Quite right. I will have to see how it affects other things. Not only could it affect freq response, but also the ETC data.
Remarkably, everything is connected. If I have learned anything, it is that if you change one thing, many other things can change also. Often times, I have to make a choice or compromise.
Case and point:
I think the starting point in any room is determining speaker and listening locations. If this is wrong, its hard to make anything right later.
Given that I started here as well, I observed that the listening position in terms of frequency response wasnt the best place in terms of controlling early reflections.
I would also get substantial changes in the freq response itself moving the listening position forward or back a mere 2 or 3 inches. Sometimes I had to choose whether to deal with a lull at 800hz vs 500hz, and so on.
With reflections, it was the same song. A few inches forward might diminish a reflection at 2k, while making one louder at 700hz, and so on.
I am not going off on this too far in this thread, but parameters such as the height and angle of your ceiling cloud, the thickness and position of your diffraction and absorption panels also affect freq response and reflections as well, also forcing still more choices.
So in my experience, you compromise, you prioritize, and you do a lot of listening at each and every juncture as to not rely on readings alone.
I intend to use a parametric Eq to adjust quickly different configurations as to optimize each. Obviously, if you build a speaker to sound best on axis, and you then play around with the toe-in or lean the speaker to where it is off axis, you might be tempted to reach the conclusion that all configurations where the speaker is on axis to the listener are the best ones. So, I do indeed plan to be a madman.
I have already done this in regards to playing with toe-in. I change the angle I re-measure everything. If I change the height of the speaker, I remeasure everything. If I move the speakers closer together, I remeasure everything, and so on.
Eventually though, it is my hope to dial in the crossover into whatever physical configuration works best after everything I can think of has been tried. This leads to what I feel will be a very controversial conclusion. But here it is.
I plan to dial in the speaker to the listening position criteria. That is, while getting a flat speaker response at 1m at 5 or 10ms is a general aim, the more specific aim is to get things flat (or how I like them) at the listening position. For the listening position in all its reverberation (room reflections) is what I will be hearing, not from 1m away and a controlled gate time. If I have to color the speaker a bit to accomplish this, I am not only willing to, but prefer to, as opposed to hearing unwanted coloration at the listening position or having to rely on EQ to compensate for a flat speaker in a unflat room. Now, most would say, well fix the room. Well, its just not possible, thats why. Perhaps on a unlimited budget and a dedicated room built the ground up with this in mind might get close, the average (my room) wont.
Ive gone a bit off here but I think it very much relates to the thread topic, for the room is critical for good imaging. Certainly, there is more than one right answer, and more than one approach. Again, this is only mine. And as I learn new things, my approach my change. But this is where I am at based on what I know, or what I think I know.
Oh, a total madman would be having the speakers set on linear actuators attached to a circuit that varied the crossover based on the exact angle you set the actuators to
Do you have one? I may want to buy it
Do you have one? I may want to buy it
Oh, I wish. I'm sure if I did, I'd have a bunch of folks from around here buying plane tickets to come check it out, lol.
Sorry to say this (someone has to?), but you are doing it wrong. All the reflections from various room surfaces superimpose with the direct signal to create spatial lobing, witch manifest in the freq. domain as comb filtering. EQ-ing the direct signal is futile fighting this issue. Move an inch and you have different comb-response.
What you need is a source illuminating all the surfaces consistently - no offaxis anomalies from speaker and controlling the early arriving high gain reflections. This gets you undistorted images, good intelligibility and low coloration. Later reflections don't cause image smear/coloration if they are dense, don't protrude too much from the overall response and you utilize a Haas kicker in the 10-20ms region. Remember - there are no absorbers in a RFZ room. (well except the inherent absorbtion in diffusers)
Also you have very early reflections 3ms after direct signal. Agree with everyone else to first zoom at the first 20ms of the individual sources ETC and don't band-limit! (caveat you need a speaker with consistent offaxis performance and treatment that is effective over the whole bandwith above Schroeder freq.)
By RFZ, what I meant was keeping the reflections at the listening position to -15db or less for the first 20ms if possible. I am using a good amount of 4" Owens Corning 703 at the wall and ceiling 1st reflection points to minimize combing. Thick rugs on the floor.
As far as band limiting. I found running individual ETC tests at several frequencies to be more revealing than one overall ETC across the whole spectrum. I DO cover the entire 250-3.6K range, but in 1/3 octave pieces. Their is no reason for me to measure ETC above 3.6k because I dont have any reflection issues above this freq.
The 3ms early reflection you see I believe is a cabinet issue. I am in the process of modifying the cabinets, in part, to try and address this. It may also be due to driver overlap whereby the woofers and mids (both active at the test frequency I illustrated) having different impulse / time arrivals. This issue also I have some ideas on how to address.
Sorry to say this (someone has to?), but you are doing it wrong.
What is required, and I think that Jim does have this mostly correct, is a flat direct field, that is reflection free (or at least surpressed) for 5-10 ms at least. a
will not do this and will in fact make the situation far worse. This is completly the wrong thing to do. You must deal with the early reflections through a narrow directivity in the source that illuminates the listener with a flat direct signal, mnimizes the early reflections through its narrow coverage angle, and has a flat power response so as not to color the reverb field.
I am not sure that I can agree with Jim when he says:
because I have not found that to be the case. I have found that there is a fairly narrow range of design choices that lead to fufilling the criteria stated above. Jim stated his goal early on and that was to have good imaging with good spaciousness, which is my goal too. But he alluded to this being "having his cake and eating it too". But the fact is that this is not a tradeoff situation if done correctly.
The classic approach of using uncontrolled directivity in a room with high damping will not do it that much is certain, but a narrow controlled directivity speaker in a room which is very live forward of the loudspeakers will. The early reflections will be surpressed by the speakers directivity (good imaging) and the spaciousness will come from the high reverberation in the back portions of the room. Problem solved - except that there are not a lot of options for the speaker or the room design in this scenario. But it does work and it works well as years and years of doing this have shown.
4ms is usually too long time difference to be cabinet related. Do this - cut a piece of rope with a length corresponding to the total time of flight of the reflection. You need to have a soundcard calibration for this to work due to internal latency. Secure one end to the mic position, one end to the acoustic centre of the speaker. Rope will have some slack, where you can touch a surface with the rope tensioned is your reflection point.
Or you can use the blocking method - take a piece of absorber and try eliminate the reflection on your ETC display. First hold the piece near the microphone to get a general direction, then 'walk back' the reflection to a boundary guided by the ETC measurement.
One thing more - if you need to look at different band-limited ETC displays, it means that you have one of the following issues(or both): a speaker with varying offaxis dispersion or a boundary impedance causing frequency selective absorption/reflection above Schroeder freq.
Or you can use the blocking method - take a piece of absorber and try eliminate the reflection on your ETC display. First hold the piece near the microphone to get a general direction, then 'walk back' the reflection to a boundary guided by the ETC measurement.
One thing more - if you need to look at different band-limited ETC displays, it means that you have one of the following issues(or both): a speaker with varying offaxis dispersion or a boundary impedance causing frequency selective absorption/reflection above Schroeder freq.
I don't understand, where is the disagreement? Did you just read that I was suggesting to splash all walls with constant 'level' of sound?
Either I can't communicate or you took something out of context? We are getting old?
I did have a non-linear power response. Another reason for my speaker upgrade project.
Both of your suggestions for finding reflection points are good ones, and ones I use. (string and blocking method)
An externally hosted image should be here but it was not working when we last tested it.
This is not my speaker, but it is/was the layout (I retrofitted the drivers with different ones)
As one can imagine, having both mids offset left and both tweets offset right was causing some very uneven power and direct responses. I am having made new front baffles putting the tweet on top, the mid below that and the woofers below that. I am using modeling to determine offset for the mid and tweets (I dont plan to merely put them in the middle of the baffle regarding left to right distances). Additionally, there is a 1/2" lip sticking out above and below the woofers (that you cant see in the picture for the 3 sided dust covers to fit into) causing possible unusual cabinet reflections. This will also be dealt with.
The 3ms ETC reflection is near the top of my list of things to figure out and fix. But I will have to wait until the speaker upgrade project (which also includes crossover upgrades) is completed before I can continue and take more measurements.
Perhaps I did misunderstand as I read
to mean that the sound should go in all directions - "all surfaces" meant this to me. A narrow directivity is key to what I am saying and I did not get this from your discussion.
Fortunately or unfortunately, my speakers have pretty wide dispersion characteristics. So reflections have been problematic. This has forced me, as previously mentioned, to use more absorption in the room than I would like.
And this has had, along with the room being carpeted, the effect of unevenness in the ETC at different frequencies. For example, I have stronger reflections at 800hz than I do at 3.2k. This is still another area that I am seeking to improve. Getting the speakers rebuilt so that the power response of each is a mirror to the other is going to help a lot. Right now, they are audibly different.
The model you outline above (a controlled directivity speaker in a live environment) is one my brother is going to do. I look forward to see how that turns out. But it is almost the opposite of my situation (high dispersion speakers in a somewhat dead room).
Through the use of ideally placed diffusion (qrd panels), I am making progress in livening up things in a controlled fashion (trying to help preserve the upper mid frequency reflections) which now are being over absorbed.
The intended meaning of my statement was meant to address the fact that speakers and rooms can be/are very different. A live room requires a different treatment than a dead one. High dispersion speakers have to be dealt with differently than high directivity ones.
The tradeoff emerges from rooms that are not correct, which probably describes the kind of rooms most of us have.
To the person who has never considered room treatment at all previously, and finally plunges into this realm, the most common mistake is putting something like 1" foam up at first reflection points and hoping the job is now done.
Then you discover 1" foam only helps above 1k, so you put 4" OC 703 up instead.
Then you realize you have now only dealt with frequencies down to 200hz or so.
So then you learn about bass traps, and start putting them in corners and such.
Then, especially in a carpeted room, you then discover that a great deal of your spaciousness is gone due to all the absorption going on in the room. So then you back track, and try to figure out how to minimize where your absorbing and try to preserve more of your reverberant upper frequencies.
I think maybe a lot of us initially go through something like the above process. Some people stop at one of those steps and feel like things are good enough. It is true in some ways that each step, while incomplete in treating all room aspects, improves some of them.
Now, in order to go further than the last step previously outlined, your faced with changing speakers (possibly), tearing down walls and making new ones using different materials, dealing with Haas Kickers, investing in measurement equipment and software or all of the above.
Everyone has limits, either financially or otherwise whereby they wont or cant see this through to the last step.
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Couple quick points.
Try to somehow match your new speaker dispersion to your room to get as much 'reflection free' time as possible.
Think ahead so that you would ideally not have any absorbing panels in your room.
Ideally there should be no 'stuff' between you and speakers and near the speakers, so forget the coffee table in the middle.
If you then identify high gain detrimental reflections, you have couple options. If you only need to take down couple (<6)dB of an offending reflection, use engineered (temporal)diffusers. They will 'trim the hedge' and use those bits to make a more uniform signal decay. There are couple caveats with them - depth, periodicity, minimum distance, bandwith, complexity, price etc. They will absorb also no matter how reflective material you use, but not as much as an absorber.
Seeing you are familiar with the 'string' and 'blocking' method, you could get more detailed answers in a more '(psycho/room)acoustics' oriented discussion forum. (just looked, we are in a multi-way(speaker) subforum)
Try to somehow match your new speaker dispersion to your room to get as much 'reflection free' time as possible.
Think ahead so that you would ideally not have any absorbing panels in your room.
Ideally there should be no 'stuff' between you and speakers and near the speakers, so forget the coffee table in the middle.
If you then identify high gain detrimental reflections, you have couple options. If you only need to take down couple (<6)dB of an offending reflection, use engineered (temporal)diffusers. They will 'trim the hedge' and use those bits to make a more uniform signal decay. There are couple caveats with them - depth, periodicity, minimum distance, bandwith, complexity, price etc. They will absorb also no matter how reflective material you use, but not as much as an absorber.
Seeing you are familiar with the 'string' and 'blocking' method, you could get more detailed answers in a more '(psycho/room)acoustics' oriented discussion forum. (just looked, we are in a multi-way(speaker) subforum
)
Couple quick points.
Try to somehow match your new speaker dispersion to your room to get as much 'reflection free' time as possible.
Think ahead so that you would ideally not have any absorbing panels in your room.
Ideally there should be no 'stuff' between you and speakers and near the speakers, so forget the coffee table in the middle.
If you then identify high gain detrimental reflections, you have couple options. If you only need to take down couple (<6)dB of an offending reflection, use engineered (temporal)diffusers. They will 'trim the hedge' and use those bits to make a more uniform signal decay. There are couple caveats with them - depth, periodicity, minimum distance, bandwith, complexity, price etc. They will absorb also no matter how reflective material you use, but not as much as an absorber.
Seeing you are familiar with the 'string' and 'blocking' method, you could get more detailed answers in a more '(psycho/room)acoustics' oriented discussion forum. (just looked, we are in a multi-way(speaker) subforum
Thanks! All good points. Especially the coffee table. Very bad
So fix your speakers. There is no point in wondering how to get the "best sound" when you know the problems but choose not to fix them. Trying to get the room to "correct" your loudspeakers is not going to get you where you claim you want to be.
$$$$$$$$$ - is why I dont get new drivers
You choose an interesting way to put that " Trying to get the room to "correct" your loudspeakers"
I dont think of it that way. The direct response of my speakers will be fine I think. Its only the polar response that is a bit problematic to my aims. And that can be tamed.
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