It is time, after much time spent perusing these and other forums, to venture into the world of DIY speaker building. To keep things simple, I am starting with subwoofers. In a nutshell, I am wanting to build (4) Sonosub LLT subwoofers (hence the title). For starters I will give as much information about where I am in the build process, but I would love some feedback from more experienced builders prior to finalizing the design details. If I’ve got something all wrong, let me know. I will be taking the whole process pretty slow as I am obviously doing this for the first time. Also, I have a job and am a full time student. I’ll try to include a bunch of pictures to keep things interesting . . .
In terms of properly designing a LLT, I have attempted to keep everything from this write up in mind:
Overview of important purchased materials:
(4) Dayton RSS390HO-4
Crown XLS 2500 amps
Mini DSP Balanced 2x4 (2-way Adv plugin, UMIK-1 and REW)
(2) 12’ Sections of 18” Sonotube
(2) 10’ Sections 6” SCH40 PVC Pipe
Overview of Design:
By pure coincidence, it seems that the RSS390HO works with nearly the exact criteria laid out in the above link . . . I had actually ordered parts before ever reading that write up.
Room Volume ~1900 cuft (odd shape, L-ish with an octagonal section)
Internal Volume (less port volume): <=250L
Tuning: 14 Hz (15 Hz would increase 1st port resonance if need be, currently 171 Hz)
HPF: I think inevitably I will require some filtering in case content reaches below 13Hz
80% movies/20% music.
I only have so much sonotube for (4) enclosures, so to maximize the internal volume of a given layout I wanted to reverse mount the driver. This orientation is more space efficient than a typical sonosub layout that essentially has a riser to keep a down-firing sub off the floor and would net about 7L in volume. Also, the Drivers have nice wire terminals built in, providing easy access outside of the enclosure. A reverse mount should also provide better cooling to the coils . . . though I don’t think I will be pushing them that hard.
Side note: The Dayton HO were chosen over the HF to produce relatively smaller footprint enclosures, which is more of a concern with (4) subs . . . In this way I was hoping to end with more even distribution of bass across all listening positions rather than absolute lowest extension.
Otherwise, the construction will be pretty typical with big round endcaps and flared ports. If you have used the “Sonosub” design software, the animation provides an excellent representation of what these things should look like. Software: http://www.subwoofer-builder.com/sonosub.htm
I was thinking I might also put in an internal brace to hold the port inside, rather than have it’s only support be the top cap. This would also provide a means to separate any stuffing from the driver.
This is what WinISD predicts without a HPF, excursion will always be an issue below tuning . . . so I assume I should plan on a HPF just in case?
This is the curve with a 2nd order butterworth HPF at 15 Hz, this seems to still increase group delay around 20 Hz . . . I don't know how much on an issue it will be. Btw, when I was playing around with WinISD I have the signal set for ~280 watts.
Will reverse mounting the driver actually produce any noticeable variance? I would assume the backside of the driver actually has slightly less Sd than the front, equal or less than the area of the dust cap . . . would this cause the port output to be greater than WinISD predicts? Or is the difference negligible?
How much of an issue will 1st port resonance of 170hz be with ~80 Hz crossover? Pushing the tuning up seems to help a lot with this, I am just wondering which is more important: Lower tuning or port resonance?
Given that LLT designs plan ahead for room gain, is it worth while to do preliminary testing using REW and my existing subwoofers to determine where room gain begins and attempt to fine tune the enclosures to align with this information?
Denon AVR-910W (MultEQ only)
2x Dayton SUB-1200
2x Fluance SXHTB speaker systems:
Center: SXC Center
FR/FL: Classic Elite Series 2-way
SR/SL: Classic Elite Series 2-way
SBR/SBL: SXSS surround speakers
Quickie Review of current setup:
Sub-1200s are being replaced obviously, but were great. For a total of $240 shipped, the SUB-1200s really are value kings, easily whomping any “HT in a box” subs. The SUB-1200s did most everything I asked until they approached the infrasonics, where they promptly called it a day and went home. I have a very oddly shaped room, which is why I am doubling up on subs, and increasing size/power. When in doubt, power out?
The classic elite floor standing speakers are the shining gems of the main speaker package. Similar performance to something along the lines of the Klipsch R26F for less money, and you essentially get the smaller surrounds to fill out a 7.1 for free. The floor standing units actually impressed me, the surrounds get the job done. As a package the biggest complaint is the center channel. The center, in no way, keeps pace with the larger units. I will most likely replace the center with something from DIYSG in the future, as the hobby continues to grow.
(I use a 32" monitor, if my pictures are still too large for some people let me know)
These are the spring terminals I figured I could use with a reverse mounted driver. They have seemingly stiff springs in them.
Topside of a driver, if you somehow haven't ever seen one. 3 more in the boxes behind.
Something I learned during this process: the only place in my house that will fit 12' sonotube was the living room. These things are tall . . .
Also, for those of you with access to Menards, at least in northern Illinois they can order many different sizes of Sonotube.