Thanks Dr. Geddes! If you call it great, maybe I should just be satisfied. I can drive myself crazy going for better. I've just tried to as you've recommended as best I could.
Too bad about Dr. John--I've never seen him live. He is truly a hero of mine. One of my first cassettes was of him and I've still got it in good working order.
Yea, no matter how the polar response looks in the pseudo anechoic, the response always has great variance in room from position to position. If I had a more heavily treated room I suspect that would be less of an issue. Do you think it is a problem? I pay it no mind above the modal region and post it mostly for others. It seems like no matter what when I average 5 or 10 FR sweeps with flat(ish) measuring speakers, the AVG comes out fairly flat above 1kHz. It doesn't sound like it graphs Anywhere in the room EXCEPT the bass. The other interesting thing is that the RT60 doesn't seem to make any difference in the bass at all. I got to read my Acoustics and Psychoacoustics textbook. There is fascinating things going on up stares perceptually. Must be the integration time vs. signal. I've got to learn more about this subject.
If I remove the room treatments, I get this:
and the treble is livelier.
I placed them like you recommended in that "Room and Loudspeaker as a System" thread a while back. I don't have everything you said to do.
The monitor graphs like this:
Dan
Too bad about Dr. John--I've never seen him live. He is truly a hero of mine. One of my first cassettes was of him and I've still got it in good working order.
Yea, no matter how the polar response looks in the pseudo anechoic, the response always has great variance in room from position to position. If I had a more heavily treated room I suspect that would be less of an issue. Do you think it is a problem? I pay it no mind above the modal region and post it mostly for others. It seems like no matter what when I average 5 or 10 FR sweeps with flat(ish) measuring speakers, the AVG comes out fairly flat above 1kHz. It doesn't sound like it graphs Anywhere in the room EXCEPT the bass. The other interesting thing is that the RT60 doesn't seem to make any difference in the bass at all. I got to read my Acoustics and Psychoacoustics textbook. There is fascinating things going on up stares perceptually. Must be the integration time vs. signal. I've got to learn more about this subject.
If I remove the room treatments, I get this:
An externally hosted image should be here but it was not working when we last tested it.
and the treble is livelier.
I placed them like you recommended in that "Room and Loudspeaker as a System" thread a while back. I don't have everything you said to do.
The monitor graphs like this:
An externally hosted image should be here but it was not working when we last tested it.
Dan
That some super set of measurements from dantheman, both the results and the method. Interesting to see bumps at 55 and 110. But also would be interesting to see a driver impedance curve on the same chart to help separate places where the driver is letting go and where the room is booming.
Long ago I gave up on the prospect of doing anything with mics in my music room but I now see that with untolded hrs of effort and the right chart recording "paper puller" software, might be possible.
Comment about Progress in Human Endeavors: we used to use a General Radio audio oscillator in 1967 that was state of the art. It had a chain that ran around knobs on the faceplate and actually drove the paper puller in synchrony. Does that make you laugh?
Long ago I gave up on the prospect of doing anything with mics in my music room but I now see that with untolded hrs of effort and the right chart recording "paper puller" software, might be possible.
Comment about Progress in Human Endeavors: we used to use a General Radio audio oscillator in 1967 that was state of the art. It had a chain that ran around knobs on the faceplate and actually drove the paper puller in synchrony. Does that make you laugh?
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Thanks to pjpoes for comments and links to sound absorption sites.
I've experimented with motional feedback and had it operating in my subs for some time. I've always wondered how it relates to active noise suppression since it "eats" any motion of the cone that doesn't match the signal far back upstream. Isn't that a definition of active suppression of noise? And we are talking here about low frequencies right down to giving the cone a push with your hand.... it pushes back; it's alive!!!
It always seemed to make the room quieter when I turned on the motional feedback amp. My imagination?
With such a woofer in a corner, could it be doing more than an acoustic "black hole" of the same 15 inch diameter? Could it be disrupting room modes that have some kind of maximums in that spot? Or all the crap in the room?
It truly absorbing noise, then a great gizmo because it also doubles as a fabulous tight woofer.
Any practical or theoretical information appreciated.
I've experimented with motional feedback and had it operating in my subs for some time. I've always wondered how it relates to active noise suppression since it "eats" any motion of the cone that doesn't match the signal far back upstream. Isn't that a definition of active suppression of noise? And we are talking here about low frequencies right down to giving the cone a push with your hand.... it pushes back; it's alive!!!
It always seemed to make the room quieter when I turned on the motional feedback amp. My imagination?
With such a woofer in a corner, could it be doing more than an acoustic "black hole" of the same 15 inch diameter? Could it be disrupting room modes that have some kind of maximums in that spot? Or all the crap in the room?
It truly absorbing noise, then a great gizmo because it also doubles as a fabulous tight woofer.
Any practical or theoretical information appreciated.
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You have to always stop somewhere. Spend several months listening and get to know what you have. THEN, you may find, that there are a few issues. But this idea of change and listen, change and listen - what a quick way to get nowhere.
I saw Dr. J as a headliner to the Neville Brothers. I had always wanted to see Aron Neville, but never managed to do so when he was in his hey-day. I should have since his voice was gone. Just goes to show that you need to take care of a precision instrument like the voice - and the ears.
One thing that amazed me is that I saw Linda Ronstadt at arround her 60th birthday. Her voice was unchanged. She did a short set, to be sure, but what she did was no less than what she's ever done.
Wise words Dr. Geddes. It's amazing how right this sounds right now. Certainly better than I've ever had it. Thanks for sharing the concert experiences as well.
Hey Ben, thanks. Can't believe you are still up! [Not a derogatory comment related to your hmm hm(clears throat), experience😉] The driver's are fine at the problem frequencies--it's the room. I don't know that the problem frequencies would show up in the impedance of the drivers, but it would be interesting to see. I still haven't built my impedance rig. When I do I'll measure everything. If I place the subs/seating elsewhere all sorts of things pop up as seen in previous graphs. I should be a furniture mover. I've done a lot of it over the last few days! Many hrs of sweat built those graphs. Rewarding however.
Is having a VC in the feedback loop of the amp what you are talking about? I remember this was discussed earlier in the thread, but can't remember what the motional feedback thing was. I did a search, but still I'm not sure exactly. Seems there could be different ways to implement that idea. These have the VC in the feedback loop, cast aluminum baffles, huge passive radiators which I think add to the perceived tautness of the overall sound, and all sorts of switches on the back to account for room position. Without all that, this response is not possible. Even then it requires a lot of manual labor.
Dan
Hey Ben, thanks. Can't believe you are still up! [Not a derogatory comment related to your hmm hm(clears throat), experience😉] The driver's are fine at the problem frequencies--it's the room. I don't know that the problem frequencies would show up in the impedance of the drivers, but it would be interesting to see. I still haven't built my impedance rig. When I do I'll measure everything. If I place the subs/seating elsewhere all sorts of things pop up as seen in previous graphs. I should be a furniture mover. I've done a lot of it over the last few days! Many hrs of sweat built those graphs. Rewarding however.
Is having a VC in the feedback loop of the amp what you are talking about? I remember this was discussed earlier in the thread, but can't remember what the motional feedback thing was. I did a search, but still I'm not sure exactly. Seems there could be different ways to implement that idea. These have the VC in the feedback loop, cast aluminum baffles, huge passive radiators which I think add to the perceived tautness of the overall sound, and all sorts of switches on the back to account for room position. Without all that, this response is not possible. Even then it requires a lot of manual labor.
Dan
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Yes, I believe VC in a bridge in a feedback loop is the best way to do motional feedback, by far. But if any other system worked, say an accelerometer glued to the dust cap, it would have the same consequences for noise reduction: a "black hole" for sound hitting the cone... or do I have that exactly backwards?
I dunno about the rest of your paragraph. "Passive radiators"... ummm, sounds Helmholtzian, tuned, and not good; barely acceptable as a necessary evil in an audio system.
Not sure if you got that backwards or not. As soon as I read "black hole" I space out. Thank you, thank you. I write my own material and I'll be here all week. Good night!
OK, but I'm not so sure about the PR being a necessary evil. More like the lesser of 2 evils d/t our auditory acuity in that range, the room being in control in its operating range, no MR leakage, and no chuffing. The PR takes care of that. Can't explain it, but they bass sounds great on these. Any case, right now the bass it cut off at 80Hz and shelved down 3 dB at somewhere around 200-300 Hz. That PR is tuned in the 40s somewhere and probably isn't being used but very little.
I wish I had hard evidence on how audible such a phenomenon should be. I know I don't hear a negative from it compared to my previous sealed system. Actually the bass seems tighter, but I believe that's b/c our perception of bass speed has mostly to do with it's harmonics higher in the frequency range and the things mentioned previously in regards to perceived tautness of these speakers.
OK everyone, start pumping perceptual evidence in here. Inquiring minds want to know more about what we should measure in regards to our loudspeakers and our rooms. It's like teaching to the test. If we understand how we interpret sound, we should be able to design and build better loudspeakers.
yea I know, fat chance. Gotta start reading that text.
Dan
OK, but I'm not so sure about the PR being a necessary evil. More like the lesser of 2 evils d/t our auditory acuity in that range, the room being in control in its operating range, no MR leakage, and no chuffing. The PR takes care of that. Can't explain it, but they bass sounds great on these. Any case, right now the bass it cut off at 80Hz and shelved down 3 dB at somewhere around 200-300 Hz. That PR is tuned in the 40s somewhere and probably isn't being used but very little.
I wish I had hard evidence on how audible such a phenomenon should be. I know I don't hear a negative from it compared to my previous sealed system. Actually the bass seems tighter, but I believe that's b/c our perception of bass speed has mostly to do with it's harmonics higher in the frequency range and the things mentioned previously in regards to perceived tautness of these speakers.
OK everyone, start pumping perceptual evidence in here. Inquiring minds want to know more about what we should measure in regards to our loudspeakers and our rooms. It's like teaching to the test. If we understand how we interpret sound, we should be able to design and build better loudspeakers.
yea I know, fat chance. Gotta start reading that text.
Dan
OK, I don't listen very well. I'm just obsessed. I blame it on John for writing such a cool program. Well I got a little lazy today with perfecting the room with just 5 graphs. It was a little bass shy and a little treble shy so I went about fixin it. I could have lived with the last, but indeed this is a bit better. Now I think I'm actually done..... for a while.
Here's what I came up with:
And just to show something I keep seeing when I do these graphs and perhaps what's more relevant for me in the center seat vs. the room AVG. It always seems to look like this and perhaps why I prefer a slightly dull AVG best:
Then compare that the the same not smoothed pseudo anechoic on axis vs avg:
Cool stuff. The speakers are cross fired FWIW.
Dan
Here's what I came up with:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
And just to show something I keep seeing when I do these graphs and perhaps what's more relevant for me in the center seat vs. the room AVG. It always seems to look like this and perhaps why I prefer a slightly dull AVG best:
An externally hosted image should be here but it was not working when we last tested it.
Then compare that the the same not smoothed pseudo anechoic on axis vs avg:
An externally hosted image should be here but it was not working when we last tested it.
Cool stuff. The speakers are cross fired FWIW.
Dan
Thats some pretty rough looking data. I'd hate to judge anything on it, but youy have the right idea.
Do note that "first surround resonance" is different from (and often lower than) the more obvious "cone breakup", and that in fr plots it often produces a null rather than a peak.
(I didn't think great accuracy was necessary and this plot showed what I wanted to show.)
Thanks for your opinion.
Was it obvious to you where that resonance was?
No . . . the response curve is too ragged, indicating all sorts of resonances and breakups, and making it hard to identify the cause of any. That's why I stopped using large drivers for anything but subwoofers years ago. There is something really odd going on at 600 Hz. . . . anything that can produce a blip that large in the impedance curve should be looked at . . . (and a smaller one at 900-1000 Hz., but I don't know what those are either). There's also the obvious big null a bit below the most obvious breakup . . . the cone, or at least the edge of the cone, is out of control.
But as I said, I stopped using big cones up high because they are unpredictable and unmanagable.
IMO surround resonances has a little common with a cone diameter. All drivers has surround and and surrounds are the weakest parts of radiating surfaces and starts resonate first (sometimes supported with cone rim resonance). Surrounds differs in weight, geometry, material and width. These properties are responsible for where the resonance is and how well is damped. Most often it is in the range of 700Hz (for heavy half-roll or wide pleated) to 1K2 Hz (narrow pleated) and doesn't make peak at IMP curve but small ripples or plateau.
Resonances below probably comes from spider and airborne resonances in motor or basket. Nevertheless they can be EQ'ed out perfectly if they are not excursion dependent.
Resonances below probably comes from spider and airborne resonances in motor or basket. Nevertheless they can be EQ'ed out perfectly if they are not excursion dependent.
I compiled a set of polar response graphs from speakers I've measured.
Behringer B2031P:
Then stuff the ports with cotton:
Then the Behringer 1030A:
Then the Mackie HR624 mk2:
The JBL LSR2325:
Last and least the KRK Rokit 6:
Dan
Behringer B2031P:
Then stuff the ports with cotton:
Then the Behringer 1030A:
Then the Mackie HR624 mk2:
The JBL LSR2325:
Last and least the KRK Rokit 6:
Dan
You're welcome Markus. You know just looking at those pictures will tell you more about how each of those sounds (from about 8-9kHz down) than if if I had written a nine hundred, ninety-nine words on each. The only one with a resonant looking impulse is the B2031P. The others are pretty good. You can really see in the FR though. From what I ca see/hear, the polar response is the most important thing particularlt betwen 1-8 kHz. If that isn't right, why go on?
Dan
Dan
The B2031P is an incredible value when the ports are closed. They'd probably make up some pretty decent surround speakers. Did the cotton you used completely block the ports?
Well, you can still feel a little air pushing through them at high volumes(90ish dB range), but not much at all. They are filled bottom to top. Personally I think they are the best value in loudspeakers. The 1030A might bump them out of that slot depending on what you are looking to do. For near field, they are great. They start sounding muddy when cranked where the 2031 can dish it out. Of course even they are not going to hang with PA type speakers, but for bookshelves... Right now my HT is made up of 5 of them with a couple subs. Not to brag, but it's darn good for the money. Audyssey's EQ is a big plus as well. I'm happy with it.
Dan
Dan
Looking back at this testing it was a great test comparison. But I have to say I could not enjoy the B2013P even though it measures well. Isue my pair for the enclosuresI compiled a set of polar response graphs from speakers I've measured.
Behringer B2031P:
Then stuff the ports with cotton:
Then the Behringer 1030A:
Then the Mackie HR624 mk2:
The JBL LSR2325:
Last and least the KRK Rokit 6:
Dan
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