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kevinmcdonough View Drop Down
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    Posted: 23 February 2024 at 12:48pm
hey all

Although I've designed and built quite a few speakers over the years, I've never really spent much time learning about passive crossover design. I've just run active, or made up a circuit from a pre-existing spec. While I know the basics in a vague sort of way and am watching lots of tutorials and things to learn more, I'd like to get some input and start some discussion on how to take it to the next level. What makes a good crossover a great one?

People like Tom Danley and Ed Kinsella for example are known to design exceptionally high quality crossovers that are a huge step above the norm. What do they do different, what other components are they including, what is it that makes theirs stand out?

I think it would be a great learning opportunity for everyone to have some discussion on this, and link to any resources anyone may have that could give us some insight. 

Annnnndddd, go... LOL


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VECTORDJ View Drop Down
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I use Xsim....Free and works good...VECTORSONICS
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kevinmcdonough View Drop Down
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Originally posted by VECTORDJ VECTORDJ wrote:

I use Xsim....Free and works good...VECTORSONICS

I've saw that one, and I've also saw VituixCAD which looks really useful. 

My question is more about the theory really, rather than trying to calculate specific crossover values. 

Some crossovers have just a few basic components and do the job fine, but some are very big and complicated. The people I mentioned are renowned for making very complex crossovers that have lots of additional components and are seen as little works of art. 

I'm more trying to understand (and start a conversation to help others understand and learn) how/why they are doing this. What do they do differently that makes their crossovers stand out, what extra things are they adding and why?  How do they elevate their crossovers to the next level.

Kev


Edited by kevinmcdonough - 23 February 2024 at 11:33pm
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MarjanM View Drop Down
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There are two types of crossovers. 
Simple one that pretty much only divides the bands and a complex one that actually shape the frequency response.
Both types works well you just need to decide about you approach to the things. You want to correct everything by the dsp (which is still needed) or you want to "fix" as much as possible with the crossover it self.
The complex crossovers do tend to create certain amount of loses because every single element adds a bit resistance in the chain.
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Conanski View Drop Down
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Originally posted by kevinmcdonough kevinmcdonough wrote:

[QUOTE=VECTORDJ]
My question is more about the theory really, rather than trying to calculate specific crossover values. 

Some crossovers have just a few basic components and do the job fine, but some are very big and complicated. 
I'm more trying to understand (and start a conversation to help others understand and learn) how/why they are doing this. What do they do differently that makes their crossovers stand out, what extra things are they adding and why?  How do they elevate their crossovers to the next level.

A basic crossover simply creates separate frequency bands that are safe for the transducers being used, to get really good results with a simple crossover like this requires really really well behaved transducers so in general this just isn't enough to get even halfway decent results with pro audio speakers.
To go to the next level we get into phase alignment, impedance flattening, response shaping, and level matching. To accomplish those things techniques like baffle step compensation, zobel networks, notch and shelf filters, and L-pads are added to flatten overall response and extend the extreme high and lowend response. Baffle step compensation isn't used as much in pro audio because it throws away so much raw sensitivity if used heavily, and because the same results can be achieved with a bit of EQ boost that is redily available in most cases. A really good passive crossover design can get into the ballpark of what is possible with well executed DSP processing but it will never match it, and it will take more time and effort to get those results.


Edited by Conanski - 24 February 2024 at 6:13am
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Conanski View Drop Down
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duplicate

Edited by Conanski - 24 February 2024 at 6:10am
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I've gotten good results using a "simple" passive xover plus 31 band eq to smooth out the response. 

Trying to do everything with a passive becomes a PITA. At best you can hope for 1 or 2 notches, or some attenuation. All that is far more easily obtained with a graphic, or parametric eq. Or DSP board. They are so cheap these days it doesn't really make sense to sweat over designing a (complex) passive anymore.   Smile
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Quote Trying to do everything with a passive becomes a PITA

I agree with this. Simple crossover circuits assume that the load, i.e. the drive unit, has a constant resistive load. It doesn’t.

Imagine building a loudspeaker cabinet for a 12” speaker, and then picking the drive unit at random and expecting it to fit.

If your main aim is learning how to design them, go for it, but for practical systems putting the crossover before the amplifiers is a much better option.

The link below to Elliot Sound has some useful information.

 

https://sound-au.com/lr-passive.htm

 

Quote People like Tom Danley and Ed Kinsella for example are known to design exceptionally high quality crossovers that are a huge step above the norm.

 

It can be done. Just as rowing across the Atlantic is possible, it is far easier, quicker and cheaper to hop on an Airbus; or if you are feeling a little more adventurous a Boeing. Plus, coming back to crossovers, no matter how good the passive crossover is, you could improve the performance by removing it and going active.

 
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kevinmcdonough View Drop Down
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Thank you for your replies everyone Smile

As I said at the start, all of the speakers I've designed and built over the years have been run active, something I'm very comfortable doing. (Hard to believe it's been almost 20 years since I built my first subs and joined this site! LOL)

I've only ever built one passive crossover, for a double 8" + comp top I made, and it was just the very basic kind, everything else was done in DSP.

My question was really just to satisfy my own curiosity, as I'd like to run the 12" wedges I'm currently working on (here) passive so I can run 4 of a single 4 channel amp. I knew I could just run them the same way as the 8s, with a simple crossover and then do some EQ correction etc in DSP, but wondered if going down the rabbit hole of really learning about these far more complex crossovers would be worth it, if the results would justify the time and effort and research etc. 

While at some point I might still do it, I don't have a lot of free time just now and it seems that no, sticking to simple is the way to go Smile

In this case I was wondering if really 
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If you do get into deigning passive crossovers, a knowledge of AC circuit theory, and inductor design would be very useful. Even sticking to basic circuits, rolling your own can be cheaper than using bought ones.

 

During the experimental/testing phase, leave the crossover outside the cabinet.
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try and work with the drivers and consider what their physical roll-offs are. If it looks like you need to do huge amounts of correction in the crossover then you probably need to reconsider the drivers and enclosure. Don't obsess about flat frequency response - you will end up using eq as soon as the speaker is in a real-world room. transient response and lobing are important and can't be fixed with DSP.
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slaz View Drop Down
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Agreed with the "just go active" posts - well most of the time .... but I'd say there's an exception - battery-powered systems like mine, consisting of 2 x FBT Maxx4 - very high quality passive 12 + 1 boxes + 2 options for bass augmentation. These speakers also get used for mains-powered setup (with different amplifiers obviously).

I never took the FBT to bits to check the passive Xover, but I'd be willing to bet its a fairly fancy one. The 12" and the 1.4" are both B&C with FBTdesigned passive Xovers - so top notch - and they sound magnificient with superb vocal clarity. I wouldn't fancy my chances of matching the integration of those passives with DSP settings ! Well at least not without resort to fancy calibrated mics and software ..... 

Aside from that, if using class-D amp modules powered from (say) e-bike batteries or similar - to go bi-amping/tri-amping - you'd want to use lower-power modules for HF, but that would mean sourcing a different supply voltage - which is a right royal PITA :-)
REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON
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