You have two woofers in a box which are in varying states of relative phase because they are independently time locked to something external (the listening position). These sources also have varying directivity with frequency due to the fixed baffle size. You call them bipoles but that is questionable, and doesn't help. Besides, what would be the benefit if they were?
Oh… I see your point about it not technically being a bipole I guess., sorry for the confusion. I don’t know what to call it then… a front and rear facing woofer cabinet I guess. Corner loaded, crossed at 200hz, I wonder what its pros n cons would be. In particular, time and phase aligned, I wonder would it sound desirable
Those speakers that are meant to be corner loaded… I forget what the name of that brand is… Or even some design that I don't know of, that is meant to be placed in the corner with a woofer facing the corner, how high they typically ran???
Matter of fact, how is placing a rear firing woofer into a corner, not very similar to a Lascala???
Matter of fact, how is placing a rear firing woofer into a corner, not very similar to a Lascala???
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The Klipsch La Scala is a purpose designed front loaded horn that does not fire in to a corner:
A woofer in a box facing a corner has little similarity to a free-standing horn designed for reproduction up to 400 Hz.
A woofer in a box facing a corner cavity will produce deep cancellation notches similar to your slot-loaded dual 18".
Any sound it produces at your listening location will either be off axis diffraction or ceiling reflections.
If you are planning to use some woofers for <120Hz, and others from <120Hz up to ~300Hz, putting them in the same box reduces system flexibility.
You could use your sealed 15" boxes to experiment with the configurations you have been speculating about.
As long as my sim is near real world result, the redesign of the slot should take care of my issues except for being stuck towards a lower crossover. Using EQ to smooth FR shows hope to have a normal GD through the XO region, and the null is near 400hz allowing the intended 200hz xo to develope fully.
Its not as black as it looks, its a very dark chocolate due to a few factors, mainly a thick last coat lacking black pigment, thus showing the color of the varnish. I could do an application of black and keep things glossy, but I am imagining a super black matte, and have means to do so.
I think I am doing good? I went with an easy favorite for me, charcoal type colors. The minwax antique gray has a hint of blue, another one of my favorites. In low light they appear black, which was my intentions so I'm happy about that. Hopefully I can get home soon enough to set them out in the sun so they can bake and speed up to curing before the next application
Looks like charcoal! I used a matte charcoal to finish my subs and use as a front baffle color. Looks great! You going matte? are those wet or you going gloss?
Rob 🙂
Rob 🙂
It's interesting that I thought of this when I saw this comparison.
On first looks it appears to be a comparison by level, with resonances being the most affected suggesting a variation in Re might be involved.
Details may be found through this thread - https://www.diyaudio.com/community/threads/why-do-tweeters-compress-at-the-top.413450/
^ This is a little different than what I was talking about. The linked thread is talking about thermal compression, a well known phenomena that I looked at decades ago. It is a critical factor in a high SPL loudspeaker system. After one test that I did I found that one of the crossover inductors had melted and no longer working correctly! So it's a big factor.
My comment above was about thermal modulation where the varying music signal dynamics would modulate the output sound thus inhibiting its sound quality. The thermal time constants turnout to be too long for this to be a significant effect, but the long term Thermal compression is well known.
My comment above was about thermal modulation where the varying music signal dynamics would modulate the output sound thus inhibiting its sound quality. The thermal time constants turnout to be too long for this to be a significant effect, but the long term Thermal compression is well known.
The discussion goes that the tweeter is swept when cold. It was labelled compression, there might be some confusion.
I'm not confused, the two things are different and from my reading they were talking about long term compression, not dynamics.
They did a classic test of FR at various signal levels where the higher SPLs heat the voice coil causing significant changes (as shown.) But, as I said, they can also heat the crossover inductors changing their DC values - a not insignificant effect.
They did a classic test of FR at various signal levels where the higher SPLs heat the voice coil causing significant changes (as shown.) But, as I said, they can also heat the crossover inductors changing their DC values - a not insignificant effect.
I am really digging the color. Does any know why this happens, of you see on the edge, the finish seemed to avoid this area, as in, withdraw from it after being covered. I tried the blackest black acrylic on this area and didn't like it, then wiped it off with ethanol, then sanded the whole horn. I was thinking maybe elevation but that don't make sense either. Varnish can be used over acrylic so even if it was acrylic residue it makes me wonder.
I'd like to achieve a mirror finish but not going to get my hopes up, as a noob. It seems fluidity is factor and drying time as well, which suggests that I switch to ethanol as a cutting agent. Then again, this being a 3rd coat, maybe if I wet sand with a fine grit, it will get me there.
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OK, not a beat a horse dead, and as said before, acoustics is complicated. I have not measured outside, which is what I should but until then, this is what I think I know about my slot loaded woofers.
If I am making sound judgment, Group Delay as shown in the sim, should be realistically achievable given how the deviations occur, thats is, its relationship to boundary distances within the slot. Looking at these in room measurements at 1m, I would be inclined to think the room is a strong apart of the reason why I have the huge at 254hz in the upstairs measurement (green) and not in the basement measurement (red).
Looking at my HR sim, Group Delay has not, the giant swings of the upstairs measurement, which is why I draw the conclusions I do. The boundary distances within the slot would create GD readings some 17-80ms long. I really need to get outside 🤦... The upstairs had hard wood floors/ceilings and the basement has carpet/padding over concrete, with acoustic tile, I am sure this plays a huge factor as well,
If I am making sound judgment, Group Delay as shown in the sim, should be realistically achievable given how the deviations occur, thats is, its relationship to boundary distances within the slot. Looking at these in room measurements at 1m, I would be inclined to think the room is a strong apart of the reason why I have the huge at 254hz in the upstairs measurement (green) and not in the basement measurement (red).
Looking at my HR sim, Group Delay has not, the giant swings of the upstairs measurement, which is why I draw the conclusions I do. The boundary distances within the slot would create GD readings some 17-80ms long. I really need to get outside 🤦... The upstairs had hard wood floors/ceilings and the basement has carpet/padding over concrete, with acoustic tile, I am sure this plays a huge factor as well,
(3ft away from... mic14.5 inches off ground)
(3ft away from... mic 14.5 inches ground with top baffle off)
I am showing the below for speculation of ringing. I think the ringing can be solved with EQ, as its not horrible considering the raw FR shown above
(Top on)
(top off)
Damping material really takes care of most of the issue, but I am stuck between how to make it look presentable vs not wanting to have to use damping material in the first place, except for inside of course.
@weltersys @gedlee @GM
Ok, lets say, I now have 3 18"s for each box now ☺️
I thought about feeding the third woofer at the beginning of the line. As many problems as the slot causes, after damping material, potentially the resonance issues are solved, if and when that comes to pass, it is a point source for the bandwidth it covers, approximately 20-200 hertz.
Being corner loaded really helps out the frequency response, and when I play with Rew room sim, I don't get a drastically different response if I surround my self with quadratic stereo subs instead of just the two in the corner. Thus the interest in keeping all sources confined to 2 positions, in the corner.
There are two other configurations I see entertaining. One; 18" on front baffle, 18" on bottom baffle, and a 18" on rear baffle, the bottom/rear drivers low passed near 1/4wl to front driver which turns out to be about 100hz. Two; one 18" on front baffle, and 2 18" on the rear baffle diagonally. Low passing the rear drivers the same as the first scenerio. A bonus scenario of facing the slot loaded woofers to the rear and then place a 18" on the now front baffle. With this scenario I might have to have the motor facing out to keep current dimensions of box.
Any of those decisions sound like the better one?
Keeping all woofers with the mains allows me to use only 2 amps, as I can wire a passive low pass filter to the woofers that need it using one channel to drive them all.
You guys are better than me at seeing the pitfalls up front so I ask of your opinions
Ok, lets say, I now have 3 18"s for each box now ☺️
I thought about feeding the third woofer at the beginning of the line. As many problems as the slot causes, after damping material, potentially the resonance issues are solved, if and when that comes to pass, it is a point source for the bandwidth it covers, approximately 20-200 hertz.
Being corner loaded really helps out the frequency response, and when I play with Rew room sim, I don't get a drastically different response if I surround my self with quadratic stereo subs instead of just the two in the corner. Thus the interest in keeping all sources confined to 2 positions, in the corner.
There are two other configurations I see entertaining. One; 18" on front baffle, 18" on bottom baffle, and a 18" on rear baffle, the bottom/rear drivers low passed near 1/4wl to front driver which turns out to be about 100hz. Two; one 18" on front baffle, and 2 18" on the rear baffle diagonally. Low passing the rear drivers the same as the first scenerio. A bonus scenario of facing the slot loaded woofers to the rear and then place a 18" on the now front baffle. With this scenario I might have to have the motor facing out to keep current dimensions of box.
Any of those decisions sound like the better one?
Keeping all woofers with the mains allows me to use only 2 amps, as I can wire a passive low pass filter to the woofers that need it using one channel to drive them all.
You guys are better than me at seeing the pitfalls up front so I ask of your opinions