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LSAF 2008 - Show Coverage, Seminar Recordings, Slideshows and Handouts [message #4835] Wed, 07 May 2008 21:57 Go to next message
Wayne Parham is currently online  Wayne Parham
Messages: 18670
Registered: January 2001
Illuminati (33rd Degree)

I've setup a page that has links to the audio recordings of the seminars at LSAF 2008. We're planning to upload the slideshow presentations too, as people have time to send them to me. And we'll also add links to write-ups, as they filter in.

If you see comments about LSAF around the internet, please link them here. I'm eager to see what people are saying. There was plenty of good buzz at the show but I haven't seen that translated to written comments yet. So please post your impressions, and if you see comments on other sites, link them here as well.

There's a similar page for last year's LSAF, so I'll link it here in case any of you missed it:



Re: LSAF 2008 - Show Coverage, Seminar Recordings, Slideshows and Handouts [message #4836 is a reply to message #4835] Wed, 07 May 2008 23:41 Go to previous messageGo to next message
Shane is currently offline  Shane
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Registered: May 2009
Illuminati (3rd Degree)
My impressions were that all the rooms sounded good, but the one that really blew me away was Duke's Audio Kinesis room. I walked in and he was playing some sort of very relaxing classical type music (duke if you remember what that was could you post it?) that nobody wanted to take out. The Dream Makers were being pushed by the NTV amps. The kicker besides the sound being just fantastic and completely enveloping in the room was that the amps were being controlled by a tiny little pre running a single 12AU7 that wasn't even cased up. I asked Duke what the design for the pre was, and he just laughed and said that I could never find out, only that it started as a Bottlehead Foreplay he thought.

All of the people were so friendly as well. It was nice to sit and listen to them explain the ins and outs of their particular setup and what it's strength's and weaknesses were. And you could ask any question and they would answer it to the best of their knowledge (which was sometimes quite expansive). Just an all around great group of people.

Re: LSAF 2008 - Show Coverage, Seminar Recordings, Slideshows and Handouts [message #4837 is a reply to message #4836] Thu, 08 May 2008 00:52 Go to previous messageGo to next message
Keith is currently offline  Keith
Messages: 3
Registered: May 2009
Esquire
No room sounded bad given the acoustics. I'd say each room sounded good and so we're talking degrees of goodness here. ../emoticons/smiley.gif

The winner for wow factor had to go to the Maxxhorn room. Defintely the coolest looking rig there. It sounded good but wasn't my favorite sounding system. The Audiokinesis speakers sounded good but they were a little on the boomy side for my tastes. Pi Speakers were natural with clean midrange and tight bass. They were my show favorites. The Audio Note system was nice but I didn't get a chance to hear it with music that I liked. I should have stayed longer to give another chance but the room was full and I thought I'd come back. Jumping Cactus had good tone and was definitely a contender. John Bush had a nice sound as did Hawthorne. I would give open baffle speakers a listen if you haven't before.

Re: LSAF 2008 - Show Coverage, Seminar Recordings, Slideshows and Handouts [message #4842 is a reply to message #4837] Fri, 09 May 2008 12:19 Go to previous messageGo to next message
Wayne Parham is currently online  Wayne Parham
Messages: 18670
Registered: January 2001
Illuminati (33rd Degree)

Don't leave out Skip Pack and Bob Brines. They generally have very good sounding systems. I regret that I didn't get a chance to stop by and listen. Too much to do!

About Duke's speakers, I was able to listen briefly and what I heard sounded very good. The source material may have been responsible for a perceived "boominess" when you were there. Or maybe it was the room, I don't know. But I thought it sounded great in his room when I was there.

To be honest, there is very little difference between our design philosophies. We're both concerned with creating a uniform reverberent field, and we both use constant or uniformly collapsing directivity to accomplish it. Our speakers are DI matched at the crossover point, as are other similar designs like Geddes Summa loudspeakers.

I remember when I first heard the Summas in Duke's room at GPAF 2005. I thought they sounded exactly like my four π loudspeakers. In most ways, they are nearly identical. They're DI matched two-way speakers with a constant directivity horn for the tweeter, using similar components for woofer and tweeter and similar crossover topologies. So naturally they would sound very much alike. Later, when Duke started making his Jazz Modules, he stuck with that design approach.

There is only one significant difference, in my opinion. Duke LeJeune and Earl Geddes both use round horns with a symmetrical 90° radiation pattern, and I use rectangular horns with a 90°x40° pattern.

The woofers in each speaker radiate omnidirectionally at bass frequencies, but the pattern begins to narrow into a cone shape in the midrange. Where the woofer pattern matches the horn, that's where crossover is done. In Duke's and Earl's speakers having round horns, the pattern remains a constant cone shape above that point, up to about 10kHz where it narrows to the compression driver exit angle. There are also lobes that appear in the crossover region above and below the speaker, off-axis in the vertical plane.

In my three π and four π speakers, the same thing happens except that the vertical pattern continues to collapse. The horizontal radiation angle is matched at 90° at the crossover point and remains constant above that point, but the vertical angle narrows to 40°, right where the lobes fall. In my design, the vertical pattern remains narrow from the crossover point up, actually taking advantage of those lobes.

I personally prefer this approach for two reasons. First, the narrower vertical pattern reduces ceiling and floor reflections. As I demonstrated at LSAF, if you clap your hands you can hear the HF ringing from reflections off the ceiling, and that's something I try to avoid by narrowing the vertical pattern at high frequencies. The second has to do with the vertical off-axis lobes I mentioned above, symptomatic of all DI matched loudspeakers like this. The position of the drivers on the baffle determines the angles where lobes fall, and this sets a maximum vertical angle for uniform response. My speakers have HF horns with vertical angle less than this, to avoid ripples in vertical off-axis response. The tweeter horn would not have pattern control in the vertical plane at this low frequency because it is too small. So these lobes actually help set the vertical pattern around the crossover frequency, and above that, the HF horn provides control.

I use a similar approach on my cornerhorns too, but instead of matching DI from a woofer with collapsing directivity, each susbsystem has equally matched directivity throughout the band. This has the advantage of being more uniform since directivity doesn't change, and also has reduced IMD by virtue of reduced bandwidth through each subsystem, i.e. three-way verses two-way. Of course, room modes shape the bass energies in the room, but if the opposite walls were anechoic, directionality would be truly constant through the entire band. Since no room is anechoic at low frequencies, another improvement one can make is to use multiple subs. Add subs, not just to extend the response but more importantly to smooth room modes.

And that brings me to a second difference that Duke included in his Dream Maker design. I think this is a great idea. Each speaker uses a second rear-facing woofer. This woofer is located in a different position in 3D space, which helps to smooth floor bounce and room modes. It works like a 2.5 way speaker or like having a subwoofer placed right beside or behind your mains, and located also at a different height.

In my opinion, this is the most effective way to smooth bass modes caused by standing waves in the room. It increases the number of bass sound sources, puts them in different points in 3D space, yet maintains symmetry and physical nearness to the mains so that the apparent source is the same. The woofers are far enough apart to average the bass nodes, certainly enough to fill in the floor bounce that would otherwise exist having a midwoofer placed at ear level. Yet they're close enough together to prevent any summing or localization problems.

Just from looking at the setup, I think it is a very good layout and I'd like to see measurements of it. I usually recommend to people installing subs that they model their rooms with CARA, and to try to achieve a room layout something like this. I suggest finding symmetrical arrangements that smooth room modes by putting the woofers in different places in 3D space, but physically close to the mains. This is built-in to the Dream Maker design.


Re: LSAF 2008 - Show Coverage, Seminar Recordings, Slideshows and Handouts [message #4843 is a reply to message #4842] Fri, 09 May 2008 15:17 Go to previous messageGo to next message
Keith is currently offline  Keith
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Registered: May 2009
Esquire
Don't get me wrong, I didn't think the Dream Makers sounded bad. They sounded good to me. Overall they are very balanced and pleasing to listen to. The slight bass hangover was the woofers I think. It wasn't the material because I listened to two songs and walked by the room a few more times and heard the same signature sound. Everybody there has the same room, so I don't think it was that. The bass was just a little too bloomed for my ears thats all.

Re: LSAF 2008 - Show Coverage, Seminar Recordings, Slideshows and Handouts [message #4858 is a reply to message #4835] Fri, 09 May 2008 18:07 Go to previous messageGo to next message
Martin is currently offline  Martin
Messages: 220
Registered: May 2009
Master
I really enjoyed listening to Bob's quarter wave seminar. It was a great discussion and I wish I was there to participate. Well done.

Martin

Re: LSAF 2008 - Show Coverage, Seminar Recordings, Slideshows and Handouts [message #4872 is a reply to message #4836] Thu, 15 May 2008 02:10 Go to previous messageGo to next message
Duke is currently offline  Duke
Messages: 297
Registered: May 2009
Grand Master
Thanks, Shane!

I think the classical piece you're referring might have been Rachmaninoff's Symphonic Dances and Etudes, Eiji Oue and the Minnesota Orchestra, on Reference Recordings.

It was great meeting you, and you can ask Richard about the preamp if you want. Shoot me an e-mail if you like and I'll give you his phone number.

Duke

Yup, we preach pretty much the same gospel [message #4873 is a reply to message #4842] Thu, 15 May 2008 03:17 Go to previous messageGo to next message
Duke is currently offline  Duke
Messages: 297
Registered: May 2009
Grand Master
I really think that getting the power response right by controlled directivity and pattern matching in the crossover region is basic to getting decent sound quality in a room. Vastly more important than a "flat" on-axis curve when the response is roller-coaster off-axis.

Whether this or that variation on the one true gospel is the most correct, I dunno. I still remember vividly my first encounter with you (crossover design seminar), and later with your speakers (seven Pi's) at the Midwest Audio Fest. Even from around the corner, your speakers sounded just lovely. Before I even saw them I knew they were something very special.

I've played around with bipolar speakers since the late 1980's, but it wasn't until I learned how to get radiation pattern control that I finally had the tools I needed to try to make a bipolar speaker that would "get it right" (in my opinion anyway).

By the way, I agree with Keith's observation about the bass being a bit heavy in my room. The Dream Makers were designed with the expectation of getting relatively little assistance from boundary reinforcement, as they like to be out in the room a good 5-6 feet. They were getting more bass reinforcement than they were designed for. While their port tuning is somewhat user-adjustable, it's not as adjustable as their sibling Jazz Modules - which are the more room-adaptable speaker. Note that I'd planned to show the Dream Makers in a large room, but that didn't work out (originally I set up in king-size room 915 on the top floor, but the whole room vibrated from the air conditioning tower on the roof so I relocated).

Next year I might show a satellite-subwoofer system, using my little four-piece subwoofer and some high efficiency satellites (which are still on the drawing board). Assuming the multisub system works as advertised, that might be the answer to getting smooth deep bass in a hotel room.

Duke

Axisymmetrical horns [message #4877 is a reply to message #4873] Sat, 17 May 2008 02:11 Go to previous messageGo to next message
Wayne Parham is currently online  Wayne Parham
Messages: 18670
Registered: January 2001
Illuminati (33rd Degree)

I really thought your speakers sounded nice. All the rest of this is academic. But in the pursuit of the best sound we can make, please don't be offended if I make an observation, a question about one of your design choices, really.

The one thing that always puzzled me is why you chose a round tweeter horn. I remember talking to Earl about his choice to go axisymmetric on the Summas too, when he could have chosen to use an asymmetrical prolate spheroidal flare instead. That shape is in the same family that he likes so much, with the throat radiused like the oblate spheroidal horn in the Summas.

I think you both use 90° axisymmetrical horns and a crossover around 1kHz. They're about 12" diameter, as I recall, so the center-to-center spacing from woofer to tweeter must be about 15" or so. With those general dimensions, I would expect lobes at around 25° above and below the forward axis. In that case, it seems to me it would be better to use a horn with 50° vertical pattern.

Why use a 90° round tweeter horn? Do you really want the tweeter pattern to be taller than the lobe angle?


Re: LSAF 2008 - Show Coverage, Seminar Recordings, Slideshows and Handouts [message #4878 is a reply to message #4872] Sat, 17 May 2008 04:58 Go to previous messageGo to previous message
Shane is currently offline  Shane
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Registered: May 2009
Illuminati (3rd Degree)
Yep Duke, that's the recording. That has to be one of the best recordings I've ever heard in any genre. Just spectacular sounding.

I'd love to talk to Richard about the pre, but my lack of specific knowledge about tube circuitry would more than likely frustrate him to no end ../emoticons/smiley.gif I just thought it was an interesting pre that sounded good and would love to see a schematic to try and build one.
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