Port location,Opinions needed

[garychurch84 127]

This is one if the instances is recommend a 4th order bandpass

I wouldn't mind trying it,I know jack squat about box design tho.I'll search a little to see what I  can find.

[garychurch84 127]

I found this calculator during my research looks to be BS.What do you all think? http://www.carstereo.com/help/Articles.cfm?id=27

[Quentin Jarrell 671]

I found this calculator during my research looks to be BS.What do you all think? http://www.carstereo.com/help/Articles.cfm?id=27

that calculator is pretty damn close to doing it by hand.  Remember Winisd doesn't model bandpasses correctly.  It seems to make the gain on the low side.

 

I calculated about 10 by hand using the Loudspeaker cookbook and the car stereo calculator was extremely close on all of them

[garychurch84 127]

I found this calculator during my research looks to be BS.What do you all think? http://www.carstereo.com/help/Articles.cfm?id=27

that calculator is pretty damn close to doing it by hand.  Remember Winisd doesn't model bandpasses correctly.  It seems to make the gain on the low side.

 

I calculated about 10 by hand using the Loudspeaker cookbook and the car stereo calculator was extremely close on all of them

Maybe I don't understand how this works just yet lol,I'll take that back I know I don't.Vr and Vf seemed like a lot of cubes for the icons or is that not what this ?

[Quentin Jarrell 671]

give me a minute I'll up load some pics for you to read

[garychurch84 127]

give me a minute I'll up load some pics for you to read

awesome:)

[garychurch84 127]

I keep reading about ratios like 2:1 for example for every cube sealed use 2 cubes on the ported side.

Last topic I seen about a 4th order guy came in sayin he wanted to do a 4th for a sundown use useing X ratio,poor guy got throwed under the bus lol.

4th order seems to be a touchy subject here lol so I'm treading lightly

Edited January 30, 2014 by garychurch84

[nadcicle 77]

One does not simply talk about 4th orders lightly. I've seen 2:1 perform Ok, and I've seen 30:1 perform Ok. It's really a matter of testing like mad crazy if you've never done it before.

[j-roadtatts 1,129]

Have you tried firing the subs/port in a different direction? Possibly even firing to the side? As sub frequency's are no directional (and very long waves) you never know what will have the most effect on amplitude. Honestly you shouldn't even need the ski pass open, as sound waves travel through anything thinner than the length of the sound wave.

 

 4th order would work, but most likely would be real peaky sounding and not very tonal. I have a 4th order so can say they are a bitch to setup and require a driver that is designed for such an enclosure.

[Quentin Jarrell 671]

If you can read these this will explain everything on that calculator.  It's a pain in the ass to do it by hand so I use the calculator to get a volume that'll work and double check it by hand.

 

 

[garychurch84 127]

Thx Q

[garychurch84 127]

Where can I find a trustworthy WinISD?Download 3 or 4 different ones with no luck.

[Sencheezy 689]

Which way to aim a trunk mounted woofer box in a car has been quite a topic of speculation for years. Folks, through experimenting have found that oftentimes the woofer box sounds much better when aimed backwards, the explanations I hear for why this works are usually quite absurd.
One absurd explanation is "the sound wave travels further when the box aims to the rear and by traveling further it sounds better. "   Not true, sound actually looses volume as it travels, not becoming louder like his explanation seems to imply!
Folks also say "the wave has more room to develop."  Well I don't like this explanation either, sound can really reinforce itself amazingly well in a small enclosed space without the need for any wave developing space!
And there used to be a story floating around called "bass trap" which inferred a magical property of some cars to eat up all the bass and not let it get to your ears.
There still really exists, a problem of building a wonderful well thought out and superbly engineered woofer box which makes bass so perfect my eyes water, with only a few watts of input on my test bench, but then barely has any output when installed into the car, this has driven me nuts for years.
Or, building a great box for 12's and installing it only to have less bass than the one I did the day before in a different car using only 8's.
The big clue came when I noticed there was much more bass with the trunk open than with the trunk closed!
How the hell can that happen???
Opening the trunk lets sound escape(!), letting sound go away cant possible be a good thing.  Then why does opening the trunk make the bass inside the car much louder????
I dragged out the test equipment (audio Oscillators, RTAs, Pink noise generators, and built me a couple of test boxes to experiment with.

 

After a few days of playing with all the fun toys I discovered the bass that goes away when opening the trunk was causing cancellation when kept in the car (trunk closed), and turning the box backward made less of a difference when opening the trunk, and moving the box all the way to the back of the trunk eliminated having an increase in SPL when opening the trunk totally.

In summary I found:

1. box at front of trunk speakers aiming forward or up through the rear deck = poor in car bass response, much better with trunk open.
2. box at front of trunk speakers aiming backward = better in car bass response by far, slightly better with trunk open.
3. box at back of trunk with speakers aiming forward = better in car bass, no difference with trunk open.
4. box at back of trunk with speakers aiming backward = best in car bass response and gets less bass with trunk open.

I used sine waves and mapped out the phase relationships between the incident (direct) sound wave entering the car and the reflected wave that hits the back of the trunk and reflects forward. Since the reflection is bounced into the listening area, you can treat them much the same as having two sources...

I drew some pictures to illustrate what I found.

 

 

 

In this picture, try to imagine the back of the trunk is the vertical black line at the left of the picture and the little square is the speaker box. This picture is an illustration of what happens when sound comes out of the right side (front side) of the little square speaker box. Sound actually goes forward into the car (incident wave (RED)) and also backwards to reflect off of the back of the trunk (reflected wave (YELLOW))... Both the incident wave and reflected wave get to the listener but they are way way out of phase causing mucho cancellation in the listening area. If you could open the trunk, the reflected wave would disappear and NOT reflect back into the car thus no cancellation...

 

 

In this picture, the speaker box has been aimed at the trunk instead of in the car and it is plain to see the incident and reflected wave are not nearly so much out of phase as in picture 1! Resulting in much better bass!

 

 

This picture it represents the speaker box being moved to the rear of the trunk with the speakers aiming forward. The waves are a little closer to being in phase with each other. (were gettin there!)

 

 

Finally, in this picture we are aiming the rear mounted speaker box to the rear so the incident and reflected wave are very close to being in perfect phase, reinforcing each other quite well.

 

These pictures are simulating a 60Hz bass note with the rear of the box mounted approximately 3 feet from the back of the trunk (reflector) ...

Keep in mind we are only discussing the incident and rear reflected sound in an effort to try to simplify this, the reflecting sound waves in a car are much more complex than these drawings indicate but we must start simple before we work ourselves into the more complex, hopefully this will be a nice foundation for those of you who wish to study this phenomenon further.

And for those that have the mindset that this can't be true because the interior of cars are small in relation to bass wavelengths, so what? The full wavelength does not have to completely develop to be OUT OF PHASE or IN PHASE with its own reflected sound. The pictures above are showing a 60Hz wavelength and the bounce distance to reflect back out of phase a complete 180 degrees is just over 4 ft. At higher frequencies the distance is less (120Hz is 2.3ft)

[j-roadtatts 1,129]

Where can I find a trustworthy WinISD?Download 3 or 4 different ones with no luck.

WinISD on Facebook. Download the Win7 version if you have Windows7 as it will work best.

[garychurch84 127]

Where can I find a trustworthy WinISD?Download 3 or 4 different ones with no luck.

WinISD on Facebook. Download the Win7 version if you have Windows7 as it will work best.

Thx man,I got windows 8 but it should still work

[j-roadtatts 1,129]

Here is a tutorial on the sequence to entering the numbers. Also explains what you are looking at if your not sure. There is a link to a youtube vid on there too if you are struggling. 

http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/6330-winisd-pro-tutorial-download-detailed-guide-how-use-winisd-pro.html