Speaker package for the missile

Discussion in 'Car Subwoofers' started by Blue Missile™, Mar 11, 2011.

  1. Blue Missile™

    Blue Missile™ New Member

    I got the shop turned back around to wood working, so the rear console was first.
    Because I have gone to alot of trouble to insulate the trunk from the passengers compartment, sticking any sort of speakers back there makes no sense. Come to think of it sticking speakers back there never made any sense to me if you had a back seat.
    Also while I will have a very nice sound system, I will not be putting thousands of watts into this small space.
    I have aquired 2-6"x9" triaxiels for the package tray, 2-4" Bi's to replace the 4"x10"in the dash, and 2 -4" Bi's for the door panels, Im not inclined to put speakers in the kicks.
    All of those are fairly straight forward.
    For the Sub-Woofer frequency range I was originally going to be running 1-6.5"MB-Quart. For you speaker guys it has an Fs=34Hz.
    It only takes 150Watts RMS, and should out perform 3-12" 150Watt speakers. This is from 20—160Hz.
    One of the things I have been doing for the past 20 years is designing and building large front of house systems say for 250 people and up.
    The secret to getting great sound, is efficiency.
    There is a design called a folded horn that if built correctly will produce 5 times the SPL at 30% of the Wattage using a conventional box.
    Now there are folded horns and there are folded horns, what makes one efficient is the lack of square corners and a proper horn flair for the frequencies desired. The ones I build are based on a design called "snails". A pair of subs for large venues takes 60 hours to produce.
    The single cabinet I made for the car took 16 hours.
    They are a real PITA to make which is why you can’t go out and buy them.
    Here are the pics, first is the pile of parts for the one box, next is the bottom, then the throat and duct assembly, then one side with the bottom & back attached showing the gussets for the corner pieces. the next three are views with the final side missing and then one of it in place.

    There were some questions on FABO about loaded systems, here is my reply:
    In a 'loaded' system, the throat is physically as close as possible to the driver. That second 'ring' around the opening is for the flexible surround to operate within. The diameter of the opening is roughly the radius of the driver.
    In the larger enclosures there is even something called a 'phase plug' which further restricts air movement and loads the driver even more. The depth of the acoustic passage is usally equal to the radius of the throat and flairs out in width first then in both directions. The design does not allow for reflected sound to get back to the driver. The ports cause the sound created by the rearward movement of the cone to have to travel twice the distance as the original sound and enter the horn behind the original sound further reinforcing it.
    The reason you go to all the trouble of eliminating hard corners is to minimize the reflected sound within the 'air stream'
    The other reason you create one large horn is to emphasize the low frequencies, the higher ones self cancel against the walls of the horn.

    A quick update, no arrows and diagrams just data.
    I put a driver in that a fellow FABO member got for me out of SA. While the enclosure worked as expected the driver did not. As it turns out what the Germans call a woofer doesn't make it so.
    For you audio guys:
    I re-crunched the numbers for the driver and while the Fs looked good @34Hz, the Vd did not.
    I know for the rest of you VD is never a good thing
    Vd in the audio world is the volume of air the driver moves per cycle.
    So I ordered a driver with a Vd 4 times the original.
    To help load the new driver I did install a phase plug. This restricts the flow by roughly 60%.
    Pic attached.
    It was also painted black, and the exterior was covered in carbon and I put a padded arm rest in place and put it between the seats.

    Andrew
     

    Attached Files:

  2. TheViking

    TheViking Well-Known Member

    quite the interesting approach to low frequency production! I have never delved into the world of horn designs. i always thought that they were better suited for the home enviorment. The design for this single driver is very interesting! It is a whole new world to me. My limited experience in this world relates to the ol Klipcsh horns.....amazing speakers with phenomanal efficiency! I agree totally with your ideas of a great sound enviorment begins with efficiency. i have tried to explain this to many over the years, some understand, some will never.

    Back to your horn design....Now i know a single 6 can do some incredible things, done dual reflex enclosures with them and had amazing results. With a shorter length horn on this design of yours, is it relying upon the vehicles transfer function to enhance the low freqs? Or is designed to interact within the cabin to be part of the horn? Look forward to learning more on this.
     
  3. Blue Missile™

    Blue Missile™ New Member

    Viking,
    Folded horns are used much more frequently for large venues than any where else.
    The current sub cabinets that I built for the sanctuary each have a single 500W 15" driver we are running one on each side of the room flown. They are of the "snail" design and are very accurate down to 20Hz. I have them crossed over at 200Hz. If the keyboard player is not careful, and he leans on his low keys, the speakers actually shake the structural steel in the building so that the Par cans start to wobble on their mounts.
    The volume produced by the pair limits my driving them with about 20% of available power!
    Now the frequencies produced are subject to the flair/length ratio.
    In the case of the center console I only had a limited space to work with. I did not even take the passenger compartment into the equation. Because the single speaker will be limited to a very small bandwidth, and the two 6x9s in the package tray will pick up the balance of the lower spectrum, all I was asking of the sub was that added punch from those freqs.
    The balance of the horn flair and the loading caused by the throat design and the phase plug. produce the increased volume from the driver.
    I hope this helps.
    By the way the driver in there now is a:
    Tang Band W6-1139SI 6 with the following specs:
    140watt MRS
    Fs-38Hz
    effective piston area-0.0140m2
    X-max13mm
    Vd=182cm3
    Andrew
     
  4. caraudioking

    caraudioking Full Member

    that is amazing!!!!!!!!