Would a Rythmik still benefit from an MBM?

[monomer]

I currently use Reference Infinity mains that can actually reach down to 27Hz (in-room response) and have an "original" VTF-2 (in 25Hz tune mode) with the 180-watt Class A/B amp and light-mass 10" woofer crossed at 50Hz over to a sealed MBM-12 that's crossed (@ reciever) at 80Hz. Both these subs are co-located and the blend is absolutely seamless. REW shows a relatively flat in-room response down to 21Hz and the bass sounds quick and tight and 'real'. I'm really happy with it currently yet I'm contemplating purchasing a Rythmik 12 (to replace the VTF) to get more extension but I don't want to lose any of the tightness in the mid-bass region or upset that seemless blend. Does anyone have any thoughts on this? Will I need to ditch the MBM? and maybe cross-over higher? keep the MBM and do a direct replacement with the VTF-2? SQ is everything, I don't care about flapping pant legs or vibrating my butt or getting slammed in the chest... I just want it to sound 'real'... so, which will sound better in the critical 50-80Hz region? My Infinities sound great in that region (better than the MBM even) but I really want to unburden the 10" IMG woofers in them to allow the best reproduction in the 80-200Hz range without interference from the lower freqs... and use the 350-watt MBM to bring those mid-bass freqs 'forward'. How will things change with a Rythmik 12? Thoughts?

[curtis]

In terms of headroom and output, the system would probably benefit with the sealed MBM-12(sealed and tweaked by Hsu?), but for sound quality am not so sure.

It would definitely be interesting to compare.

[vantagesc]

Nothing much to add to Curtis's thoughts.

Things shouldn't really change for you. I don't see why you couldn't use the Rythmik as a drop in replacement for the VTF-2. You should be able to achieve the same type of blend with the MBM and Rythmik that you enjoy with your MBM and VTF-2. Also, you have the luxury of being able to try things without the MBM at all, since you seem to indicate that the Infinity produces better mid-bass quality than the MBM. You could try crossing over the Infinities to the Rythmik at 50hz as well.

[TooManyHobbies]

This reply is based on using a pair of Rythmik F15's co-located with my Dayton Audio UA721 MTM main speakers and crossed over at 80 Hz. The reason for the MBM unit in the Hsu line is that while ported designs can provide lots of low bass output in a relatively small box, the tuning needed to accomplish that can detract from accurate mid-bass. The MBM fills in a tuning "hole" and smooths the response. Rythmik subs do not suffer from tuning anomalies, so do not need any help accurately reproducing the entire bass region. My F15's are superb with music. This is particularly noted with percussion (large drums of various types) and bass guitar where the sounds are known to be in the frequency range of interest. The lowest notes of piano and synthesizer are equally impressive, although without disconnecting my mains it's not readily apparent which speakers are producing which tones. I can not imagine an MBM would provide any improvement. However, since you have one already, it certainly wouldn't hurt to try it with your Rythmik sub and satisfy for yourself whether there's anything to be gained by using the MBM.

Bill

[monomer]

All very interesting comments. Its funny but whenever anyone asks a question often without realizing it they are actually expecting a certain answer in response to the question. In my case I guess I was hoping someone who would read my posting might have actually had some experience with an MBM and therefore had first-hand knowledge of its capabilities in relation to a Rythmik. It appears the MBM is still a rare animal in subwoofer circles. So I guess I must be the first here to compare and contrast a Rythmik in the mid-bass region (my definition: 50-80Hz) to the MBM. Yes, it is a HSU modified sealed MBM12 and suppose to be the very last one they had... at the time it was being used for benchmarking I believe.

Since I intend to use my Onkyo for the bass management and the HSU its replacing is only a 10" and a 180-watter, I assumed the standard 300-watt amp should suffice. Since Ascend doesn't seem to offer Rythmik subs with the standard amp option I had to go directly to the Rythmik site. After conversing with Brian my thoughts were to get the F15 but unfortunately they are out of stock in Black Oak until second week in August. In this particular instance, time is an important factor for me (I'm scheduled for an impending operation early August) so I went with the F12 as originally planned. When it gets here I will try all combinations to see what works best for my situation.

Anyway, thanks to all for your thoughts in this thread. Appreciated it.

[curtis]

I have heard the MBM-12 on a few occasions, but have not compared it to my Rythmik.

[vantagesc]

I was just curious why you are still going to run the MBM if you feel the Infinity speakers sound better in that region anyway? Headroom? Impact?

[Gov]

In my opinion, if you have a very capable subwoofer (Rythmik is I am sure) that has good mid bass slam AND is enough subwoofer for your room, there is no need for the MBM

[monomer]

I was just curious why you are still going to run the MBM if you feel the Infinity speakers sound better in that region anyway? Headroom? Impact?

A good question which I actually tried to address earlier. The Infinities are a 4-way speaker design with the 10" woofer crossed-over at 200Hz... this would then have that one speaker handling all freqs from 200Hz down to the 27Hz in-room response. I believe that if a speaker cone is having to move to reproduce a 30Hz tone then that large cone movement must be affecting its ability to simultaneously reproduce say a 100Hz or even a 200Hz tone cleanly. If I were to unburden that woofer of having to reproduce the most worrysome freqs that require the most cone excursion (those freqs below 80Hz) that would allow it to dedicate its cone movements to accurately reproducing the 80-200Hz range with less distortion and thus more accuracy. However, just recently I tried dialing down the subwoofer channel by 3dBs and turned on the 'Double Bass' feature on my Onkyo, where both Infinities and sub(s) are fed the same bass signal (sans the LFE), and it has improved bass response without a doubt... so maybe my Infinities don't really need the MBM. One thing that I do like about the MBM is the 350-watt amp... it provides more headroom for the Onkyo and allows me to bring the mid-bass 50-80Hz freq range 'forward'.

[monomer]

In my opinion, if you have a very capable subwoofer (Rythmik is I am sure) that has good mid bass slam AND is enough subwoofer for your room, there is no need for the MBM

This is what I need to find out. I don't really care about 'mid-bass slam', what I'm after is 'mid-bass accuracy'. My past experiences have only been with conventional ported subs and my subjective impression has been that subs capable of ultra-low freq at high SPLs and acceptable distortion levels typically do not sound very accurate and tight when reproducing mid-bass freqs. It appears to be a trade-off made in driver materials and construction that allows very large cone excursions without physically distorting at the expense of light, quick and accurate response during the small excursions. An example might be the GR paper cone option for the Rythmik F12... its lighter construction reportedly makes its response more nuanced for the higher freqs but less capable of resisting cone distortion at the lower freqs at high SPLs. The main reason HSU created the MBM was to use a lighter paper cone driver that didn't require large excursion capability (since the speaker design is meant to roll-off at 50Hz) and thus it could use smaller, lighter and more flexible surrounds, this makes it more nimble at reproducing the mid-bass freqs... in contrast to the type drivers employed in most true subwoofers. Seems most people missed that part about the MBM's driver advantage and only focused on Dr HSU's suggested near-field application for the ported MBM, which is why simply placing any uber-subwoofer near-field doesn't really get you the same type of mid-bass response as actually using an MBM... plus you have now introduced the possibility for time delay alignment issues with the 'other' (true) sub. My sealed MBM is not, nor does it need to be, located near-field, which is one of the reasons why I have no phasing (time delay alignment) issues and is a major reason why the blend with the VTF is so smooth and transparent. I believe the reason my Infinities sound even 'better' (to be read as 'more nuanced') than the MBM is because the 10" IMG polypropylene cone woofers used are both smaller and lighter still than the 12" woofer used in the MBM... and the older surrounds appear to be both thinner and more flexible. I want accurate, tight, nuanced mid-bass response with deep extension capabilities from a sub... so, can a single sub do better than two dedicated subs, each tailored to best reproduce different ends of the bass freq range? (Not unlike the concept of a 3-way speaker arrangement sounding better than using a single full-range driver.) Maybe a sealed sub doesn't have these issues?... maybe its not an issue with a direct-servo sub?... I don't know but I will very soon be able to judge these things for myself. I requested the sub (F12 w/ standard 300-watt amp) be delivered next Thursday and so I think I should know a lot more by next weekend.