Hi everyone. I need some advice. If I were to build a 3way MTMWW or MTMW what would be the tradeoffs of using 6.5" or 5.25" as the mid?
This speaker will be used for 2ch music and HT, sometimes at higher volumes, thus the multiple drivers. I've been reading some of Dr. Floyd O'tool's (sp?) findings concerning power response and it's effect on SQ, and some of the drawbacks concerning the MTM layout and it's off axis lobing around the wavelength between the mids' acoustic centers. Smooth power response and minimal cancellation between mids will be a design goal with these. Given that, I decided to use 5.25" for better HF off axis dispersion and the ability to have closer acoustical centers, minimizing off axis lobing.
So what am I losing by going this route? Low distortion even at higher volumes is important to me. Obviously the 6.5" would keep distortion lower at any given SPL. I assume power compression would be lessened at any given SPL with the larger woofer. So what else should I consider?
This speaker will be used for 2ch music and HT, sometimes at higher volumes, thus the multiple drivers. I've been reading some of Dr. Floyd O'tool's (sp?) findings concerning power response and it's effect on SQ, and some of the drawbacks concerning the MTM layout and it's off axis lobing around the wavelength between the mids' acoustic centers. Smooth power response and minimal cancellation between mids will be a design goal with these. Given that, I decided to use 5.25" for better HF off axis dispersion and the ability to have closer acoustical centers, minimizing off axis lobing.
So what am I losing by going this route? Low distortion even at higher volumes is important to me. Obviously the 6.5" would keep distortion lower at any given SPL. I assume power compression would be lessened at any given SPL with the larger woofer. So what else should I consider?
Hi,
MTM 3 ways don't make any sense to me at all.
2 ways do, but for 3 ways why have two mid drivers ?
🙂/sreten.
MTM 3 ways don't make any sense to me at all.
2 ways do, but for 3 ways why have two mid drivers ?
🙂/sreten.
Sreten...could you clarify that? It looks like he may be using a woofer for the low end, making it a three way. If one were to use a larger driver for say...under 100Hz, then why not do an MTM with an additional woofer? Efficiency might be an issue depending on the drivers, but couldn't that be offset by multi-amping...or attenuating the mids (if you had to)?
croat47 said:
Hi,
MTM(+nxW) versus TM(+nxW), two mids does not make sense to me.
One high quality midrange is the way to go.
🙂/sreten.
I understand that it does not float your boat: why? Is it cost? the MTM lobe pattern? Efficiency mismatches? Aesthetics?
Why not build MTMW where the W was below 100Hz or so? The MTM may be used because the designer/listener wanted the response of an MTM with some low end support but did not want multiple enclosures?
You have helped me before with technical help, but this seems to be more of an opinion than a technical arguement. I am curious from a technical standpoint.
Why not build MTMW where the W was below 100Hz or so? The MTM may be used because the designer/listener wanted the response of an MTM with some low end support but did not want multiple enclosures?
You have helped me before with technical help, but this seems to be more of an opinion than a technical arguement. I am curious from a technical standpoint.
It's a semantics problem? I've been asking the technical basis of your opinion because I like the idea of the original post. All you've provided is further opinion based on your working definition.
If I were to talk about an MT setup with separate subs...that would be a 2-way plus subs. It's still a 2-way if I make the MT and integrate stereo subs into the same unit as the MT? Am I wrong when I say "3-way" to indicate that all three driver types are in the same unit?
What is the definition of a 2-way? a 3-way? Would the W have to come in at 250Hz to be a 3-way? In the end, why don't we just call everything 1-ways, plus T and/or plus W? Don't "full range" 3-ways go below 100Hz?
If I were to talk about an MT setup with separate subs...that would be a 2-way plus subs. It's still a 2-way if I make the MT and integrate stereo subs into the same unit as the MT? Am I wrong when I say "3-way" to indicate that all three driver types are in the same unit?
What is the definition of a 2-way? a 3-way? Would the W have to come in at 250Hz to be a 3-way? In the end, why don't we just call everything 1-ways, plus T and/or plus W? Don't "full range" 3-ways go below 100Hz?
An MTM -- unless using quite small drivers) forces the XO to the tweeter to be lower than i find optimal....
dave
dave
How small is "quite small"?
I have seen other debates about MTM's, so I will not delve too deeply.
I have seen other debates about MTM's, so I will not delve too deeply.
planet10 said:
Dave , if you have the tweeter positioned at ear level, and are listening to music rather than jumping all over the room, then lobing and combing isn't an issue, and the x-o is not forced to be low.
For music listening I really like the MTM with a first order series, so regardless of theoretical issues you can cross higher than normal dictates.
Others have heard this style of speaker, read reply #16 on this link.
http://www.audiocircle.com/circles/index.php?topic=29980.10
Ignoring for a moment, the above digressions: your original question regarding the tradeoffs between a 6.5 (I’ll say 16 – 18 cm – O.D. of the flange) and a 5.25 (I’ll say 13 – 16 cm) for the mids for an MTMWW (or W) 3-way is actually a bigger question than that of selecting the mids alone.
As your intention is to get high loudness with low distortion in a Hi-Fi and HT set up: Your selection of mids will force certain requirements for the W and T as well. You may want to read Dr. Joe D’Appolito’s original papers on his MTM layout. Some important considerations include fairly hard to fulfill geometric and performance parameters in the drivers. With all due respect, sitting still or jumping about, lobing is always an issue if your room is anything other than an anechoic chamber and you are not locking your head in a Neurosurgeon's Stereotactic frame.
One key consideration: the crossover frequency to the tweeter should be low enough that the interdriver spacing between the two Mids (centre to centre) doesn’t exceed about 1 wavelength at the nominal crossover frequency – this will help ensure a symmetric and consistent power response. You can have more spacing if you don’t mind having a much more complex lobing behaviour – and the resultant poorer sound. As the speed of sound in Denver is approximately 2% slower than at sea level at room temperature and 50% humidity (approx. 334 vs. 341 m/s), the wavelength is about 16.7 cm at 2000 Hz. For where I am, it is 17 cm. This means that for good integration of the two mids and minimal comb filtering, 6 inch mids would have to almost touch if they were to be crossed over at 2000 Hz. If you crossed to a tweeter at 1500 Hz, then you can space about 22.2 cm and there would be space for a small tweeter. So there is a trade-off between a good power response and a crossover frequency that makes great demands on the tweeter. This obviously seriously limits which tweeters can work well in an MTM. On the other hand, at such a low crossover frequency, you need not worry about mid beaming. Of course 5s would allow some more space for a tweeter, and a more easy to accommodate crossover frequency. Even so, at 2000 Hz, a tweeter to play loudly would need to be crossed over using a rather steep slope and still be capable of significant (for a tweeter) linear excursion. Otherwise, you are likely to encounter high dynamic compression and high distortion, not to mention the real potential for killing tweeters.
At the other end, distortion rises as the mid is asked to play louder and lower. So, if you set the crossover high enough to the mid to restrict excursion, then you would also be minimizing distortion. The idea is to keep the excursion within the flat parts of the BL curve and the flatter parts of the suspension deflection curve. This would require a rather steep high pass for the mid or a higher crossover frequency. I guess if you used 6s (50% greater Sd) this would be less of a consideration – most of your challenge would be at the tweeter and its crossover.
But, all things considered, a well executed MTM (+ W or WW) is still hard to beat for overall performance.
As your intention is to get high loudness with low distortion in a Hi-Fi and HT set up: Your selection of mids will force certain requirements for the W and T as well. You may want to read Dr. Joe D’Appolito’s original papers on his MTM layout. Some important considerations include fairly hard to fulfill geometric and performance parameters in the drivers. With all due respect, sitting still or jumping about, lobing is always an issue if your room is anything other than an anechoic chamber and you are not locking your head in a Neurosurgeon's Stereotactic frame.
One key consideration: the crossover frequency to the tweeter should be low enough that the interdriver spacing between the two Mids (centre to centre) doesn’t exceed about 1 wavelength at the nominal crossover frequency – this will help ensure a symmetric and consistent power response. You can have more spacing if you don’t mind having a much more complex lobing behaviour – and the resultant poorer sound. As the speed of sound in Denver is approximately 2% slower than at sea level at room temperature and 50% humidity (approx. 334 vs. 341 m/s), the wavelength is about 16.7 cm at 2000 Hz. For where I am, it is 17 cm. This means that for good integration of the two mids and minimal comb filtering, 6 inch mids would have to almost touch if they were to be crossed over at 2000 Hz. If you crossed to a tweeter at 1500 Hz, then you can space about 22.2 cm and there would be space for a small tweeter. So there is a trade-off between a good power response and a crossover frequency that makes great demands on the tweeter. This obviously seriously limits which tweeters can work well in an MTM. On the other hand, at such a low crossover frequency, you need not worry about mid beaming. Of course 5s would allow some more space for a tweeter, and a more easy to accommodate crossover frequency. Even so, at 2000 Hz, a tweeter to play loudly would need to be crossed over using a rather steep slope and still be capable of significant (for a tweeter) linear excursion. Otherwise, you are likely to encounter high dynamic compression and high distortion, not to mention the real potential for killing tweeters.
At the other end, distortion rises as the mid is asked to play louder and lower. So, if you set the crossover high enough to the mid to restrict excursion, then you would also be minimizing distortion. The idea is to keep the excursion within the flat parts of the BL curve and the flatter parts of the suspension deflection curve. This would require a rather steep high pass for the mid or a higher crossover frequency. I guess if you used 6s (50% greater Sd) this would be less of a consideration – most of your challenge would be at the tweeter and its crossover.
But, all things considered, a well executed MTM (+ W or WW) is still hard to beat for overall performance.
sreten: just to clarify it would be a fairly typical floorstander with the mids and tweet in an MTM arrangement and two 6.5"s or one 8" for the woofer. I agree that the easiest way to good sound would be one tweet and woofer, but these have to go loud and multiple drivers will be a necessity.
Psych&sound: thanks for the info! Not much to add right now, I'm still digesting the advice and possibilities 🙂. I will be rounding up a number of drivers soon to put through the paces and see which one I will end up using in the speaker. Several of these have squared off flanges, such as the AC 130F1, and Peerless HDS Nomex. I don't mind trimming the tweet flange a bit, and with it offset a bit anyway, I think I might reach satisfactorily close woofers. For the tweeter roundup I'm including the Vifa D26, if it proves to be and otherwise excellent tweeter it would definately help with the solution. Also from what I've read even with the tweet down 3 or so dB at the interference frequency of the woofers, it still does a good job masking/removing that null.
So it's all really dependent on driver flange size, XO frequency, and slopes, none of which I can know in detail until I get the actual drivers. Which I can't buy until I know what size they will be!
If I crossed to the woofer around 300-400 Hz do any of you think this would increase power handling enough of the mid to go with a 5.25" and still have low distortion and power compression?
Thanks for the replies so far everyone!
Psych&sound: thanks for the info! Not much to add right now, I'm still digesting the advice and possibilities 🙂. I will be rounding up a number of drivers soon to put through the paces and see which one I will end up using in the speaker. Several of these have squared off flanges, such as the AC 130F1, and Peerless HDS Nomex. I don't mind trimming the tweet flange a bit, and with it offset a bit anyway, I think I might reach satisfactorily close woofers. For the tweeter roundup I'm including the Vifa D26, if it proves to be and otherwise excellent tweeter it would definately help with the solution. Also from what I've read even with the tweet down 3 or so dB at the interference frequency of the woofers, it still does a good job masking/removing that null.
So it's all really dependent on driver flange size, XO frequency, and slopes, none of which I can know in detail until I get the actual drivers. Which I can't buy until I know what size they will be!
If I crossed to the woofer around 300-400 Hz do any of you think this would increase power handling enough of the mid to go with a 5.25" and still have low distortion and power compression?
Thanks for the replies so far everyone!
The new M-165x from GR Research looks like a very nice mid driver for an MTM. I think my next speaker will probably use a pair of those with the Seas 27TDFC, open back on the MTM, then find the right woofer to do the bottom end.
That being said, the MTM I just finished using the Vifa M11WH and 80mm flange Peerless tweeter has turned out VERY nicely.
I guess what I'm saying is that 4.5" to 6.5" will work well, just need to choose the tweeter to match, need something like a Seas, with low Fs, to go with the 6.5", a less robust, smaller tweeter, with higher FS, can probably be used with smaller mids.
That being said, the MTM I just finished using the Vifa M11WH and 80mm flange Peerless tweeter has turned out VERY nicely.
I guess what I'm saying is that 4.5" to 6.5" will work well, just need to choose the tweeter to match, need something like a Seas, with low Fs, to go with the 6.5", a less robust, smaller tweeter, with higher FS, can probably be used with smaller mids.
M130-16 v M165-X
Hi Andy,
If you are going to use a woofer Wouldn't the M130-16 sound better from about 120hz on up than the M165-X. Being that the M130 has 35% less Mms, wouldn't it have better low level detail, or as Allen Wright calls it "Downward Dynamic Range” or DDR then the heaver M165? Also is there any way of incorporating a Wave guide like Zaph did with his TMM with a 1st Order series crossover or do wave guide's need a parallel network? If a series XO could work with a wave guide could you tempted in doing a large baffle TMM using the M130-16 feeding into this? http://www3.ocn.ne.jp/~hanbei/eng-intro.html
Thanks Andy for all your hard work and a willingness to share.
Ben
Hi Andy,
If you are going to use a woofer Wouldn't the M130-16 sound better from about 120hz on up than the M165-X. Being that the M130 has 35% less Mms, wouldn't it have better low level detail, or as Allen Wright calls it "Downward Dynamic Range” or DDR then the heaver M165? Also is there any way of incorporating a Wave guide like Zaph did with his TMM with a 1st Order series crossover or do wave guide's need a parallel network? If a series XO could work with a wave guide could you tempted in doing a large baffle TMM using the M130-16 feeding into this? http://www3.ocn.ne.jp/~hanbei/eng-intro.html
Thanks Andy for all your hard work and a willingness to share.
Ben
Ben,
John Krutke has an M-165X for testing. It will be interesting to see the outcome !!
Danny has recommended this driver in emails. And I sorta trust Danny too.
The waveguide on an MTM tweeter would probably push the mids too far apart I think. And if used open back, like I have found I really like at the moment, a woofer would be needed rather than a TMM approach
We will see. 😎
John Krutke has an M-165X for testing. It will be interesting to see the outcome !!
Danny has recommended this driver in emails. And I sorta trust Danny too.
The waveguide on an MTM tweeter would probably push the mids too far apart I think. And if used open back, like I have found I really like at the moment, a woofer would be needed rather than a TMM approach
We will see. 😎
Hi,
IMO the difference between a 2-way + sub and a 3-way is that for
a 2-way + sub all baffle step issues are dealt with by the 2-way.
IMO for a 3-way BSC issue are dealt with by the bass units, possibly
in combination with the mid unit, in this context a MTM mid/treble
section doesn't make any sense to me.
I not going to justify this, the MTM arrangement has no advantages.
(Except if you are stuck with particular drivers)
🙂/sreten.
IMO the difference between a 2-way + sub and a 3-way is that for
a 2-way + sub all baffle step issues are dealt with by the 2-way.
IMO for a 3-way BSC issue are dealt with by the bass units, possibly
in combination with the mid unit, in this context a MTM mid/treble
section doesn't make any sense to me.
I not going to justify this, the MTM arrangement has no advantages.
(Except if you are stuck with particular drivers)
🙂/sreten.
At about 300 Hz crossover, even with 2nd order slope, you should have very little issue with distortion using good 5" mid-woofers such as the Peerless HDS. Running the Woofers up to 300 Hz means that these would have to be quite good to over 600 Hz. However, you mentioned 2 - 6.5 or 1 - 8" for the Woofer. I think you may want to go a bit bigger or you will limit reasonably high output to above about 50 Hz before you run out of "go" with the smallish Woofers.
I designed a system (in production now) that used 2 extremely high excursion 10" (I designed the drivers as well and the Vd is approximately what you would expect out of a good pair of 15") to get to 20Hz at reasonable SPL.
I designed a system (in production now) that used 2 extremely high excursion 10" (I designed the drivers as well and the Vd is approximately what you would expect out of a good pair of 15") to get to 20Hz at reasonable SPL.
sreten please expound a little. Are you saying BSC would require taming of the mids which would defeat the purpose of an MTM? I guess I'm not totally understanding your point of view. i must emphasize that these will be doing HT work and fairly loud music occasionally, headroom is a must. Of course this moves the design from ideal to a little more compromised.
psych&sound a seperate sub will handle < 60 Hz. Although with room gain I think two 6.5"s or one 8" should be *acceptable* on the rare occasion they run without the sub. I say this because currently I have Onix Rocket 760s, which have two 6.5"s and the lower bass is actually pretty good.
Another consideration is aesthetics. A 10" would require a pretty big box. If you know of some low Vas models let me know. i may still consider it.
But I won't get to woofer selection until after I've tested out some mids. And I can't do that until I know what size to buy!
Andy I'll check out those drivers. Thanks for the suggestion.
psych&sound a seperate sub will handle < 60 Hz. Although with room gain I think two 6.5"s or one 8" should be *acceptable* on the rare occasion they run without the sub. I say this because currently I have Onix Rocket 760s, which have two 6.5"s and the lower bass is actually pretty good.
Another consideration is aesthetics. A 10" would require a pretty big box. If you know of some low Vas models let me know. i may still consider it.
But I won't get to woofer selection until after I've tested out some mids. And I can't do that until I know what size to buy!
Andy I'll check out those drivers. Thanks for the suggestion.
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