Originally posted by Diabolik
However, it does not go lower as your own graph demonstrates.
Look at the falloff on your ported box vs. sealed. The sealed box clearly goes lower,
what? at 15 hz? who cares? your nit picking the ported box clearly goes lower look at the graph look where 0 ref is the ported box is making about 5db more than the sealed box at 40 hz and about 4.5 db more than the sealed box at 34 hz (the f3 point for the ported box) how can you say it is not going lower? it clearly shows it on the graph. maybe i should explain it better? the ported box has more output than the sealed box at all frequencies between 15 and 110 hz. that means it will play or emphasize the low frequencies better than the sealed box. to the listener the box will appear to play LOWER with respect to the sealed box. don't try to play on the words to make yourself sound right.
but the ported box is louder above 20Hz. And look at the cone displacement graph. There's no way that ported sub is producing a clear sound below 20 Hz. I realize that 20 Hz is not used much, but I am just saying that a sealed box will produce it much more clearly than ported, which means it is capable of a lower frequency response. Every sub manufacturer I've ever seen says this in their manuals. I may have been wrong by saying a ported box can't go below the tuning frequency, but I am not wrong in saying that a sealed will go lower without distortion.
yes once again your wrong.. any sub that has less cone movement will have less distortion. but this is only true if the sub goes beyond it's xmax (linear cone travel limit, this is usually defined as the point wich the coil leaves the gap. as long as the coil is moving within the gap the responce is very linear and minimal distortion.) in this example the 2 designs do not match each other untill 22hz. if i redesigned the box i could easily tune the ported box to give a flat responce with no peaks by tuning it to about 20 hz then all the cone movement would be far less and even more controlled until it fell below 12 hz
For SQ, you want a smooth response, which the ported box simply does not give as well as the sealed. if the opposite was true then a sealed box would never be used for SQ, which it almost always is.
your right about that if your compeating in a SQ contest and are under the watchfull eye of the RTA meter you want a perfectly flat responce. only a sealed box will do that unless you tune a ported box to have a roll off frequency of 45hz (the point at wich most cars produce cabin gain) but in general sealed boxes tend to do this almost automatically no matter what size you build them.
HOWEVER if you have ever listened to a perfectly flat responce i as well as 90% of the people in caraudio will agree it sounds like crap. most people prefer a system with a little more bass or bass heavy. fact is most people like a lot of low bass and that is where ported boxes come in.
there is talk that orginizations like Iasca will be rewriting the rules of SQ contests. people are asking to take out the RTA as well as not allow judges to see what equipment is in the car before judging. too many judges tend to rate the sound of a system based on their opinions of the equipment used as well as the box type and or setup. my point being if a flat responce is only used to make points on a meter what does that have to do with the way the system sounds? people should be allowed to set up their system to where it "sounds good" not what an RTA meter thinks should sound good.
if you like a flat responce then go sealed by all means.
possibly in your experience with ported boxes is that your box is still too small for the sub your using. i went to your webpage and saw your install. it is hard to say from the pic but i know from experience that L7 subs require a very large box to get correct tuning in the ported boxes. yours looks too small and i would not be suprised if it does not go lower than a sealed box. it looks to me more like a SPL box because it would have to be tuned pretty high in that small of a box.
Indeed. Perhaps you can do some things to those boxes you are designing to mess with the physics, many people do that, but all things being equal with boxes built to manufacturers spec, sealed boxes have a better low end (sub 20Hz) response than ported, they are better for SQ because of the smoothness of the response curve, however are not as efficient as ported boxes.
I have ported and would never look back. At least not with my 12L7, that thing is great ported.
-Diabolik
yes i would agree L7 subs suck in a sealed box i have run several simulations with them and they have a nasty responce curve in sealed boxes. ported is a much better choice with them and it is mostly due to the fact that they have a low BL product (magnetic strength in the voice coil gap) because of a weak magnet power they don't respond well to small sealed applications because the magnet can't produce enough force to move the massivly heavy cone they use and in a small box with so little airspace.