Preliminary test of MBM

[derrickdj1]

Another forum member ask about mid bass that was lacking in what should be a stellar system.  I converted two of my 18 in. monster into MBM for an experiment.  The answer is still pending since the initial impression are bases of the film 12 Strong. All I can say is  Oh! I took the two sub from 15  Hz cut off to 50 Hz.  WOW, that is  a lot.   The nearfield subs (2) are punching like gutter trash trying to make their presents known.

 

I need further experimentation with some heavy hitter but, for right now the current configuration stan.  The movie is being watch a Reference level.   This also address another post active o n the forum on the need of an amp.  I am running the side and rear sound off my power amp.  The main are on the avr with the other speakers.  Power requirement are dictated by the weakest speakers  or surround in most cases.

 

I'm the only guy on the forum that does not recommend a power amp for the front 3 speakers.  Why waste the amp on the front 3,  when the surround require more true and stable power?  All I can say is this is great.  Don't take this as gospel but, many on the forum  know, I don't spouts off without some testing and research.  I truly only need 4 subs to control this size room.  Even though you   could store a body in the larger subs.

 

Right now the police are investigating a case and I need to go to the door.  I may be  back tomorrow.

[derrickdj1]

These speakers work well as MBM.  This is not even a big bass movie and it ' has great sound effects.  In my 4600 cu ft. room, I only really need four power subs.  I am going to play with adding MBM.  I could have 4 MBM and 4 subs going to 14 Hz..  I have many possibilities because of the sub.  If you are serious about HT, more subs mean much more than amps for the front 3 speakers!

[derrickdj1]

I'm on my second move, Pacific Rim #2.  With enough wooferage, I can't  imagine anyone putting up a speaker vs a  sub and claiming better sound! The second most important speaker in the HT setup is the subs, forget center channel and surround.  This is where the impact comes form, not the mains.  If you want good mains, switch to 2 ch.  I'm running 5.5 rear surround and 6.5 SS and 8 in Atmos and hitting spl of 127 db. at 0 db on the avr sitting 18 ft. from the mains and the reference sub is 28 ft. from the main listening position.  I wish I had a smaller upstairs room and not the basement.

 

I've now switch to some jazz.   Iam running 2 watts for 97 db average running the Mains full without subs at 18 ft away.  Wow, what is to be said about  speaker  efficiency.  I am only doing these post because some forum members believe that an avr can't deliver in recent post.  For those that want to refute the data, get another system that is not Klipsch!

[CECAA850]

So to convert from subs to MBM's you merely changed the cut off frequencies?  No driver changes?  Normally MBM's employ woofers as opposed to subwoofer drivers.

[JohnA]

I'm don't understand a thing Derrick said.  So first, what is an MBM?  mid bass? 

[CECAA850]

2 hours ago, JohnA said:

I'm don't understand a thing Derrick said.  So first, what is an MBM?  mid bass? 

Mid bass module.

[derrickdj1]

5 hours ago, CECAA850 said:

So to convert from subs to MBM's you merely changed the cut off frequencies?  No driver changes?  Normally MBM's employ woofers as opposed to subwoofer drivers.

MBM are normally constructed with a woofer and not a subwoofer.  The main difference between a woofer and subwoofer is their frequency range.  This was just a quick experiment that used my two closes subs.  I just moved the hpf up to 50 Hz and the XO on the HT to 100 Hz.  The goal of the experiment was to see if I would loose the tactile impact by setting the hpf to 50 Hz.

 

One of the things I noticed from testing on the ULF thread on the AVS forum, is that the UM 18's drop a bit in the 50-80 Hz range when running them for ULF.  By changing the hpf to 50 Hz takes a tremendous load off the driver. There was no loss of tactile response and things felt pretty good.

 

Further experimentation will be needed before more than a subjective impression.  This can be done with a smart phone.

[CECAA850]

If you want some mid bass slam, swap your 18's for a pair of these.

https://www.zzounds.com/item--PEVBW1801LT?siid=22096&-yEAQYASABEgIZIPD_BwE

[derrickdj1]

7 hours ago, CECAA850 said:

If you want some mid bass slam, swap your 18's for a pair of these.

https://www.zzounds.com/item--PEVBW1801LT?siid=22096&-yEAQYASABEgIZIPD_BwE

I am not looking to adding more speaker but, I have a couple of free channels open on the I Nuke amps.  I may consider adding a couple of MBM's since they can be run off one channel of the amp.  Replacing the one UM 18 as become quite expensive compared to when I first purchase them for $ 278.00.

[derrickdj1]

I should of define what a MBM (Mid Bass Module) is and who needs them.  A mid bass module will cover the frequency range of 50-250 Hz.  Why add a MBM?  For some small rooms, there will be a null in the frequency range of the MBM.  This is not correctable by EQ which is mainly used to bring down peaks and raise small dips.  MBM will provide more chest thump and club like music tactile response.  YYMV with employing a MBM so, they are not meant for everyone and may or may not be a good addition to a HT or music system.

 

MBM are usually made with a 12 woofer.  A subwoofer can be used but, cutting it off at 50 Hz  is giving up a lot of what it was made to handle in HT.  A MBM is placed different than most subs.  These modules are commonly used nearfield with a delay to be in synch with the subwoofers.  This is not a process done by ear and REW or Omni mic should be used or some other measuring system.

 

It should be noted that many systems with adequate subwooferage may lack the chest thump due to a lack of mid bass caused by SBIR(speaker boundary interference).  This SBIR can cause large dips or suckouts in some rooms.  This can cause destructive interference between direct and indirect sound waves in the room.  So, it is possible to have high spl at the MLP and miss the chest thump.  In an ideal world, one would place 4 subwoofers at the mid point on the 4 walls, followed by on sub in each of the 4 corners as a second choice.  I can't overemphasize that a truly  optimal HT will have subwoofer in the front and back of the room if the wall mid points are not available.

 

As a closing statement, we don't see many people on the forum complaining  about the 8000 to 25 kHz range where there are few audible modal problems. I don't get caught up on which speaker is better or what avr I should buy because  Klipsch has  many offerings and there are an abundance of  quality avrs.  Proper setup  is the key to making or breaking a system no matter what dollar amount has been spent.  You can't buy quality sound without understanding what is going on in the room!!!

[K5SS]

Gutter trash😂

 

Try the scene in the newest Rambo, when he gets into that truck with the machine gun mounted in the bed. That scene has some spectacular mid-bass!