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downfire questions

2550 Views 24 Replies 6 Participants Last post by  Jstaguy24
i think I've settled on going with a downfire sub box in my suburban for my 2-15's. I'm going round ports so i can change tuning if needed. but can't decide where to aim them.
1- aimed down with subs
2- out the back towards rear doors
3- out the sides towards each side panel

also should i carpet under the box? it will have deadener and probably insulation for road noise and vibration. but would carpet be of any benefit?
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Of the choices, I'd say towards the rear doors.

Towards the sides may not allow for enough clearance for the ports and could choke them. Similar may be said of downward as well, though I have no idea what sort of clearance you're shooting for.

I'd vote for NO carpet, you want a solid surface for the subs to load off, not an adsorbent material. Place CLD Tiles in the floor of the truck to reenforce the surface more so, but I'd try without other materials for this location at this time.
I'm running a single Polk MM1540 in a sealed downward firing enclosure and at this point in time, I have 3.5" legs on the enclosure. However I will be testing out 3.75" and finally 4" in the spring.

Still, this is more so my best guess, as I've not dealt with many ported setups.
Seems another member, who's ID suggests they own a Yukon, recommends rear facing ports, so that suggests experience with such.

However, if I may, YukonXL04, have you ever used downward facing ports with a downward firing sub? I know JL Audio has slot ported enclosures designed with downward facing port and subs. Can't say I've ever heard one in such a position though as both I've heard were in trunks of cars that didn't have the clearance for such a position. Ended up with port and subs firing rearward.
It's in my 99' Cavalier RS coupe. Not a large car, so it doesn't need much, besides, I'm not much of a bass head.

I've only had it in the car for a couple weeks now and I'm not feeding it much power. At this point in time, it's wired it to a Kicker ZR120, which i believe isn't able to produce much more than [email protected] ohms (it's rated at 120RMS). However, I set the gain for maximum clean power with a -3dB 50Hz test tone using a DSO Nano 201 with the master volume at 35 (loudest I listen to the stereo) and the sub volume at max level 10 (no boosts and flat EQ). Currently, I tend to listen to the system at level 30 and the sub volume is at -5 for break-in. I did crank it up to 35 and +10 after a few days for a matter of seconds just to see what it'd do. Was playing some Tech9Nine and it produced a fair amount of output (and this was with around 1/3 rated power). Not the most I've had, but ample for my taste. I feel 400RMS to it would be plenty for me.

Most I've had in terms of output would have been a Kicker F15c I ran very briefly in the early 2000's. Buddy built the box and set everything up as I didn't know **** and he was into the competition scene (He was running (4) 10" eclipse 500RMS subs in a sealed box on rated power in a 92' Cherokee. Claimed he hit 143.something when he took it to comp and got second). Think he built a 3.5cuft enclosure tuned to 32Hz, or at least that's what my memory keeps thinking. Gave it around 400RMS. Rattled my 88' Tempo like CRAZY. Sounded like **** with everything but Rap/Hip Hop, but even then, it rattled everything so bad it was just unbearable. After a week, the novelty wore off and I began missing my pair of JL 10W0s. Much cleaner sounding subs, just didn't hit hard at all and I thought I wanted to try and keep up with my high school buddies. Live and learn.

Never ran more than 800RMS setup and most have been between 400-600RMS, again, I'm by no means a bass head.
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I'm running my second downward firing enclosure as of now, but the first was a generic one for a F-150. I have a 99' Cavalier as of now, so I built one that I'm experimenting with on height, or should I say I will be experimenting on height.

As of now, I have 3" clearance and I plan to go no lower. Sub has been used for roughly three weeks and should be broken in by now, so I'll soon begin changing out the legs to test the effects. Don't have a lot to measure sound at this time, pretty much just my ears and a relatively inexpensive Radio Shack SPL meter. Need to buy a decent mic and get software for my laptop to do a more thorough job with testing though, but...

Anyways, I'm running a Polk MM1540 and it's (temporarily) wired to a Kicker ZR120, which I set the gain with a cheap O-Scope for maximum clean output using a 0dB 60Hz test tone. Within the first week, I tried playing the sub at max levels and it seemed more than enough for me. Now, playing at master volume used when gain was set along with 0dB on the sub volume (HU goes from -10 to +10), any song that has any sort of respectable mount of bass rattles my car badly (REALLY need to deaden the car now). Tried playing at max volume and guess what, my rear window is no longer sealed. LOL

So, anyone got any idea what adhesive is used for holding the rear window in place? The damn thing now rattles all the time when driving. :mad:
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Enclosure well braced, given you plan to mount amps to it?

One more thought though, you say the front of the enclosure will be your amp rack. This means the amps will be mounted vertically (less efficient for most amps to properly dissipate heat) and being sandwiched behind the rear seats, have you some sort of force air cooling?

Just trying to think of worse case scenarios that may arise. It'd really suck to have done all that work, which looks good by the way, only to have an amp fail due to excessive vibration (which you seem to have addressed) or regularly go into thermal protection.
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