Most setups I've seen for measuring TS parameters of a driver, independently of the electronics used for the measurement, have been placing a driver with its cone firing up and its magnet sitting flat on a surface like a desk, usually with some absorbing material like a rubber below.
My question is: Does this make sense according to the assumptions used in the derivation of the TS parameters?
To begin with the driver is literally above an obstacle, the surface above which its laying.
If that surface were the floor, this would basically be laying on an a large sound-reflecting plane. It's going to be interacting directly with it.
And often I've seen the driver sitting near to an edge of the desk or bench, so it's not even close to an infinite plane.
I originally figured that hanging a driver in the middle of the room could be a good idea, until I remembered this allows its own body to move too, so it becomes more of a system like two asymmetrical masses coupled by a single spring, rather than a single mass coupled by a spring to a fixed point.
I tested this by simply firmly holding the speaker near Fs while hanging, and it did change its behavior, while simply approaching my hand didn't.
And this is still different from having something like a steel arm holding it, because my hand is very damping, it's damping the vibrations and not actually forcing its body to be fixed.
Same thought goes for a speaker over something like a damping rubber versus a speaker held by a vise on a bench, they'll be different.
Maybe the influence of those different fixation methods isn't that large, but I suppose that having the speaker over a large surface (like above the floor) or close to an edge of a large surface (like in the edge of a desk) makes a reasonable difference.
Which is the proper way to fix it?
My question is: Does this make sense according to the assumptions used in the derivation of the TS parameters?
To begin with the driver is literally above an obstacle, the surface above which its laying.
If that surface were the floor, this would basically be laying on an a large sound-reflecting plane. It's going to be interacting directly with it.
And often I've seen the driver sitting near to an edge of the desk or bench, so it's not even close to an infinite plane.
I originally figured that hanging a driver in the middle of the room could be a good idea, until I remembered this allows its own body to move too, so it becomes more of a system like two asymmetrical masses coupled by a single spring, rather than a single mass coupled by a spring to a fixed point.
I tested this by simply firmly holding the speaker near Fs while hanging, and it did change its behavior, while simply approaching my hand didn't.
And this is still different from having something like a steel arm holding it, because my hand is very damping, it's damping the vibrations and not actually forcing its body to be fixed.
Same thought goes for a speaker over something like a damping rubber versus a speaker held by a vise on a bench, they'll be different.
Maybe the influence of those different fixation methods isn't that large, but I suppose that having the speaker over a large surface (like above the floor) or close to an edge of a large surface (like in the edge of a desk) makes a reasonable difference.
Which is the proper way to fix it?
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Driver vertically oriented will reduce the effects of gravity, non-linear BL, and stiffness/compliance on the test results.
@weltersys Yes, but what about the surface in which it's mounted?
Should it be kept the farthest from all surfaces, as in held by a tall, but heavy and stiff arm in the middle of the room, or fixating it near a wall is no problem?
Should it be kept the farthest from all surfaces, as in held by a tall, but heavy and stiff arm in the middle of the room, or fixating it near a wall is no problem?
A heavy, stiff clamp in the middle of free air space would be best, or as far from walls as you can manage would be better than near walls.
That said, if you have a vise you can clamp the speaker frame in, and the speaker is not pointed at the wall, good enough 😉
That said, if you have a vise you can clamp the speaker frame in, and the speaker is not pointed at the wall, good enough 😉
How close is "near" to a wall - is a metre or two OK?
I'm glad this has been asked, thanks for posting the thread, since it's something to consider when I take on the next wave of speaker tinkering...
Previously I've clamped a driver to a workbench, oriented vertically. I need to think if building a jig an option, and if so how rigid would it need to be 🤔
I'm glad this has been asked, thanks for posting the thread, since it's something to consider when I take on the next wave of speaker tinkering...
Previously I've clamped a driver to a workbench, oriented vertically. I need to think if building a jig an option, and if so how rigid would it need to be 🤔
What do you do when the drive is a small 17kg lump? Trying to figure out how to mount this thing for testing in free air. A safe way to work with outboard motors is to mount them to a goods trolley. Would bolting an MDF ring to the trolley uprights so that the weight is taken up by the trolley blade on the ground be sufficient? Done in this manner, the cone would have some steel pipes in its path and the total weight holding steady to the ground and some give in the wheels
