hello,
im designing a 3-way hifi build and was considering an MTMM configuration for mids and highs. however i dont think i have seen this configuration anywhere 😕 is it a bad idea? what problems may arise? when configuring the distance between mids and highs, do i follow MTM guidelines? will vertical lobing be weird? how do i best amp 3 mids, as 3x4ohm in series=12ohm or 3x8ohm in paralell=2.67ohm (was considering hypex/icepower class d amps but cant find any 2.67/12ohm data on them)?
thx for the help, cheers!
im designing a 3-way hifi build and was considering an MTMM configuration for mids and highs. however i dont think i have seen this configuration anywhere 😕 is it a bad idea? what problems may arise? when configuring the distance between mids and highs, do i follow MTM guidelines? will vertical lobing be weird? how do i best amp 3 mids, as 3x4ohm in series=12ohm or 3x8ohm in paralell=2.67ohm (was considering hypex/icepower class d amps but cant find any 2.67/12ohm data on them)?
thx for the help, cheers!
Do you want exceptional sound, OR do you want to use several midbass drivers you already own(this is the only reason to build a MTMM)?
"Back in the Day of passive crossovers" the MT-Mw-Mw topology(Mw=midwoofer with Fs<35Hz) was used to compensate the T-M time arrival difference at-the-Listener. This allows the use of -LR2 / +LR2 crossover circuits to generate a time+phase coherent wave launch arriving at-the-Listener. No deep bass -OR- no exceptional midrange with identical M's.
For HT with "on the couch" listeners, the controlled vertical polar lobe pattern of the MTM topology with +LR2 / -LR2 can be desirable, especially in an apartment. Adding REAL woofers (MTM-WW) to cover the bass can produce exceptional couch potato sound. MTM-WW, where parallel Ms and parallel Ws increase efficiency.
Why not build a REAL 3-way design?
1) TM-WW topology. Proven excellence. 1"T, 6"M, 8"W
--Like the award winning Sony AR1 with two 8" woofers
--Like the Beautiful Avalon Compas with a 3-bevel.cuts truncated pyramid low diffraction cabinet
--Like the award winning KRONOS with bottom side-side woofers for low vibration
2) T-M + side W topology, which allows a narrow front baffle.
--Build a 3cuft sealed 12" SB34NRSX75-6 on the side for fast transient bass with -F3=37Hz.
"Back in the Day of passive crossovers" the MT-Mw-Mw topology(Mw=midwoofer with Fs<35Hz) was used to compensate the T-M time arrival difference at-the-Listener. This allows the use of -LR2 / +LR2 crossover circuits to generate a time+phase coherent wave launch arriving at-the-Listener. No deep bass -OR- no exceptional midrange with identical M's.
For HT with "on the couch" listeners, the controlled vertical polar lobe pattern of the MTM topology with +LR2 / -LR2 can be desirable, especially in an apartment. Adding REAL woofers (MTM-WW) to cover the bass can produce exceptional couch potato sound. MTM-WW, where parallel Ms and parallel Ws increase efficiency.
Why not build a REAL 3-way design?
1) TM-WW topology. Proven excellence. 1"T, 6"M, 8"W
--Like the award winning Sony AR1 with two 8" woofers
--Like the Beautiful Avalon Compas with a 3-bevel.cuts truncated pyramid low diffraction cabinet
--Like the award winning KRONOS with bottom side-side woofers for low vibration
2) T-M + side W topology, which allows a narrow front baffle.
--Build a 3cuft sealed 12" SB34NRSX75-6 on the side for fast transient bass with -F3=37Hz.
thx for the answers, perhaps i was a little vague with my plans. so the idea is to make a large powerful 3-way MTMM/W which can also be used on table as pc speaker system, so the design requirements are the following: slim midtops so they can go left and right of my monitor, cabinet height of 550mm, width of max175mm. i want to go with some higher end drivers and i chose a Mundorf AMT21CM2.1-C as tweeter, SB ACOUSTICS 4” SB12CACS25-4 as midwoofer and Scan Speak 23W/4557T00 as woofer. however 30w and 4" sound a bit disappointing for mids so i was thinking about MTM W or MTMM W, something like this:
with this configuration i would have 2 options for listening height, which correspond exactly to my pc chair/couch. i could simply drop the third midwoofer and go for MTM if that saves me some problems^^
cheers
with this configuration i would have 2 options for listening height, which correspond exactly to my pc chair/couch. i could simply drop the third midwoofer and go for MTM if that saves me some problems^^
cheers
yes, you were vague...
if you make your top MTMM 2.5 way instead of just 2 way, it may be ok
if you make your top MTMM 2.5 way instead of just 2 way, it may be ok
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btw, that dashed line is irrelevant, its the height of the tweeter what matters, line should go there
Some random thoughts.
Choosing 4 Ohm mids, how are you thinking to wire them? Any combination of series/parallel will give an impedance below 3 Ohm, and wiring them all in series won't give you any sensitivity advantage. So I'd drop the concept of 3 mids.
The MTM configuration with parallel wiring is usually done to give you roughly 6dB more output from the mids. You then need to careful choose the tweeter, but you also need to pick an 8 Ohm mid in order to stay safe with the impedance. If you use 4 Ohm drivers you have to wire them in series, so you'll have advantage in lower distortion, but no gain in SPL. In this case you are using 2 smaller drivers instead of a single bigger driver.
Last thought about the chosen woofer. This is a sub will very low SPL optimized to work in a smallish closed enclosure, you need to really boost it, if not you end with a very low sensitivity speaker (padding down mid and tweeter). I don't have experience with this sub, so I don't know how high it can go, but I suspect you'll have problems in integrating it with 4" mid drivers.
Ralf
Choosing 4 Ohm mids, how are you thinking to wire them? Any combination of series/parallel will give an impedance below 3 Ohm, and wiring them all in series won't give you any sensitivity advantage. So I'd drop the concept of 3 mids.
The MTM configuration with parallel wiring is usually done to give you roughly 6dB more output from the mids. You then need to careful choose the tweeter, but you also need to pick an 8 Ohm mid in order to stay safe with the impedance. If you use 4 Ohm drivers you have to wire them in series, so you'll have advantage in lower distortion, but no gain in SPL. In this case you are using 2 smaller drivers instead of a single bigger driver.
Last thought about the chosen woofer. This is a sub will very low SPL optimized to work in a smallish closed enclosure, you need to really boost it, if not you end with a very low sensitivity speaker (padding down mid and tweeter). I don't have experience with this sub, so I don't know how high it can go, but I suspect you'll have problems in integrating it with 4" mid drivers.
Ralf
If you are worried about midrange power handling.
Go for a neo tweeter 6.5" MTM combination. Most 6.5" midrange / midwoofers can handle >= 60w. A pair would easily exceed the power handling needs (thermal) that would be thrown at your woofer(s).
I'd drop the MtMM / MMtM idea. You will have to cascade the extra M (e.g. 2.5 way) to get any power handling benefits at the expense of low impedance and avoid lobing issues.
If you were to make the top section a 3 way to improve impedance, you are creating a thermally limited low frequency bandwidth driver (the "M"MtM) which will reduce overall powerhandling - not increase it (counter to intuition that more drivers increase power handling).
So - I'd recommend for example an MTM (2 way classic) with 6.5" drivers and neo tweeter to reduce CtC spacing.
Something like an SB29RDNC (72mm faceplate) any take your pick of other SBA 6.5" drivers.
Go for a neo tweeter 6.5" MTM combination. Most 6.5" midrange / midwoofers can handle >= 60w. A pair would easily exceed the power handling needs (thermal) that would be thrown at your woofer(s).
I'd drop the MtMM / MMtM idea. You will have to cascade the extra M (e.g. 2.5 way) to get any power handling benefits at the expense of low impedance and avoid lobing issues.
If you were to make the top section a 3 way to improve impedance, you are creating a thermally limited low frequency bandwidth driver (the "M"MtM) which will reduce overall powerhandling - not increase it (counter to intuition that more drivers increase power handling).
So - I'd recommend for example an MTM (2 way classic) with 6.5" drivers and neo tweeter to reduce CtC spacing.
Something like an SB29RDNC (72mm faceplate) any take your pick of other SBA 6.5" drivers.
IDEA: spend your budget on a few higher quality M & T
You should also consider a good quality 6" midbass + 1" dome tweeter 2-way TM build.
(1) sealed for superior transients when a woofer is added
(2) ported for deeper bass when used alone for desktop or HT satellite.
-You can stack the sealed TM on two ported 8" woofers... front-front, or side-side.
-You can stack the sealed TM on one sealed 12" woofer... front or side... for excellent bass transients.
You should also consider a good quality 6" midbass + 1" dome tweeter 2-way TM build.
(1) sealed for superior transients when a woofer is added
(2) ported for deeper bass when used alone for desktop or HT satellite.
-You can stack the sealed TM on two ported 8" woofers... front-front, or side-side.
-You can stack the sealed TM on one sealed 12" woofer... front or side... for excellent bass transients.
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thanks for the input! i now understand why MTMM is silly, however i would like to stick with my narrow baffle if possible, so all those 6" midrange drivers are not really an option.
would an MTM with 4" or 5" mids do the job?
which of these mids would you prefer?
4" SBA SB12CACS25-8
5" SBA SB15CAC30-8
5″ SBA Satori MR13P-8
4" Visaton TI100-8
5" Visaton AL130-8
4" Scan Speak illu 12MU/4731T00
5" Scan Speak illu 15WU/4741T00
4" or 5" other
cheers
would an MTM with 4" or 5" mids do the job?
which of these mids would you prefer?
4" SBA SB12CACS25-8
5" SBA SB15CAC30-8
5″ SBA Satori MR13P-8
4" Visaton TI100-8
5" Visaton AL130-8
4" Scan Speak illu 12MU/4731T00
5" Scan Speak illu 15WU/4741T00
4" or 5" other
cheers
Maybe 4x 4", 4ohm drivers would fit better than three?
I once built an MTM with 4" paper drivers, it was worth remembering for how it sounded. There was enough output for a desktop speaker, not so much to sit back from in a larger room and turn it up. 4 of them ought to give you some space to tune the bass a little.
I once built an MTM with 4" paper drivers, it was worth remembering for how it sounded. There was enough output for a desktop speaker, not so much to sit back from in a larger room and turn it up. 4 of them ought to give you some space to tune the bass a little.
You have quite a price range in those drivers you have mentioned. What is your budget?
I like the CAC series of drivers from SBA, I like them a lot.
As LineSource said, why not try a 6" mid with 1" dome?... it is the easiest, most risk free approach to getting a good sounding speaker. If you want to add a sub later, it is very easy to do so...
In fact, if you have a great sounding 6+1 MT monitor, and you add a pair of small active subs (like 10 inch) using MiniDSP, you can achieve a very high quality full-range sound system.
ok,
i went back to the drawing board considering all your input...
i know i can build a decent speaker if i just copy a well known design, however this project is about experimenting and fun for me, so i might make some weird choices anyway :F i am willing to trash the cabinets and try again if it sounds or measures terrible...
Tweeters: I know many of you suggested to use a 1" dome... too late 😀 i just got a sick deal on a pair of mundorf 23CM1.1-R, too good to pass, so the tweeter choice is final.
Midranges: I heard so many positive things about the SBA CAC series, i think i will stick with those for this project... ill use 2 6" - 8ohm in paralell MTM config, baffle width increased to 230mm
woofers: 2x 8" SBA CAC woofer in vented 80l enclosure
i wanna keep it modular, so something like this maybe:
so i think i might build this monstrosity in 3 levels
lvl1: 2 midtops
lvl2: +2 woofers
lvl3: +2 woofers +subextension?
since i have to fill the empty space behind the midtop for the monster stack i might as well use those 35l for a 20-50hz sub extension...
can this be done? winisd suggest a 4th order bandpass with this size as 3.5way might do the trick.
how bad are my ideas?
cheers, lisette
i went back to the drawing board considering all your input...
i know i can build a decent speaker if i just copy a well known design, however this project is about experimenting and fun for me, so i might make some weird choices anyway :F i am willing to trash the cabinets and try again if it sounds or measures terrible...
Tweeters: I know many of you suggested to use a 1" dome... too late 😀 i just got a sick deal on a pair of mundorf 23CM1.1-R, too good to pass, so the tweeter choice is final.
Midranges: I heard so many positive things about the SBA CAC series, i think i will stick with those for this project... ill use 2 6" - 8ohm in paralell MTM config, baffle width increased to 230mm
woofers: 2x 8" SBA CAC woofer in vented 80l enclosure
i wanna keep it modular, so something like this maybe:
so i think i might build this monstrosity in 3 levels
lvl1: 2 midtops
lvl2: +2 woofers
lvl3: +2 woofers +subextension?
since i have to fill the empty space behind the midtop for the monster stack i might as well use those 35l for a 20-50hz sub extension...
can this be done? winisd suggest a 4th order bandpass with this size as 3.5way might do the trick.
how bad are my ideas?
cheers, lisette
Your general plan sounds good, however considering your final choice for the tweeter, I think you should opt for a (max) 5" for the mid. The 6" driver starts to beam long before your tweeter can be safely crossed over, so you'll end either with a strained tweeter, or with a mismatched dispersion between mid and tweeter (poor power response).
Ralf
Ralf
I have been considering something similar, but with 6" SB17MFC35-8s (or maybe CAC/NBAC). If going with these wider mids, would it be possible to use a waveguide with SB29RDNC to match dispersion, or rather use something like Fountek NEO CD 3.5H?
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You shouldn't post this question in this (active) thread...
But shortly, in the Fountek datasheet I read "Recommended crossover 2,500Hz with 3-order" so I would limit its usability with a 5" mid. OTOH a robust tweeter on a waveguide is a good match for a 6", but I'd use the SB29RDC instead.
Ralf
But shortly, in the Fountek datasheet I read "Recommended crossover 2,500Hz with 3-order" so I would limit its usability with a 5" mid. OTOH a robust tweeter on a waveguide is a good match for a 6", but I'd use the SB29RDC instead.
Ralf
The Mundorf 23CM1.1-R Tweeter is a poor choice for the MTM topology because the datasheet shows that a crossover frequency of at least 2kHz is necessary for flat SPL response and modest driver effects from the resonance = 1700Hz. Many 1" dome tweeters have a resonance under 800Hz. A 2kHz wavelength is 6.8", which becomes the maximum center-to-center separation between the two midrange drivers in a properly designed MTM configuration. This 2kHz MTM with 6" midranges will have a comb filter polar pattern.
The Mundorf 23CM1.1-R gets good reviews for excellent transient response and outstanding low distortion when properly used. Run simulations which cover the polar response for Mundorf 23CM1.1-R Tweeter with a 2kHz crossover (BW3 or LR4) to a single 6" SATORI MR16P-4, which has ~92db sensitivity ... which drops to around 90db after the crossover, which is close to the 23CM1.1-R SPL.
Two 8" SB23NBAC45-8 woofers with 87db SPL connected in parallel will have similar ~90db SPL after some baffle step compensation.
If you want to use tube amplifiers, you can use the 8-ohm version of the 6" SATORI MR16P-8, and wire two 4-ohm SB23NBAC45-4 woofers in series.
Worth some consideration and discussion.
The Mundorf 23CM1.1-R gets good reviews for excellent transient response and outstanding low distortion when properly used. Run simulations which cover the polar response for Mundorf 23CM1.1-R Tweeter with a 2kHz crossover (BW3 or LR4) to a single 6" SATORI MR16P-4, which has ~92db sensitivity ... which drops to around 90db after the crossover, which is close to the 23CM1.1-R SPL.
Two 8" SB23NBAC45-8 woofers with 87db SPL connected in parallel will have similar ~90db SPL after some baffle step compensation.
If you want to use tube amplifiers, you can use the 8-ohm version of the 6" SATORI MR16P-8, and wire two 4-ohm SB23NBAC45-4 woofers in series.
Worth some consideration and discussion.
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as i understood mr d'appolito the one wavelength rule applies between top and woofer in an mtm and that lobing can be controlled through certain crossover topologies, like shown in this pic...
the mundorfs are already in my posession, so i think ill make 2 or 3 dummy baffles, 1 MTM, 1TMM, 1TM and see if i like the sound and how it measures... (i also have a minidsp hd to experiment with different crossovers...) if everything fails ill just sell the tweeters and go back to the drawing board.
thx 4 the help, cheers