-I'm not qualified to really tell you how to best measure loudspeakers (or just drivers in cabinets).
I do this on a platform outside. (..to get a free-field condition). Surrounding noise outside can be a problem, as can just finding the space to do it.(..even then I typically use some rockwool on the ground around the platform.)
While I've also done this inside my home, I've never done that well. The exception might be book-shelf speakers on a stand and getting as a low (in freq.) a good 1 meter measurement as possible. THAT involved moving it away from all reflective surfaces in a similar manner to the test baffle approach. ..and usually required quite a lot of pillows around the stand.
I'd look to Kimmosto's guides on this technique.
I have read Kimmosto "VituixCAD_Measurement_Preparations_REW" and it's quiet complete about measurement in that case, so in theory I n this specific case I should raise the Woofer at half the eight between floor and ceiling and as far as possible from the wall to keep the time window as large as possible without reflection
As for the Tweeter and mid it seem if they are close together I could measure with the microphone pointing in the middle of the eight between the two, but to be safe I should get the right elevation for each
The theory it is great, but I am now thinking how I can practically do that.
At first if I measure the drivers in just the front baffle panel I can manage to balance that on the platform and build something that will fit the size of that baffle to be at the right elevation
but if after if I have a complete cabinet to measure at that eight it is another challenge as the whole thing is clearly out of balance if the platform isn't very large to balance.I'll thinker a bit and see what I can come-up with, I will not yet worry about building something that is adjustable yet to accommodate different sizes of baffle/cabinet
It's Ok that you can't help on that, you have done much already
I'll make a new thread and ask for help on that matter if need be.
I can do that for the eight but I don't trust myself on the off-axis moving the mic, I have already received a 32cm rotating plate on ball bearing that should help me with that, I'll screw that to two boards and mark the off-axis angles on it to help me with the precision.
-you could do it with the rotating plate effectively on the "ceiling" with an extension out (meter + mic. & boom) for the stand "inverted/up-side-down". Center of the rotating plate with a plumb-bob & string hanging down to tweeter for centering (and removed afterward for measuring).
If you don't need it to go out much more than 90 degrees then you could make a stand with the rotating plate under the stand (not connected to the stand), but with the rotating plate's center in-line with the loudspeaker's tweeter as the loudspeaker is placed on the stand.
BTW, I typically just used the mic./boom/stand with a string attached to the boom where the length of the string was 1 meter from the end of the mic. heading-out to the loudspeaker (plus the distance on the boom to the vertical stand). Stretch it out to the tweeter when you need the correct distance (and let it flop back to the floor when measuring). It is tedious though.. (and I wasn't doing a lot of off-axis measurements).
-of course that's just horizontally.
If you don't need it to go out much more than 90 degrees then you could make a stand with the rotating plate under the stand (not connected to the stand), but with the rotating plate's center in-line with the loudspeaker's tweeter as the loudspeaker is placed on the stand.
BTW, I typically just used the mic./boom/stand with a string attached to the boom where the length of the string was 1 meter from the end of the mic. heading-out to the loudspeaker (plus the distance on the boom to the vertical stand). Stretch it out to the tweeter when you need the correct distance (and let it flop back to the floor when measuring). It is tedious though.. (and I wasn't doing a lot of off-axis measurements).
-of course that's just horizontally.
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Mounting something heavy on the ceiling here is not possible and I wouldn't start, but other wise it could be nice
The string is a nice easy solution to rotate the mic around, but with the number of off-axis involved I'll stay on a turntable, I have read a table like that was called a Lazy Suzan, I am not called Suzan but otherwise it fit me
As for removing the back of the Radian I put myself to it and they where not that difficult to remove once you start cutting, I got carried away and I did the two.
I'm happy to see that the blackface is the same design as front face inside, so I suppose when they do open back at Radian they simply don't seal that plastic cup on them.
Cavity was filled with some black cloth like foam, around 1/3 of an inch thick
Now they don't measure the same at all in DATS V2, is that expected ?
[EDIT] Also the Specs of the two are quiet far apart no?
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-my fear at this point is spl.. usually the lower the resonance, the heavier the Mms and the lower the efficiency (however I'm hopeful this isn't the case because the electrical and mechanical resistance is different, still the electrical difference is also worrying as far as spl). It's not terribly worrying though because you will likely be padding-down/(lowering spl through resistance) both tweeters anyway for the loudspeaker design here.
Did you measure them first to see what their differences (freq. response) were? I hope so.
-and yes, it's doing exactly what it should be doing with a much lower resonance value (without the backing). The changes in Qe however look weird to me (between the two drivers).
And GOOD JOB with the back removal!
CAUTION: Do NOT perform a "rub-buzz" test on these again (without the backing you've got an extended low freq. response that will just "slam" against the plates). (..and that's WITH the cap.)
-anyway, get good measurements on these with the cap and appropriate baffle test and post them in the multi-way portion of the forum with a title of:
"Radian LT-2, BG Neo 3 Alternative?"
It could be helpful to a lot of people.
(..also show the before and after pic.s of the modification and DATs result.)
Did you measure them first to see what their differences (freq. response) were? I hope so.
-and yes, it's doing exactly what it should be doing with a much lower resonance value (without the backing).
The changes in Qe however look weird to me (between the two drivers). And GOOD JOB with the back removal!
CAUTION: Do NOT perform a "rub-buzz" test on these again (without the backing you've got an extended low freq. response that will just "slam" against the plates). (..and that's WITH the cap.)
-anyway, get good measurements on these with the cap and appropriate baffle test and post them in the multi-way portion of the forum with a title of:
"Radian LT-2, BG Neo 3 Alternative?"
It could be helpful to a lot of people.
(..also show the before and after pic.s of the modification and DATs result.)
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Well...No, just the DATS V2-my fear at this point is spl.. usually the lower the resonance, the heavier the Mms and the lower the efficiency.
Did you measure them first to see what their differences (freq. response) were? I hope so.
I should have kept one with the back to measure the frequency response difference indeed, like I said I got carried away, the Dremel was whispering into my ear to continue I couldn't resist.
I did not expect them to change that much between open & closed
I am not able to measure the MMS or the SPL of the drivers, the only thing I will see if they're levels in relation to the other drivers level, I still don't understand how they measure as much SPL with only 2.83v but did not spend too much time worrying as I read that the Ideal SPL level to measure in REW was around 75dB
Thanks, I was expecting the worst when removing the first, it's good the design they are exactly the same at back than the front.-and yes, it's doing exactly what it should be doing with a much lower resonance value (without the backing).
And GOOD JOB with the back removal!
CAUTION: Do NOT perform a "rub-buzz" test on these again (without the backing you've got an extended low freq. response that will just "slam" against the plates). (..and that's WITH the cap.)
-anyway, get good measurements on these with the cap and appropriate baffle test and post them in the multi-way portion of the forum with a title of:
"Radian LT-2, BG Neo 3 Alternative?"
It could be helpful to a lot of people.
(..also show the before and after pic.s of the modification and DATs result.)
I'll make a Baffle and stick that 100uf cap on it to test asap, finally I think I will just buy one sheet of standard MDF and make the front baffle in one piece, it will allow me to practice cutting holes and routing without risking wasting that more expensive Valchromat
I guess the Radian LT3 would be closer to that BG Neo 3 driver, at least in size they seem to be
But when I get some measurements I'll post them in another thread, if that can help, it will pleasant to help someone here for once
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The string is a nice easy solution to rotate the mic around, but with the number of off-axis involved I'll stay on a turntable, I have read a table like that was called a Lazy Suzan, I am not called Suzan but otherwise it fit me
Yup. Lazy Susan Hardware is a good search parameter.
Lazy Susan - Wikipedia
-sort of Victorian era throw-back to English and American's with large tables (wealthy people) expecting individual table service, and being a bit bit bemused by the efficiency/innovation (and perhaps crassness to them) of moving the dishes around the table with the turn-table. (..though even then it was rare outside of a Chinese restaurant because even those few that had large tables didn't have them in a more "round" shape.)
Really though, as long as you keep the Horizontal range more limited, all you need is a (very low-height) platform with a fixed centered (yet near the edge of the platform) peg under the platform that can be attached to with rotation ability (bearing) and a thin slat/bar (like a 2 meter stick) that extends out from there and has it's own base with some wheels
Looking from top down: [] = platform, "." = peg, | = 2 meter stick with (inverted) t-shaped base and rollers on the (inverted) "t" extensions with the other side connected to the peg.
Disregard the "," (it was needed for formatting.)
[.]
,|
-the limitation in rotation is the supports/little-legs for the platform as they approach the same edge that the peg is on. You might also need some extension for the front of the loudspeaker cabinet as well, depending on how it's designed to be secured to the floor.
ie.
Disregard ","s; First 4 "." are stubby little "legs" for support, final "." is the peg for the super-sized "open" protractor.
__________
|.,,,,,,,,,,,,.|
|,,,,,,,,,,,,,,|
|,,,,,,,,,,,,,,|
|.,,,,,,,,,,,,.|
|____.____|
(..felt a bit like I was playing Tetris doing that.)
Platform height shouldn't be much more than an inch, and you might need to weight/strap it and/or the loudspeaker in the back to keep the loudspeaker from tipping forward.
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Yes I have been a few time at the Chinese restaurant to eat on a rotating center, never the whole table though
Tip, always leave the big bowl of soup at the center
Sorry but this time even with the ASCII it's not seeping in my brain, can't understand what you mean
I was just thinking of doing something like that and put it on a high table :
-that's good.
I wouldn't (generally) put it on a high table though, and I'd put support "casters" under the loudspeaker platform extension.
..move into position and then put pillows (or better slabs of rockwool) all around the base of the speaker/platform-table. Do the sound-absorption out to that meter or more on the floor.
Note: 8"+ (thick) of rockwool should get you a decent measurement down to at least 300 Hz.
I wouldn't (generally) put it on a high table though, and I'd put support "casters" under the loudspeaker platform extension.
..move into position and then put pillows (or better slabs of rockwool) all around the base of the speaker/platform-table. Do the sound-absorption out to that meter or more on the floor.
Note: 8"+ (thick) of rockwool should get you a decent measurement down to at least 300 Hz.
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If I don't raise it somehow I'll get the reflection from the floor in my measurements, so I need to raise that and the only way I see it stable enough is to have three or four legs, unless the structure was bolted to the floor and one leg in steel to resist the pull from the out of balance weight, well unless I completely missed something
Funny I have thought also about putting caster to support the top board but then I will need a bigger table under, and if I do that will I not have sound reflected from that bigger table protruding at the front of the baffle ?
Rockwool I can do
Sorry but this time even with the ASCII it's not seeping in my brain, can't understand what you mean
-the ASCII thing was sort of the way I had my setup with TEST BAFFLE. (..and because I wasn't going beyond about 70 degrees, it worked fine.)
..btw, verticals are still a pain-in-the-@ss with a loudspeaker measurement.
If I don't raise it somehow I'll get the reflection from the floor in my measurements..
Rockwool I can do
That's what the Rockwool is for.
..and it should be covering every platform surface that isn't covered by the loudspeaker. If the loudspeaker is on a stand then make sure the "open to platform" space under the stand is ALSO covered. The rockwool should be pushed right up against the loudspeaker/stand without any significant "gap" (as if you were cramming pillows up against the base of the loudspeaker).
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That's what the Rockwool is for.
So just to clarify, if I spread rockwool at the floor from the baffle to the mic stand I will not have issue with reflection from the floor for measuring at normal baffle height ?
For example here with the AXP-08 centered at 50cm from the floor ?
From what I understand you wrote, it that the rotating part is on the floor, with a vertical Stand to put the baffle on, but for a whole cabinet this would be completely off balance even if I create a bigger platform
No platform "Stand" (vertical extension).
Loudspeaker stand ON rotating platform is OK.
-don't get me wrong though, if you can get the loudspeaker (the ENTIRE LOUSPEAKER) off of the floor for the individual driver measurements off-axis - then great!
At that point you would be doing something like you've shown here, but with the entire loudspeaker.. and of course requiring some support for the loudspeaker...you shouldn't have any significant reflection assuming the mic. is on an extension/boom. Should be good down to about 300 Hz.
Essentially you are going from a free-field condition to an *anechoic one for that floor reflection/bounding condition, that would otherwise be there without the rockwool.
*the anechoic condition is suppressing/absorbing rather than simply avoiding the reflection. It's NOT the same thing, but it's usually close enough. (the rockwool won't absorb all reflections at all freq.s even within 300 Hz plus/up passband, but they should be suppressed enough to not cause a substantial error).
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Then it make my life easier if a pack of rockwool will suffice
The mic stand is indeed with a pole a bit longer than 2' I extend it and point straight a the drivers
-of course don't forget that you are still "gating/windowing".
(..and will need to do a near-field measurement for freq.s lower than 300 Hz.)
Still, what you are typically "shooting" for here is about 500 Hz for most of the baffle effects on dispersion. (..for a typically "narrow" baffle loudspeaker.)
Note: the results of the rear of the open-box will look weird.
(..and will need to do a near-field measurement for freq.s lower than 300 Hz.)
Still, what you are typically "shooting" for here is about 500 Hz for most of the baffle effects on dispersion. (..for a typically "narrow" baffle loudspeaker.)
Note: the results of the rear of the open-box will look weird.
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