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Old 26th October 2013, 02:44 PM   #1751
gedlee is offline gedlee  United States
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Quote:
Originally Posted by weltersys View Post
Earl,

Are you saying that there is no difference in room modal excitation whether the radiator is a dipole or a monopole?
Of course there is a difference, but you cannot view it as a directivity response problem. In a room that has discrete modes the wave is restricted to move in only one direction per mode (well actually two orthogonal directions). The idea of directivity requires the response of a source along a variable direction, but the sound cannot travel away from the source in an arbitrary direction if there are discreet modes. As Markus says it is best to view LF sources of all types as sums of discrete sources separated in space and phase. This is always safe, but looking at it from a directivity standpoint is dangerous.

It is this kind of thinking that leads to false concepts like "Dipoles excite fewer modes." which is false. You can see this if you view a dipole as two sources out of phase and separated by a distance. The dipole will actually tend to excite more modes, which of course is desirable, not the other way around.
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Old 26th October 2013, 06:06 PM   #1752
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Originally Posted by gedlee View Post
The idea of directivity requires the response of a source along a variable direction, but the sound cannot travel away from the source in an arbitrary direction if there are discreet modes. As Markus says it is best to view LF sources of all types as sums of discrete sources separated in space and phase.
Agreed.

As Markus also said:
"The direct sound is swamped by the room response. So the radiation pattern isn't exactly meaningless but just one parameter in getting smooth response in frequency and time."

After further review of the tests posted in #1730, appears that time alignment has less to do with smooth response at my listening position, and "luck" at choosing the right place to put my couch in relation to the room modes more .

One interesting finding was that opening the rear room doors increased LF +8 at 33 Hz at the listening position.
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Old 26th October 2013, 06:31 PM   #1753
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Originally Posted by gedlee View Post
As Markus says it is best to view LF sources of all types as sums of discrete sources separated in space and phase. This is always safe, but looking at it from a directivity standpoint is dangerous.
My traces in #1713 illustrate nicely the complex interaction of enduring modes arising from room shape and the influence of seat location. The room modes are clearly enduring, but the two traces are distinctly different as well. (If you wanted to name the major artifacts, you'd name the room modes.)

Without even whispering a word about human hearing that might give a major twist to this discussion, it is easy to fall in fallacious thinking by confusing the simplifying assumptions and inspirational diagrams used to propel analysis with the sound of music introduced into a room. We all simplify to analyze, I'm just saying (pending better and better 3-D waterfall charts) there's a big step between that and the final audition.

Although thinking about the complex sound of dipoles might give the more analystic among unipole fans the heaves, it sure seems to fill-the-bill for dipole fans. Ditto for the topic of this thread: multiple subs.

Ben
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Last edited by bentoronto; 26th October 2013 at 06:36 PM.
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Old 26th October 2013, 08:24 PM   #1754
gedlee is offline gedlee  United States
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Originally Posted by bentoronto View Post
Without even whispering a word about human hearing that might give a major twist to this discussion, it is easy to fall in fallacious thinking by confusing the simplifying assumptions and inspirational diagrams used to propel analysis with the sound of music introduced into a room.
Huh!?
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Old 1st July 2014, 03:37 PM   #1755
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Default Does multi sub approach also work in smaller rooms?

Hi Earl,

Will the same multi sub approach also work in smaller rooms, something like 15x13x10?

The reason why I ask is that in OptimalPlaybackInSmallRooms.ppt you have defined a small room as 20x14x10. Some rooms may be smaller like above.

Thanks,
Goldy
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Old 1st July 2014, 03:58 PM   #1756
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Originally Posted by goldyrathore View Post
Hi Earl,

Will the same multi sub approach also work in smaller rooms, something like 15x13x10?

The reason why I ask is that in OptimalPlaybackInSmallRooms.ppt you have defined a small room as 20x14x10. Some rooms may be smaller like above.

Thanks,
Goldy
The smaller the room, the more pressing are bass issues. For example, room modes are in more audibly detectable ranges. So having another bit of control (by working with multiple subs) is better. Of course, the smaller the room, the harder it is to decorate your room with many subs.

Aim for heterogeneity of box types too.

B.
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Old 1st July 2014, 04:02 PM   #1757
gedlee is offline gedlee  United States
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Quote:
Originally Posted by goldyrathore View Post
Hi Earl,

Will the same multi sub approach also work in smaller rooms, something like 15x13x10?

The reason why I ask is that in OptimalPlaybackInSmallRooms.ppt you have defined a small room as 20x14x10. Some rooms may be smaller like above.

Thanks,
Goldy
Multiple subs always works regardless of size. The specifics of each room are so widely varied that you really need to simulate the situation using something like the software on my site.
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Old 1st July 2014, 04:03 PM   #1758
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Originally Posted by gedlee View Post
Huh!?
I'm sorry to have neglected any comment from Earl, even if just "huh."

My favourite example of relying on your eyeballs instead of your ears-on-music is comb filtering. Few diagrams are as dispiritingly horrible as comb filtering. But there's reason to doubt comb filtering spoils music much or at all.

Ben
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Old 1st July 2014, 07:52 PM   #1759
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Quote:
Originally Posted by bentoronto View Post
SNIP......
. Few diagrams are as dispiritingly horrible as comb filtering. But there's reason to doubt comb filtering spoils music much or at all.
Ben
I have built a number of 4 element column speakers, improving each design over time.
My latest has 4 Dayton PA-130's and a small horn.
I cross them to woofers and then subs at 153 Hz BW4.
I think they sound great.
They are so efficient I can not tolerate full volume with a 40 watt amp.
.
My Daughter comes over and says "How can you stand all that swish, swish"

I guess everyone has their own expectations and hears what they want to.
Subjectivity seems to swamp reality.

P.S. I fully subscribe to the Multiple Sub approach.

Dave

Last edited by Shadydave; 1st July 2014 at 07:53 PM. Reason: Spelling
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Old 5th November 2015, 10:14 PM   #1760
rtrt is offline rtrt  United Kingdom
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Default Practical inputs please - sub x 2 purchase soon

Making my way through this mammoth thread, am up to page 80 and have paused just now to make this post, which is longer than intended - so apologies in advance!

I have some time off next week, where i'd like to purchase a couple of additional subs and put Earls method into practice. So i'd like to ask for some practical inputs please - recognising that the answers might well be in the next 70 odd pages, but i might not get there in time...

My current single sub is an SVS SB12-NSD - Measurements (Here)

As you can see from the measurements, the sub though sealed has some quite high Group Delay.

1. From the first 80 pages or so I'm not clear if GD in the subs is removed as a potential issue with Earls approach?

2. If it is a problem, should I try to address it by siting this sub close to the listening position (as it is today)?

3. If GD is a problem then the other 2 purchases should presumable be low GD subs?

My interpretation of whats been said around the choice of sub so far, i.e. being fine at the cheaper end of the spectrum, probably implies that GD isn't significant - but i'd really like some input before buying.

Currently my intent is to buy a couple of 10 inch subs from the same manufacturer. I was going to go for ported, the ones where you get plugs to change the configuration between 2, 1 and 0 ports and run them configured differently. That way I get the required 3 differently behaving subs.

4. Or should I get a 12 and 10 inch ported instead, to maximise the differences? I'd prefer 10 x 2 simply because they're smaller!

I'd put the 12 inch SB12 in the corner next to the mains (hence the GD concern) and the other 2 as per Earls suggestion and Markus's page (Here)

Some hopefully useful context re my current setup.

Room is as follows;
  • 2.65m x 3.6m x 4.5m (4.8m in 2 alcoves)
  • 3 solid walls (brick), 1 partition wall, wooden floor with room underneath and plasterboard ceiling into loft space above.
  • Heavily furnished and messy enough that I've never been tempted to share any pictures!
Mains are -3dB at around 35Hz, with much better GD than the SB12 sub, though I've never been happy with the bass. Hence the sub purchase which did improve things to be fair.

I have a Umik 1 and have 'played' with REW before, but tbh I didn't have access to a hardware parametric equaliser and so 'made do' with the inbuilt parametric equaliser in VLC - less than ideal.

Likely if I still need EQ, that i'd go the miniDSP (possibly Dirac) route, though i'd like to try the subs on their own first.
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