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TMMW Layout
I have been looking at many speaker manufactures sites for inspiration for new designs. I can across an interesting one you don't seen very often the TMMW; There are a lot of TMWW's, some MTMWW's and TMW's and a few TM-MW-W four ways. Is the TMMW layout so uncommon because it doesn't have much to offer over other layouts? One issue I have with any MTM design is the steep order crossover needed for the tweeter and I like the sound of shallower slope crossovers. The dual midranges of the TMMW layout provides more midrange cone area than a single midrange but with better horizontal dispersion - The midrange can cover a wider range of the spectrum spreading the crossovers frequency out further.
Shawn
Totem "Wind Design"
Comments
Seems like the CTC would suffer. I'm sure in a big enough room / listening distance everything would probably combine properly, but in a normal size room, might have issues.
That's a familiar speaker, Totem is well regarded as far as commercial speakers go.
It's an interesting arrangement for sure, generally the woofer is the weak link for overall system sensitivity due to baffle step losses, so doubling up on midrange drivers is generally not required to meet sensitivity requirements. The second driver does "help" in the sense that excursion and power consumption of each driver is cut in half, however for a midrange excursion and power handling aren't generally an issue to begin with. Then you have the potential for a weird vertical polar pattern as the second midrange has significant distance from the tweeter, so the effective centre-to-centre of the drivers is larger than if you just used a single midrange. I can't say for certain why Totem decided to use 2 midrange drivers here, other than the marketability of more drivers is more impressive.
I don't understand your reasoning here. 2 drivers vertically arranged doesn't provide any greater horizontal pattern, nor does it change the frequency spectrum that the drivers can cover. It does provide a narrower vertical pattern, so if anything the spectrum that the drivers can cover is less if you are observing strictly by directivity alone. For a 5" midrange you can assume that the horizontal pattern will be sufficiently wide on the horizontal plane through the midrange frequencies regardless of the number of drivers used.
What I meant by wider spectrum for dual 5” midranges is that a single 5” could do 300-2600, a single 6” can do 200-2000Hz. And two 5” midrange drivers could cover 200-2600Hz which is a wider range. But of course it will depend on actual drivers and baffle step.
You would likely get lower distortion in the critical midrange due to reduced excursion. You would also get narrower vertical dispersion for less floor/ceiling reflections at certain frequencies. Not a bad idea overall...
You might have the 2.5-way xover the mids in that configuration unless you can get the CTC closer and the xover low enough to the tweeter.
For instance on my recent EMP design, I xover'd at 1.8k, and the CTC is 10.375" from lower woofer to tweeter. This distance equates to 1.3k wavelength, and I don't notice any stretching of the image.
In my experience, 500Hz is about as far out from CTC I can go before it starts to stretch it. The closer the better.
Jeff ran his Solstice in a straight 2-way config as well, and the CTC is pretty long there too.
In regards to the Totems, I wonder if it wasn't some sort of averaging the acoustic center of the midbasses to align with the woofer and tweeter in that design.
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Also, it is certainly possible to have an MTM with a shallow sloped crossover. It may not be true to the D'Appolito design but if it sounds good, why not?
I'm of the same opinion here. Just because 3rd order acoustic is the standard does not mean that works best in all cases.
Case in point, my Glucinium Amor MTM design with the TB 25-1743 and W4-1798S woofers have a 12dB electrical slope on them to achieve what appeared to be halfway between a Bessel4 and LR4 acoustic as far as alignments go.
They sound great!
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Not sure why the mid would have to reach low with a single front mounted woofer. I could see needing to get down to 150 to 200 Hz with a side mounted woofer.
I do like multiple small mids for a narrow baffle
Ok, thank makes more sense
Personally, I wouldn't try to operate a midrange driver below the baffle step, that just seems counter-intuitive to me, so 300Hz and up generally. I would also find it hard to justify the extra cost of double the midrange drivers to make up 100Hz difference, if that were the situation I were in I'd probably go with the 6" and get a bit better tweeter if I needed, and still probably come in at a lower cost than two equivalent 5" drivers.
For the Wind speaker above, I'm confident they could have made it work just as well with a single midrange driver.
Does someone actually know the crossover points of each of the divers (Totem spkr)?
Perhaps the top 3 drivers are set-up in a quasi ~ 2 1/2 way, which would minimize issues of the lower mid’s lack of proximity to the tweeter, while limiting the excursion necessary at the lower end of the mid range, and hence attenuating distortion at higher volume/power vs a single 5 in mid ???
I just saw a review: X overs @ 195 and 2.5g, well that is low for the mids
This what I was thinking the 5" 8ohm mids in Parallel would have a 2.83V sensitivity of around 92-94db on an infinite baffle, but with baffle step this would be reduced by 2-3dB. Therefore to matchup closer with tweeter sensitivity you roll of the lower mid driver at a lower frequency which also helps with the CTC issue since the upper midrange driver would produce more of the higher frequencies.
The reason I want a low crossover point between the midrange and the woofer is I just think is sounds better if the midrange produces a very wide range of the spectrum for better coherence. If I could get 5 octaves out of the midrange without sacrificing horizontal dispersion or excessive non linear distortion that would be awesome. Also I would move the woofer closer to the floor vs the Totem design to get more low frequency gain less baffle diffraction loss.
Here is what I'm thinking
Hiquphon OW2 tweeter in a waveguide
2X Satori MR13P-8 in parallel
Wavecor SW223BD02, Powered by an internal amplifier
Internal passive crossover for Mid-LP and Tweeter-HP filters
External Digital crossover for Mid-Tweeter and Woofer
Crossover points 200Hz and 2500Hz