Dave's Dual RL-P18 Sonotube Design/Build Thread

[Avus_M3]

Before I get into the discussion, first let me introduce myself...my name is Dave and I am a bassaholic -j/k. Anyways, I have talked with some of you regarding your dual 18" setups namely BTP, Scotty, SSabripo, and I followed Steve Callas and his thread for LLT's explained. BTW Mike @ Sound Splinter is great to deal with! He was fast and courteous for all my questions! Like others have said: Pics don't do these drivers justice!! These are monsters!!

After much research and insight from members here I have decided to head to the dark side and setup a dual 18" Sonotube LLT. For subwoofer selection I picked up (2) RL-P18 D2's with each wired for 4 ohms. For power I will be running a Crown CE4000 which puts out 1200w X 2 @ 4 ohms. Use will be 50% H/T, 25% music, 25% gaming. Oh, it will be running on a nice 20A circuit BTW!

The Sonotube I will be using is 30" diameter ordered in a 12' stick. The port will be a 8" Sonotube with massive internal/external flaring. Since I have to order a 12' section I am flexible on volume anywhere from the recommended 510 Liters @ 14hz by Sound Splinter (actually need to bump up to 520 Liters because of height restriction from back of driver to port), to ~720 Liters which the length of Sonotube divided by 2 will allow me to go. I know the common accepted values are 650L with a 13.5hz tune.

I do have some questions about the effective volume and tuning. It seems there is little difference from going to a massive 700 liters down to 520 liters -except of the standing height of the towers.

I posted some of my rough modeling in WinISD (I am still learning the program I will admit) using 1000W and a single RL-P18:

[Avus_M3]

Transfer Function Magnitude:






Group Delay:

[Avus_M3]

Apparent amplifier load:






Cone Excursion:

[Avus_M3]

SPL:






Rear Port Velocity:

[Avus_M3]

Rear Port Gain:






Impedance:






Impedance Phase:

[Avus_M3]

Looking at 650L, to me it seems like 15hz is a much better tune for little sacrificed below tuning (it looks like at 11.5hz you lose 3 db) you get more output from 13.5hz – 42hz. So I guess my question is: Is it worth it for the lower tune? I know it provides more protection for the woofer but how much information is even down that low (10 hz – 14 hz)? Here is some of the modeling for 650L using a 13.5 hz tune and a 15 hz tune for comparison.

NOTE: I am not trying to argue various parameters here I am just trying to understand. When I decide to do something I usually always go overkill on everything from design and reliability to power etc whether it be cars, computers, or audio. Things just seem to run better that way

[Avus_M3]

SPL:






Cone Excursion:





Where’s those calculus guys to help figure out what option has more area in the difference of the curves?

[Avus_M3]

Some subwoofer p0rn:

[Avus_M3]

Poll added....so you can select a size and tune.

[Avus_M3]

For those who missed my other thread:

The funny part is I have been straight up with the wifey showing pics etc saying "is this cool or that cool?" She has just been saying whatever sure I don't care it's your thing type stuff. Anyways, when she saw the sub she said "holy sh!t it's going to be that big around (reffering to the sono)?" I said of course not babe and paused looking innocent. "That's 18.4 inches around...the sono's will be 30". Her reaction was pretty funny.

Women...who can understand them? Maybe this will teach her to listen more hehe.

AND

(2) RL-P18's $800
(1) Pro Amp $600
Wood, paint, etc $160
Sonotube Material $150

The look on your wife's face when she gets to see the 18's you ordered and realize that the sonotube is twice as big and there will be TWO of them in the family room:

PRICELESS!!!

[Avus_M3]

I have two questions right now:

1) Since I am running 2 RL's, should I use 2 drivers and double the volume of the enclosure and signal power for modeling?


2) I am still not liking the drop in output when tuned below 14hz but like the idea of driver protection and not having to run a high pass would be great! I am just wondering if it's a non-issue since I am running 2 and could probably easily get away with a really low tune?

[Avus_M3]

According to the modeling the lower tunes increase the cone excursion more than I like. After doing some reading it seems that some like to input a butterworth high pass at 10hz to simulate electronic gear's natural roll off (Bruce IIRC). When I do that is seems that air velocity and cone excursion are under MUCH more control. This makes me a little happier doing the lower tune route (<15hz).

As far as size is concerned I have vaulted ceilings that go from about 9-10ft up to 18ft? I haven't measured yet but it's high so I could get away with either 650 or 700L. I will also have enough sonotube to do either. As for the room it's 21X15.

Here's a printout of the modeling in the Sono Sub program of the 650L and 700L. With either configuration I will have plenty of room to maneuver in first port resonance (255hz & 280hz) and the drivers have a driver to top of box resonance of 56hz & 52hz.

650L:







700L:

[Geoff St. Germain]

If I were using a pair of RL-p18s I'd look at tuning to around 12 Hz and using probably 650 - 700 liters/driver.

The roll-off for the 12 Hz tune and 700 liters/driver is about 3 dB/octave, which will probably be less than the room gain you will get. I had slightly more roll-off than that with my two RL-p15 sonosubs (260 liters/driver tuned to 14 Hz) and they measured flat to around 12 Hz in my room.

[Sonnie]

Very nice build/project thread...

[Avus_M3]

Here's what I get using a 12hz and 13.5hz tune with 2 RL's in 1400L with 2400w and no high pass:

[Avus_M3]

I keep reminding myself that the natural high pass does control this a lot and as Steve says: No one has yet to bottom one of these in a LLT yet. I haven't taken into account any room gain yet because I have no idea how much this affects anything. This is my first DiY of this magnitude and it's been a long time since I have had "good" bass output. This should hopefully net me "stellar" output!

[Avus_M3]

Another idea I had was to recess a circular channel on the bottom end cap facing down and flush in a small blue CCFL ring. That would look pretty **** hot as long as it wasn't to much light. I just want subtle effects. I thought about doing a mirror in the base reflecting the sub but I think it would be too much work...we will see.

[Avus_M3]

Here is one of my towers (Pioneer Elite TZ-F700):



This is why I want to figure a way to run a blue CCFL or led on the bottom...it would match perfectly!

[Geoff St. Germain]

A friend of mine now has the two sonosubs I built and he's put a blue light tube around the bottom of the endcap. I haven't seen it yet, but if I'm over there in the next few days I'll try to remember to get a picture.

As for the plots, one thing to keep in mind is that you want to avoid the resurgence in output at low frequencies. You can see it slightly on the 12 Hz tune and it is more obvious on the 13.5 Hz tune. It is caused by an enclosure volume that is too large for the tuning frequency. I would probably look at 1300 liters for 12 Hz and maybe 1200 or even less with the 13.5 Hz tune.

[Avus_M3]

Here's a quick google sketchup using 650L enclosure with a 34" base and 32" bottom endcap. Nevermind the top end cap I screwed it up and used 30" and don't want to fiddle with it anymore.

Size Comparison (Height):




Looking down 8" port:

[Avus_M3]

I was planning to do ~4" for the dowel length...will this suffice or should I run 5"? **** this is starting to get BIG?!?!?!

[Geoff St. Germain]

Depending on your tuning frequency and the size of enclosure you decide on in the end, you may want to consider using a 10" port.

I think that 4" or 5" should be fine. Of course, any 600+ liter subwoofer is going to be huge. I thought my 260 liter sonosubs were big, but these are going to be something else entirely. I am thinking something like Steve or Sherv's with their 18s.

[Avus_M3]

Geoff St. Germain wrote:

Depending on your tuning frequency and the size of enclosure you decide on in the end, you may want to consider using a 10" port.

I thought about a 10" port but at this tuning it makes the port WAY to long? IIRC something like 50"!!!

I am still learning A LOT here! My wallet wants to **** all you people but I would like to sincerely thank everyone for taking the time to help out and enlighten me. I guess this is the indoctrination into the "brotherhood"? Soon I will also be a member of the SIYS club. I am adding to the first initial though. For me it will be Stand In Your Sub Club

[Avus_M3]

Speaking of ports I am still up in the air if I should use sonotube or go for the "Collo" port and try heating some pvc?

EDIT: I forgot, another option would be to buy one of these bellmouth housings and mold some fiberglass ones off of it?

To cover the top port I am using some earth magnets I found at Parts Express...I have a similar "mod" done to my front license plate except with stronger magnets. No screws and only there when I need it! I will recess the grill so it is flush with the top. Should look killer!

For the end caps I will also cut a channel for the tube to recess into just a bit to make a more flush look. Of course the carpet will mask a lot anyways. Should I go through the effort for this or do you think it's a wasted effort and won't be noticeable? The exterior will be carpeted like most and ends will be piano black to match my existing towers, receiver, samsung, and ps3.

[Avus_M3]

Geoff St. Germain wrote:

Of course, any 600+ liter subwoofer is going to be huge. I thought my 260 liter sonosubs were big, but these are going to be something else entirely. I am thinking something like Steve or Sherv's with their 18s.

Luckily for size I don't think there is a real big difference in apperance. In my modeling I am showing roughyly ~4.25" difference in height between the 650 and 700L size. There is a difference using the suggested 12hz tune on the 650L and 700L though. The 650L brings the FPR right around 193hz vs the 210hz for the 700L.