i have measured azura horn from the mouth, 1.2m, 1.5m, 2.4m there are no differences.
im using omnimic v2, gate at 4-6msec and in room.
How you measure effectively depends on purpose of measurement. What may seem wrong for onne purpose could be a problems solver for another. Data interpretation is important and dependent on where the mic is placed.
The main purpose I have for near field measurement is to look at the low end of the upper woofer's response.
Here is a 416-8B in its sealed cabinet:
The curve isn't reliable above 216 Hz according to the protocol, but I don't see much going on until the periodic artifacts come barging in (multiples of 650 Hz).
Gary Dahl
Here is a 416-8B in its sealed cabinet:
The curve isn't reliable above 216 Hz according to the protocol, but I don't see much going on until the periodic artifacts come barging in (multiples of 650 Hz).
Gary Dahl
Looks like there is something going on below 250 Hz since there is generally a gradual roll off before the cutoff. I wonder if this happens in an open frame or not? Could also be the cone is not acting in total piston mode.The main purpose I have for near field measurement is to look at the low end of the upper woofer's response.
Here is a 416-8B in its sealed cabinet:
The curve isn't reliable above 216 Hz according to the protocol, but I don't see much going on until the periodic artifacts come barging in (multiples of 650 Hz).
Gary Dahl
Gary,
I assume from the curve this is a sealed box, but at the same time it appears that it must be rather small in internal volume as I would think you would have more extension on the bottom end but the nice smooth rolloff of a closed box. How small is that box?
I assume from the curve this is a sealed box, but at the same time it appears that it must be rather small in internal volume as I would think you would have more extension on the bottom end but the nice smooth rolloff of a closed box. How small is that box?
Nice Curve
Gary,
Thanks for posting. That's a real nice curve and a bit better in the bass than what T/S predicts.
I'm several weeks away from [also] using a 416-8B for an experimental mid-bass. Also using 3 cubic feet, sealed.
The frigid cold weather here in the land of Dixie is happering my progress.
A good friend of mine also uses the same Altec driver in his system. I'm looking forward to hearing that "Altec sound".
Gary,
Thanks for posting. That's a real nice curve and a bit better in the bass than what T/S predicts.
I'm several weeks away from [also] using a 416-8B for an experimental mid-bass. Also using 3 cubic feet, sealed.
The frigid cold weather here in the land of Dixie is happering my progress.
A good friend of mine also uses the same Altec driver in his system. I'm looking forward to hearing that "Altec sound".
As the legend at the bottom of my graph indicates, the measurement was made in an 85 liter sealed box (minus the internal bracing), stuffed with Bonded Logic UltraTouch recycled cotton insulation. The results are pretty close to the sims, and give a pretty clear picture of where the lower woofer should come in. Earlier measurements showed the stuffing's strong effect on system Q, so it would be easy to bump it up a bit by removing some of the stuffing.
I'm not at all concerned about the minor blips in the curve; the woofer sounds fantastic.
Gary Dahl
I'm not at all concerned about the minor blips in the curve; the woofer sounds fantastic.
Gary Dahl
Thanks, Gary, for the nearfield measurement of the GPA 416 Alnico in the 3 cubic foot box with UltraTouch recycled-cotton filling. Looks pretty close to the simulation results.
POOH, if your only contribution is to insult other posters, please leave this thread and do not return.
POOH, if your only contribution is to insult other posters, please leave this thread and do not return.
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In the interest of providing context, I am using a small sealed box for the 416 (85 liters, or 3 cf) because the 416 is only for the 80 Hz - 800 Hz region. Lower frequencies are covered by the bass woofer, a TD15-H in a 5 cf box with PR loading, which is powered by a plate amp. Eventually the plate amp will be replaced by a DSP unit and separate power amp.
I used TD15M's in the sealed upper boxes for 3 years. They were -3dB at 75 Hz in this application. Replacing them with 416's brought down the -3dB point just a little, but the musical effect was much more significant than the measured differences. I was at first concerned that the Q would be too high with the 416's, but once the stuffing is added, it seems just about right.
Using a larger sealed enclosure would certainly yield deeper bass from the 416. Critical damping (Q = .707) is reached at about 5 cf, -3dB at 54 Hz, so it would still require augmentation.
Gary Dahl
Who did I insult? My last comment was based on measuring several horns "at the mouth" and at various other distances. The horn cannot measure the same at the mouth as it does in farfield or even at 2.4 meters. There are several reasons why. The fellow that made that statement is welcome to show his measurements at the mouth and at a distance and so are you with your horns. My point is the horn sellers that advertise their performance should take them outside and measure them at a distance that they will be listened to - not "at the mouth" or "in the mouth" - sure there is a reason to measure them up close but that should be important to the designer with a particular driver not poor the person that buys the horn based on something that is pretty much meaningless to them.
Wasn't the question about 0 cm versus 100 cm? Not 120 to 160. No one would expect much change in those distances.
yes, i didnt save the 0cm, but its exactly the same, i think martin's measurements was at 0cm.
well you can see that its very flat 😀
At a 30 cm difference it doesn't measure the same. What I'd like to see is "at the mouth" and at 2.4 meters or further (how close do you listen to that normally?) how about 3 meters and at the mouth if you have it _henry_
Thanks
the horn is not with me right now, considering the horn diameter is 600mm, wouldnt any measurements above 120cm would be acceptable?
and no one measures speakers at their listening position, the room interactions will add to the graph no matter how much gating you applied.
as you know i dont have anechoic chamber 😛, but if anyone interested for further measurements ill be glad to do some again this weekend or the next.