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post #91 of 1093 Old 04-04-2011, 12:28 AM
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Looking Nice! ... I learned to _hate_ insulation after doing something like 1500sqft of 2" in my room. Nasty stuff, only took two hours before I was heading to the store to get a mask... I now have a hoodie that's designated as my "fiberglass shield".


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post #92 of 1093 Old 04-04-2011, 09:14 PM - Thread Starter
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Didn't get much time to work tonight, but did manage to get the drivers installed.





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post #93 of 1093 Old 04-04-2011, 09:15 PM - Thread Starter
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Everything is still a bit dusty.





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post #94 of 1093 Old 04-04-2011, 09:26 PM
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What amp(s) are you using to drive the subs?


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post #95 of 1093 Old 04-04-2011, 09:52 PM - Thread Starter
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Quote:
Originally Posted by distoga View Post

What amp(s) are you using to drive the subs?

I have a Behringer EP-4000 Pro Amp. I used this with my prior subs. Should be plenty for all 4 subs - I'll run 2 subs off each channel at 4 ohms. The manufacturer claims 1400 watts per channel into 4 ohms but I've heard it measures more like 1000. Still 500 watts per driver should be plenty.

http://www.behringer.com/EN/Products/EP4000.aspx


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post #96 of 1093 Old 04-04-2011, 10:04 PM - Thread Starter
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Quote:
Originally Posted by distoga View Post

What amp(s) are you using to drive the subs?

By the way I also have the Behringer Feedback Destroyer pro dsp1124 but was thinking of getting the 2496 like you have. When I had my subs set up before I never did do any EQ with the dsp1124. I played around with REW and could not get proper readings.

When I get everything up and running I may have to have you coach me on the finer points of REW. I have everything I need - M-Audio Mobile Pre, Behringer ECM8000 etc, but never really got meaningful measurements. I didn't have a lot of time to spend on it as we had put our house up for sale about the same time the theater was finished.


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post #97 of 1093 Old 04-05-2011, 09:38 AM
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The EP4000 puts out a measured 635@4ohms.

Here's the actual numbers;

8 ohm stereo = 450w
4 ohm stereo = 635w
2 ohm stereo = 815w

------------------------

8 ohm mono = 1336w
4 ohm mono = 2000w


Also, wrt measurement and EQ, you'll get all the support you need here @AVS, or @The Cult.

Once again, nice build.

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post #98 of 1093 Old 04-05-2011, 10:57 AM - Thread Starter
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Those ratings are a bit lower than I thought - Just a little over 300w per driver - should be fine though.

I think I calculated it as 500w per driver if I do a 4ohm mono load, which I cant do with 4 2ohm coils, unless I am not calculating something correctly. At any rate I'll see how it goes with the EP4000 - it seems to be a popular option for running 4 fi ib18's. If I need more I may look into one of the newer i series amps.


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post #99 of 1093 Old 04-05-2011, 12:59 PM
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You'll be fine at 300 watts/driver. As you likely know, one of the inherent advantages of a properly optimized IB alignment, is it's native extension. Since it's not fighting a small sealed box, it's very efficient down into the infra-sound octaves, and it doesn't need a great deal of power to adequately reproduce the bottom octaves.

Actually, an approach of using 300 watts per driver is a very good idea in this application. Overkill belongs on the driver side of the driver/amplifier equation. You'll run out of amplifier, prior to reaching the driver limits. I've experimented with the EP4000, powering the IB3-18s, they will hard bottom, in a very nasty clank I've been told. I've eased them very carefully near their limits with a 20hz. tone, to a point whereby the subtle ticking begins. From input from other owners, I'm told this ticking, or tapping is the precursor to the potentially damaging hard bottom.

The Fi IB3-18s are rated to handle 550w@20hz. So knowing many contemporary soundtracks contain material easily two octaves lower than 20hz., by spreading ~600 watts across two drivers creates an operational buffer of protection from high energy effects in the bottom octaves. Additionally, you want to stay away from Xmax, as driver non-linearities increase significantly at the excursion extremes. The end product in this scenario is that seeing a red flicker of the clip light, and reacting accordingly, is highly preferable to discovering you're near the drivers limits by a sudden hard bottoming of the drivers.


Besides, at ~300w/driver, you'll be within 3db of maximum displacement for the entire set of 4, 30mm Xmax 18" drivers. Depending on your room dimensions, contents, and the boundary walls diaphragmatic solidity, your room may exhibit quite positive PVG characteristics. One of the very few areas in audio whereby there is such a thing as free lunch. And unlike horn approaches to sub-woofing, this free lunch doesn't amplify distortion products


Good luck

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post #100 of 1093 Old 04-05-2011, 01:57 PM - Thread Starter
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Quote:
Originally Posted by FOH View Post


Besides, at ~300w/driver, you'll be within 3db of maximum displacement for the entire set of 4, 30mm Xmax 18" drivers. Depending on your room dimensions, contents, and the boundary walls diaphragmatic solidity, your room may exhibit quite positive PVG characteristics. One of the very few areas in audio whereby there is such a thing as free lunch. And unlike horn approaches to sub-woofing, this free lunch doesn't amplify distortion products

Good luck

Thanks for the info - I'm interested in the PVG characteristics you are talking about - Never heard of that. Is there anywhere to read more abou this - if nothing it will make me feel better about all the work that is going to go into the room with double drywall and OSB.


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post #101 of 1093 Old 04-06-2011, 10:23 AM
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Quote:
Originally Posted by stockmonkey2000 View Post


I'm interested in the PVG characteristics you are talking about - Never heard of that.

There exists room gain, and boundary gain.

First, Boundary Gain comes from the driver operating in a constrained space. One begins with a theoretical full-space. This has no surfaces which interact with the acoustic output of the driver. Only a full tilt, entirely anechoic chamber can approximate a theoretical full space. That said, cutting a full space sphere in half with a ground plane, one creates half space. This is an outdoor environment, whereby zero acoustic interaction occurs between the driver, and the hemisphere above the ground. The ground merely halves the previous full space. This halving, theoretically mirrors another like powered driver, thereby resulting in a theoretical 6db gain. Each subsequent halving of space, with the addition of another boundary, also results in a theoretical 6db gain.

So boundary gain is essentially added acoustic support, by halving the existing acoustic quantity. After one accepts the benefits of the ground boundary, wall and corner loading is considered. The maximum additional SPL for each boundary is 6db each. So with a sub in the middle of the room, the floor adds 6db. Moving it to a mid-wall position would add an additional 6 db, totaling 12db. Full corner loading would yield 18db. However, one must subtract whatever movement is incurred by the boundary surfaces not being entirely inert. Any movement results in losses. A full reinforced concrete wall basement structure would typically yield the full 18db for corner loading. One must be mindful that boundary gain is limited to fully supporting 1/8 the wavelength. A sub-woofer crossed over at 80hz, with the 80hz wavelength being about 14 feet, the driver's acoustic center needs to be within 20 inches of the boundary to retain the entire benefit of the effect.

Now Pressure Vessel Gain (PVG), or room gain, is the scenario whereby the longest dimension of the room can no longer support full propagation of the waveform. At this point, the acoustic propagation transitions to acoustic pressurization. A typical myth is a small cabin cannot support the lowest frequencies.... nothing could be further from the truth. The manner in which the sound is reproduced into the space changes from a normal cyclic propagation, to pressurization because the wavelengths are too big for the space. The frequency at which this occurs is approximately the point whereby half the wavelength of a given frequency is equal to the rooms longest dimension. So, a 20 hz frequency has a wavelength 56.5 feet. So half of that, 28.25 feet, is the point of transition. Any frequency below that point pressurizes the room, and any frequency above that point propagates freely. So in this room that's approximately 28 feet in the longest dimension, from 20 hz downward, the room gives back acoustically. This is room gain, cabin gain, or PVG...Pressure Vessel Gain.

At this frequency, the results are a gain in acoustic pressures in the room that grows as the frequency decreases. This acoustic support reciprocity, is theoretically 12db per octave. The percentage of the 12 db/octave gain one achieves, entirely depends on the integrity of the boundary walls and surfaces. If it was the theoretical concrete bunker, a full 12db/octave boost would occur. Typically, somewhere between 6-10 db octave could result. Also, in addition to the walls and surfaces flexing, other aspects may affect the point at which room gain begins. Furniture, cabinets etc, anything that consumes a certain measure of cubic feet, may slightly alter the transition frequency merely because the items take up space.

This acoustic pressurization, room gain, is the proverbial free lunch. It is essentially headroom that's thrown back into the system. And unlike horn subs, the distortions and non-linearities are not magnified. An IB sub system is a sealed alignment. Sealed alignments roll off second order. Room gain also is second order. So one can see how integrating a sealed alignment may offer substantial benefit when attempting to integrate the system to the room via time and frequency equalization. The -3db point of the IB, may typically be deeper than the transition point where room gain begins. Properly adjusted, this would result in substantial headroom added back in for significant capability for the big LFE effects.



Good luck

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post #102 of 1093 Old 04-06-2011, 11:05 AM - Thread Starter
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Thanks for taking the time to put together such a detailed response. I know about room gain and such but your explanation helped me understand much better. It does make me feel a bit better about spending all the extra effort making such rigid walls.

I'm looking forward to some of that Pressure Vessel Gain


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post #103 of 1093 Old 04-06-2011, 12:49 PM
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I'm glad I can help. What is your room's longest dimension?

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post #104 of 1093 Old 04-06-2011, 12:54 PM - Thread Starter
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My rooms longest dimension will end up being a 26'2". Width will be 14'8 and height should end up around 8'5 or so. This is interior dimensions after double drywall etc.


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post #105 of 1093 Old 04-08-2011, 08:40 AM - Thread Starter
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I've run into a few complications with the room within a room approach and am considering doing Clips and channel for the ceiling. I have some issues with pipes on the side walls that may prevent me from building walls that can support the ceiling. I think these issues can be overcome but clips and channel might be easier.

I noticed on the soundproofing company site it mentions placing the clips 48 inches apart to allow the panels to flex. If I do as triple sandwich with OSB, GG DW GG DW is this going to defeat some of the flex that I need? I would really like to have the OSB to allow easier connection of the star ceiling later.

I'm also curious what the performance of a clipped ceiling would be vs a staggered joist ceiling. I'm trying to figure out the pain vs performance factor and whether it is worth it to re-route some things to allow the staggered joists.


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post #106 of 1093 Old 04-11-2011, 05:51 PM - Thread Starter
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Got home today and had a new toy waiting.



This is my new center channel speaker. It is a custom made center channel that matches my main speakers. Wish I had the theater ready so i could get it set up. It is a lot bigger than I envisioned even knowing the measurements. Not sure what it weighs but the shipping weight was 170 lbs.





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post #107 of 1093 Old 04-11-2011, 07:54 PM
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Nice speaker.... Have you set any sort of 'want to finish by' date?


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post #108 of 1093 Old 04-11-2011, 08:54 PM - Thread Starter
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Quote:
Originally Posted by distoga View Post

Nice speaker.... Have you set any sort of 'want to finish by' date?

I'm expecting it to take me at least a year - so about this time 2012. That may be overly optimistic based on what I've seen out of others here. I'm doing everything by myself so it just takes time.


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post #109 of 1093 Old 04-11-2011, 09:12 PM - Thread Starter
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Originally Posted by DavidK442 View Post

Scanned your thread again and didn't catch the details of your main speakers. What are the measurements on the center? Just curious, with so many speaker options out there why go custom? Better value or specialy tweaked for you installation?

My main speakers are PBN Audio Montana EPS speakers. Ever since finding the PBN's I have had no desire to upgrade. They are amazing sounding speakers. I've been using a Tyler Acoustics Taylo Reference Center because it uses the same Scan speak Revelator tweeter found in the EPS, but I always wanted a PBN center.

While the center channel is custom, the drivers and crossover are identical to the Production model of my Main EPS speakers. PBN audio had an EPS center that was custom made for a client that later upgraded to an even larger model. It was a used speaker but peter at PBN put in all new drivers and even refinished the cabinet - even though I did not ask for that. He also gave me an incredible deal.

PBN's are quite expensive, but I have not heard anything even remotely close in price that touches the PBN's. I 've went through a lot of speakers over the years but have had the PBN's for several years. I also use PBN monitors for my rear surrounds and am going to have PBN make some custom inwall's for the side surrounds.

PBN also really stands behind their products. Even though they have a 5 year warranty - Peter has fixed things for me out of warranty for no charge.

The size of the center channel is 16 tall x 14 deep by 36 wide.


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post #110 of 1093 Old 04-12-2011, 07:14 AM
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Very nice center channel. PBN's build quality is is as good as anyone's. Their cabinets are robust and entirely inert. I'm not sure I've ever heard anything bad about their work. As a rule, I'd not use a single dome tweeter for HT use, as their sensitivity and ultimate output level would be in question. But PBN's are typically more sensitive, and higher output that most similar designs. Actually, their work is at the very top of what can be achieved with cone/dome designs. They're not inexpensive either, but you get what you pay for. PBN makes superb loudspeakers.

Have fun

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post #111 of 1093 Old 04-12-2011, 07:37 AM - Thread Starter
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Originally Posted by FOH View Post

Very nice center channel. PBN's build quality is is as good as anyone's. Their cabinets are robust and entirely inert. I'm not sure I've ever heard anything bad about their work. As a rule, I'd not use a single dome tweeter for HT use, as their sensitivity and ultimate output level would be in question. But PBN's are typically more sensitive, and higher output that most similar designs. Actually, their work is at the very top of what can be achieved with cone/dome designs. They're not inexpensive either, but you get what you pay for. PBN makes superb loudspeakers.

Have fun

There may be some better suited options strictly for Home Theater use, but music performance is more important to me than the Home theater performance. The PBN's do have 92-93db sensitivity and the Revelator Tweeter that they use is capable of very high power handling and output. I used the PBN's in my previous theater and never felt like they were being pushed to their limit. The PBN's will not be able to keep up with the IB sub in terms of sheer output, but I don't really need to listen at 120+db's. The sub is there for headroom.


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post #112 of 1093 Old 04-12-2011, 08:04 AM
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Just read the Stereophile review of the EPS's. They sound awesome, but I can't believe they gave it a Poor rating on the portability. They're only 154 lbs a piece...

-




Is it solipsistic in here, or is it just me?
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post #113 of 1093 Old 04-12-2011, 08:29 AM - Thread Starter
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Just read the Stereophile review of the EPS's. They sound awesome, but I can't believe they gave it a Poor rating on the portability. They're only 154 lbs a piece...

I think mine check in at 175 lbs a peice - Not sure why mine weigh more but they did have an upgraded crossover (the signature version) I cant imagine that would account for nearly 20 lbs though. The newer EPS2 is a bit lighter. Stereophile gave the EPS a class A rating in stereophile - I think it was class A (restricted LF). The EPS does have good response down to 25 hz or so but a full class A speaker in Stereophile requires 20 Hz extension.


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post #114 of 1093 Old 04-12-2011, 11:42 AM
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Quote:
Originally Posted by stockmonkey2000 View Post

.........

The PBN's will not be able to keep up with the IB sub in terms of sheer output, but I don't really need to listen at 120+db's. The sub is there for headroom.

I oftentimes see this statement made, ... and it isn't necessarily true in absolute terms. The equal loudness curves dictate that the threshold of hearing for very low frequencies, would place a 6hz lightning strike,...with any kind of impact, easily in the area of 120db.

Likewise, 120db of 60hz hum, would drive you out of the room. The LFE levels are relative.



Thanks

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------------------------------------
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(3)Seaton Cat12C up front, (4)QSC K8 sides/rears
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post #115 of 1093 Old 04-12-2011, 12:40 PM - Thread Starter
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Quote:
Originally Posted by FOH View Post

I oftentimes see this statement made, ... and it isn't necessarily true in absolute terms. The equal loudness curves dictate that the threshold of hearing for very low frequencies, would place a 6hz lightning strike,...with any kind of impact, easily in the area of 120db.

Likewise, 120db of 60hz hum, would drive you out of the room. The LFE levels are relative.



Thanks

To have headroom at 6hz I would probably need 32 18" drivers or a couple of rotary woofers. As a side note - I once had lightning strike about 20 feet away from me. My ears were ringing for days afterward. I could feel the hairs on my arms stand up right before it struck. I really do not want to try and recreate that in my theater


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post #116 of 1093 Old 04-12-2011, 01:37 PM
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I'm expecting it to take me at least a year - so about this time 2012. ...

That should give you just enough time before the world ends!

Every man dies. Not every man really lives.
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post #117 of 1093 Old 04-12-2011, 02:25 PM - Thread Starter
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That should give you just enough time before the world ends!

I'm really hoping the mayans were wrong on that one. We put our last home up for sale just about the time the theater was finished.


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post #118 of 1093 Old 04-12-2011, 07:31 PM - Thread Starter
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I insulated and put up OSB on the baffle wall.





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post #119 of 1093 Old 04-13-2011, 01:15 PM
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Originally Posted by stockmonkey2000 View Post

To have headroom at 6hz I would probably need 32 18" drivers or a couple of rotary woofers. As a side note - I once had lightning strike about 20 feet away from me. My ears were ringing for days afterward. I could feel the hairs on my arms stand up right before it struck. I really do not want to try and recreate that in my theater

You may not be aware just how powerful your IB will be. A system such as yours will have so much native extension, that the signal path electronics will likely be the ultimate limiting factor. The spec for LFE production is 3-120hz. If one's system is not covering that bandwidth, there will be material missing that the sound engineering team intended you to experience. There are those that believe that the infra sound octaves below 20hz have no importance, typically, they're not owners of high resolution LFE systems. The sounds we encounter in our lives contain frequencies down to 3hz, and lower. Percussive wavefronts that accompany a variety of sounds frequently have elements this low. A well recorded soundtrack can have elements easily down to 3hz. The sound designers carefully craft the infra sound octaves, just as they do the audible octaves; to achieve the desired effect of realism.

One of many examples of this is Open Range. The special effects recording and soundtrack are outstanding in the release. Here you can see the bulk of the spectral content lies in the octave between 30-60hz. However there is significant energy in the area below 5hz, placed there for systems that can reproduce it for added realism. That extra wallop down low creates a very realistic leading edge transient,....that accompanies the fundamental frequencies.



Open Range;






Another example is the famous lightning strikes in War of the Worlds. Spielberg, and his team, wanted to create a sense of impending doom....they succeeded. The resulting soundtrack is something of legend, a good test for a sub system;




At 1m, without factoring in the benefits of room gain, you'll easily have 130db@20hz and above,... and this is with a drive level of 225w/per driver, and a 50% lossy corner load. This is conservative and achievable. Your longest dimension is 26 feet, so room gain onset will occur at approximately 23hz. So you'll enjoy about 18db of gain at 6hz. So calculating this, and including a very reasonable room gain quantity, you could achieve 128 db@12hz@4 drivers@225w/per driver@1m.

Room gain, theoretically is identical to a sealed system roll off. Whatever your sub rolls off, the room gives back. In practice, the numbers vary somewhat, but you'll have significant capability I wouldn't be suprised if you could achieve flat to 5hz.

So as you see, you'll not need (32)18's to achieve this, you already there. As long as your electronics possess good extension toward DC, you'll have strong performance in the lowest octaves. Also, the equal loudness curves dictate that in order to hear 10Hz you need sound pressure levels above 100dB. To hear 5Hz you need sound levels above 110dB. So 120db at 5hz is merely 10db above audibility.





Quote:


As a side note - I once had lightning strike about 20 feet away from me. My ears were ringing for days afterward. I could feel the hairs on my arms stand up right before it struck.

I can't imagine what that was like for you, but I too have had two close calls,..not fun.





So in summary,...if you don't want that type of realism, you can always filter it out with a high pass at 20hz



Good luck

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post #120 of 1093 Old 04-13-2011, 01:22 PM - Thread Starter
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In practice, the numbers vary somewhat, but you'll have significant capability I wouldn't be suprised if you could achieve flat to 5hz.

Good luck

Flat to 5hz will make me very happy.


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