I see a lot of DIY 2-way speaker designs are MTM for the added benefit of more output, but remaining a simple crossover. However, most B&M speakers are TMM. Why is that, for both cases?
Is there any particular reasons DIY kits tend to be MTM over TMM? Is there any reason why retail speakers don't use MTM?
I personally rather like the look of the traditional tweet-mid-mid.
Thanks,
Robert
Is there any particular reasons DIY kits tend to be MTM over TMM? Is there any reason why retail speakers don't use MTM?
I personally rather like the look of the traditional tweet-mid-mid.
Thanks,
Robert
Narrow Sweet Spot
One main reason might be because of the narrow sweet spot created by the MTM design. B&W might not be using it because of this, and also because their units, I believe, are 2 1/2 way designs; were the one woofer/midbass is used for low to high frequencies, while the other woofer/midbass is just re-enforcing the low end. The D'Appolito configuration is great if you don't mind sitting directly in the center of a very very narrow sweet spot (Ie. this is a very two channel style).
Personally I have built a few D'appolito designs and find them only marginally better than a well built TM design. The extra +3db effieciency of an added woofer/midbass can be offset by a better choice in drivers and crossover design. Besides... the added complication of having to design an adequate two way passive crossover (if there is such a thing) is just too frustrating; especially when working with already inefficient drivers.
Regards,
One main reason might be because of the narrow sweet spot created by the MTM design. B&W might not be using it because of this, and also because their units, I believe, are 2 1/2 way designs; were the one woofer/midbass is used for low to high frequencies, while the other woofer/midbass is just re-enforcing the low end. The D'Appolito configuration is great if you don't mind sitting directly in the center of a very very narrow sweet spot (Ie. this is a very two channel style).
Personally I have built a few D'appolito designs and find them only marginally better than a well built TM design. The extra +3db effieciency of an added woofer/midbass can be offset by a better choice in drivers and crossover design. Besides... the added complication of having to design an adequate two way passive crossover (if there is such a thing) is just too frustrating; especially when working with already inefficient drivers.
Regards,
Oh yes, I'm aware it's the "D'Appolito" design. I'm also aware of the narrow sweet spot of the design, which makes me wonder why it's so popular with DIY. I personally have no desire to build one, and am quite surprised with all the incredible knowledge of people on this forum that it still remains so popular. I have a hard time finding T-M-M kits.
As you can tell, I am not a fan of its peculiarities. So I was hoping to hear someone defend it.
Inefficiencies in T-M design speakers can be fixed by simply a more powerful amp, which is what I do. I love traditional, simple 2-way tweet-mid designs. 😀
-Robert
As you can tell, I am not a fan of its peculiarities. So I was hoping to hear someone defend it.
Inefficiencies in T-M design speakers can be fixed by simply a more powerful amp, which is what I do. I love traditional, simple 2-way tweet-mid designs. 😀
-Robert
I'm curious to know why both of you think that an MTM creates a narrower sweet spot than say an TM design.
Thanks,
Brendon
Thanks,
Brendon
I'm curious also. The sweet spot of an MTM is far wider than any other design other than a line array. The only advantage to a TMM alignment is when the tweeter is mounted off the baffle in a separate small sub-enclosure, which is beneficial in limiting diffraction.
The reason so many DIY speakers are MTMs is that people going to the trouble of DIY tend to do a lot more research on the subject than those who simply go to a store and buy a speaker. and therefore are more likely to understand why the MTM alignment is generally superior.
The reason so many DIY speakers are MTMs is that people going to the trouble of DIY tend to do a lot more research on the subject than those who simply go to a store and buy a speaker. and therefore are more likely to understand why the MTM alignment is generally superior.
MTM sweet spot
An MTM sweet spot cannot be, by its own theory, vertically wider than most other speaker array configurations. The purpose of the configuration in general is to limit the reflections on a vertical scale of the tweeter. In smaller room configurations with tighter dimensions and lower ceilings, the tweeter reflections can be horrible as the time delay of relfections is much lessened. As such a D'appolito configuration basically 'fences' in the vertical dispersion of the tweeter, narrowing its focus and giving a very tight and well defined image. Its phase response, if the distance set between the tweeter and woofer/midbasses is properly aligned with the crossover frequency, is also greatly improved. The horiziontal dispersion in an MTM design is not affected however (unless of course you flank the tweeter on all sides by woofer/midbasses (an interesting idea... to the drawing board!)) and this gives it a very beautiful sweet spot generally more free of ceiling and floor reflections in the high end (which of course results in generally 'cleaner', 'tighter' sound).
All in all, a great design. If you elevate or lower you head when listening to this type of system however, not so good. This essentially makes it very placement sensitive (not a bad thing, you just have to be aware of it)
To those who have a VERY good understanding of MTM D'Appolito configuration please note: The above is a VERY general outline of D'Appolito configurations.
I personally would defend D'Appolito configurations quite rigourously Valnar, but I would make anyone interested in them WELL aware of their 'excentricities'
Regards,
An MTM sweet spot cannot be, by its own theory, vertically wider than most other speaker array configurations. The purpose of the configuration in general is to limit the reflections on a vertical scale of the tweeter. In smaller room configurations with tighter dimensions and lower ceilings, the tweeter reflections can be horrible as the time delay of relfections is much lessened. As such a D'appolito configuration basically 'fences' in the vertical dispersion of the tweeter, narrowing its focus and giving a very tight and well defined image. Its phase response, if the distance set between the tweeter and woofer/midbasses is properly aligned with the crossover frequency, is also greatly improved. The horiziontal dispersion in an MTM design is not affected however (unless of course you flank the tweeter on all sides by woofer/midbasses (an interesting idea... to the drawing board!)) and this gives it a very beautiful sweet spot generally more free of ceiling and floor reflections in the high end (which of course results in generally 'cleaner', 'tighter' sound).
All in all, a great design. If you elevate or lower you head when listening to this type of system however, not so good. This essentially makes it very placement sensitive (not a bad thing, you just have to be aware of it)
To those who have a VERY good understanding of MTM D'Appolito configuration please note: The above is a VERY general outline of D'Appolito configurations.
I personally would defend D'Appolito configurations quite rigourously Valnar, but I would make anyone interested in them WELL aware of their 'excentricities'
Regards,
Ansuz, could you guide me to some good d'A speaker setup theory in the net? My googling got me nowhere apart from knowing that d'A == MTM which in particular is rubbish...
I'm especially interested in the relation between T-M distance and crossover freq.
I'm especially interested in the relation between T-M distance and crossover freq.
Thanks Ansuz. That helps a lot with my understanding.
So it does not affect the horizontal off axis dispersion? ie. Multiple people sitting on a couch?
-Robert
So it does not affect the horizontal off axis dispersion? ie. Multiple people sitting on a couch?
-Robert
No, an MTM design should have roughly the same horizontal dispersion as a TMM or TM design (given the same drivers, crossover frequencies, and baffle widths).
An MTM has a more restricted vertical dispersion, which is a good thing in most cases. Further, it has a symmetric dispersion pattern, with good phase and amplitude summation attributes when the tweeter is at ear level (something difficult to achieve with TMM or TM designs, but not impossible given a talented designer).
I think their popularity for DIY types is because it is much easier to maximize the potential performance of an MTM design. Maximizing the performance of a TM or TMM (or other...) design might involve quite a bit more research, trial and error, modeling, etc.
I think the popularity for B&M models is mostly due to the height of the speaker. As mentioned, MTM's are designed for the tweeter to be at ear level. The same is generally true for TM, TMM, and other designs as well, though it is possible to tweak designs other than MTM to sound their best with the tweeter a given distance above or below ear level. For this reason, designs with the tweeter on top and all other drivers below can be shorter in height than MTM's, which require another driver above the tweeter (above ear level). I'd guess that most people don't like towering speakers, whether floor stander or on stands, so prefer a bit shorter of a design.
An MTM has a more restricted vertical dispersion, which is a good thing in most cases. Further, it has a symmetric dispersion pattern, with good phase and amplitude summation attributes when the tweeter is at ear level (something difficult to achieve with TMM or TM designs, but not impossible given a talented designer).
I think their popularity for DIY types is because it is much easier to maximize the potential performance of an MTM design. Maximizing the performance of a TM or TMM (or other...) design might involve quite a bit more research, trial and error, modeling, etc.
I think the popularity for B&M models is mostly due to the height of the speaker. As mentioned, MTM's are designed for the tweeter to be at ear level. The same is generally true for TM, TMM, and other designs as well, though it is possible to tweak designs other than MTM to sound their best with the tweeter a given distance above or below ear level. For this reason, designs with the tweeter on top and all other drivers below can be shorter in height than MTM's, which require another driver above the tweeter (above ear level). I'd guess that most people don't like towering speakers, whether floor stander or on stands, so prefer a bit shorter of a design.
disadvantages of MTM that I have noticed is that the BSC ckt operates on both midbass drivers. i find that large inductors (even air core 12AWG/14SWG) damp the sound. with WMT (2.5way) only the woofer (not the midbass) sees the large inductor.
also with WMT theone can go push-push.
The sweet spot of an MTM can be made wider if one palys wiht the crossover. I have done this using 2 x 8546 and 1x9900. however this takes a lot of time and patience and one intallation's cross over will not work in another.
also with WMT theone can go push-push.
The sweet spot of an MTM can be made wider if one palys wiht the crossover. I have done this using 2 x 8546 and 1x9900. however this takes a lot of time and patience and one intallation's cross over will not work in another.
navin said:
Hi Navin,
I assume that you're talking about the vertical dispersion. I think can be confusing for members that aren't as understanding of these topics to refer to it as the sweet spot. In my opinion, the sweet spot is more of an issue of where, horizontally, you hear stereo the best while listening vertically on the design axis (my assumption). Just confirming if this was your point...
Speaker directivity is a sensitive topic, but I just had issues with the original discussion talking about a sweet spot so generally and that 'this' is better than 'that'. I don't think dispersion and sweet spots are the same thing. Dispersion should be viewed as a design criterion. I think Ansuz clarified dispersion from the earlier posts well, but it still doesn't address what's 'good dispersion' .
This is why I don't like blanket statements, which was the start of this thread. My point here is that it's all a compromise, but one that needs to be understood.
Brendon 🙂
Sweet spots
My definition of the sweet spot is the area the soundquality is at its best. This can be horizontally, verticaly and in the listening distance as well, although this is usually less important. To create the largest sweet spot the speaker must radiate the different frequencies as uniform and phase coherent as possible. A balance of the off axis sound is very important (frequency wize) Amplitude falloff is less important (unless you want more people in your sweet spot). Sound bouncing off of walls, floor and cieling will deteriorate the quality of the sweet spot, not necesarely make the sweet spot smaller. Achieving a perfect point source (or line source) speaker is the goal here. I think MTMs behave well because off axis sound vertically is symetrical. Floor and cieling reflections can be pretty large and MTMs deal with this differently.
Coolin
My definition of the sweet spot is the area the soundquality is at its best. This can be horizontally, verticaly and in the listening distance as well, although this is usually less important. To create the largest sweet spot the speaker must radiate the different frequencies as uniform and phase coherent as possible. A balance of the off axis sound is very important (frequency wize) Amplitude falloff is less important (unless you want more people in your sweet spot). Sound bouncing off of walls, floor and cieling will deteriorate the quality of the sweet spot, not necesarely make the sweet spot smaller. Achieving a perfect point source (or line source) speaker is the goal here. I think MTMs behave well because off axis sound vertically is symetrical. Floor and cieling reflections can be pretty large and MTMs deal with this differently.
Coolin
Does MTM perform better than TM?
Hi,
Does it mean other things being equal, an MTM will always perform better than TM?
Thanks in advance,
Goldy
Hi,
Does it mean other things being equal, an MTM will always perform better than TM?
Thanks in advance,
Goldy
Re: Does MTM perform better than TM?
To be fair, we should compare MTM to TMM[2.5] (or TMW), not TM, right?
goldyrathore said:
To be fair, we should compare MTM to TMM[2.5] (or TMW), not TM, right?
I made my first d'Appolito before it had a name. I have gone back to the TMM when I need the power handling of an extra mid but I try and avoid using more than one driver for any portion of the FR as one driver will always sound better than two and because I find the small sweet spot annoying. I would say the TM is always your best choice.
One thing that's not been mentioned is the amount of BSC. A MTM is just like a MT when it comes to handling BSC and it can be altered to whatever level you wish. A TMM (2.5) by its very nature fully compensates for BS which might be a disadvantage in some rooms.
Why are so many center speakers configured as a MTM on their side?
Is this looks or is there a tech reason.
While we're at it can a MT be used well on its side?
Is this looks or is there a tech reason.
While we're at it can a MT be used well on its side?
1. Because they fit on shelves better. Many aren't interested in how they sound.
2. Yes an MT is just fine on it's side.
2. Yes an MT is just fine on it's side.
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