Introduction to designing crossovers without measurement

[jim1961]

Originally Posted by AllenB

If you would like to pose this on your other thread I will help you through using the online calculators and see if I can show you an example of dealing with breakup without resorting to a notch filter.

I thought id opened the discussion there to not only notch filters, but more fundamentally to dealing with cone breakup. If there is more to say on that issue, I invite further comment.

Now, I didnt chime in on this thread just to further my cause on the other thread. I felt since notch filtering was part of the introductory framework. Knowing how to derive what components you need through knowing the parameters of the peak ( I suppose the center freq, the -3db points, and its depth) would be very helpful. I have looked for such a tool and havent found one yet (for the series notch filter anyway).

[AllenB]

I see your point. I thought long and hard about whether to include notch filters here and finally I decided against it. Since they can often be avoided with wise crossover frequency choices, driver choices and tweaks to normal filters, their potential complexity seemed unnecessary. To know whether to choose series or parallel, where to put them and why to use them, to understand its (varying) effect created by the existing crossover and to understand (and compensate for) its (varying) side effects against the existing crossover, would have warranted its own tutorial.

[mikeyhamm]

That was excellent stuff AllenB. Your tutorial explains a lot about building speakers plus its crossovers design [very easy to master Maths], etc, even for a beginner like myself. I learn more from your tutorial than any other speaker building book.

Thank you very much.

[devilsindetails]

Terrific Post Allen B.

Reflects the the very best of what DIYaudio needs to be for the novice, those less experienced and the naturally inquisitive...accessible, illuminating and well-tempered. Thanks so much for your gracious work! Leon

[gopib]

Thanks Allenb. This is just what I was looking for as I am starting my first ground up build. Terrific stuff here....

[PRTG]

Hey, some important stuff is missing here! Phase alignment!

[AllenB]

Then you'd know the depth and the limitations on that subject. I believe a speaker can be built without measurement. I was hoping to show that here.

[PRTG]

AllenB, you're right. Your tutorials add a lot to general understanding of what can be changed to achieve particular corrections in speaker response.

Still I believe that to achieve results close to excellent we must align phase first and then see if we need any further tweaking at all. So I created alternative tutorial for those who'd like to take a somewhat more complex but in my opinion more rewarding path. It involves measurement so I started it as a new thread here

[AllenB]

Yes, with measurements it can be taken further indeed, although I disagree with the value to this extent of phase alignment at this early stage of the game.

During the '80s I wrote some software which I used to precision align phase between drivers, but it didn't bring me satisfaction after several attempts. I learned that while phase aligns at one place, there is a room full of sound that needs to be accounted for at the same time. This will limit the ability of phase alignment on-axis as being able to either make or break a speaker's response. Phase distortion, of itself, has also been shown not to be a major factor.

What matters in the end is the frequency response. This of course is phase dependent in the direct field but this then becomes virtually irrelevant by the reverberant field. At this early stage of the game, it is within the realm of being judged by ear or using a broad frequency response measurement.

All the best with the next step, PRTG, I'll drop by next chance I get.

[DennyG]

Q1: Do the DC resistances of the inductors need to be considered?

Q2: How do you accommodate a speaker with an impedance curve in the relevant frequency range that is not flat, eg a midrange driver?