I am interested in this driver but can't find the Thiel Small parameters for it. Has anyone here who has used it measured them .
Hey Woody, long time no hear!
Curious as to why? Everything you need to know is right here, assuming of course it's accurate: DMB-A Midrange Driver - Swans Speakers
GM
Oh I saw that page but it doesn't have the QMS and QES listed. I might want to use this at a verry low crossover point and need to use a series notch filter but to build one I need the QMS and QES.
If you want a low crossover mid dome then have a look at the morel mdm55 or em1308 or visaton g50. All have an FS of around 350hz ish.
Thanks, saw it and yes, one can guesstimate them without measurements, though don't know if it would be accurate enough for his app, so didn't post this: Measuring Loudspeaker Driver Parameters
GM
GM
GM, ok it looks like the QTS might be about 1. Now if I could vent that rear pod I quess I might be able to lower the FS to about 400 -500 hz with a QTS of about .7 I figure I might be able to run it full range as long as I kept the power very low like .5w average with perhaps 3W peaks. Then bring a woofer in below 500hz.
The following two boxes are not quotes, they are part of my post. Not sure what happened, or how to fix it.
I did get it to roll-off well enough above 4500hz, but that was by using a parallel notch filter---1.5uF/.14mH/30ohm. For some reason,the calculator I used gave very different values than these, so these are the result of trial and error, with measuring. Maybe it could no longer be called a parallel notch, though the capacitor/inductor/resistor-in series-with-the-driver format, remains.
To tame/roll-off the low end resonance/ response: Here is a starting point that looks good for an 800hz high-pass: 20uF series cap plus a series notch filter (parallel with the driver): 40uF/1.2mH/3.3ohm.
This looked good after swapping parts/measuring ; I did not do a simulation. I suspect that I will need to change these filters somewhat when integrating the woofer, DMB-A mid and a tweeter in my enclosure. I did not check the impedance of this filter/driver combo.
On the upper end, distortion seems to limit the DMB-A to about 4500hz. Super low distortion until about 5khz, then up it goes---dramatically. Is this breakup (or is something wrong with my test set-up)?
I did get it to roll-off well enough above 4500hz, but that was by using a parallel notch filter---1.5uF/.14mH/30ohm. For some reason,the calculator I used gave very different values than these, so these are the result of trial and error, with measuring. Maybe it could no longer be called a parallel notch, though the capacitor/inductor/resistor-in series-with-the-driver format, remains.
To tame/roll-off the low end resonance/ response: Here is a starting point that looks good for an 800hz high-pass: 20uF series cap plus a series notch filter (parallel with the driver): 40uF/1.2mH/3.3ohm.
This looked good after swapping parts/measuring ; I did not do a simulation. I suspect that I will need to change these filters somewhat when integrating the woofer, DMB-A mid and a tweeter in my enclosure. I did not check the impedance of this filter/driver combo.
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Yes, the 1.5uF//0.14mH//30 ohm is a parallel notch. It is centered at about 11 kHz. The 30-ohm resistor makes a steep rise in impedance above 4.5 kHz, which makes for a good roll-off.
I was advised to look at the HIFI Compass website that has a review of the HIVI DMB-A. The distortion does not climb above 5000hz, the way it did in my measurement. There is something amiss in my measurement set-up.
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Thanks Dave, I had started out a lot lower than 11khz, so that seems to explain why I had to fiddle with the values so much.
I liked how the AR3a project came out (that used a similar dome mid, but with a lower resonance), so this project is like a smaller version of that one---It is a modified AR-16---which started out as an 8" 2way. I will reuse the original woofer, like I did with the AR3a rebuild. This AR-16 rebuild will need a new crossover, like the 3a. The AR-16 cabinet is only .64cuft internal, and the bass is nice.
I think that I will use the SB19st-C000-4 tweeter. It is smooth and inexpensive, with generous x-max.
Hey Dave, one thing I have wondered about: If you use a notch filter to reduce SPL from a speaker, you are reducing the output from the resonance, but is there also not a proportionate reduction in the reproduced level of the source(music)? So won't the resultant sound that is reproduced, in that range, have the same proportion of delayed signal from the resonance/ringing, as the speaker had before the notch was applied? Also in this sense (ringing, resonance) is the speaker no longer an ideal “minimum phase device”?
In my filter I used the parallel notch just to affect a roll-off, not to level the response.
In my filter I used the parallel notch just to affect a roll-off, not to level the response.
The parallel notch has a bandwidth, usually fairly narrow. It will provide the most spl attenuation at its center frequency. Then depending on the effective bandwidth of the notch, it will attenuate spl somewhat on either side of that center frequency. A tall and narrow notch will attenuate most locally around the center frequency, while a broader notch will attenuate farther away.