have you designed the crossover yourself or have got it readymade

No vivek, designing a crossover is headache :sad: so i bought a ready made xover from sreekanth.

One has to be an obsessive-compulsive disorder type of person go around poking so many holes

Hi Rahul you mean to say i am a OCD patient??:lol:

No there was alternative, i had to cut 80 holes in one day. Carpenter asked me 10 bucks for each hole, so 10 Rs X 80 holes = 800 bucks :sad: you will get a new jig saw for Rs 1000

But i discovered recently that circular holes can be cut using HOLE SAW :yahoo: you get this in different sizes from 1 to 3 inch.

have a look:

What is the axis around with your router rotates?

It works like a sewing machine, blade moves up & down

Great work, Anil.
I too started a mass loaded transmission line speaker with Vifa TC18 drivers. But I have just cut up a MDF board but have not progressed further. I need to take inspiration from your work and finish my speakers.

Cheers,
Vivek

Thanks & all the best vivek, hope you complete it soon.


Regards,
Anil

 

[Anil kumar]

Hi all, after 3 day's of listening of the Small Thor i think i can now make few comments on the result.

The main objective was to get better bass out of the cabinet, after 6 hours of listening with NAD 314 & Pioneer SA 9100 amps, speakers sounded excellent with lot of bass, good mids & clar high's but the second cabinet was bass shy. After inter changing the bass driver it sounded like the first cabinet. Stuffing Dacron also plays a role here, i did experiment with it to see how much stuffing to use, to keep the bass reinforcement, but kill off the losses higher up. When i got one side working, i pulled out the stuffing & weighed it, and the same amount of dacron was stuffed in the other cabinet (approximately stuffed 300 grams of dacron per cabinet).

I played jazz, 80's disco & indian classicals, i am pretty pleased with result. Drivers are still new so they may sound different after burn in. I really enjoyed building this small thor, it is truly worth the effort.

I thank Scott Lindgren (Scottmoose) for the theory / design work, Dave Dlugos (Planet10) for the great drawings.

Regards,
Anil

 

[gobble]

Post a pic of the finished product please!!

Cheers

 

[rallynut]

great to hear anil,congrats.ur speakers are up and making their presence felt :licklips:.pics pls!!cheers

 

[kapvin]

I had been following this thread silently since it's inceptions.

My congratulations on your speakers, which are clearly the result of some great attention to detail! some questions -

could you share the T/s specs for your mid bass drivers?
what's the acoustic length of your line?
more qualitative - what made the choose transmission line over other alignments?

thanks in advance?
kapvin

 

[Anil kumar]

Thanks kapvin check this TSP measurement.

Special thanks to sreekanth for providing TSP.

could you share the T/s specs for your mid bass drivers?

Woofer size : 6.5
Motor : 120MM magnet with 8MM top and bottom plates
Polepiece : 31.5MM
Voice Coil : 32MM Dual Layer wound in 32Guage wire
Spider : 100 MM wide and 10MM tall
Cone : Air Dried with Rubberised Form Surrounds


Here's the TSP measurement....

First set of them without any hours on them (or max less then 1hr)

Re :6.8487
Fs : 47.3723Hz
Zmax :186.0971 Ohms
Qes :0.3228
Qts :0.3109
Qms :8.4475
Le : 0.7287
Vas : 25.8084 L
BL : 8.7027
Mms : 11.9917g
Cms :941.2622
Sensitivity :90.546@ 1M /1W

Second Test results after some brief burn-in using 25Hz Sine wave

Re :6.844
Fs : 47.42Hz
Zmax :186.72 Ohms
Qes :0.3244
Qts :0.31
Qms :8.5251
Le : 0.7287
Vas : 25.8084 L
BL : 8.82
Mms : 12.398g
Sensitivity :90.88@ 1M /1W

After 5 Hours of 25Hz sinewave !

Re :6.88
Fs : 43.8792Hz
Zmax :177.1931 Ohms
Qes :0.3000
Qts :0.2883
Qms :7.4175
Le : 0.7308
Vas : 26.9775 L
BL : 9.2001
Mms : 13.3713g
Cms :983.8979
Sensitivity :90.546@ 1M /1W

what's the acoustic length of your line?

48 inches

what made the choose transmission line over other alignments?

TL have an open, non-boxy sound produces a deep, well-controlled acoustic bass compared to bass reflex design.


Speakers are almost complete, metal spikes will be added soon & veneering will be done next month.

 

[avidyarthy]

Mindblowing stuff ............................

 

[avidyarthy]

And please elucidate on the other brushed-alum and black boxes .... seen on the pic ....

 

[kapvin]

Anil,

your speakers are looking really good! have you thought about what finish you'll give them?

thanks for the answers as well..

IMHO your drivers are well suited to a TL alignment and doing quite well after even the appreviated burn in. do again check the t/s after a 100hrs or so.

just wondering.. what is the speed of sound through polyfill? coz in open air your line length corresponds to a qtr wave of 68hz.. did you perchance calculate that?

also is that a pioneer DV-525 I see? brings back old memories!

cheers

kapvin

 

[Anil kumar]

And please elucidate on the other brushed-alum and black boxes .... seen on the pic ....

They are my vintage amp collection black box what u see is my first DIY floor standers made in 2006.

Have a look............

​

 

[Anil kumar]

Thanks kapvin.

Most likely it will be cherry finish, Mahogany also looks beautiful. I am getting the spikes machined next week.

I do not know to calculate speed of sound through of Dacron, pls throw some light on it.

The long wool fibers generally better at attenuating than Dacron at low frequencies, even fiberglass have much smaller fiber diameters and much better attenuation at high frequencies. It's hard to find long fiber wool here but fiberglass is a nasty stuff to handle.


Regards,
Anil

Anil,

your speakers are looking really good! have you thought about what finish you'll give them?

thanks for the answers as well..

IMHO your drivers are well suited to a TL alignment and doing quite well after even the appreviated burn in. do again check the t/s after a 100hrs or so.

just wondering.. what is the speed of sound through polyfill? coz in open air your line length corresponds to a qtr wave of 68hz.. did you perchance calculate that?

also is that a pioneer DV-525 I see? brings back old memories!

cheers

kapvin