Firing Subs down
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=31586
Printed Date: July 06, 2025 at 2:21 AM
Topic: Firing Subs down
Posted By: casedeez
Subject: Firing Subs down
Date Posted: May 04, 2004 at 3:20 PM
Is it helpful when you have limited air volume inside the vehicle to fire the subwoofers down? For example, will it be more benifecial for me to fire 4 12's down rather than towards me or the back of the truck? Casey
Replies:
Posted By: Ketel22
Date Posted: May 04, 2004 at 7:31 PM
the only way that would accomplish using less air space was if you ment having the subs inverted on top of the enclosure. if thats what you ment then yes it will help with your airspace problem other wise no. also not all sub can effeciently be fired downwards as stated in many post lately 1 being here. https://www.the12volt.com/installbay/forum_posts.asp?tid=30658&KW=down+firing ------------- Quad L Handyman services
Posted By: casedeez
Date Posted: May 04, 2004 at 9:23 PM
I am trying to find out if mounting my subs downward would increase the performance of my subwoofers DUE to the limited air space inside the cab of my truck.
Posted By: DYohn
Date Posted: May 04, 2004 at 10:47 PM
Down firing will not affect the subwofer's performance as long as it can handle the installation. It can reduce the speaker's ability to handle power as it limits its excursion capability, but that's why the 5% max sag idea comes into play. In general, the only "advantage" to this mounting is making it fit into available space, protecting the woofer cone, and a little potential apparent increase in SPL at lower frequencies since you have forced the soundwaves to travel farther by bouncing the sound off the "floor" rather than aiming the sound towards the listener. This increases the distance the sound waves must travel and can, potentially, sound better at lower frequencies. ------------- Support the12volt.com
Posted By: casedeez
Date Posted: May 05, 2004 at 3:12 AM
Well I came up with 3.1 for the first eqaution and 19.4 for the second one. Is that bad to have 19.4 for the second formula?
Posted By: Ketel22
Date Posted: May 05, 2004 at 4:22 AM
if you did the formulas correctly (they are the same thing just written different) you should have gotten exactly the same thing.
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Quad L Handyman services
Posted By: Paradigm
Date Posted: May 05, 2004 at 8:57 AM
Another thing to consider is the opening or space between the subs/box and the floor. It you place the box to close to the floor, you can cause some issues with cancellations and whatnot. I'm going thru this exact same thing with my setup (still working on). According to JL Audio, the rule of thumb is the opening the subs fire out of must be at least 60% of the cone area of the woofer(s). So be careful with how you set everything up, and you should be fine. ------------- VEHICLE: 2002 GMC Sonoma ZR2
Alpine CDA-7940
AudioControl EQT x2
JL Audio 1000/1
JL Audio 10W6 (originals) x3
Kicker ZR120
Kicker ZR460
Polk GXR-6 x4
Polk GXR-4 x2
Posted By: casedeez
Date Posted: May 05, 2004 at 12:04 PM
What do you mean by opening?
Posted By: Paradigm
Date Posted: May 05, 2004 at 12:29 PM
There needs to be "clearance" between the subs and the floor of your truck. This allows the subs to do their work (move back and forth) and produce sound. To get the box off of the floor, you will need to make spacer blocks around the perimeter of the box or just add so much extra stock to your box dimensions to get the box up. If you use the latter method, you will need to leave one (or more) sides open. This "opening" will need to be big enough to get the proper sound from your subs without wave cancellations occuring. See my previous post to determine the opening size. In my case, I will be using 3 10" subs. Taking the surface area of (1) sub, multiplying X3, then multiplying again X.60, gave me an "opening" of 141.xx in^3. So my box needs to be like 3" from the floor with a width of nearly 47" across. Since I plan on using spacer blocks, I should be more than safe in getting the best sound from my system. Hope this helps. ------------- VEHICLE: 2002 GMC Sonoma ZR2
Alpine CDA-7940
AudioControl EQT x2
JL Audio 1000/1
JL Audio 10W6 (originals) x3
Kicker ZR120
Kicker ZR460
Polk GXR-6 x4
Polk GXR-4 x2
Posted By: casedeez
Date Posted: May 05, 2004 at 12:45 PM
Wow another something learned. On the other hand I heard something somewhere stating that bass waves pass through most materials such as wood and thin metals. If thats the case then would it really matter if the opening was bigger or not, as long as the box was raised enough to account for the cone excursion. You said you got this from a jl tech right?
Posted By: Paradigm
Date Posted: May 05, 2004 at 1:36 PM
Yes, I asked JL Audio about placing my subs firing down toward the floor (since I have JL Audio subs, hehe). They gave me the "rule of thumb" about 60% of cone area, etc. I am assuming that this rule of thumb would apply to all speaker brands, not just JL Audio subs. However, he did say that he knew of a person doing the same setup as mine that only had 1.5" of clearance between box and floor without any adverse effects, but I would still use the rule just to be safe, unless you have time and money to experiment with different setups.
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VEHICLE: 2002 GMC Sonoma ZR2
Alpine CDA-7940
AudioControl EQT x2
JL Audio 1000/1
JL Audio 10W6 (originals) x3
Kicker ZR120
Kicker ZR460
Polk GXR-6 x4
Polk GXR-4 x2
Posted By: DYohn
Date Posted: May 05, 2004 at 2:11 PM
Like all "rules of thumb" they are a good starting point. I've built down-firing loudspeaker systems with as little as 1" between the cone plane and the "floor," and some with as much as 5X the woofer diameter. It all depends on the woofer and the application. Getting it to sound OK is easy. Getting any system to sound its BEST is very hard and requires lots of time, patience, experimentation with different setups and yes, money. It all depends on what you want. ------------- Support the12volt.com
Posted By: casedeez
Date Posted: May 05, 2004 at 4:19 PM
Well, what I want is to get it to sound its best but i dont have a lot of time and money. Thats why im trying to boil it all down right now before I build this box. If not perfect I want real good. As flawless as I can without investing the time and money it takes to expirement. From what I heard from the JL tech guy is that I want at minimum 80% of the cone surface area. This is information he said has come from the engineers. In any case I am taking as many steps as I can to get the information I need previous to building a mediocre box.
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