Home » Sponsored » Pi Speakers » Three 4Pi's in Basic Black for Home Theater Build Thread
Re: Three 4Pi's in Basic Black for Home Theater Build Thread [message #64013 is a reply to message #64009] Wed, 08 September 2010 13:16 Go to previous messageGo to next message
morphlaugh is currently offline  morphlaugh
Messages: 2
Registered: September 2010
Location: Colorado
Esquire
Wayne,

I think timbre matching the surrounds is quite important. Although I agree that most movies simply use the surrounds for ambiance, there are some movies where for example, a ship will fly overhead and it'll come from the surrounds and fly to the LCR's when coming onscreen.

I've just found this website and am still trying to find all of the data I can from these forums about the 2pi and 4pi loudspeakers you've designed. I'm thinking of doing what Big has done here and build myself three 4pi for the LCRs of my work-in-progress theater, but two things are holding me back:

1) I am afraid of trying to timbre match to the surrounds. I don't have horn surrounds, and horns definitely add a fair bit of presence to a speaker, in my experience. What I have now are some ported tweet-mids for my surrounds, and I am worried I won't be able to properly adjust my surrounds into the mix. You suggested the 2pi's... what are they? Are they a horn/ported woofer configuration?

2) I haven't had the pleasure of listening to the 4pi's yet... I have just been reading the glowing reviews of how great they sound. Do you ever take them on the road, and more specifically, to Colorado? Wink

Could I get a copy of the 2pi and 4pi designs/specs? I'd love to look em over and see what's involved and what trade-offs I'd be making if I selected the cheaper or more expensive components.

Thanks!
Re: Three 4Pi's in Basic Black for Home Theater Build Thread [message #64014 is a reply to message #64013] Wed, 08 September 2010 14:46 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18670
Registered: January 2001
Illuminati (33rd Degree)

I would agree generally, that to match surrounds and mains at least in terms of spectral balance is important. In fact, there was a time that I recommended all five speakers in a five channel system should be the same. However, I have backed off this, because my opinion has changed. I now think the fronts should be the same, but that surrounds need not be.

In fact, I think it is probably better that the surrounds not be the same as the mains, at least in terms of directivity. I prefer the fronts to be somewhat directional but the surrounds to have a wider pattern. They are primarily for ambiance. Even though sound effects in the surrounds are occasionally "given focus", it is rare and only for an instant, a transition to the front or as a quick movement away. Their main purpose is ambiance.

I don't think the surrounds should be radically different than the mains though. The spectral balance should be pretty similar. This is important for the times when a particular sound pans from fronts to surrounds or vice versa, like you said, as a fly-by or an approach or something. But even then, we're talking about a sound coming into focus or going out of focus, so a sonic transition is made, just as the visual transition is made. The effect is realistic, provided the speakers are not completely different.

I did some little subjective experiments before coming to this conclusion. I tried various speakers, even including some that were considerably different than the mains. I used bookshelf speakers, unbaffled speakers, car speakers and even some with tweeters removed to see what sonic significance there was in surrounds. I could tell when surrounds lacked a major portion of the spectrum, like if the treble was completely gone. Or if a speaker couldn't "keep up" dynamically, bottomed out or broke up at loud passages, obviously, I could hear that. But as long as the spectral balance was similar and there was sufficient dynamic range, the illusion of realism was maintained very well. That's why I often suggest the smaller one π or two π speakers as surrounds. They are a good spectral match with three π or four π mains, and they have plenty of dynamic range.

Re: Three 4Pi's in Basic Black for Home Theater Build Thread [message #65984 is a reply to message #64014] Fri, 04 February 2011 19:51 Go to previous messageGo to next message
BigmouthinDC is currently offline  BigmouthinDC
Messages: 41
Registered: February 2010
Location: No VA
Baron
It has been some time since I posted any information in this thread but this week I have been playing with a new measurement system I purchased to test my speakers, some planned sub-woofers, room set-up, and the overall acoustical design of my space. I picked up the OmniMic from Parts Express.

My thoughts relative to the Pi's are to do some of my own measurements of the effect of the SMX screen in the audio path and the impact of adding some foam to the waveguide.

To start this is my first pass at measuring one of the 4Pi's in place in the wall with the microphone about 3 ft away. This is with the screen in place:

http://www.PiSpeakers.com/DIY/BigmouthinDC/BigmouthinDC_4Pi_HomeTheater_31_InRoomMeasurement.jpg

I hope Wayne doesn't mind but I'm copying in one of his published graphs:

http://www.pispeakers.com/Measurements/fourPi_response.gif

I'm actually pretty happy that what I built looks to me about what the Master designed. I wonder about that sawtooth uptick in the higher frequencies that I can no longer hear. Maybe some screen interference issues.

When I finish building some new sub-woofers I'll be taking down the screen and at that point I can measure without the screen fabric.
icon14.gif  Re: Three 4Pi's in Basic Black for Home Theater Build Thread [message #65989 is a reply to message #65984] Sat, 05 February 2011 10:04 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18670
Registered: January 2001
Illuminati (33rd Degree)

Thanks for reporting back. It's always nice to get feedback from people, especially when they've done as much work as you have.

I'm impressed to see this measurement through the screen. It's pretty much the same chart as you get from an anechoic measurement. There is usually more ripple than that when you add a grille or screen.

Your system looks great! All you lack is getting the subs added in.

Great job!

Re: Three 4Pi's in Basic Black for Home Theater Build Thread [message #74150 is a reply to message #65989] Wed, 17 October 2012 04:15 Go to previous message
NWCgrad is currently offline  NWCgrad
Messages: 143
Registered: March 2010
Location: Frederick, United States ...
Master
Big,

Did you build your subwoofers? If so, what did you go with. I am about half way through your HT thread on AVSforum, simply awesome work! I followed the link from there to re-visit your speaker build.

This thread was a major inspiration for my building the 4 Pi's.


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