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Old 21st November 2007, 09:16 PM   #1
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Default Magnavox/Rola fullrange 8"

Hey all! I got two old FM026 radios recently, restored one and used the other as a display case for models ( it was pretty trashed.)

I got a nice amp86 out of the deal though It is now restored and in use in my main system.

Now I have these two 8" full range speakers that I don't know what to do with! They have AlNiCo magnets, 3/4" coils and a wizzer cone.

I tried them in my little 2 watt guitar amp and they sound wonderful, but they also sound AWESOME as mid/hi-fi speakers! They have a pretty loose surround, so the bass responce is pretty impressive for such old and small speakers.

The code on the back is 285307. The 285 says their Rola's. I don't know Rola date codes ( it would be nice if someone could point me toward some.)

I really like the sound of them, and they don't take hardly anything to drive them to decent levels. They will take about 10 watts before bottoming out. I want to build some cabinets for these, maybe transmission line loaded?

I wanted some opinions here, because I know that a lot of old console speakers were deisgned for open baffle types. I was thinking that a mid sized ( 3-4 foot tall) transmission line was in order. Maybe there are some fostex drivers that have similar Thiele-small's that I can input to get an approximate cabinet design in winisd?

I have pictures of the speakers if one wants.
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Old 21st November 2007, 09:55 PM   #2
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Post the pics.
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Old 21st November 2007, 11:03 PM   #3
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Click the image to open in full size.
Click the image to open in full size.

I am currently trying to calculate TSP's for them. So far I haven an FS of 61hz and a -3 of 54hz.
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Old 22nd November 2007, 01:32 AM   #4
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I am having difficulties calculating the VAS.

I do not have a sealed box to use so I am using the added mass method.

I am using Rod Elliots TSP spreadsheet, however in his article it says there are calculations given in it for calculating vas using mms, there is even a pic on the webpage, however in the spreadsheet no such entries exist.....


Here is as far as I have been able to get...

RE= 3.7 ohms
FS = 61.75 hz
RM= 14.06 ohms
Fh = 54.57 hz
Fl = 66.65 hz
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Old 22nd November 2007, 02:27 AM   #5
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I think something went wrong in my Vas Calculation because its showing a Vas of 5.648 liters...
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Old 22nd November 2007, 03:25 AM   #6
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Nevermind, I think I got the Vas right finally. It gives me a Vas of 94.439 liters... now to try and plug these into winisd.
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Old 22nd November 2007, 04:45 AM   #7
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ok so now I have full parimeters.

http://getchellaudio.googlepages.com/maggieplot.jpg

Here is my current graph and design for a 90 liter box. Kind of large for the bass responce it has don't you think? It rolls off pretty quickly....
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Old 22nd November 2007, 05:17 AM   #8
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I'm surprised the Qt is that low.

307 means 30 th week of year ending in 7, You'll have to use the context of the radios these came out of to decide whether it is 1957 or 1967.

dave
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Old 22nd November 2007, 07:08 AM   #9
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Quote:
Magnavox/Rola fullrange 8"
I love those old speakers

All your fault, Dave!
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Old 22nd November 2007, 01:35 PM   #10
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Quote:
Originally posted by ThSpeakerDude88

Here is as far as I have been able to get...

RE= 3.7 ohms
FS = 61.75 hz
RM= 14.06 ohms
Fh = 54.57 hz
Fl = 66.65 hz
Greets!

FYI, Fl, Fh is backwards. Regardless, when I punch these specs into my SS I get the kind of numbers that are a bit high, but more in line for radio drivers than a ~0.35 Qts:

Qms = 9.9646
Qes = 3.5588
Qts = 2.6223

That 90 L box is looking down right tiny now.

Anyway, your numbers are suspect since Fs should be equidistant between Fl,Fh = SQRT(54.57*66.65) = ~60.31 Hz.

GM
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