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Linkwitz LX521.4 Review (and measurements!)

Ok, so the passive xo is bad!


Dave, can you perhaps show us some polars of LX521? I checked briefly OPLUG topics but no hits... ps. I think that Frank is planning something about this...
 
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Sorry - ASP is explained here https://www.linkwitzlab.com/LX521/Supplies.htm
Later on Nelson Pass made passive xo, that's another story.

Yes I noticed SL's horizontals, but asked for others too, perhaps with different dsp/asp. I am just curious to find out what causes this 5-7kHz dip! Below 500Hz wiggles can be expained with the room and placement.

Some early posters in this have shown responses of speakers with DSP and ASP, and ASPs show that dip 4-7kH. So obviously it has a flaw despite SL approved it, perhaps it has non-optimal tweeter delay? See how this (obviously) dsp-version vertical dispersion response at -10 and +20deg has deep dip at 7kHz xo (timing difference). But -10deg has hihgest spl 2-4.5kHz These findings hint to timing/delay mismatch between upper mid and tweeter (what was design axis height?)

1736186741055.png


And this is SL's horizontals Notice 0-45deg spl 2-5kHz in both directions... low directivity compensated with dip in on-axis.
1736187642953.png


ps. I have set up several multichannel speakers and protos with minidsp and Hypex only for 12 years so far...
 
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SL created the LX521 baffle shape by repeated trial and error. He started with some shape and then cut away here and there while remeasuring. What you have today is basically as little baffle as possible, as he found that to give the best pattern while still being able to have enough left into which he could mount the drivers. The baffle shape and response pattern was far from the only aspect of the loudspeaker that was important to him. He valued low energy storage and low distortion, especially IMD, and he did extensive testing to find the drivers that were used in the original LX521 speaker. This is why, for example, he used two dome tweeters - they have very good performance even if not a great dipole pattern. For my own projects I choose pattern over distortion performance, so I use AMT tweeters that are dipole or close to it throughout their range. I outline the design choices and design procedure in my 2002 paper and provide some technical background about why a "nude" driver is best for midrange and tweeter.
I've been puzzling over where the advantages of open baffles end in frequency, that is, where should one transition from open to box. I'm using a homemade simi-isobaric sub (in a box, with a port on the interior chamber, hence a "semi-isobaric") with two 10 inch driver for each sub fthat goes to 125 hz. Then going to an open baffle 12 inch driver that goes up to 325 hz. 48db Crossovers are done with Mini-Dsp. I use an 8 inch above that to 600 hz, open baffle. Mark Audio drivers above that to the tweeters. My version fires forward, although we are working on a omni-directional version too. Anyhow, this is what we have come up with after about 5 years of work, on this design. Way more work in the past on other stuff. Still, I wish there was some kind of research about this, other than our semi-relentless tinkering. It may be somewhat subjective, a preference for open, or boxed sound.

An idea that might be useful. Maybe as a transition from a boxed sub and an open baffle speaker. Nelson Pass sold a kit open baffle at a "speaker camp" a couple years ago that had a innovative and trendy feature. The speaker was a speaker with a Tangband full range and a 15 inch bass driver, both open baffle. However, the bass driver fired down into a V-shaped enclosure that open into about a 2 1/2 inch slot in the front. An engnineer friend said what he was doing was loading with the slot to get 6 db more firing out the front (where the slot opened). When we saw this, we thought, "Why didn't we thing of that, argh!?" Doesn't take much room, sounds very good. When measured, it provided a 80 hz lump in my room, and so ...not perfect. For $800 with the crossover, drivers, and flatpack, everything - amazing value, kind of genius. All hail to Pass. Also, the camp was a fun way to pick up some skills (although the build would be easy for most), and there were plenty of people there to help, including Pass and his son. This is a reference to the 2023 camp with info and pics of the speakers:


I guess I should mention I have no commercial or other affiliations with Pass, or the speakers shown below, and Pass is probably not making money on this anyway. Actually, the speakers below also have some sort of claimed charitable or non-profit status.

And to explain the "trendy" comment here is a different kind of slotting, done by a Diy group, shown at the Pacific Audio Show"


Coincidentally, I went to an AMT tweeter after a friend bought more expensive AMTs and compared them to Dayton's. Found no hearable or measurable differences, at least for the way we use them. Which is from 2800 kHz and up,. The AMT's that are the dipole, open backed, seem to be better sounding than the Corundum tweeters that we were using (plus, the Corundum tweeters are "unobtainium" these days). I was using a planar and the Corundum for the treble, and by comparison, the AMT sounded more accurate, real, airy...yeah I know, a bunch of subjective mumbo jumbo.
 
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"Nelson has never made any contribution to the LX521 implementation....active OR passive"
Right, sorry, he did LXmini ASP. It is a long story with many changes! I am just an innocent bystander, more a disciple of Kreskovsky actually. I met SL once at AES 51st August 2013 and introduced him my 4-way dipole project that use Minidsp 4x10HD...


ASP seems to have many versions... at first mids had passive 1st order xo and ASP was 3-way

But how about that 5-7kHz dip with ASP room measurements? Don't you have anything to say about it?


By the way LX521 (and Orion) was critisized long ago for other issues too...
John K's website here https://musicanddesign.speakerdesign.net/products.html

Now I'll rest my case for some time.
 
I've been puzzling over where the advantages of open baffles end in frequency, that is, where should one transition from open to box. I'm using a homemade simi-isobaric sub (in a box, with a port on the interior chamber, hence a "semi-isobaric") with two 10 inch driver for each sub fthat goes to 125 hz. Then going to an open baffle 12 inch driver that goes up to 325 hz. 48db Crossovers are done with Mini-Dsp. I use an 8 inch above that to 600 hz, open baffle. Mark Audio drivers above that to the tweeters. My version fires forward, although we are working on a omni-directional version too. Anyhow, this is what we have come up with after about 5 years of work, on this design. Way more work in the past on other stuff. Still, I wish there was some kind of research about this, other than our semi-relentless tinkering. It may be somewhat subjective, a preference for open, or boxed sound.

An idea that might be useful. Maybe as a transition from a boxed sub and an open baffle speaker. Nelson Pass sold a kit open baffle at a "speaker camp" a couple years ago that had a innovative and trendy feature. The speaker was a speaker with a Tangband full range and a 15 inch bass driver, both open baffle. However, the bass driver fired down into a V-shaped enclosure that open into about a 2 1/2 inch slot in the front. An engnineer friend said what he was doing was loading with the slot to get 6 db more firing out the front (where the slot opened). When we saw this, we thought, "Why didn't we thing of that, argh!?" Doesn't take much room, sounds very good. When measured, it provided a 80 hz lump in my room, and so ...not perfect. For $800 with the crossover, drivers, and flatpack, everything - amazing value, kind of genius. All hail to Pass. Also, the camp was a fun way to pick up some skills (although the build would be easy for most), and there were plenty of people there to help, including Pass and his son. This is a reference to the 2023 camp with info and pics of the speakers:


I guess I should mention I have no commercial or other affiliations with Pass, or the speakers shown below, and Pass is probably not making money on this anyway. Actually, the speakers below also have some sort of claimed charitable or non-profit status.

And to explain the "trendy" comment here is a different kind of slotting, done by a Diy group, shown at the Pacific Audio Show"


Coincidentally, I went to an AMT tweeter after a friend bought more expensive AMTs and compared them to Dayton's. Found no hearable or measurable differences, at least for the way we use them. Which is from 2800 kHz and up,. The AMT's that are the dipole, open backed, seem to be better sounding than the Corundum tweeters that we were using (plus, the Corundum tweeters are "unobtainium" these days). I was using a planar and the Corundum for the treble, and by comparison, the AMT sounded more accurate, real, airy...yeah I know, a bunch of subjective mumbo jumbo.

When you cross over from a dipole radiator to a monopole, you will get a small band through the crossover region where the response is cardioid. A cardioid results from the sum of a monopole and a dipole, when each have the same on-axis SPL. So you can also overlap the two drivers to generate a cardoid band instead of the usual crossover where the LP and HP corner frequencies are the same.

That being said, I am in favor of using closed box subwoofers for the lowest frequencies, e.g. below about 70 Hz. At some point, no matter how big your OB system is, the dipole losses become too much to overcome. CB can pressurize the room and gives you that tactile feel that an OB speaker cannot, in most cases.

That Pass speaker was still a dipole.... not a great one overall IMO...
 
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