Setting up a sealed and ported sub together, or multiple (different) ported subs - AVS Forum
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post #1 of 19 Old 06-02-2014, 06:34 AM - Thread Starter
 
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Since a ported sub is 180 degrees phase shifted at tuning frequency, when paired with a sealed sub or another ported sub with a different tuning frequency, there will be cancellations. How can one set a frequency dependant phase delay or something like that to prevent cancellations. In my situation, I would like to combine a sealed subwoofer, a 19 Hz ported subwoofer and a ~28 hz tuned ported subwoofer. I have a minidsp and the source is a PC. Are there any articles or anything on this topic, I can't find anything.

Off the top of my head the only thing I could think of is to set a high pass filter above the tuning frequency of the ported sub to prevent output below tuning frequency, which is out of phase, but this is sort of counter-productive as it will severely lower the output between 15-30 hz, which is where I want to improve.
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post #2 of 19 Old 06-02-2014, 09:09 AM
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The issues you mention are why mixing different sub formats is seldom a good idea. If you want to improve response to 15Hz use identical subs that go to 15Hz and sell off what you have that won't go that low.
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post #3 of 19 Old 06-02-2014, 09:40 AM
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I agree with Bill and since you have a sealed uxl already, I would build more of those. That is a fantastic driver as you already know and the other subs are probably inferior to the uxl.

Also, I have tried integrating a Cap s2 with a pb2000 and could not get it to where I liked it.
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post #4 of 19 Old 06-02-2014, 10:21 AM - Thread Starter
 
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Originally Posted by Pain Infliction View Post

I agree with Bill and since you have a sealed uxl already, I would build more of those. That is a fantastic driver as you already know and the other subs are probably inferior to the uxl.

Also, I have tried integrating a Cap s2 with a pb2000 and could not get it to where I liked it.

Well my other sub is a TC Sounds LMS-R 15" in a 6 cu. ft box so it's quite decent, was hoping to integrate them. I can just seal the box off if I have to I guess.
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post #5 of 19 Old 06-02-2014, 11:11 AM
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I would just get another box. Without modeling that sub, I would guess that a 6ft^3 box is too big for a sealed application.

I probably would still take the uxl over the lms-r 15. The uxl actually models close to the ultra for half the price. Either way, they are excellent subs and great choices.


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post #6 of 19 Old 06-02-2014, 11:19 AM
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Originally Posted by JWagstaff View Post

Well my other sub is a TC Sounds LMS-R 15" in a 6 cu. ft box so it's quite decent, was hoping to integrate them. I can just seal the box off if I have to I guess.

Just use both in sealed boxes, otherwise it can be a waste of time if things don't integrate well.

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post #7 of 19 Old 06-02-2014, 11:34 AM - Thread Starter
 
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Originally Posted by Pain Infliction View Post

I would just get another box. Without modeling that sub, I would guess that a 6ft^3 box is too big for a sealed application.

I probably would still take the uxl over the lms-r 15. The uxl actually models close to the ultra for half the price. Either way, they are excellent subs and great choices.

I already have all the subs built and finished, it's just I have one in the living room and one in the bedroom, but I want to move them together at some point. Yes I do like the UXL a bit more than the LMS, same xmax but the UXL is 18". When I do get more subs, I will definitely be getting more sealed UXL's, but for the time being I just have these two.
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post #8 of 19 Old 06-02-2014, 12:07 PM
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Originally Posted by jpmst3 View Post

Just use both in sealed boxes, otherwise it can be a waste of time if things don't integrate well.

+1. i bought the pb2000 and had it 3 days before I gave up and sent it back.

You already have the subs so you can just play around with them one weekend and find out what you can do. Only thing it will cost you is your time, but you will have a learning experience out of it. if you are having phasing issues, try to high pass like you said, but then you are going to be missing so spl at that fq and below. You never know.....some people don't have any issues mixing sealed and ported.


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post #9 of 19 Old 06-02-2014, 12:28 PM
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I tried this once upon a time with my PB13-Ultra in ported mode and my DIY AV15H dual opposed boxes. It drove me nuts, and I eventually just put my PB13 in sealed mode to "fill in some holes" on the frequency response sort of speak as trying to integrate it in ported mode was like trying to put your finger on mercury. I ultimately sold my PB13 (mind you, that was more because of the fact that I won an SB13-Ultra and didn't really need the PB13, but using it in sealed mode was basically neutering it anyhow).

 

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post #10 of 19 Old 06-03-2014, 01:16 PM
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i was monkeying around with this just yesterday.

it seems that by putting a steep high pass filter on the *sealed sub* down at something like 5-10hz or so, the phase can be brought into alignment with a high-pass ported cab.

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post #11 of 19 Old 06-03-2014, 01:21 PM - Thread Starter
 
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Originally Posted by LTD02 View Post

i was monkeying around with this just yesterday.

it seems that by putting a steep high pass filter on the *sealed sub* down at something like 5-10hz or so, the phase can be brought into alignment with a high-pass ported cab.

a filter at 5 hz will affect the phase at 15-20 hz? Did you do this in winISD or what program?
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post #12 of 19 Old 06-03-2014, 01:28 PM
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here is an example:

b&c 18sw115 driver in sealed and ported cabs. sealed cab gets linkwitz transform for -3db at 30hz, q=0.7, which would be a common sealed enclosure target.

same driver in ported cab, tuned to ~20hz with eq to match the response above 20hz. no high pass.

frequency response, sealed in red of course.


and the phase.


now, applying the protective high pass filter and the eq bump at the crossover, gives this common ported response:


and throws the phase completely out of whack.


by putting an 8th order filter on the sealed enclosure at 10hz with a tight eq bump at the filter center, not much is lost from 20hz down to 10hz.


and the phase of the two systems is brought into almost perfect alignment.
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post #13 of 19 Old 06-03-2014, 01:35 PM
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of course, the same can be accomplished (perhaps more elegantly) with an all pass filter, but i don't know what the parameters mean or how many dsp's include all pass filter options.

n=2 t=0.015 q=1.0


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post #14 of 19 Old 06-03-2014, 01:39 PM - Thread Starter
 
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cool thanks - I think it would be just as good to do it at like 5 hz rather than 10 hz as the whole point of sealed subs is to get the single digits so you don't want to lose too much if you don't have to - because the ported sub will have no output at all below 10 hz so it won't matter what the phase does on the sealed. It's just important to synch the phases at >15 hz.

The all pass filter looks good, it doesn't change the FR at all right? I think minidsp can do that.
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post #15 of 19 Old 06-03-2014, 01:46 PM
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"The all pass filter looks good, it doesn't change the FR at all right?"

right. just 180 degrees phase shift per "n". "t" effectively sets the frequency, though I'm not exactly sure how. i just adjusted it manually until i got a good match.

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post #16 of 19 Old 06-04-2014, 06:13 AM - Thread Starter
 
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awesome - this should be quite easy to set up then. I'm surprised I couldn't find ANYTHING on the internet about using an all pass filter to set up sealed and ported subs together. I would think using a sealed and a ported would be more popular if you can set them up in phase like this - as having two subs will fix most nulls, a sealed will give you great low extension, and the ported will give you great SPL for 20 hz +
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post #17 of 19 Old 06-04-2014, 10:48 AM
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Very interested in this, please give details as you go along!
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post #18 of 19 Old 06-04-2014, 06:46 PM
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Also interested in this thread. Lots of results when searching this topic but there's not what I'd call a definitive thread on it. My setup is four sealed subs and I'm considering adding a Marty-type sub... have an antimode, sms-1, mic2200 for EQ with an xt32 receiver. I also have an omnimic to measure with.
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post #19 of 19 Old 07-07-2014, 08:18 AM
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Can you do this with an Inuke or a berhinger DPS feedback destroyer ?

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