Porting

[solitaire]

Hiya,

Really basic question here i hope.

If a recomended port size for a sub is say 20mmX20mmX100mm could i install two ports on either side of the sub at 10mmX10mmX100mm each?

Reason being is a shortage of space - i think i can get the full size box recomended and associated port size but not if it has to be one big port...

Make Sense? I thought not!

[Alex B]

This a tuned box i take it?

[solitaire]

This a tuned box i take it?

I think so (im just learning about this stuff). "The Plan" is a box just under the recomended maximum size that the manufacturer specifies with a port...

The box is not square though, its slightly off square due to the space it needs to fit in...

[DeeCee]

porting a box tunes the box to a particular frequency for extended bass response.

Depends on the subwoofer, but ideally you would use the thiele/small parameters in a programme like WinISD or Bassbox and model a box to have peak extension at a desired frequency eg 35hz.

Its not just a matter of chucking in some plastic tubes into a standard box and expecting perfect response.

I would hazard a guess that it could turn to custard fast and sound like Revhead singing in the shower..

Generally ported boxes are larger than their sealed counterparts and there are numerous types of ported enclosures to play with eg, standard bass reflex, 4th order bandpass, 6th order serial or parallel tuned, isobaric configurations etc etc.

Q's:
what sub? what amp?
what music do you listen to?
are you handy with a jigsaw, wood, glue, screws, a drill?

[solitaire]

...

Yeah... so i understood about 15% of that

Probably will turn to custard - but im sure to have fun making it

If its not just a matter of sticking in the recomended port size then i probably wont bother and just go with a sealed box.

I dont think i need to get crazy with the audio programs as i was going with the manufacturers recomendations on box internal volume and port length... i figured that was a fairly safe bet.

The Sub is a Kicker L5 8-4

Very handy with wood

almost edited out the wood comment but thought id leave it in for a laugh!


EDIT: Sorry did not answer all your questions!

Sub is a kicker 8inch
amp will be something cabable of delivering 200w@4ohms

[DeeCee]

if you have the manufacturers recommended ported enclosure size, port size and length, see how that goes for you

otherwise, feel free to ask more questions

[solitaire]

if you have the manufacturers recommended ported enclosure size, port size and length, see how that goes for you

otherwise, feel free to ask more questions

Cool cheers man apreciate your input SO do you think i can split up the recomended port size (maintaining the specified length, with half the specified volume per port) or does that throw everything out a bit?

I whipped up a quick drawing of what im planning, it a slightly modified version of some plans that Ae92typeX sent me, im trying to allow for storing the targas when the roof is off...

Its a bit rough and the measurements are supposed to be in centimeters not meters but you get the idea..

the yellow bit is roughly the size of the speaker, the volume taken up by the speaker is accounted for in my calculations...

The size isnt quite right yet but its close... Do you think such a funny shape will throw it off? Its for an mr2 thats why its so odd



Edit: just thinking, would a u bend shaped port work? Sorry im sure these are really basic questions

[Alex B]

Hold up, thats going behind your seat? You realise the passanger is going to have zero leg room. Mine comes out possibly 5cm from the lip and my legs hit the dash and im only avrage height. Plus you have to allow another 4-5cm min for the subs excersion.

[DeeCee]

- bent port would work fine.
- total port volume split in half would not work
- MR2s are fun to build in.. not, but really, not that bad.
- maybe look at a slot port where the port volume = circular port volume.. swapping cylinder for cubic..
- maybe mount the port over the top of the sub instead of too the sides..
- port does not have to be on the same face as the sub.
- pointing the port towards a hard surface or into a corner gains volume.. just make sure that the resultant air velocity has a place to go ie don't put the port in the lower pocket area where the air has no place to go..

there aren't that many subs that have one way xmax of 50mm... you can get away with half of that.. just account for the top of the surround.

[Lloyd]

And are your measurements in cm? Pretty sure they aren't supposed to be in metres...

And as above, you really don't want to take up much room behind those seats. The passengers seat isn't that spacious in Alexs car and as he said, the sub sticks out bugger all in that.

I personally don't know why you're bothering to try and go ported in an MR2, there simply isn't the room to make it sound any good. You'll get a better/louder/cleaner sound from a sealed enclosure.

[Alex B]

Yes but if tis to close to the back of the seat the built in map holder tends to vibrate quite nicley.

[solitaire]

god I love this forum... such a wealth of knowledge... thanks for your replies gents

yeah its supposed to be cm's... cant get the stupid free CAD program to play ball

this started off as a sealed enclosure. but the design had a fairly large internal volume, sufficient for a port.

I had been told that you get better quality (i don't care about volume) if you have a port... so I thought since I have the room to move why not see if it can be done...

this was a hybrid of a couple of plans with my own thoughts thrown in. not at the mock up phase yet... just initial design.
Thanks for the tip about the seat, have shortened by 5 cm leaving 5cm overhang. This leaves the enclosure at 26litres which still leaves enough for a port with a litre to spare according to kicker's design specs...

thoughts? ports not nessasary or an advantage?

thanks again for you input it is vvery mcuh apreciated

[solitaire]

oh just re-read (on a really small screen on a pda). add another 5cm for the sub sticking out... will redo It tomorrow night but a rough estimate puts it at 21litres which is too small for a port so this might all be moot!

[Alex B]

Pretty sure the general idea of ported is louder, where as sealed is a tighter sound but wont go as loud. Thats a massive generalization. Have a good measure up behind the seat before you make it. Idea might be to make a mock up box out of cardboard.

[scotty_ish]

I had been told that you get better quality (i don't care about volume) if you have a port... so I thought since I have the room to move why not see if it can be done...

Who told you that? Ported enclosures are better for getting loud, sealed is generally better for Sound Quality. Sealed gives you nice tight bass whereas a ported enclosure will give you something that goes loud and low.
Sealed is definately the way I would go, and in an MR2 you wont need the extra volume, but extra space is always a plus!

[solitaire]

oh, yeah well tight bass is what I'm after... loudness is of no interest... thanks guys - we got that sorted quick didn't we!

will definitely mock up first!

[DeeCee]

ported is extended bass response ie it doesn't roll off as soon as a sealed enclosure. It can have a peaky response if designed to, but is not necessarily the case and can easily be configured differently.

And it is a very generalised statement that sealed is tighter and more sq orientated over ported. Numerous subs now have the ability to play tight and go loud in ported boxes. Its how you design the box that is the end product.

One can still get a flat and extended frequency response curve with a ported design and not be peaky

[solitaire]

...

I tend to listen to generalised statements - there is generally a bit of turth in them , so if im interested in punchy tight base over volume and kick recomended a box between 10litres and 20 litres would i be better off going close to 10 litres or 20 do you think?

[DeeCee]

I tend to base it my experience judging sq cars for the last 3 years, installing for 9 years and playing spl (doofdoof) games for 3 years.
I'm starting a shop on my knowledge lol

I am playing wth your sub in bassbox and the curve isn't exactly fantastic with a flat alignment. Starts dropping after 65hz in a sealed and perfectly flat box..

34L = flat (apparently)
20L = slight loss in volume after 50hz
10L = loss in volume after 50hz and the peak at 75hz (yes, it peaks in a sealed box)

by the graphs, ported with this sub is all over the place. Only way to smooth the response is to have a ported box with 57L tuned to 45hz

shoot for the 20L if you can manage it in the space

[solitaire]

I tend to base it my experience judging sq cars for the last 3 years, installing for 9 years and playing spl (doofdoof) games for 3 years.
I'm starting a shop on my knowledge lol

I am playing wth your sub in bassbox and the curve isn't exactly fantastic with a flat alignment. Starts dropping after 65hz in a sealed and perfectly flat box..

34L = flat (apparently)
20L = slight loss in volume after 50hz
10L = loss in volume after 50hz and the peak at 75hz (yes, it peaks in a sealed box)

by the graphs, ported with this sub is all over the place. Only way to smooth the response is to have a ported box with 57L tuned to 45hz

shoot for the 20L if you can manage it in the space

20litre sealed?

Awesome thanks so much for doing that - Really apreciate you putting in the time 20 Litre sealed i can manage

Your starting an audio shop?