Have you measured the 8pe21 close up? How about free air measurement?
The ~800Hz dip seems to be about the same to all directions (you have measured) in which case it could be EQ:d. Edge diffraction would be a dip around on axis and peak further off axis. At least with boxed speakers I've measured it has been so, never measured a dipole. I checked some of your earlier posts, clearly there seems to be some confusion with the measurement setup and / or procedure. You should do what ever you can to weed out the problems to get reliable data repeatedly. Cheerios, have fun!
The ~800Hz dip seems to be about the same to all directions (you have measured) in which case it could be EQ:d. Edge diffraction would be a dip around on axis and peak further off axis. At least with boxed speakers I've measured it has been so, never measured a dipole. I checked some of your earlier posts, clearly there seems to be some confusion with the measurement setup and / or procedure. You should do what ever you can to weed out the problems to get reliable data repeatedly. Cheerios, have fun!
Please see post #118 for 0-180° outside measurements of one 8PE21 without baffle.
Post #127 is a close up measurement per a different approach.
Indeed, the dip around 800Hz shows up at every angle. This was done with the mic in a fixed position and rotating the measurement table around its axis. The table is about 60cm diameter, so there is a chance the edge of the table (protruding beyond the speaker) was creating a reflection. I guess I should remeasure this to remove/confirm that possibility. And while I'm at it measure also close up outside.
At least with boxed speakers I've measured it has been so, never measured a dipole. I checked some of your earlier posts, clearly there seems to be some confusion with the measurement setup and / or procedure. You should do what ever you can to weed out the problems to get reliable data repeatedly. Cheerios, have fun!
Could you elaborate on the confusion with measurement setup and/or procedure? I'm happy to learn
Nothing specific, just noticed many of the messurements you posted have something going on and you asking/someone commenting whats wrong.
I believe as soon as you find one or some of the reasons that made the measurements weird you refine you procedure so that the measurements get better = reliable and repeatable = more cofidence doing the measurements.
By procedure I'm thing preparing the mic, the DUT and the enviroment so that no extra reflections and noise happens. After the measurements are done there is still some steps where some errors can happen, the windowing (IR to FR) and merging the nearield measurements
Please do new measurement set without the table protruding and you are better set!
I believe as soon as you find one or some of the reasons that made the measurements weird you refine you procedure so that the measurements get better = reliable and repeatable = more cofidence doing the measurements.
By procedure I'm thing preparing the mic, the DUT and the enviroment so that no extra reflections and noise happens. After the measurements are done there is still some steps where some errors can happen, the windowing (IR to FR) and merging the nearield measurements
Please do new measurement set without the table protruding and you are better set!
Happy 2022!
After 4 months living with the 18" sitting on a swing (picture on #213), and after being unable to figure out a good looking and stable stand for the swing to allow sitting the MTM above it...my wife said it's time to move on to friendlier aesthetics for the living room. She's been patient but...
I'd like to keep the MTM for now so might need to give away the swing for the 18". Spatial X3 is aesthetically acceptable to her, but that wide panel doesn't appear acoustically good for the midrange. Since my midbass is 18" I'm simulating a 52cm-wide panel by 130cm high to accommodate the MTM such that the tweeter is at ear-height:
I'm crossing over the midranges at 1.8kHz. I could go lower, maybe down to 1.2kHz, but this wide panel would have a dipole peak at 600Hz....way too low. Doesn't look too good.
An alternative could be a 130x52cm frame with a narrow 25cm baffle to hold the MTM:
Another option could be a trapezoid, same height and width (52cm max and 25cm at the top):
It seems the alternative with the narrow baffle looks better on this simulation. Both should be OK to xo somewhere 200-300Hz from midbass to the midrange. While both peak around 900Hz, the narrow baffle is predicted to drop less drastically after the peak. Does this look like a material difference to choose?
After 4 months living with the 18" sitting on a swing (picture on #213), and after being unable to figure out a good looking and stable stand for the swing to allow sitting the MTM above it...my wife said it's time to move on to friendlier aesthetics for the living room. She's been patient but...
I'd like to keep the MTM for now so might need to give away the swing for the 18". Spatial X3 is aesthetically acceptable to her, but that wide panel doesn't appear acoustically good for the midrange. Since my midbass is 18" I'm simulating a 52cm-wide panel by 130cm high to accommodate the MTM such that the tweeter is at ear-height:
I'm crossing over the midranges at 1.8kHz. I could go lower, maybe down to 1.2kHz, but this wide panel would have a dipole peak at 600Hz....way too low. Doesn't look too good.
An alternative could be a 130x52cm frame with a narrow 25cm baffle to hold the MTM:
Another option could be a trapezoid, same height and width (52cm max and 25cm at the top):
It seems the alternative with the narrow baffle looks better on this simulation. Both should be OK to xo somewhere 200-300Hz from midbass to the midrange. While both peak around 900Hz, the narrow baffle is predicted to drop less drastically after the peak. Does this look like a material difference to choose?
Ola Senor,
From experience, trapezoid works quite well to integrate bass and mids with their different width requirements. Think about making the front part trapezoid, as small as physically possible for the bass. Small wings at the sides wich taper to nil on top will add a few dB for the bass and strengthen the whole thing. I once did it for twin 12" - not perfect, but it works fine. Would do it even sleeker on top next time.
All the best
Mattes
From experience, trapezoid works quite well to integrate bass and mids with their different width requirements. Think about making the front part trapezoid, as small as physically possible for the bass. Small wings at the sides wich taper to nil on top will add a few dB for the bass and strengthen the whole thing. I once did it for twin 12" - not perfect, but it works fine. Would do it even sleeker on top next time.
All the best
Mattes
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Can't believe it's been 6 months since my last post. Time flies and is scarce.
I attempted trapezoid flat baffle but holding it didn't work well, so moving on to trying the 18" midbass on a U baffle. How do I know if the U is too deep?
I am now crossing to the 8" mids at 300Hz, and the midbass baffle is 21.6" (55cm) wide x 23.6" (60cm) high. Would 11.8" (30cm) deep U be too much for a 300Hz xo?
I attempted trapezoid flat baffle but holding it didn't work well, so moving on to trying the 18" midbass on a U baffle. How do I know if the U is too deep?
I am now crossing to the 8" mids at 300Hz, and the midbass baffle is 21.6" (55cm) wide x 23.6" (60cm) high. Would 11.8" (30cm) deep U be too much for a 300Hz xo?
I measured the H baffle at varying distances from the front wall. I wanted to measure in-room response, so I placed the mic at the listening position 2.8m away from the speakers in an equilateral triangle. The measurements were made without windowing, later applied IR Windowing at 15 cycle FDW, which is what is shown. The "wall" seen in the picture is cloth with 15cm behind it with acoustic absorbent and resonators. Distances on the chart refer to the distance from the panel to the cloth. I tried from 40 to 100cm in 10cm increments (shown every 20cm for simplicity), expecting higher reach down low as distance grew, but evidently I have a null at 45Hz makes all drop like a rock. There is a clearer difference above 70Hz.
I'm xo the 18" at 300Hz, so looks like 80cm would be better to avoid the dips at 275Hz at 60cm from the wall and 325Hz when at 40cm. I wonder if this material at all since the DSP will bring all of this response down by about 15dB to meet the response in the 55 to 90Hz region.
There is a much different response measured from the left 18". The null registered on the left 18" at 45Hz has shifted to 55Hz on the right, and new nulls at 140 and 215Hz show up.
I also measured the left and right subs.
Responses from the right sub and 18" suggest I will have a hole in response in the 40 to 50Hz...
While the responses from the left sub and 18" suggest I will have a hole between 55 and 65Hz.
I seem to have two issues:
I'm xo the 18" at 300Hz, so looks like 80cm would be better to avoid the dips at 275Hz at 60cm from the wall and 325Hz when at 40cm. I wonder if this material at all since the DSP will bring all of this response down by about 15dB to meet the response in the 55 to 90Hz region.
There is a much different response measured from the left 18". The null registered on the left 18" at 45Hz has shifted to 55Hz on the right, and new nulls at 140 and 215Hz show up.
I also measured the left and right subs.
Responses from the right sub and 18" suggest I will have a hole in response in the 40 to 50Hz...
While the responses from the left sub and 18" suggest I will have a hole between 55 and 65Hz.
I seem to have two issues:
- The very different response between left and right 18" midbass, and the nulls in the response from the left midbass. What might be the cause?
- The holes left between subs and midbasses, both left and right.