With the drivers stacked on top of each other, the height is increased to ~34". I care because I am trying make sure the tweeter doesn't get too high of a height.
In the picture above, the enclosure is reaching about 26" inches. At 34" the drivers wouldn't have to be staggered.
I made a comment that MTM is for strict critical listener. I think there is truth to the statement, but I also think that TM configuration is just as effective because, if MTM was so great, why isn't there many more designers using it? Then again, the synergy type configurations are the same, in the aspect of symmetrically spread sources, and no more popular.
In the picture above, the enclosure is reaching about 26" inches. At 34" the drivers wouldn't have to be staggered.
I made a comment that MTM is for strict critical listener. I think there is truth to the statement, but I also think that TM configuration is just as effective because, if MTM was so great, why isn't there many more designers using it? Then again, the synergy type configurations are the same, in the aspect of symmetrically spread sources, and no more popular.
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Science is not a democracy (I believe Dr Geddes coined this, here at least 😉 )
Your logic fails because you presume that everyone possesses a full understanding of how it works and deserves an equal vote.
Secondly while generally some things don't work in all situations, some other things do. If there is disagreement then sometimes there's a good reason for it.
@AllenB you obviously have spent lots time on this topic. What's your position on my controversy between MTM vs TMM 2,5way? The MTM version would have the closest and identical spacing of the tweeter and 15"...the 18" would have closer spacing as a MTM but slightly higher spacing as TMM. My ceilings are low, just under 8ft. Xovers are relatively low, so comb filtering isn't horrible either configuration. Playing either as an 2way seems to be an option as well.
I understand that with a MTM you ideally would like a two identical source above/below the tweeter, identical refers to acoustical conditions as well. So I start out with lesser than that from begin with one woofer at the floor and the other mid air, but closer to the ceiling. That's probably not a deal breaker I presume. With a 2.5way MTM the sources will not be identical in passband, so the image will move some near crossover. As MTM 2way my lowers would still handle more bass spectrum. As a TMM 2way or 2,5way things are more traditional. I think I have the potential to obtain TM like characteristics with a TMM. I am finding it hard say which way is objectively the potentially more Accurate way.
I understand that with a MTM you ideally would like a two identical source above/below the tweeter, identical refers to acoustical conditions as well. So I start out with lesser than that from begin with one woofer at the floor and the other mid air, but closer to the ceiling. That's probably not a deal breaker I presume. With a 2.5way MTM the sources will not be identical in passband, so the image will move some near crossover. As MTM 2way my lowers would still handle more bass spectrum. As a TMM 2way or 2,5way things are more traditional. I think I have the potential to obtain TM like characteristics with a TMM. I am finding it hard say which way is objectively the potentially more Accurate way.
The centralization of the lower channel, over the tweeter, is the benefit. Also possibly a better FR as these woofers both will represent the bottom register. With the large size of the build, The lower floor dwelling woofer would sit some 50" below the top woofer. What piqued my interest was how well stereo works in close proximity. My two desktop monitors do a job well creating the phantom center. If I were to try to do things correctly, as in, way more effort than just randomly setting speakers to my left and right on a desktop, the results would be fine I think. So I take that logic an say, after proper voicing and time alignment, the centralization, ie the phantom center created over the tweeter hopefully, should be pretty good, right?
Downside.... Potentially worse FR via Comb filtered reflections? I potentially may not like the loss of "air" or reverb, via the change in the ceiling reflection. Potential for unsuccessfully predicting the performance of two sources that ultimately are not identical.
I guess one could argue that unless both midrange sources are identical for mids of an MTM, it would be a step away from accuracy. One could argue the same message towards 2.5way or 2 way MTM, or even a 3 way since the same is true for any drivers in crossband or redundancy. I have enough variables already so it would seem as I need not complicate things with a unique never seen before MTM lol.
Downside.... Potentially worse FR via Comb filtered reflections? I potentially may not like the loss of "air" or reverb, via the change in the ceiling reflection. Potential for unsuccessfully predicting the performance of two sources that ultimately are not identical.
I guess one could argue that unless both midrange sources are identical for mids of an MTM, it would be a step away from accuracy. One could argue the same message towards 2.5way or 2 way MTM, or even a 3 way since the same is true for any drivers in crossband or redundancy. I have enough variables already so it would seem as I need not complicate things with a unique never seen before MTM lol.
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I hear this a lot but it seems people fear it more than realise it. We've learned on this thread that imaging is centralised on the tweeter, and in extreme cases where the vertical spread can be detected the effect isn't as devastating as people tend to assume it would be. Centralising isn't essential to best imaging.. near or far listening.
Comb filtering has to do with multiple sources with a delay. Why would this be specific to either MTM or TMM?
You can engineer level or tilted lobing conditions either way. Adding a second M to a TM which has a 0 degree lobe, to make a MTM, doesn't do a whole lot there.
What about the vertical directivity of the pair?
I mean the woofers are working together below 67hz. I don't know how to appreciate it. Maybe you can tell me? Wide pair spread apart the most will cause more directivity. Thats all I know.
isn't it though? Phantom Center is created with an MTM no less than Phantom Center is created with a stereo set of loudspeakers.
"cases where the vertical spread can be detected the effect isn't as devastating as people tend to assume it would be" I agree, its not devasting but neither is a degree of other distortions to accuracy that we tolerate.
"Image shift - Sound dislocated from its correct position, to be more left and / or right of center." Stereo only gives left and right information, any deviation on the vertical axis is a distortion. Perfect implies no distortion or at least no perceivable distortion. With multi ways we use distance to hide the attribute of the sound being spread on the verticle axis.
well if its a MTM/TMM 2.5 nothing special going there. With MTM 2way there is additional comb filtering on the other side of the tweeter instead of just one side. A TMM 2 way will have additional comb filtering due to the set of woofers that are not in the same location. More potential for the off axis sound to be distorted, thus the final FR. I am generalizing in a case that really can't be, because each design will potentially be unique in some way.
I asked for your position on preference.
Are you perhaps conflating comb filtering with lobing? I'm a little confused.
It sounds as though you have made up your mind. It sounds as though you measure imaging accuracy with a measuring stick. I don't use image size or shape to judge it's quality even though quality can affect those attributes.. unintuitive as that may be.
I am confused. I thought that lobing was a part of comb filtering. Sorry for the, confusion.
The word point source, or point source like, comes to mind. I mean I must come to one of those, step left or right but not ahead type of situations. I can live with a number of conclusions. What I wonder is which will lead to better choices in the mix, in particular EQ.
A point source. One of the more widely used and defined terms of recent years. A point source is a theoretical source shape which creates spherical waves, just as a line source produces cylindrical waves.
Not that it can't, but where did it come to mean that you'll get pinpoint imaging? Could you name the source shape in a blind test held at a random location?
Let me throw a spanner in the works for you. If a mid and woofer were spaced at 10cm and together produced 350Hz (wavelength 10 times bigger) then technically you might refer to that as a point source...
What about a driver playing above where it's a small source, like a woofer playing treble. Since it's a large radiator it's an array, perhaps a plane wave source but not a point source. Since there's diffraction at various places it also isn't a point source.
Words are funny things. So is perspective.
Not that it can't, but where did it come to mean that you'll get pinpoint imaging? Could you name the source shape in a blind test held at a random location?
Let me throw a spanner in the works for you. If a mid and woofer were spaced at 10cm and together produced 350Hz (wavelength 10 times bigger) then technically you might refer to that as a point source...
What about a driver playing above where it's a small source, like a woofer playing treble. Since it's a large radiator it's an array, perhaps a plane wave source but not a point source. Since there's diffraction at various places it also isn't a point source.
Words are funny things. So is perspective.
I think I mean to convey a single point. When listening to a single channel. It should sound as if all sound is coming from a single point. That is the illusion we look to create.
We don't have to delve on this, but I assume to hear what I see, mainly because I sit so close. I read this;
Because I am using the larger woofers I have been dealing with large CTC, and so far successfully due to the ability to cross low. Sitting at 1 meter makes the loudspeaker vulnerable.
Like I said, I agree. I am curious how this aspect of Image affects perception of tone/spl. The mental picture of sounds coming from more than one place versus coming from the exact same place, what effect does it have on our perception of tone and spl. Mastering Studios have a percentage of designers using Coaxial systems for the mastering monitor. The Genelec Ones have been popular. I find that interesting.
Maybe we are under appreciating the stereo effect MTM creates. Anyone building a synergy is very happy for this stereo effect. It seems to come down to a matter of how well its executed.
@AllenB Do you think. My proposed MTM configuration has the potential to be.... well executed?
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Here's a test for you. Play your stereo content in mono. It should sound as though everything is coming to you through a small imaginary window that leads in from outside your room. It should remain as you walk around. If you haven't achieved that then you should ask yourself some questions.
It's been discussed many times on the forum that using a Synergy style horn has a plus for the designer that it helps match power and directivity. This can also be done with a conventional layout but it's a more complex procedure. What do you think that will do to the anecdotal evidence that is readily available to read about?
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it should? The listening window width is not an absolute. If you are referring to what the technical definition referred to as a point source, then ok, I understand. I used the word wrong apparently. As I meant, a single point. I want directivity. Still, listening to a single channel should sound as if listening to a Full Range Driver with great FR and Dynamic ability.
I didn't mention the "listening window" which is talked about in the Spinorama specification and I didn't imply it has any such meaning.
Well things are only meant stay sounding "the same" within the listening window, not as you "walk around". Maybe its the desire for non colored reflective energy that you are referring to.
You seem to make certain assumptions.
Not the least of which is the definition of 'listening window'. Where have you read that it has any meaning for a given listening seat?
Not the least of which is the definition of 'listening window'. Where have you read that it has any meaning for a given listening seat?
cannot use that word like that either.... Ok replace listening window with sweet spot.
Mono tests are always good and give some information about the speaker and room. But let's have a look what's possible with Stereo.
Switching to Mono and having a single, dry source (voice or instrument) should give a pin point representation exactly in the middle between the speakers. Cause that's what Stereo can do - build a phantom source. Effects in the music can mess with that but with a reltively dry signal you should have the feeling you can "grab" that source blindly. It's stable at one position and no hint of speakers left or right.
When you move to the sides - the source will also move. There are no time delay stereo effects in Mono so level effects will count. And when you get closer to one speaker and get more distance to the other speaker - the phantom source moves. Just a little in the beginning but depending on your position in the room it will move strongly (e.g. close to one speaker).
Whatever is happening differently to this is not what "Stereo to Mono" is doing - it is a combination of room sound and reflections and speaker behaviour. Many prefer a more reverberant and spatial experience and this will interact with mono listening. It's individual what you prefer - I like an exact representation of the music and recorded room, others like to be "in the music".
Nevertheless - the speaker should be able to produce that "pin point" source in the beginning.