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Multi-Way Conventional loudspeakers with crossovers

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Old 21st July 2010, 05:18 AM   #6741
mige0 is offline mige0  Austria
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First steps have been undertaken – and already presented - no ?
There is some more fun to have about correction of CMP systems - stay tuned ...


Michael
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Old 21st July 2010, 06:07 AM   #6742
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Is there a big idea here, about sound reproduction in general? Something like, the dipole concept has a problem that negates any/all benefits, so forget that and stick with ___? Or, open baffles have a feature that needs to be addressed with ___? Or?
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Old 21st July 2010, 08:51 AM   #6743
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Is there a big idea here, about sound reproduction in general? Something like, the dipole concept has a problem that negates any/all benefits, so forget that and stick with ___? Or, open baffles have a feature that needs to be addressed with ___? Or?
I think the important thing is not to get all religious about one approach or another - and I confess I am as bad as anyone when it comes to that. What's called for is more rigor in thoroughly analyzing what's going with a loudspeakers, regardless of topology - open baffle, transitional, closed-box, horn loading, what have you.

Several years ago I got in big trouble reviewing Dr. Geddes' book - enough so that I withdrew the review, rather than deal with all the hostility. But my basic point is simple: loudspeaker design still has a long way to go. We have not arrived at the fabled "City On The Hill", and there is much more to be discovered. And regardless of the reaction on various Internet forums, I still feel Dr. Geddes' book has made a significant contribution to the art.

I am very appreciative of all the posters who know way more than I do - Dr. Geddes, John K, Michael, Bjorn Kolbrek, JMMLC, and many others. All of these postings advance the art - sorry, folks, this ain't a construction project, but more of a round-table discussion amongst the most talented people in the business.

What I hope has become evident to the readers is that all approaches have advantages and disadvantages, and the way these are arranged depends on the priorities of the loudspeaker designer. What is given up in one area is gained in another - and this has nothing to do with brand-name awareness or the price of the loudspeaker.

Last edited by Lynn Olson; 21st July 2010 at 08:58 AM.
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Old 21st July 2010, 11:30 AM   #6744
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Originally Posted by gedlee View Post
John

A question for you, or anyone else.

When I looked at the Orion measurements it was obvious how well it controlled the directivity in the 200 - 500 Hz range, where I am not able to effect much control. Hopefully it is not a coincidence that this is precisely the region where I think the Orion shines. In my book I showed how a rear facing driver could be used to control the directivity in precisely this range while going away at LFs to yield a more efficient monopole. It turns out that this can be done passively, albeit not simply (passive attracts me for obvious reasons). I am going to try this and wondered if you, or anyone else, has actually done this as well and what your experience was (technically please!). This would not be too hard to impliment and may be an audible improvement. (There is no point in not disclosing this since its already public domain anyways.)
Actually I have done something like that. A few years ago I build a little speaker for a DIY gathering called the Bird House. Imagine a speaker enclosure that looked like a steep roofed bird house, as shown below.

Click the image to open in full size.

The tweeter and midrange were dipole format. The woofer was a single woofer firing down as a monopole. The crossover between mid and woofer was an Linkwitz/Riley 2nd order affair. As you can see at my web site such an arrangement yields a smooth transition from dipole through a cardioid at the crossover point, to monopole at low frequency:

Click the image to open in full size.

This figure is for an LR4 crossover but the LR2 behaves in the same manor. It just extend the transition region over a wider frequency range.

It is also the philosophy used in the design of my NaO Mini and applies to the NaO II as well when the woofers are used in sealed box format.

The idea is that the dipole response retains good CD behavior over its useful range. The transition to cardioid around the crossover to the woofer helps control the reflection of the wall behind the speaker in the upper bass lower midrange region. Finally the response at low frequency reverts to a monopole in the sparsely populated modal region.

The Bird House crossover was at 200 Hz. The NaO speakers cross in the 120-130 Hz. My new speaker, the Note, will also have an option to build it in this format using a ported woofer system. It will also include the option for dipole and U-frame cardioid woofer configurations. I am doing it that way so the builder can decide what woofer format he wants to go with.

The problem with doing this passively is that you can not take advantage of the frequency dependent sensitivity of the dipole midrange . As you know, my designed are hybrid with a passive crossover used on the panel and an active crossover between the woofer and panel. The active crossover also contains any needed equalization for the woofer and the dipole midrange.
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Old 21st July 2010, 11:43 AM   #6745
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Originally Posted by mige0 View Post

You missed to clearly point out that its even an approximation *below* dipole peak, and you also missed to point out that this is so because OB simply is a CMP system (if you have an other term from "ancient" researchers in that topic - no problem for me ).


Michael
Let's not get more confused here. If we are talking about the on axis response and radiation pattern of an acoustic doublet or dipole it has noting to do with CMP, as you call it. There is no requirement that the sources of the doublet be MP. MP is a separate issure.
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Old 21st July 2010, 11:53 AM   #6746
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What I hope has become evident to the readers is that all approaches have advantages and disadvantages, and the way these are arranged depends on the priorities of the loudspeaker designer. What is given up in one area is gained in another - and this has nothing to do with brand-name awareness or the price of the loudspeaker.
I also think that we often forget that the real goal is listening to music and making an emotional connection to it. With the right music that can be accomplished with an iPod. The obsession with Hi Fi and high quality reproduction is just that, an obsession and in no way guarantees any greater emotional response will result. I, for one, enjoy listening to music far more when driving than just sitting at home listening.
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Old 21st July 2010, 12:50 PM   #6747
gedlee is offline gedlee  United States
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Actually I have done something like that.
John, neither of the speakers in my setup are OB, so it seems to me that it is quite different. A cardiod is created by having the rear facing driver out of phase with the front and at a lower volume velocity. By using a 6 dB HP filter on the rear one (in adition to the LP crossover at 800-1 kHz), the polar transitions from cardiod down to monopole at LFs. I think that this can be done without frequency dependent gain required for the woofers - hence passively.
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Old 21st July 2010, 12:55 PM   #6748
gedlee is offline gedlee  United States
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I, for one, enjoy listening to music far more when driving than just sitting at home listening.
Curious (perhaps typical!), I am the exact opposite. I do not connect as much to music in a car, too many distractions, or even an airplane (of which I spend way too much time in!) as I do listening late at night in the quiet and solitude of my theater. In that case I am almost transported away and get completely engulfed in the effect. Cars and headphones just don't get there, for me, although I still like the music.

But I think that your point is, or hope that I understand, that the music and performance are quite a seperate things from the playback and one can make an "emotional connection" to the music quite independently of the sound system.

Last edited by gedlee; 21st July 2010 at 12:57 PM.
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Old 21st July 2010, 01:34 PM   #6749
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Curious (perhaps typical!), I am the exact opposite. I do not connect as much to music in a car, too many distractions, or even an airplane (of which I spend way too much time in!) as I do listening late at night in the quiet and solitude of my theater. In that case I am almost transported away and get completely engulfed in the effect. Cars and headphones just don't get there, for me, although I still like the music.

But I think that your point is, or hope that I understand, that the music and performance are quite a seperate things from the playback and one can make an "emotional connection" to the music quite independently of the sound system.
It has to be the right music. I'm not driving the back roads of northern New England at 8 or 9/10 listening to Mozart. If I'm listen to Mozart I'm probably laying down on the couch, soon to be asleep. Motzart might go better with a hot air ballon ride. Something that everyone should try, the ballon ride that is.

But (about to commit heresy) regardless of the playback quality, as soon as you put a vidio screen between the speakers there is a hole new perspective on music reproduction (event reproduction?). I'll give you an example. I have a DVD of a live perfromance that everyone who has watched it raves about the performance. Take that DVD and turn off the video and it's almost un-listenable. I guess the point is that visual stimulation take precedent over aural stimulation.
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Old 21st July 2010, 01:43 PM   #6750
gedlee is offline gedlee  United States
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as soon as you put a vidio screen between the speakers there is a hole new perspective on music reproduction (event reproduction?). I'll give you an example. I have a DVD of a live perfromance that everyone who has watched it raves about the performance. Take that DVD and turn off the video and it's almost un-listenable. I guess the point is that visual stimulation take precedent over aural stimulation.
THIS I agree with, mostly. The video adds another dimension, that is unmistakable, but I tend to agree with George Lucas here, who said that sound is 1/2 of the movie experience. Turn off the sound on that DVD and it is even less appealing than the sound without the video.

But I have found that I can't take video at times. Video is very intense and requires much more "nueral energy" than just audio. I can almost always just listen to music, but not always listen and watch.
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