Help choosing sub

[talnlnky]

Originally Posted by sqcomp

...Am I missing something here?

Are you saying that an o-scope won't detect a clipped signal until it's...already clipped or distorting? Are you saying that by the time the scope shows a clipped signal, you've already got a few points of distortion?

Yep, that's exactly what i'm saying. scopes will have a magnification tool that you can use so you can zoom-in to see a more detailed view of the wave. however, there is an amount of error due to not being able to measure small enough, or to display the info in fine enough detail.

I wasn't talking about what the correct way to set gains/signal processors was... tho, I read your comments.... and understand what you say... but generally would still go with bigger amps, and a more purist approach to avoiding clipped signals. the Overlap approach, seems pretty much like a good approach at compromising between sound quality, and the price of buying more powerful amplifiers.

Think of it this way, you can split a circular pie in exactly three even pieces, but you can't perfectly find out what percent each piece of pie takes up. In math when you divide 1 whole by three, there is only one exact answer and that is 1/3. Often times people will say that it would be .3 or .33 or 33% or even .333 with the bar over the top of it that represents the number will continue on into infinity.

.33 is not the same as 1/3,
33% is not the same as 1/3,
.333 with the bar/line over the top still is not even 1/3

Yes they are very very similar... but there is a margin of error.

The scope is the same way, the signal will ALWAYS start to clip before you can actually detect it using the scope. Now, if you do even a mediocre job it will still be better than what you can do by using the human ear as a test tool. So, it's kind of a semantic point, but that is why people always find the clipping point, and then dial back one or two clicks on the deck, amp, or signal processor.

[talnlnky]

Originally Posted by Duckywitbigfeetz

hey sqcomp i got another question for you ( or anyone else who knows the answer). I have calculated the port length to be 11.65 for my tuning frequency. Now the question is that i would like to put the port in the corner of the box ie. using 2 sides of the box for 2 sides of the port. i know that for ports only using one side of the box there is a correction factor of 1/2 h on the length. Is this the same for a port using 2 sides.

hehe... you're trying to get really specific and fined tuned. I have to admit, it's been awhile since i've been able to build boxes (shopless for amost 2 years now). I believe there is some very minore correction, but realistically, that correction will only change the tuning on a sub box by +/- 1hz.

The way I do it, is to figure where my port will be, so if its on the left side of the box, then goes to the back, then takes a 90degree turn alongside the back wall to the right. I take a straight edge, and draw exactly where my port walls will be. I then find the exact center of the port, and draw another line. When you are done, you should wind up with two L shaped marks on your box. the line that passes through the center of the port is the line I would use to do the measurements... (for you 11.65 inches long). I do remember that boxes that are designed off of wavelengths like transmission lines, every turn you do have to re-adjust for.... but wavelength based boxes often have a half dozen or more turns... which add up to a significant correction factor.

To sum up, I believe you are supposed to do some correction for every turn, but not sure, As for walls.... I don't think it matters for walls.

I would be more concerned with the displacement of the sub & internal bracing than I would be of the correction factor of a single turn.

[Duckywitbigfeetz]

never mind i got it planned it another way i will be making one turn and you are correct the correction factor only makes a .56 hz difference according to bass box. lol ... im making a wood / fiberglass box .. one last question now im looking at port velocity and i cant go any bigger area with port because length is not feasible is a 22 m/s speed ok. i see recomendations online to try and keep it below 18 any ideas.

[sqcomp]

Hey Taln, what about using bigger amps AND level matching? :)

[talnlnky]

Originally Posted by Duckywitbigfeetz

never mind i got it planned it another way i will be making one turn and you are correct the correction factor only makes a .56 hz difference according to bass box. lol ... im making a wood / fiberglass box .. one last question now im looking at port velocity and i cant go any bigger area with port because length is not feasible is a 22 m/s speed ok. i see recomendations online to try and keep it below 18 any ideas.

I know if you use flared ports you can get away with a higher m/s value. For example, with the expensive precision ports you can get away with numbers closer to 30m/s. If you're using wood to make your port, just take a roundover router bit (the bigger the better) to the port openings. then sand it down nicely so it is smooth. It won't be as good as a precision port, but it will be a little better, and should be fine for you to go with that 22m/s port.

Make sure that you put in your actual wattage in that port velocity chart... the velocity will change alot from say 100watts to 400watts.

Originally Posted by sqcomp

Hey Taln, what about using bigger amps AND level matching? :)

isn't that what I said???? oh gosh....