Hello,
This might be a pretty basic question to some, but I'm unable to find an usefull answer to it.
When a driver manufacturer publish it's driver's frequency response diagram, in what environment and how exactly are those results acquired? Do they mount the driver on some kind of infinite baffle? (Outside wall of the room perhaps?)
Reason for asking is... when I mount that driver to an open baffle, or if I just hang it with no baffle at all, what kind of a readout can I expect? (Provided that the measurement are taken outside with no reflection points, except for the ground perhaps)
I've seen some videos where a downward slope to lower frequency is displayed, with a peak in the middle of the spectrum. Would that happen even to the driver that's measured dead flat on specs?
Thanks for your help,
Stefan
This might be a pretty basic question to some, but I'm unable to find an usefull answer to it.
When a driver manufacturer publish it's driver's frequency response diagram, in what environment and how exactly are those results acquired? Do they mount the driver on some kind of infinite baffle? (Outside wall of the room perhaps?)
Reason for asking is... when I mount that driver to an open baffle, or if I just hang it with no baffle at all, what kind of a readout can I expect? (Provided that the measurement are taken outside with no reflection points, except for the ground perhaps)
I've seen some videos where a downward slope to lower frequency is displayed, with a peak in the middle of the spectrum. Would that happen even to the driver that's measured dead flat on specs?
Thanks for your help,
Stefan
you have to read the fine print on the driver spec pages... Most manufacturers use an IEC baffle, which is a fairly large baffle. But some have their own process.
Seas for instance, shows an 4-pi measured response, and then pencils in the theoretical 2-pi (infinite baffle) response.
Yes. Even the perfect ideal driver will be affected by the baffle shape and the change from 2-pi to 4-pi.
Seas for instance, shows an 4-pi measured response, and then pencils in the theoretical 2-pi (infinite baffle) response.
Yes. Even the perfect ideal driver will be affected by the baffle shape and the change from 2-pi to 4-pi.
Here is an example. This is the measured response of a high quality 6 inch driver (Satori MW16TX-4).
The black curve is the infinite baffle response. I measured this with the near field technique. From 20 Hz to 2000 Hz, this driver has an almost ideal perfect IB response.
The blue curve is the same near field measurement, but adjusted to be equivalent to a 4-pi "open space" measurement with a typical small monitor sized baffle (10 inch x 14 inch).
When compared to the infinite baffle response, you can see that at 100 Hz there is a loss of about 5 dB. At 1000 Hz there is a gain of about 1.5 dB.
Any 6 inch driver that I might install in this baffle would be affected in teh same way. Each driver would bring its own response characteristics, but there would always be a -5 dB effect at 100 Hz, and a +1.5 dB effect at 1000 Hz. It is a function of the baffle shape.
j.
The black curve is the infinite baffle response. I measured this with the near field technique. From 20 Hz to 2000 Hz, this driver has an almost ideal perfect IB response.
The blue curve is the same near field measurement, but adjusted to be equivalent to a 4-pi "open space" measurement with a typical small monitor sized baffle (10 inch x 14 inch).
When compared to the infinite baffle response, you can see that at 100 Hz there is a loss of about 5 dB. At 1000 Hz there is a gain of about 1.5 dB.
Any 6 inch driver that I might install in this baffle would be affected in teh same way. Each driver would bring its own response characteristics, but there would always be a -5 dB effect at 100 Hz, and a +1.5 dB effect at 1000 Hz. It is a function of the baffle shape.
j.
Attachments
Thanks for info 🙂
So its a large box with a large baffle or something close to infinite.... I've looked into seas testing lab, as you mentioned, they use anechoic chamber with wire mesh floor, etc.. Is there a way to obtain close results in home made builds? Where can you measure low frequencies?
One small offtopic.. have you, by any chance, measured satori in open baffle? I'm curious how different the result would be.
So its a large box with a large baffle or something close to infinite.... I've looked into seas testing lab, as you mentioned, they use anechoic chamber with wire mesh floor, etc.. Is there a way to obtain close results in home made builds? Where can you measure low frequencies?
One small offtopic.. have you, by any chance, measured satori in open baffle? I'm curious how different the result would be.
Of course, well at higher and middle frequencies you can measure and then turn off the mic before the sound reflections from the walls reach it. This is called gating. You look at the recording and set an end gate just before the reflections.
Dennnic, check out VituixCAD measurement preparations documents here VituixCAD Loudspeaker simulator
This seems to best one can do at home, without anechoic chamber. Gated far field measurements in combination with nearfield and impedance measurements gives close approximation of anechoic measurements. VituixCAD can handle everything else than the measurement, but the measurement docs show how to measure using ARTA. There is also a thread here in the Software section. Plesse read the manuals before asking questions in the thread 😀
This seems to best one can do at home, without anechoic chamber. Gated far field measurements in combination with nearfield and impedance measurements gives close approximation of anechoic measurements. VituixCAD can handle everything else than the measurement, but the measurement docs show how to measure using ARTA. There is also a thread here in the Software section. Plesse read the manuals before asking questions in the thread 😀