dd1508 question from germany

[95stroked1500]

yes, shorter.

but a 2" port doesn't have very good port area for an 8", especially with any decent amount of power to it.

3" is as small as i would go, but you still might run into port compression and velocity issues. 4" is much better.

can you find a creative way to use the port external from the box?

how about re-designing the box... into a center console type? or a combination of center console and still tap the air space from behind the seats? if you are willing to consider another box, post up some pics of the inside of the vehicle.

[drhappy90]

no port must be in box, there is no way to use the port external
i don't want to re-design the box

when i use a 4" port, how long should it be?

what means center console type ?

thanks

[SPL15]

What kind of music do you listen to? Depending on your music tastes, tuning to 45hz could be really bad for the sub unless you use a subsonic filter correctly. If you're already having issues with the sub clanging & banging in a sealed box from too much excursion, you'll be destroying the sub very quickly if you push it hard with music that has bass below 45 hz.

Also, I wouldnt be too optimistic about the performance increase of adding a port. It'll be around 3 to 6 db louder around the tuning frequency depending on box size & tuning frequency. It takes around 10db for music to sound twice as loud to your ears. You really need to load those 1508's against a sidewall or a hard surface to get maximum performance out of them. Bass in the 35hz & up range depends mostly on "exciting" the air which requires a sub to get a grip on the air to move it (high acoustic impedance), hard to do with an 8" cone unless you "load" it against a wall. Bass in the 30hz and lower range depends on moving lots of air which an 8" sub simply can't do effectively.

In a convertible like that. You'll never have hard hitting deep bass. It will be a trade off. You can have decent impact in the 45 hz and up range with almost no output below 45 hz. or you can have deeper bass & flatter frequency response but the output will be pathetic. Even if you could fit a 9510 into that same location in a proper box & port, the results would be mediocre due to the fact you're playing your sub in free space with no cabin loading.

Try to find a way to mount the sub lower & against a wall or surface or even the back of your seat, you'll get a better acoustic impedance match between the air & subwoofer which means better efficiency.

[drhappy90]

i hear almost hip hop
do you mean i should use the 1508 in free air?
i know that the bass can´t go really deep

thank´s

[drhappy90]

hi,
i found some flexible airport 2,95 zoll(75mm) and 40 cm long


is somebody able to calculate what frequenz i will have?

box has 18 liter without subwoofer

thanks

[quickshot]

If you mount the port outside the box the tuning frequency would be around 42Hz.
If the port is inside the box, then it would be around 45Hz

[drhappy90]

ok,
thank you, i will mount it in the box.

this week i build a testbox

[SPL15]

Quote: Originally Posted by drhappy90 i hear almost hip hop do you mean i should use the 1508 in free air? i know that the bass can´t go really deep thank´s

NO! DEFINITELY dont go free air!!!

If you put the port in the box, try loading it against a surface like I said earlier. This will make the port appear to be longer than it physically is which will lower the tuning frequency. also having the part of the port that is inside the box near a sidewall of the box or better yet a corner inside the box also lengthens the effective port length, again lowering your actual tuning frequency. Most Box modeling software & simple math calculations on DD's website dont account for the effect of having the port loaded against walls inside or outside the box. In that car I would try to strive for around 38 to 42 hz actual tuning frequency (tuning frequency in real world, not modeled on a computer). Your port diameter isn't large enough to handle the air velocity of lower tuning & the output either way would suffer big time for minimal bass extension if you tune lower. & make sure you have a subsonic filter TUNED CORRECTLY or you'll break yo sub

[drhappy90]

dumb question, what means against a wall?!

edit: found the answer

but i can´t mount it against a wall

other question, in witch direction the port should show?!
roof?
or backwindow?
subwoofer shows in ride direction

some words in english are really heavy

[drhappy90]

nobody an answer in witch direction the port should show?

testbox is build, must only wait for the flexible port.
how i can check the "real" frequenze of the testbox?! (whether the frequenze is 40 or 45 hz?! )
thanks

[M3 DDurango]

u need a db meter Termlab preferably, a test tones cd and test test test your loudest tone is your Frequency

[JaniU]

In general and in theory the best is to face both the same way, port and sub. But in practice there are many ways to do it and facing up or even side can work well. Facing them opposite directions is something you should probably never do though! (like facing woofer front and port back)

[drhappy90]

hi,
i have good news!
today i finished the testbox!
and the result is perfect

you all made my day!!

in the next weeks i will rebuild my gfk enclosure the same way!

thank you all sooooooo much!!!!

now i hear my music lou

here is a picture of my testbox

[xciso]

What have u do with the port?

[drhappy90]

hi,
actually i would buy the tube few posting up, but it´s not shippable..
so i build it my own way.
the endversion will look better