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Multi-Way Conventional loudspeakers with crossovers

Freq measurements and Hypex Filter Design adjustments
Freq measurements and Hypex Filter Design adjustments
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Old 30th July 2019, 10:25 PM   #121
CharlieLaub is online now CharlieLaub  United States
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Quote:
Originally Posted by denibeni View Post
If you think that a high impedance network (like a passive crossover) between the amp and the drivers is not spoil the driver's Qes, then i don't know what to say.
Question: What passive crossover has that kind of in-passband impedance???

Answer: None! So dont' crap your pants over some ridiculous BS sentiment that a passive crossover is a "high impedance network" ! You are totally wrong on this point.

What I can say is that "high impedance" compared to, say, an 8 Ohm driver is on the order of 100 Ohms or higher.

At best a junky low cost crossover will put a series resistance of at most 1 Ohm in series with the driver. That's still at least several times less than the DC resistance of a home audio driver. Could have an effect e.g. a poor damping factor? Well, OK, in the worst case scenario, maybe. Does it typically have an effect? Not typically, when the crossover is properly designed. Are we properly designing crossovers as DIYers? You betcha.
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Old 31st July 2019, 12:12 AM   #122
AllenB is offline AllenB  Australia
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From a highly qualified forum member.
Quote:
Originally Posted by gedlee
After having my bi-amped system for about a year, I am canning the active system and going back to passive. The differences are just not that great that it is worth all the trouble.

So, if you are a newbie who cannot make a complex passive crossover, then DO go with DSP (MiniDSP is ideal). But if you can do both just about as well, then the ease of passive is hard to pass up.
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Old 31st July 2019, 02:06 AM   #123
YSDR is offline YSDR  Europe
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Okay, I may have exaggerated the properties of passive crossovers here and there, so thanks for correcting me.
But this is an active DSP project thread where we can help the thread starter get the best out of his system. If he doesn't like the end result (which is even farther I think), which is almost entirely up to him, he can return to the passive solution. But in the meantime, he was learning how to take advantage of DSP.

Last edited by YSDR; 31st July 2019 at 02:15 AM.
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Old 31st July 2019, 12:29 PM   #124
Juhazi is offline Juhazi  Finland
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Two-way is piece of cake as passive design, but 3-4way systems are really painful and also costly because of the number of components. Also selection of drivers is not so critical with active systems.

There are good basic instructions of how to design dsp-xo with measurements here
Digital Crossover basics
miniDSP tutorials

But in reality making appropriate mesurements is very difficult and it takes time to understand all the aspects. Seems like many people have no idea of even the basic principles and think that this is easy!
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Old 1st August 2019, 06:40 AM   #125
kimmosto is offline kimmosto  Finland
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Quote:
Originally Posted by Juhazi View Post
Two-way is piece of cake as passive design, but 3-4way systems are really painful and also costly because of the number of components.
...
But in reality making appropriate mesurements is very difficult and it takes time to understand all the aspects. Seems like many people have no idea of even the basic principles and think that this is easy!
Are you talking about yourself or what? There's actually nothing difficult or expensive, but of course if you know nothing about designing speakers...
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Old 2nd August 2019, 04:20 PM   #126
Steve2111 is offline Steve2111
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Quote:
Originally Posted by PLB View Post
Hi Steve,

In one of the posts further back I think someone mentioned about the use of a target response. It is at this point that I think a target response would be of most benefit to you, since it will not only highlight the types of filters required, but also indicates the magnitude of some of the parameters of the filters. It is important to remember that the shape of the target curve determines its phase response, so if the acoustic responses don't accurately match the shape of the targets, then the summed acoustic response of the bass and mid-range will not be flat. It is not just a question of getting the crossover at –6dB, it is also necessary to get the phase response correct as well.
In practice, you may also have to apply a delay in the mid-range to account for the acoustic offsets between the two drivers.
To generate a target, just select “Generate Target Response” from the Overlay menu in the FR window as shown attached. It only takes two shakes of a Lamb’s tail and it’s done. Hope this helps.

Peter
Hi Peter
Why Q 0.5 when use band pass or high+low pass for Target curve?
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Old 2nd August 2019, 05:45 PM   #127
PLB is offline PLB  United Kingdom
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Hi Steve,

The low pass filter section of an LR4 crossover is made from two Butterworth second order (BW2) low pass filter sections. The Butterworth filter has a Q = 1/sqr(2), so when 2 of them are connected in cascade to form an LR4, the combined Q = 1/sqr(2) x 1/sqr(2) = 0.5.

Please note that the Q of a 2nd order filter uniquely defines its magnitude and phase relationship and therefore an LR4 crossover cannot be constructed from a Q combination of 1 x 0.5 for example, because the unique magnitude/phase relationship will not be maintained. Hope this helps.

Peter
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Old 2nd August 2019, 06:24 PM   #128
Steve2111 is offline Steve2111
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Well no idea. But as I am going to be using LR's I'll just use Q = 0.5 ( I actually would prefer LR8's or even steeper, but would most prob lead to other complications?)
Again for Target curve there is option Band-pass or High+Low-pass. I thought they were the same thing
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Old 2nd August 2019, 09:08 PM   #129
PLB is offline PLB  United Kingdom
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Hi Steve,

Can you take your curve in post #96 and generate the target curve I show in post 98 and post result. Don't worry about the other types of target curve at this moment.

Peter
Attached Images
File Type: jpg NEARFIELD.JPG (364.0 KB, 81 views)
File Type: jpg Target curve.JPG (125.8 KB, 86 views)

Last edited by PLB; 2nd August 2019 at 09:11 PM.
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Old 2nd August 2019, 09:15 PM   #130
CharlieLaub is online now CharlieLaub  United States
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Quote:
Originally Posted by PLB View Post
The Butterworth filter has a Q = 1/sqr(2), so when 2 of them are connected in cascade to form an LR4, the combined Q = 1/sqr(2) x 1/sqr(2) = 0.5.
Rubbish! (Sorry I just love saying that saucy phrase). I want to point out that there is no such thing as "combined Q" for a fourth order filter. Up to that point, you got it right PLB. The "Q" is inversely proportional to the "damping" and is a characteristic of second order functions only. The "Q" value describes the behavior where the filter enters the transition band (e.g. where it starts to "roll off" in the common parlance). I'm sure you know that PLB, that's noted for others who are reading this post.

The Linkwitz-Riley fourth order filter is formed from two second order Butterworth filters, connected in series and having the same corner frequency as the desired LR4 corner frequency. So, that's two second order Q=0.707 filters with identical corner frequency.
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