Hornresp rulez! After measuring the horn "as built", the match to the simulation is unbelievably good. The general shape and notch frequency is spot on. Black is in 2xPi, grey in 4xPi space, the measured result is somehow inbetween. I will try to find the measurements later.
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Since I have learned that even with 200 Hz cutoff, the "synergy magic" is still there and that the SPL I am listening at is relatively low, I am reconsidering the use of bass drivers. I have some cheap but relatively OK 165 mm woofers. The black line is 4 of them on the horn, each with 10 l of sealed chamber. Extension down to 80 Hz (-3 dB) is good enough, since there will be a subwoofer anyway. Compared to the 18" I considered before, I would save 8 kg of weight and 90 l of volume (reducing wood weight further).
Of course, at the cost of LF extension. The 18" in a 130 l closed box on the same horn is here:
And also maximum SPL (grey one is the 18"):
With the 18", I could have an all in one box, heavy and large for moving around. But I think a better compromise would be to cut down the size and weight and use a separate bass unit/subwoofer. Still not fully decided. And I hope to test both options and compare.
Of course, at the cost of LF extension. The 18" in a 130 l closed box on the same horn is here:
And also maximum SPL (grey one is the 18"):
With the 18", I could have an all in one box, heavy and large for moving around. But I think a better compromise would be to cut down the size and weight and use a separate bass unit/subwoofer. Still not fully decided. And I hope to test both options and compare.
With a bit of effort, I will be able to mount two 3FE22s from the sides as alternative mids, the 18" from the bottom and two 6.5" woofers from the top to try out different combinations. Unused drivers will be shorted and the ports plugged with 3D printed plugs. Where possible, back covers will be added.
Nice pelanj,
good to see others setting up to be able to try different driver combinations.
Fwiw and by way of encouragement, my 5-way syn11 that has two 18"s, two 12"s, four 4"s, and a coax CD has turned out to be hands down the best speaker I've made.
Thanks, Mark. I am preparing for mounting the 3FE22 mids. A 3D printed spacer, entry hole around 85 mm axial distance from the planar tweeter. I could maybe get it 10 mm closer, but then it would be hard to fit a back cover and mounting screws.
The entry hole will be 25 mm diameter with the option of making it smaller with 3D inserts.
The entry hole will be 25 mm diameter with the option of making it smaller with 3D inserts.
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The 18" woofer is a monster. I drilled the holes for the threaded inserts with a 10 mm drill instead of 8 mm by mistake, so I hope it will hold on to the horn at least for a while.
Now I need to install the two 6.5" woofers tomorrow and it will be fully loaded🙂
Now I need to install the two 6.5" woofers tomorrow and it will be fully loaded🙂
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I do not understand how Clio pocket stores the measurements.
Anyway, some interesting findings:
The 3FE22 pair has very similar response to the single 8PE21. There is a dip which will need more investigation - most probably related to too large port distance
The 18" bass is mighty and works nice with open back and a bit of EQ. I believe it would work as simmed in a large box.
The dual 6.5" sound anemic in comparison, there is no replacement for displacement - so these are crossed out from the project.
Anyway, some interesting findings:
The 3FE22 pair has very similar response to the single 8PE21. There is a dip which will need more investigation - most probably related to too large port distance
The 18" bass is mighty and works nice with open back and a bit of EQ. I believe it would work as simmed in a large box.
The dual 6.5" sound anemic in comparison, there is no replacement for displacement - so these are crossed out from the project.
I wonder what would happen if I ran the whole horn with open backs. I now have the 3FE22s as mids and the 18" as bass, all without a back cover. Maybe it is placebo, but I think it sounds really nice this way. Sort of a folded open baffle speaker.
I think there will be two effects:
a) there will be reflections of the back wave as with other open backed speakers
b) however, the back wave will be of a different timbre due to the fronts of the drivers being loaded by the bandpass chamber and the horn - or am I wrong here?
The open back MEH seems to "disappear" even more than the closed back one. I actually had to go near and have a listen if I forgot to turn off the speakers behind the test pair.
Since the MEH is meant to be operated only down to around 100 Hz, there is not much cancellation due to a quite large path difference at that frequency.
I think there will be two effects:
a) there will be reflections of the back wave as with other open backed speakers
b) however, the back wave will be of a different timbre due to the fronts of the drivers being loaded by the bandpass chamber and the horn - or am I wrong here?
The open back MEH seems to "disappear" even more than the closed back one. I actually had to go near and have a listen if I forgot to turn off the speakers behind the test pair.
Since the MEH is meant to be operated only down to around 100 Hz, there is not much cancellation due to a quite large path difference at that frequency.
Do you think its better to place the oval midbass openings length or width wise in the WG to get the smoothest raw midbass response? I know that most guys will say everything is fixable with EQ, but I'd think it would be best to obtain the smoothest FR to start with.
When using oval holes, I always orient them like usual - lengthwise. The main reason is everyone does it like that. And the secondary is that it feels mechanically more solid like that.
ime, the port mid/low port openings are more about getting the smoothest polars for the whole box, than getting the smoothest FR for just the mid-bass.
Gotta get the whole thing to act as a combined FR/phase, device. That said, there's easy ways to do that and hard ways, too ! And yes, the easy ways take DSP.
I've found round holes in corners to work very well for mids (say 300-1000 Hz).
And round holes in the center of the horn on the horizontal top and bottom horn walls, to work well for lows. (say 80-400Hz)
Large horns in general I'd say- and ambience speakers are definitely a nice addition to horns, I think there's something to be said for a sort of "active dither" as offered by very low volume secondary or "ambience" sources.
In my last round MEH, I used centered oval holes for the bass since there were 9 of them, and round ones would be too wide optically. They did not seem to make any trouble to the bands above. What I found out is that for the bass a larger bandpass chamber seems to be an advantage.
Hmm, assuming when not in corners and considering the long side has the narrowest polar response and vice versa same as a horn/whatever terminus; seems to me we'd want the widest polar response to be parallel with the widest horn polars and round holes for square.
Horn mouth polar frequency: c = 10^6/(a*b)
a = wall angle in deg
b = mouth width (or height) in inches
c = -6 dB frequency
metric = (2.54*10^6)/(a*b) in cm