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In Reply to: RE: I give you.... FrankenStereo... posted by briggs on April 05, 2016 at 14:27:30
I think you're mistaken. The SR-71 is a LR4 xover at 1750hz.
Follow Ups:
The 330 Hz crossover is Presto's, not Krutke's.
Zaph's ZR71 is an asymmetrical 4th order at 1750 Hz.
With my active crossover, I am using 3rd order *electric* filters. It is a considerable design restraint to have fixed-order/fixed-Q filters, but thanks to driver selection and good extended flat response this ended up working okay for this "spur of the moment" design. A fixed crossover would not be my first choice for a new design, aka if I was out purchasing an outboard crossover. Selecting crossover type/order/Q is just too powerful and versatile to pass up when working with (most) real-world drivers... I would not have even bothered to try this, but I using my DSP crossover application I was able to simulate what 3rd order BW (fixed Q) filters would do for the response, and it seemed to work pretty well. Had it been an abomination I would not have chosen that path, because of all of the equalization required. I like to get filters right to get the desired acoustic response rather than use textbook filters and eq the living hell out of it.
I am using 330 and 2200 as Fc points because they are reasonable points considering each driver's range and they sum more favorably with less equalization required. Sometimes these points choose themselves, really, and you just have to pick your poison - aka which design tenet you're most hung up on. I could have gone 2500 or even a bit higher with such a small tweet-to-mid center spacing... but, I didn't need to. (I originally did because the Vifa D26NC55 is much cleaner above 2500 but 2200 was not a big sacrifice by any means.) I don't have distortion data for the 4" mids, but given their 3/4" voice coil diameter and relatively small magnetic structure I am certain it's going to be much sweeter as a dedicated midrange. What's impressive is how much power I can get out of these rather small looking little mids (at two per side) when they're only handling "3 and change" octaves. I really really like them as mids.
The goofiest thing about this design is indeed crossing over at 330 to a 7" driver, but as I said, an 8 or 10" would have been a better choice if designing the baffle from scratch. I *really* like the bass from those Seas woofs though! Tight, tuneful with decent sensitivity for a 7". Much more sensitive than the 7" Dayton metal cone drivers I had in there... they are very flat and low distortion but they need a bit more power. That's the nice thing about active... you can compensate for different driver sensitivities with the turn of a knob.
Cheers,
Presto
After some sixty years in audio, I'm a minimalist, two-way, two driver, first order series passive crossover guy. This stuff is way beyond me.
Enjoy!
Hey Briggs:
When you cap off a tweet (1st order electric) to blend it with a fullrange that is rolling off naturally, you can get a reasonably flat response... but what you can't normally get is the kind of impulse response that a 1st order ACOUSTIC design will get. Ironically, a 1st order acoustic design takes a bucket full of components for the requisite level and impedance equalization, and since only cuts can be made in the passive domain, they're not normally that sensitive either. (85-86db 1w/1m or therabouts).
Interestingly... if you get the Thuneau Arbitrator plugin and use a PC for playback, you can make any speaker system (passive OR active) transient accurate.
My take on "time/phase coherent speakers" is that they can measure well and even produce square waves, but there are other aspects to a speakers design that are probably even more vital...
I've done a/b comparisons with 4th order LR and 4th order LR corrected (aka transient accurate, confirmed with measurement) and to be honest... it's a very subtle difference at best.
Tonal balance and drive integration is far more important, IMO, than TA performance, but some TA aficionados would scream HERESY!!
Anyways, enjoy your capped off speakers.
I think I want to try a system with a full-range and capped off tweet now.
Sounds like a lot of fun!
Cheers,
Presto
I would avoid any speaker system design requiring "a bucketful of components", and I did not say I advocated simply capping off the tweeter and letting the woofer roll off acoustically. I have experimented with that and was not satisfied with the results I got. I will not claim that it is a bad approach, though. There may be cases where it works. I failed to make it work for me.
What I did say is that I prefer (this is different from advocating) two way first order series. I will add that my primary listening interest is chamber music. I may be playing on a very different field from you.
I believe I define sophistication differently from you. In my case, a speaker system consists of six components: woofer, tweeter, capacitor, inductor, padding resistor on the tweeter and an enclosure. I think that is enough for the home builder to cope with, regardless of his level of technical "sophistication". I made a living designing computer systems and business processes, and worked long and hard to make them simple. That, to me, is sophistication.
And, thanks anyway, but I did not need the tutorial on crossover theory. I appreciated your telling of your listening experiences, but you did not specify what kinds of sources and program material you listened to. You should not expect to hear something that was not in the source material in the first place.
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