I've got a pair of rola 12px speakers.
All I know is they are full range and rated at about 20W.
Seller claims that they require a 12 cubic foot capacity cabinet, but that feels awfully huge!
Also wanting to know if they require vented or sealed cabinets?
I'm assuming that I can get the cabinet size right down if I stuff them full of dacron?
Either way they are a nice 12 inch speaker that should go well with a tube amp as they are 5 ohms impedeance.
All I know is they are full range and rated at about 20W.
Seller claims that they require a 12 cubic foot capacity cabinet, but that feels awfully huge!
Also wanting to know if they require vented or sealed cabinets?
I'm assuming that I can get the cabinet size right down if I stuff them full of dacron?
Either way they are a nice 12 inch speaker that should go well with a tube amp as they are 5 ohms impedeance.
Attachments
Without specs we can't tell anything. And as this is an old driver, you need to measure it because the specs changed over time.
Hence why I'm asking here, I thought rola should be common enough to have specs well published, but I cant find any.
Don't know what you mean my specs changing over time, but I plan to get the alnico magnets regaussed.
Don't know what you mean my specs changing over time, but I plan to get the alnico magnets regaussed.
They are not, they are common in australia, but most use them for open back guitar amps. But T/S parameters, like we need to answer your question, are not known.
And old speakers change specs over time because of the material aging of the voicecoil and other parts. So published specs are never accurate. And these speakers are from a time before T/S parameters were known, so they are never published by the company that made them.
And old speakers change specs over time because of the material aging of the voicecoil and other parts. So published specs are never accurate. And these speakers are from a time before T/S parameters were known, so they are never published by the company that made them.
Interesting you say that, the company started in the US and set up business in the UK, Australia and New Zealand.
The NZ Vintage Radio Project - Rola
I don't know much about t/s parameters, but it looks like they were a thing as far back as 1961, and these are stamped 1963.
They would have had to have published some data on cabinet sizes surely?
How else would anyone know what size to use?
I've attached a datasheet I was sent, but it doesn't mention anything about cabinet size.
As far as any changes in performance over time, thats irrelevant to me, as no one tweaks their speaker cabinet volume to compensate with age!
I plan on replacing the cones and voice coils eventually anyway, as the paper is getting a little tired around the edges.
The NZ Vintage Radio Project - Rola
I don't know much about t/s parameters, but it looks like they were a thing as far back as 1961, and these are stamped 1963.
They would have had to have published some data on cabinet sizes surely?
How else would anyone know what size to use?
I've attached a datasheet I was sent, but it doesn't mention anything about cabinet size.
As far as any changes in performance over time, thats irrelevant to me, as no one tweaks their speaker cabinet volume to compensate with age!
I plan on replacing the cones and voice coils eventually anyway, as the paper is getting a little tired around the edges.
Ok, it looks like it was something worked on starting in 1961 and contributions made by several people over the years with a final revision in 1981.
Either way, none of this really helps me.
Any idea what size box I should build?
No, but I'm guessing it would need to be huge unless you're doing an open backed box, or an open baffle, based on similar drivers from this era that have a huge Vas. Only way to fine out would be to measure them.
jeff
I'll bite, as a reference point, I have a pair of early 60s' full-range 12 " vintage speakers...Argentinian manufacture, "Leea 1222XE drivers, a full-range twelve inch, (look it up) in a factory cabinet. Without the instrumentation to measure the performance $$$, we'll take a WAG (wild *** guess).
Let's try with my dimensions, twenty inches wide, twenty inches deep, twenty eight inches high...Now, I would get a five to six inch PVC piping for porting, cut several lengths from five inches to say, eighteen inches & install them one at a time...maybe run a frequency generator, sweeping from 25 to 100 hertz & listen...listen for a smooth response, no giant peaks or valleys.
-----------------------------------------------------------------------Rick.........
Let's try with my dimensions, twenty inches wide, twenty inches deep, twenty eight inches high...Now, I would get a five to six inch PVC piping for porting, cut several lengths from five inches to say, eighteen inches & install them one at a time...maybe run a frequency generator, sweeping from 25 to 100 hertz & listen...listen for a smooth response, no giant peaks or valleys.
-----------------------------------------------------------------------Rick.........
Last edited:
Right, by the '60s, drivers were generally designed to be interchangeable across many manufacturer's cabs and the 12 PX's published specs falls 'close enough' in line with the then theoretical ideal reflex alignment of Fb = Fs when the port area [Av] = driver piston area [Sd] and since drivers were mounted behind the baffle, its cutout area was [Sd], so per this chart its 50 cps would be between 11-12 ft^3 with a [10-29/32"^2 *pi]/4 = ~93-7/16"^2 port.
Using HR to fine tune it to 50 cps [normally fine tuning was done empirically], we get an 11.53 ft^3 net with the then common 5/8" thick baffle: http://www.lansingheritage.org/images/altec/plans/1960's-lf-design/page03.jpg
Obviously, as box size shrinks the higher in frequency above Fs it will begin rolling off with increasing peaking.
Vented or IB.
Well, it will reduce an acoustically small cab's peaking, though based on the chart, getting much, if any, bass out of a < ~4 ft^3 cab with a 50 cps driver is unlikely, assuming it's anywhere near that after all these decades unless used regularly.
Ok, that's interesting, and backs up what the seller said.
He had them in a 6 cubic foot box and said you could get it smaller if you stuff it full of dacron/polyester.
I was hoping I could get away with a 4 cube cabinet, as anything larger is getting to the size of a small fridge!
I got them at a good price and thought they would be perfect for a tube amp, since older speakers are much more sensitive.