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 not also 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 to the source audio signal, as the speaker had before the notch was applied?
Just ordered one for a 3 way OB build I am working on. I just wish it went lower. Would love to cross it around 600 or so
Is that dome removable ? If it is could the chamber in back of the dome
be vented to lower the fs ?
be vented to lower the fs ?
After applying the passive filters that I mention here in post #15, which give me a pretty smooth, quasi-bell-shaped, on-axis-curve, centered on approximately 2500hz, 600hz is down about 11db. Over-all that is something like first-order, 6dB/octave. According to my measurements, the absolute (correct term?) distortion---not the percentage distortion---is still about 0.1%, and down a little over40dB at 600hz. This driver is spec'd at 92dB sensitivity. Most open baffle bass sections end up being way less sensitive than this, after compensating for OB losses. Seems like it would be possible to mate this with a woofer, or mid woofer, that was pretty well behaved to about 3000hz. I know that there are few of these to be had---almost all of them would have softer paper or poly cones---not the shiny-coated hard pressed paper PA woofers we mostly see in larger sizes.
All this being said, Wolf (who I think knows more than I do) (in other threads) has said that this driver is useful to about 800 or 850hz with a series notch to tame the 700hz resonance. Why not try it, these are not expensive drivers. Or use two of them to keep distortion down when you turn up the volume----most open baffles have lots of baffle space. Of course you will have a dipole radiation pattern from the woofer(s) only, unless you mount two domes back-to-back.
I wondered about this too. I am guessing that it needs the trapped air to control the dome movement, and would likely self destruct, with excessive excursion, without it. You would have a similar situation as trying to use one of the vintage "acoustic suspension" woofers in a ported box. The A.S. woofers relied on a tightly sealed box of smaller volume to control cone movement, because the physical suspension was, compared to woofers meant for vented boxes, very compliant.
If it was that easy to make a low Fs, low-distortion dome mid, why wouldn't the manufacturer just do it?
Im not sure what you mean by the bolded- my plan is to have this cover from ~800 to about 4k. I am using this in an OB ceiling mounted setup with a separate subwoofer. It's replacing styrofoam DML panels which sound great but have a lot of issues- weak LFE and extreme EQ for a flat response. They have amazingly wide dispersion though and while I haven't measured transient response they seem great there as well.
So I want this to cover the "important" frequency range and in combo with the other drivers have a flatter response and more LFE. I know this and the tweeter (the plan is a hornless compression driver) will need attentuation to balance with the LF driver but I'm hoping they will be fine outside of that.
I did not intend the BOLD, sorry. I thought you were doing a freestanding open baffle. Don't have time right now, but will look to if see if there is anything I said that is relevant to the further information that you have supplied. So---more later.
I can see why that could raise a question. The thought was that low order filters need a couple of clean octaves on either side of the crossover point.
I was trying to imagine how to use the DMB-A down to 600hz, but I suppose the cross would still end up around 800hz. I have had major frequency overlap between woofer and mid on a freestanding open baffle, trying to keep the crossover super simple. The woofer was a vintage 12" Bozak that played well past 3000hz---directivity gets narrow, but the sound stays clean.
800hz to 4300 hz is how I am planning to use my DMB-A pair. I am not sure what the filters will end up looking like, but those in my post #15 made the response look good for the driver by itself.
Maybe you will need steeper filters than mine if you want to play LFE at high volume?
The idea to use a notch filter is good.
Paralleled RLC in series, broad enough to give the right Q.
I guess that it can be used alone as the passband filter, but the " high volume" matter puts doubts about the effectiveness in a real design.
Paralleled RLC in series, broad enough to give the right Q.
I guess that it can be used alone as the passband filter, but the " high volume" matter puts doubts about the effectiveness in a real design.
It may work for me, because my present usage is an 8" 3way in which the woofer is capable of only moderate output. Also, the DMB-A is supposed to have 80 watts power handling, and from what I have seen in measurement, the distortion does not rise too quickly below the pass-band.
I am feeling a little shy to say that I am now thinking/remembering(?) that I also had a 40uF cap in series when testing. Not sure. My main focus was in discovering how to tone down the resonance around 750hz (and on-axis hump above 4300hz) and to see when distortion set in unacceptably.
My plan is to install the 3 drivers in the solid, but not completed, cabinet and develop a crossover that allows the driver to work up to the output limit of the woofer.
So far I am thinking that the woofer will meet the mid with a low(ish)order filter around 800hz. The woofer/enclosure are vintage (AR-16) and originally crossed at 1500hz, using just a 1.5mH coil and 30uFcap(shunt). I was surprised that this combination resulted in enough baffle step compensation to give the woofer a flat response, which it apparently had when new. Maybe the woofer has high Le?
I did something similar with an (NLA) Dayton DC50FA 2” dome (Fs:371hz), crossing at around 500hz in vintage AR3a woofers/cabinets. I do not play them too loud, out of respect for the unobtainium woofers. The speakers have a flatter response than the originals, and got some praise for midrange clarity at our DIY gathering.
Are other companies still selling the DC50FA under another brand name/model#????
Def not a high volume system so the driver should be safe. Still, I will just follow HiVi's recommendations and do the low cross at 800. Im also using a 12" for the bass driver and it should be fine at 800. Well below the beaming frequency.
I have come up with a 3way passive crossover for my 8” AR-16 speaker rebuild, using the HIVI DMB-A dome-mid. I used the previously mentioned series-notch, but not the parallel-notch for the higher frequency hump. After many, evolving, iterations the speaker now sounds coherent and “relaxed”; or maybe I should say, I feel relaxed listening to it.
This was the most difficult mid I have worked with, especially rolling off the top end. I usually try to pick drivers that are easy to work with. I am learning a little bit more about manipulating stubborn areas in drivers though.
This was the most difficult mid I have worked with, especially rolling off the top end. I usually try to pick drivers that are easy to work with. I am learning a little bit more about manipulating stubborn areas in drivers though.
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