The Talking Machine Forum — For All Antique Phonographs & Recordings

Uncle Vanya wrote: You wouldn't happen to have a spare tone arm for an Edison C-4, would you? I do have a pickup, bit wouldn'tt mind another.

Bob,
Sorry I only have one C-4 tonearm left and I use it to test pickups I restore. I have a Lenco variable speed TT that I attach various arms to depending on which pickup I'm working on.

I'll keep an eye out for you.

Chuck

Chuck, can you please tell us by what means you are measuring and plotting frequency response? It's a super interesting pursuit and surprising (to me, at least) that it hasn't been done more thoroughly on our old phonographs.

Do you measure via direct electrical connection to the outputs, or via microphone to also account for the characteristics of the original old speakers? And if by mic, how do you factor in the mic's characteristics?

There's a guy, John Levin, who has spent a bundle of money creating a special cylinder player. Very hi tech, and an awesome achievement. I saw and heard it at the CAPS meet in LA last summer. He made frequency response claims for it that were certainly held up by the demos, but upon asking directly we learned that those numbers were calculated, not measured. And even more frustrating, he only had an estimated high end number but nothing for low frequencies.

He's going to give his presentation at Union this year. It would be great if you guys could somehow connect and find a way to extract real performance numbers for his extraordinary system, unless he's already managed to do so in the meantime.

PeterF wrote:Chuck, can you please tell us by what means you are measuring and plotting frequency response? It's a super interesting pursuit and surprising (to me, at least) that it hasn't been done more thoroughly on our old phonographs.
Do you measure via direct electrical connection to the outputs, or via microphone to also account for the characteristics of the original old speakers? And if by mic, how do you factor in the mic's characteristics?
There's a guy, John Levin, who has spent a bundle of money creating a special cylinder player. Very hi tech, and an awesome achievement. I saw and heard it at the CAPS meet in LA last summer. He made frequency response claims for it that were certainly held up by the demos, but upon asking directly we learned that those numbers were calculated, not measured. And even more frustrating, he only had an estimated high end number but nothing for low frequencies.
He's going to give his presentation at Union this year. It would be great if you guys could somehow connect and find a way to extract real performance numbers for his extraordinary system, unless he's already managed to do so in the meantime.

The plots that I have done are just the amplifier, from pickup input connection to speaker voice coil output connection. Lately I have been using an HP 35665A Dynamic Signal Analyzer which has built in source to generate a sweep response from 51.2Hz to 51.2KHz. Earlier I had done them manually using a signal generator and an AC voltmeter to plot data points.

Testing end to end gets a bit more complicated, on the output side you need a calibrated microphone and preferably a sound dead room, on the input side you need a source to drive the pickup. One method would require test records that would output a series of known tones and levels within the band of interest and use the real time ⅓ or 1/12 octave measurement mode of the analyzer to measure the output levels. Another might be a transducer that could be coupled to the pickup to drive the armature mechanically through the frequencies of interest.

I have played with the real time octave analyzer connected to the pickup to see what information was actually being output from the record/pickup combination, not easy to measure but I could see there wasn't much information above 5KHz just appeared to be noise. At some point I would like to try playing a record with a modern pickup with a known frequency response and be able to isolate what's recorded on the record from the limitations of the early pickup response.

Sound is very subjective, what sounds good to me, may sound bad to someone else. Numbers are good, but just because I measure a THD of an amplifier to be .05% doesn't mean it is going to sound the same (read good) to all listeners, because of where and which distortion products are generated in the output sound.

BTW, most of my testing has been on electric pickups and phonos.

Lot's of stuff to try, not much time to do it all.


Chuck

Hmm, very challenging for cylinders...it would be extremely difficult to create test records.

What sort of information can be gleaned by playing standard entertainment content into such a system? I'd imagine one could identify upper and lower cutoff points, where all material drops off definitively. Given enough varied inputs, perhaps band stuff to explore the bottom end and vocal or violin stuff for the highs, we could at least discern the limits of a system. This of course also depends upon the range of the recording system.

The in-between part would be harder but peaks and valleys might also present themselves after enoug varied material samples were played and measured.

I'm shooting in the dark here, so maybe none of this is worth anything. But I can tell you that there was definitely an audible extension of the top and bottom ends, plus a noticeable increased fullness of tone, in the cylinders John played. And this was everything from brown wax to late blue amberols. Bottom line is, there's more music on those cylinders than we can normally extract and hear.