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Re: Mono "flanking sub" [message #81636 is a reply to message #81624]

Thu, 29 October 2015 14:23

jonone
Messages: 67
Registered: October 2015

Viscount

Thanks for the reply, I'm surprised 50hz is localisable on the same plane as your speakers, eq can really help a single IMO. The antimode from dspeaker is great plug and play auto eq device.

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Re: Mono "flanking sub" [message #81637 is a reply to message #81624]

Fri, 30 October 2015 05:10

johnnycamp5
Messages: 354
Registered: June 2015
Location: NJ

Grand Master

It wasn't so recognizable from an audible standpoint , as it was from feel.

I have three couches in that room. One on the left, one on the right, and one towards the rear/center, facing the front wall.

When the sub wasn't centered, you/I could sense it, depending on where you were sitting.

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Re: Mono "flanking sub" [message #81638 is a reply to message #81637]

Fri, 30 October 2015 05:17

jonone
Messages: 67
Registered: October 2015

Viscount

I see, maybe the gain is to high? But I understand it maybe needed? That's another area multiple subs help.

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Re: Mono "flanking sub" [message #81640 is a reply to message #81638]

Fri, 30 October 2015 16:37

Wayne Parham
Messages: 18681
Registered: January 2001

Illuminati (33rd Degree)

Flanking subs are run pretty high - over 100Hz. They're a specialized application that's not unlike the helper-woofer of a 2.5-way speaker system. The thing that makes 'em unique is they are able to be offset from the mains in all three planes, so they smooth self-interference notches in the upper midbass and lower midrange. But their relatively high frequency content makes them localizable if they're placed too far away from the speaker they're flanking. Ideally, they are about three feet below, beside and behind the main speaker.

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Re: Mono "flanking sub" [message #81641 is a reply to message #81624]

Fri, 30 October 2015 17:58

johnnycamp5
Messages: 354
Registered: June 2015
Location: NJ

Grand Master

Hey Wayne.

Are these self interference notches caused by reflections, the byproduct of being in a room, or would they still occur outdoors, in open space?

About crossover frequency:
Don't the 4pi's graph relatively flat down to around 50hZ?
Setting an active crossover on a typical plate amp/sub amp to 100hZ would certainly create a large overlap in the 50 to 100hz range would it not?

I know with my last set of speakers (B741 scan speak) 100hZ was way too high for my liking, and everything sounded very muddy or "subby".
The farther I cranked the crossover frequency down, the better the overall sound became.

Perhaps there is something wrong with my sub. It does use a passive radiator, but I don't know why that would be a problem.

Maybe I'm just not that much of a sub guy. There is plenty of music content I listen to through the 4pi's, and I shut off the sub all together.
In my short time with them, they provide some of the best enjoyment Ive ever had from all my favorites, The old "the band is in the room" experience. And that's without a sub.

Good luck jonone.

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Re: Mono "flanking sub" [message #81643 is a reply to message #81641]

Sat, 31 October 2015 13:21

jonone
Messages: 67
Registered: October 2015

Viscount

I'm sure Wayne will answer but yes the interference notches are from the room, and the speakers I'm guessing will be flat outside.
If you don't high pass your mains and you overlap the sub and mains then it makes sense to roll the sub in were the mains roll off to avoid a lump in the bass if they sum together.( or eq them)
If your sub is not that clean then the lower the crossover the better Imo, I had a sub before with a peerless driver and I couldn't cross it over 60hz really as it would get a bit boomy, although eq helped, I've also heard people say passive radiators can be boomy?
The driver I have now is super clean and measures more like a midrange driver and can be used as such, it has a very low le and 3 shorting rings, 150hz crossover is not a problem and I havent eq'd it yet.
Subs don't make good midrange drivers and vice versa so I think your better of using something like the acoustic elegance td series like I am for flanking subs.

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Re: Mono "flanking sub" [message #81645 is a reply to message #81643]

Sat, 31 October 2015 15:37

Wayne Parham
Messages: 18681
Registered: January 2001

Illuminati (33rd Degree)

Self-interference notches are from room reflections. The speakers measure flat outdoors.

The whole concept of multisubs - which flanking-subs are a specialized type - is to create dense interference that smoothes the average sound field. This requires multiple sound sources in the same frequency range. So we want to blend the mains and the subs through the modal region.

Please read the π Speakers FAQ for more information.

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Re: Mono "flanking sub" [message #81656 is a reply to message #81624]

Sun, 08 November 2015 13:52

jonone
Messages: 67
Registered: October 2015

Viscount

This is my centre seat, in red are my mains on there own, in green is my mains +mono flanking sub, im using a mini dsp with a 150hz Bessel crossover and time aligned to the right speaker which it sits below.
this is with adding 6 db boost to 100hz and 180hz just to the flanking sub.

This is the left seat mains in green this time and mains + flanking sub in red(confusing, sorry) I know it's caused a few slight problems elsewhere but that's a big hole filled in!

It needs more tweaking as it's a balance over the three seats, do people generally boost eq points on flanking subs or just use the phase/ delay to flattern the response?

The mains and flaking sub are time aligned, is that wrong? Or should I adjust the delay to get the flattest response? ....... I get confused! Embarassed

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Re: Mono "flanking sub" [message #81657 is a reply to message #81656]

Mon, 09 November 2015 12:57

Wayne Parham
Messages: 18681
Registered: January 2001

Illuminati (33rd Degree)

We can see that the flanking sub approach is smoothing the mains through reduction of the notch around 95Hz - 100Hz. This is largely because of the sub's physical relationship to the mains - Even though there's just one helper woofer, it's still a couple feet away in each plane. So we can see your mono flanking subwoofer approach works pretty well for smoothing.

From your measurement data, I'd say this is a workable solution provided the single summed subwoofer doesn't throw off the image. That was my biggest concern really - The flanking sub approach requires moderately high-frequencies blended in the subwoofer and the main it is flanking.

Lower midrange can be localized, giving perceptional cues of the position of the source. Having a shared flanking subwoofer between the mains can smooth the self-interference notches - as your measurements have shown - but I was concerned it might mess up the stereo image. I suppose that's a subjective thing, and might be content sensitive. Some (nearly mono) material might sound very good in a single flanking sub setup, while others (with highly panned content) might not work as well.

As for the comments/questions about "time alignment", remember that is impossible to align in three dimensions. You can synchronize in one position, but not all. That's what the multi-sub and flanking-sub approaches are all about. They mitigate anomalies that are created specifically because sound sources and their reflections cannot possibly be time aligned.

Thanks for your feedback on this single summed flanking sub approach. It is very useful and interesting to see.

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Re: Mono "flanking sub" [message #81658 is a reply to message #81657]

Mon, 09 November 2015 14:44

jonone
Messages: 67
Registered: October 2015

Viscount

Hi Wayne, thanks for the comments.
The flanking sub is directly below the right hand speaker, so only a couple of feet away in one direction as its down firing, there both very close to the wall.
Like this:

I would move it to be between the stereo pair but it's more practical as it is with kids! I honestly don't notice any smearing of the stereo image on the music I listen to, but in the test tracks I posted it was admittedly a little bit better without the flanking sub in but not enough to bother me.
It seems you get enough cues from the higher frequency's for imaging?
In an ideal world I would run a stereo pair but it's good enough for me on a budget, I'm lucky enough to have the one flanking sub and nearfield sub In my room and budget.
Can you recommend some content with panning?
Ok so the response can't be time aligned for multiple seats so you just adjust the delay for best response across the seats?
The response doesn't seem to change that much either side of where I have the delay set but seemed to get boomy if I delayed it to far? Is this possible?
Any comments on the 200hz dip, it obviously changes with the xo delay you apply, I'm using 150hz at the moment.
Also do you eq flanking subs? And if so do you eq them with or without the mains?
Thanks.