Introduction to designing crossovers without measurement - Page 23 - diyAudio
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Multi-Way Conventional loudspeakers with crossovers

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Old 2nd September 2013, 11:35 PM   #221
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Thanks for the explanations. My biggest concern about the voltage/current phase shift is that I don't want to end up with something that's going to damage my amplifier.

Now, in terms of destructive interference and sound cancellation - I modeled two crossover designs I found on the internet. I used a function generator to create a signal at the crossover frequency for each and hooked an oscilloscope to the high and low pass sections. The 8 ohm resistors represent the driver load. Is there anything that can be determined about which one of these designs is 'better' based on the phase differences in the high and low pass sections?

#1 Described as a 2.2 kHz crossover.

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#2 Described as a 2.5 kHz crossover

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Old 3rd September 2013, 03:00 AM   #222
AllenB is offline AllenB  Australia
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Quote:
Originally Posted by Duritsea View Post
the voltage/current phase shift is that I don't want to end up with something that's going to damage my amplifier.
This is not typical and some speakers are quite reactive. Some mention that certain amps don't work well with some speakers.

If it bothers you then you can conjugate the speaker's impedance to give the amp something easier to work into.

Quote:
Now, in terms of destructive interference and sound cancellation - I modeled two crossover designs I found on the internet. I used a function generator to create a signal at the crossover frequency for each and hooked an oscilloscope to the high and low pass sections. The 8 ohm resistors represent the driver load. Is there anything that can be determined about which one of these designs is 'better' based on the phase differences in the high and low pass sections?
Not necessarily. Firstly, the issue of destructive interference happens at the speakers and the patterns created are based on their configurations in 3d space.

Secondly, the function of the crossover is to act as an intermediary. It needs to fix speaker issues and if the crossover were as 'correct' as what is coming directly from the amp then it wouldn't actually be fixing anything.
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Old 5th September 2013, 07:21 PM   #223
njr is offline njr  Sweden
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Thanks AllenB. I have to say that this is what I have been looking for, for years now.
I've read books, posted qustions and scanned the internet, never once getting an answer to what I consider two rather straightforward questions:
how do i estimate a good startingpoint for a filter, and how do I tweak it?

I have a question (naturally) before hitting that purchase button.

I was originally aiming for first order lowpass and third order highpass. I realize that the actual response could well prove to be 18db roll-off or more, but what do I do if it isn't?
Can I add another component to make the roll-off steeper? Where and what? Or will that require that all parts need to be changed?

I have a vintage compression driver that I want to run with a rather low crossover, but it is also irreplaceable, so I don't want to overload it.

Thanks again, best contribution ever!

NJR
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Old 7th September 2013, 01:23 AM   #224
AllenB is offline AllenB  Australia
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If you do something to compensate the impedance, such as the parallel resistor or using a series RLC across the speaker at its resonance, and assuming you use it within a reasonably flat part of its band then you might get away with a standard filter from an online calculator...then tweak.
Code:
1st order

-C-|
   Sp

2nd order

-C-|-|
   L Sp

3rd order

-C-|-C-|
   L   Sp

4th order

-C-|-C-|-|
   L   L Sp
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Old 28th September 2013, 11:14 AM   #225
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AllenB,

thank you so much for the wonderful info mate. for beginners like me who aspire to building our own speakers and amps, the knowledge you shared as well as the way you explained it makes it possible for us to understand and have a grasp of what lies ahead.

i hope you will not mind if i ask the following questions:
1. your example is for a tweeter/woofer crossover. for a 3-way setup is the procedure the same, meaning, cross tweeter to mid and then cross mid to woofer?
2. how does the crossover affect the individual Sensitivity of the speakers, and how would i find out what the final overall Sensitivity would be?
3. If all three speakers have the same impedance, how would the crossover affect the impedance rating for each and what would be the final overall impedance?

Again, thanks so much for the knowledge, being presented in such a way we beginners can understand and appreciate.

regards,
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Old 28th September 2013, 11:13 PM   #226
AllenB is offline AllenB  Australia
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Hi soundspeed. Tweaking is inevitably a part of this method but as a starting point you would essentially use two of these for a three way. The woofer would be as for the woofer shown here. You can then treat the midrange as if it were the tweeter, matching the sensitivity of the two in the same way.

You can then assume the mid is the woofer and do it again with the actual tweeter. The reason I can see for looking at it this way is because it is often easier/better to use resistors to attenuate a mid or tweeter than it is for a woofer, and all three drivers will need to be brought to around the same level.

The actual circuit for the mid could be a combination of the two, ie: closest to the driver would be the woofer circuit resistor and capacitor, next out would be the inductor. You could then put the parallel resistor from the tweeter circuit across all of this (ie: from the amp side inductor terminal to the negative rail), and use the tweeter capacitor and inductor closest to the amp.

It may be simpler still to instead start by putting the parallel resistor as shown in the tweeter circuit across the mid, and this would partially do the job of the impedance compensation from the woofer circuit as well. In other words just the parallel resistor, then a capacitor and two inductors total.

You should be aware that when you use a highpass and lowpass filter on a driver like a midrange driver, they can interact causing the level of the usable range to increase or decrease. If you want to avoid this it can be better to keep the upper and lower cross points further apart. Like with a driver resonance, one octave is ok, two or three should be good.

Generally speaking if the crossover is simple the sensitivity will be whatever it is for the driver, based on your baffle scheme, and then take into account how much you attenuated it with resistors. Sometimes however a crossover will have a more profound effect on a drivers sensitivity.

With regards to impedance, the simple answer is that a crossover between three 8 ohm drivers will give a total impedance close to 8 ohms, with regions of slightly higher impedance around the crossovers themselves. This should be a reasonable assumption provided you keep the crossover simple and don't go to extremes with the values. Tweaking is fine, but every now and then you might want to give the overall crossover a bit of a reality check.
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Old 29th September 2013, 06:25 AM   #227
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AllenB,

Thank you for the reply. So much information for me to digest and really understand. I can say now - i was hesitant to post a beginner question in your thread, but the answer you posted here has vindicated my embarassment; for where i was planning to go was a complicated route to building a crossover and your answer has shown me the proper and simple way to do it.

many thanks for your generosity.

cheers!
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Old 2nd October 2013, 04:43 PM   #228
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i have a pair of Sony SS-3100 speakers.
i was lucky to find them in good condition here in Romania and i've paid 150 usd for them.
i was planing to move from solid state to tubes and i wanted some speakers with decent components and high sensibility. from what i have read, SS-3100's speakers are made by Mitsubishi/Diatone or Coral (the mid speaker has the Mitsubishi logo on the magnet cover), alnico magnets, etc. and these speakers came to hand when i wa planning all those things.

at first i've changed the crossover capacitors - Elna non polar, electrolytic caps, - with ClarityCap SA - 4,7uF and ClarityCap PX 3,3uf and two 33uF caps per speaker - where i've put a Mundorf MCap and a Jantzen CrossCap.
the sound improved a little, but nothing to die for (the system was already a decent one, with AudioNote 3.1x CD and a fully restored Lafayette LA224B - with AmpOhm PIO, Furutech copper conections, Tungsram NOS tubes - EL84 and ECC83 - and a Mullard GZ34; Tocos Cosmos pot, audio-note signal wires, tone controls bypassed, mundorf mlytic dual capacitor, etc.; audio note lexus interconnect and speaker cables)

then i went further with the speakers.
i've changed their internal cables with audionote lexus speaker wire (a bit better, but not something to really rave about) and finally i've changed the ClarityCaps with Obbligato Film Oil (4,7uF) and Obbligato Copper (3,3uF).
Obbligato made things so much better - dynamics, detail and natural timbres - that i was overwhelmed.

and i would like to ask you if you think that changing the 33uF caps (MCap and CrossCap) with Obbligato Gold Premium of the same value would improve the sound further. i was asking the owner of the store which imports Mundorf, Obbligato and all other exotic capacitors in Romania about this matter and he replied me that those caps should be on the bass circuit and, there, the main element is the winding coil (i hope this is the term in English). and that he doubts that i will have much improvement there.
those 33uF caps cost a bit, that's why i'm asking this question here.
changing those claritycaps to obbligato improved the bass response also. would you recommend this last change?
thank you!

(as you see in the pictures, there is also a 4.7uF cap on the high line of the Tri-Amping section of the speakers. i don't plan to use that line, but i keep that cap there just in case).
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Last edited by gionloc; 2nd October 2013 at 04:48 PM.
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Old 8th October 2013, 09:50 AM   #229
AllenB is offline AllenB  Australia
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Hi gionloc.

The thing is there are three types of capacitor here. Those that are good, those that aren't, and those which are good for changing the sound. If a capacitor isn't having a significant effect on its own then it should sound like other good capacitors.

Adding small amounts of low order distortion is a tool which may balance some speaker issues in a good sounding way. I used to do this with resistor types as resistor distortions (while also small and sometimes inaudible), are more predictable. Using an electrolytic capacitor on a tweeter isn't necessarily going to make it sound bad, in fact some sound good.

Capacitor rolling, as this seems to be known is something of an artform and I don't have any recommendations but I did used to use a certain type of single ended amplifier to create a similar effect.

Last edited by AllenB; 8th October 2013 at 09:53 AM.
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Old 22nd November 2013, 09:12 PM   #230
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A very easy to understand How To.

Thank you AllenB.

If I want to adapt this to a car ambient (changing the sound characteristics), are there some tweaks to do?
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