speaker level crossover

[mike c]

where can I find a speaker level crossover - similar to those found on plate amps - that have a 100hz highpass?

I only need the highpass side, but having a lowpass would be a bonus.

if there's a variable highpass crossover, that would be even better!

thanks in advance

I want to run my front speakers full range on the receiver and use subwoofers up front, but I don't want to run the extra long wires for an active crossover with line level connections.

 

[TLS Guy]

where can I find a speaker level crossover - similar to those found on plate amps - that have a 100hz highpass?

I only need the highpass side, but having a lowpass would be a bonus.

if there's a variable highpass crossover, that would be even better!

thanks in advance

I want to run my front speakers full range on the receiver and use subwoofers up front, but I don't want to run the extra long wires for an active crossover with line level connections.

This is what you need.

http://www.marchandelec.com/xm9.html

Phil Marchand makes really good gear, and is a very nice guy.

 

[mike c]

This is what you need.

http://www.marchandelec.com/xm9.html

hmm, should i just be buying the boards?

 

[TLS Guy]

This is what you need.

http://www.marchandelec.com/xm9.html

hmm, should i just be buying the boards?

You might want to try these new digital crossovers. This is the way everything will go. I'm pretty certain the industry will move to powered speakers, with digital crossovers, and the receiver will be a museum curio.

I hope to do experiments with digital crossovers soon. They have big advantages over analog filters, and I think will provide the next big improvement in speaker performance. A good analog filter active or passive is a costly thing, and they are actually one of the big limiting factors in all but the most expensive of systems and even then I think they still are.

Here is a link were you can purchase one.

http://www.zzounds.com/item--BEHDCX2496

If you build from one from a board you will need to make a good power supply.

If you get a good op_amp design cookbook such as the one by Carl Linkowitz, you can design and build your own.

 

[annunaki]

Assuming one has the amplification available, going the DIY route with digital crossovers does seem very advantageous.

I have questions in doing so.

1) Would one still put in analog Baffle Compensation Circuits to aid in response? Does it make sense to do so?

2) How does this affect tweeter responses and blending on the lower end of its range?

3) Would it still be necessary to use analog shaping filters with the tweeters?

4) Or, is all of it unecessary as many of the compensation circuits are solutions to issues associated with analog crossover circuits?

 

[mike c]

but I really need something that uses speaker level connections ... since my front speakers are about 30-40 feet from the back ... I will need 2 cables to run to each channel just to use line level connections.

I mean short of buying a plate amp just to use it's highpass output, am I SOL?

 

[TLS Guy]

Assuming one has the amplification available, going the DIY route with digital crossovers does seem very advantageous.

I have questions in doing so.

1) Would one still put in analog Baffle Compensation Circuits to aid in response? Does it make sense to do so?

2) How does this affect tweeter responses and blending on the lower end of its range?

3) Would it still be necessary to use analog shaping filters with the tweeters?

4) Or, is all of it unecessary as many of the compensation circuits are solutions to issues associated with analog crossover circuits?

Dear Annunaki,
First of all truth in advertising, I have no hands on experience using digital filters, but I'm getting increasingly tempted to get my feet wet.

Let me tell you what little I know.

This Australian firm have blazed the trail. I have watched their progress with interest.

http://www.deqx.com/DEQX-Linear-Phase-Digital-Crossovers.html

Their gear is very expensive, as is so often the case with those in first.

Behringer have entered the field with units at a tempting price point to play.

Meridian have had a high end system using digital crossovers and powered speakers for some time. It is expensive, but highly regarded. I have a feeling history will regard it as seminal product.

Now the advantage of digital crossovers is steep slopes with no phase, time or group delay issues due to the crossover. Phase shifts due to the inductive nature of moving coil drivers will still be with us, as will problems of time because of driver placement and the positions of their true acoustic centers.

Now as to your first question would diffraction compensation be necessary? I would say yes if small bass/mid drivers are used on a narrow baffle. How you do this in the digital domain I don't know, but I'm sure there is a way.

Now as far as blending is concerned that is the big attraction. Usually in analog filters either active or passive one is working with low order filters. The result is driver overlap.

The problem is then to blend the natural roll off of the driver slopes with the crossover slopes to sum to a flat frequency response. No easy task as driver slopes frequently change order, and then the crossover slopes have to be the inverse.

The next problem to solve is keeping the drivers out of their trouble zones. Because of the preoccupation with rigid driver cones, woofers hit the wall hard and generally have very unpleasant break up modes often in the 4KHz range. These frequently have to dealt often with notch filters and all the attendant phase problems. Ted Jordan debunked the issue of rigid cones back in the 60s, with elegant experiment and advanced math. The Jordan Watts modular loudspeaker was the result. The problem is very few have realized the significance of his work.

Now with the tweeter, the pass band issue is keeping the tweeter well away from its fundamental resonance. The same applies to a midrange, plus the same issues as a woofer. I personally like to have a tweeter 24db down at resonance.

The other issue with the large driver overlap using low order filters, is comb filtering. This is where the response is made irregular by adjacent drivers canceling at some frequencies and reinforcing at others.

Now to answer your question. If I were to use a digital filter I would use steep slopes and operate the drivers well in their pass bands. That would solve the issues I relate above.

As far as shaping the tweeter response, I would choose one that is very smooth above were it starts its lower end roll off and obviate the problem.

Now all of this it seems to me would make three and four way designs much less problematic. Good 10 inch woofers could be driven further up their operating range, and this would make this diffraction loss issue less acute, as well as keeping the mid range units well in their pass bands.

If the whole scheme is as as good as it seems, the issue is going to boil down to selecting the optimal crossover frequency for the selected drivers, driver placement and level matching. I just hope it is not to good to be true. However if drivers a selected with very flat pass bands I don't see why it should not solve a lot of thorny issues.

Now the selection of amps is important for the tweeter I feel. The tweeter will not like turn on thumps or any DC off set what ever. So I feel a an amp with a cap in the output would be mandatory. A good use for a nice old quad 303. Also I think there should be circuits to disconnect the tweeter and probably a lot of mid ranges at turn on and for a few seconds after.

I know most of what I have written will be old news to you, as I can tell you have wrestled plenty with these issues. However I think this is an important issue, and likely to bring about big changes in audio, that will ultimately involve all members of these forums. And I feel the educational aspect of these forums is paramount.

I hope I have answered your questions, even if in a roundabout way.

 

[WmAx]

Assuming one has the amplification available, going the DIY route with digital crossovers does seem very advantageous.

I have questions in doing so.

1) Would one still put in analog Baffle Compensation Circuits to aid in response? Does it make sense to do so?

You do not use any baffle step compensation on the speaker in the analogue realm. No reason. You program a 6dB/octave rate shelving filter to the digital unit and compensate at that point. The real advantage is increases sensitivity(a speaker level BSC circuit reduces power available to the speaker above the corner frequency of the filter) and is variable(optimal BSC is different for different rooms and posititions).

2) How does this affect tweeter responses and blending on the lower end of its range?

Makes it easier. You can, without added cost or effort, use cascade filters to increase power handling and reduce distortion of the tweeter, thus allowing lower crossover points. Virtually any filter contour is possible manipulating the variables of the filter, allowing for off axis integration/characteristic that is ideal for your objective(s).

3) Would it still be necessary to use analog shaping filters with the tweeters?

No.

However, as TLS Guy suggested, it may be prudent to use a large capacitor on the tweeter to protect it from the LF content of turn on/off thumps. I use this method to protect my tweeters.

4) Or, is all of it unecessary as many of the compensation circuits are solutions to issues associated with analog crossover circuits?

You can do almost anything with a digital crossover. Personally, I will never again use passive crossovers on any main speaker system. Of course, low cost speakers for other people are a different matter - as they are not usually willing to upfront the costs associated with multiple amplifiers, etc.

-Chris

 

[annunaki]

You do not use any baffle step compensation on the speaker in the analogue realm. No reason. You program a 6dB/octave rate shelving filter to the digital unit and compensate at that point. The real advantage is increases sensitivity(a speaker level BSC circuit reduces power available to the speaker above the corner frequency of the filter) and is variable(optimal BSC is different for different rooms and posititions).



Makes it easier. You can, without added cost or effort, use cascade filters to increase power handling and reduce distortion of the tweeter, thus allowing lower crossover points. Virtually any filter contour is possible manipulating the variables of the filter, allowing for off axis integration/characteristic that is ideal for your objective(s).



No.

However, as TLS Guy suggested, it may be prudent to use a large capacitor on the tweeter to protect it from the LF content of turn on/off thumps. I use this method to protect my tweeters.



You can do almost anything with a digital crossover. Personally, I will never again use passive crossovers on any main speaker system. Of course, low cost speakers for other people are a different matter - as they are not usually willing to upfront the costs associated with multiple amplifiers, etc.

-Chris

Chris,

Suppose one wanted to do a 2-way system with high order slopes, high pass and low pass at 36db/oct. or so. With a digital two-way crossover how would one program the 6db/oct shelving filter in?

You can program multiple slopes into one lowpass filter I assume?
For instance, start out with a 6db/octave rolloff at 3khz and then roll off at 36db/oct. starting at 2khz where the Fs of the tweeter is at say 900hz.

 

[WmAx]

Chris,

Suppose one wanted to do a 2-way system with high order slopes, high pass and low pass at 36db/oct. or so. With a digital two-way crossover how would one program the 6db/oct shelving filter in?

You can program multiple slopes into one lowpass filter I assume?
For instance, start out with a 6db/octave rolloff at 3khz and then roll off at 36db/oct. starting at 2khz where the Fs of the tweeter is at say 900hz.

With a Behringer DCX2496, it is quite simple. For every channel(you have six per DCX unit), you can specify high pass and low pass crossover types/slopes. You then have an EQ window for each channel. In this EQ window you can specify parametric bands and/or shelving filters. To cascade, you would set up a xover in the xover window as your primary intended one. Then you use the EQ window and program in shelving or parametric bands to cascade or otherwise change the contour. The Behringer allows unlimited cascading of filters until you run out of CPU power, of course.

-Chris

 

[TLS Guy]

With a Behringer DCX2496, it is quite simple. For every channel(you have six per DCX unit), you can specify high pass and low pass crossover types/slopes. You then have an EQ window for each channel. In this EQ window you can specify parametric bands and/or shelving filters. To cascade, you would set up a xover in the xover window as your primary intended one. Then you use the EQ window and program in shelving or parametric bands to cascade or otherwise change the contour. The Behringer allows unlimited cascading of filters until you run out of CPU power, of course.

-Chris

Thanks Chris!
You have now brought me the point of raging thirst.

 

[WmAx]

Thanks Chris!
You have now brought me the point of raging thirst.

To be fair, I should point out that using a DCX, the slope indicated is not the final acoustic slope; it's just the electrical slope. You use a combination of the xover setting and EQ window for each channel to achieve the final desired slope characteristic(s). Also, the DCX does not have the brickwall linear phase filters functions that you mentioned eariler. The DCX emulates non-linear phase analog filter systems. But I am not convinced to use linear phase filters yet - as when you move off the on axis reference - strange time domain distortions occur using linear phase filters. You get prominent pre-ringing effects. This has not been studied for audiblity as of yet. The DCX is also a strange wonder of value, IMO. Internally, it uses the same parts you expect to find in high dollar studio gear. Yet, it's budget priced at $270. DBX's closest price competing product, at almost 2x the price, is inferior in features/function, overall. You have to move to the near $1k DBX to exceed some of the function of the DCX. The DCX operates transparently with no noise whatsoever when you have it set up and connected properly.

-Chris

 

[TLS Guy]

To be fair, I should point out that using a DCX, the slope indicated is not the final acoustic slope; it's just the electrical slope. You use a combination of the xover setting and EQ window for each channel to achieve the final desired slope characteristic(s). Also, the DCX does not have the brickwall linear phase filters functions that you mentioned eariler. The DCX emulates non-linear phase analog filter systems. But I am not convinced to use linear phase filters yet - as when you move off the on axis reference - strange time domain distortions occur using linear phase filters. You get prominent pre-ringing effects. This has not been studied for audiblity as of yet. The DCX is also a strange wonder of value, IMO. Internally, it uses the same parts you expect to find in high dollar studio gear. Yet, it's budget priced at $270. DBX's closest price competing product, at almost 2x the price, is inferior in features/function, overall. You have to move to the near $1k DBX to exceed some of the function of the DCX. The DCX operates transparently with no noise whatsoever when you have it set up and connected properly.

-Chris

Dear Chris,
Nothing like the voice of experience. Thanks for the tutorial. I was not contemplating using it my studio system. That sounds very good indeed. However I feel instinctively that this is the way things will go, especially with the improvements being made in class D amps. I just have a feeling that even at this time in my life it would be good to get some experience. Obviously you have. May be this spring I will experiment with a two way. I have been wanting to make an updated line round the JW module. I still have a lot of those. I was the Canadian agent for Jordan Watts back in the seventies. Here is a bit of audio history for you. This is an interview I recorded with Leslie Watts back in 1976.

http://www.walberswickstudios.com/player/id/0