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Discussion Starter #1 (Edited)
I am planning on having a dedicated theater built by a well respected industry pro. It has already been designed and calls for 2 subs up front behind a AT screen and around 3 smaller "fill" subs hidden in columns around the room purely for evening out the inroom response (ie these dont have to get as low/loud as the main subs) For the 2 up front I am building 2 Dual MalX Opposed sealed boxes. This installer classically uses triad inwall subs for the column subs as shown here:
http://www.triadspeakers.com/products/iwb6sub.html
I have attatched the blueprints of the way the columns will be built.
The triad subs are nice but being a DIY sub buy I know I can either get the same performance for less $ or more for the same $ going diy. I was thinking of using shivas but these triad boxes are quite small (dimensions are ~14x19x6deep) so I am looking for suggestions as to what to do. The triad site says that these are an F3 of 20hz. I cannot get the shiva to model that type of response in this size of box. Any thoughts?

In the drawing the top cutouts are for surrounds and the bottom for the subs.
 

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I am planning on having a dedicated theater built by a well respected industry pro. It has already been designed and calls for 2 subs up front behind a AT screen and around 3 smaller "fill" subs hidden in columns around the room purely for evening out the inroom response (ie these dont have to get as low/loud as the main subs) For the 2 up front I am building 2 Dual MalX Opposed sealed boxes. This installer classically uses triad inwall subs for the column subs as shown here:
http://www.triadspeakers.com/products/iwb6sub.html
I have attatched the blueprints of the way the columns will be built.
The triad subs are nice but being a DIY sub buy I know I can either get the same performance for less $ or more for the same $ going diy. I was thinking of using shivas but these triad boxes are quite small (dimensions are ~14x19x6deep) so I am looking for suggestions as to what to do. The triad site says that these are an F3 of 20hz. I cannot get the shiva to model that type of response in this size of box. Any thoughts?

In the drawing the top cutouts are for surrounds and the bottom for the subs.
They are including the DSP equalization in their curve to get the 20Hz F3. That is fair, since they are selling a system, not a raw driver. It is using a 10" driver, in a box that is just under 1 cubic foot. A Shiva would work in the same application but the box would have to be deeper (the driver is deeper) and the equalization would have to be part of the design.

It may or may not be worth the trouble. They have a nice solution, already designed and since your using them in multiple locations they may have enough grunt. Could you build something cheaper? Maybe... I don't know what they cost but you have to be able to design the EQ curve and it depends on how you value your time. It is fairly easy to design a solution with more output but it may not be cost effective unless you have the equalization tools, measurement experience etc...

Kevin Haskins
Exodus Audio
 

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Discussion Starter #3
Kevin,
thanks for the tips. I am not sure on the price but looking around I am fairly confident they would be over 1200 EACH.
We are already gonna be using 2 QSC DSP322ua DSP's http://www.qscaudio.com/products/network/dsp/dsp_322ua.php for
all the Eq/DSP and we will have enough channels to incorporate the subs for eq'ing (each unit has 8 inputs and outputs)

So all I would need is an amp (easy/cheap). I am going to be paying the guy to configure/calibrate the audio/program the dsp anyway.

On a separate note, for the front subs is there any advantage to building 4 smaller sealed subs vs 2 larger boxes with opposing drivers (either solution has 4 drivers, all sealed) other than cabinet vibration and its easier to build 2 vs 4 boxes? All 4 will be MalX drivers, 2 of the earlier generation, and 2 I have yet to buy.
I could also not buy two more Mal X and instead get 4 PR's and go up/downfiring driver and 2 opposing PR's per box. Any thoughts?
 

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Kevin,
thanks for the tips. I am not sure on the price but looking around I am fairly confident they would be over 1200 EACH.
We are already gonna be using 2 QSC DSP322ua DSP's http://www.qscaudio.com/products/network/dsp/dsp_322ua.php for
all the Eq/DSP and we will have enough channels to incorporate the subs for eq'ing (each unit has 8 inputs and outputs)

So all I would need is an amp (easy/cheap). I am going to be paying the guy to configure/calibrate the audio/program the dsp anyway.

On a separate note, for the front subs is there any advantage to building 4 smaller sealed subs vs 2 larger boxes with opposing drivers (either solution has 4 drivers, all sealed) other than cabinet vibration and its easier to build 2 vs 4 boxes? All 4 will be MalX drivers, 2 of the earlier generation, and 2 I have yet to buy.
I could also not buy two more Mal X and instead get 4 PR's and go up/downfiring driver and 2 opposing PR's per box. Any thoughts?
Holy cow... $1200 each? I don't charge enough money for what I do. :crying:

Your rocking the boat by hiring a guy, and then telling him what to use. It always ticks me off when people hire me to do something and then stand over my shoulder telling me what to do.

He/they probably have a certain line they sell. The products have to have margin in them because they make a living doing these things. Nothing wrong with that. I'd either hire a guy and let him do his job or not hire them and do it yourself.

No problem splitting enclosure volumes. The driver doesn't care either way. Sealed is much easier from a design standpoint. You just have a box, and a driver and there are not as many variables to balance. With the number of drivers you have in that room, you won't be needing extra output. I'd stick with sealed just for simplicity sake.

Kevin Haskins
Exodus Audio
 

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Discussion Starter #5
considering the total overall cost of what I am paying him for the whole project (they are physically building the whole dedicated room, doing the sound treatment/accoustic analysis, control system, projector, masking screen, etc), those three subs are actually a very small percentage of the overall project cost so they would be silly to give me flack over a minor cost in the big scheme of things but I understand what you are saying about "rocking the boat". Its weird for them I think b/c most people that hire them to do as big of a project as I am are hands off and want them to do everything where as I LIKE to be involved and want explanations on why the solution they have proposed is better than another way (and not just "we always do it that way" or "trust me")

I think I will just stick with the 4 sealed drivers and forgo the PR's. Less holes to cut out!
 

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considering the total overall cost of what I am paying him for the whole project (they are physically building the whole dedicated room, doing the sound treatment/accoustic analysis, control system, projector, masking screen, etc), those three subs are actually a very small percentage of the overall project cost so they would be silly to give me flack over a minor cost in the big scheme of things but I understand what you are saying about "rocking the boat". Its weird for them I think b/c most people that hire them to do as big of a project as I am are hands off and want them to do everything where as I LIKE to be involved and want explanations on why the solution they have proposed is better than another way (and not just "we always do it that way" or "trust me")

I think I will just stick with the 4 sealed drivers and forgo the PR's. Less holes to cut out!
One thing is for sure, the more you understand the better your results. A lot of people think that spending money is how you get the best results. They are wrong, it is knowledge that will get you the furthest along the performance scale so getting your nose in the process has its advantages.

If you are using a bunch of them, I can design you a simple LT board that will equalize the Shiva for the application. It will cost money and take time and in the end, I'm not sure you will save all that much money. It will crush that little 10" though.

Kevin Haskins
Exodus Audio
 

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Discussion Starter #7
Interesting. Since overall output is not needed, just filling in for room nulls, I am unsure if I will go this route 9building custom LT's)for the column subs. My designer was saying that the columns really only needed to go down to around 30 hz with the 2 large subs up front doing 20hz and below at reference level at the main seating positions. although I appreciate the offer. Now, I will be building the boxes for the 4 sealed MalX so I might be interested in a simple LT circuit for them if the QSC DSP's are not enough although looking at the specs they should be quite capable (I hope so, they aren't cheap either!) My somewhat simple understanding of LT is that it can be replicated with a combo of 3 filters employed on the QSC DSP, two band (bell shaped) filters and one 12dB/octave shelving filter. The first band filter changes the Q of the box/driver to 0.7 at it's Fb. The shelving filter changes the response to Q=0.7 at the new desired Fb. The second band filter sets the Q to whatever you want it to be at the new Fb. Since I am gonna be using these to eq the room and add delays for the 2 rows of surrounds I might as well use it to pseudo-LT the subs right?
 

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Interesting. Since overall output is not needed, just filling in for room nulls, I am unsure if I will go this route 9building custom LT's)for the column subs. My designer was saying that the columns really only needed to go down to around 30 hz with the 2 large subs up front doing 20hz and below at reference level at the main seating positions. although I appreciate the offer. Now, I will be building the boxes for the 4 sealed MalX so I might be interested in a simple LT circuit for them if the QSC DSP's are not enough although looking at the specs they should be quite capable (I hope so, they aren't cheap either!) My somewhat simple understanding of LT is that it can be replicated with a combo of 3 filters employed on the QSC DSP, two band (bell shaped) filters and one 12dB/octave shelving filter. The first band filter changes the Q of the box/driver to 0.7 at it's Fb. The shelving filter changes the response to Q=0.7 at the new desired Fb. The second band filter sets the Q to whatever you want it to be at the new Fb. Since I am gonna be using these to eq the room and add delays for the 2 rows of surrounds I might as well use it to pseudo-LT the subs right?
You understand it well enough. Linkwitz outlined how it works electrically and mathematically but there is nothing that says you cannot use a DSP, that doesn't fit the electrical transfer function explicitly like Linkwitz described and still get good results. For subwoofers, you don't need text-book solutions because the room has its way with the response down low. The main thing is to worry about your overall room response and your designer is correct, the multiple subs will most likely average out the room issues which primarily are 30-150Hz. Use the four Maelstroms up front to do the heavy lifting and an array of smaller subs dispersed about the room to average out the room response. There is nothing wrong with that solution. It is obviously one that works only if you have a large budget and a dedicated room but that describes you perfectly.

Drive on!

Kevin Haskins
Exodus Audio
 
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