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Pi 7 frequency response [message #50972]

Tue, 17 April 2007 21:14

Tim Barnes
Messages: 46
Registered: May 2009

Baron

Hi Wayne:
I was browsing your measurements folder and was a little surprised by the way the slope of the Pi Seven declines as frequency increases, and by the rapid rolloff of the tweeter at about 15KHz.

Can you explain the reasons? I'm just trying to understand the likely sound prior to making the commitment to build, and I have been under the impression that generally speaking one aims for a frequency response that is roughly flat to 20KHz, and that some people are even aiming for much higher frequencies with supertweeters.

Thanks,
tim

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Re: Pi 7 frequency response [message #50973 is a reply to message #50972]

Tue, 17 April 2007 22:26

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

That's just the nature of compression horns. They don't get much above 16kHz or so. Some people add super-tweeters, others don't feel the need. I personally would prefer a bit more on the top end, but not at the expense of integration. It's hard to seamlessly match a super-tweeter because wavelengths are so short at the crossover point.

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Re: Pi 7 frequency response [message #50975 is a reply to message #50973]

Tue, 17 April 2007 22:35

Tim Barnes
Messages: 46
Registered: May 2009

Baron

OK, I understand the top end piece. What about the more gradual slope from 500Hz to 15KHz? Is that an intended balance, or just something that's too small to notice in real life?

Sorry about the neophyte questions. I'm old enough that my top end hearing is probably done for - not sure if that means I need more or less from the high end of the speaker...

tim

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Re: Pi 7 frequency response [message #50976 is a reply to message #50975]

Tue, 17 April 2007 23:30

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

You're right, there's an overall trend, sloping downward about 5dB over the audio band. It's within a +/-6dB window up to the top octave, but there's a general slight sloping downward. I think it's a very natural sound.

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Re: Pi 7 frequency response [message #50977 is a reply to message #50976]

Wed, 18 April 2007 08:16

Tim Barnes
Messages: 46
Registered: May 2009

Baron

Thank you.
tim

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Re: Pi 7 frequency response [message #50978 is a reply to message #50977]

Wed, 18 April 2007 08:50

Matts
Messages: 359
Registered: May 2009

Grand Master

After seeing all the 20K high frequency claims over the years, I was a little worried about this when I built my Stage 4's, but it hasn't been an issue at all. I thought I might add a supertweeter at some point, but have never felt the need. In fact, now when I listen to some of the speakers with them, it's a litttle annoying.

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Re: Pi 7 frequency response [message #50981 is a reply to message #50978]

Thu, 19 April 2007 09:07

Tim Barnes
Messages: 46
Registered: May 2009

Baron

That's good to hear. I find it difficult to judge a design without hearing it - I just don't have enough experience.

Thanks for weighing in. Have you heard the corner horns? Any other inputs about the sound and qualities of your speakers?

tim

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Re: Pi 7 frequency response - HF [message #50989 is a reply to message #50976]

Mon, 23 April 2007 09:31

dB
Messages: 234
Registered: May 2009

Master

It all depends in the horn being used. For that fact, to have more high frequencies and if I was Tim, I would use SELENIUM D210Ti driver instead of Eminence PSD2002. Again, the listening window is so narrow at 16KHz that it's only 15º to the left and 15º to the right from the speaker (sweet-spot). Another way is to go with a speaker including the Vifa tweeter, flat to 20KHz and a real Hi-Fi home-runner with a large listening window both vertical and horizontal.
Cheers.

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Re: Pi 7 frequency response - HF [message #50990 is a reply to message #50989]

Mon, 23 April 2007 10:44

Wayne Parham
Messages: 18791
Registered: January 2001

Illuminati (33rd Degree)

Dome tweeters actually have pretty narrow radiation patterns at high frequency. Intuitively, it looks like they would radiate an omnidirectional pattern but they exhibit collapsing DI according to radiator size.

LMS measurements show the response of the new π wood tweeter horn is virtually the same off-axis within a 90° x 40° angle as on-axis, even at HF above 10kHz. Response above 5kHz falls at vertical angles larger than that. I didn't measure other horns to see how they compare.

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