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Advice needed: mixed order Linkwitz Riley crossover
Advice needed: mixed order Linkwitz Riley crossover
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Old 14th January 2014, 03:57 AM   #1
Zoodle is offline Zoodle  Australia
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Default Advice needed: mixed order Linkwitz Riley crossover

Can I mix orders within a 3-way LR crossover (EG tweeter slope: 24db; mid-range slope(s): 12db; bass slope: 24db)? Or will I mess up the benefits of the LR system? (IE the phase constancy across the freq range).

I know Linn did something like this with at least one of their active crossovers, but not sure how.

Background: I'm using Elliot Audio (ESP) boards, plus the ESP component calculator, and I currently have a 'by-the-book' two way system (also ESP) which sounds stunning.

Last edited by Zoodle; 15th January 2014 at 01:37 AM.
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Old 14th January 2014, 09:13 AM   #2
ctrlx is offline ctrlx  United Kingdom
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what actually matters is the acoustic output from the drivers.
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Old 14th January 2014, 10:14 AM   #3
ashok is offline ashok
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Advice needed: mixed order Linkwitz Riley crossover
The electrical slopes alone don't mean much. The combined electrical and driver response should have the slope you are looking for. So you need to measure the acoustic response.
But , yes, I think the slopes at the crossover points should be similar for it to add up as predicted. If slopes are different the phase will also be a problem. But the electrical slopes could be different for LF and HF as long as the acoustic output of the drivers is what you are trying to achieve. Depends on each drivers response and where you cross them over.
But as I said you could get a 24 dB slope with an electrical slope less than what you want because the driver also contributes to it.
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Last edited by ashok; 14th January 2014 at 10:16 AM.
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Old 14th January 2014, 08:48 PM   #4
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by Zoodle View Post
Can I mix orders within a 3-way LR crossover (EG tweeter slope: 24db; mid-range slope(s): 12db; bass slope: 24db)? Or will I mess up the benefits of the LR system? (IE the phase constancy across the freq range).
I'm not sure what you're trying to do, which ESP circuit you're trying to use and what your skill is.

But you seem to think about transient perfect (minimum phase) crossover, specifically the Duelund 3-way.

Of course you can mix the slopes. The LR benefit that you miss is the flat summation at xo frequency, not the phase. But with active xo, the non flat response can be easily equalized.

If you're using passive xo, there's similar way to do it but it seems not what you're looking for.
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Old 14th January 2014, 08:56 PM   #5
tinitus is offline tinitus  Europe
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Quote:
Originally Posted by Jay View Post
I'm not sure what you're trying to do ...
sounds to me like it is about active xo

many seem to forget all about acoustic slopes when doing active crossovers
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Old 14th January 2014, 10:55 PM   #6
Absconditus is offline Absconditus  Australia
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Quote:
many seem to forget all about acoustic slopes when doing active crossovers
For the most part you can if you select drivers which have a FR outside of the active crossover slopes. THAT is only one of their many advantages.

@Zoodle, I suggest going with the 24dB slopes unless there is a very good reason to do otherwise. Is there one?

Abs
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Old 15th January 2014, 12:07 AM   #7
sreten is offline sreten  United Kingdom
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Hi,

For the most part you can get it cluelessly wrong using
active electrical L/R crossovers, which are best left to
active PA *, and basically just very poor for real hifi.

rgds, sreten.

* Because in most cases they work much better
than the god awful 8 ohm PA crossovers used.

Last edited by sreten; 15th January 2014 at 12:16 AM.
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Old 15th January 2014, 12:10 AM   #8
Zoodle is offline Zoodle  Australia
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Thanks all. Since yesterday I found out that for the Linn active crossover, they crossed bass to mid using 12db and mid to high at 24db, which is different to what I suggested earlier. However, the mid has both a 12db and 24db slope, so wouldn't there be a 180 degree mismatch, somewhere?

On the Linkwitz site I found this: Frequently Asked Questions A sentence there suggests why Linn may have chosen 12db for the bass to mid. BTW, I'm using the Kef B110 and B139, the same drivers for which the Linn crossover was designed.
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Old 15th January 2014, 12:26 AM   #9
sreten is offline sreten  United Kingdom
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Hi,

Here is a design that uses second and fourth order
acoustic L/R slopes : Zaph|Audio - ZDT3.5
Note the driver phase is correct at both x/o points.

rgds, sreten.
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Old 15th January 2014, 01:52 AM   #10
CharlieLaub is offline CharlieLaub  United States
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To answer your question, asymmetric slopes don't matter at all.

Don't bother looking at the literature for "the best" crossover type. All of these studies assume that the driver has an infinite passband and a constant phase of zero. Once you throw the driver(s) into the mix, all bets are off.

What is important is to get the output from the drivers that operate together within a crossover region operating in phase and with matched amplitudes (SPLs). What comes out of the driver is the sum of the electrical filters and the driver's own response. Since the driver's own response and the cabinet edge diffraction all influence the amplitude and phase responses these must be included as well. Where the responses are measured is also important. You can get a crossover to sum nicely at one point in space only, because as you move away from that point the relative phase of each driver changes and eventually there will be interference of one kind of another. So where you plan to listen to the speakers relative to their front baffle should also be taken into account.

I usually do some extensive modeling to plan out the loudspeaker and look for issues. Once I have the driver layout and cabinet size/shape figured out, I build the cabinet, install the drivers, and then take lots of measurements. I mean LOTS. On axis, off axis, driver in pairs, nearfield measurements - all of these are important and used in the crossover design in one way or another.

Once you have all the measurements, you can use a comprehensive crossover design tool/package/software to design a crossover that really works as you intend it to. These do not need to be commercial by any means. There is an excellent free passive crossover design tool built in Excel called "Passive Crossover Designer" by Jeff Bagby. I created an active crossover design tool called "Active Crossover Designer" that also uses Excel. Both of these are complicated programs but you can find lots of support for either one in DIY forums (I'm happy to answer questions).

There are some who suggest that you can develop a crossover without any measurements, but I think that this is often a waste of time unless you really know what you are doing.
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