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Discussion Starter · #1 · (Edited)

I am working on designing a subwoofer system using the Aurasound NS18-992-4A as the driver.

People I have talked to have said they'd like to see someone use this driver in a LLT alignment because it's a great driver. I'm not quite sure how well it would work for LLT though.

So far, this is what I have come up with:

Four Aurasound NS18-992-4A Drivers - These were chosen for their linearity and low distortion. The underhung coil and NRT topologies are another reason for being chosen. This way, I can power them up to the point where the voice coil is at the end of its range and have almost no compression or non-linearity.

One 20-22 Cubic Foot Enclosure Tuned to 13hz *Per Driver* - This seems to model well considering room gain. I've read around and found that they recommend four subs with one at the midpoint of each wall or in each corner so four separate enclosures rather than one or two seemed best. These will be built as SUPER-inert enclosures with baltic birch. One eight inch port seems to model well.

Crown CE4000 Amplifier - Almost everyone who's recommended an amp to me has recommended this one. A lot of people I have seen do this type of project use it.

I'm looking for more information on the Aurasound driver so it'd be appreciated.

This project is still in the design stages and I'm trying to get it all figured out before I even order anything.

On the port, what type of material is good?

I'm looking for as much information as I can about LLT and porting and design etc...thank you. :daydream:

Premium Member
413 Posts
That is supposed to be a really good driver. It's expensive of course. If you're willing to spend the money, I don't see any reason not to choose that driver. The alternative is always more less expensive drivers, but in the end that's up to you.

For port material I'd be looking at sonotube for an 8" port. I'd also look at whether a 10" port is feasible since you are building such large enclosures. I haven't modeled this driver in the box you're describing, so I can't make any recommendations on that side.

The CE4000 does come highly recommended. If I were building a subwoofer now and didn't have anything I'd be looking at that amp.

Elite Shackster
1,506 Posts
Well this thread is where I learned all about LLT. From the looks of that driver and the tuning you have in mind the LLT should sound great. A nice benefit of this design is that it acts like a sealed enclosure until close to the tuning frequency so you should keep all of the high quality sound from that driver until down deep. Is on of those crowns enough for 4 of those subs? I'll have to run som WinISD plots, that driver just looks insane.

All I have to say is with a build that big you'd better post it here and show us some pics of the rest of your theater!:R

Discussion Starter · #4 ·
Haha. The main priority in design, like I said before, is low distortion (FR/Group Delay/THD/Phase/Transient/Depth/etc.).

That classifies everything I want from the design. :rolleyes:

I read your build thread and I must say, good job. :wave:

The reason I did not do two drivers in an enclosure opposing and inverted to cancel distortion and non-linearities is because the enclosure weight simply would've been too high and I couldn't have four subs which I can optimally place using the 25% Solution (maybe I'll explain later). With how the design is progressing, I'm estimating distortion levels lower than 1% above 30hz in the mid 120dB range and 5% in the 20s and 10% in the teens. If I pass the linear range of the coil at all, the distortion is going to skyrocket to 40%+ probably, hence the reason for so much headroom to eliminate that possibility. The power compression is very low with these drivers.

The Crown CE4000 is rated for 3600w on a 220v feed and it has been tested to do closer to 4000w. 1300w input gets full excursion at 20hz (with my local air pressure added to the equation)...it increases to 1700w at sea level. It can take full power from 12 to 16hz however...which is probably 130dB with room gain (adding 4dB). Pretty much if I ever get the amp to clip, I'm trying to damage my neighbor's house! :yikes:

The listening room right now is 3000 cubic feet. It will change later on most likely.

My theater is some cheap speakers and JBL 4311s powered by a Pioneer Elite Model 91, nothing special. I'm working on that though.

The truth is, construction probably won't begin until late January to February due to budget constraints, but I need to have a SOLID design down before I start.

I will make sure to post it when the time comes, of course! :T

Discussion Starter · #5 ·
Since the budget is like it is right now, I'm not really going to be doing much. As soon as things kick into gear, I'll be posting here more.

Discussion Starter · #12 ·
After seeing what you said, I e-mailed AuraSound.

And they replied extremly fast (within a couple hours)!

They said they had quality problems at their current factory, so they switched and have starting producing new drivers again.

I wish to get the money one day. :whew:
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