| Power Transfer into Professional Pi7 [message #49540] |
Mon, 29 May 2006 07:21  |
Tobias
Messages: 19
Registered: May 2009
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Chancellor |
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I currently have the Pi7s with all JBL drivers, and driving them with a tube amp that is hard wired for 4 ohms. I've contacted the manufacture and indicated that the speakers I'm driving should have a relatively flat impedance of 8 ohms. The manufacturer can change the output to 8 ohms, however they claim their amp has been optimized to use the 4 ohm tap. Whether I keep my current amp or change to a tube amp with multiple taps, is there any benefit to using 8 ohm taps vs 4 ohm taps with the Pi7s?
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| Re: Power Transfer into Professional Pi7 [message #49546 is a reply to message #49545] |
Mon, 29 May 2006 18:19  |
Tobias
Messages: 19
Registered: May 2009
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Chancellor |
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I think they do a lot of things very well. Good resolution without being hyper revealing, nice tonal balance, soundstage is wall to wall, the dynamics and impact are exciting, and they seem to do well with both tubes and solid state. I'm still dialing them into my system. I find them sensitive to different things than I am accustomed to, such as noise floor, gain, and things that influence timing. Regarding the output impedance of my tube amp, I don't think I'm getting the same power as before with the output fixed at 4 ohms. Still enough to comfortably cruise at 100 spl if I want to, but not with the same punch. I have some modest 200 watt Outlaw monoblocks on hand that were only average sounding with my last speakers that kick butt with the 7Pi. It seems to me you can get good results without going overboard on amplification with the 7Pi.
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| Re: Power Transfer into Professional Pi7 [message #49547 is a reply to message #49546] |
Tue, 30 May 2006 20:42 |
Russellc
Messages: 397
Registered: May 2009
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Illuminati (1st Degree) |
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I wouldnt worry about it too much. It is not like speaker impedance is that constant. At some frequencies speakers will be above and below their "nominal" impedance. I find in my system that the 8 ohm taps sound best, and I have three sets of speakers I use, One Nominal 4 ohms, one 8 ohms, the other is around 6 ohms. as frequency of the signal the speaker reproduces changes, so does the impedance. I have also seen setups wherein you use a bi wire setup and all four taps are utilized! this araingment is in an issue of positive feedback I have somewhere or the other. the author basically believes that since all the taps are making music and the frequency is constantly varying, why waste any of it? Plus, depending on which taps are used for the highs and lows, you can accentuate or attenuate either the bass or treble. It requires a tube amp with 4,8, and 16 ohm taps and a bi wire setup to impliment, but this example demonstrate the basic principal I am talking about. some speakers vary widely in there impedance depending on what frequency is being put through them. As Wayne has pointed out, most of the Pi speakers have a relitively benign impedance curve, but you can bet it varies beyond 4 to 8 ohms at some point. I have also noticed that some tube amps taps sound better than the other taps, and It also seems to me that this sometimes depends on which tap the feedback is taken from. ( at least in amps that utilize feedback) Russellc
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| Re: Power Transfer into Professional Pi7 [message #49548 is a reply to message #49547] |
Wed, 31 May 2006 04:51 |
Tobias
Messages: 19
Registered: May 2009
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Chancellor |
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Thanks Russell for your reply. Since my amp does not provide other taps to try it's difficult to know whether an 8 ohm output would make that much of a difference. I simply suspect that the power transfer is not as efficient as it was with my previous speakers that were a better match impedance wise. The reason I came to this conclusion is that my tube amp sounded more articulate, punchy, and powerful in the lower frequencies on my old speakers, where as the Outlaw monoblocks did not perform as well even though they are 200 watt SS amps. It seems the opposite is true with the Seven Pi.
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| Re: Power Transfer into Professional Pi7 [message #49634 is a reply to message #49540] |
Sat, 17 June 2006 15:25 |
TomM
Messages: 2
Registered: May 2009
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Esquire |
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All is well again. I found the culprit to be a pair of cathode tubes in my preamp that had weakened. After I replaced these I have all the power, bass, and slam that 140wpc of tube power can dish out. Those Outlaw monos now sound anemic by comparison.
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