I have had some opportunity to isolate and assess room impact (mainly modes) and IMO agreed that it is strong but the strongest impact on audio quality I have observed was combined mid and tweeter IR optimization (a bit general and possibly vague statement, I know 🙂 ).
So room can strongly worsen the quality (in my observation mainly damages the overall resolution & detail and in particular bass articulation, all is quite muddled) but it is even more important to create this quality in the first place 🙂
So room can strongly worsen the quality (in my observation mainly damages the overall resolution & detail and in particular bass articulation, all is quite muddled) but it is even more important to create this quality in the first place 🙂
So the so fer discussion supported me in my plan to give an MTM a chance, I have 3" fullranges already selected but I would greatly appreciate tweeter tips. After studying what is available in more detail i will lower the bar slightly, so anything > 86dB (1W/m) and 4Ohm is OK.
Yeah we need first and foremost agonize over perceived sound in a room. This means figuring out the off-axis response of any system, which as one lump is just the power response. And to be able to make good judgement what kind of off-axis response is needed one should know about psychoacoustics and perhaps know some preference sound to attach to, perhaps optimize some angles over some others and its somewhat frequency dependent as well.
Those who like MTM style speakers probably like it because of less vertical reflections and more horizontal reflections, some where on critical midrange. Coaxial is different, its got roughly as wide vertical as horizontal directivity depending on the enclosure so about as much vertical and horizontal reflections coming in at listening spot.
We gotta remember this mostly affects mid range, above the speaker size wavelength frequencies and below beaming of the treble, or more likely up to few kilohertz above which "comb" happens so tight hearing system averages it out. This could be roughly between say 300Hz - 3kHz or something, make WMTMW with narrow response on this bandwidth and most advantage is reaped. Conversely, reducing vertical reflections past few kiloherz is diminishing returns in this regard ( not knowing all effects it might have on perceived sound, just looking at effect to timbre as in frequency response anomaly ).
Attached simulated response of combfilter similar to what single floor reflection would make with direct sound (ideal sources in vituixCAD, other delayed 50cm in relation, but its irrelevant as the intention is just to demonstrate hearing system would smooth out the tight comb). REW:s psychoacoustic smoothing it smooths out past some kiloHz.
I'm not very educated on this, just what comes out from the hobby by reasoning and reading random bits from here and there. I don't have any MTM speakers, or coaxials, to compare. I liked coaxial and fullrange systems I've had in the past but current prototype trumps them all and its not either, just controlled directivity. As always, its not direct comparison because so much more difference than just the topology but it just means not all point-sources are best, just make problem free speaker system that works with the room and its good no matter what the topology.
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Tmuikku,
Agreed with your first sentence in post 39. I will have opportunity to compare directivity in my room in the next month (i ordered a Kef uniQ recently) with Tannoy 8" 90° @1800hz and up.
Pawelp please do an mtm.
Even if for educational purpose. The issues they have have already been described and link from GM is the main one.
Explanation given by SpeakerDave are worth a listen too imho.
Did someone else noticed Dave Smith described the answer John Dunlavy have choosen with it's own works? Bright minds arriving to same point..
Agreed with your first sentence in post 39. I will have opportunity to compare directivity in my room in the next month (i ordered a Kef uniQ recently) with Tannoy 8" 90° @1800hz and up.
Pawelp please do an mtm.
Even if for educational purpose. The issues they have have already been described and link from GM is the main one.
Explanation given by SpeakerDave are worth a listen too imho.
Did someone else noticed Dave Smith described the answer John Dunlavy have choosen with it's own works? Bright minds arriving to same point..
And why an mtm with 'big' drivers ( 12/15") are interesting as they mitigate this floor/ceiling 1st reflections: rather than a big notch, they create two smaller ones which are less noticable.
This works because wavelength are long enough at fc with these big drivers.
And why i'm less convinced by most smaller drivers mtm i've heard. In this case i would go expanding array as it offer a chance to have more control over a wide range for vertical directivity and give more 'weight' to sound by increasing total sd the lower you go.
The other answer is to use a coax xed over to freq at which the floor bounce happen... three source with different distance, 3 lesser notch,...
One have to remember too mtm have other advantage than their directivity behavior, doubling sd (and power if //drivers) being one of them: bsc compensated by design choice).
I'm mixed feelings with this one as we don't have single reflection in listening spaces but a lot more, roughly 6 strong first early reflections that make the response quite a roller coaster nevertheless and the late reflections fill in. Visual curve might not matter if hearing system is intelligent with the sound, it seems to be quite efficient disregarding the reflections from perceived sound, or at least integrating them to one perceived sound somehow meaning that what we can and probably should do is try and help the brain, give easier time making the filtering, get focus on the music and discard the noise. This might mean we just have to provide very clean comb filter for example without extra dips and peaks, equal frequency response towards specular early reflection angles as direct sound making perfect comb filter.
This is what I mean, and speculate: see the comb filter graph on my previous post basis for this thought experiment, the comb happens at regular interval of 50cm (~700Hz) in this case. If the first or second dip of the comb was reduced due to null (null between lobes at crossover or something) pointing that direction the dip wouldn't cancel out completely but perhaps turn into two narrower dips and the new bottoms would be at different frequencies than all the rest of the combfilter, which happens at regular interval depending on the path length difference. I speculate the brain can process the regular interval effect much more easily out than irregular one. At least with computer programming difference between the two would be immense in terms of lines of code, it is much easier to take out effect of regular patterns than irregular patterns out from data. For lazy programmer it would mean that only the regular data gets fixed but the irregular stays in making coloration.
Mind you I'm not referring to any science as I haven't read such thing, just reasoning over the stuff I'm observing.
This was discussed, or at least mentioned, earlier in the thread few times but I'm not sure if this an argument with small MTM because just using single big coaxial with the same size would have about 3x more Sd. Example, two ~6" drivers fit into space (height) of one ~15" but only have ~33% of Sd, both would have similar vertical directivity but different horizontal directivity. It is when the array gets bigger than 15" when it cannot be substituted with single coaxial anymore. Obviously constrains in aesthetics, or requirements in directivity, that could demand either topology so, can be advantage or disadvantage 😉
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I think i remember SpeakerDave mentioned he used an Audax tweeter which was small enough to fit the requirements ( look for Dave Smith TNT interview in google, or the stereophile reviews of Snell's he designed).
At which freq would you plan to cross?
Something like this @2400hz could fit ( distance ctc between 2x3" + this tweet ~ 0,5wl at 2400hz) :
https://www.toutlehautparleur.com/u...f13-4-ohm-bobine-25-mm-facade-70-x-54-mm.html
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Edit time over. I'm fixated to the directivity and stated the above based on that alone.
Of course you are right if we use two same sized woofers instead of one the Sd is more and there might be reasons why the small woofer was used instead of single big one, like small tweeter to crossover to. There is many variables/things on loudspeakers to optimize and for example using small tweeter without waveguide needs small woofer to accompany for smooth off-axis response, doubling it with another might be good thing to do for some applications. One could also use a waveguide on the tweeter instead and now bigger woofer would be fine with much more Sd and smooth off-axis response but this is again another set of compromises unraveling through out the system.
Whats the most interesting thing to me in loudspeakers is the acoustic output, the off-axis, the power response, which perspective one looks at the system, which is about all that matters because if thinking things in perspective of what is possible we can pretty much solve every other problem: if we assume we can do any crossover (which is pretty much possible), and can buy best drivers there is (can't quite touch ideal drivers but not too far out especially if performance is factored into the system) and the rest is just about manufacturing problems, which we don't have in the age of 3D printing and computer aided manufacturing. All that is left as "problem" is the acoustic output and implications of that to perceived sound in a room and at the core is wildly different wavelength between low and high frequencies and fact we have to control it all to some extent with static physical objects whose size doesn't change with the frequency 😀 and we can't have two objects in same physical place at same time so what compromises matter and what not, in this regard, physical worlds vs. wavelength. Questions that are interesting are like is diffraction important and to what extent? Is lobing important and to what directions? What about main lobe does it need to be wide? Things like that, the acoustic output of the system. When we know what's more important, what kind of vertical directivity for example, is it comfortable to listen to, how much it costs, its not big of a deal to make system based on that. Or it is, but its now possible to do as we know what to actually do to make best system for the situation and application with current technology. Mucho to learn though and first step is to discard marketing fud which has that's been injected to our brains since commercial tv 🙂
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I see where you are heading to. But i must confess i've been involved into all this because i faced an issue with lobe with my mains... and so know i'm sensitive to the issue* they can bring so if i could stay away from it... 😉
Yes there is multiple source of ER and they all contribute, but the most harmfull comes from the lowest dimensions of room and chances are this is the height the culprit.
There is only few answers for this vertical control in wide range ( including low and low mid) and one is from vertical aligned array imho.
* my mains induce(d) waistbending behavior around 800hz as a cross from 15" to 4,5" direct radiators would bring. 'Room's ' sound ( reverb) sound weird as outcome... and the vertical offsets between drivers doesn't help with a stable rendering imho. It's better now i lowered fc but i've lost in output level and induced more or less same issue at tweeter x by upping it...
I assume you are using VituixCAD and have full data: How is your sound power? what about DI and what happened to ERDI? Do you have possibility to lower / raise the whole system or have you experimented with listening distance, toe-in? these would affect at which angle the first specular reflections happen and perhaps help figure out if problem is the overall directivity of the system or directivity to some particular directions. As you seem to describe the problem as reverberation related and not direct sound related I suspect its just the power response that is not smooth, or perhaps some acoustic treatment to lower the reverberation time would help. Very interesting stuff 🙂
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No.
I havent. Did'nt need it. I own these loudspeakers since 1995 and used them in many rooms. I always been bothered by them but their other quality kind of compensated. Until i started to work on them.
I though it was xover related so gone active thinking i could eq the 800hz range. Better to my preference but still that thing that bothered me and eq wasn't successful... That was around 2010. I first measured them outside at that time as i quited city for countryside. Each drivers by themself, then all at once at different angles horizontal.
It was instructive. Made some sim in lspcad too but only theorical behavior of perfect loudspeakers. Identified a pattern, done more sims,...
I've lost interest on improving them. I'm ok with how they are. I don't want to spend more time on compromises i've not made myself. I learned a lot thanks to them. Not only about 'acoustic behavior' of drivers but size of cabs, their effect on diffraction, etc,etc,..
Meanwhile i've got many coax at home and i'm hooked to their rendering. And i like vertically aligned loudspeakers i've heard so why not try both at once?
For that i simulate a bit.
I could simulate them as an exercice but i must tell i'm short on time with 2 kids and an house to renovate. And i'm not sure it would bring me more ( except confirming the soft are trustable).
I havent. Did'nt need it. I own these loudspeakers since 1995 and used them in many rooms. I always been bothered by them but their other quality kind of compensated. Until i started to work on them.
I though it was xover related so gone active thinking i could eq the 800hz range. Better to my preference but still that thing that bothered me and eq wasn't successful... That was around 2010. I first measured them outside at that time as i quited city for countryside. Each drivers by themself, then all at once at different angles horizontal.
It was instructive. Made some sim in lspcad too but only theorical behavior of perfect loudspeakers. Identified a pattern, done more sims,...
I've lost interest on improving them. I'm ok with how they are. I don't want to spend more time on compromises i've not made myself. I learned a lot thanks to them. Not only about 'acoustic behavior' of drivers but size of cabs, their effect on diffraction, etc,etc,..
Meanwhile i've got many coax at home and i'm hooked to their rendering. And i like vertically aligned loudspeakers i've heard so why not try both at once?
For that i simulate a bit.
I could simulate them as an exercice but i must tell i'm short on time with 2 kids and an house to renovate. And i'm not sure it would bring me more ( except confirming the soft are trustable).
Allright! asked because the simulations are relatively easy to do and produce these graphs but without experience it is hard to translate sound to graphs and vice versa. Listening always rules and dictates if something is good or not and it would be very helpful to be able to relate graphs to sound without actually building and listening every variation 😀 I suppose there is no way around currently.
I could ask people what should I build for best sound but everyone knows how helpful that is, all have their own experiences views and opinions, rooms and what not. 😀 no way other than listen to everything and keep on searching and studying as long as its fun and interesting.
I could ask people what should I build for best sound but everyone knows how helpful that is, all have their own experiences views and opinions, rooms and what not. 😀 no way other than listen to everything and keep on searching and studying as long as its fun and interesting.
Yeah thanks, there are multiple similar systems, from KEF for example. Need to finaih current system and when it is time for next one its going to be multiple entry horn 🙂 point-source is the way to go I think as well.
Meh. If i could dream of such a built... maybe one day.
I inquired a customer which is carpenter about cost for an meh. It wasn't cheap but not completly crazy neither. The real issue i see is there is probably some tweaking needed and i'm not sure i could handle that...
I inquired a customer which is carpenter about cost for an meh. It wasn't cheap but not completly crazy neither. The real issue i see is there is probably some tweaking needed and i'm not sure i could handle that...
This is not really an issue i face, my family is used to big ugly box in the living room ( maybe not frightned enough as my youngest son was proud to show me he destroyed the dustcap of a woofer and he didn't touched the tweeter! I should have been clearer in my explanation... don't touch dad's toys! Even on storage...).
From the link; "Audio Physic's Active Cone Damping (ACD) technology. The tweeter is hung in front of the midrange cone using AP's three-point String Suspension Concept (SSC) technology. AP claims that SSC both decouples the tweeter from vibrations induced by the midrange driver, and positions it far enough out front to avoid the typical "cuppy" sound that, in a coaxial driver, can result from the tweeter dome being deep within the confines of the midrange cone."
Wow, I guess I'll call my cork board sandwich "constrained layer panel damping technology" that absorbs vibrations induced by the FR driver and prevents re-radiation of unwelcome musical tones from the panel itself.
I once stuck a tweeter concentric to a linear woofer cone, on a threaded post where I could easily change the relative depth. It measured terribly, until I pushed it way out forward from the pole piece. I didnt want that, so I abandoned the project. Guess I should have stuck with it; no cuppy sound, but no time align, either.