Hello,
I would like to be able to take better speaker measurements and am wondering how I can do so with a limited ceiling height?
Outdoor measurements are not practical where I live due to either weather or too much environmental noise.
Has anyone successfully taken the corner of a room and setup sound deadening materials on the ceiling and floor to allow an impulse response much greater than 4ms in a room with only 7' ceilings?
I was thinking of something like 6" of Safe'N'Sound Rockwool in sort of an amphitheater configuration radiating out from one corner of the basement three meters (10 feet) in all directions with the speaker stand 1 meter out from the corner and the mic 2 meters out from the corner.
Another option was to do the same sort of configuration with large acoustic foam triangles.
Or, if the ceiling and the floor are going to be closest reflections between the speaker the mic, just place the speaker and mic twice the distance from the walls as the distance between the speaker and mic and just treat the floor and ceiling between the speaker and mic.
Don't know if any of these ideas would work or if they are dumb.
Anyone taken any significant steps to improve indoor measurements?
Thank you,
David.
I would like to be able to take better speaker measurements and am wondering how I can do so with a limited ceiling height?
Outdoor measurements are not practical where I live due to either weather or too much environmental noise.
Has anyone successfully taken the corner of a room and setup sound deadening materials on the ceiling and floor to allow an impulse response much greater than 4ms in a room with only 7' ceilings?
I was thinking of something like 6" of Safe'N'Sound Rockwool in sort of an amphitheater configuration radiating out from one corner of the basement three meters (10 feet) in all directions with the speaker stand 1 meter out from the corner and the mic 2 meters out from the corner.
Another option was to do the same sort of configuration with large acoustic foam triangles.
Or, if the ceiling and the floor are going to be closest reflections between the speaker the mic, just place the speaker and mic twice the distance from the walls as the distance between the speaker and mic and just treat the floor and ceiling between the speaker and mic.
Don't know if any of these ideas would work or if they are dumb.
Anyone taken any significant steps to improve indoor measurements?
Thank you,
David.
Physics is not on your side here. If you're dealing with reflections measured in feet, then your sound deadening must also be feet in thickness. A few inches of sound deadening will only have a positive impact at frequencies where a gated measurement would already eliminate reflections.
Easiest solution is to measure outside, with ground plane measurements for low freq.
Easiest solution is to measure outside, with ground plane measurements for low freq.
I know its not the answer you wanted but i just took my first outdoor measurements to do speaker correction the other day and noticed a huge difference in the evenness of the tonality. I was going to write a post about it.
Bottom line I think what I learned is that its better to bring neutral speakers into a room and the room impart its own charecter on the sound rather than impregnate the room sound into the frequency response by measuring indoors. Im still not sure all the reasons why. Reflections is a large part of it though
Bottom line I think what I learned is that its better to bring neutral speakers into a room and the room impart its own charecter on the sound rather than impregnate the room sound into the frequency response by measuring indoors. Im still not sure all the reasons why. Reflections is a large part of it though
I'm in the a similar boat as far as speaker measurements go, so my long-term pipe dream is a DIY Klippel Nearfield Scanner... hinging on large improvements in my math and programing skills (see here and here). That being said, I'm always on the lookout for novel ways of getting useful data, so I'll pass on an interesting looking option that uses delayed-sum beamforming:
(PDF) Quasi-Anechoic Measurement of Loudspeakers Using Beamforming Method
(PDF) Quasi-Anechoic Measurement of Loudspeakers Using Adaptive Beamforming Method
(PDF) Quasi-Anechoic Measurement of Loudspeakers Using Beamforming Method
(PDF) Quasi-Anechoic Measurement of Loudspeakers Using Adaptive Beamforming Method
Limited ceiling height is difficult, I have considered some of the same things. The only one that makes much sense to me is to put enough absorbent on the floor to be able to have the speaker closer to the floor and further from the ceiling to get a longer gate time.
As was said above that does need quite a thickness of material, 6" of Rockwool is probably not enough to offset the height change. Low density fibreglass as thick as possible would give the most broadband absorption.
I have got a lot of spare fibreglass sitting in my shed which I intend to experiment with in this way when I have a speaker to measure.
I don't think it will be able to remove the need for a groundplane measurement but I think it could help to give a little more resolution between 300Hz and 1K where normal gated measurements are way too smoothed by the gate.
The beamforming works but the amount of measurements needed to have a meaningful effect makes it seem impractical for polar measurements.
That's what I've been calling "Toole's Critique": the purpose of EQ is to fix the speaker, not the room (which is what it is and your brain can "learn the room"). The jury is still out, as far as I can tell.
But I must say, as an empiricist, I have another viewpoint. I put my mic where my head usually is when listening to music. After all, that is the "bottom line" reference. My goal is not to confirm the perfection of the design sim, but to have great sound quality at my chair.
The two viewpoints conflict. Too bad if you hold both.
Gosh, I wonder how it would work to have two sets of DSP EQ running simultaneously, one to make the speaker flat/Spinorama and one for the room and tailoring sound to your personal taste?
B.
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Isn't that what most people who are into DIY audio try to do anyway one way or another?
Anyone measuring with a mic and setting their EQ accordingly is not doing that. Unless they later realize they better re-tune more to their liking (which includes the kind of recorded music they favour).
It is widely agreed that "mic flat" doesn't sound best (possibly because it may not correspond to "ear flat").
B.
It is widely agreed that "mic flat" doesn't sound best (possibly because it may not correspond to "ear flat").
B.
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Sadly, you´ll need something like this:
Not kidding, you can´t cheat Physics.
You can try to minimize outside noise; I measure outside but at, say, 3AM to 5 AM, on non-windy days.
Not kidding, you can´t cheat Physics.
You can try to minimize outside noise; I measure outside but at, say, 3AM to 5 AM, on non-windy days.
A good speaker set should not measure flat at sweet spot. Often show up as a slope from left to right.
Perhaps. Both methods have their limitations. The human race seems obsessed with measuring things and unless you are using the latested technology to measure (and correct) your speakers you probably won't be taken seriously here, even to the extent of being told to go away and not come back until you post some.
I’ve always been a ‘empiricist’ and didn’t even realize it 😛
When it comes down to it what you hear at lp is most important, you can manipulate the xo to fit the room……granted that makes for a specialty set of speakers but if for some reason you need to change rooms you either redesign the xo or build a new speaker!
Not the popular view, but I’ve never been one of the popular kids anyhow 😀
can you be more specific?
what is wrong your current measurements?
what do you want to measure?
Good question.
Gated measurements are wonderful for >800Hz
Nearfield are excellent for <200Hz
It is that baffle step, no mans land between 200-800Hz that I would like to improve.
Thank you,
David.
Agreed! With perhaps 100ish needed to get meaningful data for each angle of orbit, that pushes it into the realms extreme dedication.
But on the other hand, it appears that the processing for it can be done entirely with readily available freeware, so it might be worth it for getting just the on-axis or listening window response.
While I don't doubt it can be done with absorption, from a practical standpoint I haven't found using absorbing materials to give me the confidence of a consistent reading so I avoid going there unless I have little choice. I've tried all practical thicknesses of bedding, couch cushions and roofing batts, cubby house or open. If I dedicated the effort to building an anechoic chamber that's one thing, but I don't think so.
Have you ever tried isolating the three corner wall reflections during placement, trying to blank one wall to control the nulls in the lower to mid hundreds?
In any case, you can always get clean down to some point. Even if it's only one octave more than the crossover frequency.
Have you ever tried isolating the three corner wall reflections during placement, trying to blank one wall to control the nulls in the lower to mid hundreds?
In any case, you can always get clean down to some point. Even if it's only one octave more than the crossover frequency.
You can get down to 200 Hz (with spl suppressed enough in level for a decent measurement) gated by:
1. being in a large enough room (that has everything in it moved far enough away or out of the room).
2. putting the loudspeaker in a room with at least 7 feet from any wall (or any reflective surface other than floor and ceiling).
3. putting 8 inches of *rockwool on the floor around the loudspeaker 1 meter + (and a bit more around the mic./stand to the 1 meter + surrounding the loudspeaker). IF you have a driver that extends below that 8 inch depth (ie. really close to the floor) then raise the loudspeaker slightly to accommodate it.
4. putting 8 inches of rockwool on the ceiling centered on loudspeaker and extending out at least a meter in all directions. Note: IF you are in a room with substantially higher ceilings (say 12 feet or more) then you might not need this depending on how close the driver (operating in that bandwidth) is to the ceiling.
*some pillows (+blankets, etc.) can also work as a good substitute, in fact if you have enough of them and you are doing this in a large enough room with 12-14 foot ceilings - then you don't have to spend any money on rockwool.
If you don't have a dedicated room for this then it's a major hassle (moving everything about and setting it all up), lighting fixtures (usually centered in-room on the ceiling) complicate it even more.
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I have wondered for some time if it might be feasible to redirect the sound at the points of initial reflection (at wall/s, floor, ceiling - whatever is/are the nearest critical reflection/s).
I think that in principle this should be doable - but from what frequency upwards it would yield (very) good results, and how to best design the reflectors in order for them not to introduce their own (new) interfering reflections? Finally, would this be "easier" than simply applying absorptive material of sufficient thickness?
I think that in principle this should be doable - but from what frequency upwards it would yield (very) good results, and how to best design the reflectors in order for them not to introduce their own (new) interfering reflections? Finally, would this be "easier" than simply applying absorptive material of sufficient thickness?
Gated measurements and combined nearfield and farfield measurements are the way to go. Any sound absorption on reflection points in a normal room will most likely only make it harder to choose the correct time window for the gated measurements
Also note that "gating" does some effective "averaging/smoothing" closer to the gate freq..
If you have some linearity issues within an octave and a half (above) the gate freq. - then they likely won't show up (or be much smaller in magnitude than actually present). Undamped (no/low fiber fill) transmission lines for your midrange/midbass can be particularly problematic along with "fullrange" drivers in "back-horns".
Still, in this respect then it is better to have as low a gate freq. as PRACTICAL so that your upper freq. response is more accurate (..with 350 Hz and moderate pillow/blanketing around the loudspeaker and mic. usually being sufficient in a decent sized room).
If you have some linearity issues within an octave and a half (above) the gate freq. - then they likely won't show up (or be much smaller in magnitude than actually present). Undamped (no/low fiber fill) transmission lines for your midrange/midbass can be particularly problematic along with "fullrange" drivers in "back-horns".
Still, in this respect then it is better to have as low a gate freq. as PRACTICAL so that your upper freq. response is more accurate (..with 350 Hz and moderate pillow/blanketing around the loudspeaker and mic. usually being sufficient in a decent sized room).