Before I get started, for reference:
Vehicle-1994 Chevy Caprice 9C1
Electrical - stock, 1/0 from battery to amp, grounded to trunk floor, needs big 3 or more but suffices for now
Amp - Wolfram Audio 2400.1d (has clipping indicator bass knob!), subsonic 10hz, hpf max
Woofers - 10" Orion 2NT, DVC 4 ohm, 500W rms, 1000W peak
Headunit - Pioneer 590IB, LPF 125 hz, HPF 80hz
Speakers - Stock powerd from headunit, Rear speakers faded down to 30%
I just wanted to put together a little write up of my findings from this week. I have been experimenting with some 10" DVC Orion 2NT woofers I got in a trade deal in a prefab bandpass box.
I ran the prefab for a while and to my surprise it sounded pretty good even without the port tubes installed (just holes effectively as long as the wood thickness) having a pretty busted up baffle, and being made from particle board! However, I wanted to see if they could do better in a better enclosure while also saving me some trunk space (not that i care in this car but useful info in general)
Getting into it, I was always curious between the pros/cons of running 2 woofers sealed vs 1 ported. In terms of trunk space, both use roughly the same amount and for me this is main issue with any system. With 2 sealed you get more coil for more thermal power handling, but if you need to send more power you could potentially need electrical upgrades etc. With one ported you gain efficiency, lower cost, and reduced weight, but you might lose DB's or SQ. Do note, i am not a fan of sealed boxed in general. I like the low end boost of ported boxes.
For theory, adding a port to a sealed enclosure adds ~3db. this is a rule of thumb and in the car often results in much more significant gains depending on tuning, etc. Adding a second woofer in a sealed application should theoretically double your efficiency and power handling, but how this translates to SPL is unclear to me, but I would also expect at least a 3db gain, especially when factoring in double the power consumption if running the subs in parallel. So in the real world I can see this going either way for the output battle.
In terms of SQ, everyone says sealed is better, however I disagree with this and have never built a ported box that I thought sounded bad (including in this experiment, more later) and in fact I always like the response curve better from a ported box. Initially I thought it had to be properly tuned to sound better but I found that tuning is actually not that important, amazingly!
I would also like to add that I am still experimenting and willing to take suggestions from others to test various things. I DO NOT HAVE A METER so everything I say about output is based on ear at the head rest.
Both enclosures (dual sealed and single ported) I accidentally built the net volume to the 12" gross volume subwoofer specs, despite thinking they seemed quite big for a 10 i never went back to double check lol. But this was an important learning experience for me as i have never ran a sub off much off spec box size. consequently,
The recommended net volume boxes are (for a single sub) 0.77 cuft sealed and 1.26 cuft @32 hz for the 10", and 0.86 cuft sealed and 1.51 cuft at 31hz for the 12".
The enclosures I built (specs for one sub) in net volumes are 1.0 cuft sealed, and 1.7 cuft at 42/29hz. The sealed box has a divider in the middle so each sub sees it own chamber. The ported box has two 21" long x 4" diameter ports to allow for two tuning frequencies by plugging one of the ports.
When running the dual sealed box I wired the subs in parallel for a 1 ohm load. The single ported was ran at 2ohms. Both setups I was able to drive to clipping without distortion (until clipping) It also seemed as the woofers were over extending once at clipping, though its hard to tell for sure without looking a the subs hidden in the trunk but it sounded pretty bad and muddy.
I built and tested the dual sealed box first. Right off the bat I was shocked at the low end extension, how poor the upper bass response was, and how low the power handling seemed. All of this told me the box was considerably too large but i still decided to build the ported box too big also, lol. Anyways, the output was pretty good, better than the bandpass box the subs came in but I was super disappointed how peaky it was in the low end. I never expected this from a sealed box especially having my LPF setting set so high (i usually cross my subs much lower, like ~60hz) but i thought I built it to spec a the time. Makes more sense now looking back.
The ported box was of course my favorite. I honestly think I like how the port "colors" the sound and theoretically the distortion is less near port tuning since the woofer hardly moves. I really only tested this box at 42hz tuning, as I think I need better plugs. The box was not behaving correctly with the one port plugged with a bunch of rags in a plastic bag. I figured it would just act as if it was intermediate between plugged and unplugged but instead it seemed to cause the woofer to unload and killed the output. Keep in mind 42hz is the highest tuning I have ever built. Previously the highest I built was 35hz. I was very surprised how low the box still went being tuned so high. Didn't seem to unload either even below port tuning. In fact it had more unloading issues at high frequencies.
In terms of output, the ported box did seem a bit louder and the output seemed flatter and overall the bass has more impact. Weirdly the sealed box seemed to have more of a peak (at very low frequencies) than the ported box but the sound was muddy and lacked punch. I suppose this could be from the fact that the enclosure was too large but so was the ported box...
What I learned from this so far is that I still like ported boxes best but I need to try the sealed again with appropriate net volume. Much to my surprise, ported boxes, even significantly too large and tuned high can still yield flat response. I think the tolerances for getting good sound from a ported box are actually a lot larger than most lead you to believe, in fact I would argue that sealed boxes must be built more accurately for proper sound, based on this experiment alone. For me the ported box is way more musical however the dynamic range does seem to be lower, but this could be my settings that I need to tweak.
For my next experiment I am going to displace some of the air in the sealed and ported boxes and see how this changes the sound. I hope you can learn something from this post and can help me to learn more with your comments and suggestions!