# how important is it to keep x-overs out of the sensitive hearing range?



## jeremy7 (Feb 7, 2008)

I've heard a few times that it's benificial to keep the x-overs out of the range of say 300-3000 where the human ear is most sensitive. Now, very often particular projects incorporate drivers that need to be crossed in this range. So, I think the issue is how benificial is it?, and can this idea be ignored if quality drivers are used with a well designed x-over? I know that some very respected high end loudspeakers cross in this frequency range. Ive noticed many x-overs between 2-3k.
Does anybody hane any thoughts on this?


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## Geoff St. Germain (Dec 18, 2006)

I haven't specifically listened to speakers with crossover points in this range for any sort of problems. I would imagine that if the crossover is well executed that it shouldn't be much of an issue. Like you said, some well respected and well reviewed speakers crossover in this range and people don't seem to point it out as being a problem. The KEF Reference 207/2 crosses in this range (twice), though near the edges (350 Hz and 2.3 kHz) and every review I've read of that speaker has been outstanding.

You might get down to some personal preference issues on this, as you see with some people preferring 3 and 4-way speakers and others preferring single driver full-range speakers.


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## BoomieMCT (Dec 11, 2006)

I would say this is mostly personal preference. That being said it is *my* personal preference. I tend to like speakers with a tweeter crossed above well that range, a woofer (almost sub woofer) crossed well below with a good quality wide range driver handling the bulk of the work. That isn't to say I don't like speakers designed differently (I do), just that that is my "ideal".


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## mlwebb (Feb 2, 2008)

Jeremy, most of the well regarded speaker designs I have looked at, and the one I built (JonM's MTM), have crossovers in that region. More important than the crossover point (IMHO), is not stressing the drivers (the tweeter on the low end), and suppressing any woofer breakup, on the high end. But its a good question, and I will be curious to see if there are other opinions (perhaps more knowledgeable than mine).


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## drf (Oct 22, 2006)

I tend to think there is merit in crossing higher or lower than 300-3000, however as pointed out earlier, if the drivers cross best inside this region then crossing higher/lower will only do more damage than good.


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## nova (Apr 30, 2006)

I love my speakers,...they are not DIY, but the do have x-overs at 2700 and 100. I believe this is due to the drivers' aluminum cones. I know very little about speakers design, and even less about crossovers, but I'd imagine driver design would dictate the crossover. I don't think you could ignore it cause the driver may need it.


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## Jason Schultz (Jul 31, 2007)

Hi Jeremy 
I Have tried to Design a speaker that crosses outside the 300 - 3000Hz region in the hope that vocal sounds would be more natural (I was convinced by this line of thinking too) After many hours looking for suitable drivers for this purpose I noticed a few things 1/ Drivers that perform fairly flat through the 1-3 KHZ region are usually small, around 5inches or less and are not very efficient. So you would need to use multiples of them to acheive a decent SPl. 2/ Drivers that are a little larger but can still be used Have peaky resonances in the 1-4 KHZ region and need special notch filters to suppress these. There are some good old polypropylene or paper cones that can do the job but they are getting hard to find. Check out the Vifa p17 wj driver. some good kits have been with these in the past. Its quite flat from 150 to 3000 HZ. Hope this info helps


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## jeremy7 (Feb 7, 2008)

Jason Schultz said:


> Hi Jeremy
> There are some good old polypropylene or paper cones that can do the job but they are getting hard to find. Check out the Vifa p17 wj driver. some good kits have been with these in the past. Its quite flat from 150 to 3000 HZ. Hope this info helps


Yes this does help.
Its funny you mentioned the p17. I was actually considering the p13. It appears to be the 5" version of the p17. I was going to use the p13 because of the smaller diamater. If size wasn't an issue I would go with the p17. My intentions were to cross it at around 120hz and then hopefully cross again at around 2700hz-3200hz. i heard good things about both the p13 and the p17 "flat and natural". The p13 has the same efficiancy rating, but handles only a little over half the power. I was hoping to use the p13, as boomiemct mentioned, to handle the majority of the work load. If I put these into an mtm configuration with a sub, do you you think they would be sufficient? Or does any anyone else have any other opinions? I haven't chose the tweet or sub yet


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## BoomieMCT (Dec 11, 2006)

jeremy7 said:


> Or does any anyone else have any other opinions? I haven't chose the tweet or sub yet


Depends - what is your budget? 

On the cheap side I've had some good experiences with some of the Tang Band and Hi-Vi wide range drivers. For more money CSS has some 4.5" drivers that look promising. Most of the drivers I'm playing with here are 3" - 4" so, depending on your application, you may need multiples of them.


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## jeremy7 (Feb 7, 2008)

On this particular project I was hoping to keep the midbass drivers under $70 a pc. I think the vifa p13's are just under $50


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## JCD (Apr 20, 2006)

No expert, but from what i've seen/heard, most 2 way designs can't help but have their crossover in that area. I've heard this is one of the advantages of an active crossover -- bypassing a passive crossover and all their related quirks.

Not sure if that helps much, but that's what I've heard.

JCD


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## BoomieMCT (Dec 11, 2006)

JCD said:


> I've heard this is one of the advantages of an active crossover -- bypassing a passive crossover and all their related quirks.


I'm not sure how an active crossover will help a driver play a wider range.


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## avaserfi (Jul 5, 2007)

There are many different factors that can play into this situation. Ideally it shouldn't and doesn't matter where one crosses over the drivers, but issues arise with improper implementation of a crossover. This poor implementation is why there are irregularities of frequency response, phase, impedance etc...occur in a loudspeaker's response which would likely cause a lessened listening experience. 

The reason why use of an active crossover can alleviate some of these issues is not because they extend a drivers usable range, but because they easily eliminate much of these issues if a quality unit such as the DCX2496 is used. Use of a unit such as this not only allows for a more dynamic system (due to active amplification), but also easier integration of drivers without various artifacting often found in passive systems that is sometimes unavoidable (assuming proper use of DCX unit).


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## drf (Oct 22, 2006)

BoomieMCT said:


> I'm not sure how an active crossover will help a driver play a wider range.


It's not so much about the range, but about other aspects of passive filters like impeadance matching and thus no requirment for zobel networks, it also eleviates the need for driver sensitivity compensation which if not implemented properly can cause more headaches.


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## terry j (Jul 31, 2006)

JCD said:


> No expert, but from what i've seen/heard, most 2 way designs can't help but have their crossover in that area. I've heard this is one of the advantages of an active crossover -- bypassing a passive crossover and all their related quirks.
> 
> Not sure if that helps much, but that's what I've heard.
> 
> JCD


I've debated whether or not to stay out of this thread, but when a quote like this comes along (and with others response to it) it gets very hard to stay quiet.

I have just had the most amazing revelatory weekend in hi-fi you could imagine. I will not gush, I'll try and stay calm and refined, so read what I say with the knowledge that if I could I would be preaching.

I too have read the comments about keeping the x-over point out of the 'sensitive midrange'. As I use the deqx (the main reason I was going to stay out of the thread, very few would ever consider such an expensive item) it is a simple matter to set the x-over points (and slopes) you desire.

So, I applied the 'conventional wisdom' and had the x-over points of 300 and 3000 hz, and just for good measure applied the slopes of 150 db/oct.

W/out going into system details, yes I had a _very_ good system indeed.

Now, as it just so happened, I was fortunate enough to have the deqx technician come out and stay the night last w/end, the family were overseas and so we had...a loud boys night out??

Anyway, he re-measured the speakers, re-0did the correction filters (and what is appropos to this thread ) he changed the x-over points to 200 Hz and 1650 hz.

Now, there were a lot of simultaneous changes here, but......I am simply unable to get across to you the magnitude and character of the changes. A lot of the difference was indeed due to the x-over points, gpoing lower allowing the extremely wide and even dispersion from the tweeter.

agreed, apart from the deqx it is impossible to get the steep slopes (which allow low x-over points) and with corrected phase blah blah blah.......just let me say that the 'rule' of keeping x-over points out of the midrange is an analog/passive concept.

OK, no deqx then maybe it is a good rule. It most certainly led me up the garden path when erronously applied to the 'new world' now available in stereo.


As I say, this is probably only an 'interesting backdrop' to the conversation here, but beware hard and fast rules for every situation.


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## Anthony (Oct 5, 2006)

That's one of the first things Joe D'appolito mentions in his loudpspeaker measurements book: crossover points and dispersion. It's not just about setting a crossover point that sums flat or keeping the crossover out of the sensitive region. You have to also consider driver distortion and dispersion. Ask a midrange to play too high and it will "beam". Ask a tweeter to play too low and it will distort.

As to the original topic: Two ways almost always have to cross in the 1.5 to 3kHz region. Very few tweeters can play lower and very few woofers can play higher. However, I've heard some incredible two way speakers and they sound great, despite being crossed in that region. So if the drivers are up to it and the crossover is well designed, it will still sound good.


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## BoomieMCT (Dec 11, 2006)

Anthony said:


> That's one of the first things Joe D'appolito mentions in his loudpspeaker measurements book: crossover points and dispersion. It's not just about setting a crossover point that sums flat or keeping the crossover out of the sensitive region. You have to also consider driver distortion and dispersion. Ask a midrange to play too high and it will "beam". Ask a tweeter to play too low and it will distort.


DING! This is why when I use a wide bandwidth mid I tend to use 3"-4" drivers (preferably smaller). That way they beam less and, if you are using multiple mids, you can put them closer together to reduce comb filtering. 

Just like dating, all speaker design represent a set of compromises. The key is finding the qualities you need and the compromises you can live with.


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## BoomieMCT (Dec 11, 2006)

drf said:


> It's not so much about the range, but about other aspects of passive filters like impeadance matching and thus no requirment for zobel networks, it also eleviates the need for driver sensitivity compensation which if not implemented properly can cause more headaches.


These are all advantages of active crossovers, but I still don't see how that would make a single driver play a wider range. The original statement seemed to imply that using an active crossover on a 2-way speaker would allow the crossover to be placed in places a passive crossover could not.


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## Anthony (Oct 5, 2006)

I think the advantages of an active crossover are this:

If you have a driver that is very well behaved up to 1.5kHz and then starts to beam (or breakup), then you can't just passively cross it at 1.5kHz because a lot of that "bad" behavior still leaks through. So if beaming is the issue, off axis is no longer getting a flat summation at the crossover region, it drops off. That's why people design crossovers that stay at least an octave away from any of the undesirable traits of the driver (sometimes even farther).

With an active crossover, you don't have to worry about the "leakage" because you can essentially brick wall the filter at 48db/octave, resulting in a crossover point much closer to frequencies that cause the undesirable effects.

That's my take on it anyway. You're getting more effective range because you can cross an octave closer to the frequencies you want to avoid.


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## JCD (Apr 20, 2006)

BoomieMCT said:


> These are all advantages of active crossovers, but I still don't see how that would make a single driver play a wider range. The original statement seemed to imply that using an active crossover on a 2-way speaker would allow the crossover to be placed in places a passive crossover could not.


Sorry, I wasn't clear.. the idea wasn't that an active crossover doesn't allow a driver to play a wider range, just that the issues with having a crossover point in that particular range are minimized. 

Again, not going to claim to be an expert, but I've been led to believe that, for example, distortion is increased in this area due to the passive components. An active crossover won't have the same issues.

JCD


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## BoomieMCT (Dec 11, 2006)

JCD said:


> Again, not going to claim to be an expert, but I've been led to believe that, for example, distortion is increased in this area due to the passive components. An active crossover won't have the same issues.
> 
> JCD


Where did you hear this? Distortion can be added by passive _or_ active crossovers. There isn't anything magic about active crossovers - they just split the signal before the amp instead of after it.


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## drf (Oct 22, 2006)

BoomieMCT said:


> Where did you hear this? Distortion can be added by passive _or_ active crossovers. There isn't anything magic about active crossovers - they just split the signal before the amp instead of after it.


They do more than split the signal before the amp, they are not reliant on inductors, they do not react to the back emf from the driver so damping is not an issue, there is almost complete electrical isolation between the woofer and tweeter and thus one does not alter the other. From these characteristits alone an active crossover is far less likely to produce distortion than its passive counterpart.


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## BoomieMCT (Dec 11, 2006)

drf said:


> They do more than split the signal before the amp, they are not reliant on inductors, they do not react to the back emf from the driver so damping is not an issue, there is almost complete electrical isolation between the woofer and tweeter and thus one does not alter the other. From these characteristits alone an active crossover is far less likely to produce distortion than its passive counterpart.


Point taken - a _good_ active x-over will produce less distortion (for a lot more money). However I still do not see how this applies to the thread subject. Yes, a steep x-over slope (active or passive) will allow you to move your x-over point towards the ends of the bandwidth a bit. It will not affect when a driver will start beaming and it won't increase the frequencies a driver can play without distortion.

Ultimately there is no problem having an x-over in the 300 - 3kHz range assuming it is a well designed crossover. The only real disadvantage is that your ear, being more sensitive in that range, will be more apt to detect flaws in the crossover OR will be more apt to detect flaws from the fact the drivers are not colocated (unless they are coaxial). It is probably safe to say that if someone has ever heard a set of 2-way speakers they like, then this won't be a problem.


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## JCD (Apr 20, 2006)

BoomieMCT said:


> Where did you hear this? Distortion can be added by passive _or_ active crossovers. There isn't anything magic about active crossovers - they just split the signal before the amp instead of after it.


Active vs. Passive Crossover

TKoP


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## BoomieMCT (Dec 11, 2006)

JCD said:


> Active vs. Passive Crossover
> 
> TKoP


Good article, although statments like "All passive filters will cause the amplifier to have a rather tenuous grip on the driver behaviour at best" seem somewhat less than objective. 

This is still besides the point. My point is that active crossovers will offer little advantage over passive crossovers as far as expanding the crossover points of a speaker above 3kHz and below 300 Hz. Driver selection and driver placement (in relation to each other) will probably be much more important.


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## JCD (Apr 20, 2006)

BoomieMCT said:


> This is still besides the point. My point is that active crossovers will offer little advantage over passive crossovers as far as expanding the crossover points of a speaker above 3kHz and below 300 Hz.



I TOTALLY agree with the above statement.

JCD


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## drf (Oct 22, 2006)

BoomieMCT said:


> Ultimately there is no problem having an x-over in the 300 - 3kHz range assuming it is a well designed crossover. The only real disadvantage is that your ear, being more sensitive in that range, will be more apt to detect flaws in the crossover OR will be more apt to detect flaws from the fact the drivers are not colocated (unless they are coaxial). It is probably safe to say that if someone has ever heard a set of 2-way speakers they like, then this won't be a problem.


exactly, so in summation it would safe to say that if you have to cross between 300 and 3000 then either do it properly or get different drivers.


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## BoomieMCT (Dec 11, 2006)

As a possibly interesting note Bowers and Wilkins crosses their 800 series 3-ways at 350Hz and 4kHz. Additionally they say they use a low order electrical network. They accomplish this by using a very capable kevlar mid. I think that many of their 2-ways are crossed high, again because of using a capable kevlar mid/woofer.


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## groundie (Feb 7, 2008)

one simple advantage of an active xo (e.g., DCX2496 mentioned earlier) is the ease for experimentation. with my set of home-assembled diy speakers, i've had great success with active.
of course, success as subjectively measured by my ears.
these quickly put-together diy speakers (total cost approx. $500) easily beat out my old pair of B&W DM640s (i think i paid something like $600 some 10 years ago).
is this surprising? it was for me.

of course, one major disadvantage of going active and bi-amping is the extra amps, but for me truly worth it for the superior sound.


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## terry j (Jul 31, 2006)

groundie said:


> of course, one major disadvantage of going active and bi-amping is the extra amps, but for me truly worth it for the superior sound.


but nowadays watts are _cheap_. Years ago it might have been a much greater expense, but nowadays the advantages of active far far outweigh the (much less relevant) extra cost of amps.


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## groundie (Feb 7, 2008)

as suggested,
i tried widening the woofer frequency range with a steep slope (LR-48) per driver's spec. generally speaking, this resulted in more trebly or
crispy sound (some CDs more so than others) than gentler slope.
this does not seem intuitively correct to me; i was expecting the opposite. can someone offer an explanation or am i hearing things wrong?


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## drf (Oct 22, 2006)

> i tried widening the woofer frequency range with a steep slope (LR-48) per driver's spec. generally speaking, this resulted in more trebly or
> crispy sound (some CDs more so than others) than gentler slope.
> this does not seem intuitively correct to me; i was expecting the opposite. can someone offer an explanation or am i hearing things wrong?


As the frequency being reproduced rises, all woofers start to introduce some degree of harmonic distortion and intermodualtion distortion. When and how bad depends on the drivers design, cone material, size etc. This distortion is commonly called cone breakup, it often manifests itself as a brittle sound sometimes refered to as chirpy or edgy. This could easily be what you are hearing. I would leave the slope set at 48 and slowly bring down the xover point until the crispy sound disapeers or becomes normal for your drivers. And lastly never doubt what you are hearing, no one has golden ears, just be prepared to sift through a whole heap of different explanations until you find one you agree with.


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## Anthony (Oct 5, 2006)

Yeah, even the Loudspeaker Measurements book (which I recommend BTW) mentions that listening first then looking at the plots to explain is a good way to go. 

If you hear some harshness, check out some results to explain it. If it sounds great, don't mess with it 

You can drive yourself nuts trying to explain and overcome the anomalies present in speaker building.


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## BoomieMCT (Dec 11, 2006)

Anthony said:


> You can drive yourself nuts trying to explain and overcome the anomalies present in speaker building.


I'll remember you said that . . . :bigsmile:


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## Anthony (Oct 5, 2006)

yeah, but the problem is, I seem to hear lots of stuff that you, my wife, and everyone else can't. <pulls hair out> Time for my meds.


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## BoomieMCT (Dec 11, 2006)

Anthony said:


> yeah, but the problem is, I seem to hear lots of stuff that you, my wife, and everyone else can't. <pulls hair out> Time for my meds.


If you are hearing stuff no one else can hear . . . . have you considered that you are perhaps insane? :bigsmile:

To explain, Anthony and I have worked on a few projects together. I like to experiment on many things at once, while Anthony is a perfectionist and likes to obsess. How all this relates to this thread is that he's working on a very very cool set of 3-way dipoles now that, when finished, will sound and look like nothing I've seen or heard before. The main hangup to-date has been obsessing over the crossover settings, baffle design and (sometimes) driver selection trying to get the crossover points outside of the 300 Hz - 3kHz (ish) range while avoiding breakup modes and minimizing little bumps in the FR.

I guess the moral of the story is this isn't trivial in design, but the result is probably worth something.


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