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venturing back to a passive two-way project, in a smallish travel package
My last few projects have been 3-ways; coaxials set-up with a passive Xover, and actively crossed (mini DSP-hd, bi-amped) with a woofer(s).
Being a fan of Xover points outside of the 1-3.5Hz range (highest hearing sensitivity range), I previously matched full-range with a pair of Beyma 12BR70’s in an open back bi-amped design that I hauled over to an event a couple of years back. I’m hoping to get back to an event next year with something a bit easier to transport. I've moved to Colorado.
My initial goal is to KISS, but I’m expecting at a minimum a Zobel for W, a significant attn for the full range, with targeting the filters to manage the baffle step diffraction (bypassing the need for a BSC circuit).
I plan on starting with a 1st order HP with a 2nd order LP. My thoughts being (which may prove otherwise, as measurement often does…) is that the baffle step will have the affect of moving the 1st order HP electrical slope towards a 2nd order slope (combined mechanical) with frequencies going south, and moving the 2nd order electrical LP towards a 1st order slope (combined) going into the higher frequencies (as a result of the baffle effect). Hoping not, but may need a notch on the W if the peak ~ 6.2g Hz causes an issue (although it is quite far from the expected Xover point, so hopefully not needed).
Ultimately may need to move to a 2nd order HP matched with a 3rd order LP, but we shall see. Generally, with mixed filters you see the higher filter in the HP position (to protect a tweeter), but the Fs of this AN driver is 127Hz, so I am going to play with my initial thoughts regarding baffle step affect on the net filter slopes.
I have a pair of Audio Nirvana 4s sitting around and I’m going to pair with the Epique 150HE-44s. The AN 6's I have extend up well past my hearing, however I don't know if the 4s, with a different cone design, will be so accomplished.
Time to make some more sawdust. Hope to catch back up with you guys at an event next year !
Comments
...a little progress.
I have more lining to do, but now waiting on tubing for the port. I'll be supporting the port inside the box with the bracing between the sidewalls. Net internal box vol for the woofer ~12 ltr.
That's a lot of felt and $$$ inside that box - looks good - What Coaxial driver had you planned for the enclosed portion?
I’m using ¼ inch felt left over from my previous build. I had bought a small roll of the stuff.
This go round I’m not starting with a coax, I’ll be using an Audio Nirvana 4 in ‘full range’. Looking at this as an exercise in playing with a crossover set around the box’s baffle step affect.
I've been working on getting the port to ~length (freq measure, trim, repeat..)
The tape is temp to get a tight-enough fit as I made a few trips back to the table saw. I had just tossed in a board with a few components to get towards an accurate net internal volume.
Getting the bottom corner W nut and washer in place once the only access it via the rear is going to be a challenge.
I plan on staining the sides, but gotta hand it to the DuraTex for covering a few issues on the baffle
Now for the fun part; designing a passive Xover.
I plan on starting with using my miniDSP to look at filters and Xover points (and balancing the drivers’ differing sensitivities). As mentioned, I hope to target the baffle diffraction area and would like to combo a 2nd order LP with a 1st order HP for the Audio Nirvana driver. But the drivers in the box may dictate otherwise... From there pull out my box of components, alligator clip wires, and I understand a bottle of wine (or two) is advised.
Looking at these I’m considering naming them Black&Tan, but then do I need to continue posts under Adult Refreshments?
Initial miniDSP filters results:
These drivers look to be working well with a 2nd order LR LP combined with a 1st order HP.
I ran multiple filters and leaning towards 2nd order LPass filter LR @ 380 and 1st order HP @600 (non-inverted). The attached is with a notch @1650 Hz (-4dB, Q2) and -10dB attenuation on the AN driver. I thought I had trimmed the port down enough, but may need to cut down a bit more.
img 2108: the red line is with the port slightly stuffed (and LP 380 and HP 600, the blue line unstuffed and with slightly different filter points)
Wow! That ^ looks sweet!
Visually the graph makes me question how much "presence" they have based upon the dip from 3 ~ 6 KHz.
Sorry, I posted pic w/o reference provided to vertical ranges.
The dip is approx 2.5 to 3dB centered around 3500 (BBC dip area) which I generally prefer. The notch I put in is ‘south’ of that range bringing down a rise around 1650.
I hope to ~ duplicate the active filters w passive components - I’ll work on keeping the 1650Hz notch Q from further attenuating the driver’s natural dip 3500-6000.
Is that 5dB/div?
That was at 10dB per.
Attached is the area shown at 5dB per (taken ~30in 15 degrees off ctr), as well the measurement at the port
I’ll look at potentially placing the notch to attenuate the rise ~11g
I need a bigger hammer, and/or suggestions
I’m trying to approx match passive components (parallel notch) to dsp notch results: fq 1550, gain -7.6, Q 1 (blue line).
Yellow is pre-notch. While I have been trying differing components, outputs from VituixCAD model and diyaudio calculators, I cannot pull the level down anywhere near target (resistor values from 10 and up thru 35 Ohms, green line).
I have put together a passive notch ~10,400Hz which is acceptable, but this range (1g to 2.5g) is illusive. I get that L shunts the LF, C shunts the HF, and resistor drops the level, but ‘its not happening’
Thx
Take a look at what your impedance is doing at the notch frequency range.
As modeled in VituixCAD; left side starting at zero, darker horizontal lines increments of 5
The AN driver 'out of the box' exhibits a fairly flat impedance from approx 300 up (8 going towards 10 at 15-20K)
I’ve been struggling with getting a parallel notch in place on the Audio Nirvana broad range driver around 1600-1800Hz, pairing with a notch for the bump at 10.4k Hz in this driver. Using filters designed via VituixCAD and the diyaudio calculators, adjusting components on each end, to no avail.
Then it finally hit me, and while this is probably nothing new to the majority of the builders here I’m tossing it out biz it was an aha moment, for me anyway. I still have tweaking to do with the final components, but here are the steps I took:
A) Put in a zobel so the filters I put in had some chance of stability over notch frequency range (thx Nick).
I finally saw the notch for what it is: a LP and a HP with resistor to control the bypass.
C) Modeled and then applied a LP filter. Period. Got that slope about where I wanted. Then pulled it out.
D) Modeled and then applied a HP filter. Period. Got that slope about where I wanted.
E) When I put these together, with a resistor (of varying values) it blew up again (didn’t actually blow up it just put me back to ground zero- a fairly worthless notch maybe attenuating a dB of the rise). Then the aha moment. I didn’t actually need to place the resistor as shown per the parallel notch diagrams ( coil / cap / resistor), but could actually place a resistor in series with just one path of the notch (and/or each with a differing resistor value). I placed a 16 ohm resistor in series with the 1.0mH coil along with a 6.2uF cap, and while not a final combo of component values, its progress. I’d call this more of a shelf vs a notch but it works for this driver. I’d like to pull this down a couple more dB in this range (BBC) but its down 5 or so from where it was sitting.
1st order Xover, with contour networks (+ Zobel) on AN driver.
I'll need to work on tuning the port (trim down a bit and/or lightly stuff, but for a small 5.5in driver base extension not unwelcome). The AN driver looks finally to be under control, and now a shallow BBC. Probably sticking with 4+4 net 8 ohm for the woofer.
(Measurements in room approx. 4.5 ft.)
Final parts came in. I’ll need to unwind a couple of coils to tgt values, and playing with the placement on the crossover board.
Parts express asks (post ordering parts) ‘why you picked these items?’
Answer: Well, in this case, ‘cause I must of screwed up when soldering the first set of parts…
The good news about being visited by Gremlins post assembling the crossover boards, besides being quite the learning experience (and then supporting the USPO), is by tracking down the issue you go over each component + and – a unit here and there, revisiting both the post measurements and listening results. In the attached, the purple line shows the pop ~220Hz that was driving me nuts, so a small change here, and another small change in my parallel notch ~10kHz by upping inductor somewhat surprisingly from a 0.82 to 0.92 (small value but ~12%) you get a better sounding speaker. And, rack another one up to ‘error between keyboard and chair’.
I did additionally play around with a series 1st order, with less than stellar results.
Thinking was with a 1st order this might be the place to give a series network a go- but too much interaction, at least with these drivers. So I’ve been making a couple slight changes to the parallel first order (minimal resistor and coil changes looking at 15 degrees off axis, and at ~6ft).
Additionally, I have been going back and forth with relative levels between W and the AN full range mid/high end. Depends somewhat upon what I’m listening too (and somewhat with what mood I’m in). Since the 1st order Xover slope is not steep, and crosses around baffle step range +/- 510Hz, I may end up with a toggle between a couple of resistors providing +/- 1 to 1.5 dB level change.
I’ll post some measurements when set-up.
Unusually I found the port (tuned ~37 hz) was _very_prominent and needed to be attenuated. I’ve been working on via active 1st order HP in combo with notching down to smooth it out > trying to get rid of what was a peak (as seen in the VituixCad pics previously posted). I’ve got more work to do, but getting tired of the frequency sweep tones…
just about there… I think
@ 8.5 ft
Probably close enough for gov’t work. Measured ~ 8.5ft, mic (stationary) centered btwn left and right speakers.
Hope to catch up with you guys in Iowa.
(just uploaded ½ oct version as well)
Revisiting the crossover for Iowa (parts on their way, with a bit of adjustments yet to be finalized-fingers crossed) trying to go with an all passive 1st order LP on the woofer and a 2nd order HP on the AN, with a notch filter set before the crossover. Hopefully I can somewhat match the active notch I have with the active DSP. The little 4in AN driver is a problem child compared to its 6.5 in larger brother (which is one of my fav ‘broad range’ drivers, and easy to work with in a two-way set-up).
As mentioned, it (the 4 incher) really doesn’t like a cap being placed in a first order filter (rolls off then peaks badly around 200Hz). Hence the addition of the coil to try to tame it.
Also, I hope to maintain the switch in the back for alt resistor values for the AN driver > standard (higher curve) and large venue voicing, as seen in the graph, gold lines.
OK, how many days until Iowa?
I just cleared mine for the first time today. You have plenty of time.😎
https://www.jfcomponents.com/
One reason I was planning on using dsp with this speaker was to control the excessive port output (I hadn’t experienced this issue to that extent). So I put a sock in it > maybe I can find a happy balance with a poly/wool blend….ha
that’s measured at about 8 feet
Ready (finally, and full passive), and looking forward to checking in with you guys next weekend in Iowa!
My final tweaking is getting the port socked correctly - geez. The frequency chart shows (left and right speakers averaged together) with and without the socked port.
Safe travels everyone.