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?

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.

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.

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, I’m not sure.

Maybe Outlaw Support could give us some insight??

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...

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

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

Nope, only two ports. From what I can tell, both ports are the same length and diameter. Not sure about that switch...

later,
simp

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!

i won't quit though,my next boxes are for jl 10w3d6 subs for my truck,they will be my first attempt for THE "harder to calculate 'rectangular' port",i'm not 'fraid,look forward to it!

wish 'wing' was closer so i could help!

Several of the SVS subs have 3 ports, and plugging 1-2 ports is a method of lowering the sub's extension. BUT, as 'sraber' pointed out, there's a switch or knob on both the HSU and SVS that needs to be switched along with the insertion of the port plugs, which I did not realize. So now it seems apparent that something is being changed internally with the amp/electronics, along with the port plugs in these other subs-- a feature (switch) which is not available on the LFM-1.

So the big question is will I miss the 15-24 Hz range some of these other subs deliver?? I love the idea of 2 solid stereo Outlaw subs under $1K with free shipping now (with a couple of purchased cables). But will I wish I had that "wow" factor below 25 Hz in the HT???

i'll try to get into this again after work

The switch undoubtedly lowers the frequency of the high pass filter which rolls off bass below the tuning frequency. Some EQ changes might also be made by throwing the switch. The high pass filter prevents the driver from trying to reproduce frequencies below the tuning frequency which might damage it because of excessive excursion.

Port plugging is what I have done with my JBL subs - they originally had 3 ports with a 25Hz tuning, and by plugging two of them, the tuning is around 12Hz. I lost efficiency which I made up for by using two subs per side instead of one.

I hate when that happens.

Soundhound--

You sound like you have some serious bass cranking! I would imagine you "experience" and hear a real difference between the 25Hz tuning and the 12Hz setup, yes?

It seems that more and more material being created out there is utilizing these lower freqs. Would that be your take too?

You might say that

soundhound:

how much power do you have for the subs?each one have it's own amp,i assume?

i don't remember seeing those plugs in older pics.this a recent thing?

by having 2 subs,they will compliment each other,and with interaction with the room,i'd guess you should be down in the teens.

my monitor sub had a switch(before i smoked the amp) for movies/music.monitor told me the movie setting gave a 3db increase over music mode,but could not elaborate on an eq change(i did ask)

They are in parallel on each side so the resulting impedance is 4 ohms. They are driven by a Soundcraft SA-1000 professional stereo 1000 watt amp that puts out 500 watts per side into 4 ohms. I do have another identical amp and for awhile drove each side by it's own amp, but I found that I didn't need the additional power. In spite of the port plugging, they are still quite efficient in the scheme of things because of the large cabinet size and 18" drivers.

The tuning has always been the same. The pictures I have posted before have been with the grilles in place.

The resulting response in-room is dead flat down to 10Hz, which is the lower limit of my RTA program (TureRTA).

for some reason,it seems like i remember big jbl subs being really efficient,10 hz has gotta be insane,i know how bad my eyeballs rattle in my truck,and my subs are cabable of 18hz but have never had it on an rta.i tuned my sealed boxes somewhere around 42 hz,but these things are going much lower,they do things my home(ported(2)) sub will not touch(rated at 22 or 25hz)!

if you can deal with metal and have no sensitive ears around the house try out DOPE:LIFE.tracks 1&6 have bass lines that would just have to be stupid loud on your system!don't stream it or use a burnt copy,the bass isn't there.trust me it would be worth the $15 just to have it 4 a demo.i used track 1 with 4 12's,in my truck,on the spl meter and hit over 150db!

My own "organ bass demo CD" that was circulated here and the Sound & Vision forum a couple years ago is still the most potent bass CD I've ever heard. It has extremely strong 16Hz notes held for seconds at a time from the 32 foot pipes.

wish i coulda got a copy of it when it was goin around,snooze ya loose i guess

Back to port plugging--

Here is a post I stumbled into today by Dr. HSU regarding their use of port plugging with the STF-3. That sub seems very close to the LFM-1.... has no electronics switching but only utilizing the plugging on one port. Here's his comments:

"Our company tries to respond quickly to customer needs. This issue of getting high output below 25 Hz is a good example. Previously, we felt that the majority of customers who buy the STF-3 do not need response below 25 Hz. Posts like yours make us reconsider that. We came out with a very simple and cost effective solution to make the STF-3 more appealing to consumers like yourself – plug up one port. The fact that our manual did not mention the option does not mean that one cannot do it or that it is not recommended. It is a different story if we said specifically in the manual that we do not recommend operating the subwoofer in that fashion.

The loss in output with 10% harmonic distortion when switching to one port is not as bad as you think. Thanks to the soft power supply of the BASH amp, with one port open, the impedance at 25 Hz is much higher than when both ports are open. With both ports open, the impedance at 25 Hz is very low. The maximum voltage swing the amplifier can deliver is much lower than when one port is open, where the low impedance is shifted down to around 18 Hz. The result is no loss of output at 25 Hz for 10% harmonic distortion. The woofer has a much higher excursion at that SPL compared to the two port open case (roughly 10 times higher), but harmonic distortion is still below 10% up to the same SPL. The only 1/3 octave spaced frequency measured that showed significant reduction in output with the 10% harmonic distortion criteria is 31.5 Hz where we measured a 2 dB reduction.

Regarding frequency response, using one port versus two ports and not adjusting the EQ is roughly equivalent to comparing a sealed box system with a system Q of 0.7 to one with a system Q of 0.5. The frequency response starts to roll off earlier. In this case, the roll off begins at around 40 Hz, being down about 2 dB by 25 Hz compared to both ports open. However, Edward’s expectation of the frequency response being down 7 dB at 20 Hz compared to the two ports open situation is erroneous. Edwards forgot that with both ports open, below 25 Hz, the output of the port gets out of phase with respect to the woofer output. This result in a 24 dB/Oct acoustic roll off below 25 Hz. This is absent in the one port open condition, down to the single port resonance of around 18 Hz. This means that the roll off rate between 25 and 18 Hz is far gentler with one port open. The result is the frequency response at 20 Hz is down less with one port open than with both ports open, even without changing the EQ.

Now, some customers do prefer an overdamped frequency response. Some feel that it gives a ‘tighter’ bass. Hence I would not dismiss this option entirely. In fact, I will make it official that customers who prefer an overdamped characteristic can set their VTF-3 or VTF-2 to two ports open EQ, and plug up one port. It posts no danger to the subwoofer (on the other hand, we do NOT recommend opening both ports and setting the EQ to one port open)."

So how about it.....I'm still curious if port plugging would be allowed with the LFM-1. I am considering a pair of them, and still wondering if this is feasible with the LFM-1 to gain a greater extension.

Anyone able to do a little testing/trial and error on their Outlaws?

Any Outlaw spokesman out there able to confirm or deny the rumor or possibility of plugging??