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I'm not familiar with how MBMs are managed in a system that is already running subs and is linear to 25Hz as mine is. With four subs running with HTM-12s, an 88 Special, and six Volt-10LXs, all with bass management at their respective required frequencies, I'm not even sure it's something from which I could benefit. It seems that if the system is already linear through the mid-bass region, the only benefit of running MBMs would be experienced if the main subs were a bit slow in attack of higher amplitude events (percussion in music, and sound effects in movies).

Education required. A primer would be helpful. Is there one somewhere?
The idea, IMO, of an MBM is mostly about fixing floor and ceiling bounce. By placing a driver on the floor and setting the crossover such that the dominant floor reflection from the speaker is placed in the stop band, you can achieve a very good midbass frequency response (60-120hz or so). This tends to be the hardest response to get right in a room.

It also has additional benefit like increased output, lower XO point to the subs if helpful, takes some load off the mains, etc.
 

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The idea, IMO, of an MBM is mostly about fixing floor and ceiling bounce. By placing a driver on the floor and setting the crossover such that the dominant floor reflection from the speaker is placed in the stop band, you can achieve a very good midbass frequency response (60-120hz or so). This tends to be the hardest response to get right in a room.
Thank you. I'm not familiar with "floor bounce" associated with LF acoustic response. I am familiar with non-LF floor issues such as floor coupling of an LCR close to the floor. What problem is being fixed for what transducer; the sub or the MBM?


Is this done by using the AVR/AVC crossover/HPF/bass management with the MBM connected as a sub? Then the sub utilizes another LPF from somewhere (if it's a passive sub) to splice with the low end of the MBM?


"Stop band?" Not familiar with the term.


More info, if you have the time, please. :)
 

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Thank you. I'm not familiar with "floor bounce" associated with LF acoustic response. I am familiar with non-LF floor issues such as floor coupling of an LCR close to the floor. What problem is being fixed for what transducer; the sub or the MBM?


Is this done by using the AVR/AVC crossover/HPF/bass management with the MBM connected as a sub? Then the sub utilizes another LPF from somewhere (if it's a passive sub) to splice with the low end of the MBM?


"Stop band?" Not familiar with the term.


More info, if you have the time, please. :)
Im talking about the suckout caused by the midwoofer of the speaker. This is usually in the 150-250hz range. Stop band is the region being attenuated by the crossover. So if we put a high pass on the speaker at 300hz then the reflection off the floor is being attenuated. If the mbm is close to the floor then the floor reflection will be at say 500-600hz or so. With the 300hz crossover the floor reflection is in that stop band. So with the primary floor reflection in the stop band of each driver (speaker midwoofer and mbm) we have nearly elimated any floor bounce issues. If also has some affect on ceiling reflections BTW.

Does that help? Im answering from a phone so not comprehensive. I had a good thread about this somewhere on the forum before.
 

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Thank you. I'm not familiar with "floor bounce" associated with LF acoustic response. I am familiar with non-LF floor issues such as floor coupling of an LCR close to the floor. What problem is being fixed for what transducer; the sub or the MBM?


Is this done by using the AVR/AVC crossover/HPF/bass management with the MBM connected as a sub? Then the sub utilizes another LPF from somewhere (if it's a passive sub) to splice with the low end of the MBM?


"Stop band?" Not familiar with the term.


More info, if you have the time, please. :)
http://www.avsforum.com/forum/401-d...ass-module-your-diy-sound-group-speakers.html I think that is the thread tux is referring to.
 
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Thank you. I think I found the answer to my questions in the first paragraph of that:

"Some people have expressed the desire for stupid amounts of mid bass. Also, sometimes people can only afford a smaller design, and want the ability to upgrade later. Adding an MBM is one way to extend the life of a smaller DIYsoundgroup design before you outgrow it."

If you have a system that is appropriately sized for your room/environment, bass management has provided a good splice between the main speaker and the subwoofer, and the system is acoustically linear through the subwoofer range, there is not reason for a MBM other than the desire to make the system non-linear; bloated in the mid-bass region.

I have HTM-12s and plenty of sub capability/headroom. The system is appropriately sized for the room and equalized. It is linear through the entire spectrum. Therefore, I don't need an MBM.

I guess I can see a scenario where there is not room to place an adequately large main speaker in a room. If that smaller LCR speaker does not have the acoustic response to reach low enough to adequately splice with the subwoofer(s)--and that would be mighty small for any DIYSG design--, I can see how an MBM might bridge the response gap. But that is even more bass management work to do to achieve smooth/linear response through that transition zone.

Otherwise, it would seem that the need for an MBM is more of a Band-Aid for a system that is not designed/selected to have synergistic acoustic performance in the room. Seems a peculiar concept/utility, especially for designs as efficient as those of DIYSG.

I hope I'm missing something, because I love to have more stuff. :D
 

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You are missing something, but Im sorry to tell you that you dont need more stuff.

If your system had a suckout in the 150hz area due to floor bounce you would benefit from an MBM. It is actually one of the only ways to deal with it. Eq is not an appropriate way to fix such a suckout. No matter how crazy your speakers may be, they cant beat physics. Thats where thr mbm comes in. It fixes the physics.
 

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Otherwise, it would seem that the need for an MBM is more of a Band-Aid for a system that is not designed/selected to have synergistic acoustic performance in the room. Seems a peculiar concept/utility, especially for designs as efficient as those of DIYSG.
In most cases the room is the room, and often no amount of "designing/selecting to have synergistic acoustic performance" is going to mitigate the problems of floor bounce and bounce from the wall behind the speakers. You have an advantage in that flush-mounting your LCR speakers is a workable choice for you, and the fact that you don't suffer from midbass issues resulting from floor bounce at the listening position is at least partly sheer luck. (These kinds of issues can't be EQ'd out by the way, nor solved by getting bigger/badder mains.)

If your system measures to your liking then I guess you're right, there's no need for you personally to add any MBMs to the mix. I don't think it's fair, however, to paint the concept as a band-aid; many, many rooms have unavoidable problems in the midbass with any sensible arrangement of speakers and listener, and I believe a well-implemented MBM is a perfectly valid tool in those cases.

edit: figures Mr. Tux would beat me to the punch. :D
 

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You are missing something, but Im sorry to tell you that you dont need more stuff.

If your system had a suckout in the 150hz area due to floor bounce you would benefit from an MBM. It is actually one of the only ways to deal with it. Eq is not an appropriate way to fix such a suckout. No matter how crazy your speakers may be, they cant beat physics. Thats where thr mbm comes in. It fixes the physics.
In most cases the room is the room, and often no amount of "designing/selecting to have synergistic acoustic performance" is going to mitigate the problems of floor bounce and bounce from the wall behind the speakers. You have an advantage in that flush-mounting your LCR speakers is a workable choice for you, and the fact that you don't suffer from midbass issues resulting from floor bounce at the listening position is at least partly sheer luck. (These kinds of issues can't be EQ'd out by the way, nor solved by getting bigger/badder mains.)


If your system measures to your liking then I guess you're right, there's no need for you personally to add any MBMs to the mix. I don't think it's fair, however, to paint the concept as a band-aid; many, many rooms have unavoidable problems in the midbass with any sensible arrangement of speakers and listener, and I believe a well-implemented MBM is a perfectly valid tool in those cases.

edit: figures Mr. Tux would beat me to the punch. :D
Thanks guys. I'm pleased to find something to learn of which I was not knowledgeable. :eek: I'll have to ponder this a bit. :)


Antisuck, I see your point. The "Band-aid" can be a useful tool in a specific room where it can be effective.
 

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Personally speaking now that I have an MBM, the modes it fixes are awesome but having a slightly bloated mid bass region adds to the experience. The biggest gain is probably with music and bass players or drummers.

My towers were already a little heavy on the midbass but I couldn't EQ in greater amplification due to me being on a cheap AVR. Now I can EQ in using my inuke.


Sent from my iPhone using Tapatalk
 

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Personally speaking now that I have an MBM, the modes it fixes are awesome but having a slightly bloated mid bass region adds to the experience. The biggest gain is probably with music and bass players or drummers.

My towers were already a little heavy on the midbass but I couldn't EQ in greater amplification due to me being on a cheap AVR. Now I can EQ in using my inuke.


Sent from my iPhone using Tapatalk
Do you have your LFE daisychained with your LR pre-outs?
 

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No, its all being handled my LFE right now. I don't have pre-outs on the X1200.

My MBM's are daisied off of one channel on the Inuke and my UM18 on the other.
What's your crossover set at?

Also, do you plan on getting a different AVR?
 

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Lol. Its very close. Im on the west coast so just got home from work. Dont get to excited. Just a bunch of measurements. Not much we didnt already know :)


I'm excited to see their performance in a smaller box.

I'm sort of second guessing the size of my boxes. I was too keyed in on chuffing I think.


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I have two of the DIY MBM's in my setup. Mains are tannoy Definition 12's. Have a UM-18 ported sub in between the MBM's, which are mounted directly below L and R mains. MBM's and L R mains are used as a large front stage (i.e., not running through LFE output). Crossover is at 200. I use the DSP in a crown CTs4200 amp to set crossover on tops and bottoms and delays. I love the setup because you can run the MBM's a tiny bit hot for kick and bass guitar (only couple dB's) and it does not otherwise affect the LFE level on other channels. My room is square and has never measured like a dedicated theater, but the MBM's helped even the mid bass frequencies. Have a narrow 8 dB null at 60hz, but that's probably as good as I'm going to get without bass traps everywhere.

The system sounds much more punchy to me with them. I'm a fan.
 

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I'm excited to see their performance in a smaller box.

I'm sort of second guessing the size of my boxes. I was too keyed in on chuffing I think.


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That makes me feel a bit better about my design. My forward facing is going to be between 1.2 and 1.27 tubes at 45 or 46 depending. Downward or rear facing I'm closer to 1.4 to 1.45.
 
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