Sometimes, medium Z drive, like 4 ohms actually sounds better. There are several reasons for this, one is the BL product of the loudspeaker. IF it is over-damped, then a higher drive impedance MIGHT improve the overall bass and even the overall sound. I found this out in 1964, (when most of you were young) with an Acoustic Research AR-1 loudspeaker, driven by a Dyna MK 3, 60W amp. (more later)
A good nastinessometer can be made of a source of powerful sinewave and resistor.Say, to test 100W amp on 8 Ohm load we need 100W of a sine wave and 100W resistor. Feed this signal to the output of the amp in question and see FFT plot there. It is revealing. Actually, how big the output resistance of the amp is, does not matter: it is not a dirt. What is a real dirt, is what the amp adds trying to compensate this sinewave. Some amps that in conventional measurements show perfect results add very nasty dirt due to their non linear and complex output resistances, even though they are very low. Adding say 0.5 Ohm resistor to output of such an amp makes it's output resistance higher, but more linear.
I thought that was what I said the little piston moves at a fixed frequency, they are intended for an absolute sensitivity at some low frequency. Most microphones behave in an ideal sense at low to 500Hz or so.
As I said $$$ software and hardware are not for the little guy, nothing would give me more pleasure than to give the average DIY'er the same capabilities for free.
I thought he drove a Bentley, I got rid of my Mercedes the tires were the least of the problems. We are an all BMW family now.
You are definately right, we did lots of experiments with the "wrong" impedance taps on the output. Rarely did the "right" one give the best overall sound.
Hi,
I don't think this much to help with nonlinearities I listed, which depend on voicecoil current.
Ciao T
I don't think this much to help with nonlinearities I listed, which depend on voicecoil current.
Ciao T
Don't feel too bad. The little diy guys still benefits from your input here.
Just speaking for myself, as I don't represent any groups larger than one.
ditto
mlloyd1
mlloyd1
Don't feel too bad. The little diy guys still benefits from your input here.
Scott, you are the person making the BIG money, these days. Jack is mostly retired. He laughs when we talk about 'big profits' from his audio efforts. For example, he gave Brian Cheney, about $10,000 worth of Bybee devices to put into his bigger loudspeakers that he showed at CES last year.
Brian thinks they sound great!
On the other hand, Jack Bybee likes to stay busy, and that is tough on a guy who is 82 years old, this month.
Over the years, he has helped me, my associate, Mike, and several others in building new products over the last 15 years, including a lot of AC power conditioners, a power amp (now under independent evaluation), and the new active Bybee power supply filters (separate company). What Jack actually makes himself to sell to his own clients across the world is completely separate, though I have more than a handful of them in my audio system. He just does that to keep himself busy. No kidding! Most here are kind of 'clueless' about Jack Bybee, and even me, and my actual position, economically. We both do audio, because we LOVE it, not because it is a big money maker for us. Jack's wife would rather that Jack quit making audio stuff, as there is little or no real profit in it. They have a separate fortune, based on product designs and company developments, made BEFORE he started doing audio about 15 years ago.
Brian thinks they sound great!
On the other hand, Jack Bybee likes to stay busy, and that is tough on a guy who is 82 years old, this month.
Over the years, he has helped me, my associate, Mike, and several others in building new products over the last 15 years, including a lot of AC power conditioners, a power amp (now under independent evaluation), and the new active Bybee power supply filters (separate company). What Jack actually makes himself to sell to his own clients across the world is completely separate, though I have more than a handful of them in my audio system. He just does that to keep himself busy. No kidding! Most here are kind of 'clueless' about Jack Bybee, and even me, and my actual position, economically. We both do audio, because we LOVE it, not because it is a big money maker for us. Jack's wife would rather that Jack quit making audio stuff, as there is little or no real profit in it. They have a separate fortune, based on product designs and company developments, made BEFORE he started doing audio about 15 years ago.
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As I have already said, impedance in series may help to some drivers, depending on their Q. But this is not a general rule. Secondly, it may help only to a single driver. If a resistor is put in series with complete speaker (with passive cross over), we inevitably get dips and bumps on speaker frequency response, as seen in Carry review. There might be some cure if speaker impedance was equalized by additional RLC networks.
Yes, the high output impedance of many tube amplifiers acts like tone controls, with unpredictable response, varying with every speaker used. If such sound is preferred, wouldn't it be more wise to design high quality tone control circuits? My hint is a Blowtorch preamplifier MkII (with tone control circuits). Let's discuss the design
Yes, the high output impedance of many tube amplifiers acts like tone controls, with unpredictable response, varying with every speaker used. If such sound is preferred, wouldn't it be more wise to design high quality tone control circuits? My hint is a Blowtorch preamplifier MkII (with tone control circuits). Let's discuss the design
Close. The Pistonphone nominal frequency is 250 Hz. The later ones have an electronic governor, the older ones something more primitive. They all offer a bypass as a battery test so you can speed it up. In the bypass mode you can use an external power supply to run it a slower speeds as well.
I agree the Praxis is pricey for a hobbiest ($1100 or so for now) but it has been the most useful of all my gadgets (except the scope). I have used it for everything from measuring jitter to multitone spectral contamination to the effectiveness of noise cancelling headphones. You can download the software for free and use some of its functions, impedance and pink noise, without the magic box. Another free, useful, but tricky to use outside of its narrow function range software package is RMAA. I used that to characterize mp3 FM transmitters.
I'm a big fan of really good inexpensive solutions. Kim Girardin will calibrate your microphone if it works like the Panasonic for a pretty reasonable fee. He compares it to a 1/4" B&K. A method for using a barbecue lighter to check a microphone would be pretty neat, certainly as a quick field check that nothing has gone south.
Scott,
As you well know there are two issues to microphone calibration. Sensitivity and then frequency response. The pistonphone is used to calibrated absolute level. Works brilliantly.
I also have the adapters to do the frequency response calibration based on a known voltage. That does require a calibrated volt meter that is calibrated over the entire frequency range of interest. The requirement is eased somewhat as it only needs to read sine waves of low distortion.\
The common Flukes are decent on true RMS but the accuracy actually has some range dependent issues!
The other good news is that externally polarized microphone capsules are pretty much so unchanging until you drop them. The last time I flew with my full kit, they offered to put it in the baggage compartment as the plane really was packed. I mention that it probably was worth more than the guy's house and he let me keep it as carry on.
OK so I lied, it probably was only worth the cost of a mid range automobile!
Now if you can design an easy to build and calibrated source that would be very useful. Of course even a spark gap should have barometric influences.
What is to me interesting is that virtually no one else doing large systems actually measures the results after it is done to the level required to determine if their design methods are accurate. The one exception that proves the rule is Acentech (formerly BBN) they actually do real honest and detailed measurements. There may be a few others, but they are the exception.
As you well know there are two issues to microphone calibration. Sensitivity and then frequency response. The pistonphone is used to calibrated absolute level. Works brilliantly.
I also have the adapters to do the frequency response calibration based on a known voltage. That does require a calibrated volt meter that is calibrated over the entire frequency range of interest. The requirement is eased somewhat as it only needs to read sine waves of low distortion.\
The common Flukes are decent on true RMS but the accuracy actually has some range dependent issues!
The other good news is that externally polarized microphone capsules are pretty much so unchanging until you drop them. The last time I flew with my full kit, they offered to put it in the baggage compartment as the plane really was packed. I mention that it probably was worth more than the guy's house and he let me keep it as carry on.
OK so I lied, it probably was only worth the cost of a mid range automobile!
Now if you can design an easy to build and calibrated source that would be very useful. Of course even a spark gap should have barometric influences.
What is to me interesting is that virtually no one else doing large systems actually measures the results after it is done to the level required to determine if their design methods are accurate. The one exception that proves the rule is Acentech (formerly BBN) they actually do real honest and detailed measurements. There may be a few others, but they are the exception.
John,
That is day one measurement stuff. A 6,800 hertz tone has a half wavelength of one inch.
ES
The spark is only for relative response, initial measurements show that with care in eliminating ALL reflections you can get a perfect point source emitter, sort of (but not) like a plasma tweeter there is no horn or other mechanical mechanism for all those little "wiggles" you see in for instance most real mics at high frequencies. Zeldovich simply gives the way to fix the shockwave thermal relaxation form of the spectra, the initial results were quite amazing for $10 and a sound card. It has other uses of course like plotting the diffraction of baffles and the responses of damping matierials.
Another feature of the IC barometer is that in gage mode the atmospheric pressure is removed.
This is fun stuff take it or leave it. You could build Salas' simplistic RIAA or buy the $60,000 one. Just finished the all FET phase splitter/differential out circuit for the article, .025% thirds only at 0dBu out, JFET's rule! (open loop of course and no matching required
)What do you expect, the middle B wrote THE book?
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