Need help - mixing sealed and ported subs? - AVS Forum
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post #1 of 25 Old 11-01-2013, 12:26 PM - Thread Starter
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I thought I knew the answer to this question but recently I read somewhere that mixing a sealed sub with a ported sub in a listening area may not be such a mortal sin after all. 

 

My situation is pretty simple. After conducting the sub crawl I found three good sub placement locations. I'm getting ready to order new subs very soon and had planned on going with dual PSA XV15s. The XV15 will fit fine in one of the locations but it will be a challenge to fit the XV15 in either of the other two locations, it can be done but it will extend well out into an area we walk through. On the other hand a XS15 would fit much better in either of those locations due to the smaller size. 

 

Both PSA and SVS suggested ported subs due to the size of my room so I had originally planned to get two XV15s but now I'm wondering if mixing a XV15 and a XS15 would be okay? Or would that be a bad idea? Also could you please explain why, I'm interested in learning as much as possible.

 

Any help with this is greatly appreciated.

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post #2 of 25 Old 11-01-2013, 12:43 PM
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Obviously it would be better to have matching subs, but I think you'll be OK. As long as all your subs can play at roughly the same level at roughly the same frequency range, you should be able to integrate them OK. Mixing ported and sealed, in of itself, shouldn't present any problems.
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post #3 of 25 Old 11-01-2013, 06:30 PM
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My main concern would be phase cancellation, if they can't be configured to have the same phase curve.
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post #4 of 25 Old 11-01-2013, 07:10 PM
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Originally Posted by rcohen View Post

My main concern would be phase cancellation, if they can't be configured to have the same phase curve.
That's a major concern if you try to mutually couple them. But placed in different locations in the room their differing phase responses are dwarfed by the effects on the room on phase, so it's not a big deal. Mixed subs aren't as good as matched, but far more often than not they still work better than one sub. Still, there's no guarantee of that. I'd buy matched.

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post #5 of 25 Old 11-02-2013, 09:40 AM - Thread Starter
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Okay. Thanks for the input guys I appreciate it.

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post #6 of 25 Old 11-02-2013, 08:22 PM
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We mixed a pair of JTR caps today with a port tune of 20hz and a HPF engaged and four sealed 18" SI drivers and there was 0 issues in integrating. No phase issues, no dips around port tune, no loss of ability below the cap's port tune for the SI. This may be specific to room - but we were surprised in our little g2g - that there were no ill effects of matching the subs. They were all co-located. I'm going to throw up a compro thread tonight or tomorrow on the matter.

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post #7 of 25 Old 11-03-2013, 05:41 AM
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I've definitely had plainly audible cancellation problems before.

I think the bottom line is that it works in some cases and causes problems in others, which is why matching subs is generally recommended.

If there are problems, you might be able to address them by changing the subs' filter settings, because they change the phase curve.
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post #8 of 25 Old 11-04-2013, 08:32 AM
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Bosso's reply is interesting because it differs from the consensus but he also knows more then most.

Would be great to be able to mix ported and sealed but don't know if it's a wise idea for the less technically inclined like myself.
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post #9 of 25 Old 11-04-2013, 09:17 AM - Thread Starter
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Quote:
Originally Posted by goonstopher View Post

Bosso's reply is interesting because it differs from the consensus but he also knows more then most.

Would be great to be able to mix ported and sealed but don't know if it's a wise idea for the less technically inclined like myself.

I'm arriving at that same conclusion as well. 

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post #10 of 25 Old 11-04-2013, 11:15 AM
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The transfer function for sealed and ported subs tends to be quite different, especially near and below the port frequency (natch). The phase issue can be resolved if your AVR will independently set the delay for the two subs. Or if they are the same distance from the LP. Or you have phase/delay control (continuous, not a polarity switch) on the sub (a.la. Rythmik and some of the higher-end Velodyne etc. subs -- I am not familiar enough with PSA or SVS to know what they offer). Or you can play with placement enough to smooth the response by physically moving the subs around. Note 1 foot (about 1/3 m) is about 1 ms in time.

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post #11 of 25 Old 11-04-2013, 12:07 PM
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Originally Posted by DonH50 View Post

The transfer function for sealed and ported subs tends to be quite different, especially near and below the port frequency (natch). The phase issue can be resolved if your AVR will independently set the delay for the two subs. Or if they are the same distance from the LP. Or you have phase/delay control (continuous, not a polarity switch) on the sub (a.la. Rythmik and some of the higher-end Velodyne etc. subs -- I am not familiar enough with PSA or SVS to know what they offer). Or you can play with placement enough to smooth the response by physically moving the subs around. Note 1 foot (about 1/3 m) is about 1 ms in time.

I know it's a waste of low end but can't you just set a universal HPF right around the tuning frequency of the ported?

Would that help minimize phase issues below tuning?
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post #12 of 25 Old 11-04-2013, 12:27 PM
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Quote:
Originally Posted by DonH50 View Post

The transfer function for sealed and ported subs tends to be quite different, especially near and below the port frequency (natch). The phase issue can be resolved if your AVR will independently set the delay for the two subs. Or if they are the same distance from the LP. Or you have phase/delay control (continuous, not a polarity switch) on the sub (a.la. Rythmik and some of the higher-end Velodyne etc. subs -- I am not familiar enough with PSA or SVS to know what they offer). Or you can play with placement enough to smooth the response by physically moving the subs around. Note 1 foot (about 1/3 m) is about 1 ms in time.

I agree with everything except phase and delay are not the same thing. There's no such thing as a phase/delay knob. It either adjusts phase or it adjusts delay. Phase adjustment should only be used for integrating subs with mains, not for integrating 2 subs.
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post #13 of 25 Old 11-04-2013, 01:18 PM
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Originally Posted by goonstopher View Post

I know it's a waste of low end but can't you just set a universal HPF right around the tuning frequency of the ported?
Would that help minimize phase issues below tuning?
Phase issues are the least of your concerns below the tuning frequency of a sub, because that's where the driver begins to unload, meaning excursion skyrockets, and the possibility of mechanical damage arises. You can get around that, as you can all the other concerns, if you really know what you're doing. If you don't then take the easy route and use identical, or as close to identical as possible, subs.

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post #14 of 25 Old 11-04-2013, 02:06 PM
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I am currently running both sealed and a ported sub in my main setup and while a bit more tricky to get right, the results are indeed satisfying overall. Dealing with room modes was indeed my biggest problem. I'm glad this is finally being cleared up in this thread. smile.gif
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post #15 of 25 Old 11-04-2013, 04:03 PM
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Quote:
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Quote:
Originally Posted by DonH50 View Post

The transfer function for sealed and ported subs tends to be quite different, especially near and below the port frequency (natch). The phase issue can be resolved if your AVR will independently set the delay for the two subs. Or if they are the same distance from the LP. Or you have phase/delay control (continuous, not a polarity switch) on the sub (a.la. Rythmik and some of the higher-end Velodyne etc. subs -- I am not familiar enough with PSA or SVS to know what they offer). Or you can play with placement enough to smooth the response by physically moving the subs around. Note 1 foot (about 1/3 m) is about 1 ms in time.

I agree with everything except phase and delay are not the same thing. There's no such thing as a phase/delay knob. It either adjusts phase or it adjusts delay. Phase adjustment should only be used for integrating subs with mains, not for integrating 2 subs.

I understand that (my design career revolves around radar systems where the distinction is very important!) but different subs call it different things and implement it differently, natch. Adjusting the phase at one point does look like a time delay, or can, but I did not want to go too deep. Realistically, room modes dominate and that's what you have to deal with, usually by adjusting the sub's placement in the room. Setting the delay can help (or hurt) when trying to even out the response. Adjusting the phase is more important at the crossover point to avoid a hole at the crossover frequency. Ideally you'd have both a phase control for that and a true time delay function.

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post #16 of 25 Old 11-04-2013, 04:07 PM
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Quote:
Originally Posted by goonstopher View Post

Quote:
Originally Posted by DonH50 View Post

The transfer function for sealed and ported subs tends to be quite different, especially near and below the port frequency (natch). The phase issue can be resolved if your AVR will independently set the delay for the two subs. Or if they are the same distance from the LP. Or you have phase/delay control (continuous, not a polarity switch) on the sub (a.la. Rythmik and some of the higher-end Velodyne etc. subs -- I am not familiar enough with PSA or SVS to know what they offer). Or you can play with placement enough to smooth the response by physically moving the subs around. Note 1 foot (about 1/3 m) is about 1 ms in time.

I know it's a waste of low end but can't you just set a universal HPF right around the tuning frequency of the ported?

Would that help minimize phase issues below tuning?

Read what Bill Fitzmaurice wrote. Below tuning is usually a don't care, it's really above that point where you want to adjust things. A lot of ported subs I have seen already include a HPF and/or limiter to prevent the sort of issues Bill describes.

Problems can occur when the two subs have significantly different responses, causing one sub to overload whilst the other is ambling along.

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post #17 of 25 Old 11-04-2013, 06:01 PM
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Originally Posted by Archaea View Post

We mixed a pair of JTR caps today with a port tune of 20hz and a HPF engaged and four sealed 18" SI drivers and there was 0 issues in integrating. No phase issues, no dips around port tune, no loss of ability below the cap's port tune for the SI. This may be specific to room - but we were surprised in our little g2g - that there were no ill effects of matching the subs. They were all co-located. I'm going to throw up a compro thread tonight or tomorrow on the matter.

Post 139, 146, and 147 is my recent experience.
http://www.avsforum.com/t/1489801/bought-four-sealed-18-cabinets-on-a-wild-hare-direct-me-to-a-driver-setup-at-least-competitive-or-superior-to-jtr-captivators/120

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post #18 of 25 Old 11-05-2013, 06:01 PM
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I'm running seal and pr together , make sure delay is right and you are gold.
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post #19 of 25 Old 11-05-2013, 07:43 PM
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I'm running seal and pr together , make sure delay is right and you are gold.

Hey dat.. Do you mind if I ask what kind of PR sub are you running?

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post #20 of 25 Old 11-05-2013, 08:56 PM
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I have used identical and non-identical subs with good results. One of my favorite combos was 2 ported and a sealed subwoofer. One of the hardest sub integrations was with identical sealed sub. A lot depends on the setup and room. I would not shy away from non-identical subs if that is what I have to work with.

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post #21 of 25 Old 11-06-2013, 08:50 AM - Thread Starter
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For what it's worth, I asked Tom at PSA this same question and he said he didn't think it would be too much of an issue. It didn't sound like it would necessarily be ideal but it sounded like it would be fine if properly set up.

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post #22 of 25 Old 11-06-2013, 08:55 AM
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For what it's worth, I asked Tom at PSA this same question and he said he didn't think it would be too much of an issue. It didn't sound like it would necessarily be ideal but it sounded like it would be fine if properly set up.

If properly set up is what scares me...

It just seems like so many people are going sealed. It use to be ported, then gorns and now sealed is the rage.
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post #23 of 25 Old 11-06-2013, 09:08 AM - Thread Starter
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If properly set up is what scares me...

It just seems like so many people are going sealed. It use to be ported, then gorns and now sealed is the rage.

Yeah, I agree with the… "If properly set up"…… scare factor.

 

I think in the next few months I will be working on learning about REW and subwoofer set up etc…..

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post #24 of 25 Old 11-06-2013, 09:32 AM
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Sealed subs are smaller and easier to place than a similar ported sub. No port noise and that are great for music and HT.

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post #25 of 25 Old 11-07-2013, 10:24 AM
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