Adding an MBM (mid bass module) to your DIY Sound Group speakers - Page 9 - AVS Forum | Home Theater Discussions And Reviews
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post #241 of 259 Old 05-01-2016, 09:45 AM
 
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Most of the benefit of using a midbass module or a design with multiple woofers isn't because it provides relatively more midbass. Spl output is basically the same. It's because it helps mitigate floor/ceiling bounce and room and set up problems so it sounds better or you hear it better.

Too much of a good thing is a bad thing.

Too much midbass is a guaranteed way to make your system sound worse.

Good sound is about balance.

A MBM allows you some extra headroom, and often increases dynamics by reducing the strain on your primary speaker and amp, adding more watts and cone area in the form of an MBM. It's like upgrading your main amp and speakers in a way, because if relieves them of strain or gives them some extra help. By the acoustics of it also helps you hear it.


More isn't better for spl. More is better for balance and response.
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post #242 of 259 Old 05-01-2016, 10:02 AM
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Quote:
Originally Posted by Mfusick View Post
Most of the benefit of using a midbass module or a design with multiple woofers isn't because it provides relatively more midbass. Spl output is basically the same. It's because it helps mitigate floor/ceiling bounce and room and set up problems so it sounds better or you hear it better.



Too much of a good thing is a bad thing.



Too much midbass is a guaranteed way to make your system sound worse.



Good sound is about balance.



A MBM allows you some extra headroom, and often increases dynamics by reducing the strain on your primary speaker and amp, adding more watts and cone area in the form of an MBM. It's like upgrading your main amp and speakers in a way, because if relieves them of strain or gives them some extra help. By the acoustics of it also helps you hear it.





More isn't better for spl. More is better for balance and response.

Yep, I understand this. I guess my question was more directed towards graphs I've seen that were relatively flat and yet people are still saying the sound is lacking in the midbass so they eq more of that band and/or add mbm's.
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post #243 of 259 Old 05-02-2016, 08:23 AM
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Originally Posted by DotJun View Post
Yep, I understand this. I guess my question was more directed towards graphs I've seen that were relatively flat and yet people are still saying the sound is lacking in the midbass so they eq more of that band and/or add mbm's.
Flat isn't always good as everyone has their own preference. Flat just means you are hearing it like the original sound editors wanted you to hear it. Many people like a lot more punch and a LOT more of the deep rumble, so they run their bass up 5-15db over flat.

However, if you have your x-over at 80hz like most setups do, you can get a sharp dropoff at 80hz. It leaves what feels like a null from 80 to around 250-300 hz. On top of this, floor bounce (and back wall reflections) can cause some nulls in this area as well. This is dangerous territory because if you add too much mid bass your sound can get "muddy", but you also want to ease that cliff that results from your subs running hot and regain the "balance". It isn't about making your mid bass "hot", it's about filling in the gap to make it sound balanced.

Here's an example using one of my measured curves. I started flat, then jacked up the subs to my liking. But it left a hole in my mid bass (yellow area). Ideally I am looking for something similar to what is in red (maybe not quite that extreme, but you get the idea). If I had an MBM on a separate amp with DSP control crossed from 80hz to 250hz, I could easily dial it in to fill in that gap and create a smoother transition from the deep bass to the upper midbass range.


Frankly I have plenty of midbass. Gunshots feel real in my theater at reference volume, but compared to the sub bass and midrange, it is lacking. The result is my sound feels less "full" than I would prefer. If I could get 2-3 more db in the 100-300hz range I think it would fill it in nicely.
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post #244 of 259 Old 05-02-2016, 09:16 AM
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Hmm, would it be wise to add an MBM such as the MBM-12 to the back of the room, where the Volt-6 are? The Volt-6 are in angled flat packs, hanging on the wall near my ceiling. They just don't go as deep in vocals like the Volt 10 LX do in their ported enclosures that I use as side surrounds. I've even looked at the PA255 mentioned in the first post here.

My idea is the MBM-12 could provide the necessary extension I want, and with as close as the channels are, one MBM can cover both rear back channels. At least maybe allow myself more control, as I think their crossover points have a phase issue with the main subwoofers, where the LCR doesn't as well. (Rear sides, if memory serves, don't seem to be effected much.)

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post #245 of 259 Old 05-02-2016, 09:44 AM
 
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Originally Posted by DotJun View Post
Yep, I understand this. I guess my question was more directed towards graphs I've seen that were relatively flat and yet people are still saying the sound is lacking in the midbass so they eq more of that band and/or add mbm's.
If you poll 25 people on AVS less than half of them would even agree what midbass actually is, and the other half would argue.

I would not worry too much about what people say.
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post #246 of 259 Old 05-02-2016, 10:27 AM
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@dkersten , your plot (red line) is exactly what I'm talking about. Even if it were a less aggressive curve, 100hz would still be louder than 300hz.

This might make gunshots sound good, but wouldn't it also mean that the lower a persons voice tone is, the louder they will sound? For instance, two people recorded while they are talking at the same spl would sound like one is talking normally (300hz guy) while the other is shouting (100hz guy).
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post #247 of 259 Old 05-02-2016, 10:35 AM
 
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Originally Posted by dkersten View Post
Flat isn't always good as everyone has their own preference. Flat just means you are hearing it like the original sound editors wanted you to hear it. Many people like a lot more punch and a LOT more of the deep rumble, so they run their bass up 5-15db over flat.
I haven't see a lot of evidence this is true^ I have seen a lot of evidence that makes me believe people "THINK" that it is true, but reality is often they also don't know.

If you add 5-15db of midbass most would agree it won't sound great- especially the higher stuff. You get close the critical area where accuracy is preferred, and human hearing ability increases and becomes more acute- so smaller changes are perceived easier.

I'm nearly certain that if I went and dialed up +10db of midbass on anyone's system they would think it sounds worse. I used 10db because it's halfway between your 5-15db range you gave.

My understanding of what BASS is for clarity is all frequencies under the middle C on a piano. That is about 250hz or so, without my looking it up.

That gives you three ranges. The lower bass is the common sub woofer territory of 16-80hz. The mid bass starts above that and reaches to about 150hz, then you have upper bass which is 150-250hz. The definitions are confusing because midbass can mean the middle of the bass range, or it can be interpreted by some to be a half blend of bass and midrange- which really is more upper bass in the 150-400hz range if you take half of bass and half of midrange as your meaning. But clearly from 200hz and up I would say it sounds like midrange to many laymen, and if you polled people to guess what frequency it was, or call it bass or midbass, or midrange I am guessing 200hz+ would be guessed to be midrange because that is what it sounds like, and it's part of the vocal range.

The upper bass register is the most sensitive to SPL increases as hearing becomes more acute in that territory. Adding +10db from 150hz-250hz would not sound good IMO. It would be quite unbalanced, and sound unnatural. In the 80hz-150hz perhaps it might be more tolerable, and certainly below 80hz it becomes even more tolerable because as frequency drops so does your ability to hear it. Adding +10db at 20hz isn't generally a problem for sound quality- and it certainly provides you more of that pant flapping, house shaking aspect.

One point too- +10db has a dramatic increase on the required wattage so makes sure anyone trying to add big boost has a big amp and plenty of extra power.

But I would maintain that above 150hz, it's somewhat important to be relatively flat- and that will all sound there is always an element of balance. Someone who says midbass is lacking often has a room problem, so the sound is weak- a flat or slightly elevated midbass would be perceived to them as relatively more I think, because their problem is not that there is not enough, it's that it's being manipulated by the boundaries of the room.
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post #248 of 259 Old 05-02-2016, 12:25 PM
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Originally Posted by DotJun View Post
@dkersten , your plot (red line) is exactly what I'm talking about. Even if it were a less aggressive curve, 100hz would still be louder than 300hz.

This might make gunshots sound good, but wouldn't it also mean that the lower a persons voice tone is, the louder they will sound? For instance, two people recorded while they are talking at the same spl would sound like one is talking normally (300hz guy) while the other is shouting (100hz guy).
I would say no, but it WILL alter the tonal quality of the voice. Voices are not just a single frequency, they are a mix of several at varying volumes.. my voice might have a spike at 600hz and be 25db down at 100hz, so 2-3db difference at 100hz is not going to be anything extreme. And if my voice were in the midst of explosions that were 30-40 db above the level of my voice, subtle changes like that would be completely unnoticeable unless referenced against a system with a different curve.

But if you were running ALL 100hz sounds too hot then it would start to sound "muddy".
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post #249 of 259 Old 05-02-2016, 04:15 PM
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Quote:
Originally Posted by Mfusick View Post
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Flat isn't always good as everyone has their own preference. Flat just means you are hearing it like the original sound editors wanted you to hear it. Many people like a lot more punch and a LOT more of the deep rumble, so they run their bass up 5-15db over flat.
I haven't see a lot of evidence this is true^ I have seen a lot of evidence that makes me believe people "THINK" that it is true, but reality is often they also don't know.
Oh come on, you can't tell me that people here ONLY buy multiple subs to correct room conditions.... People like more bass than is recorded, so they turn it up. They like more ULF in movies, so they get big subs and build big boxes and run tons of power... and then turn up the subs. At that point you don't have a "flat" response, you have a "house curve".

The perfectly tuned flat system is going to sound perfect to ONE person - the audio engineer who recorded the track. From there it is all subjective, and personally I have never heard a flat system I like more than one with a house curve that suits my ears.

I will grant you this, however: Over the years sound engineers have gotten better at eq'ing music and movies while recording. A lot of stuff recorded in the 70's and 80's sounds positively awful on a flat response curve, and a lot of the basis for not wanting a completely flat response probably comes from that perception that you need to eq it with hot highs and lows to make it sound good. Even with that being said, however, when it comes to reference level listening, I will take +10db on my subs all day long over flat on ANY movie.


Overall I get what you are saying and while I disagree that you need to have flat response to sound good, I think if you have a relatively flat response then running mid-bass hot will probably make it sound muddy. I say relative because even if you have a house curve that you prefer, if there is one range of frequencies that is lower than the curve you will perceive that section is lacking, even if running it hot on a regular flat curve would make it sound muddy.

BTW, that example with the red line was an exaggeration to show the void from running subs hot. If I were to get an MBM, I would use it to get my curve flat (with the subs flat too), then run the subs up to where I want them and then gently fill in the void until it sounded right. One of my speakers shows a clear null between 100 and 300hz, which is a room issue, but overall the problem is one of perception - I feel like I am lacking midbass because of that huge cliff after 100hz. When sounds that include frequencies both below and above that 100hz, it will sound wrong because of the imbalance. The risk is going too hot and muddying the sound, but the alternative is either living with a distinct lack of midbass or dialing down the subs so that the system is dull and boring but flatter.

The beauty of the MBM outlined in this thread is that you have full control. You can not only crank up or dial down the whole MBM, you have DSP so you can fine tune it to blend with your system and make it sound like what works for YOU.
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post #250 of 259 Old 05-02-2016, 09:07 PM
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Flat is great... With DEQ. DEQ is a valuable option in the inuke dsp amps. I run my 18's crossed to my mains at 200hz but this only works for me when it's all eq'ed totally flat and the subs have proper delay set with mains to integrate constructing through the crossover region. Crossing so high is tricky. Once I got it dialed in, I turned up the bass and it sounded like crap, made voices super deep etc. So I went back to flat and turned to DEQ to give me the bass boost below 120hz that gradually boosted less as I turned the dial toward reference volume.
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post #251 of 259 Old 05-03-2016, 06:39 AM
 
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If you doubt me then add +10db at 200hz and you'll see what I'm talking about instantly.

I do agree with the downward slope, and that bass can be a little hot, but there's a practical balance to it. If someone really prefers something it's not my place to try to stop them, or critique that. I believe my point has been misunderstood. It was never about that. My point was more for the larger group of people that don't know, and don't realize, to keep them on the straight and narrow of understanding. A totally new person might quickly read about midbass enhancements and think that's what they need for good sound or it will make it sound better, but again my point isn't that more is better, it's that better is many different things and included is the element of balance.
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post #252 of 259 Old 05-03-2016, 08:17 AM
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Flat is great... With DEQ. DEQ is a valuable option in the inuke dsp amps. I run my 18's crossed to my mains at 200hz but this only works for me when it's all eq'ed totally flat and the subs have proper delay set with mains to integrate constructing through the crossover region. Crossing so high is tricky. Once I got it dialed in, I turned up the bass and it sounded like crap, made voices super deep etc. So I went back to flat and turned to DEQ to give me the bass boost below 120hz that gradually boosted less as I turned the dial toward reference volume.
Dynamic EQ's make a flat response into a response curve that sounds better, or in other words, it makes it so it is no longer flat. If you like the DEQ in the inuke, try it in Audyssey where it covers the whole spectrum, not just your subs. From my measurements it is running the stuff below 80hz about 5-7 db hotter (at about -20db on the volume knob), plus it will boost other areas as well to compensate for the lack of dynamics at lower level listening.

Using an MBM you could still get the midbass punch you get from your subs at 200hz but then have the freedom to boost your subs to add more impact to special effects without the downside of adding too much to your midbass range. Also you won't be trying to make a woofer play 16hz and 200hz at the same time.
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post #253 of 259 Old 05-03-2016, 09:11 AM
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Originally Posted by dkersten View Post
But if you were running ALL 100hz sounds too hot then it would start to sound "muddy".


Umm, if you boost 100hz, wouldn't the outcome be that all sounds at that frequency be boosted? It's not like you can boost a 100hz gunshot and skip the voices.
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post #254 of 259 Old 05-03-2016, 10:30 AM
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Originally Posted by DotJun View Post
Umm, if you boost 100hz, wouldn't the outcome be that all sounds at that frequency be boosted? It's not like you can boost a 100hz gunshot and skip the voices.
Sorry, that was horribly worded and I am not even sure what I was trying to say, lol. I guess that's what I get when trying to reply at work on a busy day, haha.


I stand by the rest of that reply though. Sounds are almost never one frequency, they are a combination of several, so jacking up a single frequency with a high Q is going to result in a tonal change more than anything else, as long as you don't get too extreme with your boosting or cutting. And as long as your boosting or cutting is smoothing out your overall response relative to the whole spectrum, it will likely sound better than before the change. This isn't universal of course, some curves will sound like crap. If you turn up a frequency that is already balanced well with the rest of the spectrum then you will have adverse results.
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post #255 of 259 Old 05-03-2016, 06:18 PM
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Quote:
Originally Posted by dkersten View Post
Dynamic EQ's make a flat response into a response curve that sounds better, or in other words, it makes it so it is no longer flat. If you like the DEQ in the inuke, try it in Audyssey where it covers the whole spectrum, not just your subs. From my measurements it is running the stuff below 80hz about 5-7 db hotter (at about -20db on the volume knob), plus it will boost other areas as well to compensate for the lack of dynamics at lower level listening.

Using an MBM you could still get the midbass punch you get from your subs at 200hz but then have the freedom to boost your subs to add more impact to special effects without the downside of adding too much to your midbass range. Also you won't be trying to make a woofer play 16hz and 200hz at the same time.
Audyssey dynamic eq is good too, though the way it emulates the Fletcher Munson curve is fixed. It does not boost much above 100hz, so the higher crossover region remains unaffected. Having a higher crossover means you can't run your bass hot as increasing the sub trim bumps up the entire channel. Having a cliff at 80hz or 100hz to your mains because you run your subs super hot may not be so bad, great even, but when it's localizable (above 120hz) it sounds terrible, imo. DEQ in audyssey and on the inuke is the perfect fix, given your subs are near your mains. I agree an mbm is better than running ulf and upper bass on the same speaker but until I get a real room, I'll have to live with it.
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post #256 of 259 Old 05-04-2016, 08:06 AM
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Originally Posted by corradizo View Post
Audyssey dynamic eq is good too, though the way it emulates the Fletcher Munson curve is fixed. It does not boost much above 100hz, so the higher crossover region remains unaffected. Having a higher crossover means you can't run your bass hot as increasing the sub trim bumps up the entire channel. Having a cliff at 80hz or 100hz to your mains because you run your subs super hot may not be so bad, great even, but when it's localizable (above 120hz) it sounds terrible, imo. DEQ in audyssey and on the inuke is the perfect fix, given your subs are near your mains. I agree an mbm is better than running ulf and upper bass on the same speaker but until I get a real room, I'll have to live with it.
If you were looking for more sub bass closer to reference volume (which is what I love.. rocking those subs hard when the highs are comfortably loud), you could always eq in a few more db from 16-80hz.. if you have a couple peq channels not being used, start at around 45 hz and use a low Q and bump it up, and if it drags your 80hz+ up, use another channel with a high Q to tame it. You will push more power to that range yet still get the midbass hit you are after above 80hz. Then you could ease down the DEQ a bit and get more sub bass at all volumes without making it muddy..
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post #257 of 259 Old 05-11-2016, 10:56 AM
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PA255-8 dual MBM

Tux,

does the 18l (.64cuft) sealed for the PA255 include its displacement or does that need to be added in for a gross box larger than 18l? and if so do you know that the speaker displacment is? having trouble finding that in the specs, Im thinking of getting one of these per side http://www.sonicelectronix.com/item_...va-MDFD10.html to be lazy since Im really not good with wood and the airspace seemed like it would be ideal if the 18l was a net figure and not a gross. down the road it would then double as a speaker stand for the L/R on top of it.

Thanks for all your help in these forums.

2000 watts of power and climbing

-Fred
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post #258 of 259 Old 05-11-2016, 12:37 PM - Thread Starter
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Being that its sealed you can get away with 18L gross but bigger will always help reduce Q.

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post #259 of 259 Old 05-13-2016, 06:21 PM
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Quick comparison of woofer on bottom vs port on bottom for those who were curious:

Blue is woofer on bottom, yellow is woofer on top. Basically identical other than the little extra spike at 265Hz.




And here is with the same EQ applied to both. Blue is woofer on bottom, green is woofer on top.




So there's very little difference, at least in my room. YMMV.

Last edited by strakele; 05-14-2016 at 05:12 AM.
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