Has anyone seen an MTM arrangement in the kicks? Im thinking two 4" mids and a tweet mounted inifnite baffle... would probably take some serious work to get the crossovers and baffle right.. even if it wouldnt end up with a sonic advantage, the wow factor would be up there I think any thoughts? mike http://mstamm.imgaming.com
Never seen an MTM alignment in car. Geolemon ran a line array in his Nissan truck and ran it TMMT. He said the dispertion charachteristics with the dual tweets worked better that way. Here is Chris' line array project. Notice the tweeters surrounding the mids. I can understand how it allowed for greater dispertion compared to an MTTM alignment. I might be a bit concerned about the MTM in door. If you are planning a kick, with a totally on axis install it may work well, but I suspect a very flat, maybe too flat stage. The characteristics of an MTM alignment are better suited for Home Theater. Bear in mind in HT apps, the ideal location for the tweet is right in line with the TV, or right at eye level of the viewer. The compression of the soundwave can obviously be understandable in this scenario. I would certainly be interested in seeing this done in car, but the closest I know of is Geo's line array.
By the way, my concern with the MTM arsies with directionality issues. I forsee setting a good stage hieght as being nearly impossible. Tweeter location may be hard to hide. I suspect directionality (is that a word?) issues.
And the pure SPACE that it took! You can see, with 5.25" drivers, it took up the whole door... Of course, those were some pretty large-format tweeters I used there (yes, they were 4 ohm! B) ) It wouldn't be too bad with a 4" mid and "normal" neo tweet, I'm sure.. but still, give it a little measurement, see where you are at! It sounds like an interesting comparison.. but it would be really fun to separate the airspace between the two 4" mids, and do an A/B comparison... MTM... compared to MT (shut the lower mid off)... compared to TM (shut the upper mid off)... And see what you end up with! B)
Tweeter location will DEFINITELY be limited.. you're stuck to - surprise surprise - between the mids! It may work out.. give it a shot. I tried TMMT first, with my array.. Then MTTM, and that was noticably worse in terms of imaging. I then tried an arrangement with the mids mounted where they were in the TMMT arrangement, with the tweeters both located phase-correct with each other, but forward of the mids - theoretically better... longer pathlengths. But that sounded worse too. So, I went back to the TMMT. The 5.25's that I used, rightfully ruled... You'd have loved the midbass and impact from four 5.25's in the doors, honestly. But 4's might be more limited... might be really nice to have four 4's in there, in terms of speaker capability. If you are using a very efficient tweet (you'll probably want to), you might even find it to be well matched!
my plan was as follows: with two woofers in each door covering ~60-500Hz, to make sure extension is not a factor for the kicks. I think (by the time i finally get around to it) geo's idea of trying the MTM - TM - MT setup is pretty slick, might try to find a few "cheap 4's" and some tweets to play around with first. thought of doing a boxless, baffle-only design, but depending on the carpet material that might not turn out due to reflections... its just the novelty factor that gets me. as you seem to confirm, there's not too many of these installs around mike
Read my page close, if you get a chance... Like I describe on there, the reason that the speakers were arranged the way that they were, was to ensure phase-correctness, common arrival times... Essentially, all speakers in that "line" had the same pathlength distance to your ear... And in a home-audio MTM cabinet, you have that same effect. In fact, with a line array (if you can get that full advantage with a near-field application), there's only a 3dB loss per doubling of distance, compared to a 6dB loss per doubling of distance, along the direct sound path... This, I theorized, might yield some benefits as well, as especially in-car, you want the direct sound to be prevelant, over the too-many reflections in a car. Also, consider your offset seating position... If the sound is only dropping 3dB per doubling of distance, compared to 6dB per doubling of distance for a typical point-source type speaker install, that effectively acoustically has a balancing effect, making you seem less offset in the car. These were the reasons behind the line-array install... It wasn't just a "TMMT" or "MTTM" thing to try out. Just something to give some thought to, before you build. B)
hey geo, isn't the reduced rolloff with distance the advantage inherent to the line array? Reduced rolloff="apparent increased directionality" in HT, whereas in-car the advantage may be (as you theorized) a decrease in the offset-position effect... no? i never thought about the second issue, but it's a great point you make... how far is the typical -3dB distance, if the reference signal is infinitely close to the source? this would be important, as if the -3dB point is, say, past your ears, the effect wouldn't be very pronounced... just a thought. by the way, in your line array, practice sort of proved that your ears are more sensitive to phase anomalies in whatever frequencies your midranges were playing, right? I.e. you thought the TMMT a better configuration, and since the midranges are in the more ideal line array positions there, maybe tweeter position isn't as inportant? ... so the kickpod configuration i proposed above should yield (theoretically) decent results, seeing as both the Mid and Tweet lines are fairly close to ideal on their respective sides...? mike ps: this is sort of what i had in mind with doors / kicks (not as "fancy" ):
For other views on line arrays in a car setting.... http://www.carsound.com/UBB/ultimatebb.php...ic;f=1;t=022431 http://www.carsound.com/UBB/ultimatebb.php...ic;f=1;t=022435
madstamm, Those don't look like line arrays, rather the door pod and kick appear ported, with a chrome ring. Are you sure they are line arrays? Again, I reiterate the MTM seem to me to make pinpointing tweeter location very easy. Not a desireable trait IMHO. (Ask anyone who has been in my car, they are usually looking for my tweeters in my dash ).
hehehe sorry for the confusion... the pic was supposed to show **a rough approximation** of what i want my front stage like, two woofers in each door, mids and tweets in the kicks. Failed to make tha clear, sorry.. :stupid: aight, this post used to be half a page, but i just educated myself: line arrays turns out all the issues raised can be explained from reading this paper. specifically, the advantages of the line array are contained within the nearfield. On page 8, Figure 5, the minimum line height is adressed, showing that for a typical kick-to-head (pun intended ) distance of ~1.2m, and a crossover freqency of say 2kHz, we need a tweet-tweet distance of more than 0.5m. I have no such space in my kicks. This **might** explain why chris' TMMT config worked better for him, as the MTTM config might have his head in the far field already. Also, to eliminate some other nasty effects like comb line filtering (see page 5, table 1), i'd need a few more tweeters. looks like this idea died. on another POSITIVE note, MrWiggins dropped a hint of a NASTY 2" XBL2 driver with a 4mm one-way excursion... me thinks my kickpods will be hosting a pair of these!! 2" XBL2 driver!! :jawdrop:
