ibanender

Take all your graphs and close them out, and never look at them again. They ARE NOT accurate. On several occasions I've taken a box, tested several subs in it, written down real data, mocked up those speakers in that box and had VERY different results. One example stated 1 sub would be 4 dB quieter than the other, in actuality it was 2 dB louder. As far as suggestions go, a pair of Sundown SA 15's would work on 1000 watts in it. It wouldn't be the greatest thing ever, but it'd do pretty good for the cost.

They need 60's, or around 35 works too. Below 34 or so craps out, and there is also a dip around 45 hz.

You do realize that 3 dB is twice as hard to accomplish, and 5 db is almost four times harder to accomplish, right? 5 dB is 50% louder. That's more than a little tweaking unless everything was just plain wrong to start with. Some class D amps (mostly cheap ones) have limited frequency response, but I've never seen one that had greater than a 30 hz limitation. If it wasn't that, it was probably a subsonic filter setting that wasn't right OR was a set figure like Kicker's 25's hz. But again, what actually plays 25 hz or below?

Your right, I probably should have just stated surface resistance to the moving air but in this case it is exactly one of the confusing things to Ibanender so I did that on purpose. Just because you are dealing with the requirements to reduce resistance for laminar flow does not describe flow in itself. The point in excessive treatment is just that, to reduce resistance. Why does reducing resistance matter if there isn't flow?

Yes, flow has direction, and if it moves in 1 direction, then quickly changes direction, that's still flow. Flow is not uni-directional, but can only be in 1 direction at a time. Let's say for instance I put something in my port, and I played it for 2 seconds, according to you, whatever I put in my port would be in the same position I placed it, yes? If it's agitated it should be equal movement according to what you're saying. laminar flow   –noun Hydraulics, Mechanics . the flow of a viscous fluid in which particles of the fluid move in parallel layers, each of which has a constant velocity but is in motion relative to its neighboring layers. So now SPL boxes are liquid cooled? Smoothing it makes it louder because of liquids in the box? So you're a bridge engineer now? Yes there was a resonance problem, maybe they should have added more bracing... I bet if they had thicker material, the resonance would have been lower and wind wouldn't have matched that. My comments had nothing to do with amplifiers, which would be apparent if you know what axial, tangential, and oblique modes are. Who's to say you're gonna have crappy response from the enclosure period? You're making the assumption if you don't make the most epic box ever, it won't sound good. What if you have a 50 hz dip, but your vehicle has a 50 hz peak, now all the sudden it's perfect! Bottom line, your quest for perfection is stupid because no matter how much you try to get it perfect, something will screw with it, or it will be so minute it will be inaudible.

A small vehicle, especially a CRX, is the wrong vehicle for that. I'm not sure why you'd want your goal to be playing a frequency that is found in a handful of songs only, but you're probably best off aiming for a 160 @ 30-35 hz and accepting what you get @ 25 hz. That's what is going on in all the vehicles I know of doing at or above a 150 @ 25 hz. Those vehicles have at least 762 sq in of cone area and 15,000 watts, most have much more of both. They're all in full size trucks too.

I helped (and continue to) develop the SA8. I wouldn't do a 3" port. You can run one sealed and it'll be just fine, but that doesn't mean you're getting your monies worth. Ever put 4000 watts clamped on an SA8? We've tested all power levels

That should be fine as long as you don't use a 3" port, that's not big enough. An unfortunate side effect to a small box tuned low with more port area is a long port. Just make sure you aren't tuning below 35 hz, things start to go not good if you do that.

Since I'm the only one that read the original post to know what he is asking for, I'll also provide the answer. 5.25", thanks for playing. How'd I find that answer? A measuring tape and actually having one to measure.

Read the OP, he said 8 subs, wired in 2 groups of 4.

Yes, that will work and it's correct.

Yes, all air is excited, and there is flow. Air moves, it is exchanged. Do you think pole vents and basket vents are there because air is stagnant? No, it gets moved around, that's what cools a voice coil. Even outside of the sub itself, it's not circulating the same dead air. If air moves, there is flow. It can change directions in a short area, but that's still flow. Get inside ANY seriously loud SPL vehicle, look at the box, and tell me there's no flow. We go to great extremes to make sure things are very smooth and gradual. To me, that says different wood species are harder or softer, which coincides with my findings. While your definition is accurate, there are side effects to bracing. What happens when you stiffen a bridge by putting a brace across the lanes a foot off the pavement? Who said anything about 90dB? Why don't you understand that midbass is the challenge and adding sub bass is ultra easy in comparison. No it doesn't. Again you have to address not only the frequency but the damping as well. Adding thickness surely has benefit as you note I even recommended it earlier, but it isn't the end all solution. Sort of like using damper as a blocker. The golden ratio doesn't guarantee squat and is another rule of thumb that is generically not so useful. You also have to do a lot more than not make your box a cube. Symmetry is your enemy. The vehicles "effect" is independent of the box. The only thing you aren't confused by in this post is the long wavelength comment, but inconveniently for you that counteracts your whole accurate reproduction post from before. Better question for you. Why do some people have ONE box that does something and without thinking about the math or reasons then apply all the things they did in that box to every other situation? SQ people get judged at 90 dB, and often listen at that level too. Midbass is easy if you know how to install, or don't have limitations like stock speaker location only. I guess you're talk about dampening factors on amps now too right? Are you suggesting having a rock solid box isn't acoustically good? I'm not confused by anything. Scientifically speaking, the golden ratio has the least possibility of creating a standing wave, on axial, tangential, or oblique modes. Even if you were concerned about a standing wave at say, 35 hz, the wavelength is 32 ft. You'd have to be SEVERAL octaves below that before you hit the standing wave in any box that would fit in a car, so the effects would be minimal. Yes, vehicle reaction does change things as we both agree, so why are you so concerned about having this magically perfect box when the vehicle will change that anyway? And lastly for your condescending remark, those are the people that copy others designs and listen to the first person that will spit information at them. After building 250+ boxes, I can honestly say I know why boxes do what they do most of the time. There are some cases that are freaks of nature and that's when I set out to figure out why. I'm working on that right now actually, and my next test box will likely confirm my findings. It's the anti-music box and you'd hate to apply it to a daily application, but knowing the how and why is what drives improvement. "Winning" on a forum isn't even a real thing. Everybody wins in their own eyes and you can't tell anybody they're wrong if they don't want to learn or assume they know everything. I know what I've done, I know what works and what doesn't, and you can build what you wanna build (what do I care, not my car), but at the end of the day I have something to show from my experience.

I guarantee, if it's the dark MDF, it shares the same lines. You may not have a bundle available to see the markings, or know what the markings mean, so going by color has proven accurate. The port is excited, the box has flow. Throw some packing peanuts in there and you'll see what I'm talking about. Or better yet, stick something in the box anywhere near the port and see/hear what happens. Rigid raises scores, not necessarily bracing.

Because then you deal with the complications of internal bracing? Yes, there are adverse affects. I NEVER use internal bracing. Why? I'm sure bracing in an acoustic suspension enclosure, a 4th order, or a 4th order bandpass wouldn't hurt. Wherever there is air flow, it causes problems. Perfect example (and not the only case), in my S10 I did no internal bracing and made the box 5.25" thick except for the baffle which was 6" thick. If you put ANYTHING in that box, score dropped. I left a drill in the box once and lost over 1 dB. In other smaller box applications, I've heard turbulence from bracing as well. Depending how your brace is, I could see it causing a problem with phase or standing waves. The only bracing I'd deem usable is thick threaded rod. Don't assume everyone is concerned about a "score". Acoustic reproduction might just hit the list as important... While they may not be concerned with a specific number, if they want "loud", that's a "score". Loud is loud, whether it be an ear or a meter. The same way you make a daily system loud, you make it loud for a meter. Your acoustic reproduction won't be accurate if you have turbulence and audible noise from it. Standing waves will give dips or spikes in response, a direct relationship to accurate reproduction. The OP asked about good enclosures not loud ones. There are a ton of people that don't care about loud at all, reference levels perhaps, but loud has connotations that are all negative IMO. If you said linear, flat, capability to blend or something sure, but loud not so much. As for your acoustic reproduction comments, true if you have audible noises it will take away from it but flexing panels will cause way worse distortion than any bracing techniques. Bracing will also help to stop standing waves and alter the inner shape of the box to a less symmetric rectangle which is also of benefit but of course we are discussing subs here which play sounds with LONG wavelengths. A solid built enclosure IS a good one. "Loud" is what you make it. Why do SQ guys have 600 watt front stages, then don't go over 90 dB? "Overhead" isn't THAT much. Having an extra thick box solves the flexing problem and won't induce any other noises. Will bracing help stopping standing waves? Sure, but so will changing the box shape. Don't make your box a cube, problem solved. There is such a thing called a "golden ratio", which should pretty well guarantee no standing waves. Besides, even if you had as standing wave of some variety, you're assuming response is linear in a lab or simulation. What about the vehicle's effect? You shouldn't have a problem with standing waves with long wavelengths anyway, unless your box is huge.

All the 3/4 MDF I've seen lately is TERRIBLE. It's very soft, flexes very easily, and costs more than a high grade plywood. The 2 grades of MDF can be identified if it's light or dark. Dark MDF = bad.

You've got at least 6 months till you see anything new, and as stated, the changes are minuscule and back compatible, so it wouldn't be wise to wait.

Care to explain? I can't think of any way a flow helping structure would act as a brace, and vice versa.

Because then you deal with the complications of internal bracing? Yes, there are adverse affects. I NEVER use internal bracing. Why? I'm sure bracing in an acoustic suspension enclosure, a 4th order, or a 4th order bandpass wouldn't hurt. Wherever there is air flow, it causes problems. Perfect example (and not the only case), in my S10 I did no internal bracing and made the box 5.25" thick except for the baffle which was 6" thick. If you put ANYTHING in that box, score dropped. I left a drill in the box once and lost over 1 dB. In other smaller box applications, I've heard turbulence from bracing as well. Depending how your brace is, I could see it causing a problem with phase or standing waves. The only bracing I'd deem usable is thick threaded rod. Don't assume everyone is concerned about a "score". Acoustic reproduction might just hit the list as important... While they may not be concerned with a specific number, if they want "loud", that's a "score". Loud is loud, whether it be an ear or a meter. The same way you make a daily system loud, you make it loud for a meter. Your acoustic reproduction won't be accurate if you have turbulence and audible noise from it. Standing waves will give dips or spikes in response, a direct relationship to accurate reproduction.

VERY well put!! Now, for this particular question we have done a lot of testing so we have a good bit of experience.. That said, a 180 amp alternator in this car is going to give him about 120 "usable" amps over what he normally has, and with a couple of "good" batteries he should have plenty of adequate power under normal circumstances. The main thing to consider with a big amp like the 3500, is how is it going to be used. Is it in a daily driver that just bumps alot driving around, or is a comp vehicle. Kyles 3500 never pulled more than about ~100 amps at .5 on music at say 3/4 volume. On tones at .5 at high volumes, it may touch 180 BRIEFLY. In hours of testing, we NEVER saw over 200 AFTER we put a 270XP with a 15.1v regulator in it no matter how hard we pounded on it. Remember, music is dynamic and even though you may have a 3500W "RMS" amp, your dynamic load of the amp will almost NEVER exceed 70% of its rated power. If you calculate it to the letter for power consumption, 3500/15 15= 233 amps. 233/.8 (effiency) = 290 amp max power input required to make an actual 3500w of output power. Now, take 290*.6 (dynamic avg MAX current requirement on music) 174 Amps, which is the absolute MAX necessary for 3500 actual produced watts, which you will only see MAYBE 25% of the time. Will a bigger alt power it better, absolutely, no question about it. Will a 180 amp alt power it ok 90% of the time, no question... I'm trying to make sense of these numbers... I blew a 350 amp fuse with a 3000D at .5, at full tilt with 4 yellow tops the power wire from my alt was clamped putting out 170 amps of current and I still had voltage drop into the 11's on the amp inputs.... not doubting, just seeking information crazy...i ran a 200amp fuse with the same amp and nominal load AND voltage, and never blew the fuse{never have}. that was on a 75 amp stock alt and one 100ah batt awhile back. i now have an h/o alt and 2 of the batts and dont go lower then 12s now, still on that same fuse haha Not all fuses are created equal, and I'd put money on you having a higher impedance rise.

I wouldn't go that far, because there are subs that are insanely inefficient and insanely stiff that require 3000+ watts to be useful. Then I'd look for different woofers. But he said the amp would be more than enough power for any sub......

Because then you deal with the complications of internal bracing? Yes, there are adverse affects. I NEVER use internal bracing. Why? I'm sure bracing in an acoustic suspension enclosure, a 4th order, or a 4th order bandpass wouldn't hurt. Wherever there is air flow, it causes problems. Perfect example (and not the only case), in my S10 I did no internal bracing and made the box 5.25" thick except for the baffle which was 6" thick. If you put ANYTHING in that box, score dropped. I left a drill in the box once and lost over 1 dB. In other smaller box applications, I've heard turbulence from bracing as well. Depending how your brace is, I could see it causing a problem with phase or standing waves. The only bracing I'd deem usable is thick threaded rod.

I wouldn't go that far, because there are subs that are insanely inefficient and insanely stiff that require 3000+ watts to be useful.

Because then you deal with the complications of internal bracing? Yes, there are adverse affects. I NEVER use internal bracing.

Do you also refer to sealed boxes as "acoustic suspension" all the time? That would certainly lead people to believe you feel you have superiority. Wouldn't you WANT it to act like a horn? You'd gain lower end extension and efficiency. You can have too short of a port, depending on the tuning frequency, but I don't think there is such a thing as too long. You always have proper wavelength reverberation.

But if it was corroded, it would be right on top and not in the connection! Yeah, I've said the same thing, then followed by "did you take the terminal off?" and they go "why would I do that?".