interesting...I run taboo with vcap & hazen mod and old zen select with hazen mod..also use zen tube buffer plus Monarchy audio dip...one classic and other 24/96...I buy them used and find that they boost sound and increase base...with decware outboard dac and Lars audio equivalent I find that my sound is smoother and less digital (harsh).  It's a pretty cheap way to improve sound.I have a smaller listening room and listen mostly to jazz so these minor tweeks fit my listening environment well.

dla405j

Thanks DBC! I wrote a question to you over in the SUPERZEN AND Z-STAGE thread. You just answered all for me. Thanks again for your insight on this. I am going to try this module. I now have a room where I can stretch the legs of my Super Zen CKC to obtain more dynamics-not-just tone and texture that I have enjoyed over the years with the SE84CS and now CKC.  My Zu Union's in Sangria Red arrive next week!   -Stone

DBC, are you running two of the mid bass and one or two subs?

My imagination is tickled, I bet you have killer sound.

Thanks for the info. I can imagine it sounds really rich and deep. I know you enjoy the sound very much, and that is what counts.

DougK,

You ask a great question. I have to say going in to this (experimentation with the MBM) my past experience and preconceived notions on what I thought I knew about subwoofers was actually an impediment. After all if you know the world is flat then you are unlikely to set sail for the horizon.

A little background. My Klipsch RF-7 mains are full range speakers. I've been to the local Klipsch dealer and when they crank them up with 200 Solid State Watts per channel they can kick out the bass. Problem is you have to play them loud and your ears start to bleed from the Solid State highs after about 5 minutes.

Come home crank the RF-7's with my Super Zen 2 Watts per channel and the mids and highs are to die for at normal listening levels. But where's all the Bass ??  I can hear it but it's a little faint for my liking.  Well lets crank it up some more and I start to drive the Super Zen into clipping.

No problem, I've got the HSU ULS-15 (15 inch sealed sub) tucked into the front right corner of my listening room. Turn that baby on and set the crossover at 90 Hz (max crossover setting on this sub). Yuck, it's boomy. Darn I've got a room induced peak at around 70 HZ. Turn the sub volume down from 50% to 20% and no more Boom, in fact pretty much no more nothing.

OK lets set the crossover at 50 Hz and the volume back to 50%. That sounds really good with Black Sabbath, Nickle Back and other music with lots of low bass (hey lets start spinning some RAPP) not really. Does not do much for The Rolling Stones though ??? OK Lets move the sub to the Front Left Corner. Darn, I've got a peak around 45 Hz there.

OK let's move the sub more to the center of the room along the front wall. Not too bad. I have the sub volume at 50% and crossover set at 90 Hz (max). I'm listening at a comfortable level, Super Zen sounds good and the music has a little meat on it's bones, I like it. Lets see if there is more of that to be had, tweak the sub volume up to 55%. What happened  ?? That does not sound natural. OK, sub volume back to 50%. I like what I'm hearing but wish I could get some more of that. Another point, now that the sub is in the center of the front wall I don't have the really low 20 Hz extension on movies ??

OK, fast forward to today. Having used the MBM (mid bass module) for months now I can appreciate how much music material lies between 50 and 150 Hz (150 Hz max crossover setting on the MBM). I don't think it was a mistake that Dr. Hsu designed and optimized to MBM to accurately reproduce material in this range. If you read some of Dr. Hsu's material he states below 50 Hz you need a big heavy driver and above 50 Hz a smaller lighter driver is optimal.

My Theory: You have a sub reproducing low frequency up to 100 Hz as an example (assuming no room induced peaks, good luck on that). As you increase the the sub volume at some point your brain says there is a disconnect between everything below 100 Hz which is going up in volume and everything above 100 Hz which is not going up in volume because the mains are producing that portion.

As you increase the volume on the MBM the frequency range that Dr Hsu felt was important (50 to 150 Hz) increases across the board as opposed to my example above using a single subwoofer and the mains.

I have to admit I was sure there would be a conflict to deal with given that my mains go down to 40 Hz. Certainly the MBM and Mains reproducing the same frequency range was going to be a problem. Well I run the MBM crossover at 150 Hz (max) and there is no issue. Basically just keep increasing the MBM volume until you brain says that's not right. Back the MBM volume off just a tad and enjoy.

Now will a system with a single MBM benefit by introducing a good sub, well yes. For reference I would say 80% of the performance bang comes from the MBM. Add a good subwoofer and you can increase performance (Weight & Body) another 20%. I think this goes right back to the fact that most music material does not have a lot going on below 50 Hz.

Recap:

Best room location for a box to reproduce frequencies below 50 Hz is often not the best location for a box to reproduce frequencies above 50 Hz.

Best driver to reproduce frequencies below 50 Hz is not the best driver choice to reproduce frequencies above 50 Hz.

Listening using a single MBM as opposed to a single Subwoofer there is a whole lot more going on in the bass region above 50 Hz then below on most music material. Therefore IMHO using a single MBM has a more profound impact on the overall "WEIGHT & BODY"  of the overall presentation.

Dr. Hsu knew something I didn't when he decided to build a box optimized to reproduce frequencies between 50 and 150 Hz.

The new Super Zen heightens the performance of the MBM compared to my 12 year old stock Zen Select. Point being if your source or amp are a tad muddy on the low end that will be reproduced by the MBM.

Final Thought: Prior to receiving the Super Zen I had a tendency to tinker with the MBM module volume. With better more modern recordings it seemed I could run the volume a tad higher without the MBM calling attention to itself. Older material could get a tad muddy so I would tweak the volume down a tad. Since introducing the Super Zen I have not touched the MBM volume. I think this is due to the Super's improved low end clarity and separation.

My apologies for the long winded response. If anyone does manage to get this far then I hope it was of some help.

4krow,

I agree with your comment regarding simplicity. Take my system for example; without the subs it is pretty basic which is always good. Source, pre, amp, mains.

The intent of my original post was to suggest that if someone has a simple system and would like to add a noticeable amount of quality "Weight & Body" to the overall presentation that a single HSU Mid Bass Module is a simple and effective option based on my experience.

I wanted to comment on placement also. The MBM is not all that sensitive to placement. With one unit you would want it somewhere along the front wall center or slightly off center depending on what your arrangement allows. Corners are not the best choice since at these frequencies you may start to sense that most of the bass is coming from one side of the sound stage.

I was reviewing Steve's paper on "Insights About Subwoofers" the other day.  https://www.decware.com/paper01.htm

"The common application of a sub woofer is far from high fidelity because of two things: The user turns up the volume to a level greater than his speakers, and turns up the crossover frequency to 90, 120, even 150 cycles. He does this because he is waiting to hear the sub work, and that is what it takes to get it to draw attention to itself. In this application, the response of the speakers are altered by overlapping them with a thick veil of bass."

I agree with with Steve's observations. If a sub is crossed over at say 80 Hz, as you increase the sub volume at some point the brain recognizes a disconnect between the volume of Sub frequencies below 80 Hz and Mains frequencies above 80 Hz.

On the other hand if one tries to overcome this problem by setting the crossover at say 150 Hz a second problem arises. Subwoofers by their very nature are designed to play Low & Loud and in my experience sound crappy when you attempt to cross them over at higher frequencies.

The HSU Mid Bass Module seems to solve both problems in my system. A unit optimized to reproduce frequencies between 50 and 150 Hz with accuracy and authority. No sense of "overlapping the main speakers with a thick veil of bass". The MBM simply adds to the music rather than drawing attention to itself.

DougK

You asked the following question earlier:

[b]"Can you expand on this?  Any idea why a smaller sub would add more weight than the larger one?"[/b]

First thing, the HSU Mid Bass Module is not a subwoofer in the traditional sense. So to judge it's effectiveness as I have described based on it's size alone would be a BIG mistake.

Traditional subwoofers are designed and optimized to go low and loud. Generally that means bigger, heavier drivers and bigger enclosures as your question suggests. The sealed ULS-15 does a wonderful job of going low with accuracy.

On the other hand the Mid Bass Module does a wonderful job of doing what it was designed to do. Reinforce the 50 to 150 Hz range with accuracy. If you read some of Dr Hsu's explanations on the MBM he selected a light weight 12" driver and designed the enclosure specifically for the MBM application.

So the traditional Subwoofer and the Mid Bass Module are really two different animals. I will try to explain it this way. If you are primarily into music and want to reinforce the 85% of the bass material that lies between 50 and 150 Hz on most recordings then I have found the MBM to be very effective. If you are only interested in reinforcing the last 15% of the bass material that is below 50 Hz on most recordings then a subwoofer would be a better choice.

Sure, I have both and and they sound great together. I realize however not everyone will have that luxury. I have listened to both and IMHO it's not even close. If I had to choose between the two it would be the MBM.

If I recall correctly, the effect described of 'volume intensity relative to level', it has been supported by the Fletcher-Munson curves from the 1950's. I'm sure it is in our genes for a reason, but I still envy other animals' hearing.
The sub that I used to own was a Velodyne UDL-15. I found that it was a great enhancement with the right speakers. The idea that a speaker cone was in constant 'check' in reference to the music signal seemed to be as good as it gets. But, as I stated, matched with the right speakers was important so that the two could be as seamless as possible. Driver distortion is unbelievably high in the lower regions of frequency, making less of a note and more of a thud as a rule.

Yes, and I agree with you also. It is a very good idea, using a less traditional sub that doesn't deal so much with unneeded frequencies. Correct bass reproduction, as hard as it can be to get right, is well worth it. Still, we have all visited those who have systems that they are so proud of because it can rattle windows....hmmmm to each his own I guess.

I think the big problem is phase coherence at the roll-off points... Some speaker manufacturers addressed this in the past: notably Beovox 'phase link' speakers...

They inserted an extra driver that lives in the suck out point between the bass and mid units... And it is phased especially to make a smoother transition...

Quote:

"Beovox," now there's a name I haven't heard in a while in a serious audiophile discussion.

Thanks again DBC for your insight with the Hsu mid bass module. It is a more efficient paper cone & driver motor too (by design as you eluded too)....to keep up with my Union Driver.

Out in the room, just a few feet away from my Listening Chair....is where I will start for placement. Anyway, after some time with my new Zu Unions and then the mid bass module I will return with some observations & pics.   Party on Wayne - party on Garth.....-Stone of Tone

Stone,

Have your new Union's arrived already ??  If not when do you expect them ??

Union's did ship today and are scheduled for 2/18 delivery!

I find that to be a really good point.  Low volume leaves out some information.    
    On another related note, if I remember correctly, harmonics go both ways. So if there are harmonics from say a cello that reach beyond it's scale, then the obverse is true. And harmonics are weaker signal than the original.

Hi Lon,

Been meaning to post but been too busy listening or working. I've actually been getting up an hour early each morning just so I can listen for a bit. The Super Zen and Mid Bass Module combination have provided an audible window into what is really happening in the lower frequencies. This has allowed me to tweak the system some and actually hear the improvements.

Last week I changed to a different equipment rack I had on hand in an attempt to improve vibration control. In the process I found that my two sets of Decware 1/2 meter interconnects I had been using were a tad tight so I went to a couple 1 meter pair of pure silver interconnects I have had for a long time.

It was interesting, when I powered back up and started listening my first impression was the low end was just a tad thinner. After listening for a while it was apparent that the low end was not thinner but more accurate with more clarity. Kick drum and Bass Guitar notes for instance seemed to have more space between them. Less tendency to bleed together.

Now to your question. Per Steve Deckert's advice I use the speaker level connections so that the MBM is reproducing as close as it can the signature of the Super Zen amp. I'm actually using common Cat-5 computer network cable purchased from Lowe's. I know, does not sound very Hi-Tek but it sounds good. The cable has four twisted pair, each individual conductor is solid copper (not stranded). I always use bare wire speaker level connections at the amp, mains, and MBM. The solid copper conductors hold up better than the very fine stranded type.

I twisted two of the pair together for the POSITIVE and the other two pair for the NEGATIVE.  So basically I have one Cat-5 cable for the left channel and one Cat-5 cable for the right channel. I have a pair of MBM's so I run them in Stereo, left channel only to left MBM, right channel only to right MBM.

I have experimented with just one MBM where I run both speaker level channels into a single MBM and the single unit performs very well in my room. The MBM has speaker level input connectors for both left and right channels. It did seem when I switched back to dual MBM's (Stereo) that low end clarity was improved a bit but it was not a night and day difference. I have implemented a few other small system tweaks since then that might account for the difference at that time ??

I did have a small ground loop issue. I run dual MBM's and ULS-15 subs in stereo mode. So left channel for instance I run speaker level connection to the left sub and daisy chain to the left MBM. Seems the MBM's would interact with the sub it was mated to. I simply ran a Radio Shack test lead with alligator clips on each end from one of the steel toggle switches on the MBM to one of the toggle switches on the ULS-15 sub to give them a common ground.

I talked to Dr. Hsu about the ground loop. Basically they expect anyone not living in a cave these days will use the line level connection. I think they expect the ground on the line level interconnect to tie all the grounds back to the amp ??

After I got my Super Zen I could just barely hear a very low level hum with the MBM's turned ON. I had to be right up next to the mains to hear this. Not audible at the listening position or with the MBM's turned OFF. I tied the the ground jumpers installed between each MBM and sub back to the case of my surge protection device where everything is plugged into. Bam, everything was dead quiet and it made a noticeable improvement in low frequency playback. Again just seemed to be a little more separation and space between instruments on the low end.

It seems if you have any type of low level distortion from your source, pre or amp the MBM is going to make that audible. In my case that has been a good thing since I have been able to identify (hear) and address these things.

The biggest advantage of the MBM is that you achieve big, full, spacious, satisfying sound at low to moderate volumes. I've been trying for 20 years to achieve this type of sound in a listening room with subwoofers and have had limited luck at best. The MBM is not a subwoofer.

I've come to appreciate that subwoofers are more of a Sledge Hammer. They are designed to reproduce frequencies that you feel more than you hear. The MBM is more of Hammer, much more nimble, more subtle.

Thanks for that info! I think if I were to use these I'd use the line level inputs from the CSP2+ . . . I will even have one of those with an extra stereo out put which would work for two or one. I like the signature of the CSP2+ so much that thanks to Bill selling one here I bought another to use with my SACD player which doesn't sound quite as good just straight into the Torii Mk III. For me the ideal preamp is a CSP2+ with three or four inputs. . . .

Anyway, your experience is really informative and I have no doubt that you are enjoying excellent sound. I'm moving to a townhome in OHio soon and will have a few neighbors; I've been living in a house with some space between neighbors for twenty plus years. I may need to listen at lower volumes, and your experience shows these HSU units can be a big benefit.

Another thought: I really like the simplicity of the HSU products. None of the "Digital Signal Processing", "Servo Control", "Parametric Equalization" or any of that other CRAP that I have tried with only limited success at best.

Who would have Thunk It, simple amp, driver and enclosure that does exactly what they say it will do.

Pale Rider,

Thanks for turning me on to Paul McGowan's daily discussions over at PS Audio. I thought this kind of fit into the topic being discussed on this thread and should be shared:

http://www.pstracks.com/pauls-posts/loudness-button/9651/

Well put DBC, like you, I have been part of this Foum for 12 years with the purchase of my Zen Select SE84CS in May of 2001. I don't post that much either and I learn things from Poster's like Lon, whom I very much appreciate on this Forum.

Now, I'm learing from you. I am ordering a MBM soon as I finish this post! Furthermore, I have a pair of Klipsch RF 52 II coming on Monday from Crutchfield. $448.98 delivered....can't complain. I have bought them for my bedroom system. However, after a long breakin...I think they will make it in for an audition in the Listening Room System.

Anyway, back to the MBM....RF 52's come Monday and the MBM by the end of next week and I'll return with some early thoughts.

I will use the MBM-12 MK2 in my Listening Room System first...and then out with the Polk 1.2 bohemoths...then with the Bedroom System....burned in RF 52 II's down the road.

I will be purchasing just one (1) MBM...I do realize you have two. I will run 14 gauge wire to them from Super Zen CKC Speaker connections to Speaker connections of MBM....placing the MBM near me/Listening Chair.




Listening Room System (12 x 14 room):

Ipad2 with Apple LossLess/CD Error correction>Cambridge Audio iD100 Docking Station >Illuminati D-60/BNC>Audio Alchemy DTI-Pro32>Prophecy Cryo-Silver Reference i2s>Audio Alchemy DDE 3.0 w/remote wand>Kimber Select 1030>Decware SuperZen CKC Amp>Kimber Select 3033> Polk LS 90....Room Acoustically treated/Dedicated Room & Adcom ACE-515 AC Enhancer // Herbie's Halo's on all Tubes & 2.5lb Mapleshade Brass weight on top of CKC Transformer // XLO Pro Power Cord to SuperZen




2 Channel Home Theater (w/Polk SDA SRS 1.2 Speakers):
(DVD, Blu-ray disc, CD, Vinyl, HDTV & Sirius Sat Radio via Dish Network)

Panasonic Blu-ray>Kimber Hero IC>Rotel RA-1062/Pre-Amp>Kimber Timbre IC>Emotiva XPA-2/(300 watts per CH into 8 ohms)>Kimber 8TC Speaker Cable>Polk SDA SRS 1.2/(use SDA always)>Kimber PK10 Palladian Power Cord to Emotiva XPA-2

Dish Network/HD DVR with Kimber KCAG IC to Rotel RA-1062/Pre-Amp.....
Sharp 46' Aquos Quattron HDTV/extra thread of Yellow (2nd only to the Pioneer Kuro)

Pro-Ject Debut Carbon (Red Plinth) to Pro-Ject Phono Box II with Audio Quest Diamondback IC to Rotel RA-1062/Pre-Amp.....

Velodyne Subwoofer wired with Kimber 8TC out of Emotiva XPA-2
Soon to be replaced by: http://www.hsuresearch.com/products/vtf-15h.html .....(fall of 2013 purchase)




Bedroom System:
Pioneer DV-563A...Illuminati D-60...Cambridge Audio DacMagic...Kimber Silver Streak...Decware SE84CS (stock)...Zen Styx w/Silver plugs...Klipsch RF 52 II

Stone, I'm pretty sure you will love those Klipsch.  I gave my brother my old (1 yr. ) pair of rb81's to help out in his system.  I loved them...great bang for the buck and Crutchfield is a great co. to buy from.

JD

....have put  concrete slabs between speakers and floorboards,
yes,...more bass firmness....and a little more subtle detail...

Thanks DBC, phasing and localization would be an issue with the MBM close to me. I will start at 150 hz as you suggested, while working on placement.

It is going to be fun using the MBM in 3 different Systems, somewhere between the mains and trying nearfield positioning and variations of... .

might be a bonus Stone, I was just getting my front firers off the floorboards, nothing to do with subs...then I thought, a few slabs on top of a sub might...  :)
The MBM sounds interesting. When you dont use subs you think you have weight and body enough. Detail of mid lows and up from a unit (not sub) well you know, it`s allways interesting to find out what lies hidden and can be brought out without comprimise. Looking forward hearing of your trials, following DBC`s good low down on them.