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mestapho

ANSWERED port fitting difficulty, help please!

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So I am designing a 38 x 13 x 21.75 box (external including double front baffle) for 2 SA12 dual 4's

net after subs and port is 3.8 cubes tuned to 33.5 (sundown says 35 hz, forums I'm seeing 32 so split the difference) 

4 x 11.5 x 21 center port.  

1200 watts from Pioneer 9601.

Here's the issue,  If I stop the ports to make turns to the sides of the box, half the port width, 2" from the rear wall, the center measurement over 21 inches (22.75") just with the width of the port wall.

Is it fine how it is? Should I change it, if so what/how? 

Any advice is much appreciated.

Port problems 2 sa12s.jpg

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When it's close and I want to extend the port a bit to add a bend, I do something like this...

TCLaFg.jpg

 

It adds length to the portwall needed... I'll just adjust the external measurements a touch to account for the shrinkage in volume. Then once I re-dimension it (volumes & end corrected port length) and put the #'s in Winisd I'm usually close... if I want it perfect at that point I just resize one dimension until I get the volume/tune desired.


JVC KD-X350BTS, Sundown Sa-15 5.7ft3 net ported @ 43hz, Synergy 3K@ 2 ohm, RF 500s, Polk DB comps, Cache Preamp/EQ

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27 minutes ago, shredder2 said:

When it's close and I want to extend the port a bit to add a bend, I do something like this...

TCLaFg.jpg

 

It adds length to the portwall needed... I'll just adjust the external measurements a touch to account for the shrinkage in volume. Then once I re-dimension it (volumes & end corrected port length) and put the #'s in Winisd I'm usually close... if I want it perfect at that point I just resize one dimension until I get the volume/tune desired.

That's a good idea, thanks!

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40 minutes ago, mestapho said:

That's a good idea, thanks!

Yeah... too much of a good idea can make a headache tho... sometimes it's just easier to tune 1-2 hz over what you were after originally or close-up the port area a bit if you got the wiggle room. But I usually get all stoopid and try to hit the volume/tune I was after.

I love Sketchup for rechecking port length and volumes... beats the hell out of a box calculator

TCIP5b.jpg

Sometimes I'll add roundovers to shorten the length as well... I suppose it all depends on how close the volume/tune ends-up.

Edited by shredder2

JVC KD-X350BTS, Sundown Sa-15 5.7ft3 net ported @ 43hz, Synergy 3K@ 2 ohm, RF 500s, Polk DB comps, Cache Preamp/EQ

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Yeah, I'm thinking I'll just keep it straight back, shorten it a 1/4 inch an round it.  I'm pretty sure that'll land me in a happy medium.

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Adding the beveled peak on that back wall will help with airflow, I almost always add it in and if I can I'll roundover the portwall , even if it's 3/8" its easy to extrude the part to hit the length needed... what gave me trouble was Aeros, still do but I'm starting to get the hang of it... finding exact displacements for them is a "B" tho... h*ll... drawing one is hard enough...

RKZAme.jpg

Maybe someday I'll get the hang of it.


JVC KD-X350BTS, Sundown Sa-15 5.7ft3 net ported @ 43hz, Synergy 3K@ 2 ohm, RF 500s, Polk DB comps, Cache Preamp/EQ

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Nice, It is a fun program to play with.  

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15 minutes ago, mestapho said:

Nice, It is a fun program to play with.  

Yeah... I'm getting better at making whatever I draw-up look nice, it's a double edged sword sometimes... as building it might turn into a real project. 

Sh*t like this may look great, sound nice and all but to build it and make it look good may be another thing entirely

l86PMq.jpg

Like I'm ever gonna put that in my Honda... I wanted to, but reality set in... I sure love playing around tho.

Probably just do a pair of Sa-15's on 3K, that ^^^ might end-up getting expensive.

All those years, and I never tried to learn this program... took some unwanted spare time (stroke) to get me started.

Edited by shredder2

JVC KD-X350BTS, Sundown Sa-15 5.7ft3 net ported @ 43hz, Synergy 3K@ 2 ohm, RF 500s, Polk DB comps, Cache Preamp/EQ

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Ha. That box would get down and nasty! Awesome

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Goofin around, I felt that a single baffle would suffice for your power... 

KsxEHr.jpg

I increased the port area a tiny bit, got a lil' more volume and did the port how I was talking about. Take a look and tell me you'll need a 1.5" thick baffle on 1200 watts with that box (No big panels)... IMO that'd be fine for your amp.

Cutting the baffle for the port is not how I usually do it but the height makes it kinda necessary.

Anyways... that's how I solved the port issue... add that piece on the back wall... it shortens the port, lost the extra baffles, the extra volume makes the added port length easy to do (oh... I added 1/2" to depth)... Think this'll be easy to build... lol... It seems unless I start out to keep it simple, they start to become projects.


JVC KD-X350BTS, Sundown Sa-15 5.7ft3 net ported @ 43hz, Synergy 3K@ 2 ohm, RF 500s, Polk DB comps, Cache Preamp/EQ

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See I'm the opposite. I can build whatever I have in my mind... but I cant always draw it in sketchup.

When I built my custom center console for my yukon, I drew it probably 75% close to what it came out to be. But the final product turned out way better.

Same thing for my new sierra, I know how to build the box I want with all the curves, but drawing it to spec isnt going to happen lol...

Now your standard rectangle, or angled, or similar box I can draw and build.

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See I'm the opposite. I can build whatever I have in my mind... but I cant always draw it in sketchup.

When I built my custom center console for my yukon, I drew it probably 75% close to what it came out to be. But the final product turned out way better.

Same thing for my new sierra, I know how to build the box I want with all the curves, but drawing it to spec isnt going to happen lol...

Now your standard rectangle, or angled, or similar box I can draw and build.

Example below

Console https://imgur.com/gallery/aPhaKYJ

Console https://imgur.com/gallery/cE9udMD

 

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5 hours ago, shredder2 said:

Goofin around, I felt that a single baffle would suffice for your power... 

KsxEHr.jpg

I increased the port area a tiny bit, got a lil' more volume and did the port how I was talking about. Take a look and tell me you'll need a 1.5" thick baffle on 1200 watts with that box (No big panels)... IMO that'd be fine for your amp.

Cutting the baffle for the port is not how I usually do it but the height makes it kinda necessary.

Anyways... that's how I solved the port issue... add that piece on the back wall... it shortens the port, lost the extra baffles, the extra volume makes the added port length easy to do (oh... I added 1/2" to depth)... Think this'll be easy to build... lol... It seems unless I start out to keep it simple, they start to become projects.

Nice!  I was thinking the double baffle was overkill as well, but I also like it for flush mounting the subs.   I agree about cutting the port out of the front baffle but it is what it is.   I’ll play with it some more tonight. 

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In the space you are working with, power you got (1000 watts fo 2 sa's) and other concerns... I'd really use a round for efficiency and hitting that volume you really want (close to 4ft3 net).

A SDR-35 riser pipe is 5.9 ID, sold in 2' sections by HD and about $8. 

This ought to really do well, nice and musical with good output...

GwdbxO.jpg

I'd consider doing something like that ^^^ if it was me.

 


JVC KD-X350BTS, Sundown Sa-15 5.7ft3 net ported @ 43hz, Synergy 3K@ 2 ohm, RF 500s, Polk DB comps, Cache Preamp/EQ

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Hmmm. I’ll have to consider that. I think WinISD put the air velocity at well over 30 m/s when I looked at 6” round port though. 

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Yes... it's a bit high, but the efficiency and volume savings might be worth it. It's a compromise like most enclosures, but I' do it... Round-over the entry and exit .75", lengthen the tube that amount and your volume/tune would be close.  

A big 8" would be LONG... even a 7.5" like a Sonotube, but a 6" is more area than a pair of 4", easier to do than 3 4" ports  and most likely enough for a 1000 watt amp playing music. 

Sheeit... for your power I'd look for volume and efficiency and that aero/round ought to serve IMHO.

 


JVC KD-X350BTS, Sundown Sa-15 5.7ft3 net ported @ 43hz, Synergy 3K@ 2 ohm, RF 500s, Polk DB comps, Cache Preamp/EQ

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On 9/11/2018 at 2:39 PM, mestapho said:

Hmmm. I’ll have to consider that. I think WinISD put the air velocity at well over 30 m/s when I looked at 6” round port though. 

I thought with round port air velocity had to be below 40mps not 30 like slot port.. shredder said jeff said that last yr anyway

 


KENWOOD X301 HU, PRECISION POWER Phantom 1000, FU 750 12, 2.1cfad ported, soundqubed 6.5" coax/doors, hp & lp xover on hu, AGM starting batt...

Boomin_tahoe said:
2 ohms rule

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I said that?... I suppose you're gonna quote me and try to prove a point... ok... here goes... I keep it under 115fps if I can... otherwise I specify an aero or some kinda flare. As far as compression losses go... I've really never noticed when the velocity is a bit high, chuffing either... Plus actual power delivered is usually less than most think, especially when playing actual music. 


JVC KD-X350BTS, Sundown Sa-15 5.7ft3 net ported @ 43hz, Synergy 3K@ 2 ohm, RF 500s, Polk DB comps, Cache Preamp/EQ

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Using a round limits the port area available to a fixed value... sometimes sacrifices/compromises are made. Hell, most enclosures are a collection of compromises  


JVC KD-X350BTS, Sundown Sa-15 5.7ft3 net ported @ 43hz, Synergy 3K@ 2 ohm, RF 500s, Polk DB comps, Cache Preamp/EQ

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4 hours ago, shredder2 said:

Using a round limits the port area available to a fixed value... sometimes sacrifices/compromises are made. Hell, most enclosures are a collection of compromises  

This. That's the downside to round ports. But I like throwing a big flare on them if I'm borderline on port area.

I know that's how all my boxes go, one compromise for another. But I also try to go for the max in a given area as well...

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