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Re: Favorite flavors [message #17456 is a reply to message #17453] Sun, 23 January 2005 14:18 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
Excellent explanation. Now I understand the benefit of off-axis. The concept of reflected energy constituting a similar frequency response to the on axis response nails it for me. Now how to explain the effect of nulls and standing waves and how those artifacts impact on off-axis and reflected sound. Thanks Wayne; good stuff.
The best part of debate is someone will ask or discuss the questions I don't know enough to ask.

Re: Favorite flavors [message #17457 is a reply to message #17456] Sun, 23 January 2005 14:37 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18689
Registered: January 2001
Illuminati (33rd Degree)
Standing waves, interference and the nulls they cause are a related but different issue. Here are some good papers that describe them:



Re: amazing clarity... [message #17460 is a reply to message #17437] Sun, 23 January 2005 18:51 Go to previous messageGo to next message
Bill Martinelli is currently offline  Bill Martinelli
Messages: 677
Registered: May 2009
Illuminati (1st Degree)
yeah, I'd have the same house house Bill Gates has If I were him as well. Oh, and put my bid in for the Astro Dome for my garage. I want to be able to open up the roof on sunny days while I pick out what I'll be driving for the day.

Re: Favorite flavors [message #17461 is a reply to message #17454] Sun, 23 January 2005 20:29 Go to previous messageGo to next message
Earl Geddes is currently offline  Earl Geddes
Messages: 220
Registered: May 2009
Master
Wayne

You are falling into the common trap of assuming that waves follow the walls of a horn simply because you want them to. They don't. For instance at frequencies where the wavelength is comparable to the horn mouth the directivity is substantially smaller than the wall angles. It is only when the mouth is much larger than a wavelength that the device even begins to get CD. Thus for your mid horn to be CD it would have to be gigantic - about 8 ft. across at 250 Hz. Then this places the HF horn many wavelengths away - unless they are coaxial, which has a whole other set of problems - and there will be a great deal of polar lobing at 1.6 kHz - not CD. SO from where I sit this design is anything but CD.

Unless you have data to support your contentions I will have to stick with my opinion that your hypothesis is unlikely.

Mine claims, on the other hand, have substantial supporting measurements which I freely show on my web site.

Sorry to disagree with you like this, but we don't see this issue eye to eye.


Re: Favorite flavors [message #17462 is a reply to message #17461] Sun, 23 January 2005 20:58 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18689
Registered: January 2001
Illuminati (33rd Degree)
OK, Earl. Perhaps we don't see eye to eye. Or maybe there's more to it than that.

There are seven π cornerhorn response measurements in the link on my last post, both on-axis and off axis. Beyond what is shown there, I don't see the need for additional measurements that prove π/2 radiation defined by a room corner. It is a radiating pattern definition, not a hypothesis or a speculation about an acoustic device. I really think it's needlessly combative to even bring this matter into question.

It is easy to hear the difference in output from corner loading. It's immediately noticeable. The DI formula illustrates the fact that there is increased power due to directionality. That wouldn't be the case if the corner weren't providing directionality. As you know, the equation was written by C.T. Molloy to quantify the directivity index.

I imagine the data on your website is probably specific to your speakers, and from your position here, I don't think it has anything to do with using room corners. I guess that means your arguments must be based on intellectual skepticism. Maybe it's best to limit your comments to a description of your thoughts and ideas. Or maybe you can substantiate your remarks with measurements that are relevant to this discussion. Don't hesitate to use formulas and include technical details. I'll do the same for you.

Let me ask you:

  • Do you believe that a horn's behavior is modified by the radiating space it is used in? Specifically, do you think a baffle mounted horn or one used in quarter-space or eighth-space can be made smaller than one used in freespace?

  • Do you agree that a room corner produces 9dB DI over omnidirectional radiation?

  • Since those things are accepted by most everyone in the industry, what measurements or other data might you have that suggest otherwise?

Re: Favorite flavors [message #17463 is a reply to message #17462] Sun, 23 January 2005 22:04 Go to previous messageGo to next message
Earl Geddes is currently offline  Earl Geddes
Messages: 220
Registered: May 2009
Master
Since you won't accept my measurements why would you accept my arguments. I think that I'll bow out at this point.

Re: Favorite flavors [message #17464 is a reply to message #17463] Sun, 23 January 2005 22:23 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18689
Registered: January 2001
Illuminati (33rd Degree)
You're a smart guy Earl, and I think that if you have a valid argument you can probably discuss it intelligently.

So I ask you again, what do you attribute the 9dB DI power increase from eighth-space radiation if it isn't from directionality?

If you agree that a room's corner has DI ≈ 9, then maybe you'll consider taking advantage of that, combined with high frequency horns having DI ≈ 9 to provide constant directivity across the audio band.

Re: Favorite flavors [message #17465 is a reply to message #17442] Mon, 24 January 2005 04:13 Go to previous messageGo to next message
Rainer is currently offline  Rainer
Messages: 4
Registered: May 2009
Esquire
"I want the power response to rise at lower frequencies in my rooms because I design them to have a lot of low frequency absorption. The increased power response at LF is exactly compensated for by the increased absorption."

What about typical rooms that don't have your special absorption? Won't room gain add to abnormally boost the bass? How does that jive with "the increased power response at LF" of your speakers?

Re: Favorite flavors [message #17466 is a reply to message #17464] Mon, 24 January 2005 07:08 Go to previous messageGo to next message
Manualblock is currently offline  Manualblock
Messages: 4973
Registered: May 2009
Illuminati (13th Degree)
Wayne; you scared him away. What is with you engineers; should be more like Lawyers. This was such a good debate too. What happens at NASA; do they walk out when they disagree? Leave the astronauts floating?

Re: Favorite flavors [message #17468 is a reply to message #17465] Mon, 24 January 2005 09:14 Go to previous messageGo to previous message
Earl Geddes is currently offline  Earl Geddes
Messages: 220
Registered: May 2009
Master
In the kind of room that you describe the bass from my speakers and any other speaker, will not sound very good. It will be boomy and resonant. I think that we are talking ideals here, not "How does one design speakers for bad rooms".

And I continue to contend that it is inappropriate to talk about directivity or power response or any concept that requires thatthe space be acoustically difuse at LF (i.e. below about 200 Hz.) We ahve talked about this problem and the solution is lots of damping and several woofers. Directivity is not relavent.


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