Ported and sealed subs in the same room?

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Greetings:

I've read that you should not mix sealed and ported subs in the same room due to phase issues. I don't grasp that concept fully, or even know if that is correct.

I currently have (3) powered subs. Each one has a 12" driver, and a 12" passive radiator. They are commercially manufactured subs. They are approximately 18" x 18" x 18". I do not play them head-banging loud. I'm looking for high quality sound.

Our new audio room, which is 4000 cubic feet net, is mainly for 2 channel, but will also serve as a home theater. I want to build (2) more subs, and am leaning heavily towards buying the new assembled cabinets from Erich at DIYSOUNDGROUP. Sealed, 5 cf, for an 18" woofer. The woofer I'd prefer to buy is the Acoustic Elegance TD-18. I've owned several sealed subs, and prefer the sound over other designs I've heard. My current main speakers are ported, but I also have Magnepans, and am restoring a pair of vintage ElectroVoice Marquis.

Is this going to create issues? Should I be focusing on ported designs, or use a passive radiator like my existing units? Space is not an issue. I've long considered doing infinite baffle woofers, but that forces me to place speakers and equipment on walls where it is less desirable functionally.

Thank you in advance for any helpful advice.
 
Greetings:

I've read that you should not mix sealed and ported subs in the same room due to phase issues. I don't grasp that concept fully, or even know if that is correct.

1)I currently have (3) powered subs. Each one has a 12" driver, and a 12" passive radiator.
2) I want to build (2) more subs, and am leaning heavily towards buying the new assembled cabinets from Erich at DIYSOUNDGROUP. Sealed, 5 cf, for an 18" woofer.
3) My current main speakers are ported, but I also have Magnepans, and am restoring a pair of vintage ElectroVoice Marquis.
4)Is this going to create issues?
5)Should I be focusing on ported designs, or use a passive radiator like my existing units?
1) A passive radiator has the virtually the same phase response as a ported cabinet with the same Fb (Box tuning frequency). A "powered sub" usually has some sort of analog or digital processing which will alter the phase response in some fashion dependent on digital latency and filter topography.
2) A sealed box will not have the same phase response as a ported box unless the frequency response is identical.
3) Depending on the crossover frequency and Fb of the ported cabinets, they may not be "in phase" with the upper range of the subs.

In general, if the phase response is within 1/4 wavelength (90 degrees) two cabinets can be considered "in phase". At 100 Hz, 1/4 wavelength is 2.8 feet, but at 30 Hz 9.4 feet, so you must consider phase as a "moving target".

Art
 
Weltersys:

Art:

Thank you for your reply. Based on my very limited knowledge of what you describe, it sounds like I would need to acquire measurement gear in order to determine how my current subs perform, and then attempt to match that as closely as possible with any new subs?

I have no idea if any digital processing is going on with those subs. They have a modest amplifier, and an adjustable crossover, which I have set at 50 hz. The subs are units built by TAD, and unfortunately marketed under the Pioneer logo. Which is why they did not sell. They were designed by Andrew Jones as entry level TAD's.

The other thought I have had is to use a completely different set of subwoofers for home theater, than for 2 channel. I have plenty of amplification laying around to do that.

In the past, I've noted that John at Acoustic Elegance seems to be a fan of passive radiators, so that doesn't pose any problem in itself. My lack of knowledge is the issue here.
 
I would not do it.
(Different enclosure types/speakers play the same freq range).

What could work though, use a dsp and let the different enclosure types/speakers play different freq bands according to their strengths.
Like one enclosure type plays 20 to 50hz and the other 50 to 100 hz.
For example.
 
You should always take any opportunity to get heterogeneity into your speaker system.

Talking about phase is often a naive textbook-diagram kind of simplistic thinking, rarely meaningful at your own music chair. Unless you are exactly equal distance from all drivers and all ports AND playing in an anechoic space, guessing the precise phase at your ear is just guessing. Stick with plain freq response and trim to taste.

So your best bet is to have averaging statistics on your side. Do the math.

B.
 
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Beltoronto--?

Okay, that went right over my head. Not the language....I suck at math, which is the only subject that has ever stymied me.

I have no concept of how to apply your comment to my situation, other than that I should listen with my ears. I do that now. I simply don't understand the entire subject of "phase" and how that applies to my speakers or environment.

I believe that it is necessary to invest in some measurement gear, in order to treat my room, and get things placed properly.

Right now, my thought is to plan for a couple new subs this Spring or Summer, and what they should look like, and how they should be built. I'm busy with my other projects, so this is going to mean either hiring my cabinet maker to build from a set of plans, or buying something like the cabinets I mentioned in my first post...the DIYSOUNDGROUP units.

There are many people on this site who are really into the technology, the measurements, etc. I'm not one of them. My fall back position if I cannot get what I want from "DIY" is to go with "DIFO". Do It From Others.

In my first post, I alluded to an issue that to me is of concern....I have radically different speakers. Ported TAD, Magnepan, and vintage EV horn-loaded, Alnico drivers.

I'm not a bass freak. I want to experience the concept of distributed bass. I bought my TAD subs for $1000 each, new. That was a bargain in my mind. Where do I go from here?
 
The concept of heterogeneity is simple. There are resonances and piling-on of loudnesses arising from various sources in speakers and rooms. No easy way to stifle them adequately. So best to even-out the peaks and valleys by avoiding clones* (except, of course, for matching your basic stereo pair, north of the non-directional bass band) and, instead, mix and match. That way things will average out better.

B.
*for example, not have multiple copies of the same subwoofer and arranging furniture so that you have least parallel surfaces the same distance apart. Just to give two examples.
 
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ScottJoplin and BelToronto

Ah. Interesting. I have read some of Geddes work, and that is the main reason behind my interest in distributed subs. I will do more reading.

BelToronto: Okay, I see where you are going with this. Although it isn't strictly limited to sub-woofers, one concern I have with my new room is that it is nearly a square at 21.5' by 22.5' The ceiling is 9'. I'm trying to educate myself on how to treat different walls, and what types of furnishings to put in the room to break up undesirable modes. For example, I'm looking at those thin bricks to put on one wall to create an irregular surface. Also looking at bass traps, live-end/dead-end, carpeting, etc.

I do want to mention that all of the people who have responded so far are people whose comments I have read for many years. I really appreciate any help I can get.

Although this is off topic somewhat, last night I came across "Funk" woofers. Very interesting. My cabinet-maker was at my house today measuring up for some new kitchen cabinets, and we took about 30 minutes to look at sub cabinets, and 18"-21" drivers. Wow.
 
Art:

Thank you for your reply.
1)Based on my very limited knowledge of what you describe, it sounds like I would need to acquire measurement gear in order to determine how my current subs perform, and then attempt to match that as closely as possible with any new subs?
2)I have no idea if any digital processing is going on with those subs. They have a modest amplifier, and an adjustable crossover, which I have set at 50 hz. The subs are units built by TAD, and unfortunately marketed under the Pioneer logo. Which is why they did not sell.
3)The other thought I have had is to use a completely different set of subwoofers for home theater, than for 2 channel. I have plenty of amplification laying around to do that.
1) Could help, but to match phase of differing cabinets completely will require implementation of FIR filters. Due to room reflections, a perfect phse match will still not correct room response, so a perfect phase match may not be worth the cost.
2) Likely the adjustable crossover is either analog, or a digital analog equivalent. Each "pole" in a crossover adds 90 degrees of phase shift, and a digital crossover adds a minimum of around 2ms of delay on top of the phase shift.
3) Generally, "the more, the merrier" as long as they are not too far out of whack (phase) at the listening position.

The "Phase Wheel" diagram below from the "SRS Speaker and Enclosure Intro.pdf" may help you start to understand phase and it's consequence on frequency response. Just like turning through 360 degrees of compass headings puts you back "on track" same with phase, but that spin has time associated with it :^)

Contrary to the "EQ/Tone controls ruin phase response" myth, the filters used to correct frequency response also tend to correct phase response..

Art
 

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ScottJoplin

I have seem some information on subwoofers set up in that configuration. I had forgotten about that. I believe it was when I was looking at Nyal Mellor's website about room design and treatment.

If that doesn't excite room nodes, does that negate any issues with phase? Aren't they different things?

Weltersys sent some info that helps to explain it somewhat, but now people are talking about applying FIR's, DSP, etc. I'm looking for the easiest solution to avoid having to delve into things I know nothing about, and am unlikely to ever understand. So a couple of really basic questions:

1. It sounds like in general you should not mix sealed and ported. If I go with ported or passive woofers, do I have to try to match the frequency response of my existing subs? Could I build larger, or more efficient subs and use them with what I have?

2. If I did mix the two types, and had them distributed around the room roughly 10-13 feet from the listening position, is that likely to create audible problems?

3. Does it matter much in any of those scenarios what the crossover point is? I tend to cross subs over low: never over 80, and usually at 50-60.

Thanks!
 
If that doesn't excite room nodes, does that negate any issues with phase? Aren't they different things?

Weltersys sent some info that helps to explain it somewhat, but now people are talking about applying FIR's, DSP, etc. I'm looking for the easiest solution to avoid having to delve into things I know nothing about, and am unlikely to ever understand. So a couple of really basic questions:
1. It sounds like in general you should not mix sealed and ported. If I go with ported or passive woofers, do I have to try to match the frequency response of my existing subs? Could I build larger, or more efficient subs and use them with what I have?
2. If I did mix the two types, and had them distributed around the room roughly 10-13 feet from the listening position, is that likely to create audible problems?
3. Does it matter much in any of those scenarios what the crossover point is? I tend to cross subs over low: never over 80, and usually at 50-60.
Homebuilder,

The easiest solution to avoid having to delve into things you know nothing about is to not do anything ;^).

Room nodes and modes will screw up the sub response regardless of attention to phase and time alignment.

1. "In general" sealed and ported cabinets may have quite different phase response, but in specific, they can be near identical if the frequency response is also near identical. You could build larger, or more efficient subs and use them with what you have, and also have them match the frequency and phase response of your existing subs.
2. This approach can be useful in reducing room mode problems, but you had dismissed it in your OP: "I've long considered doing infinite baffle woofers, but that forces me to place speakers and equipment on walls where it is less desirable functionally."
3. Unless the subs are co-located with the mains, a crossover point above 100 Hz will result in some degree of "image wandering" as instruments or vocals raise and lower in pitch around the crossover point. Below 80 Hz in a small room with clean subs imaging should not be a problem with distributed subs. Using more subs (assuming they "play well" with each other) increases efficiency, lowering excursion and power required for a given SPL.

Room modes and sub placement in relation to the listening position can make huge differences in response, they are as important as phase and timing response.

Art
 
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...Unless the subs are co-located with the mains, a crossover point above 100 Hz will result in some degree of "image wandering" as instruments or vocals raise and lower in pitch around the crossover point...
While Art, once again (in this thread) makes valid points, I'd like to qualify the thought quoted above.

My view that a crossover up to maybe 130 Hz works very well for music has been supported by others who worked that way too, provided you are not talking about lab testing. But it requires clean subs with few give-away upper harmonics and sharp slope crossovers. Nice when a sub has about 2 octaves.

Moving the crossover from 80 to, say, 120 Hz vastly helps you in making nice sounds above that crossover and with quite small, affordable, quality mid-range drivers available to use. And you can then move the next crossover point up to place where again, high quality dome tweeters become feasible.

BTW, I don't think I've heard any good acoustic reason why you'd want matching subs, other than maybe for the Welti set-up.

B.
 
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room nodes

Weltersys: thank you for all of that information. I'm going to read up on some of the topics you have elaborated on, to get a better understanding. I just want to clarify one point you alluded to, from my OP: that about infinite baffles in my room. The room is in a basement, and has one fairly large egress window in the NE corner. It also has a shared wall with other rooms that I cannot use as the back chamber for the infinite baffle. It also happens to be the wall you walk into the room from, so anyone entering the room would walk in front of the sitting position. If just doesn't work, which is too bad. I had considered framing one of the walls out about 3-4 feet to create the 10x VAS that the Cult of the Infinitely baffled recommends.

Beltoronto: I have not tried a higher crossover point with these speakers, or my mains. Partially because the room they have lived in the last 2 years was just such a difficult room with walls of glass, hard wood floors, etc that I just listened to it as is, and kept working on the new room. I'm still not done, but am making progress. I'm looking forward to getting the speakers set up properly, and learning how to do some measurements.

Thank you everyone for your comments. There is time to consider all of this, learn a bit more, and make changes and additions as the process unfolds.
 
I'd be interested to know how you get on. It shouldn't pressurise your room like a monopole, you may not like that effect, I do however, I find pressure uncomfortable on my ears, one of the reasons I use open baffle speakers. Are you able to reverse the phase on one and provide the requisite delay?
 
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