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Ported and sealed subs in the same room?
Ported and sealed subs in the same room?
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Old 17th January 2018, 10:36 PM   #11
globalplayer is offline globalplayer  Germany
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Originally Posted by scottjoplin View Post
Ok, have you read about double bass arrays? These work best in a symmetrical room, you don't need any traps, and theoretically there are no room modes.
Agreed.
You will need a dsp for the delay.
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Old 17th January 2018, 10:38 PM   #12
scottjoplin is offline scottjoplin  Wales
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I'm tempted to try this as a simpler version DP_woofer_room
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Old 18th January 2018, 02:02 AM   #13
weltersys is offline weltersys  United States
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Originally Posted by homebuilder View Post
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..

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Old 18th January 2018, 12:36 PM   #14
homebuilder is offline homebuilder  United States
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Default 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!
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Old 18th January 2018, 03:17 PM   #15
scottjoplin is offline scottjoplin  Wales
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Quote:
Originally Posted by homebuilder View Post
It sounds like in general you should not mix sealed and ported.
I think the consensus is that if you are using multiple subs to mix them is a good idea, you'd do worse than to follow Earl Geddes' advice, and if you can't measure you could do it by ear
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Old 18th January 2018, 07:20 PM   #16
weltersys is offline weltersys  United States
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Quote:
Originally Posted by homebuilder View Post
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

Last edited by weltersys; 18th January 2018 at 07:22 PM.
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Old 18th January 2018, 07:36 PM   #17
bentoronto is offline bentoronto  Canada
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Ported and sealed subs in the same room?
Quote:
Originally Posted by weltersys View Post
...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.

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Last edited by bentoronto; 18th January 2018 at 07:40 PM.
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Old 19th January 2018, 07:09 AM   #18
homebuilder is offline homebuilder  United States
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Default 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.
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Old 19th January 2018, 03:51 PM   #19
homebuilder is offline homebuilder  United States
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ScottJoplin:

I just read that paper you linked to in your earlier post. That is very, very interesting. As stated in the article, it is a simple test to carry out. I already have all the requisite subs.

Thanks for that suggestion!
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Old 19th January 2018, 05:53 PM   #20
scottjoplin is offline scottjoplin  Wales
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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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