third ported subwoofer or two new sealed subs?

[mike c]

say somebody had two A7-450's ... tuned to 18hz

what would be a better buy:

another A7-450?
or
two A7S-450's EQ'ed to play 10-20hz only?

just a theoretical question to keep my mind busy.

 

[mazersteven]

Sounds like someone at the HomeTheaterShack is doing something that your questioning.

 

[mike c]

who?

the guy asking about the plate amps?

 

[Sheep]

The guy should stop buying subwoofers before he starts seeing red.

Oh, and 3 subwoofers is an acoustical no no.. so I think at answers your question.

SheepStar

 

[tomd51]

While I don't consider myself a bass addict but do love the bang and boom, I wouldn't necessarily consider dedicating two subs to 10-20Hz a good buy.

If you've been able to gather up up lots of subsonic/infrasonic material then maybe, but I'd say you'd get more mileage out of the third sub.

As far as whether they're ported or sealed affecting their performance, if the 19Ov.2 performs as well as the 13Ov.2 I've used to build a friend a DIY sub and eD is capable in their enclosure builds, you should get good performance regardless whether they're sealed or ported... -TD

 

[avaserfi]

Mike, I really don't see a reason to add more subs to your set up. From the graphs I have seen on the A7-450's you won't really need more output at any levels, but if you want a better response rather than getting another sub and having it run 10-20Hz I would suggest getting another pair of A7-450's for the other two corners in your room. This will increase your overall output by around 10-15dB, give you way more headroom and allow for decreased distortion as each sub will have to work less. Also, this will completely even your frequency response through the room (assuming proper placement and set up).

In your quest for the ultimate subwoofer setup I think you are going a little overboard. With the subs you just bought I would recommend cross-room placement with opposing phase and a parametric equalizer creating an extreme house curve. This should give you the thump you want.

 

[tomd51]

Oh, and 3 subwoofers is an acoustical no no.. so I think at answers your question.

SheepStar

While I agree to some extent, I think it is possible to integrate several subs at once. It certainly takes quite a bit of effort, but it can be done and prove beneficial if implemented properly... -TD

 

[mike c]

hey it's just theoretical. I can't afford any of that right now.

tomd51, thanks for sharing your experience with eD.

andrew, but with a tuning of 18hz, wouldn't anything below the tuning be full of distortion, that's why i'm planning to set a subsonic filter on the A7-450.

sheep, I make sure to move the other subwoofers to other setups anyway
maybe two more of the A7-450 is a good idea
and I currently AM using 3 subwoofers ... it's flat in both seating locations sans any EQ

 

[annunaki]

For response that low, it is inefficient to use dedicated subwoofers (from 10hz-20hz). Do remember that room gain will play an important role that low down in the spectrum.

What was that Adire Audio contraption they devised sometime back. It was like a sub woofer but had a 4' x 4' sheet of rigid honecomb material attached to it. It was good down to 5hz or even lower I believe. It would move something like 5" or so peak to peak.

As far as distortion goes, you are going to have to have it pretty high to even begin to remotely hear it that low in the frequency band. People do not hear much below 20hz. The ear just is not sensitive in that range. We can feel and sense the pressurizing effect at those frequencies which is what you would want to accomplish.

 

[mike c]

hey annunaki, somebody mentioned just plugging ports on the ported sub ... how do I know at what volume or spl will the ports start chuffing?

 

[annunaki]

You would have to get the T/S parameters on the sub and then get all of the enclosure specifics. You can then model the sub in said enclosure and check the port velocity. It will show what frequency they will start making noise at anor if there is a significant amount of port compression.

Large diameter (surface area) ports have lower resonant frequencies (port resonance) and typically will require steeper low pass crossovers to ensure that the port resonances are kept out of the operating range. Making a port too small introduces port compression and increased port velocity resulting in noise and chuffing.

 

[annunaki]

Any of the options you posted should easily produce usable in-room response to below 10hz. I assume the graphs are anechoic???

Two subs properly placed in any of those configurations will yield substantial infrasonic output. I do not think I have ever heard a system, home or car, that was capable of 107db at 10hz. That is simply amazing. You may feel sick at those output levels, literally. With two subs, it will be 3db higher to boot!!!!

 

[annunaki]

I am not sure how your room responds but many rooms tend to accentuate frequencies below 20hz. If you have eve a 6db bump in room gain below 20hz you will be in for a frightful experience. You are going to have to tie or nail everything down. 113db or potentially higher in room response at 10hz is quite amazing.

I all seriousness, I would make sure there are no health risks. The resonant frequency of the brain, from what I recall, is between 5hz-10hz depending upon the person. The right frequency at a high enough level could cause some rather weird effects. I am not entirely sure on this topic as I have not persued it much. It is something to look into though.

 

[tomd51]

You may feel sick at those output levels, literally.

So it's not just me? During extended calibration and testing, I've felt a bit nauseous a few times from what seems like over exposure to unusually loud, low frequencies.

Is this the kind of thing you're referring to annunaki? -TD

 

[mike c]

Any of the options you posted should easily produce usable in-room response to below 10hz. I assume the graphs are anechoic???

Two subs properly placed in any of those configurations will yield substantial infrasonic output. I do not think I have ever heard a system, home or car, that was capable of 107db at 10hz. That is simply amazing. You may feel sick at those output levels, literally. With two subs, it will be 3db higher to boot!!!!

those are models of something they call "power response" ... not models of FR or even a measurement of FR.

also, isn't room gain dependent on one of the room dimensions? i remember my 2600 cu room not having any room gain til the teens ... now my room is 4k cubic

 

[annunaki]

So it's not just me? During extended calibration and testing, I've felt a bit nauseous a few times from what seems like over exposure to unusually loud, low frequencies.

Is this the kind of thing you're referring to annunaki? -TD

Yes. Somewhat prolonged exposure to high output extreme low frequency information can cause these types of feelings.

Mythbusters did a piss poor attempt at this one. They did it outside with a bunch of large woofers but failed to mention if the woofers were even capable of output that low. It should be noted that people over 50 feet away admitted to feeling queasy and/or nauseous after some time. The length of such low frequency waves are over 50 ft. hmm??

They should have tested in a room where the length of the wave would not come into play.

 

[annunaki]

those are models of something they call "power response" ... not models of FR or even a measurement of FR.

also, isn't room gain dependent on one of the room dimensions? i remember my 2600 cu room not having any room gain til the teens ... now my room is 4k cubic

If the gain starts in the teens, that will help you out.

What is power response??? Did they explain it? Is it a curve they hope you get but are guessing? In other words it is useless

 

[mike c]

i think those are max outputs (in theory) when fed a high amount of power.

i'll have to find the room gain computer ... i'll wait til i get to work to waste time finding that and computing for my room gain