Hi,
You can measure at whatever distance you like, e.g. in room very near for
the bass end, but to get the sensitivity of your displayed response correct
it has to be normalised to be correct at one metre.
For responses taken with a calibrated system at further or less than 1m
the drive voltage is increased or reduce to be equivalent to 2.83V@1m,
e.g. 2.0V@0.5m, seen quite a few tweeter curves done this way.
rgds, sreten.
You can measure at whatever distance you like, e.g. in room very near for
the bass end, but to get the sensitivity of your displayed response correct
it has to be normalised to be correct at one metre.
For responses taken with a calibrated system at further or less than 1m
the drive voltage is increased or reduce to be equivalent to 2.83V@1m,
e.g. 2.0V@0.5m, seen quite a few tweeter curves done this way.
rgds, sreten.
Custom inwall speakers arent that common but factorymade speakers like genelec do exist. But there are atleast hundreds of studios without inwall-speakers on every studio that has inwall-speakers.
About consoles, the whole business is changing thanks to both protools and internet. One studio i know of has a harrison 2824 console connected as a summingbox in the machineroom, while all mixing is done on the computerscreens in the controlroom.
Internet has also made a great impact on the workflow, people today are tracking in several different places, then it is sent thru email to a engineer that mixes it in his own controlrom with whatever gear he prefers to have.
-Then, about gear vs knowledge... it is not the gear but the knowledge that limits most people.
PS: Today i and my solderingiron has a "date" with a NEVE 8108 😉 Next week we have a lot of work to do with a Neotek elite that needs to be installed in a new studio...
Yes, and for JA's quasi-anechoic measurements he uses 50 inches. I believe he explains why in the series of articles he wrote about how he does measurements.
IMO, there are a few good reasons.
1. Stated earlier, re. efficiency tests at 2.83V for 8 ohm nom. speakers
2. The lobing characteristics of spaced drivers on a BB will be 'melded' together into a cohesive wavefront at the point of measurement
3. It's a compromise between 2 and minimizing room reflection effects that tend to become elevated beyond 1M.
That's too bad. It should have more to do with the consumer and less to do with the graphs, no? Silly me always thinking about the purchaser rather than the seller.
How the speakers will sound varies with the listening environment. The key to predicting that performance is analyzing the characteristics of loudspeaker and room separately. Please read Toole's book -- the correlation with a metric based upon anechoic or quasi-anechoic measurements is very high.... 
Doesn't have to be hours, you can use minutes, seconds or even light years, if you wish. Given that in different parts of the world there have been traditionally different weights and measures used, it seems the common use of time has been acceptable to most, as the speed of the Earth's rotation is a reliable constant. You could use Rods and Chains per hour, kilometers per hour, Cubits per hour, or even Terry's tree branches per hour.
On ships, there is speed (in knots) through the water, and perhaps even more important, speed over the bottom. One is important to estimate fuel consumption and the other will give you an estimate of how far you've travelled and how far you must continue before reaching port. The era of long sea voyages under sail ushered in the vital need for extremely accurate Chronometers and in England a King's Ransom was offered for the first successful one to be invented. Latitude (North/South position) had been easy to estimate and has been practiced since antiquity, but the calculation of Longitude (East/West position) called for a method of keeping track of the time at some fixed position on the Earth.
I'm sure our friend "Scottmoose" can elaborate, or even correct if need be, what I've already mentioned.
I just realized that I've gone on for too long and am guilty of wasting your "Time."
😀
Best Regards,
TerryO
Speed can be measured in any units of length and time you like.
And with modern technology it really doesn't matter what units you use, the values are easily converted. I'm still amazed (I guess I'm old and get amazed easily) that one can request the value of a universal constant in any set of units one can imagine, or type in just about any mathematical statement, and get the right answer to eight significant digits, almost instantly.
speed of light in furlongs per fortnight - Google Search
And with modern technology it really doesn't matter what units you use, the values are easily converted. I'm still amazed (I guess I'm old and get amazed easily) that one can request the value of a universal constant in any set of units one can imagine, or type in just about any mathematical statement, and get the right answer to eight significant digits, almost instantly.
speed of light in furlongs per fortnight - Google Search
More likely: Cubic yards of Blue Smoke per mile.
I measured mine (actually several) in miles per quart (of oil).
😀
Best Regards,
TerryO
If only 2 curves were available i would like to see
- sound pressure over frequency at 3m distance
under anechoic or free field conditions
- energy response (e.g. with rotating microphone in a
reverberation chamber)
- sound pressure over frequency at 3m distance
under anechoic or free field conditions
- energy response (e.g. with rotating microphone in a
reverberation chamber)
One meter is much more comfortable for fast calculations.
It is -6dB for each doubling of the distance so 2m,4m,8m,16m and so forth is easy to estimate without a calculator.
I was only joking about SI units. Everything can be measured in any unit you find convenient. But still we talk about HP, when it comes to cars although the official unit has been kW for years. And we talk about speed in km/h or you in mi./h although the official unit is m/s.
Did you know that only three countries in the world have not adopted the SI system? Guess which are the other two.
Which gives you a better impression of the actual speed?
"That car goes 55,6 m/s."
"That car goes 200 km/h."
"That car goes 124 mi./h."
The first one is especially interesting to know in the context of how far you travel during your reaction time before you can hit the brakes.
Did you know that only three countries in the world have not adopted the SI system? Guess which are the other two.
Which gives you a better impression of the actual speed?
"That car goes 55,6 m/s."
"That car goes 200 km/h."
"That car goes 124 mi./h."
The first one is especially interesting to know in the context of how far you travel during your reaction time before you can hit the brakes.
I guess you missed my reference to the thread
starter's question.
Since a (home) loudspeaker has frequency dependent
dispersion, i would - like cal weldon does - want
the frequency response to be measured at a distance
typical for (home) listening, since the 1m FR will
look very different to FRs at larger distances for most
speakers.
For estimation of a room dependent sonic result, i would
like the anechoic 3m measurement to be augmented
with an an energy FR.
Kind Regards
It will for line arrays, certainly. 😉
Frequency dependent dispersion has little to do with anechoic or quasi-anechoic on-axis response. Yes, measure at 2M, and there is more coherency in multi-driver systems and the measurement axis is less of a factor, but it's mighty tough to take full advantage of that distance in a confined space.... 🙁
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Excuse me Sir,
if you measure a typical 2-way at close distance
on axis and then go farther away under anechoic
conditions, the woofer beaming in the crossover
frequency range will cause the sound pressure to rise
in relation to the tweeter ... which is small compared
to wavelenght and has wider dispersion.
Every multiway speaker with non matched drivers
due to dispersion in the crossover range,
will have just one dedicated listening distance
where the FR of the direct sound is
without discontinuity.
- Wave guides,
- (frequency dependently weighted) line arrays and
- properly sized (open) baffles
are measures to overcome that problem if implemented
properly.
Not to mention panel form bending wave transducers,
which can also overcome the diameter/wavelength
dependent directivity of pistonic drivers.
Kind Regards
if you measure a typical 2-way at close distance
on axis and then go farther away under anechoic
conditions, the woofer beaming in the crossover
frequency range will cause the sound pressure to rise
in relation to the tweeter ... which is small compared
to wavelenght and has wider dispersion.
Every multiway speaker with non matched drivers
due to dispersion in the crossover range,
will have just one dedicated listening distance
where the FR of the direct sound is
without discontinuity.
- Wave guides,
- (frequency dependently weighted) line arrays and
- properly sized (open) baffles
are measures to overcome that problem if implemented
properly.
Not to mention panel form bending wave transducers,
which can also overcome the diameter/wavelength
dependent directivity of pistonic drivers.
Kind Regards
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One meter distance for drivers on IEC baffle provides a nice ratio minimizing baffle diffraction effects and far enough such that the response is close enough to normal listening distance. This distance also provides a very nice noise rejection capability. The value is easy to remember.
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