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Smaller 3 pi construction? [message #93247]

Fri, 05 March 2021 03:13

stereojan
Messages: 7
Registered: February 2021

Esquire

Hi!

I am thinking about building a couple of speakers for the living room. My preference would be the 4 pi, but they are a too big for wife acceptance.

The compromise is to build a smaller 2-way speaker designed like the Klipsch Heresy III (24" x 16" x 13.5", tilted). I am thinking 12" woofer with waveguide tweeters. And maybe add two flanking subs in the corners next to speakers (perhaps used as speaker stands when wife is away).

Is it possible to reduce the size of the 3 pi to fit the the specs?
I guess I will lose some bass extension, but maybe subs will compensate enough.

Cheers.

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Re: Smaller 3 pi construction? [message #93248 is a reply to message #93247]

Fri, 05 March 2021 08:34

Wayne Parham
Messages: 18787
Registered: January 2001

Illuminati (33rd Degree)

Of course, a loudspeaker like you've described could be designed and I would expect it to be great, if done properly.

But don't modify the cabinet dimensions without acoustic testing, and specifically pay attention to the lower midrange. That's what is most problematic in cabinet design for a large-format two-way loudspeaker.

Also, bear in mind that another one of the things that will change is the baffle step region. As the baffle shrinks, the baffle step happens higher in frequency. The three Pi and four Pi models are large enough that baffle step is around the frequency where the flanking subs rolloff. So they provide extension, SBIR and higher-frequency room mode mitigation and baffle step correction.

More information about these issues and others can be found in the Pi Speakers FAQ.

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Re: Smaller 3 pi construction? [message #93257 is a reply to message #93247]

Sun, 07 March 2021 03:11

stereojan
Messages: 7
Registered: February 2021

Esquire

Thanks for the reply and the additional tips Smile

Seems like I have to get into some acoustic testing too. May be some of the econowave variants is an easier place to start from since I am kind of a newbie in this. The size of those designs fit my size requirements quite well it seems. I understand those design were based on your Pi speakers. But maybe not as refined as your designs.

What do you think is the easiest starting point?

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Re: Smaller 3 pi construction? [message #93259 is a reply to message #93257]

Sun, 07 March 2021 08:56

Wayne Parham
Messages: 18787
Registered: January 2001

Illuminati (33rd Degree)

Econowave guys are definitely kindred spirits. You could certainly root-around on the Econowave thread and find something that suits your needs.

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Re: Smaller 3 pi construction? [message #93407 is a reply to message #93247]

Wed, 31 March 2021 08:16

stereojan
Messages: 7
Registered: February 2021

Esquire

After some research I've decided to start out with the 3Pi kit, and try to measure and adjust the crossover to the smaller box/baffle size. Or maybe just add some simple digital corrections with the Minidsp shd streamer/dsp/dac.

I think I will go for the B&C tweeter. Not sure yet which woofer. The B&C woofer seems maybe to do better in a smaller box (+ higher sensitvity?). Any opinions on which is the better choice?

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Re: Smaller 3 pi construction? [message #93408 is a reply to message #93407]

Wed, 31 March 2021 08:40

Wayne Parham
Messages: 18787
Registered: January 2001

Illuminati (33rd Degree)

The B&C 12PLB100 is the highest-quality option. I'd go with that.

https://audioroundtable.com/images/thumbs-up.gif

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Re: Smaller 3 pi construction? [message #93821 is a reply to message #93247]

Thu, 27 May 2021 00:08

stereojan
Messages: 7
Registered: February 2021

Esquire

Hi again

Just received the speaker elements from a store in England, and looking forward to start with the project. But by chance, when inspecting the B&C DE250 compression drivers, I noticed something that seemed a little wierd. When using a flashlight to look inside the driver, it looks like there is some kind of corrosion, or white powder or something.

You guys know what this is, or if it's normal?

/forum/index.php?t=getfile&id=2783&private=0

Attachment: IMG-2701.jpg
(Size: 1.85MB, Downloaded 683 times)

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Re: Smaller 3 pi construction? [message #93822 is a reply to message #93821]

Thu, 27 May 2021 09:19

Wayne Parham
Messages: 18787
Registered: January 2001

Illuminati (33rd Degree)

I can't really see it, but I can tell you that aluminum oxide is white. It's very common to see it on aluminum parts, and it isn't harmful.

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Re: Smaller 3 pi construction? [message #93840 is a reply to message #93822]

Mon, 31 May 2021 07:05

stereojan
Messages: 7
Registered: February 2021

Esquire

Thanks for the reply.

I emailed B&C to check. Got the following reply, so doesnt seem to be any reason to worry:

It is normal.

What you see is a white residue due to the evaporation of the adhesive's solvent used to glue together the phase plug components.

This behavior does not affect absolutely the performance of the phase plug or its reliability, but it concerns only its cosmetic appearance.

Unfortunately, once the phase plug is assembled, the parts covered by the white residues are difficult to reach. Their removing would be too much time consuming, so they are left on the parts.

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Re: Smaller 3 pi construction? [message #93841 is a reply to message #93840]

Mon, 31 May 2021 07:13

stereojan
Messages: 7
Registered: February 2021

Esquire

Another question Smile

Im thinking about moving the bassport to the back of the speaker. Will this affect output significantly, such that I have to compensate for it in the crossover?

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