Going from a similar MTM to a more simpler TM, I enjoy listening to the TM a bit more. I know I'll lose some output (my main concern), but is there anything else that you can convince me to stay with another MTM ?
The more I think about it, the more I see that the Orion design is where I'm headed. I'd like to experiment with a full 4 way active system. But, don't have the amps and the processing power just yet.
What do you think?
The more I think about it, the more I see that the Orion design is where I'm headed. I'd like to experiment with a full 4 way active system. But, don't have the amps and the processing power just yet.
What do you think?
I am a few steps ahead on a similar journey. I started with MTMs, first with 6" drivers then 7". Went looking for quality sound in a space saving design, so built some 6" MTs. Still looking for something...
I am a bit of a dynamics nut, so the loss of maximum output level was a big deal to me. Note that I said dynamics, not loud average listening
Another factor that seems to affect the sound character is cancellation of some floor bounce modes in the MTM that are present in the MT. I was able to alleviate some of this with a big flokati rug with 2" of open cell foam under it between me and the speakers.
Even though the drivers and resulting system are more accurate than my older ones, there is something missing on peaks. I'm heading back to MTM land or possibly an open baffle Orion inspired design.
If you are ready to start on the "processing power" side and don't want to go digital, I bought extra filter boards for the group buy. If you plan to build the Orion, not a clone, buy SL's kit and boards. The group buy boards have all the features that SL says are necessary for a proper active system. See the group buys section, WIKI or my www button for info.
I am a bit of a dynamics nut, so the loss of maximum output level was a big deal to me. Note that I said dynamics, not loud average listening
Another factor that seems to affect the sound character is cancellation of some floor bounce modes in the MTM that are present in the MT. I was able to alleviate some of this with a big flokati rug with 2" of open cell foam under it between me and the speakers.
Even though the drivers and resulting system are more accurate than my older ones, there is something missing on peaks. I'm heading back to MTM land or possibly an open baffle Orion inspired design.
If you are ready to start on the "processing power" side and don't want to go digital, I bought extra filter boards for the group buy. If you plan to build the Orion, not a clone, buy SL's kit and boards. The group buy boards have all the features that SL says are necessary for a proper active system. See the group buys section, WIKI or my www button for info.
Thanks Bob,
What drivers are you using if you don't mind me asking? Dynamics is something that I'm sought after too and I'm sure with a simple 6" or 7" mid, it just won't cut it for me.
I have yet to analyze why I like the MT more or why it sounds better, but, like you, I've already found its weakness. (output + dynamics)
Currently, I'm comparing the dayton rs160/seas 27 MT vs. dayton rs180/seas 27 MTM. The MT is a boxed design and the MTM is a dipole. The processors are the Behringer deq and the dcx.
I've considered the active boards since the groupbuy started, but now that the DCX are back in stock again, it's really hard for me not to consider another dcx and chain both.
Would high efficiency drivers help me out? Or is there anything that I can do to improve on my MTM dipole?
What drivers are you using if you don't mind me asking? Dynamics is something that I'm sought after too and I'm sure with a simple 6" or 7" mid, it just won't cut it for me.
I have yet to analyze why I like the MT more or why it sounds better, but, like you, I've already found its weakness. (output + dynamics)
Currently, I'm comparing the dayton rs160/seas 27 MT vs. dayton rs180/seas 27 MTM. The MT is a boxed design and the MTM is a dipole. The processors are the Behringer deq and the dcx.
I've considered the active boards since the groupbuy started, but now that the DCX are back in stock again, it's really hard for me not to consider another dcx and chain both.
Would high efficiency drivers help me out? Or is there anything that I can do to improve on my MTM dipole?
My current setup uses Focal 6W4254 midbass units and either a Focal TC120TDX or Fountek JP3 tweeter. I built otherwise identical boxes. The old MTMs used Focal coated paper drivers and the kevlar T120 tweeter. I also use a pair of RS150/27TDFC MTs in my bedroom. The bedroom speakers sound a little different than the mains, but are quite good. Hard to choose a favorite. Amazing since the bedroom total driver cost was 1/4 of what I spent on the Focals...
I'm either going to a Dayton RS225/RS150/27TBFC/G MTMWW or if I like the open baffle and waveguide experiments I'll probably end up with an RS225/27TDFC(waveguide) MTM on top of a pair of RSS315s per side. Daytons are excellent performers, and freight to Pennsylvania is cheap and fast.
I have all the drivers save the 315s on hand. Until I get the 315s my subs can handle up to 150 Hz fairly easily.
My guess is that you might be trying to get too much bottom end out of your MTMs. The RS180s are really large flange 6" drivers. Asking them to go as low as 200 Hz open baffle is probably asking too much (unless the baffle is huge).
I go back and forth on the high efficiency issue. On one hand the dynamics of my college roommate's A7-500s was wonderful, but they had a distinct ringing horn honk. Currently I lean towards drivers optimized for low distortion and using multiples to get the surface area needed for dynamics/extension. I have plenty of amplifier power available.
I'm either going to a Dayton RS225/RS150/27TBFC/G MTMWW or if I like the open baffle and waveguide experiments I'll probably end up with an RS225/27TDFC(waveguide) MTM on top of a pair of RSS315s per side. Daytons are excellent performers, and freight to Pennsylvania is cheap and fast.
I have all the drivers save the 315s on hand. Until I get the 315s my subs can handle up to 150 Hz fairly easily.
My guess is that you might be trying to get too much bottom end out of your MTMs. The RS180s are really large flange 6" drivers. Asking them to go as low as 200 Hz open baffle is probably asking too much (unless the baffle is huge).
I go back and forth on the high efficiency issue. On one hand the dynamics of my college roommate's A7-500s was wonderful, but they had a distinct ringing horn honk. Currently I lean towards drivers optimized for low distortion and using multiples to get the surface area needed for dynamics/extension. I have plenty of amplifier power available.
Not yet Salas.
My room is on the small side - proper dipole spacing from the back wall will mean I have to put a speaker in such a way that the cables interfere with coming in the door. I guess it will have to be on casters so I can easily pull them out to a proper position and stow them when not in use.
My room is on the small side - proper dipole spacing from the back wall will mean I have to put a speaker in such a way that the cables interfere with coming in the door. I guess it will have to be on casters so I can easily pull them out to a proper position and stow them when not in use.
salas said:
BobEllis said:
Hi Bob, and Salas;
I happened upon a very nice AES article by Juha Backman which seems to pretty much agree with my assessment of different woofer systems. I have favored cardioid woofers over dipoles for some time. Backman finds that in the modal region cardioid woofers are least sensitive to room placement where as dipoles are the most sensitive. Below the first mode, dipole SPL drops off because of the inability to pressurize the room, however, below the first mode he finds no advantage to cardioids over monopoles since both are capable of room pressurization. But monopoles are, of course, more efficient in that range. I have some excerpts from Backmans's paper over at my site in the discussion of the Mini design. http://www.musicanddesign.com/NaOMinidiscus.html
It has been my feeling for a long time now that the major apparent benefit of dipole woofers is really their weakness, the inability to excite the room below the fundamental. As a result, dipole woofers don’t over load a room when the woofer's cut off frequency is below the room fundamental the way cardioid and monopole woofer do. The result is that the real devil here is that monopole and cardiod woofers aren't often tuned correctly to the room. There is a lot of, "the lower the F3 the better" attitude with regard to woofers, particularly for HT use, and that is a recipe for problems. But with a dipole with 20 Hz cut off in a room that can only support 35 Hz, the dipole just fades under 35 Hz. As a result the dipole won’t sound blotted or boomy when mismatched to the room. For a monopole or cardiod the first thing that has to be done is to optimize the F3 and Q (assuming a sealed box woofer) to match the room.
I know it's not the popular view as there is a great deal of favorable subjective evaluation of dipole woofers. But my own experimental, analytical and subjective evaluations seem a bit contrary to this and it was nice to see another effort which seems to agree. As I said, I believe the major reason for the positive subjective evaluation is the room pressurization factor.
Martin Logan uses 'Force Forward' a.k.a cardioid and offcourse dipole mid-high by definition.
In Line Array professional systems circles though, after having made some systems with cardioid bass so to steer as much of the whole array output better, there was some consensus that in the end monopole was better. But there we talk humongus halls and open air.
In Line Array professional systems circles though, after having made some systems with cardioid bass so to steer as much of the whole array output better, there was some consensus that in the end monopole was better. But there we talk humongus halls and open air.
Can you explain to me what exactly is a cardioid set up?
I also went over to John K's webpage and see that you chose the U frame for your Nao speakers. And here I'm getting the impression that you prefer monopole and cardioid over dipole?
While we're on the topic of dipole woofers, I have the bottom portion of the Phoenix dipole (by LR) with the original woofers that Linkwitz used. What can I do to get more output out from them? I have equalization power, but I'd prefer to make another box to get the best out of them.
http://www.linkwitzlab.com/woofer.htm
I also went over to John K's webpage and see that you chose the U frame for your Nao speakers. And here I'm getting the impression that you prefer monopole and cardioid over dipole?
While we're on the topic of dipole woofers, I have the bottom portion of the Phoenix dipole (by LR) with the original woofers that Linkwitz used. What can I do to get more output out from them? I have equalization power, but I'd prefer to make another box to get the best out of them.
http://www.linkwitzlab.com/woofer.htm
John K,
I for one am in agreement with you about a preference for cardoid or at a minimum cardoidish for the bass region on down. To me what makes is worth the extra effort over monopole is that we still have the highly directional sound (greatly reduced room effects similar to dipole) without the loss of extension.
I've read your description before about the lack of room pressurization being the limitation for dipole bass. In my mind though, for a dipole operating below the room fundamental, the baffle size ceases to be of importance and the room dimension itself causes the higher degree of cancellation between the 2 waves. ie On axis the front and rear waves must net to much less below the room fundamental with dipole.
I for one am in agreement with you about a preference for cardoid or at a minimum cardoidish for the bass region on down. To me what makes is worth the extra effort over monopole is that we still have the highly directional sound (greatly reduced room effects similar to dipole) without the loss of extension.
I've read your description before about the lack of room pressurization being the limitation for dipole bass. In my mind though, for a dipole operating below the room fundamental, the baffle size ceases to be of importance and the room dimension itself causes the higher degree of cancellation between the 2 waves. ie On axis the front and rear waves must net to much less below the room fundamental with dipole.
sqlkev,
I've used the W-baffle layout to create a hybrid toward a cardoid response by sliding the driver mounting panels all the way to the front edge of the cab and extending the outer panels deeper. Making the distance to clear the front of the unit significantly shorter than the distance for the rear wave to clear the cab significantly moves the area of highest cancellation rearward from the usual dipole 90 degree plane.
This way you still enjoy the benefits of the W-baffle, vibration cancellation, ease of implementing push/pull, and compact size. Plus you gain the extension benefits that JohnK advocates. The only real detriment that I see is that you need some extra power because compact manifolds load the cone with more air mass which lowers sensitivity and Fs.
I've used the W-baffle layout to create a hybrid toward a cardoid response by sliding the driver mounting panels all the way to the front edge of the cab and extending the outer panels deeper. Making the distance to clear the front of the unit significantly shorter than the distance for the rear wave to clear the cab significantly moves the area of highest cancellation rearward from the usual dipole 90 degree plane.
This way you still enjoy the benefits of the W-baffle, vibration cancellation, ease of implementing push/pull, and compact size. Plus you gain the extension benefits that JohnK advocates. The only real detriment that I see is that you need some extra power because compact manifolds load the cone with more air mass which lowers sensitivity and Fs.
Mine use a double stack of cheapie 12's per side. I was able to shoehorn them in to a front 12"w by 25"h. The depth of the W portion is 13.5" and I added an extra 8" to the back (be sure to brace anywhere possible). Use Linkwitz's Fequal formula to determine at what point you want bass roll-off to start. Which boils down to Fequal = 58.3 / D in meters (D is the added travel distance by the rear wave). For his dipole woofer D is 19" although he shortcuts how to measure the 19" since it's dipole. For yours D is the depth of the driver manifold plus 2 times the amount of depth you add. That's where JohnK's U-baffle +6db comes from. The rear wave must travel back around the edge of the baffle then forward, and double the D moves Fequal down one octave. My total depth of 21.5" got me to an Fequal of 78hz vs the 19" deep Linkwitz model at 120hz.
78hz works fine for me, since that's free space and floor loading adds back 6db making it more like 40hz (rich and deep).
In your case, I'd just try a temporary add-on to the back to help you decide your overall depth. You do need some polyfill in the back to prevent resonances. Bracing also helps raise the frequency of some, but not the 1/4 resonance based on depth.
I used the Ripole idea of magnet through the side panels to reduce the size, and something I realized afterward is that thicker panels in the driver mounting baffles actual result in small potential minimum width of the overall cab. With narrow widths, I'd suggest the center pathway to the front, as you need uniformity to creat equal loading on both sides of all cones. I made the sum of my 2 rear pathways 1" greater than the area of my front pathway and added stuffing to the rear to tune and equalize the air mass load. I guess you could make the center pathway to the rear and have a narrower extension toward the back, but you would have to make it larger than the sum of the left and right pathways going the other direction, resulting in a wider overall cab.
Here's a crude drawing of the top view of mine. Note that the stack above had the drivers facing the other direction for weight balance and symmetry in the pathways left and right.
78hz works fine for me, since that's free space and floor loading adds back 6db making it more like 40hz (rich and deep).
In your case, I'd just try a temporary add-on to the back to help you decide your overall depth. You do need some polyfill in the back to prevent resonances. Bracing also helps raise the frequency of some, but not the 1/4 resonance based on depth.
I used the Ripole idea of magnet through the side panels to reduce the size, and something I realized afterward is that thicker panels in the driver mounting baffles actual result in small potential minimum width of the overall cab. With narrow widths, I'd suggest the center pathway to the front, as you need uniformity to creat equal loading on both sides of all cones. I made the sum of my 2 rear pathways 1" greater than the area of my front pathway and added stuffing to the rear to tune and equalize the air mass load. I guess you could make the center pathway to the rear and have a narrower extension toward the back, but you would have to make it larger than the sum of the left and right pathways going the other direction, resulting in a wider overall cab.
Here's a crude drawing of the top view of mine. Note that the stack above had the drivers facing the other direction for weight balance and symmetry in the pathways left and right.
An externally hosted image should be here but it was not working when we last tested it.
(JPK) I had prepared a long reply but a malfunction seems to have erased it. Sorry, I'm not going to try to retype the entire thing again. The bottom line is that I still favor cardioids to minimize room interactions. My experience and testing with the NaO II, which has a woofer system that can be switched between a U-frame and a monopole, and the CRAW, which operates as a monopole, cardioid or dipole with the same on axis response) seemed to bare this out. But below the room fundamental there really isn't any difference between a cardioid and a monopole except that the monopole is a more efficient means of pressurizing a room. This lead Backman to propose a woofer system that transforms from cardioid above the room fundamental to monopole below the fundamental as an efficient means of efficiently extending bass response while minimizing room interaction and sensitivity to placement. I was very happy to come across the Backman paper which seems support much of my experience. The Mini accomplishes the transition of cardioid to monopole suggested by Backman using a novel approach which is discussed at my web site. It may not be perfect, but it is effective at controlling the rear wave and minimizing room interaction in the critical lower mid, midbass frequency range. Additionally, it is a simpler solution than the U-frame for which correct operation is critically dependent on the damping of the cabinet.
John, I was reading an interview in Pro Sound Europe (unfortunately I dont have the issue so to quote or tell you the name of the guy) and he said that after using Meyer cardiods for long as for taking advantage of quiter stage in LF etc and better driving of halls for nodes etc. he had come to the conclusion that it lacked pressure vs monopole in enclosed spaces and have reverted back to monopole subs. I think he was from Meyer but I cant recall exactly. Are you aware of such references from pro line array world?
(JPK) I'm not aware of the particular review, but I am aware of Meyer. The pressurization thing is just a little more complicated than what I or Backman implied. It assumes that the monopole and cradioid have the same free air response all the way to DC. If you look at my site http://www.musicanddesign.com/roomgain.html
you will see Figure 1
which can be interpreted as the variation in volume displacement vs frequency for an uneualized cardioid constructed from two hypothetical monopoles with flat free air response to DC. Obviously we can't have flat response to DC, but the point here is that where the monopole would have constant volume displacemment the cardioid volume displacement drops off at 6dB/octave. As I am sure you are aware, the cardioid, as with a dipole, requires 6dB/octave equalization. Thus a cardioid or dipole constructed from two monopoles must have 6dB/ocatve equalization applied to DC if it is to have exactly the same free air response as a monopole, to DC. This is, of course, impossible since it would require infinite gain as DC is approached. Thus when a cardioid is equalized to have the same response as the monopole sources used in its construction, the equalization must be cut off at some point. Typically the eq is cut off some where around 1/2 octave below the target system low frequency cut off. Thus, if the monopole sources have a second order roll off the cardioid will only match that roll off to the point where the eq stops. Below that the cardioid will have a 3rd order roll off and the volume displacement will roll off at 6dB/octave as shown in the figure, and so will the ability to pressurize a room.
So it's really another aspect of the sensitivity issue brough about by the need to apply eq to the cardioid. The monopole has better sensitivity as the frequency drops because it doesn't need eq and on top of that there is the pratical issue of how low in frequency the eq can be reasonalbly applied. That is usually limited to about a decade, or 20 dB or eq. at the lowest frequency.
you will see Figure 1
An externally hosted image should be here but it was not working when we last tested it.
which can be interpreted as the variation in volume displacement vs frequency for an uneualized cardioid constructed from two hypothetical monopoles with flat free air response to DC. Obviously we can't have flat response to DC, but the point here is that where the monopole would have constant volume displacemment the cardioid volume displacement drops off at 6dB/octave. As I am sure you are aware, the cardioid, as with a dipole, requires 6dB/octave equalization. Thus a cardioid or dipole constructed from two monopoles must have 6dB/ocatve equalization applied to DC if it is to have exactly the same free air response as a monopole, to DC. This is, of course, impossible since it would require infinite gain as DC is approached. Thus when a cardioid is equalized to have the same response as the monopole sources used in its construction, the equalization must be cut off at some point. Typically the eq is cut off some where around 1/2 octave below the target system low frequency cut off. Thus, if the monopole sources have a second order roll off the cardioid will only match that roll off to the point where the eq stops. Below that the cardioid will have a 3rd order roll off and the volume displacement will roll off at 6dB/octave as shown in the figure, and so will the ability to pressurize a room.
So it's really another aspect of the sensitivity issue brough about by the need to apply eq to the cardioid. The monopole has better sensitivity as the frequency drops because it doesn't need eq and on top of that there is the pratical issue of how low in frequency the eq can be reasonalbly applied. That is usually limited to about a decade, or 20 dB or eq. at the lowest frequency.
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