Mid Bass Modules

[lsiberian]

Not sure how many of you are familiar with this concept.

Basically you take the 50hz- 120 or 150hz and use a smaller 8inch sub for it. Then you use something like a 12" Axis for your below 50hz response.

It helps with dynamic classical music which even at SPLs of 80 can cause issues with mid range woofers.

You need at least 2. Place them with the main speakers and then corner load your sub 50hz. Something like a DCX2496 can be used to integrate them with your mains.

My plans are to use a pair of JL Audio 8w6s I picked up for cheap as the MBM and then pair it with a 12" axis build. (Unless i can spare the change for the 15" when the time comes).

I really like the concept. But as you folks know I'm always tinkering so what else is new. This hobby has bit me hard. And I love every minute of it.

What do you think of the concept? Don't be afraid to chime in even if you are a newb like me at this.

 

[alexwakelin]

Mike C was using sealed kappa 12s for midbass wasn't he?

 

[alexwakelin]

Found this picture in Mike C's system thread. I think there was a build thread for it too, but I can't seem to find it right now. I think this was supposed to be a midbass module.

 

[ParadigmDawg]

This is the one Andrew built. That picture is taken at my friends house when we were testing it.

 

[Adam]

This is the one Andrew built.

Doesn't that guy put grills on anything?

 

[Guiria]

Interesting concept, I hope some veterans chime in soon. I have a dip in frequency response from about 80 Hz to 250 Hz when listening in stereo, yeah, its pretty wide . When I add the center channel the dip isn't as wide and starts to climb at about 150 Hz. I have yet to determine if this valley in response is simply a room node or if the output of my speakers cannot fill my 2300 ft^3 room at those frequencies. I've tried increasing the xover on the receiver to 120 Hz and it did very little, besides, localization issues starting rearing their heads so I brought it back down to 80 Hz.

If I could add something that would essentially make my 2-way mains become 3-ways I would seriously consider it. Seems like all I would have to do is add a simple low pass filter and connect it somehow to my mains in such a way that the overall speaker system(2-way + midbass module) was 6-8 ohms. Of course then I also have sensitivity of the midbass module to match up as well and I'm not sure how that is even done...yup, starting to get complicated.

 

[WmAx]

Interesting concept, I hope some veterans chime in soon. I have a dip in frequency response from about 80 Hz to 250 Hz when listening in stereo, yeah, its pretty wide . When I add the center channel the dip isn't as wide and starts to climb at about 150 Hz. I have yet to determine if this valley in response is simply a room node or if the output of my speakers cannot fill my 2300 ft^3 room at those frequencies. I've tried increasing the xover on the receiver to 120 Hz and it did very little, besides, localization issues starting rearing their heads so I brought it back down to 80 Hz.

If I could add something that would essentially make my 2-way mains become 3-ways I would seriously consider it. Seems like all I would have to do is add a simple low pass filter and connect it somehow to my mains in such a way that the overall speaker system(2-way + midbass module) was 6-8 ohms. Of course then I also have sensitivity of the midbass module to match up as well and I'm not sure how that is even done...yup, starting to get complicated.

The only way to do this correctly is to be able to use an active digital xover on your mains, subs and midbass modules. This requires you to have external component amp for the mains (not a surround receiver's built in amps; as you have no way to insert the required digital xover in the mains loop) so that you can use the digital xover between all of the speakers involved.

-Chris

 

[fredk]

You've been reading Dr. Geddes havn't you?

This approach is apealing to me because I am in a smaller space. I don't need a slew of big honkin subs to preasurize my room.

I wish I had the cash to give this a try, but, at a minimum I need to upgrade my receiver to have a variable crossover I can set higher than 80Hz.

Geddes uses 12" & 15" pro drivers in a sealed cabinet for his mains so he gets natural rolloff starting at around 150Hz.

Two small, sealed 8/10"ers and a larger corner loaded sub for the low stuff would fit well into my setup.

 

[Guiria]

After doing some research I have come up with a concept for adding midbass modules to my existing setup. While I agree with Wmax that adding external amplification and digital xover/EQ to the whole system would be ideal I think my proposal makes a good second run at the idea.

I would use something like the Dayton RS225-4 8" driver built into a speaker stand for my bookshelves. The box would be 1 cubic foot net internal volume. The f3 is around 60Hz which is plenty low since these are being designed to fill a lull in response from 80-200 Hz. Each stand would then be powered by its own Dayton SA100 100 watt amp that has high level in and outputs with a xover that goes up to 180 Hz. I would set the xover at 180 Hz and use the high level in/outputs for my bookshelves.

This gives me some flexibility in level matching the 8" speakers to the rest of my system. Since my receiver is rated at 100 watts per channel I figured the 100 watt amp would suffice. Dayton also has a 240 watt amp I would consider if I decided to pull the trigger on the idea.

What do you think?

 

[WmAx]

After doing some research I have come up with a concept for adding midbass modules to my existing setup. While I agree with Wmax that adding external amplification and digital xover/EQ to the whole system would be ideal I think my proposal makes a good second run at the idea.

I would use something like the Dayton RS225-4 8" driver built into a speaker stand for my bookshelves. The box would be 1 cubic foot net internal volume. The f3 is around 60Hz which is plenty low since these are being designed to fill a lull in response from 80-200 Hz. Each stand would then be powered by its own Dayton SA100 100 watt amp that has high level in and outputs with a xover that goes up to 180 Hz. I would set the xover at 180 Hz and use the high level in/outputs for my bookshelves.

This gives me some flexibility in level matching the 8" speakers to the rest of my system. Since my receiver is rated at 100 watts per channel I figured the 100 watt amp would suffice. Dayton also has a 240 watt amp I would consider if I decided to pull the trigger on the idea.

What do you think?

I must strongly disagree with your suggestion of using the passive high signal level xover built into a plate amp or any other generic high level signal crossover. It will not work well. The lower mid-range band (180Hz) is CRITICAL for SQ. You must use the proper equipment to integrate/crossover properly.

A passive xover at such lower frequencies is possible, but it must be designed specifically for the impedance curve of the speaker system to which it is connected.

-Chris

 

[Guiria]

I must strongly disagree with your suggestion of using the passive high signal level xover built into a plate amp or any other generic high level signal crossover. It will not work well. The lower mid-range band (180Hz) is CRITICAL for SQ. You must use the proper equipment to integrate/crossover properly.

A passive xover at such lower frequencies is possible, but it must be designed specifically for the impedance curve of the speaker system to which it is connected.

-Chris

I have to ask what frequency isn't critical for SQ? While I'm not prepared to buy 3 different amplifiers and a DCX to run my mains + midbass modules through I might be able to round up enough funds in a couple of weeks for something like the above mentioned speakers + an A500 and DCX. Would I be able to integrate the midbass modules fairly well without adding another amplifier to the DCX to run my 2-ways?

As I'm unfamiliar with the DCX would I be able to control my subwoofer independant of the midbass modules?

 

[lsiberian]

I have to ask what frequency isn't critical for SQ? While I'm not prepared to buy 3 different amplifiers and a DCX to run my mains + midbass modules through I might be able to round up enough funds in a couple of weeks for something like the above mentioned speakers + an A500 and DCX. Would I be able to integrate the midbass modules fairly well without adding another amplifier to the DCX to run my 2-ways?

As I'm unfamiliar with the DCX would I be able to control my subwoofer independant of the midbass modules?

You would only need the DCX for 4-waying. You could use a passive crossover between the tweeter and upper midrange woofer.

However your picking a woofer not a subwoofer. I suggest you look for a subwoofer type driver. For example the JL Audio 8w6s I picked up will extend to 25hz, but at 50hz they can be run at full power. So they stay in their sweet spot.

basically to pull this off I suggest 2 Behringer EP2500s and a DCX 2496. You could easily drive the sub and MBMs and integrate them with the DCX. You would only need 3 channels of the DCX. So you could even pair them with an A500 and use the crossover to cross the subs and mains. This would lead you to sonic nirvana. There are other ways to achieve this though. As they say there is more than one way to skin the cat. Though I would never do such a think to cute animals.

 

[Guiria]

I think our applications of the midbass modules are different. My sub has plenty of output below 50 Hz and I plan on adding a second so the output and smooth response will improve even more below 80 Hz. I'm looking for something to play optimally between 80 - 200 Hz. All the xmax, huge voice coils, and super stiff cones on subwoofers just add weight. In the range I'm talking about it's overkill and a quality, lighter weight woofer would sound better IMO.

I'd rather use something designed to play in those frequencies rather than stretching the limits of a high performance subwoofer where the high performance is all below the cut off frequency anyways.

This sounds like quite ($$) a project to pull off successfully.

I think I'll go back to building a Loki center channel. The center is the weak spot in my system right now anyways.

 

[lsiberian]

I think our applications of the midbass modules are different. My sub has plenty of output below 50 Hz and I plan on adding a second so the output and smooth response will improve even more below 80 Hz. I'm looking for something to play optimally between 80 - 200 Hz. All the xmax, huge voice coils, and super stiff cones on subwoofers just add weight. In the range I'm talking about it's overkill and a quality, lighter weight woofer would sound better IMO.

I'd rather use something designed to play in those frequencies rather than stretching the limits of a high performance subwoofer where the high performance is all below the cut off frequency anyways.

This sounds like quite ($$) a project to pull off successfully.

I think I'll go back to building a Loki center channel. The center is the weak spot in my system right now anyways.

I think I understand your goals. An MBM using an 8 inch sub wouldn't be all that difficult. My subs only take up to 200watts each. I don't see a problem running them up to 200hz. Though I don't see this as necessary. My5" drivers can extend to 120hz with no issues even at higher volumes.

The center channel would be a better investment ATM.

 

[MatthewB.]

I actually use the built in subs on my DefTech BP7001's as mid bass subs. Even though DT claims the subs can go down to 18Hz (they drop like a rock below 30Hz, and since my Onkyo 805 can only go down to 40Hz before setting to full range. I set my mains at 40Hz and the SVS NSD12/2 kicks in below that. By doing this (instead of setting the 7001 subs to Large) it tightened up the bass big time and I get overall great bass all around with the internal subs handing everything between 40-80Hz and the sub in the back of the room (next to siiting poistion) handles all the real deep bass. It is very tight and controlled.
I recall being at MajorLosers house a few years back and listening to his Hsu subs along with his mid bass subs and just being blown away with how tight and controlled his bass was. This alone was the main contributing factor of me buying my DT 7001's so that I could use the 10" drivers as mid bass subs and so far has worked beautifully.

 

[lsiberian]

What kind of dampening and bracing should one use in a sealed MBM. I was thinking of 2inches on all sides and 4 on the back.

And a just a few braces in between the back and front baffle with round cut outs. These will be eventually paired with acoustically neutral upper-mids. So I'm very concerned about sonic quality here.

 

[pjoseph]

I was wondering about using a active electronic crossover with a 7.1 receiver.

I am not sure if it would work or not.
my receiver says it has 7 channel inputs so i am thinking I can hook up from the electronic crossover to the individual channels would this work? What else would 7 inputs be used for?

Wmax i know you said this will not work but then what is the point of having 7 channel inputs?
The receiver i am referring to is a marantz sr4001.

thanks

 

[lsiberian]

I was wondering about using a active electronic crossover with a 7.1 receiver.

I am not sure if it would work or not.
my receiver says it has 7 channel inputs so i am thinking I can hook up from the electronic crossover to the individual channels would this work? What else would 7 inputs be used for?

Wmax i know you said this will not work but then what is the point of having 7 channel inputs?
The receiver i am referring to is a marantz sr4001.

thanks

Active crossovers are hooked in one of 2 ways to a receiver.

1) Hook it up to the pre-amp outs and use an external amp to power the speakers on the other side of the crossover.

2) Use the receiver as an Amp and put the crossover in front of it. (This requires another pre-amp source though.

 

[Guiria]

2) Use the receiver as an Amp and put the crossover in front of it. (This requires another pre-amp source though.

So in theory you could use your DVD player as your pre-amp source, run analog cables to your active crossover, and then run cables from that to your amp(receiver).

This setup would only be good for your DVD input on your receiver however and I'm not sure how you can override the built in crossover settings of the receiver since you have your active crossover before the receiver which isn't the norm. I guess if you set everything to large that would leave the bandwidth wide open through your receiver...just thinking out loud here.

 

[WmAx]

I was wondering about using a active electronic crossover with a 7.1 receiver.

I am not sure if it would work or not.
my receiver says it has 7 channel inputs so i am thinking I can hook up from the electronic crossover to the individual channels would this work? What else would 7 inputs be used for?

Wmax i know you said this will not work but then what is the point of having 7 channel inputs?
The receiver i am referring to is a marantz sr4001.

thanks

Yes, many receivers have 'DIRECT INPUTS' on the back panel to feed external sources directly to all of the receiver's amplifier channels. However, I believe that you will find that you will not be able to feed the receiver's OUTPUT PREAMP JACKS to the DIRECT INPUTS and get the receiver to work in this configuration. It would be easy for the manufacturer to allow this to work with a firmware upgrade, but as it is, you are not likely to find a receiver that will do this. Of course, feel free to try it; maybe you will get lucky.

There is also the option of opening up the receiver and cutting the circuits that feed the amplifier channels. Now insert a bypass circuit and install appropriate extra jacks on the back of the receiver. I have done this in the past. But you need to fairly comfortable messing about with your electronic internals to do this....

-Chris