"Cult of the Infinitely Baffled"
IB Subwoofer (aka IB subs)- FAQ Pages

Generic 'how-to' guide for designing, building, 
  installing, and fine-tuning your IB subwoofer

Page 2

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Peek-a-boo...do I see you?
aka hiding and protecting your IB


1) Floor mount IB solutions:

The options are limited for floor mounted IBs, since in most instances one needs a grate that's strong enough to walk on. 

One possibility is a DIY welded angle iron frame with inserts. For the inserts one can use lengths of steel rod, or obtain a wide variety of the decorative elements used for security doors. These can either be welded on or actually crimp-on with built-in clamps. 

Check your yellow-pages for local suppliers before going to the 'net', since shipping cast metals is a bit pricey. Some places sell cast aluminum decorative elements.

New or antique cast floor grates/registers are another option. These are of course fairly expensive

Standard preformed cold air return grates can be used for a floor covering where there is absolutely no foot traffic. Unfortunately these do tend to get beaten up by vacuum cleaners

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2) Wall or ceiling mount solutions:

Standard grill cloth covered frame is a quick and fairly easy solution. Make a frame from 1"X2" stock, attach the grill cloth with a staple gun. The best technique for stapling is that used by artists to 'stretch' their canvas for painting. This LINK shows the proper technique to avoid wrinkles, One should use a staple gun instead of the hammer and tack method shown.

Grill cloth can be obtained from any of the larger speaker supply houses like Parts Express, or one can simply go to a cloth/fabric store and by a 'sheer' polyester single-knit fabric. 

With high excursion/ high output drivers it is possible that the cloth will pump in and out (flutter). Other than a potential issue of esthetics, this doesn't interfere with the performance of the IB.

This is Prototrax's very nice oak trimmed grill cloth 

Below is a ceiling mount IB built with a hinged grill 

 

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For those preferring an even easier grill, get the lengths of white or bronze aluminum extrusions used for DIY window screens. The sections snap together with plastic L's. The groove for the rubber spline material will hold the cloth in place.

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Grill frames can most be easily held in place using Velcro. Home center stores sell both 'Marine' (blue) and 'Industrial' (white) Velcro. These types are much stronger than the standard Velcro sold in hobby or craft stores. I recommend supplementing the factory applied adhesive with hot glue or staples, depending on the weight and orientation of the grill.

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A newer method to attach grill frames is to use multiple small rare earth magnets. These are mounted in both the grill cloth frame and in the wooden ceiling or wall frame holding the IB.

This is a close up of a 3/8" dia  X 3/16" high, neodymium magnet sold by Parts Express

The small dots seen in the edges in the ceiling frame below 
are rare earth magnets similar to the one above

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Cold air return grates/grills are also a popular choice. These are available in a variety of sizes, and can be painted to match the interior of the room. Most home center store carry a vide variety of these grates usually painted white.

This is a wall mount IB using cold air return grills to cover 2-15" woofers. 
Note that these grills do not cause 'chuffing'

 

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Wires, wires, and more wires.....

People frequently have questions about how to actually wire the voice coils of woofers in their IB. This LINK (also posted on the main FAQ page) has the information needed to wire virtually any combination of drivers. 
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Wires, wires, and more wires.....part deux


Which interconnect should use for my IB?

The world of high-end boutique wire combined with marketing hype has everyone neurotic about what wire to use for what application. The concept of needing a specialty interconnect for a subwoofer is absurd. We're dealing with frequencies around 80Hz and lower. So ANY good quality, shielded IC is fine for your IB. If you lay awake night worrying about the 'rhythm', 'timing' and 'pace' of the wire running to your IB, then buy something REALLY expensive, and you'll sleep better. For the rest of us, virtually any good quality shielded interconnect will handle the signal going to your amp.

But..... what about the speaker wire from the amp to the IB?  

I use 10 gauge 'Sound King' wire on both my IB's. This is a generic vinyl (PVC) insulated, parallel lead wire. People leave the house slack jawed after hearing the IB's. They rave about the levels of detail they've never heard before.  So I don't think that investing high-end speaker wire for a subwoofer is necessary

Disclaimer........

There are obvious and audible benefits to good quality ICs and speaker wire when used for full range speakers. Given the L>C>R (inductance, capacitance, resistance) of all wires, they do function like passive tone controls. So what's good for one person's system, won't necessarily be good for someone else. In home auditions are important to find the cables/wires that will work best with your system.

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Special note to those using Behringer EP-1500/2500 amps

PLEASE NOTE: The big DIP switch on the back of the of the older EP-1500/2500 amps have  +/- marks molded into plastic housing. These molded in markings are opposite the settings that are screened in white paint on the back of the amp. Follow the +/- white painted on the graphics, DO NOT use the markings molded into the plastic on the switch itself.

If you're using one of these amps and you don't think you're getting enough low frequency output CHECK THE POSITION of the selector switches.

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Got Amps?

Can I use a plate amp?

You can but IMO they're not the best investment. Most don't have enough power for a big IB. If they are powerful enough then they're more expensive that the amps on the 'Recommended Equipment page'

If I buy a plate amp I can save money because they have built-in EQ.

The built-in EQ in plate amps isn't flexible enough to adequately EQ a sub. That's why we  recommend using the Behringer DSP1124P or FBQ2496.

Which load is best,  2 ohms, 4 ohms, 8 ohm, etc? 

The answer is it depends. It depends on the amp, it depends on the drivers. Normally amps are most 'happy' running moderate loads, 4 or 8 ohms. However there are certainly many amps that will drive 2 ohms. Use 2 ohm loads if they are the only practical option. 

Why can't I run an odd number of drivers?

The answer is you can, but you must be careful how they're wired to the amp. The load on the amp needs to be symmetrical, or some drivers will be working harder than the others.  On a single channel do not run one driver in parallel and others in series, or visa versa. 

Should I run my amp in stereo, or bridge it to mono? 

Generally speaking, if stereo operation offers enough power to drive the IB to the SPLs you want, don't bother bridging the amp it's results in higher noise/distortion. If the only way to get enough power for your IB is running the amp in a bridged mode, then obviously that's what you need to do. Understand bridging the amp doubles the distortion. 

Can I plug my power amp into the outlets on the back of my receiver? 

No, power amps pull too much current to be plugged into a receiver. They should be plugged into a wall outlet or a line conditioner, (only if it's specifically designed to deliver high amounts of current)

Do I need a dedicated AC line for the power amp?

No it's not mandatory, but some people find it improves the bass output. 

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Gotta match?

Occasionally people run into a situation where they have a pro-sound power amp requiring a higher input drive level than that supplied by the output of their pre/pro or the BFD. 

If you have the subwoofer output level turned all the way up, and the output from your sub is too low, you need to diagnose the problem. Start by looking at the input sensitivity spec for the power amp and the output voltage for the receiver of pre-pro. If there's a big difference between these two numbers you may need a device that can provide a higher drive level, these are called line level shifters. 

There are numerous such devices several listed below. Most use a wall-wart power supplies. I'm not a big fan of those types of power supplies. I don't need a line level shifting device but if I did I'd use the Behringer Ultralink Pro MX882 for this purpose.

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Below are examples of the lower cost line level shifters that use a wall-wart PS

Above is the ART "CleanBox".
Here's a .pdf information sheet about it's operation. 

Testing of the CleanBox by Ilkka Rissanen shows it's probably not the best choice for IB sub owners. 

However changing the values of the two capacitors (C7-C8) on the PCB flattens the frequency response. Use caps with a value of 0.47uF or higher. There's no need for high voltage caps in this instance. 



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A similar product is the 124A Audio Level Interface from Apex systems

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Samson S-Convert

 



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Rane makes the BB22

 

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Ebtech makes a line level shifter. It's also priced at $70 from the online suppliers

 

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Remote Switching

Frequently people place pro-sound power amps in a remote location and need a unit to cycle them on/off. 

One low cost option is the  Sears Craftsman Auto Switch

 

A more $pendy option are pro-sound sequencers. 

I use a Furman PS-Pro II Power Conditioner/Sequencer for this task

Another option are the remotely controlled outlets sold by most home center stores.
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