The last couple of months we've been working on getting a generator setup for my house going.

I currently rent where I live, and live in a city in a semi-neighbourhood.  I was hoping that the EU-2000i would be quiet enough that people would not be able to hear it from the streets  and from my neighbours house, at least in idle/econo mode.  The house is on 1 acre so there's a fair amount of distance on all sides before the property line; the closest distance from my  (open air/concrete slab with a roof over it) garage where I will have the generator(s) is about 50 feet.

As anyone with an EU-2000i knows, that was an unreasonable expectation, especially when there is no city noise (traffic etc.) to blot out the engine signature.  Late at night, I can hear  the econo-mode eu-2000i hundreds of feet away; I'd say 300 feet PLUS.
This was very disappointing to me; I don't think I need to explain why that kind of sound travelling distance is a Bad Thing(tm) to you guys reading the SURVIVAL forum ;).

In fact, if my goal is to have some basic power during a SHTF event, i've failed at it; I would not want to start my generator because it would effenticely put a fucking huge audio-based  target on my house.  I don't want to LOOK prepared, just BE prepared ;)

With this in mind, I started reading about quiet boxes for generators.  I've got to say, there isn't a whole lot out there regarding this particular goal; everything I found was  insufficient for my purposes.  Most of what I have found were people who bought loud ass POS chinese generators and were looking to make them as quiet as an EU-2000i, rather than someone  trying to make an EU-2000i quieter than it, admittedly, already is.

I've always been interested in audio, have been involved in building speaker boxes and have a good idea of how sound works. So, I decided to try my own design.

Requirements for my particular design:
1. Must bring the sound signature to the point that it cannot be heard > 40 feet away.
2. Must accomodate a pair of econo-mode eu-2000i  generators.  The above sound requirements should at the minimum be true for a single generator in idle mode, but if I can get to that point with two  running in idle at once, added bonus :)
3. Must be moveable/non permanent install - I rent, and I will want to take this fucker with me.  I also am not going to be pouring my own concrete slabs or erecting any permanent- ish buildings on the property for the same reason.
4. Must keep the generators cool enough that they can run in idle mode indefinetely (which in practice means 100 hours; the oil change maintenance time for an eu-2000i).
5. Must facilitate the use of an external fuel tank for extended run times

My idea was to build a (big, fucking heavy) box out of primarily 3/4-inch MDF.
The external walls + ceiling of the box are made of 3/4in MDF along with the long-side walls of the internal box.  The baffles and the interior box's short side walls are made of 1/2-inch MDF.

Since MDF is solid and dense, it does not resonate well with sound; that's why we make speaker boxes out of it :)
If the MDF isn't enough, I have butyl mat sound deadening material (RAAmat) that I can use to mass-load specific points further, and sound deadening closed cell foam to cancel echoing soundwaves.

The box has NO FLOOR/bottom.  The generators thus have no direct contact with the box; the box is be placed on the concrete floor of my garage (in the future, i'll have a special slab just  to mount the box to, but for now....), and the generators be placed directly on the concrete slab.  This point is important - if you build a box with a floor, the generators will shake that  box a ridiculous amount due to the amount of shaking/vibration the generator itself produces, and that kind of vibration produces low frequency sound waves on the outside of the box.

Low frequency sound travels a long way, so this is a very Bad Thing(tm).  High frequency can be blocked easily. Low frequency goes through and around shit, so you need to keep as much low  frequency sound in the box as possible.  Thus, this box is intended to be used directly on top of a concrete slab that the generators are sitting on, and it seals to the concrete by way of  3/8 inch thick rubber weather stripe tape.

MATERIALS REQUIRED:

To accomodate 2 eu-2000i's, I needed:

Enclosure itself:
2- 4'x8' Sheet of 3/4-in MDF
0.5- 4'x8' Sheet of 1/2-in MDF
Another piece of 3/4-in MDF just for the hatch
2- Square 10in attic vent
2- 120v Cooling fans.  I went with these because of their extremely low sound profile (49db!):
Rotron CLE2L2
2- Computer Power cables for cooling fans (chop end. Solder to wire leads on fans)
40Ft- Weather seal rubber foam (3/8 in thick) (seals bottom of enclosure to concrete floor)
20Ft- Door sealant (seals enclosure 'hatch' to top of enclosure)


While you could use the box as-is without any external fuel, your run time would be pretty shitty.  I plumbed the enclosure permanently with fuel lines, and added quick disconnect fittings  to allow me to easily connect the external tank and generators themselves to the existing fuel lines in the enclosure.

Plumbing for Fuel:
Numbers here are highly dependent on what exactly you do for fuel... I have already increased the #s here so I will have spares of each type of QD, since I used BERGS tank +caps which came with connectors for the 'upper red caps' :)

15-20Ft- 1/4in Fuel line
5 Parker DM-121-4FP- Quick Disconnect (Male NPTF 1/4-18 Threads) (nipple)
5 Parker DM-122-4FP- Quick Disconnect (Male NPTF 1/4-18 Threads) (receptable)
10- 1/4 Fuel Line (barbed) to Female NPTF 1/4-18 adapters Parker 26-6-4
1- Branch Tee fitting (barbed 1/4 fuel x2, 1/4-18 NPTF x1) Parker 232-6-4
1- 90 degree elbow fitting (barbed to 1/4-18 NPTF) Parker 230-6-4
1- External Fuel tank of your choice.  I bought a single run BERGS system because it got me pre-made fuel line with Parker QD already installed on one end and a 6 gallon tank, but  you could use anything you want; a Moeller boat fuel tank would be great for a pair of generators as it is easy to find in 15-25gal sizes.  You'll need a  'upper red cap' for each generator to allow you to plumb it into the system.

Note that the caps themselves come with the DM series parker quick disconnects (nipple) for the cap and a fuel line with the female DM series QD on one and, and an NPTF (male) fitting on  the other end already crimped.  The NPTF (male) fitting to Parker DM QD(female) hose that came with my BERGS single run system is perfect to run from the BERGS fuel tank to a DM series  nipple fitting on the outside of the enclosure, so I used one hose that came with my red caps for this fuel line run, and kept the second one as a spare just-in-case.  I then custom-made  the fuel lines that run from the permanently installed fuel line in the enclosure to the caps of the generators; they both have DM series QD's on both ends so I can snap the fuel lines on  to the caps and into the plumbed fuel line, and remove the 2-3 foot fuel lines entirely when the generators aren't in the enclosure.

Since the NPTF fitting that comes with the cap is NPTF male, and I was unable to find a T splitter that had an NPF Female on it, if you wanted to use your second BERGS fuel line inside the  box for one of the generators, you'd need to get one of these to adapt the 'branch tee fitting' male NPTF above to connect to the parker fuel line...  Female NPTF<->Female NPTF coupling

If you were only using a single EU-2000i, you could just run a (thin enough) standard power cable out of the enclosure directly from one of the built-in receptacles... but with 2 cooling  fans needing power, I used both of the standard plugs on the EU-2000i just to power those two fans.  Obviously that wasn't necessary; I could've used a single plug to a splitter to power  both fans, then still had a 'normal' plug free - but in my case, my intention is to allow 2 EU-2000i's to run in parallel in the box, which is done by using the banana plugs on the  generators anyway.  I created my own parallel harness, and I used shielded 4mm bullet connectors so that I can use either 1 or 2 generators in the box without changing wiring harnesses.  It  also allowed me to go ahead and just install a 30a twist-lock receptable on the outside of the box so that the pair of EU-2000i's can provide their full power.


Electrical Wiring:
4- Shielded 4mm Banana plugs - I bought  2 of of these Mueller shielded banana plug - 36inches, and wired my own.  You could always scavenge from the official Honda parallel connectors if you wanted to and it'd be cheaper.
3ft- 16ga wire for grounding generators to eachother and wiring ground into the 30a socket
1- 30a Twist-lock receptacle
3-4ft- 14/3(or 4) Wire (runs through the box; 30a receptacle on one end, solder parallel harness from gens to other end)

Here's my diagram of the box in it's semi-final form:

The original is bigger than the forum is showing it: click here to see the original
And here's a link to the source file where I have each system separated into a separate layer, so you can easily show/hide any parts of the box, electrical, or fuel lines just by toggling 'Layer visibility' on that layer.  It's in .pdn (Paint.NET format), so you will need to get Paint.NET to read it.
You can download Paint.NET for free HERE

For my box, the baffle chambers are 6 inches wide.
The holes cut in the baffles are 4 inches wide.
Every other baffle is reversed, so the air must travel 20 inches vertically up or down each time to go through the next baffle's hole.

I was overly ambitious with 12 baffles per side; I think I would need a serious A/C blower motor to generate enough pressure to actually vent through that kind of distance.
Instead, I used 6 baffles per side.
With 6 baffles that means the air is travelling through ~1200 inches of distance before it exits the box or enters the inside chamber, each baffle chamber is totally sealed from the outside, inside, and next baffle chamber except for the 4 inch hole.
I also created a 'dead space' area on each side of the box by moving the fan/vents over a bit; the hoses for fuel and wiring for the power are going to go through the 'dead space' area rather than the intake vent chambers.

Not only does the air travel a long distance, but it goes around ~10 90 degree bends before exiting the box.  It is REALLY DAMN QUIET.

So I called up my friend who is a carpenter and asked him to help me since I cannot make something this big + hefty myself.  He did a great job.
At this point, I have:

1. The box assembled with baffles
2. One of the two fans installed (the exhaust inside the inner box)
3. The bottom of the box is lined with the rubber 3/8' thick tape.

At this point, I have connected a single EU-2000i to the internal cooling fan and lowered the box to seal it inside.  I ran it for 5 hours on econo-mode without any ventilation.  Interior box temps were approx 130f when I lifted the box up.

A single EU-2000i in this box in economo mode is virtually impossible to hear more than 30 feet away from the box.
At 3-4AM, I went outside and walked around my house; I had to be within approx 40 feet and in direct line-of-sight of the box to hear anything, and at that distance it sounds like an engine running REALLY far away.  In order for someone to know i'm running the generator, they would have to walk right up to my house.

Next to be done is to:

1. Run the fuel lines; I got the wrong friggin quick disconnects so I am waiting on fuel fittings to finish this step
2. Create the wiring harness for the parallel generators, install the 30a receptacle on the outside of the box, and wire the harness into the 30a receptacle
3. Cut the hatch, find some kind of clamp based mounting hardware to allow me to clamp the hatch down to the top of the box while everything is installed & running.


Here is a picture of the box last weekend, before I added the rubber foam to the bottom.  If you look past the top of the box, you can see my yard fence and 2 cars.  1 eu-2000i in this box cannot be heard by the time you walk to the second car.  On the close side of the first car, it sounds like a car engine running 3 blocks away and is non-directional sound.

You can clearly see the 'dead spaces' I added by moving the vents; it also shortened the path the air has to take.  I have a feeling I screwed up there and should've kept the air path as long as possible but simply removed some of the baffles to allow for greater flow.  Idunno, this is the first attempt for me :)

Sounds like a great build. You sure have done your planning.

When you get a chance to stand back and admire your handy work, I'd love to see video of the finished product.

Absolutely :)  I should have everything I need this week, so next weekend I am planning on cutting the hatch, and plumbing the fuel.
I'm hoping someone here will have an idea for how I can have the hatch be NOT hinged, fully removable, but still be able to be clamped down to the top of the box in some way while it is installed.

see also this excellent thread:

http://www.ar15.com/forums/t_10_17/644329__ARCHIVED_THREAD____DIY_Generator_Power_Cables_and_Install.html&page=9#i11103339

Actually, that thread was one of the main sources for my inspiration!  :D He made a great permanent install enclosure but it didn't turn out to be particularly quiet :(

I think a lot of that has to do with the generators sitting on a wooden floor that is part of the box, but also, no baffles were installed to muffle the sound of the generators and the fan; it's just an open hole to the main chamber.  My aim is primarily to be as quiet as possible.

The current setup with fan running, 1 generator in econo mode is so quiet you can whisper to someone on the other side of the box and be heard clearly.  I'll need to get a dB meter so I am not making false claims as to just how quiet it is :D   Anyone know of a meter that is accurate at these levels that won't break the bank?  This project turned out to be expensive once I decided to run external fuel with quick-disconnects...

1. are you sure those Mueller test leads, with 18AWG wire, are suitable for interconnection of the two generators?  how much current is carried by the parallel cables?
2. your ground wire should be AT LEAST the same AWG as the current carrying conductors.  for a 30A circuit you should be using a 10AWG ground wire.
3. your current carrying conductors (14 AWG) are undersized.  a 30A circuit requires 10AWG wire.
4. you should not be soldering ANY current carrying or ground conductors; this is for safety and reliability reasons.  such conductors should be mechanically clamped by machine screw thread means.

ar-jedi

forget the meter.  there is no way to make measurements which can be accurately compared to others' measurements taken with other meters in other locations and with different measurement arrangements.  for example, a measurement taken with a generator sitting on grass will differ from a measurement taken with a generator sitting on concrete.  tiny changes in measurement distance, angle, and microphone characteristics will make it impossible to compare with other results.  for A/B'ing your own setup as you make changes, sure; but for comparing with others, not so much.

ar-jedi

last question -- are you running the generator(s) in your garage?

ar-jedi

Thanks a ton for taking the time to post and give me advice; I appreciate it, and that's why I posted :)

Yup.  It's more of a car-port actually, though i call it my garage :)  It's open air, without walls, but covered with a roof.  I won't be suffocating myself :)  I'm going to set up one fan outside blowing air across the exhaust vent from the box towards the yard to make sure there's circulation in the car port too.

Don't cheap out and burn the place down.

Buy the correct parallel kit from Honda.

Parallel runs are considered a big no no. No solder joints. No matter the length the grounded conductor should be the same size as the current carrying conductors.

To yourself a favor go to Lowes, Home Depot, or local bookstore and buy a book about residential wiring basics.

Follow the link AR-Jedi posted and you should be trouble free.

That is a MOST AWESOME enclosure!

Several observations:

1. Your port holes are considerably smaller than the fans - which means that they're going to drastically reduce the fans' airflow.

2. Lining a few of the baffle walls with sound-absorbing material (carpet, acoustic foam, etc.) would probably help attenuate some frequencies that are currently getting through.

3. At some point, X number of baffles reduces the sound enough that most of the remaining noise leaks out via other paths - i.e., the unbaffled sides of the enclosure vibrating, leaking enclosure seams, etc. I would bet that you reach that point with just 3 or 4 baffles.

BTW, you don't need a super-accurate sound meter to make before-and-after comparisons, or to evaluate the results of enclosure modifications. Even a really crappy meter will give you useful comparative measurements.

Unfortunately, the kit from honda is for a companion model + normal eu-2000i. With 2 eu-2000i, you need to wire your outputs from the generators directly to a plug rather than just using them to connect the  2 generators in parallel.  Don't worry, it's perfectly OK to wire multiple eu-2000i's up in parallel to a receptacle; in fact, there's a triple parallel kit sold by wise sales that works this way; each generator outputs from it's bullet connectors and their outputs are joined in a 50a receptable.  If you do a brief google you can even see a youtube video of someone running 4 in parallel to a 50a receptacle :)

If the ground wire is larger wire than the current conducting wires, why would that be a problem?

The link AR posted involves a more complex system being installed into a house; a lot more than I am doing.  This will not be permanent, since i am renting...i'll be running a 10/4 cable from this enclosure through a window and into my house to power stuff :)  When I buy i will be looking to have something properly installed into the building but that's not on the books for now.

1. Yep...but they also drastically reduce the sound signature.  If i have heat problems, i'm going to double up the holes so there'll be 2 4inch holes per baffle.

2. Is on the to-do list...

3. I bet you're right... I really wish I had time to do a ton of tests with various baffle constructions to see how much of a difference it makes...  MDF is really dense... I went with 6, but I have a feeling I could've done 3 and doubled the size of the holes but still had acceptable results in the sound reduction department.

for the current carrying and ground conductors used for power distribution, the length of the wire doesn't matter (until they get really long and into a voltage drop situation).  

so, in general for AC branch circuits: 15A = 14AWG.  20A = 12AWG.  30A = 10AWG.  50A = 6AWG.  

as for downsizing the conductors because "realistically neither generator is going to be running @ absolute full load" -- this is not the issue.  current carrying and ground conductors used for power distribution are sized based on the capacity of the source and the overcurrent device employed, and not the expected end load.  

you can see by the diagram below that the inverter outputs are directly connected to the banana plugs, bypassing the circuit breaker; we know the short-term output limit of the inverter module itself is 2000W, or ~16.7A at 120Vac.   for this reason the parallel cable should be 12AWG.  i surveyed a few websites and youtube videos detailing DIY parallel cable approaches and they are all using 12AWG wire.  i'd be interested to know what gauge the OEM Honda parallel cable is.

ar-jedi

http://tinypic.com/r/mcavpi/5

AR-Jedi thanks for posting that schematic that is the first time I have seen had they applied the jacks.

Must be some very intelligent sensing and control going on to make sure all generators are phase synced.

Always wondered the same thing...

Seems ridiculous...  Maybe they serve as 'fuses'?  

Great job and initiative Headless.

This is a real contribution to our knowledge base!

How abt considering a low frequency [low power consuming] sound generator outside that will mask any residual low frequency sounds from the genny?

A boombox turned down and plugged into the genny maybe??

Nothing wrong with solder joints if used appropriately...

" ran it for 5 hours on econo-mode without any ventilation. Interior box temps were approx 130f when I lifted the box up."


Cheap wireless thermometers are only a few bucks and can enable constant temp monitoring.

Once you start developing some power from both genny's the requirement for more heat exchange is going to go way up.

As will sound levels.

I've been doing a lot of work developing a low frequency detector the past few months...

You would be amazed how 'low freq' impulses are conducted thru concrete.

It would be worthwhile to isolate the gennys from the concrete floor using something like blocks of pink rigid foam insulation, then a layer of 2 inch concrete tiles, then maybe another pair of layers, then the gennys.

Yep - Big-time.

Onan used to offer enclosed and unclosed versions of essentially the same RV generators. Even with factory-engineered enclosures, the continuous power output was always derated quite a bit. They simply couldn't get enough airflow through the enclosures to specify the same power ratings as their unenclosed counterparts.

For weatherproofing your enclosure, you might look at "laminating" the outside walls with fiberglass-reinforced plastic paneling ("FRP").

It's sold in 4' x 8' sheets at Home Depot, Lowes, etc., right next to the wood paneling, and is commonly used for lining kitchen, shower and bathroom walls - Also quite popular for moisture-proof, washable interior walls in dairies, livestock buildings, etc.

2-part marine epoxy does an excellent job of permanently laminating it to plywood - Cut it to fit, apply a thin coating of mixed epoxy to the underside, and clamp it to the wood surface for 24 hours until the epoxy sets. It withstands weather very well - I've got pieces that have been outdoors for over 10 years, and still look brand-new.

Good info!

I'm confused, because I've been looking all over the place and found a lot of places that even have calculators designed to tell you what size wire you need, based on the amount of amperage and type of power you're using; I hope you can tell me what these places are doing differently in their calculations than what you are, because this has really turned my knowledge of current carrying wires on it's head; every piece of wiring I've done with my DC projects has been based on the length of wire run & max current requirements... The batteries that I used in remote control plane applications put out 45+ amps of continuous power for ~5 minutes at a time, and I used 12ga wire for those; but leads were only ~1 foot long; the wires themselves never got close to warm - but from what you are saying, regardless as to length, 10ga is the minimum wire gauge if the wire will ever see 30amps of current, even if the wire is only 6 inches long? Why are there so many places telling me what the length of wire does matter when deciding minimum gauge to use?  Are you referring to code/legality rather than purely electrical requirements maybe?

I've got a bunch of 12ga wire here; I'll re-solder the banana plugs from Mueller with 12ga lengths.  Just trying to get an idea of whether I really need to replace the <2 foot of 14ga wire between those leads and the 30a L14-30P receptable with 2 foot of 10ga wire instead..

Thanks again for the input, I appreciate it :)

I'ma kill that low frequency sound entirely if I can :)  A boombox running would also attract attention to my place that i'd rather not have...

Yup, with econo mode OFF, I can hear the low frequency sound of the motor until just about the fenceline in my picture.  I fully expect for it to be louder when under a full load; i've been testing with a space heater that lets me put 750w or 1500w of load on the generator. @ 750w it's still quiet enough that it can't be heard from the fenceline of my property, but at 1500w it can be.

However, my use case is going to be 90% < 600watts load, and 2 eu-2000i's should be able to generate that wattage without needing to rev up.  What i'm hoping for is basically silent running @ idle, and barely audible from the road - but non directional sound - if it's completely quiet outside no traffic noise etc.) and they are under load approx 50-60% load.  My use case is going to be to power a fridge, a window 12,000 BTU A/C, and some low power LED lights...oh...and fish tank air pumps + filters so my fisheez don't die :)  Those will, combined, pull <50 watts.  If i get some noise bleed-over when the generators rev up for start-up surge, that's fine. Just don't want people to hear an engine running while they are idling.  The window A/C is going to likely be louder than the generators are judging on the current amount of sound escaping the enclosure.

Heat is the big unknown for me; it's just getting up to normal temps here in FL so I have yet to try it on a truly blistering 95f day.  I'm optimistic but I wouldn't be surprised if I can't run these @ full load in this enclosure for extended periods of time.  Thankfully I won't need to; i'm looking for bursts of 100%, and hoping the ventilation will be enough to keep temps under control when that surge is done and they are back to idle current.  We'll see how well it works. I have a feeling my 550CFM ventilation fans might need to instead be high pressure blowers of some kind because I made the baffle holes so small.  Any experience with this?

I think I would be; I didn't think that a concrete slab would vibrate with these suckers on rubberized feet. Where do you get 2 inch concrete tiles from?  I don't think the box is tall enough to accomodate that added 4-6 inches of height; it's 20 only inches tall...but I could try 1 layer.

That is totally awesome.  I made the box from MDF for it's density, but it's super sensitive to moisture and that concerns me.  I had it painted with exterior paint that is quite rugged, but your solution would be a whole lot better.  How do you cut that stuff?

What AR-Jedi provided you was from the National Electric Code that covers residential, commercial, and industrial applications. What your use to working with is what we call low voltage dc applications. Totally different ballgame. This is why I recommended you picking up a residential electrical basics book.  

ah, gotcha.  I can see how NEC code for house wiring would be very specific; I just wanted to make sure my understanding of the underlying electrical concepts was not flawed.  If I understand correctly, the NEC rates their specs conservatively, and I can see how they'd go with blanket statements to make it easier to tell if things are in compliance.  For example, if they gave you leeway to vary gauge per x-amp-circuit based on on the length of wire run, then to be sure something was code compliant would require measuring every single circuit's wire length... easier to say, 'all runs of x amps must be y gauge' and know that even hundreds of foot long runs would be fine with the spec.  Am I understanding right?

In other news, I drilled the 1/2 inch holes in the enclosure tonight and ran the 1/4-in fuel line through it.  It was a tight enough fit that I don't think i'll even need to seal around the tubing with anything :)
The last of my gas fittings should be here in a couple of days, then i'll get some detailed pictures or a video of the fuel plumbing setup.  I think it'll be a total of ~10 foot of fuel line.

Also, does anyone have any ideas on how I could retain the 'hatch'? I'd like it to be removable, so probably not hinged to the box.  I was thinking about some kind of clamp-downs but I can't seem to find anything that would work on 3/4in MDF...  I'm planning on cutting the hatch next weekend; just bought a jig saw and did some test cuts on scrap.  My wife cut some holes too and said that 'power tools are awesome'... That was fun. :)

Also, the box is pretty heavy (200+ pounds!) and I want to be able to roll it into/out of position on wheels. With wheels on it, it'd be semi-portable. The way it is now, it is very difficult for even 2 reasonably strong people to move around by lifting; you really need a hand cart....

I'm thinking about installing 4 casters on 1 of the sides of the box so i can tip it up onto the casters, then roll it around and put it back down into position.  Kinda like a roll-away bed like you see in hotels.  I'm wondering if the wheels can be placed right on the 4 corners of the side I want to make roll around or if 2 of them need to be indented part of the way so that they are closer to the 'middle' of the box. Does anyone know anything about this kind of 'tip-onto-wheels' set-up?

Something like this..

A pair of tin snips works OK.

A hacksaw blade in a jigsaw also works fine.

What about rubber blocks or a mat?  I would think that might be able to help.
If you were building an outdoor enclosure for something like this would you end up building a pad for the generators and a separate foundation for the box?
I would think bringing cool air in from below and venting heat and exhaust out the top might help cool them off.

Check McMaster Carr or MSC Industrial

We use to use some green vibration reducing pads that were about 3/8 thick and 4x4 square.

They are concrete garden tiles from home d , ~$3 each.

Horse stall or exercise room floor mat should provide enough isolation from the slab.

The fan your using likely isn't rated for the static pressure required to get much flow thru your baffle system.

Grainger has a quite educational section on various blowers and static pressure they're capable of.

EBay has lots of higher static pressure blowers for less than $100, and here's a good place to start looking.


Blowers

Anti-Vibration Pads work pretty well. You will need to size width and thickness according to your application. I have used these for under HVAC units. I like whisper quiet compressors and air handlers. In a previous life when I used to build recording studios, we used to put the whole exterior frame of the building on top of sheets of stuff very much like these, only probably not as good. Better materials and stuff now... Anyways, it decoupled the building from the slab it sat on in the lower frequencies.

Now you've done it.  I need to find one of those that is  <50db ;)
The current fan is definetely pushing air through the baffle system, but also is definetely not pushing what it's rated for (550cfm)...but all of the higher pressure fans seem to max out at 300-400cfm unless they get insanely loud.

I wonder: is there a piece of equipment or methodology that doesn't require massive investment of $$$ to figure out what kind of resistance my baffle system is producing?  Then it looks like I could compare spec sheets and see what the real-world flow rate would be with a particular fan.  I have the flow vs. pressure curves for my current fan and it looks like all of these ducting fans provide the same kind of datasheets...

Flo/Therm.  you should be able to pick up a license for about $10K.  
http://www.mentor.com/products/mechanical/products/flotherm

seriously though, tubeaxial fans get less and less effective as the static pressure goes up.  
get a backward curved impeller (aka reverse impeller) blower, as they have much flatter curves and will deliver rated airflow into much higher static pressure.

ar-jedi

LOL, my baffle box would cost 11k.  Hell of an enclosure.
Anyone got a license they could run some numbers for me through? ;)




Abysmal performance into pressure.  My issue is that I have no idea wtf the static pressure of my box is so I can't even begin to tell where on the curve I am. :(  0.3 in h20 looks to be 'not much pressure' in the grand scheme of things, and it's flow is only ~45cfm @ that pressure.  Air pressure + cooling is one area I have no experience with at all.

Rather than using huge fans to squeeze a lot of air through small-ish ports, another approach would be to open up the size of the ports somewhat.

For example, you're currently using round holes for the ports. Completely cutting away the part of each wall where a port currently is would give you considerably larger, square or rectangular openings for airflow.

Even so, the fact that sounds still have to take a labyrinthine path to exit the enclosure would provide considerable noise reduction.

Hmm.  chop chop.  I could double the size of the baffle holes pretty easily; they're screwed into the enclosure so to be removable Just In Case(tm).  I just wish I had some way to actually tell what the pressure is and how it would change if i were to do that.  Seems like a serious physics problem that isn't easily solved without $$$$$ and training though. :(

I was planning on mounting the intake fan on the outside of the box because AFAIK the tubaxial fans do better pushing into pressure than pulling through it.

If I go with blowers backwards curved fans, it looks like I I could mount both inside the box as those appear to be OK for 'suction' type applications as well; is that true in your experience, jedi?
If i can mount both intake + exhaust inside the box, then the fans being 60-70db would be fine since their noise would also be contained inside the box; seems like there are good options in that volume level that can really move a ton of air against high pressures.  Seems like they are all rather expensive though...any advice on what brands I should be looking at or sites to find good selections?  Seems like most of what i'm finding are super specialized aerospace + medical purposed fans that cost 2 grand+...heh.

Measuring any significant material pressure drop/increase, can be done with a simple manometer.

Take some 3/8 ID vinyl tubing, tape a section abt 24" long at an incline of about 20 degrees, for an elevation difference of abt 6"  ---on your box.

Then tape each side of the 18" section in an upwards direction abt a foot higher.

Fill the 18 inch section and the vertical ends partially so the water level is abt half way across the sloped section.

The ends of this config can be inserted any where  you want to measure pressure vs ambient.

You can measure pressure drops or gains differentially using both end of your new manometer and inserting them at the targeted places.

The differential in the water column is the pressure difference in, say, inches of water.

You could use mercury, but the sensitivity might be less with a home-made unit.


You can use this technique many ways, for instance to monitor the pressure drop across the filter, or the coils, in your A/C.

Search "Regenerative Blower".

The have outstanding static pressure and sometimes are found cheaply at auction or ebay.

I bought a small years ago at an auction for ~$75 and was thinking of using it to pressurize A-C fuselages.

Grainer will break the bank for these tho.

Link

Concrete inertia base with isolators should reduce low frequency problems.