[ctviggen]

I think you're right -- most sound cards cut off at about 20Hz.  My ETF program does not go below 20Hz.  What you can do with ETF though is put out a tone.  I'll see if ETF will let me try to put out a tone less than 20Hz, although I do not think that it will let me do this.  If that doesn't work, I'll create a CD with lower tones.  However, I'll have to review the material for my NHT crossover.  I think it begins to cutoff at 20Hz also.  So, even if I play 10Hz tones on a CD, I won't know how much will get cutoff, although perhaps I could estimate an unfiltered result using the cutoff slope of the crossover.  

At the listening position, the RM40s drop off according to ETF at about 40Hz.  I'll know more when I do some more testing.

[ScottMayo]

I think you're right -- most sound cards cut off at about 20Hz.  My ETF program does not go below 20Hz.

I use http://www.nch.com.au/tonegen/ . It's not free, but it generates low frequencies and combinations of frequencies. With a USB (external) SB Audigy "card"  as the source, I'm able to generate pretty much as low as I've ever dared go (5Hz) and see the speaker cone moving. Of course I don't know how many db down it gets below 20Hz, but it gets there at least.

[ctviggen]

Cool!  It's reasonable, too.

[John Casler]

If you want to make someone... vaguely uncomfortable, a 2hz "tone" can be helpful. If you want to mess with their intestines, a prolonged 8Hz tone at high SPL can do the trick. And people have reported experiencing distortions in vision when exposted to high SPL of 18-19Hz. (People considering buying "bass shakers", take note.)
...

I'm not sure you even need to go, that low to to cause a little nausea, since I have noticed it several times, when I have shut down my "mains" amp and just left the LARGERs on, for various things like placement, phasing, etc.

Any period of time doing this and you begin to feel like you just got off a ride at Magic Mountain.

I know B, was working with a Goverment Agency at one time with something "not related" to audio and though the project was/is Top Secret, I can say that they were having trouble with people getting sick from the low frequencies.

No it wasn't at GITMO  but that could be a good idea

[John Casler]

 The "-3dB @ 17hz" spec may be reproducible at 1m on the floor, or with the mic shoved up the slot. At the listening position (where it counts) don't expect much output below 30hz. And stacking two, four, or more won't affect this very much -- it is a function of the passive radiator design with 24dB/octave drop off below the resonant frequency. Stacking will obviously increase maximum SPL at any given frequency by 3dB which can definitely be a good thing, and it also helps load the room more evenly.

...

Just did a Q&D (quick and dirty) measurment on the lowest "tones" I have, and "in the listening position" I measured an "RS corrected" 81.5db at 20Hz and 84db @ 25Hz, so in my rig, we're getting substantially below 30Hz.

This is using a gain setting with Pink Noise (-20db) at 83db, which represents a normal listening level.

No stacking here, but the RM30s are full range and the QUAD LARGERs are running vertically, and in PUSH/PULL "sans" base plate so PR is firing into space.

Also of interest, is that the 10" woofer of the RM30s and the PR of the front LARGERs are both firing inward.

These readings represent a "HUGE" increase over the downfiring LARGERs in horizontal position and the 626Rs.  If I remember correctly the 20Hz measurment then was 68.5 db.

A 12.5db increase @ 20Hz!!

No wonder it was "instantly" noticable  

[rosconey]

i'm getting very very nice results so far with my cabinet design

[ekovalsky]

John,

If your measurements are accurate that is an amazing improvement.  Down 15dB or more at 20hz is what I'd expect from the Largers.  How ironic that totally defeating the proprietary VMPS "slot loaded" technology greatly improves the performance of the subs  

Sounds like the Larger is in serious need of a redesign to have the extension a huge subwoofer box with 15" and 12" drivers should have.  And perhaps you (and rosconey) stumbled upon a good solution.

It would be interesting to compare your Larger setup to some other reasonably priced dedicated bass systems, like the Citrine from Selah and the monsters that RAW is building for GR.  Based on QC and cabinetry I know which I'd buy, but the VMPS will be the cheapest.  And the conversions you've made can be done for free.

Brian should take advantage of your creativity and improve his product line by incorporating some of your tweaks and mods.

[John Casler]

John,

If your measurements are accurate that is an amazing improvement.  Down 15dB or more at 20hz is what I'd expect from the Largers.  How ironic that totally defeating the proprietary VMPS "slot loaded" technology greatly improves the performance of the subs  

Sounds like the Larger is in serious need of a redesign to have the extension a huge subwoofer box with 15" and 12" drivers should have.  And perhaps you (and rosconey) stumbled upon a good solution.

It would be interesting to compa ...

Hi Eric,

Well I would love to take credit for some kind of break through, but I'm not sure about the fact that it would "over-ride" the Slot loading technology "if" it were a single or dual sub set up without my "push/pull" configuration.

I have to say that it is a very "non-conventional" set up:

1) System is set up on the "long wall" (approx 30 x 20 x 9)
2) Front subs are at least 5 feet off the front wall so they "are not" corner or even wall loaded, Additionally they are over 9-20 feet from any side wall, so we are getting no room gain from the front subs
3) Rear subs are located on the rear wall and run "anti-phase"
4) All subs are run, vertically, and to do this the right has the 15" on the bottom and the left has the 12" on the bottom
5) I have "no bass traps" and did not open the windows or door to my patio, which I would expect to provide an even better response
6) Front LARGER's PR's fire inward at each other. actives fire at the sweet seat, converged to somewhat align acoustic centers with the RM30's.
7) Rear Largers fire directly forward and loosley aligned with the fronts.
8.) Rm30's 10" woofers also fire inward at each other
9) RM30's have SR-71 upgrade which might have deepened their bass response, but I haven't run any tests
10) The incredible thing is that this "depth" is realized at the "sweet seat", which is generally very hard to get.

In any event, the PR's firing on a different "path" in my room seems to work quite well.

It may be a "lucky fluke" or maybe I am on to something, in any event, no "re-design" is needed since I accomplished this simply by re-orienting from horizontal to vertical.   So if some find this works in their room, it can be done easily.

It certainly is a pleasnt surprise even though I need many more hours of listening  to make sure that "clarity and detail" are not negatively impacted.

See the problem is, the bass now goes so deep that I am concerned about my upstairs neighbors, getting a larger dose   So I restrict my listening to late morning and early afternnoon as to not wake their little 2 yr old.

If you didn't see my post about the American Beauty (Original Score not soundtrack) you need this CD, if you want to hear some good deep bass with your new Bass Towers.

[warnerwh]

Eric: With my last speakers, Vmps Supertower/R SE's, I was only down 3db at 20hz and flat at 25, this relative to 1000hz. They used the same bass drivers as the larger subs. A friend now has them and is in awe of the bass power in movies.

[rblnr]

How ironic that totally defeating the proprietary VMPS "slot loaded" technology greatly improves the performance of the subs

Does BC have any thoughts on this and the thread in general?

[ctviggen]

Interesting.  I measured (using ETF and a Behringer microphone) 72 dB at 20Hz with a single Larger (I have two, but currently can only measure either right or left using ETF) at the listening position, with slot loading on the Largers.  However, I have a major dip right after that to 60.7 dB at 22 Hz, then it shoots upwards to 82db at 30Hz.  What's interesting, though, is that the measurement with only my single RM40 is actually higher by 6 dB at 20Hz.  I may have to retest.  

The passive radiator has a 24 dB/octave drop off after the tuned frequency?  That's a large drop off.  I find that a bit hard to believe.  For instance, using ETF, I find a single RM40 alone (no sub) produces 85dB at the listening position at 50 Hz and is still producing 77 dB at 25 Hz.  That's nowhere close to 24 dB of loss.  I'll post some ETF measurements when I get back my stuff (mic and cables) from a friend.

[ScottMayo]

Interesting.  I measured (using ETF and a Behringer microphone) 72 dB at 20Hz with a single Larger (I have two, but currently can only measure either right or left using ETF) at the listening position, with slot loading on the Largers.  However, I have a major dip right after that to 60.7 dB at 22 Hz, then it shoots upwards to 82db at 30Hz.

It's more or less impossible to measure a speaker this way. A room plays such a big part in the response, and inches can matter. An anechoic chamber is about the only way to really measure (or being out in a quiet forest, I suppose, but that's about as hard to arrange. I wonder what the neighbors would say if I dragged a subwoofer into the woods at 3am. Hm.)

This is why I don't fret too much about a speaker's frequency response, except to make sure a setup can go low enough to handle movies. It's nice to know what the speaker will do, and I like to see graphs published - you can figure out in advance what you might need to correct for - but you're going to end up correcting no matter what.

[John Casler]

How ironic that totally defeating the proprietary VMPS "slot loaded" technology greatly improves the performance of the subs

Does BC have any thoughts on this and the thread in general?

Rblnr,

B, is on vaction this week and will be back next week, so he is not weighing in.

Eric,

There is no irony here at all.  Bass is a "very" room dependant quality, and for most purposes, the unique "slot loading" which Brian has developed produces great bass capabilities.

If my memory serves me right Zybar claimed 115db @ 20Hz at one time.

I found that in my room with the "push pull" that I gained quite a bit from an alternative orientation.

I think the take home message to my post is that the VMPS LARGER is a more "versatile" sub, in that there are several ways it can be used to good advantage, depending on your room.

I also did a couple test tones with my new RM30's yesterday, and "they" even produce a nice healthy 25Hz and 20Hz tones.

[zybar]

If my memory serves me right Zybar claimed 115db @ 20Hz at one time.

My claims at the time were with the RS meter and simple test tones.

I couldn't achieve anywhere near this with the much more accurate TacT + microphone measurements.

In fact, my measurements were as Eric described earlier.  I was seeing very quick and substantial dropoff starting around 40Hz in my room.  At 40Hz I was plus 10db's (almost corner loaded) and at 27db's I was -7db's.

I had almost exactly the same results with the RM 40's.

I do NOT get these results with the HT3's in the same room.

What the measurements did prove to me is that MOST of the bass that really impressed people is well above 30Hz.  

The measurements didn't take away from my enjoyment of the subs or the positive impressions that they made upon myself or guests at the time.

Dual Larger subs, still made pant legs flap and helped build a very nice HT experience.

George

[James Romeyn]

John
The side panel siting of the PR was recommended to me by Art Noxon, PhD in Physics (or acoustic engineering, I forgot), owner of ASC Tube Traps.  A great, wonderful, generous guy, very friendly.  

When I made my own speakers I found this PR siting worked just as you describe.  I passed along Art's suggestion to Brian & we know Brian's response.

It was so long ago (over a decade) I don't remember the reasoning, but Art had good, solid, scientific, mathematical justifications.  Brian likes the slot because it filters hi freq garbage.  I think the audio results that you & me noticed in this case are consistent with ASC's recommendation.  The funny thing is that Brian would decrease weight, increase cabinet volume significantly & apparently save money on materials & labor.  What's wrong with that?  The PR grill could mimic the RM30s side-firing 10MW grill.  Insist that Brian try it, & soon.