In search of response/impedance charts for a PE buyout about 10 years ago... - diyAudio
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Old 11th May 2012, 08:23 PM   #1
mdocod is offline mdocod  United States
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Default In search of response/impedance charts for a PE buyout about 10 years ago...

Here's some pictures of the driver... Sold as 6.5" poly cone woofers, foam surround.

Click the image to open in full size.

Click the image to open in full size.

I have T/S specs but would really like to get some response charts to come up with a reasonable x-over. If anyone recognises these or has any ideas for a place to look for a response chart I would very much appreciate it.

Thank you and Regards,
Eric
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Old 17th May 2012, 05:17 AM   #2
mdocod is offline mdocod  United States
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Going to try for a bump
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Old 17th May 2012, 12:30 PM   #3
AllenB is offline AllenB  Australia
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Hi mdocod, sorry I can't help you with this. I wonder whether this is time to get yourself a mic, an MTM design could really use it
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Old 17th May 2012, 05:26 PM   #4
18Hurts is offline 18Hurts  United States
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I had that problem 2 years ago

An old pair of Cerwin Vega 3 way 15" woofer PA speakers and a wife that gave the "do something with these or I'll burn them" concept. Since I had no T/S parameters on the woofers, I tested them for Fs with my multimeter and a free frequency program from the net.

Knowing that the original cabinets were dual rear ported for 40Hz--it gave me a clue. Measured the cabinet and had around 2.9 cubic feet of space. Removed the two horns and crossovers which returned 3.6 cubic feet. Did the isobaric face-to-face trick with the woofers to hit "7.2 cubic feet" but they did not like to be sealed. Added 2 inches of plywood on the back and bolted on a 18" passive radiator. My Fs measurement was 33 Hz so I guessed I could push the passive down to 22 Hz and get it rather even when corner loaded. Very simple to change weights on a passive radiator than cut port tubes.

So that would be my advice to you, use a meter to determine the resonant frequency of the woofers--the point that you have the lowest voltage is the resonant frequency. Get one of those passive radiators that allow you to tune without removing the radiator--tune it until smooth and you're done. If your tuning is really high (say 80Hz) that means you'll need a larger box which can be calculated with ratios. You can tune it by ear by using a frequency sweep but a Radio Shack meter runs around $40, get the calibration correct charts from the web and test away.

My wild guess sub box does 20 to 40 Hz +/- 2dB after messing around with placement and the passive radiator weights. Tuning a sub box to the room works very well so get a sound meter and have fun with it.
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Old 19th May 2012, 12:37 AM   #5
mdocod is offline mdocod  United States
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Hi 18hurtz,

I already have T/S parameters for the drivers. The boxes are built to suit the drivers well IMO. I am looking for the driver response above ~200hz, not below

As AllenB said, might be time to start thinking about picking up a mic, on the other hand, I imagine for the price of equipment to get going down that route, I could pick up 4 dayton RS180's instead. We'll see, I'm not in a huge hurry to get this "solved."

Regards,
Eric
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