Adding an MBM (mid bass module) to your DIY Sound Group speakers - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 259 Old 03-16-2015, 09:17 AM - Thread Starter
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Adding an MBM (mid bass module) to your DIY Sound Group speakers

THIS IS A WORK IN PROGRESS

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. Or maybe you move from a small HT to a large one, add an MBM and you'll find it helps a lot. It also helps with room modes, especially floor bounce. It's sometimes a little daunting for the newb. Here's a ready made prescription how to do it.

What you'll need:

1. A woofer. (Woofer options further down)
2. The ability and materials to build a ported cube.
3. Pre-outs on your AVR.
4. Some form of DSP such as a minidsp, built in amp dsp (inuke or ipr), etc.
5. Two channels of external amplification per speaker being upgraded with an MBM (if the amp already has dsp like an inuke, then you'd need one amp per speaker).

Requirement 5 is what makes MBMs a bit costly. You need to budget about $500 per speaker to do this. But you do get the added benefit of external amplification, which a lot of people already do, so...

WOOFER OPTIONS

The best bang for the buck comes from the Magnum 12 and MBM flat pack found here: http://www.diysoundgroup.com/midbass-module/mbm-12.html

Also useable is:
- Celestion FTR12-3070C reasonable value and box size, though doesn't tune quite as low as the Magnum 12.
- JBL 2226 requires a large cabinet and expensive, though has more output available and can be used sealed.
- Dayton PA255-8 requires a large cabinet considering it's only 10", but is very affordable.

MAGNUM 12


More details will be coming.

Based on the anticipated box dimensions (waiting on Erich), there should be a floor null at 500hz roughly. If a Fusion 8 or Fusion 10 is placed on top of the MBM, there will be a floor null around 175hz roughly for that. For a bigger speaker like the Fusion 12, you get a null around 150hz. This is the basis for the settings below.

Channel 1 to MBM
- Low Pass = LR 24db/oct at 250hz
- Level = 0
- EQ should be based on measurements

Channel 2 to DIY Sound Group Speaker (ie. Fusion 8 or 10)
- High Pass = LR 24db/oct at 250hz
- Level = -5db (Fusion 10), -5db (Fusion 12), -6db (Cinema 8), -6db (Cinema 10 MAX), -7db (Cinema 1099)
- EQ may be available to further smooth the speaker response over an above what the passive XO does, ask the designer.

ENCLOSURE DETAILS DAYTON PA255-8

Sealed 18L.

I used these built into a speaker rather than MBM, but here's a pic anyways.




Frequency response



Very usable extension to 70 or even 60hz and sealed. Quite good.

Impedance




DSP SETTINGS DAYTON PA255-8

Based on the box description above, there should be a floor null at 500hz roughly. If a Fusion 8 or Fusion 10 is placed on top of the MBM, there will be a floor null around 175hz roughly for that. For a bigger speaker like the Fusion 12, you get a null around 150hz. This is the basis for the settings below.

Channel 1 to MBM
- Low Pass = LR 24db/oct at 250hz
- Level = -1db (Fusion 6)
- EQ should be based on measurements

Channel 2 to DIY Sound Group Speaker (ie. Fusion 8 or 10)
- High Pass = LR 24db/oct at 250hz
- Level = -5db (Fusion 10), -5db (Fusion 12), -6db (Cinema 8), -6db (Cinema 10 MAX), -7db (Cinema 1099)
- EQ may be available to further smooth the speaker response over an above what the passive XO does, ask the designer.

AVR subwoofer XO at 60hz or higher for maximum performance.

Feel free to change levels to get the balance that fits your room and listening preferences. Those are guidlines only. Especially if two MBMs per speaker are used. Then roughtly 6db additional sensitivity should be compensated for. This woofer would do well in pairs. Feel free to ask questions.


ENCLOSURE DETAILS CELESTION FTR12-3070C

14.5"x17.5"x12" (Outside wxhxd using 3/4" materials).

This design requires two ports per box down in the corners. Ports can be slotted, triangle, or prefabricated. For the prefabricated round port, I recommend this one: http://www.parts-express.com/speaker...lared--260-478 It's ready to go. Just install them.

Slot and triangle port dimensions coming.






DSP SETTINGS CELESTION FTR12-3070C

Based on the box description above, there should be a floor null at 450hz roughly. If a Fusion 8 or Fusion 10 is placed on top of the MBM, there will be a floor null around 150hz roughly for that. For a bigger speaker like the Fusion 12, you get a null around 130hz. This is the basis for the settings below.

Channel 1 to MBM
- Low Pass = LR 24db/oct at 225hz
- Level = -4db (Fusion 6), -0db (Fusion 8)
- EQ should be based on measurements

Channel 2 to DIY Sound Group Speaker (ie. Fusion 8 or 10)
- High Pass = LR 24db/oct at 225hz
- Level = -2db (Fusion 10), -2db (Fusion 12), -3db (Cinema 8), -3db (Cinema 10 MAX), -4db (Cinema 1099)
- EQ may be available to further smooth the speaker response over an above what the passive XO does, ask the designer.

AVR subwoofer XO at 60hz or higher for maximum performance.

Feel free to change levels to get the balance that fits your room and listening preferences. Those are guidlines only. Especially if two MBMs per speaker are used. Then roughtly 6db additional sensitivity should be compensated for. Feel free to ask questions.

ENCLOSURE DETAILS JBL 2226J/H

22"x17.5"x24" (Outside wxhxd using 3/4" materials).

This is a sealed enclosure and can be run full range, though crossing over to subs is still recommended.

Here's a GP measurement. I'll update with better data, but for now this is what I have, unsmoothed with a couple reflections sneaking in.



Test boxes.




DSP SETTINGS JBL 2226J/H

Based on the box description above, there should be a floor null at 450hz roughly. If a Fusion 8 or Fusion 10 is placed on top of the MBM, there will be a floor null around 150hz roughly for that. For a bigger speaker like the Fusion 12, you get a null around 130hz. This is the basis for the settings below.

Channel 1 to MBM
- Low Pass = LR 24db/oct at 225hz
- Level = -5db (Fusion 6), -1db (Fusion 8)
- EQ should be based on measurements

Channel 2 to DIY Sound Group Speaker (ie. Fusion 8 or 10)
- High Pass = LR 24db/oct at 225hz
- Level = -1db (Fusion 10), -1db (Fusion 12), -2db (Cinema 8), -2db (Cinema 10 MAX), -3db (Cinema 1099)
- EQ may be available to further smooth the speaker response over an above what the passive XO does, ask the designer.

AVR subwoofer XO is flexible and may even be run full range.

Feel free to change levels to get the balance that fits your room and listening preferences. Those are guidlines only. Feel free to ask questions.



I will eventually add woofers I use and feel are worth MBM drivers as I come across them. HINT, Erich has obtained a really wicked 12" woofer that will make a great MBM and only cost a bit more than the Celestion.
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Last edited by tuxedocivic; 10-23-2015 at 08:16 AM.
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post #2 of 259 Old 03-16-2015, 09:56 AM
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Quote:
Originally Posted by tuxedocivic View Post
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. Or maybe you move from a small HT to a large one, add an MBM and you'll find it helps a lot. It also helps with room modes, especially floor bounce. It's sometimes a little daunting for the newb. Here's a ready made prescription how to do it.

What you'll need:

1. A Celestion FTR12-3070 woofer per MBM.
2. The ability and materials to build a ported cube.
3. Pre-outs on your AVR.
4. Some form of DSP such as a minidsp, built in amp dsp (inuke or ipr), etc.
5. Two channels of external amplification per speaker being upgraded with an MBM (if the amp already has dsp like an inuke, then you'd need one amp per speaker).

Requirement 5 is what makes MBMs a bit costly. You need to budget about $500 per speaker to do this. But you do get the added benefit of external amplification, which a lot of people already do, so...

I'll provide the box and port dimensions soon. Also the dsp settings soon. This is to get things going.

This is how I use the MBMs under a one off descign similar to the Fusion 12.



Here's a ground plane measurement of the MBM described in this post:



I will eventually add woofers I use and feel are worth MBM drivers as I come across them.
Tux,

Came over here to check out the new DIY postings and caught your MBM thread.
I am happy to see you posted the following as one reason to add MBMs:
"It also helps with room modes, especially floor bounce"
I Thank You again for helping me with this solution !

(Side-note; I'm curious for #2 ; why do you specify a ported cube?)

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post #3 of 259 Old 03-16-2015, 10:08 AM - Thread Starter
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Glad that's still working out for you.

Your right, could be sealed. For this woofer though, it likes being ported. And a lot of people want to cross to subs lower, so the porting helps with that.
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post #4 of 259 Old 03-16-2015, 10:55 AM
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Quote:
Originally Posted by tuxedocivic View Post
Glad that's still working out for you.

Your right, could be sealed. For this woofer though, it likes being ported. And a lot of people want to cross to subs lower, so the porting helps with that.
Duh - a lower crossover.
Should have thought of that.

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post #5 of 259 Old 03-16-2015, 07:18 PM
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Is it possible to integrate MBMs by using only the sub out on an avr with the mains crossed higher? Maybe 150hz. Then use a two channel amp like an inuke to send 0-40ish to a sub then 40-150 to the MBMs. This would eliminate the "stereo" of the MBMs but would be simpler as far as equipment needed. I can see where mono MBMs could be an issue with imaging but if they were stacked under the mains it seems like it could work. Especially for those of us without pre-outs.
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post #6 of 259 Old 03-16-2015, 07:55 PM - Thread Starter
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Samps, that would work although as you identified limits the stereo bass. Probably hard to localize though. In any case, you'd follow the same steps I'll outline here soon.
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post #7 of 259 Old 03-21-2015, 11:22 AM
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Did you veneer that? It looks really good.
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post #8 of 259 Old 03-21-2015, 02:20 PM - Thread Starter
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Thanks, it's cabinet grade maple plywood. Basically high quality plywood with veneer already on it. Tinted black lacquer finish.
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JBL 2226 woofers might make a good midbass module. I did some recently, the output of them is quite stupid. I have a source for official JBL recones for $125 each, that's almost stealing. The woofers sell for $503 each on PE (no thanks!) but there is often a lot of good quality sources in the used market. I see ebay deals and stuff pop up from time to time, I know Erich had gotten a big group buy of them in the past as well. Those might be a good MBM woofer choice if you can find them for reasonable prices. I see guys around here buying those all the time.
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post #10 of 259 Old 03-23-2015, 08:59 AM
 
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One thing I noticed is you are basically making it a semi active 3 way, by crossing the SEOS design 24db/octave at 225hz ? What is the benefit of that versus running the SEOS down a bit farther?
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post #11 of 259 Old 03-23-2015, 09:40 AM - Thread Starter
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Quote:
Originally Posted by Mfusick View Post
One thing I noticed is you are basically making it a semi active 3 way, by crossing the SEOS design 24db/octave at 225hz ? What is the benefit of that versus running the SEOS down a bit farther?
There are several reasons. Higher power handling. Phase issues. The floor bounce. The fact that I'm trying to apply this to multiple designs. This is meant for someone who isn't comfortable with the details and wants a straight forward solution to upgrading their DIYsoundgroup speakers.

The 2226 is a nice woofer. It'll dig deeper to. But considering the cost and size I wouldn't use it for this app. Once I've put more time in with them, maybe I'll change my mind. But you can buy a ftr-3070c for the cost of a recone... The boxes I built for the 2226 are also much bigger. About 22x17.5x22 (wxhxd). So unless someone is trying to upgrade their Fusion 15 I think the size is off putting.

Don't worry, a 12" has plenty of output. People often don't understand that lack of midbass is usually a suckout/null from their room response. This solves that problem. So it's not so much about adding firepower to the speaker as it is solving the acoustics problems. Once that's solved, a 10" is probably more than most people need in a home. Speaker of which, the Dayton PA255-8 will likely be added to the list once I've refined it's box a bit.
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post #12 of 259 Old 03-24-2015, 01:29 PM
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Quote:
Originally Posted by tuxedocivic View Post
2. The ability and materials to build a ported cube.
This might help, if it's tall enough.
http://www.parts-express.com/knock-d...inet--300-7085

Did you really need to quote that entire post in your reply?
Welcome to AVS - Get out while you still can!
Don't guess, measure: https://www.avsforum.com/forum/91-au...l#post22789786
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post #13 of 259 Old 03-24-2015, 01:48 PM - Thread Starter
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That looks like a good product It's a hair small but could work for someone who can't build. Just a little less port output due to the size.
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post #14 of 259 Old 03-24-2015, 04:04 PM
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Since this is the DIYSG section it only seems fair to direct people to the DIYSG flatpacks instead of the PE flatpacks.

http://www.diysoundgroup.com/sealed-...flatpacks.html
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post #15 of 259 Old 03-24-2015, 05:23 PM - Thread Starter
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Thanks. I think they're both from DIYsoundgroup ground but Erich would have to confirm. I was going to ask Eeich the cut out sizes of this one: http://www.diysoundgroup.com/sealed-...flat-pack.html and use it as the basis for the instructions in this thread if it works. I haven't emailed him yet but I think it might be to big.
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post #16 of 259 Old 03-25-2015, 11:43 AM
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Tux, Do the MBMs need to sit directly under the speaker to work? For example, my Alchemy towers are 56" tall with the WG at ear level... so could they be placed to the side?
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post #17 of 259 Old 03-25-2015, 05:49 PM - Thread Starter
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They need to be on the floor but beside is fine. I'll doublt check the horizontal lobing though. For the MTM a 150ish hz XO might be better. I'll look into it.
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post #18 of 259 Old 03-26-2015, 06:17 AM
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Ryan, the MBM can be placed on floor only? I have an idea of adding two MBMs to each of my Tempest, one on top while another on bottom
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post #19 of 259 Old 03-26-2015, 07:27 AM - Thread Starter
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You could certainly experiment with that if using two, or put both on the floor.

If using a single, the recommendations I'm posting here are designed to take advantage of floor loading.
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post #20 of 259 Old 03-27-2015, 12:17 PM
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Tux, I can model later when I get home to see what it looks like, but if I have around 1.7cu ft to play with, would you still recommend using this woofer or are their any others that would model better in a little bit larger enclosure? Thinking about building some MBM's 22" high to match better with an AV Console.
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post #21 of 259 Old 03-27-2015, 03:22 PM - Thread Starter
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Hi Matt,

22" tall would be no problem. I'd maybe flip it so the ports are up and the woofer is down. You want to couple the woofer to the floor up to at least 350hz. So that would be how to accomplish that. Alternatively you could lower the XO to about 175hz.

I tried this woofer in about 1.7cu ft and it worked very well but did move up the tuning and also causes a bit more excursion. All in all it can work exactly the same way. There are many options for MBM woofers that I haven't used, so if you have something you'd prefer to use I'm sure it would work fine.
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post #22 of 259 Old 03-28-2015, 06:31 PM
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Do you think the Eminence Alpha 12A could work? It looks smooth up to 250ish hz.
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post #23 of 259 Old 03-28-2015, 07:51 PM - Thread Starter
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Unfortunately not to well as it requires a large box. You could hammer it into shape with eq, but power handling is to low to really smack it around to much.
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post #24 of 259 Old 03-30-2015, 10:46 AM - Thread Starter
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Quote:
Originally Posted by Mfusick View Post
JBL 2226 woofers might make a good midbass module.
The more I thought about it's sealed capability while working with it, I decided to add it. It's still not what I would recommend for most people, but I already have the data and details, so someone can give it a whirl if they'd like. The sealed box I used is bigger than needed likely, but still requires a large box.
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post #25 of 259 Old 03-30-2015, 11:35 AM
 
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Quote:
Originally Posted by tuxedocivic View Post
The more I thought about it's sealed capability while working with it, I decided to add it. It's still not what I would recommend for most people, but I already have the data and details, so someone can give it a whirl if they'd like. The sealed box I used is bigger than needed likely, but still requires a large box.
I was going to suggest this earlier, my sealed boxes are not too large.











Just be careful of the JBL postive negative confusion- they do that different. Test it.
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post #26 of 259 Old 03-30-2015, 11:43 AM - Thread Starter
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Quote:
Originally Posted by Mfusick View Post
I was going to suggest this earlier, my sealed boxes are not too large.
Ya, the problem I found with the smaller box is it starts rolling off pretty steep by 80hz. So the bigger box will help it get down to 40hz usably. And someone could port it for 40hz if they weren't interested in the sealed benefits. Either way, it's superb, just expensive and large.
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post #27 of 259 Old 03-31-2015, 11:53 AM
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Are there any other 18" contenders you would recommend for a small sealed box?
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post #28 of 259 Old 03-31-2015, 01:50 PM
 
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Quote:
Originally Posted by tuxedocivic View Post
Ya, the problem I found with the smaller box is it starts rolling off pretty steep by 80hz. So the bigger box will help it get down to 40hz usably. And someone could port it for 40hz if they weren't interested in the sealed benefits. Either way, it's superb, just expensive and large.
Interesting you mention this because to me 40hz and below is BASS. That upper region above 40hz all the way up to say 200hz I consider "mid bass" but I don't think I ever got a complete definition of "mid bass" before. I kind of just assumed what it was, but who knows I could be totally wrong about it. So I guess this is as good a thread to ask- What is midbass specifically?

When I see midbass modules, or I think of their application I kind of think of a woofer positioned above the subwoofer system and below the midrange or full range solution to fill in the gap between those two areas. Midbass can be directional or at least start to be able to be localized as you start to get into the higher frequency so I always kind of assumed a MBM was always positioned near a full range or the LCR speakers to maintain the idea the sound if coming from where it should be.

I also usually more consider the 80hz-200hz range midbass, with 40hz being more of the normal or low "bass". In fact 40hz is the meat of the musical bass band IMO, where the low bass guitar notes and kick drums hit hard. I'm not sure if I am right about this though ???

I am of the belief of a few things that predominately dictate my approach to set up of subs/LCR/MBM:

- The best place for a subwoofer isn't always the best for your LCR speakers
- A crossover point should never be determined by the capability of your speakers (I.E monster mains and cross low)
- Crossover should be based on the room, and not arbitrarily 80hz everytime.

Therefore I am not sure a MBM needs to dig down to 40hz. I mean it's great it you can port a 2226 and get there with a huge box and make it fit, but probably you don't even need to do it, or should even do it. LCR and MBM's don't need to get to 40hz. They should only need to get to whatever crossover you use for your subwoofer solution- and that should be based on the room.

For example: If you have a null at 85hz, you probably don't want to just arbitrarily cross at 80hz, but rather set the crossover to achieve a nice response. Or- If you have a big peak at 70hz, you might want to cross just before that to help minimize the problem. Balancing the MBM or LCR hand off to the subs is usually determined by the room and I can't think of many times it's going to be near 40hz (this is too low). So all things considered I am not sure the problem is all that big in reality, I would suspect a small sealed box that starts rolling off and doesn't get to 40hz with "flat" response is probably ok for ~90% of the rooms most people put home theaters in.
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post #29 of 259 Old 03-31-2015, 02:20 PM - Thread Starter
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Are there any other 18" contenders you would recommend for a small sealed box?
None that I've used personally. If you really wanted to go that route I could give a recommendation based on simulations and general awareness. Let me know if you do.

Most of my thoughts have leaned towards a cost effective approach and smallish size. If a driver isn't playing above 300hz it doesn't need to be fancy to work well.
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Therefore I am not sure a MBM needs to dig down to 40hz. I mean it's great it you can port a 2226 and get there with a huge box and make it fit, but probably you don't even need to do it, or should even do it. LCR and MBM's don't need to get to 40hz. They should only need to get to whatever crossover you use for your subwoofer solution- and that should be based on the room.

For example: If you have a null at 85hz, you probably don't want to just arbitrarily cross at 80hz, but rather set the crossover to achieve a nice response. Or- If you have a big peak at 70hz, you might want to cross just before that to help minimize the problem. Balancing the MBM or LCR hand off to the subs is usually determined by the room and I can't think of many times it's going to be near 40hz (this is too low). So all things considered I am not sure the problem is all that big in reality, I would suspect a small sealed box that starts rolling off and doesn't get to 40hz with "flat" response is probably ok for ~90% of the rooms most people put home theaters in.
The 40hz things isn't to cross at 40hz. Notice on the graph 40hz is about 10db down. What if someones room dictates a 60hz XO and the sub were 18db down at 40hz. It's less likely to work well as a 60hz XO. And if running them full range, the larger box will help. I'm offering solutions that are broad and work for anybody. If your room requires a 100hz XO then you probably don't need a 15" MBM, a 10" would be sufficient. Also consider that adding an MBM will help with room acoustics in the dreaded 80 to 100hz region and allow for a lower XO. If a lower sub cross over works, then I would use it if all else equal and if using a capable MBM (lots of "ifs" there).

The JBL 2226 is a great driver, but not MBM friendly. Personally, the way kingpin is using it is IMO the best application for it. 60-600hz, massive output, no concern for size or price. But hey, I solid measurement of yours in your box would be welcome and appreciated.
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