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My FR125S project is finally done!
My FR125S project is finally done!
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Old 13th November 2005, 12:01 PM   #11
Geek is offline Geek
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Ok, some stuff measured before going to work tonight and more detailed Xmax measurements.

A testament to WinISD Pro, the curves only differ by a small amount from design.

I believe I can answer this too - the foam in the ports appear to have effectively lengthened them by 12.8%.

Basically I took the curve from a sweep generator and a FFT, then altered the params to match the resulting curve. The only thing that changed, was port length. That is how I draw my conclusion.

I will also say that my setup was nowhere near professional. The mic used however, was designed for a kick-drum/Tom pickup and is nearly flat from 25Hz to ~800Hz, where it then becomes the "Rocky Mountains" for response (hence, I didn't bother with > 1KHz).

The Xmax curves were measured with a slow sweep and a white dot on the speaker.

Those curves were accurate enough to match the predicted response, but the program says 3.8W, while I measured about 7W in real operation.

Funny thing about the source at 8 ohms, since I measured it on my Sony sand-state amp, not a tube one

Suffice it to say, it appears WinISD Pro is within 3dB of real-life measurements in this instance
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Old 22nd November 2005, 06:56 AM   #12
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My final test with these speakers was with my prototype CV4060/S11E12 in the configurations of SE trioded and boosted triode. No problems what so ever at all power levels.
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Old 22nd November 2005, 07:07 AM   #13
eVITAERC is offline eVITAERC  Canada
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May I know what program/procedure you're using to measure the freq resp. and plot the transfer function in the above screenshot?
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Old 22nd November 2005, 07:43 AM   #14
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The procedure was posted, but here it is in more detail.

Xmax was determined with a little white sticky dot on the cone and I measured the length of the "blur". It was close enough to the WinISD curve, that I used a screenshot of it.

Frequency response was measued with a microphone 1M from the speaker and the amp at 1 watt, with a slow sweep (also from WinISD) inputted. Since I do not have an anechoic test chamber, the area was dampened with quilts. The mic went into the soundcard and was displayed on a FFT. I went back into WinISD and was able to duplicate the FFT response fair precisely and determined the only seeming change in the params was port length.

As mentioned, the microphone was an Aiwa (model # worn off) for bass percussion and is fair flat from 25 to ~800Hz.

I have gone out and purchased a nice mic to measure the mids and highs. Any further test results will be posted on my forum. I just wanted to dispel any myth that the FR125S was tube unfriendly
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