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Old 2nd October 2004, 05:53 PM   #1
JoeBob is offline JoeBob  Canada
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Default What's your favorite crossover slope?

I'm currently buying parts for my next speaker project, a three-way with a widerange driver in the middle, I'll be crossing it over to a large woofer and a tweeter to fill in both the top and low ends, but my problem is this, since it's a widerange driver, I'll be crossing over high for the tweeter and low for the woofer, so I'm sure a single-order slope would work (maybe 2nd for the tweeter, just to be safe), but would it sound good? I remember reading somewhere that odd-order slopes sounded better than even-order, why is this? If so, I think I'd lean towards a third-order, since it'll be an active x-over. But are there any drawbacks to higher order slopes? Should I keep it low if possible?

I've always built the crossovers to suite the drivers (high-order on ribbon tweeters, because I had to), now that I've got the choice, I'm not sure which is preferable. Oh, and this begs another question, should I look into subtractive x-overs or not? Hmmm... So many questions today.

I know in the end I'll have to tweak it to the loudspeaker, I would just like to start off as well as possible.
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Old 2nd October 2004, 06:00 PM   #2
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XO slopes required depend totally on the measured response of the drivers in the enclosures, along with cone break-up and response peaks/nulls. Once you know all of that then you can design a crossover, not before.

So, my advice is to build the boxes first, then test and experiment to see what suits your taste and measures well.

Doesn't really help that much, I know, but it is a realistic answer...
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Old 2nd October 2004, 07:31 PM   #3
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Default Re: What's your favorite crossover slope?

Quote:
Originally posted by JoeBob
[B]I'm currently buying parts for my next speaker project, a three-way with a widerange driver in the middle.... Oh, and this begs another question, should I look into subtractive x-overs or not? Hmmm...
This is the kind of system i tend to build (think about building). Often on the top end i just let the FR run to its limit and bring in a superT with a single cap. On the bottom, i've been partial to subtractive -- just been reading Nelson's paper on the subject over & over. His use of a buffered PLLXO for the filter stage is facinating. The droopy respnse of a 2nd or 3rd order section helps kill the bump in the derived leg of the XO. What i'm having a bit of trouble with is how the levels add up right going into the adder.

In a fully active system i'd have 2 or 3rd order on the bottom, same on the top, with the FR having the derived 1st order bandpass. (i keep looking a a set of little teeny EL94 OPTs that should make a killer HF amp)

I've a set of Arun Cantus 2si -- i haven't decided whether to pursue a system with multiple FE103A or a JX125 (my JX150s look like they will morph into 125s) in the middle -- with 4 Foster 12s or 4 Peerless 8s on the bottom)

dave
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Old 2nd October 2004, 08:43 PM   #4
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Default Low- vs. High- Order Active Crossovers. High- Order Active Crossover

Hmmm....
I tried to question the same in this thread:
Low- vs. High- Order Active Crossover

Right now I'm using 4th order LR active filter - which I like

After my surfing'n'reading on the internet and discussing with other DIY-HiFi people
My conclusion is: 4th order active

Well that is just my opinion!

- You can find people prefering 1st order passive x-overs
- You can find people prefering 32th order active

Regards, Ask
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Old 3rd October 2004, 01:45 AM   #5
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Default Re: Low- vs. High- Order Active Crossovers. High- Order Active Crossover

Quote:
Originally posted by askbojesen
After my surfing'n'reading on the internet and discussing with other DIY-HiFi people
My conclusion is: 4th order active

Well that is just my opinion!

- You can find people prefering 1st order passive x-overs
- You can find people prefering 32th order active

Regards, Ask
Myself, I almost never get what I want with 4th order and
above.
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Old 3rd October 2004, 01:47 AM   #6
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Default Re: Re: What's your favorite crossover slope?

Quote:
Originally posted by planet10
On the bottom, i've been partial to subtractive -- just been reading Nelson's paper on the subject over & over.
You want to get John Curl's comments, as he has been there
also, having designed the Symmetry crossover, which was an
interesting subtractive design. (Correct me if I'm in error, John)

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Old 3rd October 2004, 03:46 AM   #7
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Something that's been hinted at but not stated outright is to go for the lowest order crossover that will get the job done. Sure, it's easy enough to say that, well, a six (1st order) crossover will do, but I think I'll go to 12 or 18. Unh unh. Stop at six if it does the job. Or if it takes 12, stop there, etc. Odd order crossovers have some advantages, but it's seldom, if ever, the make-or-break kind of thing that you might expect.
Your goals are:
1) Protect drivers from frequencies that could damage them
2) Don't ask drivers to reproduce frequencies that they can't do well.
3) Sound good.
4) Avoid--to the extent possible--having to tailor the frequency response.
1 is an absolute--if you're burning drivers, you're going to run out of money quickly. 2 & 3 are related. 4 is loosely related to 1, 2, & 3, but keep in mind that frequency tailoring involves phase shift, which is bad. The arguable exception here is the very lowest frequencies. It's very difficult to get flat response below about 30 or 40Hz without having to tweak things a bit. Related point: Don't believe Thiele-Small simulations--they are poor approximations of reality (don't say I didn't warn you).

Grey
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Old 3rd October 2004, 12:19 PM   #8
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Since you want to go active anyway I'd recommend a subtractive crossover.
Since the derived slopes are only 1st oder usually, the feasibility depends heavily on the drivers used of course.

You can do symmetric and asymmetric constant-voltage subtractive crossovers of higher orders like 2nd/2nd or 3rd/2nd but that comes at the price of increased overlap and higher bumps (i.e. incrased power needs).

Regards

Charles
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Old 3rd October 2004, 02:00 PM   #9
rabbitz is offline rabbitz  Australia
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Quote:
Originally posted by GRollins
Something that's been hinted at but not stated outright is to go for the lowest order crossover that will get the job done. Grey
This reply has got to be one of the best bits of wisdom I have even seen on a post about crossovers. Well put Grey.

These wise words should be in the Wiki to be remembered forever.

Cheers
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Old 3rd October 2004, 04:02 PM   #10
Ken L is offline Ken L  United States
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Default I think it depends on the variables

Running the Azuras full-range and crossing to a sealed sub at 134hz, it always integrates better with the higher orders -

When using the Behringer - I migrated to 48DB slope.

When I sold the Behringer and started using the BSS FDS366, it sounded better with the 52dbm NTM slope.

One major advantage of using a digital crossover has been the ability to try the various slopes, in addition to being able to dial in delay, phase and EQ.

Does that mean I think everybody will be better with 48db or 52db slopes at 130-135 hz? Nope! Not at all.

I believe you will find differences in whether it is done digitally, passive or active.

Saying one slope or approach is better - overlooks the differences in the various frequencies and approaches.

Soooo, I don't think you can say any one slope is best for all situations - it's going to depend on the drivers, the hz, etc., and what method you're using to achieve the crossover function

Regards

Ken L
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