Here is my parameter file for this driver for WinISD Pro ver 0.50a7

This driver performs best in a sealed or Infinite Baffle enclosure. For comparison purposes, I've relaxed the 130litre limit on box size - the higher Vas of a 15inch driver makes this mandatory for a ported design.

According to William Cowan at cowanaudio the suspension becomes noisy above about 12.5mm excursion and Xlim seems to be 20mm one-way. The following designs stick to the 12.5mm limit. When working out maximum power for the IB designs, the 20mm limit is used.

Firstly I'll present some conventional sealed and ported designs.

Further down in a separate section are some Infinite Baffle designs for those with deeper tastes and deeper pockets....

SPL

Ported design scores well but at the expense of a huge 400litre box and high group delay.

Jaycar 49litre design needs 250w. This is from an unboosted amp. If using the Jaycar amps which have boost @ 35hz, the response will be worse.

150 litre sealed design is easiest to live with - not huge, no filter required and only the 150w Altronics amp required. 10dB down on the ported design at 20hz though, so will only be half as loud for serious HT use.

Cone excursion

The ported design requires an 11hz high pass filter

Port air velocity

Infinite Baffle Designs

An Infinite Baffle (IB) design is a sealed design where the box is infinitely large. In reality, the box needs to be at least 10 times the combined Vas of the drivers. The box is usually the roofspace, a space under the house, or an adjacent room such as a garage.

Since the drivers are not compressing air in a box or charging up a port, the transient response is excellent. The unrestrained movement also means that it takes less power to reach excursion limits.

Since we're using less power and doing without any contribution from a port, more drivers will be needed.

I initially thought that you would add a Linkwitz Transform to sacrifice SPL above 30hz for a flatter response. It's been pointed out that this is not the case, since room gain makes this unnecessary.

If you're interesting in exploring IB further, check out the experts at the Cult of the Infinitely Baffled. To use their forums you need to register, but it's free and worth it.

All designs are modeled with a space of 10,000 litres. This is a bit larger than the minimum size for 4 drivers ( 150 * 4 * 10 = 6k ) and a bit smaller than the minimum size for 8 drivers ( 12k litres). It's around half the 18k litres that a twelve driver design would like - increasing the modeled volume just results in slightly less power being required than shown here.

SPL

The solid lines are for when excursion is kept to 12.5mm to keep distortion at bay.

The shaded areas are for when excursion is allowed out to 20mm, which is the suggested Xlim. This will involve some distortion, but the drivers will be OK.

Cone excursion

The excursion graph is the same for all three designs.

The black line is the resulting excursion for:

• a four driver design with 190w applied or
• an eight driver design with 410w applied or
• a twelve driver design with 670w applied

The grey line is the resulting excursion for:

• a four driver design with 480w applied or
• an eight driver design with 1050w applied or
• a twelve driver design with 1700w applied

Displacement

When comparing IB systems, a common measurement is the amount of air displaced, which is worked out by the formula:

Displacement = Sd * Xmax * 2 * Number of drivers...... where Xmax is the one-way value. The result is expressed in litres

EP1500 at StoreDJ - $499

EP2500 at StoreDJ - $649

I purchased an EP2500 from them recently, and apart from waiting for an overseas shipment to arrive, found them to be a delight to deal with. They rang to confirm the order prior to shipping, and the package arrived promptly and in good condition.

Project cost - drivers plus amp

Four driver project using EP1500 $899 - (buy four drivers @ $100ea = $400) or
Four driver project using EP1500 $949 - (buy five drivers @ $90ea = $450 keep one as spare)
Upgrade to EP2500 add $150

Eight driver project $1369 - (buy eight drivers @ $90ea = $720) or
Eight driver project $1449 - (buy ten drivers @ $80ea = $800 keep two as spare)

Twelve driver project $1597 - (buy twelve drivers @ $80ea = $960)

Add another $200 for a Behringer Feedback destroyer which allows you to even out the in-room response. Peaks due to room nodes can be cut with up to 12 parametric equalisers. You can also factor in a house curve for a tailored bass response.

The DSP1124P has been supeceded by the FBQ2496. Here's a comparison:

Rumor has it that you can pick up the older model for about $170 so shop around... If you go for the FBQ2496, don't confuse it with the DEQ2496, which is a crossover management device.

You can analyse your room using the free Room EQ Wizard software written by John Mulcahy.

The software will even upload the new settings into the BFD via the MIDI port on your computer. If your BFD is ver1.3, you'll need to enter the settings manually. If you have a BFD, you can check it's version by holding in the Filter Select button during power up. Mine turned out to be v1.3, so it was manual entry for me! Reading the values from REW meant that this was no big deal.

See here for a guide on using REW.

I've used the software to explore a couple of potential locations for an IB. See my writeup here.