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How to tune a crossover please?

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  • billfitzmaurice
    replied
    I've never seen a complaint from a Drive Rack 260 owner, nor PA2 for that matter.

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  • frustrated
    replied
    Thanks guys. Next, I have asked a few people who have used both digital and Analog crossovers and I had asked specifically about the Driverack 260 and a BSS FDS388 and was told the DBX does not even come close to the BSS, that one will get better quality sound with the bss or the more expensive crossovers like Lake, RCF e.t.c.

    Thing is, I have heard one bass tuned with both a BSS FDS388 and an Ashly XR1001 and I could not tell the different between the two so I don't know about the higher end digital crossovers giving better quality sound, what's the opinions of both situations above for you guys here please?

    I gad also asked a DBX Tech the question of the DBX 260 vs the BSS 388 and these were his words

    "Most people running the DriveRack 260 are pretty impressed with the quality. I have not heard one complaint. I’ve never really done a shootout between those two models, I mean some people swear by the old BSS Signal Processing equipment and of course it has some benefits like the multiband compressor for example we discussed earlier.

    I guess what you get with the 260 is that it is a still serviceable product that is in production still, that is another benefit. At it does, loudspeaker management, you can’t really go wrong tbh.

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  • billfitzmaurice
    replied
    FWIW most of the pros who regularly post on my forum use 48dB slope if their crossovers allow it. They can do so because a good DSP employs linear phase filters that eliminate phase shift issues.

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  • Paul O
    replied
    To highlight certain items in a recording is difficult, if the recording engineer wanted that instrument to be prominent at that time he would have raised the instruments level in the recording. The best you can do with a finished recording is boost the frequency range of the instrument with a parametric EQ, but if there are other instruments or sounds in the same range they will get boosted too so it doesn't work quite as well.

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  • frustrated
    replied
    Ok so from what I have learned so far it appears that a Digital crossover has advantages over an analog, I will get to this in a a few. Meantime, if I wanted to hear specific instruments highlighted "in a horn" in particular, like violin, hi pitched cymbal or wind chimes, how might I go about getting those results please?

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  • Paul O
    replied
    With most digital processors you can set all parameters differently for each filter if you want, but they also allow settings to be mirrored to a second channel if you are doing a stereo setup for example.

    Steeper filters offer more protection but also add more phase shift.. that is the catch with all of this, and phase shift is difficult to deal with as it tends to not behave linearly... it varies with frequency. Digital processors often can adjust for phase shift at the crossover frequency but that doesn't fix the problem everywhere so often a compromise is made and we use a medium filter slope like 4th order(24db/oct) to get good out of band rejection without too much phase shift. An added benefit is that even order filters sum flat and a generally flat response is the target anyway.

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  • frustrated
    replied
    That link is indeed a very detailed account [thanks] but in all honesty a little too technical for me to grasp all of its concepts, right now at least. So would one be able to set separate slopes on a digital crossover for high pass and low pass or only one slope setting allowed?

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  • billfitzmaurice
    replied
    Analog active crossovers have adjustable frequency but not slope. The advantage to higher slopes is better protection for high frequency devices and less pass band overlap of the driver outputs. This site explains how crossovers work very well. It speaks specifically to passives, but again, actives do the same thing, except being located before the amps they don't affect the speaker impedance. http://www.bcae1.com/xoorder.htm

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  • frustrated
    replied
    Great, making a lot of progress. Reading up on and watching videos of DB and slope settings:

    The slope is the rate at which the signal rolls off or attenuates past the crossover's frequency. Slopes are set in 6 dB increments with 12 dB, 24 dB and 48 dB slopes being the most common and used in many amplifiers with variable or set crossovers. Higher end DSP tuning processors such as the TwK™ 88 and TwK™ D8 include 6 dB, 18 dB and 36 dB slopes for more advanced tuning. The higher the decibel, the steeper the slope on the crossover.
    I am guessing that one can only choose the slope settings with a digital processor and not an Analog unit?

    Also I am having trouble understanding how the slope or roll off translates into the sound you hear, can you guys explain this aspect for me please? Meaning if I should set a digital processor to 12db then try another setting at 48, how would that affect the sound I am hearing or what should be the difference I should pay attention to in what's coming from the speakers?

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  • billfitzmaurice
    replied
    Users of my horn loaded subs routinely set the low pass frequency lower than the high pass frequency of the mains What matters is the summed response of sub and main, with horn loaded subs this is usually the best way to get flat summed response, as they have higher sensitivity with increasing frequency.

    I had thought it was referring to an active crossover.
    Active and passive crossover do the same thing. What mainly differs is where they are in the signal chain. Active is before the amps, passive is after the amps. Active allows using a separate amp for each frequency pass band, passive uses one amp. Active allows easy manipulation of the filter frequencies and slopes, passive has fixed values.

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  • Paul O
    replied
    Originally posted by frustrated View Post
    I think I got a better handle now. I had thought that each separate speaker would require it's own frequency knob and setting so for example a 5 way setup would have required 5 frequency knobs with each having their own settings
    With analog crossovers at least there are always 1 fewer crossover frequencies than speaker bands, so a 2-way speakers system has 1 crossover frequency, a 3-way has 2 crossovers, a 4-way has 3 crossovers, etc.
    With a digital crossover it is often possible to set each filter individually allowing for more complex configurations.

    Maybe a few definitions relative to audio applications would help.

    Filter: An electronic circuit or algorithm(in the digital realm) that affects the frequency response of a signal. Filters come in many flavors, they can boost or cut a range of frequencies like an EQ control, or they can roll off or boost frequencies above or below a certain corner frequency.

    Crossover: A pair of roll off filters that when ganged together produce a smooth acoustic "crossover" from one speaker driver to another.

    Originally posted by frustrated View Post
    So this tells me guys that both frequency knobs should not be set to the same exact setting, that it would depend on each speaker's frequency response requirements, is this correct please?
    No they would not be set at the same frequency obviously, but it depends on more than just the speakers frequency response, driver protection and a bunch of factors that affect optimum sound quality are also a factor. For example most woofers have a published response that ranges from somewhere below 100hz up into the khz range but they are seldom used over such a wide spectrum in a speaker system, their low frequency response will be excursion limited and the cone tends to create a lot of distortion and has a narrowing output pattern at higher frequencies, so crossovers are used to limit their output to perhaps something like 80-1.5khz. Same applies to high frequency drivers, the response might extend down to 500hz or lower but they would have a very low power handling capacity and would be easily damaged if used that way so a crossover is used to limit their output to perhaps 1.5khz and above. There is also a hugh range in what classifies as a "high frequency driver" too, some can operate safely down to 500hz but others can't safely be used below 5khz so as already mentioned, everything depends on the drivers being used.

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  • frustrated
    replied
    Originally posted by Paul O View Post
    OK I understand your confusion now, the article describes 3 crossover filters which would be used when building a passive crossover. .
    Oops, my mistake then [sorry], thanks for clearing that up as I had thought it was referring to an active crossover.


    I think I got a better handle now. I had thought that each separate speaker would require it's own frequency knob and setting so for example a 5 way setup would have required 5 frequency knobs with each having their own settings but from this screenshot I can see that in 3 way mode there are only 2 frequency knobs with each one sharing the Mids frequencies:

    https://i.postimg.cc/JzYjfm8x/Screen...2-17-32-PM.png.

    So this tells me guys that both frequency knows should not be set to the same exact setting, that it would depend on each speaker's frequency response requirements, is this correct please?

    Leave a comment:


  • billfitzmaurice
    replied
    Originally posted by frustrated View Post
    if I should have 3 separate speakers, one sub, one mid woofer and one horn, which frequency settings would I be using for each of the 3 frequency response knobs on any active crossover please?
    That depends on the speakers being used. The crossover between subs and mains will almost always be in the 80-100Hz range. The crossover between midbass and high frequency driver could be anywhere between 500Hz and 5kHz.

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  • Paul O
    replied
    OK I understand your confusion now, the article describes 3 crossover filters which would be used when building a passive crossover. Analog active crossovers do it a little differently, those 3 filters are combined together in such a way that there are only 2 crossover frequencies in a 3-way setup. The upper crossover for the LOW band and the lower crossover for the MID are at the same frequency, and the upper crossover for the Mid and low crossover for the HI are at the same frequency, that is why there are only 2 frequency controls on a unit like the Ashly xr1001.

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  • frustrated
    replied
    I am not referring to any particular system, just trying to understand what I am seeing in the DIY article mentioned earlier.

    https://i.postimg.cc/c6G4WBwc/Screen...8-24-59-AM.png

    Sorry the screenshots are not uploading directly into my posts.

    So that article is showing 3 filters, my question is if I should have 3 separate speakers, one sub, one mid woofer and one horn, which frequency settings would I be using for each of the 3 frequency response knobs on any active crossover please?

    Leave a comment:

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