| 3 Pi - Could it work for me? [message #62526] |
Wed, 05 May 2010 22:06  |
Docere
Messages: 11
Registered: July 2009
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Chancellor |
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It has been a while... but I can finally foresee a time when I can make a new pair of speakers happen. I have eliminated "wide/full-range" drivers and Altec duplex units based on their various compromises and apparent challenges to getting them to present music in a way I would like.
Background
The 3 Pi with AE and B&C drivers would likely fit my needs and constraints, but I would like to confirm a few things. My amp will be a ~ 3W to 6W SET amp (with healthy overload behaviour). I have attached a layout of the room (red boxes = speakers, blue blob = listening position). The room is room 12.5(w) x 18.7(l) x 8.8 (h) feet. I will be listening across the short dimension at ~ 8 to 9 feet, with the speakers ~ 7 feet apart (driver ctr to driver ctr); speakers will be against the front wall and at least 3.5 feet from side walls. There are room openings along the front wall (long dimension) starting at the outer sides of each speaker, so the front wall does not provide a genuine quarter-space (I think?!) loading.
I generally listen at low to moderate levels, with occasional loud listening being at a volume where I can still hear someone talk with their voice a little raised; rarely louder. I listen to a wide range of music, but not so much heavy orchestral/opera or metal. Quite a lot of ambient, alt-folk, melodic indie, down-tempo; some jazz and alt-country... I like melody, foot-tapping, effortless flow and listening with friends while forgetting about hi-fi. Speaker size (within reason) is not really an issue as my long-term GF loves music and is supportive; she likes speakers that look functional and even prefers wide baffles to dainty narrow ones (though she thinks tubes are a little phallic especially 845s and 211s)!
Questions
So, given the room and amp power constraints, could the 3 Pi work well, or would I be better opting for the 4 Pi with 2226? Any suggestions for how I could get the most out of such a room/make the Pi spks more useable, eg. move the speakers closer together and or use flanking subs subs distributed around the room would be tougher, would be appreciated.
Are the impedance and phase graphs of the 3 and 4 Pi available for viewing this would help me determine suitability for a SET amp? That said, if you say it will work I will trust your opinion. Also, would I need to alter slightly the damping of the mid-bass driver to account for the high-ish output impedance of the SET amp?
Finally, I would love the option of being able to use those beautiful Pi wood horns at some later stage. How difficult is it to achieve the required distances between driver centres how precise do they need to be? Would it be practical to build the speaker with a separate Eminence horn module and then swap in the wood horns at some later date?
Apologies for asking so many questions Wayne, you are very generous with your time, but short answers are fine if you are busy. Here's hoping that a Pi speaker will be in my house for the next 10 years or so (or more!).
Cheers
Raymond
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| Re: 3 Pi - Could it work for me? [message #62528 is a reply to message #62526] |
Wed, 05 May 2010 22:59  |
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Wayne Parham
Messages: 18787
Registered: January 2001
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Illuminati (33rd Degree) |
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I run a 10 watt Audio Note amp for my main home stereo and home theater. It's plenty for either model - three π or four π - but do remember the four π is 3dB louder. This isn't night and day, but it is noticeable. With 10 watts, I'd say either will play louder than most middle aged adults want or need. With 5 watts, you might just be at full volume sometimes, but you'll definitely not be able to talk over the stereo at that level.
Your room layout is similar to mine with one exception. I think I have a little more room to the sides and places to put subs. You'll want to experiment with subs placement to find positions that simultaneously work with the decor and smooth room modes well. Shouldn't be too hard though, especially with two or more subs. The mains go pretty deep too, so with a couple subs you have four bass sound sources.
The impedance of either model is very SET-friendly. There's a set of charts for the four π at the link below. I've been meaning to do the same thing for all my models rather than having a hodge-podge of measurements, mostly made during development. But for now, just take my word that the three π impedance curve is also tube-friendly. You can see its response in the "Vertical Nulls" video in the crossover optimization thread:The spacing between midwoofer and tweeter is precise, naturally, to position the forward lobe and vertical nulls. The electro-mechanical and directional characteristics of the drivers and horn, their positions and the electrical phase of the crossover all combine to set the pattern. You can move them only slightly without upsetting the pattern.
Fortunately, the wavelength of the overlap region isn't unmanageably small, approximately 10", making 2.5" be 1/4λ. Because of that, there is a little bit of wiggle room, and that allows freedom to surface mount or route the baffles for flush fit horns and midwoofers without a complete redesign. But I wouldn't be comfortable with much more than that.
If you want to put the horns outboard, then move the woofer up in the box to keep the physical spacing between drivers the same. Don't shift the fore/aft relationship, keep it as close as possible to stock, and don't make the woofer and tweeter more distant vertically either. You can put the H290 in a small attractive box to start with and then upgrade to a wood horn later.
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