In the past, I've measured T/S parameters of drivers by setting them on the floor facing up; however, I've since llearnedfrom the collective wisdom here that this is a *bad* way to do it and would like to do it the right way.
I am thinking about building a large open baffle with a removeable/replaceable insert in the center. I could then build inserts for various sized drivers, put them in the baffle, and measure the driver, not havong to build a new large baffle for every new size of driver I want to test. Does that make sense? If not I can create rough drawings later.
My questions are as follows:
I am thinking about building a large open baffle with a removeable/replaceable insert in the center. I could then build inserts for various sized drivers, put them in the baffle, and measure the driver, not havong to build a new large baffle for every new size of driver I want to test. Does that make sense? If not I can create rough drawings later.
My questions are as follows:
- Is this general approach good?
- How large should I make the baffle if I want to get good measurements on drivers ranging from tweeters to 12" woofers?
- Are there any general design/construction things I should make sure to do?
- Any other suggestions?
Measuring T/S paramaters (..cheap and easy):
Measure and Analyze your drivers and loudspeaker systems video
As for measuring the impulse response and then graph for things like freq. response, setting on/in a BAFFLE on the floor facing up is an excellent way to measure (..assuming the floor is very absorptive with a typical couple of rolls of insulation on the floor).
under this condition:
1. speaker should effectively be in the center of the room's floor away from everything.
2. baffle should be supported up about a foot from the insulation (which is laying on the floor covering at least the area of the baffle) - with good air-space for the speaker (..so that it isn't pressing up against the insulation when it's mounted to the baffle). Think of it like a super-sized (4 x 8 foot) "coffee table" that you remove after use.
3. the mic. should be "dropped" (hanging) from the ceiling directly "on-top" of the center of the driver. (..suspended about a meter away from the dust-cap of the driver for freq.s: 300-20000 Hz.)
4. the driver should be mounted flush with the baffle with a chamfer in the rear - see Zaph's baffle at the link (..though note that he does not use the baffle on the floor as mentioned).
..also note that Zaph's page mentions T/S testing through his software as opposed to something like the DATS system in the video link above.
-and yes, Zaph uses a "mounting plate" for different drivers and the same baffle: which is excellent.
Zaph|Audio
Measure and Analyze your drivers and loudspeaker systems video
As for measuring the impulse response and then graph for things like freq. response, setting on/in a BAFFLE on the floor facing up is an excellent way to measure (..assuming the floor is very absorptive with a typical couple of rolls of insulation on the floor).
under this condition:
1. speaker should effectively be in the center of the room's floor away from everything.
2. baffle should be supported up about a foot from the insulation (which is laying on the floor covering at least the area of the baffle) - with good air-space for the speaker (..so that it isn't pressing up against the insulation when it's mounted to the baffle). Think of it like a super-sized (4 x 8 foot) "coffee table" that you remove after use.
3. the mic. should be "dropped" (hanging) from the ceiling directly "on-top" of the center of the driver. (..suspended about a meter away from the dust-cap of the driver for freq.s: 300-20000 Hz.)
4. the driver should be mounted flush with the baffle with a chamfer in the rear - see Zaph's baffle at the link (..though note that he does not use the baffle on the floor as mentioned).
..also note that Zaph's page mentions T/S testing through his software as opposed to something like the DATS system in the video link above.
-and yes, Zaph uses a "mounting plate" for different drivers and the same baffle: which is excellent.
Zaph|Audio
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If all you are doing is measuring T/S parameters then just holding the driver in the air with your hand is going to be virtually identical to mounted in an open baffle. Restricting the air flow around the rear of the driver and especially around pole piece vents will definitely affect T/S parameter measurement - sitting it on a floor firing up does both of those things so it's not a good idea. The size of a baffle (or none at all) will not change things below a few hundred Hz.
Thanks ScottG and TMM for your input!
In addition to T/S parameters, I do intend to do frequency, impedance, and phase sweeps for full modelling of a speaker in the design phase, so based on what was said it sounds like a large baffle fits my needs.
I started work on it, 4'x4' with a 15" square cutout in the middle to mount different drivers in. The baffle is basically done and the first mounting plate nearly so (just have to chamfer the back and put in screw holes).
Interesting idea having it parallel to the floor instead of standing up. Would that change the ts measurements at all due to the driver sagging downward slightly from gravity? I built legs for my baffle, but maybe I should jyst leave them unattached and run it parallel to the floor instead.
Either way this has been a fun excuse to use my tools (and buy a jigsaw!). I will post pictures this weekend.
In addition to T/S parameters, I do intend to do frequency, impedance, and phase sweeps for full modelling of a speaker in the design phase, so based on what was said it sounds like a large baffle fits my needs.
I started work on it, 4'x4' with a 15" square cutout in the middle to mount different drivers in. The baffle is basically done and the first mounting plate nearly so (just have to chamfer the back and put in screw holes).
Interesting idea having it parallel to the floor instead of standing up. Would that change the ts measurements at all due to the driver sagging downward slightly from gravity? I built legs for my baffle, but maybe I should jyst leave them unattached and run it parallel to the floor instead.
Either way this has been a fun excuse to use my tools (and buy a jigsaw!). I will post pictures this weekend.
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