Crossover help

[TLS Guy]

About 1st order slopes, it seems you have some preconceptions ... maybe based on past experience. But my experience has showed a somewhat different result. I'm not a huge 1st order proponent, but I have pretty high confidence that one would work extremely well on the Peerless poly woofer. Your assertations that you need exceptional drivers just isn't true, a perfect example is just about every product that Danny Richie at GR Research puts out ... he uses 1st order on all his woofers which are far from exceptional, with a zobel that does shaping as well. My approach with paper/poly woofers is often similar to his, cross low with a 1st order on the woofer and 3rd order on the tweeter. Or with something as smooth as the Peerless Poly cones I'd at least try a 1st order on both woofer and tweeter. But a 3rd order on that woofer is just not needed.




Well, I have no doubt this would be far better than what the OP had in mind ... but also there are hundreds of published designs around that have all the supporting measurements to go with it. And I don't mean to take a shot at you by any means, but I'd never publish or suggest a design to anybody without building it, measuring it, and listening extensively.



Honestly, with those woofers I wouldn't even bother with modeling. They're extremely easy to work with, I'd just put them in a box and put a guesstimate network on it and start measuring ... tweak, measure, tweak, measure.

And why are you so worried about having any tweeter output around the resonance? It's not like anything necessarily bad happens by doing so, but of course the only way you'd know is by first measuring said tweeter's frequency response, distortion behavior, and phase/impedance. I've done a 1st order network on a Vifa XT25 before centered at 2400hz, and even with it's huge resonance peak it performs very well. I mention that speaker specifically because it's at a friends how now replacing his Dynaudio Confidence C2's while they're being repaired, and he's shocked at how good they are in comparison to a $12K speaker. It's just a 2-way sealed bookshelf with about $300 of parts.

Driving a tweeter to its resonance sounds horrid. You can't use a first order crossover with that tweeter only an octave above Fs. If you think you can, you are just adding to the population of lousy speaker manufacturers, with which the audio scene is littered.

 

[Spkr_Bldr]

Driving a tweeter to its resonance sounds horrid. You can't use a first order crossover with that tweeter only an octave above Fs. If you think you can, you are just adding to the population of lousy speaker manufacturers, with which the audio scene is littered.

That may be true in some cases, but certainly not a generalization that fits. It seems like you're taking this personally, why? Have you personally tried an XT25 with a 1st order slope and resonance trap? Or do your preconceptions not allow you to try things like that?

Say what you want, but when I build a $300 sealed bookshelf that can hold it's own very well against a $12K pair of Dynaudios, I call that a success. My little bookshelf actually beats it (the owner told me today) in spatial cues and pinpoint imaging, and it disappears into the room better. The Dynaudio with it's Esotar tweeters has better top end articulation and more bottom end weight, which is to be expected.

So why would you tell me I can't do something that I have, and succeeded?

 

[TLS Guy]

That may be true in some cases, but certainly not a generalization that fits. It seems like you're taking this personally, why? Have you personally tried an XT25 with a 1st order slope and resonance trap? Or do your preconceptions not allow you to try things like that?

Say what you want, but when I build a $300 sealed bookshelf that can hold it's own very well against a $12K pair of Dynaudios, I call that a success. My little bookshelf actually beats it (the owner told me today) in spatial cues and pinpoint imaging, and it disappears into the room better. The Dynaudio with it's Esotar tweeters has better top end articulation and more bottom end weight, which is to be expected.

So why would you tell me I can't do something that I have, and succeeded?

If you power a tweeter significantly at or below Fs. Distortion rises off the clock, yes always, and the tweeter will roll off fast below f3, so you would have to adjust the woofer crossover to match, so they sum. That's speaker design 101. Any how a speaker that drives a tweeter out of its band pass and yes, powering only 6db down at Fs is significant powering, makes for a harsh, and not a smooth speaker. So after doing this as long as I have you know what not to waste your time with.

 

[Spkr_Bldr]

If you power a tweeter significantly at or below Fs. Distortion rises off the clock, yes always, and the tweeter will roll off fast below f3, so you would have to adjust the woofer crossover to match, so they sum. That's speaker design 101. Any how a speaker that drives a tweeter out of its band pass and yes, powering only 6db down at Fs is significant powering, makes for a harsh, and not a smooth speaker. So after doing this as long as I have you know what not to waste your time with.

It's just not that simple, period. An example, HD of a D26NC55 ... just a cheap $28 Vifa tweeter with a fs of 1500hz.

I don't see distortion rising off the clock. 2nd and 3rd harmonics are still 50 db down at Fs.

I never said to cross it below Fs, just that you can get an octave or two away with many tweeters and it not be the end of the World as you represent it.

 

[TLS Guy]

It's just not that simple, period. An example, HD of a D26NC55 ... just a cheap $28 Vifa tweeter with a fs of 1500hz.

I don't see distortion rising off the clock. 2nd and 3rd harmonics are still 50 db down at Fs.

I never said to cross it below Fs, just that you can get an octave or two away with many tweeters and it not be the end of the World as you represent it.

That's a highly damped tweeter, you can see the resonance is highly damped between 1.5 and 1.6 KHz. The response falls at 12 db per octave below that. So if you were to add a a first order crossover, the composite slope would be third order. If you did this around 2.2 K Hz then the tweeter would have the electrical signal only 12 db down at 550 Hz It would not be 24 db down until 125 Hz. So the voice coil would be stressed and invite burn out. In my view that is far too much power to present to a tweeter. I would never consider a first order crossover below about 4.5 KHz because of the power that is delivered to the tweeter if you crossover below that with a first order crossover.

The next issue is that to make a good first order crossover, you need drivers with wide response either side of the crossover. In this case the composite woofer and crossover slope would have to sum to third order below 1.5 KHz. It would be highly unlikely that would happen with a first order crossover to the woofer.

There were many reasons I chose the topology I did for that crossover. Not the least of which was keeping all drivers in a pass band not only were they would perform the best, with good crossover frequency response, but to keep the drivers in a range where their off axis response is excellent, and mirrors exactly the on axis response. The speakers then will be much more tolerant of room reflections.

There is a reason that first order crossovers are seldom selected, and good reasons why higher priced tweeters usually have FS below 700 Hz and often as low as 500Hz.