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Discussion Starter #1 (Edited)
I'm currently building a vented box for the rear sub.
Tuned to 32hz.

I know already, just by looking, that I don't have enough room for a vented box for the front sub. (Between the seats)

So is it a bad idea to run one sub vented, and the other sealed?


Playing with WinISD shows this...

 

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Discussion Starter #2
Max excursion occurs in the vented box around 18hZ.
I used different filters to try to get them to play at the same levels without damaging the vented sub.
Even with full 1000 watts, the sealed doesn't come close to max excursion.
 

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I wouldn't run both as you plan, but that's me.

I've tinkered with the idea of having a sealed and ported setup in my car with a toggle switch to choose between the sealed or ported setup depending on the music I'm listening to and my mood.

With running two subs in different enclosures it may be wise to band pass the sealed to play the upper bass and the ported to play everything below 50Hz or so. and don't forget you need a SSF active no lower than 27Hz to protect the ported driver.
 

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Discussion Starter #4
With running two subs in different enclosures it may be wise to band pass the sealed to play the upper bass and the ported to play everything below 50Hz or so. and don't forget you need a SSF active no lower than 27Hz to protect the ported driver.
I thought it was 6dB lower than the tuned port frequency for the ssf.
 

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I don't see the benefit of running a sub up front and one in the back. But your ears don't care if one is sealed and one is ported. If you have the frequency response dialed in it doesn't matter if one is sealed and one is ported. It just might be a nightmare getting the overall response dialed in. It might be easier than I'm thinking, but to me it's not worth the trouble, with the front stage tuned well upfront bass shouldn't be a problem with a sub behind you.
 

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You might run into a BUNCH of phase issues... but on the other hand, you might correct a bunch of phase issues that would have been inherent with a single ported sub... If youre not overlapping them in frequency response, you should be able to pull it off with some nifty crossover work and some time delay, might just sound amazing if you can make it all come together. An even more interesting idea might be to tune the front sub at twice the rear subs frequency, in doing so, you might be able to get good harmonic summation (ie, 40hz and 80hz wind up in phase and add nicely), similar to the old ABC box, but with the two tuned enclosures actually physically separated. The front enclosure could be quite small and would need a short vent. Just an idea.
 

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Discussion Starter #7
I was playing with the program again, and I think I can build another ported box that is about 2-2.5cuft, so I should be able to get them pretty close to the same response, and protect them from over excursion with a HP filter in the DSP set to 16hZ.
 

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you're going to get a lot of varied responses as people join the conversation from various camps in audio.

there's the old guidelines of "same sub, same type enclosure, same equalization" and the natural bias against a distributed bass approach that makes bass hot spots more apparent, which also tends to galvanize one towards effectiveness...


you see the big fart boxes with a single huge tuned port, because if you load the cabin that way, you will get the most distinct signature, and hopefully the greatest load at the pressure mics...

but your way, and the way of many sound quality enthusiasts, is to reduce and minimize resonances and give an overall smooth presentation that becomes ever more transparent in the way one focuses or localizes on the sound, overall.

I don't feel like it's necessary to differentiate between bass that is coming through a port, versus bass that comes directly off the cone.

so, in the same vein, shouldn't you not care whether you have a ported sub in one place, and a sealed in another?

as long as one is able to equalize the system to an acceptable standard, (and with DSP it's highly likely today, versus just 10 years ago when it was an impossible task) you can put mis-matched gear in and not notice a loss of quality.

this is an opinion, of course.


I hope anyone who disagrees with it provides some basis for discussion, as I would like to know who can tell the difference between ported and sealed in a blind test, haha...
 

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as I would like to know who can tell the difference between ported and sealed in a blind test, haha...
Well if you played a frequency closer to the tuned frequency of the ported or a song that goes that deep then wouldn't the ported be more obvious which is which if you were to directly side by side compare?
 

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Well if you played a frequency closer to the tuned frequency of the ported or a song that goes that deep then wouldn't the ported be more obvious which is which if you were to directly side by side compare?
if you were specifically throwing test tones to find the place where a vented sub is detectable, then yeah.

but on music, using regular, instrument-driven sounds not produced by a tone generator that removes all the harmonics, it would be a different game, right?

we're not trying to disprove the theory that mixing and matching bass enclosures in the car is bad, are we?

wait, yes we are, hahahaha..
 

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Discussion Starter #11
I thought I was just getting lazy....tired of working on this system every spare minute I have...seemingly very little progression...trying to figure out this and that...
I can run the system with one sub for awhile...just to take a break.
I don't even think I will install the new mid bass drivers yet...
One step forward, 3 steps back...

I also bought a oscilloscope to help set up the system...FINALLY!!!!
 

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5Hz is the "safe" rule of thumb setting, though I'm pretty sure the SSF needs to be set no more than 1/2 an octave below the tuning, which with a tuning of 32Hz, half an octave would be 24Hz.

With enough processing, you may be able to get it to work as some have said, but I just don't see it personally. Then again, I've not got much experience with sound processors, or should I say no experience beyond time correction and EQ's built into the HU's I've owned over the years. External DSPs have much more flexibility than any HU I've used, but I still have doubts.

I just don't see the two sub setups (easily) working well together at all. Call me ye of little faith.

With them playing the same frequencies, I'd think it'd result in either cancellation between the two or a big spike in output over those frequencies.

Still, there are many members on here with far more knowledge and experience than I, so...
 

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Discussion Starter #13
Think I'm just gonna stick with another ported box...."KISS" method.
 

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Discussion Starter #14
What do you guys think of the vents I'm adding to the bottom of the sub box?

 

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Nice looking vents!

I see no reason not to run one ported and one sealed. You may need to play a bit with tuning to tune out some cancelations due to phase, but other than that it should be fine.
 

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I'm currently building a vented box for the rear sub.
Tuned to 32hz.

I know already, just by looking, that I don't have enough room for a vented box for the front sub. (Between the seats)

So is it a bad idea to run one sub vented, and the other sealed?


Playing with WinISD shows this...

I would definitely not run two different types of enclosures. I see phase issues in your future if you do.

I would ponder the issue and find a way to get the 2 ported subs in there.
 

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What do you guys think of the vents I'm adding to the bottom of the sub box?

I do not know if you plan to put the grill material in the port of not but if you do it will throw your port tuning off a bit and also cause some port noise.

Lets say that the grill open area is 60%, well that means that you just reduced the port area by 40%.

Just a heads up:)
 

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Discussion Starter #18 (Edited)
I do not know if you plan to put the grill material in the port of not but if you do it will throw your port tuning off a bit and also cause some port noise.

Lets say that the grill open area is 60%, well that means that you just reduced the port area by 40%.

Just a heads up:)
The port will be wide open.
These vent grills are on the sides of the box...at the bottom. With the down firing sub, the box was sealed up against the floor...the vents are on the sides, and front of the box.

Here is a picture of the box upside down.
You can see where I drew the location of the vented on the front portion of the box.



I have the front ports cut in now, and the trim piece cut. I just have to drill all the holes for the cap screw bolts, and router the inside, and outside edges.

Then take the box all apart, and glue it all together.
 

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Discussion Starter #19
Here is what the side of the box looked like sitting in the cab...
To me, it looked like waaaay too much box...needed something to break it up a bit.

 
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