nismo

There are many misconceptions when it comes to audio 'truths'...there is so much misinformation, that I doubt anyone will ever be able to set the record straight for the masses, but here goes:

No, I don't have a degree in audio engineering, or a doctorate in any form of audio, but I have many friends who are audiophiles, presidents of audio companies, etc. I also have numerous friends who have degrees in audio of one sort or another, and I have spent the better part of 8 years learning this stuff.

Myth 1: Sealed boxes are better than ported boxes for sound quality...

Truth: A well designed and built ported box CAN sound as good or better than a sealed box...there are a lot of factors that affect this. The reason that ported boxes are usually regarded as inferior is due to the fact that most people undersize their ports (which causes 'chuffing' noises), and tune their boxes too high.

Myth 2: A larger box will sound sloppier than a small box.

Truth: The whole purpose of going with a Sound Quality setup, is to end up with the flattest frequency response (taking everything into account). The larger the box--to a certain degree--the flatter the response, and better Sound Quality.

In the following link, there is a picture of the response curve for several boxes for a single JL Audio 12w3. The idea is the to have the curve drop off as little as possible going from right to left, but there will always be some drop-off, and cabin gain will help the extreme low end response some. In yellow, the response curve shows a sealed box with the optimum balance between sound quality, and output...notice that there are no peaks (peaks are okay--to a point, but once past that point they become audible, and sound bad). In orange, is the average users sealed box for the 12w3. You'll notice that it peaks and then drops off quickly, hurting the low end. In blue, is the optimum ported enclosure--its flat as far as it can be, and has much more low output than any of the other curves. In green, is the typical ported box. It is loud, but has very little low end, and will sound pretty sloppy.

http://www.bsu.edu/web/ervincent/comparison2.jpg

Myth 3: 15's are sloppier than 12's.

Truth: People assume this, because they try to put 15's in WAAAY too small of a box--even compared to 12's. The picture in the link above shows that the lower the box qtc, the flatter the response, and the lower it will hit. The problem is that people try to undersize boxes for the 15's REALLY badly, and it causes a huge peak, and a loss in low end.

Myth 4: Larger speakers have poorer transient response than smaller ones (people say this meaning that larger speakers are sloppier).

Truth: Transient response's definition is basically how low something will hit...so this is semi-true, but people blame the size on it, when the whole reason is that the box is just too small. it is totally box dependent--nothing else.

I am sure I will have more to add later, but that is all I can think of right now.

Eric
btw, is there any way to make this stick at the top, or make it into an FAQ for everybody's use?

audi-o-man

You have to consider what is true on paper, and what is true in real life ...

audi-o-man

The truth is that small, sealed boxes are better for SQ, and bigger or ported boxes are not,...that is why everyone uses small, sealed boxes for SQ, because it works, it DOES sound better... in the car... when a box is ported, it is tuned to 1 specific frequency...it is NOT a flat response...also, when they test the woofers in the boxes and present a graph, they test them on a bench, not in the car, not with a mobile 12 volt battery supply, etc. What can appear to be ideal on paper does not always work in the real world...

bigbassman

you should get out and view a few larger sized SQ shows, whether it be IASCA, or USACi.. you'll see a majority of WINNING vehicles use IB (infinite baffle) or aperiodic enclosures... The list of woofers that perform CORRECTLY in small sealed boxes is rather short...

Loyd L.

nismo

<center><img src="http://www.bsu.edu/web/ervincent/comparison3.jpg"></center><p>do you understand box qtc? it doesnt change between home and car. physics do not change between home and car...things may react a little differently, but they dont write books called "physics within cars, and how they are different from your living room"

i have to disagree with saying that tuning to a certain frequency means that its not a flat response. YES they measure anechoically. but if youre going for something with a huge peak in it, then its not gonna be flat, in car or otherwise. in this pic, i can show you a truly near-flat response in room/in car/whatever...

in the pic, it looks to me like the ported one goes WAY lower flat than the sealed one, and that sealed one is the optimum box, not some high qtc box like youd put yours in, which means yours would have an even weaker low end! if there is a small peak or dip, that can be eq'd, but there is NO way to eq that sealed box to a response that has an f3 of 20 hz...cuz thats a full octave below where the f3 is in the sealed box!

eric

HIS4

Transient response is something that should not be associated with subwoofers. Transient response describes how the speaker reacts to fast changes in the audio signal. This is something that should be associated with midbass drivers rather than subwoofers. The reason is because transients don't occur in the frequencies below ~65 - 70 HZ. Above that is where they will be most audible and this is the midbass range. I know a lot of people will say that their subs are crossed over at either 80 or 100 Hz but to get a solid front image, it needs to be lower than that. However you need to have some hefty midbadd drviers in the front of your vehicle to cross your subs over that low so most people will not go that route.

HIS4

No one car will have the same transfer function which means that the same speaker will never sound the same in two different cars. The box can be tuned to take into account the tranfer function of the car and produce a flat "in-car" response. If measured in a chamber, the box measurements will look like crap because there is very little contribution in response from the chamber.

Another liitle point is, have you ever heard what flat response sounds like. It's not very pleasing and sounds dead. It's for the sake of measurement only. That why most competition cars have separate EQ settings for SPL, RTA, SQ and maybe everyday listening if used as a daily vehicle. The approach to tuning is so much different depending on what you're trying to achieve. Try and listen to a car with flat response, you probably will think there's no bass and no highs, all midrange.

nismo

yes that is true, but its better to start with a fairly flat response, and tweak to your hearts content, than to start out with a poor response, and try to eq it to where you want it.

also, you forgot that placement/loading affects response too.

eric

HIS4

Some people feel that less or no eq is better than too much. In other words, they would rather get it how they want it with minimal eq interaction. The theory is that you have less components in the loop and therefore, less THD.