Zaph's WaveguideTMM crossover error

[sreten]

Hi,

Seems I'll have to post this here as there seems no other choice.

With the revised 0.5 way layout L1 should be 0.2R DCR (not 0.4)
and L2 should be 0.4R DCR (not 0.2), unless there is some bizarre
logic at work I haven't fathomed out.

The point being as L1 sees both drivers its DCR is effectively doubled
compared to L2, so why make L2 effectively 1/4 of the DCR of L1 ?

/sreten.

[Zaph]

Well, this certainly wouldn't be the first time one of my crossovers has been misunderstood and declared incorrect. That's actually one of the many reasons my email address currently isn't posted. Of course, making a post here under the assumption that there is an error pretty much forces me to respond, so I guess that plan failed.

Those values are correct. I've attached the list of components from Madisound required to build the perfectionist version without the impedance comp circuit.

Yes, both drivers see the .41 ohms in L1.

.41 ohms as a series resistance affects the woofer's Qes and gives us a little deeper bass response at the expense of sensitivity. But it's not really an "expense" because this puts the woofers right at a level that matches up with the tweeter perfectly without the use of an L-pad.

The .21 ohms in the BSC inductor insures that the lower woofer is producing sound at the same level as the top woofer, which also extends bass response and provides good acoustic coupling below 200hz.

John

[sreten]

Hi Zaph,

I'm sorry if you feel I've done you a disservice, and forced you into
a position you would rather have avoided, but I couldn't e-mail you.

Seems to me as long as system Q is not marginal then having
the 0.5 way driver at near the same level and Q as the bass /
mid driver is not a necessary condition for design.

In fact in some cases it could help having lower output and
higher Q by somewhat reducing (slightly) the full 6dB BSC of
a 0.5 way, and by dint of the higher Q the 0.5 way driver
would actually produce more bass than the mid/bass driver.

If you've considered the above and rejected it, I apologise.

/Sreten.

[Zaph]

No worries Sreten. You'd probably know how I feel if you continuously got emails saying "there's something wrong with your crossover." I don't normally spend time answering those types of questions anymore. What people really mean is "I don't understand your crossover or design choices and I need them explained to me."

While my projects are generally well documented, rest assured that there's a lot of small details that are thought about but not mentioned. After all, I can't write a 300 page book for each project. Minescule little details like "why is the spacing between the woofers 3/8" different than between the top woofer and the waveguide?" well, I have a reason, which I've already had to explain several times.

Crossover components in my diagrams are occasionally determined by what I have in stock to test with. I pretty much have one of everything, but sometimes I don't have multiple DCR's to chose from. Though in this case, I did have a solen perfect lay with about half as much dcr, but I determined the madisound air core to work better and be cheaper as a bonus.

[Rolandas3]

Hi,

it could more easier to include some additional comment for dummies (if did not allready), since it could save some internet resources (and your e'mail space ) from sending less spam

Originally posted by Zaph
No worries Sreten. You'd probably know how I feel if you continuously got emails saying "there's something wrong with your crossover." I don't normally spend time answering those types of questions anymore. What people really mean is "I don't understand your crossover or design choices and I need them explained to me."

[kneadle]

By the way Zaph, since we've got your ear, thanks for posting the 5.5" comparisons on your site.

Sorry to threadjack...

Dave