Introduction to designing crossovers without measurement

Hi Spinifex & Carlthess40,

Thanks for kind words, I really need to make one thing clear - I'm complete beginner when it comes about passive crossover design, I have never done it before this project. I did make couple of speakers trough the years but they were all someone else design.
This time I wanted to grab the Bull by the Horns and see where will I end up...:p

So far these little gems are just putting enormous smile on my face each time I listen to them or look at them... really special sound.

The final crossover I ended up is presented here, I need to say that I changed "correct" values in favour of nicer and warmer sounding speaker as oppose to the flat and lifeless first emulation.

What that means is that I probably do not have anymore perfect phase integration between tweeter and woofer but I really did not like sound of such "perfect" text book match.
What I ended up is Low-pass with classic bass hump to help bottom octave and slight BBC dip in the midrange to ease down and help longer listening sessions.

This is highly personal set-up so I'm not really bothered if is not up to the flat studio standard or if I could drive them with 100 Watts of power without compression etc...
I just wanted something that sounds human and warm but with high dose of musicality - I think I succeeded spot on!

The whole point is to make something valuable ( in musical terms ) for your personal preference, not for marketing reasons!

I really doubt if I could help you in designing crossover for you without running entire cycle as I did with this one and it took me 6 months of my lifetime.
My kind of specialty is building tube amps, not really speakers but I need to admit it is very addictive and satisfying hobby.

I hope that I have answered some questions...
 

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I changed "correct" values in favour of nicer and warmer sounding speaker as oppose to the flat and lifeless first emulation.
This makes sense, and first you tweak around the baffle step to bring the bass into line.

But 'flat' is not necessarily correct, although it should be smooth. Often a downward tilt of the treble is wanted. Typically differing directivities also support variations from flat.
 
Hi AllenB,

Yes, first emulated crossover was kind off predictable sounding, I would say like many commercial speakers, not what I wanted this time... so I went with changing values ( not much ), creating bass hump, mid deep... until I found acceptable sweet spot.
I actually ended up with slightly tilted-up high end - probably because tweeter sounded a bit shy in top octave, once I placed capacitor of sufficient value - all was set " flat " to my ears!

EL84 tubes are gems, they really shine in any configuration ( SE or PP ) as long is enough power for your speakers of course. My last tube amp was SE RH84, but I need more power for these new speakers... maybe PPP EL84 mono block this time...
 
6922's are gems as well. I am using 2 to drive my SS amp ( 75w ). The sound quality is outstanding.
next project is a new crossover for 4 way HPM-900. The midrange and tweeter need phase alignment, mid is reverse connected with woofer and tweeter(s). Woofers newly re-foamed and in perfect condition.
 
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Increasing value of bass shunt capacitor

Allen B thanks so much for your tutorial.

I have SEAS ER18RNX and 27TDFC drive units in 19 litre floorstander cabinets with a Zaph SR71 crossover. The speakers have to be fairly close to the back wall and this resulted in a rather heavy balance with a muffled midrange.

Zaph gives details of a reduced BSC crossover (this reduces L7 to 2.5 mH and R0 to 3 ohms) which certainly made things clearer, but the midrange was now much too forward and fatiguing. Looking at post 13 of this thread about increasing the value of the bass shunt capacitor I put a 2.2uf in addition to the existing 12uf (C9) and changed the tweeter resistor (R0) to 3.5 ohms This improved things but I really need to increase C9 a bit more.

My question is if I do this will I mess up the crossover? The inductors I fitted are quite expensive and low value caps are comparatively cheap.
 

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Yes, walls are great when the speaker expects them but they are the worst otherwise. Comb filtering is difficult to deal with (random appropriate image). The result varies with angle. A null isn't something that can be undone with a change in level, and it's also a high Q effect.

An acoustic solution might be the easiest and most successful. This includes extending the baffle or using absorbing material in the reflection region.

As far as your filter, yes that will be fine. As you increase the capacitance you lower the cross and increase the response around the 'knee'. This is a gentle increase until the Q of the filter approaches and exceeds 1. The capacitance will be closer to 40uF by that time. Hopefully you can find something that works at a more gradual level than that.
 

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Thanks for the quick reply. I've thought of a supplementary question. Would I be right in saying that the shunt capacitor affects the roll-off of the bass driver in a different way to the series inductor? By this I mean that with an increase in the inductor value the sound can end up a bit muddy and dull, whereas increasing the capacitance seems to have more effect on the upper midrange nearer the crossover.
 
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I'd agree with that. Increasing inductance reduces the filter Q (changes the response vs frequency around the filter knee), and increasing capacitance increases it. This is the same for the tweeter circuit despite the fact that the C and L are in different locations there.

This image shows response vs frequency around the knee of the filter. Your original filter is around 'yellow'. You are moving towards brown, but not there yet.
 

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Help with crossover, please...

Couldn't find replacement drivers for Wharfedale E90's, because of a huge aluminium frame size of original 10 inch woofers. I made hole a bit bigger to accommodate 12 inch Dayton PA-310 woofers. Original woofers where 4 Ohm - Dayton's are 8 Ohms. They could be a bit louder to better balance with the rest. What would I have to change on the crossover to gain a few dB?
Thank you!
P.S.
I'm going to bypass LOW Selector, so Inductor L1 should be ignored since L1 and C1 will be bridged.
 

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I would turn the mid and treble level down. If this isn't enough I would put resistors across the mid and treble drivers. This would be a good idea anyway because R10 and R11 are already large. If you need more, increase those resistors in the switches.

Since the default is to have the woofer at max level I would tend to agree with you about L1 and C1, but they are interesting. They are intended to do some response shaping depending on your level choices but now the levels are being forced. They would cause some reduction in the woofer level with its middle point around 400Hz.

L7 is also only double L4, so its effect is worth considering. With a resistor in parallel this would give a shelving effect, a step with lows at one level and mids/highs at another, lower level with a slope in between. To some degree it would also be lowering the frequency of the filter that includes C6.

This is the thing when it comes to variable level controls. There are a couple of ways to do it. Either you can arrange components to isolate and preserve the driver response shapes, or whenever the controls are adjusted everything will be uniquely different.

With regards to the woofer, L5, C5 and R12 are reducing the level around 200Hz. It's hard to say whether this is to correct a driver issue, adjust for the baffle or something else. Could be worth temporarily shorting.

When it comes to the filter components L6, L3 and C2, for the 8 ohm woofer, double the inductors and halve the capacitors.
 
Thank you for quick reply!
It kinda hurts to kill overall sensitivity... I have these E90's stacked against Klipsch RF-7 and RF-7's are just a tiny bit louder. For now I'm using parametric equalizer in Yamaha RX-A3070 to correct the issue.
I'm gonna try shorting L5, C5 and R12, as you suggested and see what it does.
As for L6, L3 - L3 is already 10.0mH. 20mH is huge in size and also expensive... Is there any way that I could use the old one's and add to them? Parallel? Series?
The picture I attached illustrates what controls are supposed to do - you were right on the money!
Thanks again!
 

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Increasing value of bass shunt capacitor

Allen B

A bit of feedback on my query in post 709.
Adding a bit of extra capacitance worked a treat. I only needed to replace that 2.2uf with a 3.3uf and minor tweaking of the tweeter resistor to effect a cure. Thanks for your encouragement.