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Pi 2 Plans [message #53177] Fri, 06 February 2009 11:08 Go to next message
Steven Cone is currently offline  Steven Cone
Messages: 7
Registered: May 2009
Esquire
Wayne,

Would you please send me the plans for the Pi 2 speakers, both the bookshelf and the tower versions?

Thank you!



You've got mail! [message #53178 is a reply to message #53177] Fri, 06 February 2009 11:37 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18671
Registered: January 2001
Illuminati (33rd Degree)


Re: You've got mail! [message #53181 is a reply to message #53178] Fri, 06 February 2009 16:27 Go to previous messageGo to next message
Steven Cone is currently offline  Steven Cone
Messages: 7
Registered: May 2009
Esquire
Thanks!

Crossover Question [message #53183 is a reply to message #53178] Sat, 07 February 2009 01:25 Go to previous messageGo to next message
Steven Cone is currently offline  Steven Cone
Messages: 7
Registered: May 2009
Esquire
For the resistor that is across the Pi 2 tweeter, what Watt rating would you suggest? 10? 40? 100? I may run these fairly loud.

Thanks!

Re: Crossover Question [message #53184 is a reply to message #53183] Sat, 07 February 2009 10:22 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18671
Registered: January 2001
Illuminati (33rd Degree)

Use a 10 watt non-inductive resistor.


Re: Crossover Question [message #53185 is a reply to message #53183] Sat, 07 February 2009 11:02 Go to previous messageGo to next message
dB is currently offline  dB
Messages: 234
Registered: May 2009
Master
Steven Cone hi,
I dare to say, after Wayne has answered your question, that he mentions this fact on his paper "Speaker motors and passive crossover filters" on page 74.

Steven, what are the ohmic values for R1 and R2?

Re: Crossover Question [message #53187 is a reply to message #53185] Sat, 07 February 2009 11:40 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18671
Registered: January 2001
Illuminati (33rd Degree)

You're right, power handling is discussed at the end of the Speaker Crossover document. It is really geared more for the crossovers used in the larger speakers though, the ones with CD horns. The speakers Steven is talking about use a soft-dome tweeter and a simple first-order crossover. The resistor is used for damping only.


Re: Crossover Question [message #53189 is a reply to message #53185] Sat, 07 February 2009 12:16 Go to previous messageGo to next message
Steven Cone is currently offline  Steven Cone
Messages: 7
Registered: May 2009
Esquire
Thanks for your reply.

OK, I looked at the Speaker Motors document, and I think I found the answer I was looking for; however, as Wayne indicates the crossover I'm working with is not exactly the same as the ones in the doc.

Using one of the Pi 3-7 crossovers, 300 W RMS put 100 W RMS across the tweeter resistor. But, practically speaking, 40-50 W power rating for the resistor has been found to be sufficient, because of the usual balance of energy in program content.

In the Pi 2 crossover, however, there is only a single capacitor leading to a tweeter resistor. No inductor.

If that does not mess up the calculations, then I could run four ten-watt resistors in series to make the required power dissipation. Right? I would never plan to run more than 300 W RMS into the speakers--probably quite a bit less.

Thanks again. Just trying not to set my speakers/house on fire....

Thanks [message #53190 is a reply to message #53187] Sat, 07 February 2009 12:17 Go to previous messageGo to next message
Steven Cone is currently offline  Steven Cone
Messages: 7
Registered: May 2009
Esquire
Thanks, I'll look at the document.

Re: Crossover Question [message #53192 is a reply to message #53189] Sat, 07 February 2009 13:03 Go to previous messageGo to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18671
Registered: January 2001
Illuminati (33rd Degree)

It never hurts to add power handling by adding more components in the way you've described. So I wouldn't try to talk you out of it. It adds protection in cases where higher-than-normal spectral density is sent to the parts in question. It reduces thermal shifts, distributes the heat among more components and reduces the chance of failure. Reducing heat is always good. That's why my horn tweeter crossovers use R1a, b, c and d components where almost everyone else uses just one resistor.

That said, I've never run into trouble on the one π and two π speakers using a single 10 watt damper resistor. They're only designed for 100 watts total, and most of this goes to the midwoofer.


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