yeah Paul,
I agree with what your saying, although most people don't have a meter to try and "perk up" the sounds that they are missing or lacking.

What dukk talked about has nothing to do with having a meter.

I re read Dukk, and now I need to be schooled, how do you "perk-up" the bottom end of a sub box and sub if your not sure what you are listening for in the first place??? The specs of a sub should by all accounts be tested and labled, and very rarely is the response of the peaked at the bottom end 20-30...So now comes the testing right, keep playing with ports until the bottom perks up to something we can hear???

Sealed boxes roll off early compared tu ported, porting boosts the low end relative to sealed.

That's all he meant.

It's especially important because of whats called the Fletcher–Munson curves that dukk was refering to.

Most of us use modling programs to figure out the details though...
winisd
bassbox

Others simply go by rule of thumb, I might be off but most I think would say for car\music tuning around +-35hz turns out good.

i have a HT 12" sub for a temporary setup. its tuned low im sure.. lower than 35hz and it sound nice.

What is the best SUB for SQ not SPL?

Everyone has a pair of ears and can decide for themselves, but given that home audio is still considered an environment with higher SQ than cars, then it would seem that vented designs are preferred as most high end speakers use low frequency drivers that are in vented enclosures.

Well, this is where you have to get to the point where you DO know what you are listening for. Unfortunately time in the seat and at the table saw are the only true teachers here. As mentioned, box modelling programs help. I used to use TermPro until my license expired and now use WinISD. It's free and very good.

For a meter, if you have an iPhone 3GS or 4, or a 4th gen (I think) or newer iPod touch, you have one. Get the JL audio app. - it's free and has a basic SPL meter, RTA, and other neat stuff on it.

to Bill@wa
I am going to look at a few of the more extreme points of misinformation in your posts to try and provide some clarification.
If the sarcasm of this statement wasn't obvious the statement would actually make sense. The truth is that you can achieve spectacular results listening to classical music with a ported 15" and also techno with a sealed 8".
This actually represents a number of issues.
1) You don't want a sub with a flat response, you want an installation with a balanced response curve. The metered output of a sub on the spec sheet has very little impact on the final product you will get. The enclosure, cabin and EQ all work together with the sub itself to determine what it sounds like. The exact same sub/enclosure/setup in a Corolla will sound completely different in a 300M (setup being the crossovers and EQ)
2) The response you should be looking for will actually increase towards the subaural range (below 30Hz) to compensate for our natural roll-off in that region. Flat on a meter will usually sound less than ideal to the ear.
3) A SQ setup would only run the subs up to 120Hz crossover if the subs were mounted in the same location as the mids. Typically you will see the sub crossed over as low as the mids can handle (usually between 50 and 80Hz) You can begin localizing sound around 80Hz so you would mess with the staging and transparency if you had a speaker in the trunk handling material into the 100s
Please understand that saying the size of a subwoofer affects it's SQ is completely false. Your assertion that a 15" will give too much bass only proves that you have never listened to a decent SQ setup that uses a 15" sub. How can you miss the obvious reality that the output of the sub is easily regulated with EQ and gain? For that matter, how many DB drag winners are using 10s and 12s? According to your "physics" they should all be using 15s to get more sound pressure.

Anyone else remember the BMW in the late 90s that had 15" subs in kickpanels? Tore up the SQ scene, judges were nearly in tears, the car sounded so good.

A sealed box built properly and with the right woofer will play louder lower than almost all ported boxes due to the lack of output and power handling below it's tuning frequency. A sealed box doesn't have the inherent issues ported boxes have in this respect, not saying it's the be all end all of boxes but can be better at playing below 30hz which is where the fun stuff is

^ I disagree. Most sealed boxes have substantially more cone movement between 25-60hz than a vented box so, unless running a monster excursion driver, it may be easy to overpower the suspension when sealed. Also, sealed boxes almost always have a much higher F3 than a vented box, indicating lighter response in the low end.

Further to this, I routinely see more output from vented boxes in the 25-30hz range when tuning around 30hz than with a sealed option for the same driver. To handcuff a system looking to improve the very limited amount of sub-25hz music out there seems like a bad trade off to me. :dunno: