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  #1  
Old April 15th, 2013, 7:05 AM
fidelis1970 fidelis1970 is offline
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5.2 (True and Mid-bass subwoofers) HT: Setup (and other...) Advice Please

I am planning buying this Spring 5.2 HT speakers consisting of 5.0 speakers + 2 Hsu subwoofers: the mid-bass and the VTF-15H. Three questions:

- Is getting these two subs an overkill..? (compared to only getting the VTF-15H)
- Is the level matching procedure described by Dr Hsu (http://hsuresearch.com/faq.html#1) the same when the subs are different (as in this case)?
- Will the Audyssey setup work with two different subs like this? I'm planning to buy the Denon AVR-4520 CI it has two sub outputs

Many thanks!!

Patrick
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  #2  
Old April 15th, 2013, 1:31 PM
Kevin_Hsu Kevin_Hsu is offline
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Hi Fidelis1970,

The MBM-12 is not really a subwoofer, even though it is placed under the subwoofer category on our site. It is a mid-bass module. As the name suggests, it handles the bass from 50 to upwards of 250hz (but you're probably just going to set the crossover for the speakers and sub to 80 hz). The mid-bass module gives you more freedom for placement so you can place the VTF-15H in an area where you get a nice deep bass response and you can place the MBM-12 where you may get the best mid bass response possible. You would set the crossover to about 50hz on the VTF-15H to get more separation between the two units. That's not to say that you can't run the crossover set to "out" on the VTF-15H to potentially give you a boost in the mid-bass as well. In many cases, we've seen that some of the best mid-bass response occurs when the subwoofer/mbm is placed nearfield and for deeper bass when the subwoofer is placed in the front corner. YMMV
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  #3  
Old April 15th, 2013, 1:46 PM
fidelis1970 fidelis1970 is offline
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Thanks Kevin. Your answer takes care of my first question, if you or someone else knows the answers to my questions 2 and 3 it would be great! thanks
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  #4  
Old April 15th, 2013, 3:55 PM
Kevin_Hsu Kevin_Hsu is offline
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Whoops did not answer your second and third questions.

2. Yes you should gain match. Play a 63 Hz tone (comes with the test cd), and measure 75 dB. Place the MBM in the same position and measure 75 dB at 63 hz.
*Note* Keep the mic and the subwoofer/mbm in the same position. Make sure the crossover is set to out on the VTF-15H.

3. Personally I would use a Y-splitter on the sub 1 or 2 outputs. Putting the MBM-12 on one output and the VTF-15H on the other, when Audyssey runs its calibration, it might try to boost the mbm-12 sub 50hz signal to attempt to get a more even response (which may cause it to bottom out). Versus, if you use a y-splitter, Audyssey may treat the mbm/vtf-15 combo as a singular source. By and large, when it boosts/cuts the mid-bass, it would affect the mbm, if it boosts/cuts the deeper bass, it would affect the VTF-15H. We always recommend to take measurements before you run audyssey so you can know what it's doing with your system.
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  #5  
Old April 15th, 2013, 7:57 PM
fidelis1970 fidelis1970 is offline
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ahh thank you! I also just read (this should have been my starting point...) the mid-bass manual. It refers to a "after-market time delay unit" :
If you wish to time align the MBM-12 MK2 with respect to the true subwoofer, you can get an after-market time delay unit to delay the signal to the MBM-12 MK2. Dial in 1 ms for each ft difference in distance between the MBM-12 MK2 and the true subwoofer. In this case, set the subwoofer distance parameter on the controller to the distance of the true subwoofer, not the MBM-12 MK2.
Is this really necessary..?? If so, would you care to recommend (or give examples of) any brand / model?

Thanks!!

Patrick
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  #6  
Old April 15th, 2013, 9:33 PM
SME SME is offline
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Hi Kevin,

Would it be better to level match them with the mic at the main listening position and the sub/mbm at their respective locations? Otherwise, I imagine the bass balance could be substantially off if one location provides more gain than the other.
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  #7  
Old April 15th, 2013, 10:13 PM
SME SME is offline
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Patrick,

Consider the distance between you and each subwoofer. Subtract the smaller distance from the larger distance. If this difference is large, you may want to consider a delay box. A delay box may be worth considering if the difference is more than 3 to 5 feet. The phase switch(es) can help mitigate some of the time alignment problems.

Sorry, I can't recommend a particular brand of delay box. In my own research, I did see a lot of devices designed to provide echo effects for electric guitars. Unfortunately, those devices typically don't work well for the very short delays needed to time align subs. If you can find a device that lets you dial a delay of between 1-25 ms with a precision of at least 1 ms, then you're in good shape.

One more thing to consider, depending on your room layout, is to go dual-drive VTF-15Hs. I've heard it said that the mid-bass sound from a 15H is nearly as good as an MBM. The key detail is to place the sub or MBM as close to you as possible. You can run the 15Hs in the same close+corner placements used for the MBM+15H pair and gain more deep bass headroom. Or, you can install both VTF-15Hs close to you. Two close placed VTF-15Hs can give excellent sound for multiple listeners. I personally have a VTF-15H on the left and a VTF3-MK4 on the right side of my sofa. Both are used as end tables. Some obvious downsides to getting 2 VTF-15s are the added cost and the size difference between the MBM and 15H.


Quote:
Originally Posted by fidelis1970 View Post
ahh thank you! I also just read (this should have been my starting point...) the mid-bass manual. It refers to a "after-market time delay unit" :
If you wish to time align the MBM-12 MK2 with respect to the true subwoofer, you can get an after-market time delay unit to delay the signal to the MBM-12 MK2. Dial in 1 ms for each ft difference in distance between the MBM-12 MK2 and the true subwoofer. In this case, set the subwoofer distance parameter on the controller to the distance of the true subwoofer, not the MBM-12 MK2.
Is this really necessary..?? If so, would you care to recommend (or give examples of) any brand / model?

Thanks!!

Patrick
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  #8  
Old April 16th, 2013, 10:18 AM
Kevin_Hsu Kevin_Hsu is offline
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Quote:
Originally Posted by SME View Post
Hi Kevin,

Would it be better to level match them with the mic at the main listening position and the sub/mbm at their respective locations? Otherwise, I imagine the bass balance could be substantially off if one location provides more gain than the other.

Hi SME,

You can try that as well. It may or may not be a good idea to level match in that way. It really depends on the room acoustics. If there is, for example, a major null in the 63hz range from the VTF-15H, that would potentially ruin the leveling for the MBM-12 and may cause the 15H to bottom out. You are correct that there may be more of a dB increase with the MBM-12 next to you, after gain matching. I don't think that the difference will be that major that you would notice it. To be perfectly honest with you, with the mbm-12/sub config, level matching vs gain matching is a pro/con situation.
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  #9  
Old April 16th, 2013, 2:15 PM
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JerryMeeker JerryMeeker is offline
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IMO, you would be far better off getting two matched subs rather than the MBM. Much easier to find the best placement for a balanced frequency response, easier to gain-match, and easier to apply EQ like Audyssey calibration.

If a MBM were such a good idea, why don't you see more serious audiophiles using one? Yet, you see many who have two or more subs, usually identical ones. Do the research.
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  #10  
Old April 16th, 2013, 3:08 PM
shadyJ shadyJ is offline
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Quote:
Originally Posted by JerryMeeker View Post
IMO, you would be far better off getting two matched subs rather than the MBM. Much easier to find the best placement for a balanced frequency response, easier to gain-match, and easier to apply EQ like Audyssey calibration.

If a MBM were such a good idea, why don't you see more serious audiophiles using one? Yet, you see many who have two or more subs, usually identical ones. Do the research.
The MBM is not a bad idea at all, and it has some real advantages over dual identical subs. For starters it is better for reducing nulls, because the subs can more easily be placed in optimized locations. Also, it increases headroom overall because by separating the frequency bands that the amplifiers have to deal with, more power can be devoted to a narrower spectrum of frequencies by drivers that deal with those frequencies more efficiently. If you are going to have two subs deal with the same frequencies yes, it is a good idea to have them be identical subs so they will not be limited by each other's weaknesses. However, when you have two different subs and have them play to their individual strengths rather than weaknesses, that is something else entirely, and is more efficient than simply having two identical subs share the load equally.
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  #11  
Old June 8th, 2013, 2:15 PM
RayK RayK is offline
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fidelis1970, you mentioned in this initial thread posting that you intended to acquire the 5.2 system this spring (2013). If you have, what can you report to us and how did you implement the thread suggestions?

I, too, intend acquire the Denon AVR-4520 primarily for the Audyssey functions although I am considering an Ultimate 5.2.1 Package. Kevin's comment that the MBM is NOT a subwoofer causes me to reconsider using one AVR-4520 Pre-out for the two ULS SWs and the other Pre-out for the MBM, possibly overriding the Audyssey MultiEQ settings for different cross-over frequencies.
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  #12  
Old June 9th, 2013, 8:12 PM
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JerryMeeker JerryMeeker is offline
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I have the 4520, and I repeat my previous recommendation--it is a better idea to get two identical subs, rather than trying to go through the hassle of trying to integrate a sub and an MBM.
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  #13  
Old June 13th, 2013, 10:00 PM
SME SME is offline
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Rayk,

I don't recall where, but I did see someone say that running the dual-sub version of Audyssey with a true sub and MBM plugged into separate outputs does not work. I believe Audyssey expects the subs to be similar and that all it does is applies separate time delays to each sub before calibrating them as one device. Instead, you will definitely want to run them on the same output and use the controls built-in to each sub to integrate them before running Audyssey.
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