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Old 11th December 2012, 04:18 PM   #1
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Default Larry Wormer's LX5 Crossover Help

I am looking for some help understanding the crossover the Larry Wormer built for his Optimus LX5 speakers.

See the article here: LX5

First, Larry describes his crossover as a sixth order, but the diagram shows only a third order. Is it possible he used some advanced theory to simplify the crossover to use only 3 components? My own research shows this to be impossible. A sixth order crossover needs 6 components to work.

If he misspoke and did create a normal third order crossover, how come I can't reproduce his values? On my LX5s, the tweeter has a Re of 6.2 and the woofer has a Re of 4.7. This means a third order filter on the tweeter would be a C1 of 8.8, an L1 of .3 and a C2 of 26. Larry's C1 is 7.2 and his C2 is 10. I can't figure out how he got those values. A Re of of 7 on the tweeter would give me a C1 of 7.5 (close enough), but C2 is 22 (nowhere near 10).

Any thoughts?


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Old 11th December 2012, 04:34 PM   #2
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Quote:
by taking advantage of the driver rolloffs
That's the point: probably the software (Calsod) has to hit the target when referring to the final curve/slope/roll-off. So a woofer (and also a tweeter)
has a natural 2nd order rollof, accentuated by the box/baffle .Just sum
the gradients/slopes and you have the desired 6th order. One thing is the electrical roll-off, but the target is acoustical .
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Old 11th December 2012, 05:13 PM   #3
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Thanks for the reply Pico,

I see now what he meant by sixth order, but electrically only three....I guess it was just the way he wrote it didn't work for me.

I plan on getting a hi-vi Kevlar woofer to go with my linaeum tweeter, and will be making my own crossover + box and wanted to know how he got his crossover values so I could make the same improvements to my own.

Guess I was hoping there was new advanced theory I could check out, but in reality, it was probably all in that software. I like to double check things and learn how to do the work myself, but I can't do that without knowing how that software works.

Off hand, do you, or anyone else, have some suggestions I can research for incorporating a natural roll-off into my crossovers?

A quick search online showed something about a transient perfect crossover? Is that the actual term for what I am looking for?

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Old 11th December 2012, 08:07 PM   #4
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Oh..well..er : you're welcome
I'm not into simulation and measurement at all, I just swap
things that are in the basket.
About perfect transient response, that might be theoretically true
just for the tweeters, and among them only isodynamic/ribbon tweeters
might perform fairly well regarding that particular parameter.
Like for crossover analysis, there is the electrical part and then there
is the electro/mechanical/thermic/??? that is the loudspeaker, which has
some mass so it's impossible to make it start&stop suddendly.
Not to mention the whole system, which is subjected to many filterings
(like the Cd anti-aliasing low-pass at 20 KHz ) that have the effect to limit
somehow the transient response.
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Old 11th December 2012, 09:59 PM   #5
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Kinda sounds like I shouldn't bother

I was hoping that since these linaeum tweeters were ribbons, I would try some different crossover topologies and perhaps run them real low.

I am still going to try some different things of course, I was just trying to understand what Larry was doing with his.

I don't think matching the roll-offs is going to be what I want anyways. According to Madisound, the Hi-Vi L5-8R starts rolling off after 6KHz....I didn't want to run it that high. I was hoping to run the tweeter real low so I get as much of the ribbon sound that I can get. As far as I can tell, no one has actually tried going real low with this tweeter.....

The Dayton Audio DATS system won't measure it so I have nothing to go on besides guess work.
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Old 11th December 2012, 10:32 PM   #6
sreten is offline sreten  United Kingdom
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Hi,

You can't run the ribbons real low, end of story.

Your best bet is to follow the mods. Don't introduce
a driver you don't have a good known x/o design for.

rgds, sreten.

Ex owner and modder of LX5's.
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Old 13th December 2012, 07:30 PM   #7
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Well, I am going to follow the mods as described and see what happens. I am still suspicious of them since I can't recreate any of the values he chose myself. Even the imped comp doesn't match up with anything I have figured out myself, both measure values and listed values I found online.

Odd.

Thanks for the replies everyone!
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Old 13th December 2012, 07:40 PM   #8
sreten is offline sreten  United Kingdom
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Hi,

Nothing odd about it. Online calculators are crap.

Make sure you have the version the mod is for.
The sixth order acoustic x/o uses lower order
electrical slopes along with the drivers responses.
The drivers must be the same for it to work well.

rgds, sreten.
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Last edited by sreten; 13th December 2012 at 07:46 PM.
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