[hotjt133]

Long time lurker.

A few years ago I purchased N3 from GR and built the transmission line enclosure designed by Danny. Very solid design and still enjoy them.

Now I had a chance to acquire a pair of vintage 12" full range drivers in mint condition (50 years old Rola, a piece of Australian legend BTW). Initially wanted to sell it, but the more I listen to them (in the open), the more I enjoy them! So now I withdrew the sale and decide to build a proper enclosure. Here's the thread if you're interested.

http://www.stereo.net.au/forums/index.php/topic/93781-fs-a-pair-of-vintage-rola-12ux-12-full-range-driver-warning-picture-heavy/#entry1503690

Are these old drivers suitable for transmission line? Or just a ported one? I ask this since I believe Danny is good at TL designs.

[Danny Richie]

Long time lurker.

A few years ago I purchased N3 from GR and built the transmission line enclosure designed by Danny. Very solid design and still enjoy them.

Now I had a chance to acquire a pair of vintage 12" full range drivers in mint condition (50 years old Rola, a piece of Australian legend BTW). Initially wanted to sell it, but the more I listen to them (in the open), the more I enjoy them! So now I withdrew the sale and decide to build a proper enclosure. Here's the thread if you're interested.

http://www.stereo.net.au/forums/index.php/topic/93781-fs-a-pair-of-vintage-rola-12ux-12-full-range-driver-warning-picture-heavy/#entry1503690

Are these old drivers suitable for transmission line? Or just a ported one? I ask this since I believe Danny is good at TL designs.

I'd really need to see some parameters to really be able to recommend applications.

I'd also advise for you to be careful with them and not play them too hard. The suspension and surrounds on a 50 year old driver might not last long if played hard.

[hotjt133]

Thanks Danny. Glad you asked this!

These speakers were made before Thiel and Small published the theory, so it is impossible to find the T/S parameters. Here's my measuring results:

Fs: 47Hz
Qms: 3.75
Qes: 1.06
Qts: 0.83
Vas: 173.22 Ltr  (using added mass method so won't be very accurate)

Cone Diameter: 265mm
Coil resistance: 13.98 Ohm

I tried a few online calculators and it seems this driver's Qts is too high. Some suggested a volume as high as 1500-1800Ltrs! That would be a room sized box. So now I'm at a dilemma that T/S would have little use if my box is significantly smaller than suggested.

My thought of the transmission line enclosure was inspired by the pictures of IMF Studio Monitor.
http://www.imf-electronics.com/Home/imf/speaker-range/reference-speakers

Its front baffle has 2 square holes which looks exactly like the front baffle where my Rola was installed. I can only suspect the original enclosure has a similar TL design like the IMF, but unfortunately it is impossible to find the original box. All I can salvage is the front baffle. This baffle is 69cm x 39cm, so the box would be in the 80Ltr range.

[Danny Richie]

The parameters of that driver suggest it was made for open baffle applications.

[hotjt133]

So why the original baffle has 2 square holes? (please check the second last photo on the sales thread)

[Danny Richie]

So why the original baffle has 2 square holes? (please check the second last photo on the sales thread)

Pictures from Stereonet don't open for non-members.

[hotjt133]

Sorry, forgot that. Here're some pictures:

http://imgur.com/a/btFlQ

[JLM]

Looks like they came out of a hi-fi console.  The holes made have been for non-acoustically related purpose. 

They look to be well made and in great shape.  Definite candidate for open baffles IME. 

[Danny Richie]

Keep in mind that 50 years ago they packaged these in a way that they could sell them. They used large un-braced boxes with a couple of vents in the end.

The parameters are ideal for an open baffle design. So we can help you build something ideal for that application.

Still I would not advise playing them real hard.

[hotjt133]

Thanks guys.

So open baffle that is! Do you have suggestions on the baffle size? Or I just use the current one by installing 2 support legs?

I have to admit the bass is really weak for a 12 incher. When I measure the Fs, 47hz is the highest impedence, however all I can hear is not the usual 50hz hum, it was like continues clicks.

I was even thinking of adding a 80hz high pass filter to prevent low frequency damage. Any suggestions?

[persisting1]

I was even thinking of adding a 80hz high pass filter to prevent low frequency damage. Any suggestions?

Get a set of Danny's servo subs and cross them over at 200hz. 80hz might even be a bit too low.

[Danny Richie]

Thanks guys.

So open baffle that is! Do you have suggestions on the baffle size? Or I just use the current one by installing 2 support legs?

I have to admit the bass is really weak for a 12 incher. When I measure the Fs, 47hz is the highest impedence, however all I can hear is not the usual 50hz hum, it was like continues clicks.

I was even thinking of adding a 80hz high pass filter to prevent low frequency damage. Any suggestions?

The baffle size needed for a 12" woofer gets you about 3/4 of the baffle width that you need. You can add the additional baffle width by making a wing down one side. And the depth of the wing will help determine the -6db down point or crossover point.

Because the baffle is pretty wide you can use two very short side wings of a couple of inches (two to four inches) on each side. They can't get too deep though. The driver will likely play up into the top octave and you don't want to enclose the space too much or you will set up a cavity resonance back there.

You can do a little shorty wing then a longer one too.

With the Super-V design I made two short wings that tapered top to bottom. That worked out pretty well too. See pics:  http://www.audiocircle.com/index.php?topic=73341.0

And adding a high pass filter to keep it from ever seeing lower frequency range signals is a good idea. I'd go for a single capacitor in-line filter on the RCA input of your amp.

[hotjt133]

With the Super-V design I made two short wings that tapered top to bottom. That worked out pretty well too. See pics:  http://www.audiocircle.com/index.php?topic=73341.0

I can never do these nice curves. What do you think of a straight triangle side wing like this (forgive my poor drawings): from top 0 to bottom 10cm, perpendicular to front baffle?

http://i.imgur.com/jF60klw.jpg

[Danny Richie]

I can never do these nice curves. What do you think of a straight triangle side wing like this (forgive my poor drawings): from top 0 to bottom 10cm, perpendicular to front baffle?

http://i.imgur.com/jF60klw.jpg

Yeah, you can do that. Just try to minimize the surface area of the front baffle to the top and sides of the driver.

And your side wings can be a little deeper than that.

[mlundy57]

The Wedgies have roundovers on the inside edges of the side wings (don't know about the super V's). Would that also be a good idea with this shape of side wing?

Mike

[Danny Richie]

The Wedgies have roundovers on the inside edges of the side wings (don't know about the super V's). Would that also be a good idea with this shape of side wing?

Mike

It wouldn't hurt, but these wings will be so far away from each other that it might not have much effect if any.