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ALK Crossovers


mkane

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10 hours ago, Doug said:

Sorry if the answer has been stated already in terms I just don't understand, but with a SET amp and a stock AA network (no swamping resistor) in a Klipschorn, would there be more or less output at the frequency where the impedance is the highest?  

 

(Edited for clarity) Yes more output relative to the rest of the frequency spectrum .........when using a typical SET Amplifier

 

The internal impedance of the amplifier together with the [AA network/Klipschorn] impedance are performing like a frequency variable voltage divider. Thus the Voltage Drop across the [AA network/Klipschorn] will increase as the impedance of the [AA Network/Klipschorn] increases.

 

miketn

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5 hours ago, mikebse2a3 said:

The internal impedance of the amplifier together with the [AA network/Klipschorn] impedance are performing like a frequency variable voltage divider. Thus the Voltage Drop across the [AA network/Klipschorn] will increase as the impedance of the [AA Network/Klipschorn] increases.

So, this results in fewer decibels of sound at the frequency where the impedance is high?

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Does it seem bizarre to anyone the solution to this problem is to shunt power through a resistor in the midrange circuit?  Of course it depends on the size of the shunt resistor, but in the case of the Klipschorn, you would basically have to generate about 5 watts just to generate one watt in the compression driver (4 watts will be dissipated by the resistor as heat).  You have already cut the midrange efficiency to 20% just by going through the network.

 

Does it really sound like a good idea to dissipate that kind of power through the network?   

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57 minutes ago, dBspl said:

Does it seem bizarre to anyone the solution to this problem is to shunt power through a resistor in the midrange circuit?  Of course it depends on the size of the shunt resistor, but in the case of the Klipschorn, you would basically have to generate about 5 watts just to generate one watt in the compression driver (4 watts will be dissipated by the resistor as heat).  You have already cut the midrange efficiency to 20% just by going through the network.

 

Does it really sound like a good idea to dissipate that kind of power through the network?   

It doesn't sound like a good idea to me because of all you have pointed out and there are better options in my experience like high quality Analog EQ Units or even better DSP Signal Processors that would allow someone to tailor the sound to what they want and still maintain the easy option of retaining the orginal Klipschorn sound.

 

miketn 

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1 hour ago, mikebse2a3 said:

It doesn't sound like a good idea to me because of all you have pointed out and there are better options in my experience like high quality Analog EQ Units or even better DSP Signal Processors that would allow someone to tailor the sound to what they want and still maintain the easy option of retaining the orginal Klipschorn sound.

 

miketn 

 

Aren't you talking about two separate things. One, is the use of the swamping resistor to give a consistent load to the amp (better for tube amps that have a higher output impedance than SS amps) and two, making adjustments to the mid driver to tailor the sound to your room (which is what many seem to do on the stock heritage systems. A lot of folks seem to knock off around 3db on the mids,This really helped my La Scalas, with the added benefit or making the overall tonal balance better (to get the mids back up, the bass improved as well. This eliminated what Tom Brennan used to call the  "chainsaw in your forehead" sound, with the mids way too hot. I could have used an EQ, of course, but I don't have one in my system.

 

I believe William has also used the DHA2 that I use, which is a pretty simple network, but it does have the swamping resistor in it. My 3.5 watt amps have no problem getting to any level at which I am going to listen.

 

btw, this is all a great discussion.

 

Bruce

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3 hours ago, dBspl said:

Does it seem bizarre to anyone the solution to this problem is to shunt power through a resistor in the midrange circuit?  Of course it depends on the size of the shunt resistor, but in the case of the Klipschorn, you would basically have to generate about 5 watts just to generate one watt in the compression driver (4 watts will be dissipated by the resistor as heat).  You have already cut the midrange efficiency to 20% just by going through the network.

 

Does it really sound like a good idea to dissipate that kind of power through the network?   

 

 

Where are you getting these calculations from?

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It's just a crude estimate based on a midrange impedance of around 30 ohms and a shunt resistor of around 8 ohms. 

 

The loss would be significantly higher on a product such as a Heresy where the midrange impedance approaches 100 ohms.

 

Kerry

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5 hours ago, dBspl said:

Does it really sound like a good idea to dissipate that kind of power through the network? 

 

If you suspend belief in passive networks just for a moment and rethink the entire situation instead...this time using a baseline of direct coupling each driver with an amplifier channel, and moving the electronic crossover networks to just upstream of the amplifiers.

 

Now look back at trying to use passive crossovers downstream of the amplifier outputs.  The notion of using passive networks now seems very strange, indeed.  Dumping all that heat into resistors in some parts of the audible spectrum, and playing extreme games with amplifier stability trying to drive large amounts of frequency-dependent reactance, sometimes with almost no load at all (less than 4 ohms load impedance)...it's like flooring an automobile accelerator and using the brake pedal to change speed (which doesn't sound like a very good way to do things...in fact it sounds insane). 

 

But the phrase that I keep hearing, echoing:

 

"we've never done it that way before...we've never done it that way before...we've never done it that way before...". 

 

"It's too hard...it's too hard...it's too hard..."

 

So when you finally make the shift to direct coupling amplifiers to drivers (i.e., biamping or tri-amping instead ) and you find out that you get much more than just 3 dB increased output headroom per amplifier (assuming identical amplifiers): it's more like 6-12 dB in practice on average, suddenly the sun's light appears, all around you. 

 

You immediately realize that it takes very little amplifier output power if you're willing to bypass loudspeaker passive network-induced reactances and resistances.  So much so that chip amps now start to become attractive alternatives.  Any kind of tube amplification--however small--becomes viable.  Very small transconductance amplifiers start to come viable...and new possibilities arise for increased fidelity everywhere you look.  All that constrained thinking about how to do it with passive crossovers...simply dissolves.  Air suddenly returns to the room, and you can move on to things that actually should make a difference in audio fidelity(...away from self-imposed flagellation).

 

:emotion-55:

 

JMTC.

 

Chris

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36 minutes ago, Chris A said:

All that constrained thinking about how to do it with passive crossovers...simply dissolves. 

This is a very compelling argument, especially when one starts really geeking out and gets tempted to go down the path of extreme slope passive networks.  Being pretty new to this hobby, I'm not feeling drawn to that rabbit hole as of yet.  I'm actually quite happy with the sound of my ST-70 and Klipschorns with ALK universals.  I debated doing a Crites-facilitated re-cap of my AA's shortly after I got my speakers, but ended up going with the ALK's because of the ability to adjust the midrange and tweeter levels.

 

I'm mostly interested in this stuff in an academic sense and am learning a lot right now!  I think it is pretty clear that there are many ways to arrive and the subjective goal of good sound.  Thanks for your patience and for sharing knowledge with a newb!

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1 hour ago, Chris A said:

 

If you suspend belief in passive networks just for a moment and rethink the entire situation instead...this time using a baseline of direct coupling each driver with an amplifier channel, and moving the electronic crossover networks to just upstream of the amplifiers.

 

Now look back at trying to use passive crossovers downstream of the amplifier outputs.  The notion of using passive networks now seems very strange, indeed.  Dumping all that heat into resistors in some parts of the audible spectrum, and playing extreme games with amplifier stability trying to drive large amounts of frequency-dependent reactance, sometimes with almost no load at all (less than 4 ohms load impedance)...it's like flooring an automobile accelerator and using the brake pedal to change speed (which doesn't sound like a very good way to do things...in fact it sounds insane). 

 

But the phrase that I keep hearing, echoing:

 

"we've never done it that way before...we've never done it that way before...we've never done it that way before...". 

 

"It's too hard...it's too hard...it's too hard..."

 

So when you finally make the shift to direct coupling amplifiers to drivers (i.e., biamping or tri-amping instead ) and you find out that you get much more than just 3 dB increased output headroom per amplifier (assuming identical amplifiers): it's more like 6-12 dB in practice on average, suddenly the sun's light appears, all around you. 

 

You immediately realize that it takes very little amplifier output power if you're willing to bypass loudspeaker passive network-induced reactances and resistances.  So much so that chip amps now start to become attractive alternatives.  Any kind of tube amplification--however small--becomes viable.  Very small transconductance amplifiers start to come viable...and new possibilities arise for increased fidelity everywhere you look.  All that constrained thinking about how to do it with passive crossovers...simply dissolves.  Air suddenly returns to the room, and you can move on to things that actually should make a difference in audio fidelity(...away from self-imposed flagellation).

 

:emotion-55:

 

JMTC.

 

Chris

 My constrained thinking towards passive crossovers has a lot to do with the fact that I have multiple systems and I change amplifiers quite often everywhere except my main system.  I need to be able to hook up any amp or receiver.   I don't mess with my amplification on the main setup because it was expensive and I like the music it reproduces.  When I'm done playing with passives I might just have to take on some new experiments that you have put into my head.  

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17 minutes ago, muel said:

 My constrained thinking towards passive crossovers has a lot to do with the fact that I have multiple systems and I change amplifiers quite often everywhere except my main system.  I need to be able to hook up any amp or receiver.   I don't mess with my amplification on the main setup because it was expensive and I like the music it reproduces.  When I'm done playing with passives I might just have to take on some new experiments that you have put into my head.  

 

I know that it seems like it makes a difference in your scenario, but it doesn't.  In fact, it's actually easier using active crossovers upstream of the amplifiers: just swap your amplifiers out A-B. no problem. 

 

Once you start to realize that virtually all of your issues with amplifiers are actually source music and passive crossover issues (along with non-flat acoustic driver frequency response on-axis and off-axis), you might find that you save a lot of money swapping amplifiers around.  I know that's been my experience.

 

EDIT: By the way, I also have found that the cost of my amplifiers is a lot less now.  The answer to the question "why is that?" is a key insight.

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On 10/16/2016 at 1:57 PM, tigerwoodKhorns said:

I am not worried about a constant impedance for my amplifier.  I do not think that it is necessary.

 

However, swamping the resistance of the midrange with a parallel resistor allows you to adjust the taps on the autoformer without changing caps. 

 

I am not a crossover expert, so my question is are there any disadvantages to swamping the autoformer?  The adjustable midrange is a nice feature. 

I'd love for someone to run some valid tests showing any difference!  I am doing this currently on one pair of B2 networks in Cornwalls of which I dropped the mids 3db on the taps.  I plan on removing the resistor and replacing the mid cap to listen for any difference.  It seems we have heard from a couple people here who have suggested they did hear a slight difference of some sort.  It does seem to me that there might be a slight change beyond just a 3db drop in the mids... I just can't put my finger on what it is.  When it comes to small changes I have to listen to them for days or weeks to figure out if I seem to like it better one way or another.  Sometimes it is just a matter of finding myself having longer or shorter listening sessions for me to call something "better" or not.

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2 minutes ago, Chris A said:

 

I know that it seems like it makes a difference in your scenario, but it doesn't.  In fact, it's actually easier using active crossovers upstream of the amplifiers: just swap them out A-B. no problem. 

 

Once you start to realize that virtually all of your issues with amplifiers are actually source music and passive crossover issues, you might find that you save a lot of money swapping amplifiers around.  I know that's been my experience.

Oh I don't feel as though I have an amplifier issue... I just swap amplifiers/receivers around because I have a bit of a collection and I don't like to let any of them sit unused for too long!  The source and the room are my biggest problems I think.

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26 minutes ago, muel said:

Oh I don't feel as though I have an amplifier issue... I just swap amplifiers/receivers around because I have a bit of a collection and I don't like to let any of them sit unused for too long!

Believe it or not, I actually like to listen to good music--not tinkering with hardware, so I try to keep my inventory of unused stuff to a minimum.  (I've probably got more than a few items to sell off once the K-402-MEH project has completed production for my setup upgrade needs.)

 

Fixing badly mastered recordings--oftentimes after decades of listening to them done badly--is also unbelievably cathartic for me. I always end up wondering, once again, how recording companies think that their as-released (clipped and creatively EQed) CDs are something that anyone likes to listen to.  After unmastering the recordings, it's always a pleasure to listen to the underlying recordings revealed for the first time.  There are some real gems out there.  For me, it's like restoring masterpieces. 

 

Have you seen the Sistine Chapel ceiling lately?

 

Chris

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13 hours ago, wdecho said:

You need to find the paper in Dope from Hope by the master to read how in his X-over he did not see the rise in impedance as evil. He describes in technical terms his findings in detail for those that are interested in those things. I doubt any of us has the equipment or rooms he used to test his findings. Most of his research was done when tubes ruled. I read now how many of the present designers and engineers still reference papers PWK  wrote years ago. As much as I enjoy reading AL's opinions on constant impedance X-overs I do not see him in the same light as PWK. 

 

I would have to disagree with the comment "Most of his work was when tubes ruled"  and from Roy's own accounting he was very interested and working with steep slope filters in his later years.

 

For those interested here are the Dope From Hope papers in a searchable pdf:

which includes the DFH Vol 16 No 8 I believe wdecho is referring to.

 

miketn

 

DOPE_from_HOPE!!!_searchable.pdf

DFH Vol 16 No 8  pg1.jpg

DFH Vol 16 No 8  pg2.jpg

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