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In Reply to: Re: unrelated posted by hemholtz on March 24, 2007 at 07:17:31:
Once again, thanks for taking the time to reply.Of course we gate the measurements if we want useful data on what a speaker is doing, and unless you have a huge room with the speakers up very high that 10-15 milliseconds you suggest is way too long a window to get clean data.
I agree with your suggestion to address the early reflections and diffuse the late ones, though I take it you're advocating absorbing the early ones whereas I prefer to diffuse them. The problem with using absorption panels for the early reflections is that they keep on absorbing and so suck a lot of energy out of the reverberant field, particularly at short wavelengths. The smaller the room, the more effect absorption panels have because within a given time interval many more reflections will strike and be absorbed by the panel. In my opinion a late-arriving, well energized, spectrally correct, highly diffuse, slowly decaying reverberant field contributes to timbral richness. My goal as far as room acoustics goes is to bring as many of the desirable characteristics of a good recital or concert hall into the home listening room as is practical.
You mentioned certain frequencies "being perceived too loud and hang a little too long to sound natural". In my opinion, this is a significant problem with most reproduced music. I believe the primary cause is loudspeaker radiation pattern anomalies, wherein the speakers are putting out a lot more energy into the reverberant field (6-18 dB more) at some midrange and treble frequencies than at others. Planars and horn speakers tend to be significantly better than cone-and-dome speakers in this regard.
Note that timbre is not established solely by the first-arrival sound, but is strongly influenced by reflections. I can explain why this is so if you would like.
Follow Ups:
10ms-15ms is easily doable with line source dipoles like maggies. many times the only problem is the backwave. here's a measurement taken from the listening position one channel driven. i see one way out there at 17ms and it's less than 20% of impulse. note the gate is at 10ms. 10ms is usually pretty indicative of what the room sounds like in the high and mid frequencies.
i can't stress enough that slow decay is more often than not problematic. slow decay is almost always uneven. you want fast, even decay. what i see often is ineffective treatments. high frequency "suckout" is more often insufficient absorption in the midrange frequencies. cones and domes are famous in this regard due mostly to the floor reflection. a carpet or rug may absorb o.k. in the high frequencies but is still pretty reflective. this is the reason measurements need to be taken. just because there is a treatment somewhere doesn't mean it's an effective one. i personally don't want to listen to my room. recording artists and producers go to great lengths to record the music certain ways. i like it to sound just like the venue in which it was recorded whether that be a theater or a heavily treated vocal booth. you can't get that with slow decay.
Is that the impulse measurement of a multi-driver speaker? If so, it looks pretty good to me.I had forgotten that this is the Planar Asylum and most of the speakers here radiate as line sources, not point sources. I'd still want to window out all first reflections off of walls when I make my frequency response measurements.
There are tradeoffs associated with room acoustics. Fast decay gives better clarity and imaging, while slow decay of gives a richer and more lively presentation. I do not subscribe to the theory that the recording engineers mixed in anticipation of listening under semi-anechoic conditions. Note that typical microphone placement is very close to the performers, so the direct-to-reveberant energy ratio captured by the microphones is much higher than a normally-seated listener would experience.
those are mg3.5r's. that's a measurement from my old room. i'll post some new ones in my gallery when the boys down under at deqx get done upgrading my crossover.so you set you room up to correct for bad mic placement? interestng idea, but potentially at the risk of detail and imaging.
i really don't think the engineer anticipates a room at all. normally they use headphones. the best situation is to get the sound from the speakers to you ear without letting the room change it. it's not as easy as it sounds.
So you use DEQX? That would explain the remarkable impulse response.Well you and I both like planar speakers with well-controlled directivity, and we both like to diffuse the reverberant sound. Apparently we have our philosophical differences about why we do what we do, but what we do is very similar.
If we were far apart in practial application I might quibble with you about the intentions of recording engineers, but I think we're on the same page about enough of this that I'll pass on the quibble.
The Auralex t'fusor looks very interesting. Thanks for bringing it up. A nice oiled hardwood quadratic diffusor would have higher WAF, but at many times the price. I might have to give the Auralex a try.
Do the Auralex t'fusor panels come nested? I'd like something diffusive that can be taken down into a relatively compact package for easy transportation to and from audio shows.
Thanks,
i think you get 6 nested in a box. they fit tight together so you could certainly fit more. i spray painted mine with the speckled paint to make them look like granite. might help with waf. auralex recommends a whole can of spray paint per panel. i thought that sounded crazy, but that's about what it takes. quite a bit of surface area there. i think i cleaned out home depot, lowes, and menards of the one color i was using. i have 16 of them so just the paint was kind of pricey.
i attached them with carpet tape along the outside edges and plastic anchors in the corners. if you spray the anchors after installation they blend right in.
The speckled paint idea is ingenious. Thank you very much for the information and tips.
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