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3Pi or 4Pi? [message #91771]

Tue, 28 April 2020 16:04

Jimmy D.
Messages: 3
Registered: April 2020

Esquire

I'm new to the forum. I want to help my graduating son build a pair of high efficiency speakers to compliment his singled ended KT88 amp he built. I want a compression driver and a very high efficiency. Looks like my options with Wayne's designs are either the 3 or 4, that can fit a modest space at least.

A couple questions:

Why is there so much difference in efficiency between the 3 and 4?

How can I get a copy of the plans for the 4?

Are the kit parts readily available for the 3 and 4?

What is the approximate -3 dB point for the 3 and 4?

Thanks in advance,
Jim

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Re: 3Pi or 4Pi? [message #91774 is a reply to message #91771]

Tue, 28 April 2020 16:35

Wayne Parham
Messages: 18785
Registered: January 2001

Illuminati (33rd Degree)

The real difference - besides efficiency - is the choice of midwoofer brand you prefer. It's kind of like a Ford v. Ferrari thing here. In fact, the high-end option for the four π is American (JBL) and the high-end option for the three π is Italian (B&C). Both are excellent choices, so you're just choosing between two top-notch manufacturers.

You can see the specifications for each model here:

Parts are readily available for both models. We sell complete kits, or we can sell you just the waveguides and maybe the crossovers of you want to source the drivers yourself.

The waveguide is the only part that you must buy from us, because we're the only source for that part. But everything else can be purchased wherever you wish.

Beyond that, I encourage you to look through the Pi Speakers FAQ, especially the section called "Models, Upgrades and Driver Characteristics." This will help you learn more about each model and option available. That might help you decide which model is best for you, and what options you think you'd like to have.

Once you decide, let me know and I'll send the plans.

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Re: 3Pi or 4Pi? [message #91809 is a reply to message #91774]

Sat, 02 May 2020 07:35

Jimmy D.
Messages: 3
Registered: April 2020

Esquire

Wayne,

Why does the design of the 3 pi have a 2" wider baffle than the 4 pi? I'm struggling to find a design less wide however I'm guessing that reducing baffle width to minimums will affect efficiency?

Jim

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Re: 3Pi or 4Pi? [message #91812 is a reply to message #91809]

Sat, 02 May 2020 13:35

Wayne Parham
Messages: 18785
Registered: January 2001

Illuminati (33rd Degree)

The three π model is slightly larger than the four π, that's true. Both have similarly sized baffles though, and they're large enough that baffle step happens right about the Schroeder frequency. So below the baffle step, we're in the room's modal region.

Instead of adding energy into the mains to compensate for baffle step - or worse yet, removing energy above the baffle step as it usually done with BSC filters - it's nice to be able to use a flanking sub approach. This provides simultaneous solutions to three important acoustic problems:

Provides baffle step correction (BSC)
Mitigation of Speaker Boundary Interference Response (SBIR) and higher-frequency room modes
Provides deep bass extension

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