Right know I hit decent spl# with my current box, which is tuned to 37hz, I called the manufacture and they gave me specs on a new spl box but they told me most people with my equipment tune to 50-55hz! I had a test done, between 42 and 47hz it was the loundest with a 44hz peak. However, I never went past 47hz because it started to lose db's! What should I do? retest! or tune to their recommended 50hz? This box they recommend is much bigger then the box I tested at to begin with.

Thanks
David

pm me man

this site has a formula that works for me
http://www.jlaudio.com/tutorials/ports/index.html

Its not the formula for the port that I'm having problems with. I dont know what to tune the port to 40hz? 45hz? 50hz?

It all depends on the car.. the only way to find out is to test [img]graemlins/thumb.gif[/img]

Alright lets say my car gets the most response at 44hz! What should I tune the port at?
The size box they want me to make is like 7.25cf, made out of inch thick mdf, I cant afford to make 4 or 5 of these boxes even though I know testing is my best bet. I just want to think everthying through so I get as close on the first try.

Thanks
David

[ July 15, 2005, 11:35 AM: Message edited by: dchow ]

tune 7hz below peak. u dont need a 7 cube box for 1 12. 3 cubes is more than enough

^ 7hz? Always? Regardless of what the frequency is?

I'm not knee deep in the SPL world so I'm not disputing you - just seems kind of odd. If you look at it from a box point of view, one would tune 1/2 an octave below the resonant peak, so in this case 33Hz. Admittedly, that seems low for an SPL box but then 44Hz is kind of a low resonance too - must be a large vehicle.

Must be a case of the real world and theory not quite lining up [img]graemlins/dunno.gif[/img]

The "7hz rule" is more just a guideline of where to start. Any SPL box design really needs to be tested at a few freq's to find out which suits best. [img]graemlins/thumb.gif[/img]

this is exactly why this topic is in the SPL section... and Prolifik knows SPL. If he said that throwing subs off a brigde would gain spl, I would prolly believe him and then ask him which brigde as the biggest gain

ahaahaha... and if you have to throw the sub upwards and allow gravity to help it accelerate on its way down or if you should just throw it down words ! [img]smile.gif[/img]

FYI: the larger the box the closer the peak output will be to the port frequency... the smaller the box the further the port frequency from the peak frequency

if your not happy with the freqency your at and you want to go up in hz shorten you port in increments and find your sweat note by testing and alot of it

Yo Peter, i actually have come to disagree with the large box closer to port peak and smaller box farther from port peak. say what if you have a box thats same size but you keep changin the port bigger or smaller........what happens in that case? what if you add or take out ports without changin volume of the box at all?? like the case is with external aero ports like mine?

In SPL there is no such thing as calculation tunning, only testing using a termlab.

X

^^^True Datt Brotha' [img]graemlins/laugh.gif[/img]

in this case... keeping box always the same volume and keeping port say 12" long but adding one more port to the already existing port will cause the tuning frequency to increase, reversly... if you have 2 ports each 12" in length and you plug one of them, the tuning frequency will decrease... in a simmilar fashion box volume the same and # of ports the same, shortening the port length will cause an increase in tuning and reversly lengthening will cause a decrease in tuning... but this is all in your situation where your ports are mounted to the outside of the enclosure and not changing the internal air volume of the enclosure [img]smile.gif[/img]
I know, now you can laugh because you knew I would get into a really nice lengthy explanation [img]smile.gif[/img]

Im still calculating... and still works

Im still calculating... and still works </font>[/QUOTE]So you build a box, you can tell with any sub, in any car within a given box size and port tunning what the car will peak at within .1 db?

With calculations? No.

Termlab? YES!

X

Peter i have no clue what u said there man but i will just take your word for it.

Xiphoid dont be an idiot and say calculations do not work, you are an embarasment to every spl guy who actually does use his head. what did u hit in your super street 1-2 car with 2 15's and 8 amps?? 154something??
Mean while MTA does 157.x with 2 audiobahn 12's and 4 amps in a no wall set up.

Im still calculating... and still works </font>[/QUOTE]So you build a box, you can tell with any sub, in any car within a given box size and port tunning what the car will peak at within .1 db?

With calculations? No.

Termlab? YES!

X </font>[/QUOTE]I wouldnt say 0.1..but close...and yes as long as I have the "Theile Small" I can calculate it

yeah, the calculating part isn't the problem with SPL. you can do really well with calculating. It gives you a Fine starting point for the SPL that a box can put out! :D but the ultimate tool is of course the termlab! ;)


Livin Loud

or a peice of mesonite

masonite is good stuff [img]graemlins/freak.gif[/img] .... wait a second... i heard neon lights gain spl [img]graemlins/dunno.gif[/img]


Livin Loud

you're both krackheads [img]tongue.gif[/img]

The world is ruled by physics, I am sure their is a formula out there that takes into account every possible variable. It's funny that alot of the loud Europeans seem to have engineering and science backgrounds.

alot of the loud europeans have engineering backgrounds?????? ok name 10 people, their class and their spl.

or are u talking about team BS which consisted of 10 guys and 1 vehicle?? lol

Yeah, Team BS was the immediate group of guys that popped into my mind.

Yes but some of those variables and formulas are unattainable so therefor you must rely on a mic to fine tune basic formulas and thinking.

Even then I'm sure somethings don't make sence that are louder.

X

Well I think that all the tricks that are known now, make sense and people thought they didn't not too long ago. Like I said, physics pretty much rules the universe.

for any street vehicles physics cannot take of everything!!! EVERY vehicle has differences. I have seen ppl test out 4, or 5 different CRX's (same model, and year though)with the same EQUIPMENT and same BOXES and get a 3 db difference! [img]graemlins/freak.gif[/img]

how does physics help you now?


Livin Loud

Those are simply variables in the equations, some cars may have brand new weatherstrip, while others are old and cracked. Some may have extra holes in the firewall, while others don't etc. I am sure if you did a 'leakdown' test on the interiors, you would find large variable that while hard to test for, are possible to factor into an equation.

I never said that there was a simple formula, or that using a formula would be quicker and less time consuming than just trial and error testing, just that there is a formula somewhere that would work.

Can you imagine in the future people taking cars into their local SPL specialist for interior leakdown testing? You heard it here first folks :D

That makes sense. the same vehicle, same equipment, same box, etc.
BUT same elevation, same temperature, same time, same mic, same humidity?

There are always variables to every situation. Calculations help, so does testing. It's a sweet science.

That makes sense. the same vehicle, same equipment, same box, etc.
BUT same elevation, same temperature, same time, same mic, same humidity?

There are always variables to every situation. Calculations help, so does testing. It's a sweet science. </font>[/QUOTE]they were ALL in the same shop! they had like 5-6 CRX's man [img]graemlins/freak.gif[/img]

not every car built equal [img]graemlins/dunno.gif[/img]


Livin Loud

LOL. yes very true....

makes sence now...


Hey Perfect Tones offer "leakdown" testing now, for $80.00.00 each! :D

Livin Loud

I'll take two ... [img]graemlins/laugh.gif[/img]

the way that sheetmetal is formed into shape, makes variances in thickness from panel to panel.
both of my colts have different resonant frequencies...spl is "vehicle dependant".
with sound deadening,foam,adjusting door/hatch latches, you can alter the frequency..i just need to see how far i can push it :cool:

termlab is a very useful tool,and with the proper box (.707 qtc)you can find the frequency,modify,your cars frequency and build a ported box(using a calculator gets you close)
than fine tune with the termlab [img]graemlins/deal4u.gif[/img]

[ July 23, 2005, 07:36 PM: Message edited by: Loud Brown Kicker Colt ]

:(

[ July 25, 2005, 02:03 PM: Message edited by: dchow ]

I'm still using a good old rock and a piece of flint!

The modelling you can perform with LEAP will give you highly accurate results, if you know how to define the interior of the vehicle as an acoustical filter. I'm in broken record mode, having stated this in previous posts. It's expensive as hell, has a learning curve that tolerates no guess-work, and totally kicks ass!
You can accurately model response and SPL with regard to how far the windows are open, so modelling the leakage from the random holes in the vehicle is also on the menu. It's great, it's accurate, but as stated in other posts on this thread, you just don't know for sure until you build the damn thing!

If all these computers, programs, analysis, science and experts are so accurate, why can't they build a simple violin, the like of which a semi-literate Italian turned out with regularity, some 200 years ago?

Kevin is that you. I was just in the old school forum and was suprized to C 2001, Gord and my brother mentioned. I had thought of you as well, and to my suprise I found this post from you. Is there any way I can contact you. Maybe you can let RT know that I want to talk to you and to give me your e-mail.

Hope to chat soon
Ryan Sontowski