Yes.So, are you talking about the cascaded x-over?
It provides slightly better overall phase-matching of the system, but also the added advantage of further high-pass filtering on the 4" driver.
Yes.So, are you talking about the cascaded x-over?
Hi Burning SoundsDo you have any links to the work done by Laub, Boers and Finke?
Laub here... If you (or any forum member) wants a copy of my manuscript from 2022 about "minimally baffled" speakers just drop me a message and I will send it to you. It's an evolution of the 20-20k dipole whitepaper that is linked above by @JeyB.Do you have any links to the work done by Laub, Boers and Finke?
Yes, I do pull them out for listening. I know Sigfried recommended at least 3 feet from the front wall, but realize many 521 owners bring them much further into the room, which doesn't have a very appealing WAF lol, which is very much at play in my situation. I did pull them into the room for the measurements that I made. That being said, I don't think one should have such wild frequency/SPL response fluctuations.
Hi Burning Sounds
Of course I have. Here you have them.
Gerrit Boers' absolutely full constant directivity 20-20 KHz design and implementation, including the assembling of Hypex power amps, Hypex DLCP crossover and custom designed planar tweeter. Astounding work in my opinion. The resulting polar measurement is out of this planet. Nude drivers is the way to go, I also think. Use Google Chrome for a very exact translation from Netherlands to English. The real show begins around page 6 or 7, if my memory serves well.
Charlie Laub has also constructed a true CD transducer 20-20 KHz. In my opinion, he implements a great and quite innovative way to use two inexpensive 1" nude dome tweeters with waveguides to achieve constant directivity performance up to the highest frequencies. This is Achilles heel in LX521, because I suppose SL was forced to set up a very high crosspoint to the Seas tweeters (above dipolar peak and above diffraction zone) to get some control on the directivity of the 27TFFNCs. This was due to the fact that the Seas tweeters showed a bad pattern in that zone from 2 to 6 KHz, so a dead end. As a consequence of this fact, I think SL was forced again to add much more passband to the MU10RB high mid driver than what he was willing. It should have been crossed up at a significative lower frequency, at about 3 to 4 KHz, but his selected tweeters didn't allowed him. Could it be a better transducer without these impositions? Maybe yes, maybe not. The thread itself is a fantastic work by Charlie Laub, with quite interesting opinions by other informed writers.
In Pursuit of a 20-20k Dipole Loudspeaker
I thought I would kick off 2019 with this thread about dipole loudspeaker design and construction. Specifically, how to create a loudspeaker having a dipole radiation pattern across as wide a frequency range as possible, when it might make sense to abandon this goal in favor of some other...www.diyaudio.com
And finally, here is the thread by Rudolf Finke. He has also married two opposed and nude smaller dome tweeters but without waveguides. Despite getting a quite good horizontal response off-axis, the vertical directivity resulted a disaster and he abandoned the idea.
On the directivity of dipole tweeters
There have been some attempts lately to make dipole tweeters work up to high frequencies with constant directivity. How high can we go, if the tweeter housing is already almost as small as its radiating area? I would like to demonstrate the issues involved with an idealized 1 inch circular...www.diyaudio.com
Best regards
Laub here... If you (or any forum member) wants a copy of my manuscript from 2022 about "minimally baffled" speakers just drop me a message and I will send it to you. It's an evolution of the 20-20k dipole whitepaper that is linked above by @JeyB.
I see the source of your confusion... Using "transducer" in the sentence above is not correct and it should read: "Loudspeaker"
Is the transducer described in its final form, preferably with measurements.. somewhere in the 28 page thread Jey linked to, or elsewhere?
Hi RichardHi Jey
I just saw your description of Gerrit Boers' speakers with “constant” directivity - apparently better than Linkwitz final design
awaiting confirmation but assuming you’re not making it up lol - Much appreciated
Went to the thread in the link …11 pages - in Dutch … now hoping someone able to search the thread than me will direct me to specs & especially the measurements
I just saw your equipment list in your footer. And an octagonal room. Very impressive
Anyhow … what is a monkey box?
Cheers
While I don't find the UM driver to sound harsh it can sound slightly edgy on some recordings, but is perfectly fine on others, so I'm not completely convinced it is the driver that is at issue here.Well, we can all constabtly learn things, I do every day and it is one of the joys of living!
My experience with my Lx521 is they upgraded the wrong driver. I have not found any issue with the lower midrange driver which now has an expensive replacement. And while the upper midrange driver measures perfectly and I can tune any which way with my pc based crossover/dsp - i just find it sounds "harsh" compared to other speakers I have - Genelec, Neuman etc. I just dont think its a nice sounding driver no matter what I do. Considering how little the tweetets actually do, I dont think they need replacing, but do need shelving down. The bass is phenomenal!
Yes, I know what ASPv2 does, that's why I asked you in an earlier post if that was what you were referring to.The newer ASPv.2 is essentially a reversion back to the original crossover design. It uses a state-variable topology vice the Sallen-Key configuration, plus a few notches/peaks to fine-tune the drivers.
The LX521 system has not changed in general concept since day one.
Also, the need for all-pass filters is removed if using a DSP setup since you can program pure delays to achieve the phase-coherency.
another true constant directivity prototype, mainly with nude drivers from 120 Hz up, just to discover what difference is perceived psychoacoustically compared to my own LX521.
Hi RichardI totally understand your motivation, and your goal
re nude drivers
You probably know that the 521’s baffle shape was arrived at by experimentation. angularity aside, relative to his previous speaker the Orion in terms of baffle size I’d say, ball-park it’s “70% nude”. It’s a shame he didn’t share the shapes he tried and their results
“won't be a single driver loudspeaker”
Of course. Unless you’re aware of a driver that is from an alternative reality lol … mission impossible
“ It will be 4 way, 7 drivers”’
Sounds about right. At diyaudio, poster andyr made a nude baffle dipole. a 3-way
From memory
the frame is metal
7 drivers: 1 tweeter, four midwoofers and two bass drivers
the four midwoofers are SB Acoustics, arranged in a square pattern abutting each other.
I don’t know why he didn’t put the tweeter in the centre, but it’s in the usual position above them
Probably worth a look. Let me know if you have trouble finding it
It got very high praise from a very good amplifier designer
As of now I know nothing about Charlie's. It could be even better?
Cheers
Richard
Yes, all of the changes/revisions have affected the sound.Yes, I know what ASPv2 does, that's why I asked you in an earlier post if that was what you were referring to.
I agree that the LX521 system has not changed in general concept, but there have been what appear on the surface to be a few minor changes that do affect how it sounds IMO.