Midbass Quandary - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 19 Old 04-04-2020, 10:45 AM - Thread Starter
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Midbass Quandary

I have four 18" subs in an IB line array. Each drivers sensitivity is 89dB so the combined sensitivity is 95dB. Each driver only gets 350 watts so I'm looking at a peak output of around 126dB before room gain is considered. My theater is in open loft so there is very little room gain. The IB subs of course cover the ULF quite well. I also have 4 sealed Infinity Reference 1262's as NFS. But, midbass is not quite what I want. I'm looking for a clean, efficient, low distortion midbass option to complement the sealed IB and NFS subs. I was looking at getting a pair of VBSS subs, or Erich's 15" MBM at DIYYSG, but it just so happens that vertically oriented 15" MBM Devs would fit perfectly between my HTM-12 LCRs. Another option is to get 21" MBMs and put them in the attic with the openings firing into the room through a hole in the ceiling.

So,

1) Would a pair of MBM Devs work well if they covered the midbass between my sealed subs (IB sub and NFS) and my ported LCR (HTM-12's)?

2) If the answer to 1) was yes, would you get the 21" or 15" MBM Devs? Please keep in mind the output capability of my current gear and that going with the 15" MBM Devs would be easier since the enclosure would be in the room (vs the 21" MBM Dev being in the attic).

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post #2 of 19 Old 04-04-2020, 10:59 AM
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Damn, 15 channels of surround sound!

I personally would replace the NF with something more capable. A pair of some model of Dev should do the trick. You could repurpose the JBLs into a BOSS system.
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post #3 of 19 Old 04-04-2020, 11:20 AM
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Almost the same setup I have. I have 2 fi IB18 and 2 adire tempest in an infinite baffle setup. Looking to do the same. I have limited space and was deciding between the 15" mbm devastator, slim vbss or the dual 12" devastator. Been going back and forth.
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post #4 of 19 Old 04-04-2020, 02:02 PM - Thread Starter
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Originally Posted by Samps View Post
Damn, 15 channels of surround sound!



I personally would replace the NF with something more capable. A pair of some model of Dev should do the trick. You could repurpose the JBLs into a BOSS system.
I doubt I'll get rid of the NFS. I like them, and they work. I think I'm looking for more impact from the front to balance the feel of the NFS from the back. I don't have all 15 channels running right now as my receiver is still an ancient Denon 4311. I'm using Audyssey DSX until I get a 16 channel pre-pro. I'm waiting for DIRAC to be released for the Emotiva pre-pros before I decide which way to go. Hopefully the bugs will be minimal but I've learned to take a wait and see attitude with them. I plan to work with the MiniDSP 2x4 Balanced and crossover points for the subs before taking the plunge on the MBMs. Of course being able to dial in a house curve with DIRAC should help (especially when compared to the my old version of Audyssey XT 32). I'm leaning towards the getting two of the 15" MBM. If I get them I'm guessing I'll set the high pass on the HTM-12 at 120Hz and the high pass on the MBM at 60Hz. That seems natural since that's where the 15" MBM drop off and that coincides with the low pass of the LFE channel and also limits the IB to it's best frequencies.

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post #5 of 19 Old 04-04-2020, 02:03 PM - Thread Starter
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Originally Posted by rykerjen View Post
Almost the same setup I have. I have 2 fi IB18 and 2 adire tempest in an infinite baffle setup. Looking to do the same. I have limited space and was deciding between the 15" mbm devastator, slim vbss or the dual 12" devastator. Been going back and forth.
What do you have for your LCR?

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post #6 of 19 Old 04-04-2020, 03:10 PM
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Originally Posted by krholmberg View Post
I have four 18" subs in an IB line array. Each drivers sensitivity is 89dB so the combined sensitivity is 95dB. Each driver only gets 350 watts so I'm looking at a peak output of around 126dB before room gain is considered. My theater is in open loft so there is very little room gain. The IB subs of course cover the ULF quite well. I also have 4 sealed Infinity Reference 1262's as NFS. But, midbass is not quite what I want. I'm looking for a clean, efficient, low distortion midbass option to complement the sealed IB and NFS subs. I was looking at getting a pair of VBSS subs, or Erich's 15" MBM at DIYYSG, but it just so happens that vertically oriented 15" MBM Devs would fit perfectly between my HTM-12 LCRs. Another option is to get 21" MBMs and put them in the attic with the openings firing into the room through a hole in the ceiling.

So,

1) Would a pair of MBM Devs work well if they covered the midbass between my sealed subs (IB sub and NFS) and my ported LCR (HTM-12's)?

2) If the answer to 1) was yes, would you get the 21" or 15" MBM Devs? Please keep in mind the output capability of my current gear and that going with the 15" MBM Devs would be easier since the enclosure would be in the room (vs the 21" MBM Dev being in the attic).

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Awesome looking room man
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post #7 of 19 Old 04-05-2020, 09:13 AM
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Most bass is limited by cone area, driver efficiency and input power.

The biggest problem with IB, as you've probably noticed, is that they lack mid-bass... this is because IB and sealed pretty much play full-bandwidth, the power is divided across a larger range of frequencies, and hit their xmax quicker at lower powers. That's the price you pay for wanting flat to 1hz! (In more ways than one, 1hz ain't cheap!)

ULF is almost entirely cone-area/displacement limited.
Mid-bass is almost entirely power-limited.

If you have low-power into low-efficiency drivers spread too-thinly, you can see how this is a problem.

IMO every system needs both ULF and MBM subs. The driver attributes that lend to good ULF don't make for good MBM subs and vice-versa.

One of the many reasons I chose to buy 16 PA-460's was that not only is it 16 x 18 worth of cone-area but also 8kW RMS/16kW burst at 99db/w/m x 16. Not only that, it only cost me like $1400 (ignoring amplification). An FP20k is perfect for driving 16 of those at quad 2-ohms.

You need lots of coil-area to keep things cool too. Pushing 8kW into a pair of 21's is possible... if you want them to reach the same temperature as the surface of the sun! (I smell coil!/Burnt slinky! )

153db @ 1m @ 8kW
I put them in undersized opposed sealed boxes, you can barely even see them, they hide well.

If I didn't point it out you probably won't even have noticed them behind my fronts.


It's more mid-bass than I could ever use. It can kill small animals from a distance. It is so overkill that it just sounds "dumb" if you actually crank them to their full potential, the SEOS's can't keep up and neither can the ULF subs. Even with 100kW going to them. All while producing no audible cone noise. Bass for days without overheating or bottoming. A basshead's gotta do what a basshead's gotta do! Problem SOLVED!!!
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post #8 of 19 Old 04-05-2020, 10:24 AM
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It seems to me the more I read here about tuning real low the more that the people come back here asking for more midbass, hmm?

Anyways, I have two pa460 narrow Devs and they are midbass monsters more than any other VBSS I’ve ever built. I was going to upgrade drivers but I love the sonic signature of them for midbass alone (in the Dev) and they blend well with my BOSS setup. Yes, they play to 20hz but if you cut them at 40-50hz they would more than satisfy IF THEY FIT. Most mini Devs would probably do you good, just look through the index for a size that would fit and make sure it is not tuned low.

Or just go with the 15”MBMs, one for each htm. This would be a better long term goal for me to do (make the HTMs three way), oh wait I did that already too.

Both would do you great, not sure I would do anything less after building / hearing / knowing all the other directions you listed..... Except more 21s, but then I would run them from 16-120hz with a BOSS.
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post #9 of 19 Old 04-05-2020, 10:35 AM - Thread Starter
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@BassThatHz So for midbass you were able to keep the cabs sealed (dual opposed) yet gain what you were missing. The idea of spreading the workload over a large number of drivers to minimize the stress on each driver and in turn decrease distortion is the same reason I have 4 relatively large high excursion IB drivers as opposed to the pair I used to have. Of course a side benefit of sealed dual opposed enclosures is they are rather easy to build . From a phase integration stand point keeping everything sealed would make things much easier, too.

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post #10 of 19 Old 04-06-2020, 07:33 PM
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There is no free lunch.

Power causes heat and excursion, and both of those cause distortion (unless you can spread it out.)
All 3 of those are your enemy. A necessary evil at-best.
Cone-area, coil-area, and driver sensitivity are your friend.

This of course, results in a WAF of 0%, but such is life.

I mean, alternatively you could just keep adding more IB drivers until you have so much headroom that you can't use it all. That works too, it's just an inefficient way to get there due to the things I already described.

Alternatively again, you could bump up your mid-bass via EQ, but that will cause your driver heat to increase and eat into your amplifier headroom.

You could buy 4 pro 21's and port them or 6th order them etc, for more money than I paid for my array, and still have less mid-bass than me. LOL!
I don't even run a HPF on my MBM's, they are exposed to single digits, that's how much headroom I have. They barely ever go above 1mm excursion.
By 2mm's... your skull is caving in as 147db is flying out of the cones by that point. (Yes... You read that correctly!)
It can sustain 147db all-day-long (from just those 2 boxes.)

You can hear the mid-bass pulses at 1:48
It's fully clipping my GoPro, 0dbFS. (and that's at only 5% output power too...)
That's only 15mm of 80mm's on the LMS's (and even less excursion on my 21's and 24's)
It goes louder...

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post #11 of 19 Old 04-07-2020, 06:06 AM
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Nice looking room! What drivers are those in your subs?

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post #12 of 19 Old 04-07-2020, 03:30 PM - Thread Starter
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Nice looking room! What drivers are those in your subs?
The quad 18" array uses gen 1 FiCar Audio IB3 18 S2 drivers. The space behind it is open to the attic and the opening happens to be equal to the combined SD of the drivers so they are in an infinite baffle alignment. They only need 350 watts to get 30mm one way excursion with sub 15Hz material. As noted above, they are great for the ultra low frequencies, but not at all at midbass. I also have a quad 12" array for NFS (at the bottom of the pic). They are Infinity Reference 1262 drivers and each is in a 2sqft sealed enclosure.

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post #13 of 19 Old 04-07-2020, 03:34 PM
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Quote:
Originally Posted by krholmberg View Post
2) If the answer to 1) was yes, would you get the 21" or 15" MBM Devs?
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The quad 18" array uses gen 1 FiCar Audio IB3 18 S2 drivers. The space behind it is open to the attic and the opening happens to be equal to the combined SD of the drivers so they are in an infinite baffle alignment. They only need 350 watts to get 30mm one way excursion with sub 15Hz material. As noted above, they are great for the ultra low frequencies, but not at all at midbass. I also have a quad 12" array for NFS (at the bottom of the pic). They are Infinity Reference 1262 drivers and each is in a 2sqft sealed enclosure.

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If you can fit an enclosure for a 21" driver, then that would be my suggestion.

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post #14 of 19 Old 04-07-2020, 04:29 PM - Thread Starter
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If you can fit an enclosure for a 21" driver, then that would be my suggestion.
The only way to do that would be to assemble it in the attic and have the vents fire thru an opening in the ceiling. That would be doable but a pain. If I do dual 15" MBM Devs, they could be in the room (one between the L and C and the other between the C and R) and fire directly at the people in the room. I also like the dual 15" Devs because I could move them somewhere else if I want to. If I build a 21" Dev enclosure in the attic it isn't going anywhere!

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post #15 of 19 Old 04-07-2020, 05:09 PM
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Originally Posted by krholmberg View Post
The only way to do that would be to assemble it in the attic and have the vents fire thru an opening in the ceiling. That would be doable but a pain. If I do dual 15" MBM Devs, they could be in the room (one between the L and C and the other between the C and R) and fire directly at the people in the room. I also like the dual 15" Devs because I could move them somewhere else if I want to. If I build a 21" Dev enclosure in the attic it isn't going anywhere!

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Ok, I see what you're saying. Which 15" do you have in mind?

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post #16 of 19 Old 04-07-2020, 06:52 PM - Thread Starter
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Ok, I see what you're saying. Which 15" do you have in mind?
Probably the LaVoce WAF154.00. From what I've read it seems to have better impact than the B&C 15TBW100-4. I was thinking about 15" speakers offered by Erich at DIYSG but less seems to be known about them. Interestingly the LaVoce is only 8 Ohms but it's 3dB more sensitive so that makes those T/A parameters moot. For me the LaVoce makes more sense because I'd like to wire them parallel.

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post #17 of 19 Old 04-07-2020, 06:57 PM
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Probably the LaVoce WAF154.00. From what I've read it seems to have better impact than the B&C 15TBW100-4. I was thinking about 15" speakers offered by Erich at DIYSG but less seems to be known about them.


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I think that would be a great choice of driver. I believe that is the same driver that JK.7 uses in his mbm.
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post #18 of 19 Old 04-07-2020, 06:57 PM
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If you haven’t, check out my thread on dual devastator micro build and setup. They did more then I could’ve imagined. For just being a couple 15’s, they added midbass I was only dreaming about. I had SI hst18’s ported, and those didn’t provide midbass for all the reasons already explained in this thread. The mbm devs added all I was missing and more. And this is also with Titan 630 mains. I suggest you build the devastator micros. You’ll love them.
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post #19 of 19 Old 04-07-2020, 09:37 PM
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Hopefully dual 15's will be enough SPL for you, at some point we all run out of space/money/will power/WAF, and hopefully by that point the SPL is sufficient.
You can only do so much... at some point the SPL just is what it is.

>30hz is fairly easy to cure relatively-speaking.
Single-digits there is never enough bass, no matter how many woofers you throw at it...

If I throw my 21's in the garbage, and abort the HzHorn idea completely, move the sealed LMS-18's to the back; then I'd have enough room for 10 24's up front. That would definitely make my room louder.
I think I'll do just that... [Dude I'm so getting SWAT'ed, like a WH email server. Pitchforks and everything! ]
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