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post #1 of 26 Old 03-29-2014, 10:50 AM - Thread Starter
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I've always heard this is not a good idea..

I have two sealed 18's and am going to convert to ported boxes. If using a MiniDSP would it be a big no-no to mix ported and sealed? Was thinking about picking up 2 more Dayton 18's for a total of 4 subs. two would be ported, two would be sealed. I'm thinking I can EQ them individually with the MiniDSP having the two sealed on one EP4000 and the two ported on another EP4000. Thoughts?
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post #2 of 26 Old 03-29-2014, 12:25 PM
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Model both versions, see the difference in phase response. More pertinent, look at the difference in frequency response, excursion and maximum SPL and you'll see why there's nothing to be gained in mixing them.

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post #3 of 26 Old 03-29-2014, 03:03 PM
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Quote:
Originally Posted by Gomdaf View Post

I've always heard this is not a good idea..

I have two sealed 18's and am going to convert to ported boxes. If using a MiniDSP would it be a big no-no to mix ported and sealed? Was thinking about picking up 2 more Dayton 18's for a total of 4 subs. two would be ported, two would be sealed. I'm thinking I can EQ them individually with the MiniDSP having the two sealed on one EP4000 and the two ported on another EP4000. Thoughts?

Sealed will have far less group delay while ported will have noticeably higher GD. Subjectively speaking; you will have no accuracy in bass response. While you can reduce box size on ported ones to have GD close to sealed ones; but then you won't enjoy the high output trait of ported subs. So, I don't see the need to mix both. Hoffman's Iron law is in full swing wink.gif

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post #4 of 26 Old 03-29-2014, 03:08 PM
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Quote:
Originally Posted by braveheart123 View Post

Sealed will have far less group delay while ported will have noticeably higher GD. Subjectively speaking; you will have no accuracy in bass response. While you can reduce box size on ported ones to have GD close to sealed ones; but then you won't enjoy the high output trait of ported subs. So, I don't see the need to mix both. Hoffman's Iron law is in full swing wink.gif

ported vs sealed group delay:


IMO, just go ported and enjoy the extra output.
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post #5 of 26 Old 03-29-2014, 03:43 PM - Thread Starter
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Ok, thanks. Guess its a bad idea to mix. What about ported mains like DIY Tempests with sealed subs? I'm guessing that doesn't matter correct?
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post #6 of 26 Old 03-29-2014, 04:23 PM
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I have read, (no practical experience here on my part), that getting ported mains to blend with any subs might be difficult. I am unsure if sealed versus ported on the subwoofers end will make a difference, but, I would assume that sealed subs would be easier to blend versus ported ..
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post #7 of 26 Old 03-29-2014, 04:36 PM
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Quote:
Originally Posted by Martycool007 View Post

I have read, (no practical experience here on my part), that getting ported mains to blend with any subs might be difficult. I am unsure if sealed versus ported on the subwoofers end will make a difference, but, I would assume that sealed subs would be easier to blend versus ported ..

I asked Wayne about this when I was building the 4 Pi's
His response was:

"I do not think it is valid to consider sealed mains to be easier to integrate with multisubs. In fact, I'd say this presumption goes against the whole multisub concept, which is to blend sound sources having various phase relationships and physical locations in the modal region.
The additional extension from vented mains helps increase overlap between mains and flanking subs. The venting also reduces excursion. It is a good thing, all the way around."

This is regarding his multisub approach, but wouldn't the same apply to a subwoofer? (granted it isn't crossed nearly as high)
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post #8 of 26 Old 03-29-2014, 04:38 PM
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Quote:
Originally Posted by Martycool007 View Post

I have read, (no practical experience here on my part), that getting ported mains to blend with any subs might be difficult. I am unsure if sealed versus ported on the subwoofers end will make a difference, but, I would assume that sealed subs would be easier to blend versus ported ..
If this was an issue wouldn't all those happy tempest main owners have chimed in. I have ported mains with ported subs and they blend well.
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post #9 of 26 Old 03-29-2014, 04:52 PM
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In a lot of cases having multiple drives in multiple locations is good- there is a synergy and it helps to even out room effects. I doubt many owners would chime in about such a minor problem. I bet most don't even notice it.

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post #10 of 26 Old 03-29-2014, 05:05 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

Model both versions, see the difference in phase response. More pertinent, look at the difference in frequency response, excursion and maximum SPL and you'll see why there's nothing to be gained in mixing them.


What if you tweak the distance settings for all of the subs and put a HPF right at tuning for the ported subs? We tried this at Archaea's place and they measured well and subjectively it was an improvement over running just the ported subs or just the sealed subs.

I ask because I'm thinking about adding ported subs to my sealed sub setup.
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post #11 of 26 Old 03-29-2014, 05:49 PM
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I realize that the following graphs don't represent all the possible pitfalls of matching alignments, but here are my results:

 

Original sub(ignore SPL, it was not calibrated):

 

Ported PSW110(am I banned forever now?)

 

Upgraded to sealed dual opposed:

 

 

Added the Polk:

 

 

And finally, with EQ applied via miniDSP(no EQ below 20 hZ, i closed my two sets of french doors in my 2525 ft3 room.)

 

 

I know these are not DIY subs, but I felt this was relevant to the topic, and I've been lurking on DIY lately(the Polk needs to go)


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post #12 of 26 Old 03-29-2014, 08:18 PM
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Quote:
Originally Posted by braveheart123 View Post

Sealed will have far less group delay while ported will have noticeably higher GD.
Noticeable on a graph, but not in practice. For GD to be audible the numbers would have to be literally off the chart.

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post #13 of 26 Old 03-29-2014, 10:01 PM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

Noticeable on a graph, but not in practice. For GD to be audible the numbers would have to be literally off the chart.

This, hence the graph I posted wink.gif
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post #14 of 26 Old 03-30-2014, 02:42 AM
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Quote:
Originally Posted by Bill Fitzmaurice View Post

Noticeable on a graph, but not in practice. For GD to be audible the numbers would have to be literally off the chart.

I have a set of ears and can discern even the likes of Rythmik FV15HP in 2 ports open, low damping, rumble filter on, 20Hz hz to be not so accurate below 30Hz. All of that is attributed to high GD i.e. close to 72m/s at 20Hz. And I've heard many subs just like so many people on this forum.
But then at the same time, it's always a trade off between accuracy, output, extension, size.

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post #15 of 26 Old 03-30-2014, 05:18 AM
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It seems like integrating like subs is hard enough without mixing alignments. If a guy has them on hand sure try and see what you can come up with (the more gear you have on hand will/can be a help) but imo I would never buy or build a different alignment with the plan of mixing.

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post #16 of 26 Old 03-30-2014, 05:23 AM
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"I have a set of ears and can discern even the likes of Rythmik FV15HP in 2 ports open, low damping, rumble filter on, 20Hz hz to be not so accurate below 30Hz. All of that is attributed to high GD i.e. close to 72m/s at 20Hz."

are you sure gd is what you are hearing?

Listen. It's All Good.
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post #17 of 26 Old 03-30-2014, 05:55 AM
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Quote:
Originally Posted by LTD02 View Post

"I have a set of ears and can discern even the likes of Rythmik FV15HP in 2 ports open, low damping, rumble filter on, 20Hz hz to be not so accurate below 30Hz. All of that is attributed to high GD i.e. close to 72m/s at 20Hz."

are you sure gd is what you are hearing?
+1. Earl Geddes would have a field day with that statement, bringing up all sorts of actual technical aspects, starting with the period of a 20Hz wave.

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post #18 of 26 Old 03-30-2014, 06:20 AM
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The reason it works for ported mains is we XO well above tuning, otherwise it would be a problem IMO. Above tuning the power output of the port and driver are in phase, no problem. Below, they are down about 24db hopefully.

I disagree that it HELPS to have the port contribute to the multi sub ideology. The multi subs are still in phase, just at various locations in the room and exciting different modes. Yes, that's a different phase, but still seems different to me. I've often wondered about nearfield subs cause of this. Wether owners delay the nearfield ones or what.
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post #19 of 26 Old 03-30-2014, 06:28 AM
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Also keep in mind that 90 degrees out of phase isn't catastrophic. Not like 180. So ultimately it can work.
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post #20 of 26 Old 03-30-2014, 06:29 AM
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Quote:
Originally Posted by LTD02 View Post

"I have a set of ears and can discern even the likes of Rythmik FV15HP in 2 ports open, low damping, rumble filter on, 20Hz hz to be not so accurate below 30Hz. All of that is attributed to high GD i.e. close to 72m/s at 20Hz."

are you sure gd is what you are hearing?

The Damping switch set to Low on FV15HP in 2 ports open mode while gives the max output as it has the steepest slope, but it also jacks up GD. That gives away accuracy. I would like to set it to Medium or HIgh, but it gives up output in favor of accuracy. Um sure it is the GD that impacts accuracy below 30Hz keeping all things equal.

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post #21 of 26 Old 03-30-2014, 06:49 AM
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You might not be hearing the GD, you might be hearing the high pass knee. That would sound like a loss of accuracy.
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post #22 of 26 Old 03-30-2014, 07:37 AM - Thread Starter
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Here is a decent small but to the point read on this:

http://www.neumann-kh-line.com/neumann-kh/home_en.nsf/root/prof-monitoring_knowledge_faqs_general-answers_question13

Maybe a dumb question, but wouldn't audyssey X32 take care of the GD? It measures the subs independently, so hooking up both ported to one preout off the amp, and the sealed subs to the other and let it do it's thing.

I wouldn't base a system off of mixing ported and sealed from the get go, but if you have them on hand, it sounds like you can make it work with the right HPF's and delay settings. Does that sound correct?
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post #23 of 26 Old 03-30-2014, 07:47 AM
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Quote:
Originally Posted by tuxedocivic View Post

You might not be hearing the GD, you might be hearing the high pass knee. That would sound like a loss of accuracy.

HPF in ported alignment is imperative and is still active when damping is set to High/Medium.

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post #24 of 26 Old 03-30-2014, 07:55 AM
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Maybe a dumb question, but wouldn't audyssey X32 take care of the GD?

Higher GD close to tuning frequency is inherent trait of ported alignment cause of the application of HPF to protect driver from unloading below the tuning frequency. Sure you can reduce GD with a gentler slope (first order/2nd order) but then you compromise on the high output. To me, the purpose of having a ported sub is moot then.
Quote:
I wouldn't base a system off of mixing ported and sealed from the get go, but if you have them on hand, it sounds like you can make it work with the right HPF's and delay settings. Does that sound correct?

Yes and No. With gentle 1st order slope, you can bring it close to the performance of a sealed sub; but what's the need of ported then? You lose output.

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post #25 of 26 Old 03-30-2014, 08:23 AM - Thread Starter
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Originally Posted by braveheart123 View Post

Yes and No. With gentle 1st order slope, you can bring it close to the performance of a sealed sub; but what's the need of ported then? You lose output.

lol, actually thats a very valid statement and good point now that I think about it. What would be the point of adding ported if all i'd be doing was trying to shape the FR to match the sealed...DOH!

so now i'm thinking replace the sealed boxes with ported and add a couple of more ported down the road, or just build two more sealed and be done. i'm really wanting to port these things though! I'm also going to buy one of Erich's waveguide kits soon (still debating on which one) for LCR, hence the questions about ported mains.... decisions, decisions..
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post #26 of 26 Old 03-30-2014, 10:39 AM
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Originally Posted by Gomdaf View Post

lol, actually thats a very valid statement and good point now that I think about it. What would be the point of adding ported if all i'd be doing was trying to shape the FR to match the sealed...DOH!

so now i'm thinking replace the sealed boxes with ported and add a couple of more ported down the road, or just build two more sealed and be done. i'm really wanting to port these things though! I'm also going to buy one of Erich's waveguide kits soon (still debating on which one) for LCR, hence the questions about ported mains.... decisions, decisions..

Depends on what you want... Guys with ported subs in a car with a lot of cabin gain will still used ported but EQ the response back down after cabin gain to offer more headroom and less distortion redface.gif
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