Frequently Asked Questions

Some ramblings of mine will appear below.  Some of this is controversial.  You can get opinions on the internet telling you whatever you want them to tell you.  The opinions below are mine using my logic and my testing.  

QUESTIONS AND ANSWERS

Q:  I am building some speakers and I want you to build a pair of crossovers for this speaker.

A:  Man this question comes to me all the time.  Usually starts out with something like:

I have these drivers I want to use and will be building a cabinet…… or, I have this old pair of speaker cabinets and want to replace all the drivers with modern ones…. or, I have all the horns and drivers from some speaker but want to put them in a much smaller cabinet…. or, I have a pair of Klipsch cabinets with no drivers and want to use this woofer, this midrange and this tweeter.

All of these cases would be a new speaker.  No one can build you a crossover without doing a lot of testing on the exact drivers in that exact cabinet.  Knowing how those drivers work in that cabinet will provide the information on how to design the crossover. 

So, let’s briefly go through how we work out a new speaker.  Let’s say that we have selected a woofer and have used the basic specs of this woofer to come up with a cabinet and how to port the cabinet.  Then the next step is to build that cabinet and with the woofer in that cabinet we can measure the output of this woofer it the cabinet with the porting we have selected using a spectrum analyzer.  This is a good time to also see if adjusting the port some gives an improvement.  At the completion of this, we can look at the spectrum analyzer results to see how we should match up a midrange to it.  If for instance we see a relatively linear response to 800hz, that is our first clue on what midrange we should look for.  We want a midrange that can operate relatively linearly from about 800 hz to some point that we can select a tweeter to carry on above that and an output at least as high as the woofer output.  Usually this output is quite bit higher than the woofer and we can adjust for that in the crossover.  

Next we measure the output of the proposed midrange and see that in fact it will take over at the 800hz frequency we have already determined and that it’s output is equal or higher than the woofer output.  

Then same measurement for the proposed tweeter.  It has to take over inside the range of the midrange and go on up from there.  Again, the output must be equal to or greater than the woofer output.

Now we are ready to design a prototype crossover.  We know by this time the crossover frequencies and the relative outputs of the three drivers.  Normally, we will go with the woofer output being whatever we got naturally and then attenuate the midrange and tweeter both to match the woofer output.

Using the various crossover calculators available on the net, we design and build a prototype crossover.  

Connect up the crossover and then run a curve of the combined drivers operating together and then analyze that curve.  Here is where things get a little murky.  Almost always at this point that curve looks like it could be improved.  That is where we make some changes to the crossover component values with the goal of improving that curve we got with he prototype.  A lot of trial and error in this part.  And, honestly, this is also the point where we discover that our speaker we have worked on for all that time may not be very good.  Sometimes happened.  In that case, you start over completely from scratch.  That has certainly happened to me.

If speaker building was easy, I guess everyone would be doing it.


Q:  Do components have a break-in time?

A:  Some do and some don't.  Capacitors would be a definite NO.  Let's look at this one a bit.  

You have new good quality capacitors installed in your crossovers.  Capacitors have exactly two qualities that effect the sound of your music that goes through them.  Those are capacitance (what we use them for) and ESR.  ESR is the sum of all other qualities of a capacitor other than capacitance expressed as an Equivalent Series Resistance.  ESR is a bad thing.  Good caps have ESR so low it is barely measurable, on the order of  a couple of hundredths of an ohm.  ESR is made up of stuff like the resistance of the leads and their connections to the foil inside the capacitor or stray inductance or dielectric absorption.

So, we put our new caps in the crossovers.  These new caps are right on the capacitance value the design calls for and the ESR is almost unmeasurably low.  What exactly of these two qualities do you expect to change with break-in?  And if either of them changed, why would you expect the sound to get better since the only way they could change is to go away from the "perfect" values they had to start with?  I hope any caps you use in your crossovers are good enough that they do not change at all for many years of use.


Q:  But my speakers sound so bright after putting in the new caps that I have to hope they change with break-in.  In fact I am pretty sure they are getting better as I listen longer.  They must be changing.

A:  Sounding brighter is a good thing.  That means your old caps were really bad and had high ESR.  That high ESR had the impedance all upset on the crossovers and you had the drivers all trying to play at the wrong frequencies.  Also, the high ESR was directly attenuating the high frequencies.  Now with the new good caps, the frequency and level relationships are back to where the factory had them when the speakers were new.  The fact that you think they are changing now is because you are getting used to them sounding like they should.  The break in is occurring but it is inside your head instead of inside the speakers.


Q:  How about break in time for wires and interconnect cables?

A:  None


Q:  How about break in time for drivers or new driver diaphragms?

A:  Yes, and depends on the size of the driver.  Tweeter diaphragm probably break-in at a matter of seconds.  They are very low mass and move very little, so any break in would happen almost instantly.  Probably happened when the factory tested the diaphragm after manufacture.

Midrange are a bit bigger and have a bit more mass.  Break-in is probably on the order of minutes with these.

Woofers would take the longest.  I think that break-in on a 12 to 15 inch woofer would be less than an hour played at pretty good volume using music with a lot of low frequency content.  


Q:  Do different capacitors sound differently?

A:  Good caps all sound the same.  Let's define that term.  A good cap has the value of capacitance we need and has very low ESR (I defined ESR earlier).  A bad cap has either the wrong value of capacitance and/or higher ESR.  If we compare a good cap to a bad cap, we would probably hear a difference.  If we compare two bad caps, they would also probably sound different.  If we stay with good quality polypropylene caps, we likely meet the two qualities we need....right value of capacitance and very low ESR.  


Q:  You say to use a good quality Polypropylene cap.  Why not use the cheapest ones?  There are cheaper caps than the Sonicaps you use.

A:  In testing caps, I look at ESR as a sign of quality in manufacturing.  When testing some of the cheaper polypropylene caps, I see low ESR, but ESR that varies between caps more than I like to see.  I would rather see all the caps measure about the same and very low in ESR.  For instance one popular brand of inexpensive polypropylene caps I have tested varied from about .02 ohms ESR to around .06 ohms ESR in a batch of ten caps.  Now .06 ohms ESR is still a good cap and I consider that to be very low ESR.  But, since there is a variation between the caps, that makes me question the quality of the manufacturing process for those caps.  And since ESR increases with age as a natural part of the aging process, I consider that starting out with very consistent values of ESR when new, is likely to result in the caps staying good (with low enough ESR) longer.  

Testing like that, led me to go with the Sonicaps.  They were the most consistent of the caps I tested.  The manufacturer of these caps tells me that he thinks they may last 50 years.  That is much longer than typical caps have lasted and that will be something for others to verify.  I won't be around that long and neither will the guy that manufactures these caps. But I do like the idea that he was designing in qualities he thinks would make them last longer.


Q:  How do you measure ESR in caps?

A:  That takes an instrument made to measure ESR.  I use a B&K Model 885 LCR ESR Meter.  I also use the Kelvin Clip leads with that.  Cost is about $600.00 for that meter with those leads.  That is the least expensive meter I know of that will really give accurate measurements of ESR.


Q:  I have heard rave reviews of Paper in Oil caps for crossovers.

A:  Pure audiophile garbage.  All the PIO caps I have tested have very high (around 0.5 ohms) when new!!.  I call those bad caps no matter how much someone charges for them.  They have that "warm" sound, people say.  Warm then is defined as the high frequencies being rolled off.


Q:  What do you think of using "bypass capacitors" in a crossover circuit?

A:  Not much.  The theory is that you can use cheaper caps in the crossover circuit and then use a high quality cap of about 0.01uF to "bypass" that cap and impart the "goodness" of the 0.01uF high quality cap into the circuit counteracting the "badness" of the lower quality crossover cap.  First, I really don't like that someone in the cap selling business hijacked a perfectly good electronics term (bypass capacitor) and decided to redefine it's meaning.  A bypass capacitor in electronics is a cap used to bypass AC around a DC circuit.  Now it is being used to describe this idea of bypassing AC around an AC circuit.  

Anyway, at the audio frequencies we use in crossovers and the impedance of the circuit, none of the frequencies we can hear would actually go through that .01uF cap.  So, what could that cap do to the circuit?  I think the obvious answer is "nothing".  Good news is that this would not hurt anything.  I have never heard any reasonable and coherent explanation using real electronics terms of how this cap could help anything.  I think the whole idea was created to sell more caps.  Yes, I am aware that JBL used this trick in a few speaker crossovers for a brief time.  But they were selling speakers.  Some speaker manufacturers set up their speakers in certain ways just because some they sell them to expect it.  Like bi-wiring perhaps. 


Q:  How do I know if it is time to replace the caps in my crossovers or replace the crossovers?

A:  If the caps are over about 20 years of age, it is time to replace them or replace the crossovers.  The caps are the main wear item on the crossovers, so a rebuild replacing the caps gets you most of the gain you could get.  Replacing the crossovers completely, gets you some more gain because everything would be new and higher quality than the originals.

Also consider that for some speaker lines, parts for the crossovers were of lesser quality to start with since this is a place where costs can be cut and there is not an immediate hit on the quality of sound from the speakers.  This applies to the non-heritage lines of Klipsch speakers.  We see that in lots of those, the quality of the parts, especially the capacitors was not up there with the quality we see in the Khorn, Lascala, Cornwall 1, Belle, and Heresy 1.  So, it is good to work on those earlier than the 20 years I mentioned earlier.


Q:  The wires from my crossovers in my speakers (Forte, Forte II, Heresy II, Cornwall II, Chorus, Chorus II, Quartet, KG-Series ETC) use push on clips.  Should I solder those?

A:  No, unless you are an expert at soldering, don't do it.  Lots of drivers have been ruined by doing that.  The wires are connected to very delicate diaphragm connections.  You can very easily melt the plastic that the small metal terminal is attached to by getting it too hot.  If you are an expert at soldering and are sure you can do a good job on soldering these wires to the driver terminals, you should still not do it unless you are planning to keep them for ever.  The next guy you sell them to may not be an expert and he might need to replace a diaphragm some time.


Q:  How can I get more bass out of my Heresy speakers?

A:  You can't improve the bass response very much in those speakers.  The bass response is dependent on the woofer working in the cabinet.  The crossover has little to do with the bass.  To get more bass, the cabinet has to get larger or efficiency has to decrease.  What you have in the Heresy is a pretty efficient (therefore low distortion) speaker in a small size with bass good down to around 60 hz.

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