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New member Username: RedskinPost Number: 8 Registered: 12-2003 | Having read many posts on many bbs about cheap empty bandpass boxes, I decided to conduct a bit of research to find out if their performance with a variety subs really would be as dire as everyone predicts. I will say from the start that I was firmly in the "they must be crap" camp as I started this project. To start with I was going to test 10 random 12" subs in several different boxes but as I began to get into it I decided that my life was just to short. I have therefor limited myself to 3 subs and 1 box but I will give you the rough results from myfirst run with all 10 subs in a different box. To be able to make an informed choice about which sub will work in a cheap box you need to find out some info on the box you have in mind. I found that all of the boxes I looked at on ebay did't have enough info about them and neither did the sellers, so personally I would avoid these. To find out if your sub is going to work you will need to find out the volume of the ported chamber and the volume of the sealed chamber and the diameter and length of the port(s). You will also need some box design software. Don't worry the software is free and can be downloaded from www.linearteam.org It is their WINISD pro that I have used in this project. When I started this I ran all 10 of my subs on this software using a box that I found at the SUBZONE to get an idea of what each would do in this box. The results were quite suprising in that 4 out of 10 actually worked in the box quite well, unforunately the other 6 didn't do so well and one was so bad it hardly gave a response curve to look at. It was after I had done the first run that I realised that I hadn't taken into account how much of the chambers volume would be taken up by the speaker and what difference there would be by mounting the speaker into or out of the sealed chamber. DOH! So that is when I decided to shorten the test. The final test used a Shiva 2, Pioneer W304c and a MTX T8124 all 12" drivers in a Q-Logic QB112 box. I ran all three subs through WINISD with the speaker facing into the ported chamber (spf) and with the speaker facing the sealed chamber (spr). I the thought what about if you could change the port length would it help to give a better response, so I tried that as well both ways and chose the best. Oh well here's the bit you've read all this way to find out.............. Shiva 2 spf -3db 33hz -3db 82hz slight hump at 42hz spr 33hz 92hz slight hump at 40hz both these curves had humps that might not sound to go but if you mount the driver facing the ported chamber and shorten the ports to retune the box it was easy to get a nice flat curve with -3db points at 36hz and 106.8hz. So in this case the cheap box works well. Pioneer W304c spf -3db 37.7 -3db 71 spr 34.5 59.4 both of these curves were garbage really ineffcient and with a narrow bandwidth. But with a bit of retuning the results were great. Once the port was shortened both ways of speaker mounting looked good. So with a shortened port and speaker facing into the ported chamber the -3db points were 40hz and 93.5. You can bump the upper -3db up to 104 if you face the sub the other way but lose a bit of gain. Yet again the cheap box wins. MTX T8124 spf -3db 31.3hz -3db 88.4hz spr 30.7hz 91.3hz Using spf mounting gave a big hump in the curve, not good, but switching the speaker around gave a bit of band width and flattened out the response curve. This was good but could it be made any better. Yes it sure could. Just by shortening the port and with the speaker facing the ported chamber the gain went up, the curve got really smooth and the bandwidth increased to give -3db points at 33.2hz and 101hz. This was the best combo yet. Well there you have it I have taken 3 random subs and 1 crap box and the results I got seem amazing.I think we can safely say, as long as you model the box and sub combo on some design software just to make sure you don't get a lemon,that cheap ready made boxes are a possibility. Of course you could make a better box by giving yourself total freedom when it comes to box size and tuning but if your woodwork skills are worse than useless and you rather skip much of the technical stuff the in my humble view cheap boxes are ok, as long as you avoid the really cheap stuff that you can't find specs for. I never thought I'd say that. p.s. the sub/box that failed so misrably in my first run would have been $200 down the drain so make sure you check all combos with some design software before wasting your cash. |
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New member Username: GlasswolfPost Number: 259 Registered: 12-2003 | real world results won't always equate to the same thing as what your PC is telling you, since WinISD doesn't account for vehicle acoustic dynamics. also note that aside from the curve issues and high roll off points of a bandpass box that make it sound like crap to begin with, the main issue with these prefab Qlogic type boxes is the construction and materials. They suck. If the box was good, it'd be no less than 3/4" MDF, it wouldn't use 1/4" plexiglass for a window in a load-bearing panel of the enclosure, lending itself to resonation or box flex, and it'd be well-reinforced and cross-braced. These are all lacking from the prefab box market. They are made like a $20 box, and that's about all they are worth, regardless of what the software may yield on a screen. Granted, though.. some people are happy with those cheap boxes, a couple of Sony subs, and a Boss amplifier with lamp cord from the fuse box to power the amp as well as wire the speakers. To them, hey, I won't argue. there's no point. |
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New member Username: RedskinPost Number: 9 Registered: 12-2003 | Hey you've got to start somewhere, I understand that most design software or calculator methods of speaker design don't account for room or car response and the rising rate of incar response can lift a falling bass end but I'd rather have my system look good on paper before I cut the wood. Coming from the land of the metric unit I got my fractions mixed up assuming 5/8 was bigger than 18mm. I was just dissapointed that these boxes weren't flocked or mirrored on the inside but prehaps I,m expecting to much. |
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New member Username: GlasswolfPost Number: 278 Registered: 12-2003 | considering they sell for cheap, yeah that'd be a lot to ask. haha as for vehicle response, again, true. you have transfer point, cabin gain, and the vehicle's resonant frequency to figure, as well as vehicle damping which will help, too. But I agree, the more you research it first, the better. good job on the boxes though |