Is a Hsu MBM 12 needed with Sierras and a Hsu VTF3.3?

Currently I have a 7.1 system connected to a Denon 3808 receiver. The speakers consist of Sierras for LCR and 170s for the 4 surrounds. My sub is a Hsu VTF 3.3. The crossover is set at 60 HZ for LCR, 80 HZ for the 170s, and 120 HZ for LFE soundtrack. My room is around 6000 CF.

The sub is positioned 12 feet from prime listening position and can not be moved closer. If I bought a MBM 12 it would be placed directly behind the main couch for the near field effect.

Hsu offers a mid base module for 50-80 HZ called MBM 12.

Does anyone have any experience with listening to the Sierras with a MBM 12 and another sub?

Will I notice a substantial difference in bass if I buy a MBM 12 and set the VTF 3.3 for 0-40HZ, MBM 12 at 50-80 HZ, and the remainder for the Ascends?

The MBM-12 is not a necessity for any of their subs.

Will you notice a difference? Yes, but only you can be the judge if you like it or not.

I am new to audio so forgive me if this doesn't make sense.

According to my Audyssey graphs from the auto setup for my Denon the Sierras are dropping off at the 80-100 Hz point by 15-20 dbs for the LR and 10 dbs for the center. My On Axis Freg Response charts shipped to me along with my speakers from Ascend also show a 15 db dropoff below 100 Hz.

My HZ/db graphs from Audyssey and from Ascend do not look similar to the ones shown on the Ascend page. The Sierra web page shows a straight line across all the way to 50 HZ. Am I comparing the wrong charts? Are the ones included with my Sierras supposed to look like the first graph on the measurements section of the Sierras webpage?

Did I get a dud pair of speakers?

It appears from the VTF3.3 that it has trouble at above 50 Hz.

From reading around on audio boards it appears it is optimal to have a level line across all HZs to replicate what the soundtrack was intended to be. By not having a MBM 12 am I missing sounds from the 50 HZ to 80 HZ spectrum?

I appreciate you replying to my initial post Curtis because I remember faintly that you have the same setup as me - 3 Sierras and 4 170s. I have also seen you post on the Hsu boards about trying out Hsu subs. I imagine you would be the best person to ask if you have auditioned the MBM 12 with Sierras and another Hsu sub? If space was not an issue for placing an additonal sub (ala MBM 12) would you suggest adding it. BTw I use my speakers for 75% HT and 25% music.

What you are describing are issues with your room, not the speakers or sub.

In my room, I have a huge dip at about 40hz. Not much you can do about it besides trying different positions.

In your case, an MBM-12 placed nearfield would probably help.

I would also double check the settings on your subwoofer. Make sure the crossover is set to "out". What is Audyssey setting the crossover to for the speakers?

Audyssey sets the crossover at 40 Hz. I then manually change it to 60 HZ for LCR, 80 HZ for surround and 120 for LFE soundtrack.

Am I reading too much into the audyssey and ascend supplied graphs?

Here is the chart provided with my Sierras. It is similar to the Audyssey charts supplied by my Denon. I don't think it is my room unless Ascend tests their speakers in a bad room also.

As you can see form the chart the dip begins around 110 HZ and drops by 10 dB at 50 HZ.

The chart does not show the bass response of the speaker. I believe the chart actually says it is accurate to 250hz (the one I have does).

To measure the actually full response of each speaker coming off the production line would take too much time.

If Audyssey measured it the same way, it would not set the crossover at 40hz...it would set it above 100hz.