| Pi 3 or 4? [message #78603] |
Tue, 10 December 2013 11:15  |
BFP
Messages: 48
Registered: May 2009
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Baron |
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Hi again Wayne. This is probably a common question.
I have been considering the Pi 4. However, the price and availability of JBL2226 woofers in Canada is giving me second thoughts.
I'm wondering if the Pi3 would be a better fit. I can get the 4012 woofers in Canada at a reasonable cost, so parts wise it would be easier and less expensive. My room is about 12.5 x 20 so I don't really need the extra output of the 4. The sensitivity is lower but the response looks like it extends a little further in the bass. Are there any big differences in the 2 models that I'm not seeing? Could you send me the 3Pi plans so I can take a closer look.
Thanks again
Brian
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| Re: Pi 3 or 4? [message #78604 is a reply to message #78603] |
Tue, 10 December 2013 12:17  |
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Wayne Parham
Messages: 18786
Registered: January 2001
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Illuminati (33rd Degree) |
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It is a pretty common question, you're right. And my answer is always that what you're really doing is choosing the midwoofer family more than anything else. Thes two speakers have very similar spectral balance. They are very much alike. This is even more true between the upgraded models. The four π speaker is slightly more efficient though.
Both the fully upgraded three π and the four π models generate deep, full bass, but it definitely rolls off in the lower midbass. I prefer the speakers when used with flanking subs, both for extension and for smoothing. Flanking subs mitigate the self-interference anomalies from reflections from the nearest boundaries, the wall behind the speakers being the most troublesome. Flanking subs also provide additional bass extension.
But that doesn't answer your question about differences. Measurements show little differences, really. There are some minor response differences, but overall, response is similar, that gentle rolloff down low. Midrange up, they're the same. The four π is more efficient though, about 3dB greater sensitivity than the three π speaker. And while distortion is very low in both speakers, the four π model is a little lower, especially at the lowest frequencies. Some would question how much that matters down low, and that's a valid question. But measurements show the four π speaker has slightly lower distortion at the lowest frequencies.
All in all, I think the biggest difference is probably the efficiency though. The speakers sound very much the same, both offer the same uniform directivity, the same pristine wavefront launch from the same waveguide/horn, both have a slightly overdamped alignment that is immune to parameter shifts and has gradual rolloff. So they're very similar in most aspects, with just a slight difference in efficiency between the two models.
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| Re: Pi 3 or 4? [message #78933 is a reply to message #78932] |
Thu, 09 January 2014 10:40 |
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Wayne Parham
Messages: 18786
Registered: January 2001
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Illuminati (33rd Degree) |
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I really like the look of Allen head fasteners, especially those with a button (rounded) top. I almost always use those for my best builds.
As for T-Nuts, do be sure to get a good quality part. Some are better than others, and these T-Nuts will be in your speakers for a lifetime. They won't probably be opened and closed a lot, but still, we want those fasteners to last. You don't want to ever have to drill one out.
What I've done (several times) when testing a new fastener is to use a few sacrificial parts to see how they hold up. I wish I could just count on one brand being always available, but it seems like sometimes, vendors change suppliers and I have to inspect them again. So what I do is to get a handful of screws and a handful of nuts and I put them through several tighten/release cycles. What I'm essentially doing is testing their yield, seeing how they act when they go plastic. It's not what my mechanical engineering friends would call a good stress test, but it is good enough for me to see if the threads deform easily or not. Some brands of T-Nuts are definitely better than others; Some will take several cycles before deforming threads, others are like tighten-to-yield parts after a single cycle at a mere 15 foot pounds.
On a similar subject, when you install them in your cabinets - which is hopefully a permanent installation - be sure to install them gently. The proceedure I use and suggest for you is in the link below.
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