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#35102 - 03/26/05 07:57 PM Max Extension via Port Plugging
LaserMark4 Offline
Deputy Gunslinger

Registered: 02/19/05
Posts: 9
I noticed several similiar sub designs and manufacturers (SVS, HSU) utilize port plugging to drop the extension. Has that ever been a possibility for the LFM-1?

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#35103 - 03/27/05 02:21 AM Re: Max Extension via Port Plugging
soundhound Offline
Desperado

Registered: 04/10/02
Posts: 1857
Loc: Gusev Crater, Mars
It is my understanding (although I'm not completely sure) that the lowest frequencies are band limited in the power amplifier so any extension from re-tuning the cabinet would make no difference.

In any event, if you do this you will loose efficiency at the expense of the added extension.

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#35104 - 03/27/05 04:58 AM Re: Max Extension via Port Plugging
gonk Offline
Desperado

Registered: 03/21/01
Posts: 14054
Loc: Memphis, TN USA
I've never seen anything about what effect plugging a port on the LFM-1 might have on the extension, but Outlaw support might be able to shed some light on the subject.
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#35105 - 03/27/05 07:12 AM Re: Max Extension via Port Plugging
Spiker Offline
Gunslinger

Registered: 05/29/03
Posts: 297
Loc: Middle Earth
If one port is blocked it will increase the port noise since one trying to do the venting job of two (increased velosity). Whether it will be audible or not, Iím not sure.

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#35106 - 03/27/05 08:43 AM Re: Max Extension via Port Plugging
LaserMark4 Offline
Deputy Gunslinger

Registered: 02/19/05
Posts: 9
Maybe Outlaw Support could give us some insight??

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#35107 - 03/27/05 11:57 AM Re: Max Extension via Port Plugging
painttoad Offline
Desperado

Registered: 10/25/04
Posts: 688
Loc: peoria il
shove a "nerf" ball in each port,because that is basically what the plugs are.i'll almost bet you won't like the sound,MOST ported boxes,i'm sure there are exceptions,are tuned with # of,length and diameter of ports for maximum output.(along with the box volume (minus the port,driver and bracing displacement))xmax(1 way excursion) comes into play also,along with a bunch of numbers that are useless to most,unless designing a box to a particular driver

i've been(on a hobby level) designing and building sub boxes for a few years now(with outstanding results,i might add)

as soundhound stated,you will lose efficiency,and i don't see plugging ports as a way to get extension,as my ported boxes have all had higher output and lower end tuning than my sealed boxes.but as i said,i'm sure there are exceptions.

b & w supplies "port plugs" to REDUCE the bass extension and ouput to several of their speakers,so you may be reading the whole thing wrong,"dropping the extension" i thing should read;reducing the extension.but this is just my interpretation of things and i could be wrong...

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#35108 - 03/27/05 12:21 PM Re: Max Extension via Port Plugging
sraber Offline
Gunslinger

Registered: 10/11/04
Posts: 183
Loc: Green Bay, WI
In the case of the VTF series subs from HSU, you have the option of plugging one of the two ports. To get the max output (highest SPL) out of the sub, you remove the plug from one of the ports and flip a switch on the amp. (not sure what the switch does). to get the deepest bass, you plug one of the ports and flip the switch to "max extension" mode. the trade offs are in max output mode, the sub doesn't goes to 25hz, but it plays louder. In max extension you lose about 4 db according to the manual, but the sub plays down to 20hz.


later,
simp
_________________________
Marantz av7005 Proc.
Oppo BDP-83
Rotel RB-991 (mains)
Outlaw Audio Model 2200 (center)
Rotel RMB-1075 (ss, rs)
f, B&W DM604S3
c, B&W LCR600S3
ss, B&W DM302
rs,Polk M3II
HSU VTF-3 MK3
APC H-15 Power Conditioner
Display: Panny PT-AE4000 Proj. + 92" DIY Screen
Little Dot MKIII Headphone Amp
Denon AH-D1100 Headphones (needed a quick, cheap set. looking for an upgrade worthy of the h/p amp.)

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#35109 - 03/27/05 01:00 PM Re: Max Extension via Port Plugging
painttoad Offline
Desperado

Registered: 10/25/04
Posts: 688
Loc: peoria il
are the ports different lengths?that could maybe explain some tuning issues,that switch sounds intriguing,but there are 3 ports on these?i'll check back later,time for my "festivities",happy easter all

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#35110 - 03/27/05 03:50 PM Re: Max Extension via Port Plugging
sraber Offline
Gunslinger

Registered: 10/11/04
Posts: 183
Loc: Green Bay, WI
Nope, only two ports. From what I can tell, both ports are the same length and diameter. Not sure about that switch...

later,
simp
_________________________
Marantz av7005 Proc.
Oppo BDP-83
Rotel RB-991 (mains)
Outlaw Audio Model 2200 (center)
Rotel RMB-1075 (ss, rs)
f, B&W DM604S3
c, B&W LCR600S3
ss, B&W DM302
rs,Polk M3II
HSU VTF-3 MK3
APC H-15 Power Conditioner
Display: Panny PT-AE4000 Proj. + 92" DIY Screen
Little Dot MKIII Headphone Amp
Denon AH-D1100 Headphones (needed a quick, cheap set. looking for an upgrade worthy of the h/p amp.)

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#35111 - 03/27/05 04:38 PM Re: Max Extension via Port Plugging
painttoad Offline
Desperado

Registered: 10/25/04
Posts: 688
Loc: peoria il
ok,cookout is over,hope everybody had a good easter.sraber,i was thinkin' 'bout pics of the svs sub that had 3 ports,and the 'plug n tune',not really sure about how they design these things(technology,huh?)but then again,i've peered into many subs over the years,car and home(most of my knowledge stems from cars,but,same difference) and many 'higher end ' speakers,and not seen an ounce of absorbtion material,but...have seen PARTICLE BOARD as a rear panel in 'monitor' cabinets,which i understand absorbs some resonance and the damping is not necessary,go figure!figure out some kind of rules and they change everything!

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