[infinkPoode]

Does it matter if the port of a box is partially out side the box or does it have to be all inside? This is for a slot port.

Thanks....

[ådrrraj]

Outside the box?

The tube should be in entirely.

[infinkPoode]

Do you have any reason for that or just becase they normaly are?
Its only because of space constraints and I am only talking about 3 inches.

I can't see how it would affect the sound as the port is the same size as if it were inside.

[HomePageOEMfreeSOFTWARE]

You can do whatever you want with the port, so long as it's the length you intend it can stick in or out of the box.

Most box calculator programs account for one flanged end (flush with an enclosure wall) but it wont make much difference in the real world if you have no flanged ends.

[Scukonahuy]

box calculator programs account for one flanged end (flush with an enclosure wall) but it wont make much difference in the real world if you have no flanged ends.

Aside from turbulant noise around the port end,but if you have a ported box you probably don't care about SQ much anyway..so I geuss it's not a huge thing.

I would think that it would somewhat alter the sound because it alters the overall volume/pressure of air,not by much,but I would predict a slight difference.

Probably not enough to bother most people as long as it booms.

[HomePageOEMfreeSOFTWARE]

Aside from turbulant noise around the port end,but if you have a ported box you probably don't care about SQ much anyway..so I geuss it's not a huge thing.

I would think that it would somewhat alter the sound because it alters the overall volume/pressure of air,not by much,but I would predict a slight difference.

Probably not enough to bother most people as long as it booms.

Flanged and flared port ends are a different thing, unless you have a huge radius a flared port end makes little difference in practice.
Actually a ported box will have lower distortion as excursion is much lower down to the tuning frequency as the port damps cone movement. The main problem with ported enclosures is they have no loading on the cone under fb so you have to high pass filter it so the cone doesnt flap it's self to death at very low frequencies

[Scukonahuy]

Actually a ported box will have lower distortion as excursion is much lower down to the tuning frequency as the port damps cone movement.

At and right around the frequency that the box is tuned to maybe,although it *will* be boomier/less distinct* even at it's optimum frequency. The thing is frequencies it isn't optimised for will pretty much just sound like indistinct crap....well even more than it already does.

Great if you listen to music that pretty much stays within a very limited frequency range I geuss,otherwise a nice,small sealed box is going to produce a much smoother,more natural sounding bass across a much wider range of frequencies. In practice geuss which I think is better?

I did mix the port ends up though,still..if there's more of the port protruding I'd still say it will be turbulant and lead to some nice port noise.

[HomePageOEMfreeSOFTWARE]

You're not fully upto speed on how ported enclosures work, the sound above and below the tuning frequency isn't cut like a brick wall. I'll do some plots later to illustrate what I mean

It's a common misconception ported enclosures sound bad because they're harder to get right than a sealed box, therefore more people get it wrong hence the reputation. Neither approach is superior, they both have upsides and downsides. You decide which best suits your application and go from there. The biggest mistake people make is not to high pass filter subsonics on a ported enclosure, it might sound wrong to cut the extreme low bass from a speaker that's job is low frequencies but you'll see what I mean when I have time to do a better explanation [thumbup]

For the record...
Sealed
Good cone damping/control at subsonics
Low rate of rolloff, greater subsonic output
Less phase swing
Less group delay
Higher excursion - higher harmonic distortion
Higher rolloff frequency
Less efficient

Ported
More efficient
Lower excursion around tuning frequency - lower distortion
Lower rolloff frequency
Easier on amplifiers
Higher group delay
Higher rate of rolloff
More phase swing
Poor subsonic cone control, high pass filter required

[Habalinnyf]

or to put the aforementioned in laymans terms,
sealed = tighter bass
ported = boomier bass

[melissa]

Hi I have a question also.

I have 2 of these



Pioneer TSW305F's they are free air subs apparently. In my previous car I mounted these 2 on a board and put it in the boot as below...



That isnt my car or pic but thats the setup I had. Worked great because the board sat up flush and there was a hole that it covered behind the back seat. I now have a different car and I havent tried the same setup although I have positioned it in there and it doesnt sit up as nicely.

So basically my question is, for the above subs what should the dimensions (in metric) be for those 2 12" subs. Also should it be ported being that not ported would make a hell of an easier job for me. Would a sealed box be sufficient?

[HomePageOEMfreeSOFTWARE]

or to put the aforementioned in laymans terms,
sealed = tighter bass
ported = boomier bass

Not at all if you know what you're doing

For a car you need to take into consideration cabin gain, which increases relative SPL at about 6db/octave under a certain frequency which is determined by the size of the cabin.
Usually a low Q sealed enclosure will give you the flattest frequency responce in a car, ie a larger sealed box than normal. Are you guys that think ported designs sound boomy going purely by systems you've heard in cars? If you are it's because cabin gain probably hasn't been corrected for, so you'll have been listening to a system thats got way too much output under 150Hz; hence boomy sounding.
To give you an idea how much difference this can make my HT room is quite small (12.5x10.5x8 ft) and the room gain is about +20db's at 10Hz, with the gain starting at 100Hz or so. I designed my sub to mirror this curve, hence flat output into infrasonics

droy I'll try and dig up some specs on those woofers and give you an idea where to start [thumbup]

[infinkPoode]

Thanks guys, I picked a ported box because the quality of the sub sounded much nicer
to me, went lower too.

Here is a quick sketch I did that is roughly in proportion (Side view cross section).



There is only a small bit sticking out at the end.
Using the Theile Small Parameters, the box will be tuned to 27hz using these calculators:

For the Port

For The Box

[HomePageOEMfreeSOFTWARE]

Just FYI, there's no problem putting a vertical piece on the inner side of the port to extent it up the back of the enclosure, it's not a horn so it doesn't have to be super smooth. That way you wont have to have it sticking out the front if you don't want [yes]

Also leave a bit extra on the length of the port, I tend to find in practice I like to tune a little lower than the maths tells me to.

droy - Those drivers have a very high Qts, meaning they are designed for a sealed enclosure. I havn't worked it out but looking at Qts and VAS you would end up with an enormous ported enclosure, too big to fit in the car [shocked]
Either stick them in the biggest sealed box you can deal with or mount them as in the picture, you'll effectivly be using the boot as a big lossy sealed box.

[Konservir]

If you do a search for a program called WinISD beta. You'll find a free program for building subwoofer boxes. It does all the math for you based on the Thiele/Small specs. And calculates proper port diameter and length for tuning.

Something It also shows is Some subs are suited to closed boxes while other subs are more suited for ported boxes. It's has a scale system that leans to one side or the other.

[HomePageOEMfreeSOFTWARE]

WinISD is the main tool I use, if you get WinISD Pro Alpha from the LinearX website it gives you a lot more options than ISD Beta

http://www.linearteam.dk/default.aspx?pageid=winisdpro

[eCw56dzY]

Not at all if you know what you're doing

For a car you need to take into consideration cabin gain, which increases relative SPL at about 6db/octave under a certain frequency which is determined by the size of the cabin.
Usually a low Q sealed enclosure will give you the flattest frequency responce in a car, ie a larger sealed box than normal. Are you guys that think ported designs sound boomy going purely by systems you've heard in cars? If you are it's because cabin gain probably hasn't been corrected for, so you'll have been listening to a system thats got way too much output under 150Hz; hence boomy sounding.

"Cabin gain" due to a vehicle's transfer function is actually closer to 12dB/Oct, not 6 as you stated. While the frequency does vary with interior volume, it begins at 60-80Hz for almost all vehicles.

The reason most people feel sealed is "cleaner" than ported, is due to the group delay of ported systems, which often makes them sound less "tight" compared to sealed.

[Scukonahuy]

You're not fully upto speed on how ported enclosures work, the sound above and below the tuning frequency isn't cut like a brick wall. I'll do some plots later to illustrate what I mean

Actually I know more about it than people tend to give me credit for on here.

Once you're below the ports effective frequency range the sub will "unload".
Like I said it's great if all your music stays above that ports effective tuned frequency,it's more effecient in that narrow range,but once you get past that there's no way around it...your sub starts to unload and that just sounds nasty.

[HomePageOEMfreeSOFTWARE]

Actually I know more about it than people tend to give me credit for on here.

No intentional patronising intent in my posts, hint taken

Cabin/room gain rate varies, depending on where you read it's stated as either 1st or 2nd order. Nearfield and in room measurements of my HT room give somthing like 8/9db/octave [rolleyes]

I'm not trying to annoy anyone, just responding to the baseless claim that sealed = good and ported = crap
If that were the case there wouldn't be so many highly regarded ported speakers.

[infinkPoode]

So you mean like this?


"I'm not trying to annoy anyone, just responding to the baseless claim that sealed = good and ported = crap
If that were the case there wouldn't be so many highly regarded ported speakers."

I tend to agree with you, my logitec z5500`s soud quite good and that sub is ported.[thumbup]

Here is another box that I made a while back:













I was aware that how I did the port and the stand like that would make noise but I wanted to
see how much.
I can only hear it at loud levels, I ended up taking the baseoff and laying it on its side.
(it was for a home setup)

I had a look for WinISD beta, I just have to learn how to use it now!