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Why do you not see this in plans?
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tb_mike View Drop Down
Old Croc
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Points: 2744 		Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 19 April 2007 at 1:28am
That meyer multi sub above probably is setup for a cardoid polar.

gazman - is that in theory or to your ears?
Sure,we have out of phase 'late'bass emanating from the port,but does it matter at that frequency.

The phase wrapping on a graph looks bad,but one has to confer with psycho acoustics to see what the ear can hear.


Edited by tb_mike - 19 April 2007 at 1:29am
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Points: 100 		Post Options Post Options   Thanks (0) Thanks(0)   Quote gazman Quote  Post ReplyReply Direct Link To This Post Posted: 02 May 2007 at 7:41pm
Hi Mike, sorry for late reply! I'd say its both the theory and the practice..think about using multiple types of sub over the same frequency range and all the horribleness that causes, same problem basically. As far  that Meyer sub, obviously set up for cardiod use, weird they've used 1x 18" at the front with a 15, then 2 more 15's to provide the cancelling waves. Wonder how the 15 and 18 are setup to coherently sum together...
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Gazman- The 18's and the 15's on the front baffle cover different frequency ranges and have separate subenclosures. The pair of 15's on the rear also have their own subenclosure and tuning.

Tom- Did my homework: Each 18" driver in the PSW-6 IS double-tuned within its own cavity (via employing 2 sets of vents with differing lengths and Sv), as are the following Meyer Sound enclosures:

MTS-4A, 18" driver subenclosure (only)
650P double 18" sub
700-HP double 18" sub
600-HP double 15" sub
CQ series 2-way, fullrange cabs
(This might not be a complete list.)

EAW does the same thing with at least one of their older designs. This is not a new design tactic, but it's tricky to get the tunings right.

John Meyer can be contacted through the Meyer Sound website (www.meyersound.com).

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This contains the descripcion of the box MTS-4. It even tells you the size and lenghth to each chamber.

http://www.patentstorm.us/patents/5602367-de0scription.html

I was wondering. I have heard stacks of meyer 700HP subs and i see different port size i can assume they are double tune also.
 
Anyway how can we acomplish our own designs double tune. What are the tools we need to do it?
 
I don't think john meyer will answer questions on port size and length on the 700hp or other cabinets they produce.
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Ibex View Drop Down
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Originally posted by Cuppa Joe Cuppa Joe wrote:


Tom- Did my homework: Each 18" driver in the PSW-6 IS double-tuned within its own cavity (via employing 2 sets of vents with differing lengths and Sv), as are the following Meyer Sound enclosures:

MTS-4A, 18" driver subenclosure (only)
650P double 18" sub
700-HP double 18" sub
600-HP double 15" sub
CQ series 2-way, fullrange cabs
(This might not be a complete list.)

EAW does the same thing with at least one of their older designs. This is not a new design tactic, but it's tricky to get the tunings right.

John Meyer can be contacted through the Meyer Sound website (www.meyersound.com).


Whereon do you relate to this fact? I can't find any information concerning your claim...

...maybe the diverse sized ports have different lengths to get the same tuning frequencies for each one?!
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Points: 298 		Post Options Post Options   Thanks (0) Thanks(0)   Quote DjMidKnight Quote  Post ReplyReply Direct Link To This Post Posted: 15 November 2009 at 9:02pm
hermm.. i might be overstepping my self here BUT from what i understand that if you put ports in a common cavity of varying lengths and sizes the combind volume of air that can push through them all will set the tuning of the box. of course there will be differing amounts of resistance through each port but the sum of exchange would be the calculated frequency.
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Points: 5992 		Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 16 November 2009 at 3:06am
Double tuning still gives only one resonant frequency per tuned chamber.
 
gedlee is offline gedlee vbmenu_register("postmenu_1832150", true);  
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Quote:
Originally posted by Josh Ricci
I've done a little bit of rough testing on having 2 unequal length ports in an enclosure and they act like a port or ports that split the difference. Basically if you have a 16" port and an 10" port they will act like a pair of 13" ports at least as far as the tuning is concerned. Perhaps it could be useful for diminishing pipe resonances or something.

 

The staggered ports act as one as a lumped mass, but have different resonances within the tubes when they have internal standing wave resonances.


This is precisely what happens both theoretically and in practice. I typically use three, have used five, all different lengths. Just take the average if they are all the same diameter. (Thats not exact, but close enough).
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Edited by _djk_ - 16 November 2009 at 3:19am
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Ibex View Drop Down
Young Croc
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Originally posted by MythBusters MythBusters wrote:



Myth, that Meyer Sound Subs are double tuned within its own cavity, clearly busted!
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Ibex View Drop Down
Young Croc
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Maybe Cuppa Joe was talking about such a system design?!

DCR - Double Chamber Reflex

DCR - Double Chamber Reflex
http://www.claudionegro.com/projects/speaker/dcr/dcr.html

It's obvious that the Meyer Subs have different sized ports, it possible that they are utilizing the DCR technology:
Meyer Sound 700-HPMeyer Sound 700-HP 

Edited by Ibex - 16 November 2009 at 8:29am
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Ibex View Drop Down
Young Croc
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...but there is nothing mentioned on their web site in the sound lab:
http://www.meyersound.com/support/forums/talkshop/subs.htm

Myth still busted!
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Points: 249 		Post Options Post Options   Thanks (0) Thanks(0)   Quote MusicXtra Quote  Post ReplyReply Direct Link To This Post Posted: 16 November 2009 at 9:44am
Each bass reflex cabinet is a simple Helmholz resonator, so it is impossible to give it two resonance frequenties.
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G-Man View Drop Down
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Points: 41 		Post Options Post Options   Thanks (0) Thanks(0)   Quote G-Man Quote  Post ReplyReply Direct Link To This Post Posted: 17 November 2009 at 4:02pm
There was a HiFi speaker company a few years ago, that used round ports that were put in at an angle and the ends were cut at an angle, with the idea being  similar to what you are talking about here (one port with a variable length). But when you look at the geometry of the thing, all you have in the end is a straight oval port. 

You are better off using multiple ports (of any length) simply because of the reduction in port velocity and port noise, but other then that, not much benefit.

As a side note, even though they are mostly used in HiFi market, flared ports are the best way to go.
If it was easy, everyone would do it!
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