Sub placement in my van and what type of box? - diyAudio
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Old 12th June 2012, 01:37 AM   #1
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Default Sub placement in my van and what type of box?

Vehicle in question is a 99 Ford E350 cargo van that I am turning into a weekend camper. Oddly enough (although I have a crazy amount of room) there are few places to put an enclosure that aren't in the way of cargo room or that the drivers wouldn't be in a poor location. (like for instance firing directly at each other.)

Drivers are 2 10-inch Kicker CVR and will be driven by an 800w Kenwood mono sub amp.

My first thought was placing them behind the driver and passenger seats firing backwards so I could get as much distance for the longer waves to form, but they would get in the way of cargo. I thought about building a box between the seats to fire them backwards, but I would need an extra 1.5" between the seats to make that work.

Which got me thinking about isobaric enclosures. What are the drawbacks? Will I get the same basic SPL/SQL from an iso box or is it a whole new ball of wax? I'm a bit out of my league with this stuff.
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Old 12th June 2012, 01:36 PM   #2
bjorno is offline bjorno  Sweden
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Quote:
Originally Posted by curtis73 View Post
..What are the drawbacks? ..
Hi,

My
Your driver works best in a Closed box and if used in tube ported BR box you will run into port resonance issues. Therefore IMO/IME a TL type( OD-TL = Offset Driver-TL or a Nd-TL should be considered if including a port.

An isobaric connection of drivers would cut the box internal volume requirement in half = Useful for drivers like yours as they have a high Qts value.

The expected performance would be very similar like for one diver that requires twice the box volume when compared to a isobaric pair.

Look at the pictures, especially where to place a sub.
I calculated the 'Cargo' volume and if I'm right it's about 7.5 m^3:
Normal 'cabin' gain for a small car wouldn't apply (Full Cabin gain kicks first in below~50 Hz), i.e. a program that can predict small room reflections characteristic's is IMO handy:


Room Response Calculator - Reflective Accumulation Simulation Software

b
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File Type: jpg 99 Ford E350 cargo.JPG (410.8 KB, 101 views)
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Old 12th June 2012, 07:38 PM   #3
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In a cargo van that size the longest dimension will determinn that at frequencies below about 60-70 hz the subs will operate in a pressure response not a wave response so cancellation will not be an issue.

Below this turnover frequency you can estimate approx 12db/octave boos to your low end response.
depending on the mounting locationj of your upper frequency drivers and their capacity to reach low enough you shouldnt have a trouble with localizating the bass to the installed location of the subs.

Port resonance is not an issue in car installations unless tuned VERY high(80hz).

This only occurs where you only wish to achive EXTREMELY high spl at ANY cost.

so:

To make it clear what you require answer as many of the following as you can.
required Db output @ 1m into your space
Bandwidth eg20hz to 80hz +-3db
efficency 90db/watt
Price in dollars
Power available in watts
how many systems including amp channels are to be used
Size of venue.
type of music played?
External maximum dimension?
Deal breakers? maybe highlight these parameters so we know exactly what parameters will make you abandon a design.

The Isobaric design trades efficiency for space.
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Last edited by Etocynned; 12th June 2012 at 07:40 PM. Reason: new infoo
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Old 13th June 2012, 03:56 AM   #4
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Quote:
Originally Posted by Etocynned View Post
required Db output @ 1m into your space
Bandwidth eg20hz to 80hz +-3db
efficency 90db/watt
Price in dollars
Power available in watts
how many systems including amp channels are to be used
Size of venue.
type of music played?
External maximum dimension?
Deal breakers? maybe highlight these parameters so we know exactly what parameters will make you abandon a design.
Required dB = no requirements. I already have the drivers and amp and simply want to make the most of the installation. I would hate to build the box for a certain spot only to find that I have odd gains or standing waves.

Bandwidth = 25Hz would be great, but realistically I think these 10s will drop more than 3dB at around 30Hz. Upper end will be determined in the future. I can stretch or shrink the low pass cutoff a bit to tailor it, but I've yet to choose mid and high drivers. I figured (instead of pushing the subs out of their comfort zone) I would choose mid drivers that are capable of filling in that range properly.

Price = not an issue. Drivers and amp (as well as plenty of MDF) has already been purchased.

Power = Amp is a Kenwood, 1-ohm stable, 900wrms bridged at 1-ohm. I'll probably wire the drivers for 4-ohm total. IIRC, the amp will provide around 650wrms at that resistance.

Type of music = Rock, classic rock, jazz, but I will admit to the occasional times when I pop in a Rap, Trip Hop, or Electronica CD and make a little hum.

I 100% appreciate the technical data, and I'm following much of it, but I'm not as savvy as you folks are. I'd like to find the placement and enclosure type to do that.

Sounds like an iso enclosure would solve the space issue, but I'm not really keen on giving up SPL just to get a smaller box. I'd rather re-engineer the box to keep it acoustic suspension if that's the case.
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Old 13th June 2012, 04:15 AM   #5
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By the way... given the confines of the area between the front seats, I came up with this quicky drawing. At those dimensions, the chambers would give a lackluster 0.79 cuft. Extending the height to 14 inches would give me a more satisfactory 0.96 cuft.

Click the image to open in full size.
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Old 13th June 2012, 10:34 PM   #6
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In a small space the drivers will have the least interference patterns if they are placed either at the front or back of the space, magnet side against the wall. Basically tuck it in a corner and fire out from said corner. This keeps the wall reflection close in phase to the primary wave.
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Old 14th June 2012, 12:41 AM   #7
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I know this is a potential no-no, but what about facing them toward each other and phasing them opposite? Will I lose SPL, or will the 5' between them cause certain frequencies to drop out?
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Old 14th June 2012, 04:06 AM   #8
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Here is another quicky. This shows places that I've picked that would minimize space concerns re: cargo, seating, etc. I can build boxes for in front/behind the wheel wells that fire across the cargo area on either side (indicated by the red and blue arrows) or the previous drawing above would be represented by the green arrows (although this drawing doesn't show the seats and the cabin. It ends at the front of the cargo area.)

Click the image to open in full size.
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Old 14th June 2012, 05:04 AM   #9
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What is the length of the van interior from front to back.
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Old 14th June 2012, 05:20 AM   #10
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Quote:
Originally Posted by Etocynned View Post
What is the length of the van interior from front to back.
Total length is approximately 15'. Unobstructed cargo area is 12'
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