Current 18" options for LLT-Big Sonotube

[Mike P.]

Ports up to 36 inches long have been used with no problems.

[SteveCallas]

Here's the nieghborhood I'd be looking at for each driver:

Mach5 = 365 liters with three 4" ports 32" long each, yielding ~15hz tune

FiCar (dual 2ohm coils) = 625 liters with one 8" diameter port 26" long, yielding ~13.6hz tune

SS (dual 2ohm coils) = 600 liters with one 8" port 29" long, yieldng ~13.5hz tune


Tranfer function magnitude is just a static FR - use it in the beginning of a design to help narrow down volume and tuning. Once you like the FR, add some power in the signal section, and then tab over to spl, excursion, and port velocity to make sure everything looks ok. It doesn't matter if your excursion goes over claimed xmax with high power, I was wrong in my early LLT explanation about amp limiting. Just as long as you aren't already grossly crossing xmax limits before reaching acceptable output levels, you will be fine. All three options should be able to get you to 115db peaks indoors using a dedicated EP2500 without much trouble as long as you aren't sitting extremely far away from the sub.

[Bill 3]

Ok guys, here are the graphs with the correct numbers for all drivers (I hope), Using the volumes and frequencies that Steve suggested and using 750W (due to a single Behringer EP2500).

Thanks for all the help and suggestions and corrections.

Bill

[Bill 3]

Here we go

I will not add up the constants like amp, MDF for endcaps, and the rest of the building supplies. Btw, only 24" and 30" are the only sizes available locally (no 26" or 28").

SS: 30" x 12' Sonotube ($140) + 2 of RL-p18 D2 ($780 plus ship or $860) = $1000

FiCar: 30" x 12' Sonotube ($140) + 2 of Q18 D2 ($618 inc ship)= $758

Mach5Audio: 24" x 12' Sonotube ($95) + 2 of IXL-18.4 ($250 inc ship)= $595

So, if you ignore the $ difference and not worried about size, would you prefer the SS with the SPL advantage below 20Hz or the Fi with the SPL advantage above 20Hz.

Looking at $, to me the Fi offers more bang for the buck over the SS, the question now becomes - does the lower tuning and higher overall SPL gives the edge to the Fi over the Mach The size advantage is nice, but not really that big of deal and the $ difference isn't a deal breaker either. Sure wish I could audition.

[SteveCallas]

I think the Fi Q hits the sweet spot - you're getting more displacement than the Mach5, are able to dig a bit deeper, use more port area, and have a more damped driver. Keep in mind that the rolloff that shows up with your Fi model is a bit exagerrated due to the way WinISD models inductance and because your vertical scale is quite small. When built and measured in real life, all 3 options will have a relatively flat FR across the spectrum.

[Mattlock]

SteveCallas wrote:

I think the Fi Q hits the sweet spot - you're getting more displacement than the Mach5, are able to dig a bit deeper, use more port area, and have a more damped driver. Keep in mind that the rolloff that shows up with your Fi model is a bit exagerrated due to the way WinISD models inductance and because your vertical scale is quite small. When built and measured in real life, all 3 options will have a relatively flat FR across the spectrum.

For what it's worth...I built my sonosub with the Q18 and have been extremely happy... Here's my build thread:

http://www.avsforum.com/avs-vb/showthread.php?t=938083

Here's my measurements thread
http://www.hometheatershack.com/foru...surements.html



Matt

[Bill 3]

Thanks for the input guys. I have more or less decided on the Fi and your input confirmed it. Kind of waiting on Scott (Fi) to get back with me - hopefully soon since it looks like I will be sending $ his way.

Looks like other than a few building materials I will get locally, I need to get an amp bought. Probably going to be Guitar Center online for a refurb EP2500.

Looks like I am copying Mattlock.

Thanks again,
Bill

[Mattlock]

Bill 3 wrote:

Thanks for the input guys. I have more or less decided on the Fi and your input confirmed it. Kind of waiting on Scott (Fi) to get back with me - hopefully soon since it looks like I will be sending $ his way.

Looks like other than a few building materials I will get locally, I need to get an amp bought. Probably going to be Guitar Center online for a refurb EP2500.

Looks like I am copying Mattlock.

Thanks again,
Bill

You won't be dissapointed....look forward to seeing your progress...you may even convince me to build a second twin to sit beside my first one..

[Bill 3]

Q18's and EP2500 have been ordered. Sonotube and MDF have been aquired. No turning back now.