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Discussion Starter #1

I currently have a 5400 + 2 VMP build that has plenty of 15-80hz output, but is definitely lacking in anything below 15hz. My goal now is to make some serious gains in the 5-10hz department. I guess you could say it's just the next step up for me.

http://www.avsforum.com/avs-vb/showt...0#post20514030


For sealed subs, this build definitely sticks out: http://www.avsforum.com/avs-vb/showthread.php?t=1314884


I like the design of the array layout since the depth of the cabinet is not excessive. The depth of my current cabinet being around 33 has been an annoyance and I've had to change the positioning of the main speakers and TV to accommodate and also not look so funny. I know there are advantages of the dual-opposed design, but due to cabinet size that's not in the cards right now.


I do have some questions regarding the array design since I won't be using the insane powerful LG clone amps like notnyt has.


First off, what are the advantages/disadvantages to having both drivers in one sealed chamber in the cabinet opposed sealing each off from the other?


notnyt is using one amp per cabinet since the power is there, so I can see why one large sealed chamber makes sense. What if I were going to use a pair of amps to drive the cabinet, like one ep4000 per driver, or run one larger amp in stereo like my Peavey 4080hz rated at 2k RMS per channel at 4ohm? Would I want to seal each driver from the other, or does that cause a decrease in performance?


Thanks!

 

 

 

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one reason to make a dual opposed cabinet is that it can be relatively lightweight and not vibrate. when the cabinet vibrates, you are losing energy that should be going to creating sound.


the most affordable way to get 5-10 hz content is with an infinite baffle type setup...essentially a very large sealed subwoofer where the drivers don't need giant motors because they aren't fighting internal cabinet pressures.


also with infinite baffle, you hardly need any power, again because you aren't fighting against internal air pressure of a cab.


you can read about many projects here: http://ibsubwoofers.proboards.com/index.cgi
 

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Quote:
My goal now is to make some serious gains in the 5-10hz department. I guess you could say it’s just the next step up for me.

I think you need atleast 4 LMS5400s. I have 2 LMS5400s and even though they give me decent output down to 10Hz I believe its still not enough when it comes to having 10Hz performance that makes a real difference.
 

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Will this me in addition to what you have now?
 

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For now it means I have limited

OP understands that 10Hz performance is 100% about displacement/power requirements. Displacement is Xmax * Surface Area which should be > 25 Liters to have enough output for 10Hz performance to be meaningful.
 

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Discussion Starter #7
Quote:
Originally Posted by penngray
I think you need atleast 4 LMS5400s. I have 2 LMS5400s and even though they give me decent output down to 10Hz I believe its still not enough when it comes to having 10Hz performance that makes a real difference.
Agreed.


At the moment I have ZERO performance at 10hz. Since my PR's are tuned to 16hz I have a subsonic filter at 15hz.


From what I've seen from graphs, before room gain, and IF both drivers receive 2k RMS each, I should be around 103-104db at 10hz. When the money is there I'd build an identical enclosure and get closer to 110db. After room gain things should be looking pretty good at that point.


So the question, do I seal each sub off from the other?
 

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Discussion Starter #8
Quote:
Originally Posted by t6902wf
Will this me in addition to what you have now?
I’m going to re-use the driver that’s in my current DIY build. However, the dual sealed LMS will be used in conjunction with two JTR Caps.
 

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Quote:
Originally Posted by lukeamdman
Agreed.


At the moment I have ZERO performance at 10hz. Since my PR's are tuned to 16hz I have a subsonic filter at 15hz.


From what I've seen from graphs, before room gain, and IF both drivers receive 2k RMS each, I should be around 103-104db at 10hz. When the money is there I'd build an identical enclosure and get closer to 110db. After room gain things should be looking pretty good at that point.


So the question, do I seal each sub off from the other?
You have a decision, do you just want to maximize output or do you want the ability to possibly smooth out the in room bass response.


The only reason you would go with separate sealed designs is because you want placement flexibility. If you are going just have the subs stacked together then put them in one box for maximum output, minimum vibration (ie. sealed dual opposed). Of course if you like the looks of a single box dual woofers facing you then go that route (ie. Gotta love what Notnyt built
)


You just have to decide what your priorities are.


Do you want to see those cool looking LMS5400 drivers?


Do you want to maximize output?


Do you want to try and smooth out in room response?


FWIW, you really need > 110dB at 10Hz to make it meaningful. Will your room gain give you that? Who knows.
 

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Something else to consider. You mentioned you wanted to dig down to 5hz. I did some testing with my system to see where meaningful output stopped. Once I started to go below 7hz, it became hard to notice the output. Doors would be shaking and stuff would be rattling, but below that there wasn't really much tactile sensation at all. Because of that, I added a steep HPF to prevent over excursion below 7hz.
 

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Discussion Starter #11

Quote:
Originally Posted by penngray /forum/post/20857814


You have a decision, do you just want to maximize output or do you want the ability to possibly smooth out the in room bass response.


The only reason you would go with separate sealed designs is because you want placement flexibility. If you are going just have the subs stacked together then put them in one box for maximum output, minimum vibration (ie. sealed dual opposed). Of course if you like the looks of a single box dual woofers facing you then go that route (ie. Gotta love what Notnyt built
)


You just have to decide what your priorities are.


Do you want to see those cool looking LMS5400 drivers?


Do you want to maximize output?


Do you want to try and smooth out in room response?


FWIW, you really need > 110dB at 10Hz to make it meaningful. Will your room gain give you that? Who knows.

This is hard to explain and I'm obviously not asking in a clear enough manner



I have a performance (SPL) question in regards to this: Take the dual drivers in a single cabinet like notnyt's build (both drivers are in the same cabinet with no divider in between. If you push on one driver the other will move since they're in the same sealed compartment). What would the difference be if he put a divider in between them so that even though they're in the same cabinet, their sealed air space is separated. Would there be a performance (SPL) disadvantage?
 

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Your question was clear and the answer is no, their will be no SPL differences.


BUT as Penn clearly pointed out, there are performance differences when two independant enclosures are used with different placement over one, large enclosure. Given the response curve of a sealed system without eQ, the difference in room response could be substantial. In other words, build two.
 

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Quote:
Originally Posted by mayhem13 /forum/post/20858489


In other words, build two.

I hope by that you meant build two seperate duals. God forbid that he lose the cool factor of an upright dual driver sealed enclosure.
 

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Discussion Starter #14
Quote:
Originally Posted by mayhem13
Your question was clear and the answer is no, their will be no SPL differences.


BUT as Penn clearly pointed out, there are performance differences when two independant enclosures are used with different placement over one, large enclosure. Given the response curve of a sealed system without eQ, the difference in room response could be substantial. In other words, build two.
I definitely intend on building two, but each will have dual drivers



Until I have enough money for the second I already have two other subs to even out the room response.
 

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Quote:
Originally Posted by lukeamdman
I definitely intend on building two, but each will have dual drivers



Until I have enough money for the second I already have two other subs to even out the room response.
Then build four instead.
 

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Discussion Starter #16

Quote:
Originally Posted by notnyt /forum/post/20857844


Something else to consider. You mentioned you wanted to dig down to 5hz. I did some testing with my system to see where meaningful output stopped. Once I started to go below 7hz, it became hard to notice the output. Doors would be shaking and stuff would be rattling, but below that there wasn't really much tactile sensation at all. Because of that, I added a steep HPF to prevent over excursion below 7hz.

Interesting and good to know!


On my SMS I'll put a 7hz/48db crossover on it.
 

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Maybe, Save floor space??
 
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