Room Response and Preference

[manoj.p]

Mahabartha - Final chapter.



Just about 14.7 pounds for every 1 sq. inch diameter of drive cone. Or if the cone is small enough, say about 1cm it should be about 1kg per sq.cm. Can a voice coil magnetic field exert enough energy to match that? Can the grand Utopia's driver with a magnetic coil of 34T.m. force factor move it? Very much so. Furthermore, there idea of vacuum enclosure for speakers already been patented and in market. They are known as Vacuumspeakers. They use springs to counter the atmospheric pressure to keep the diaphragm in suspension.

I don't mind the Nobel but I am not sharing with your scientists and audio engineers, ok? .:lol:

Considering the vacuum experiments where 24 horses could not open a vacuumed ball, my understanding is that one would need a hell of a power and way strong driver. Look at these experiments. Pressure Now in a normal discussion, why would I be talking about audio in vacuum or "no air resistance" if it needs such a special equipment. As for the vacuumspeakers patent, I looked it up and they are feeling up the back chamber with gas. Could not understand the whole thing but as I understand, it is partial vacuum, rest filled with gas.

Post 46 where you said



If the driver is not producing any movement at 4Hz then what are they measuring the impedance against? The graph is plotted Impedance vs frequency. It is rather too basic that I have no idea how else to explain to you because that would mean I have start from the very beginning from "How to draw a graph".

But then you don't understand anything about the impedance graph and asked that you are not seeing any frequency response graph so there could be any sound at 4Hz. They are NOT SPL chart. SPL chart means something else but sometimes we all make mistake and use it interchangeably.

No, I don't understand impedance but do understand that having impedance at 4 Hz does not mean there is an output at 4 Hz. I have seen tweeters showing impedance down to 10 hz. Can we extrapolate that tweeter having output that low? Afterall, when people look at output of a speaker, they don't look at impedance chart, they look at SPL chart. When speaker manufacturer talks about usable frequency range, they are talking about SPL at -3db points.

All these 30 over posts is related to your insistence that drivers cannot produce any frequencies below Fs. Which is wrong. They could produce way below Fs but rather inefficiently causing too much problem to the crossover design and distortion and amplifers.


If you still want a FR graph specifically and hope that will end the discussion. Go back to Trio15 TB and Duet15 TB Open Baffle Speaker - PureAudioProject and click http://www.tb-speaker.com/detail/1230_04/w8-1808.htm .

In that you would see both SPL and Impedance charts merged into one. The Fs of the driver is 45Hz. You could see that in the chart and also in the T/S parameters. Then look at the frequency response chart you could see the loudness is about75dB at 20Hz. Do you agree 20Hz is below the Fs 45Hz?. So does it mean that the driver is producing frequencies below Fs?

If you are still are still clueless about all these. Watch this video below and see how pros measure Impedance and frequency response. It is just one bust of sweep and you get everything from FR chart to Impedance. Pay attention to the word quasi-anechoic. Do you see how they cancel out room influence? (Strictly speaking anechoic chamber is not required for Impedance measurement).

Video APx Loudspeaker Production Test measurement - YouTube

More detailed explanation about T/S here. APx Impedance/Thiele-Small measurement - YouTube

These videos are from Audio Precision. They are the industry standard in audio analyzer.

That's all I have to say.

From my limited reading of quasi-anechoic measurements, do have limitations. Especially how much delay time they put to measurement. Quasi-anechoic may work for impedance measurement and other whole lots of test, but it does have issues with low frequency response and accuracy depends upon time delay. One has to do impulse measurement and that gives an idea how much delay to put. There is a reason big cos invest into anechoic chambers and also perform measurements outside, sometimes on ground planes or cranes.

Although I stand corrected on spl below Fs. No matter how low it is, or distorted, usable or not but it is an output. Take a tweeter, can we vibrate it at 100hz? yes. Can it have usable output? Questionable. Is it an output? yes.

So yes. I stand corrected. I have no problem accepting it.