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Line-level crossover for bi-amped speakers?


kdoot

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Hi Mike, it's too quiet around here! A post over on the PS Audio forum got me thinking about this, and I figured there might be more people than just me interested in your thoughts.

 

What do you think about the idea of a passive line-level analogue crossover that sits between a pre-amp (or active source like my DirectStream DAC) and a set of stereo power amplifiers for bi-amping a pair of your 2-way speakers? Have you ever experimented with systems like this? 

 

I know you did some work with active speakers and DEQX but I'm particularly interested in your analogue crossover designs for this application.

 

Cheers mate. 

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The crossovers inside a traditional multi-driver speaker are passive. Signal comes in from the amp, frequencies are divided among the outputs, all totally passive. Could that not be done with much lower level signals?

 

SGR makes "active loudspeakers", which is more about having amplifiers inside the speakers I thought. That they also perform crossover functions prior to amplification – which obviously requires more channels of amp – is the same as what I'm asking Mike about regarding his own designs.

 

I'm definitely not talking about digital crossovers though. That was the main concept I was trying to convey with the term "passive". 

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2 hours ago, Sir Sanders Zingmore said:

I'm pretty sure that you can't have a passive line-level crossover (I may well be wrong here).

 

SGRs active line-level crossovers are analog

 

Most certainly passive line level crossovers are a thing (I use them myself - built right into the amplifiers) and in certain circumstances they can be advantageous.  For instance, the filter cap values are much smaller (and therefore cheaper and less sonically intrusive) and the amplifier gets to drive only the transducer, not the passive network before it, so it can be an easier load which in some circumstances benefits singled ended amplifiers, particularly tubes.

 

In some circumstances you can also remove components from the network by using amplifier interstage coupling caps as part (or all) of a high pass filter, thus removing the need for that cap in the crossover. 

Edited by acg
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15 minutes ago, kdoot said:

The crossovers inside a traditional multi-driver speaker are passive. Signal comes in from the amp, frequencies are divided among the outputs, all totally passive. Could that not be done with much lower level signals?

I understand what you meant. My understanding (and as I said, I may be wrong) is that the low level signals are too low for a passive crossover 

 

edit: @acg answered as I was typing. Ignore me !

Edited by Sir Sanders Zingmore
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5 hours ago, kdoot said:

What do you think about the idea of..

I'm obviously not Mike, but have been suggesting such filters for years....  but, there are a lot of buts....  and it isn't as simple as "go active" (or line-level filter) and win good sound.

 

 

If you build a speaker with a well done passive crossover  ... and then you build a speaker with exactly the same crossover implemented "active" or "line level".    There is not any super-massive reason to assume the "not-speaker-level" filters are going to be obviously better.    In fact, I'd expect them to sound the same.

 

The real benefits of such crossovers is the ability to make more complex filter shapes (than speaker-level filters), filters with boost, and to equalise drivers with non-equal SPL.

 

One could argue, this isn't needed in ML speakers as the drivers are very well behaved, and from the get go designed with the knowledge there'd be a speaker level filter.

 

 

So, to get any real serious advantages - you would need to redesign the filters (and then perhaps the entire speaker) ..... and one could argue this (ie. redesigning anything) isn't needed.

 

 

OTOH, if it's something you really wanted to do..... it's relatively trivial to design a line-level filter which implements exactly the transfer function in your speakers current filters.

 

4 hours ago, Sir Sanders Zingmore said:

I'm pretty sure that you can't have a passive line-level crossover (I may well be wrong here)

Sure you can.    You just put RCL in between your source/pre and amp.

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2 hours ago, kdoot said:

SGR makes "active loudspeakers", which is more about having amplifiers inside the speakers I thought. That they also perform crossover functions prior to amplification – which obviously requires more channels of amp – is the same as what I'm asking Mike about regarding his own designs.

Yep.

 

 

You can also have active analogue line level crossovers.    ie. line level filters which have active devices (eg. opamps).

 

 

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Good replies all, thanks. I guess my question for Mike would be something along the lines of whether it might have any sonic advantages or disadvantages, and whether we could meet or exceed the performance of his best speaker-level crossovers (Duelund Cast etc) at much lower prices. Though of course we double up on cables and amps... maybe it'd be worth it.

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Maybe a basic but good quality active analogue crossover using op-amps.

It would certainly cost a whole lot less than the usual passive version.

The good part is no resistance between the amp & drivers.

OK I will have a chat with Mike about it next time I see him.

Klein Cossover ???

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On 16/02/2019 at 6:26 PM, davewantsmoore said:

One could argue, this isn't needed in ML speakers as the drivers are very well behaved, and from the get go designed with the knowledge there'd be a speaker level filter.

This ^

 

I have some vague recollection that Mike once tried an active crossover as an experiment and the consensus seems to be that the passive version was better.

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10 hours ago, Sir Sanders Zingmore said:

consensus seems to be that the passive version was better.

There were likely differences between the filters causing this.

 

 

I would put money in mouth that I could make an active and/or line level filter which sounded exactly the same as a typical passive speaker-level filter .... all else being equal (eg. same amps/sources, etc.)

 

If you made a different shaped filter (as opposed to exactly copying the existing passive speaker-level one)  ... then you could maybe make a better active one..... and of course, you would easily make a much worse one.

 

 

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11 hours ago, Gieseler Audio said:

Maybe a basic but good quality active analogue crossover using op-amps.

If you want to make the same filter shape(s) as the passive speaker-level one .... then there is no need to use op-amps.

 

Of course, using op-amps, you can make many more complex filter shapes that are impractical/impossible with a speaker level filter

 

 

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Thanks Dave.

 I will have a good chat to Mike about it and see what sort of slopes & baffle correction he is using.

Mikes factory  it’s only five minutes from mine so I call-in regularly.

 I’m sure he will give me his Clio measurements  - that way I can have a good look at transfer functions phase etc and see how hard it would be to match up.

 I will add an update once I’ve had a chat with Mike about it.

 You ever ever know - maybe another Gieseler Lenehan alliance coming up. 

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On 16/02/2019 at 11:41 AM, kdoot said:

Hi Mike, it's too quiet around here! A post over on the PS Audio forum got me thinking about this, and I figured there might be more people than just me interested in your thoughts.

 

What do you think about the idea of a passive line-level analogue crossover that sits between a pre-amp (or active source like my DirectStream DAC) and a set of stereo power amplifiers for bi-amping a pair of your 2-way speakers? Have you ever experimented with systems like this? 

 

I know you did some work with active speakers and DEQX but I'm particularly interested in your analogue crossover designs for this application.

 

Cheers mate. 

Hi Terry

                  yes indeed it is possible ! in fact on my way to work this morning Clay Geiseler rang me  and said he had seen your post and thought it could work very well .

 

I have been thinking about this on and off for about 10years but simply haven't had the time ! anyway to cut a long story short Clay and I are going to work on this together . He has more experience than I at line level and Myself at Speaker level . 

 

I'm not sure if there would be an advantage at Xover frequencies above 1.5khz but I can imagine significant gains at frequencies around 100 to 300hz.  I've tried many configurations and brands of active Xovers and they simply cannot match dedicated custom designed Passives.

 

This is the very reason I have not effectively designed a big three way ! can you imagine a SOTA passive Xover at 150hz . We would need a 15mh aircored inductor with a DCR of 0.2ohms ! Ahh Huh ,it would weigh about 13 kgs . Of course you can always build it with a piece of junk iron cored inductor to get the DCR low but I aint ever gonna do dat Bros  :)

 

Ok I'm going to talk to Clay later today and get something started. I'll update with progress soon .                     Cheers Mike Lenehan

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On 19/02/2019 at 7:52 AM, Sir Sanders Zingmore said:

I have some vague recollection that Mike once tried an active crossover as an experiment and the consensus seems to be that the passive version was better.

 

Yes.   Mike, like a lot of speaker designers, was very impressed with the DEQX and got one.   It beat his current crossover but he then came up with his PRC crossover.   That beat the DEQX,   But online discussions with someone from DEQX indicates it has made big strides in transparency so the comparison really needs to be done again.   To be fair however you would need the rather pricey DEQX 4 with its DAC outputs so you can use the same DAC in comparison.   I would love to do it but it is just a bit to pricey for me to purchase the DEQX.   Clay can supply the dual DAC's so that is no problem, its just the cost of the DEQX.

 

Regarding the original query the HDP2 would be a more cost effective choice - no pre or DAC needed:

https://www.deqx.com/products/hdp-express-ii/

 

I could just swing getting one of those for a comparison, but it will be unfair because the passive version will use better quality DAC's.

 

Mike has told me and plenty of others he will build any of his speakers to work with the DEQX.   Some have taken him up on the offer so they may like to chime in.

 

I only wish the DEQX guys would make a version with only sub-woofer analogue outputs and the others digital.   To me that would be more 'high end' without the expense of all the other stuff that comes with the HDP4 - just me and my priorities.   The DEQX guys have their own reasons for the products they make ie it may be the price difference between my suggestion and the HDP4 is not worth a separate product.

 

Thanks

Bill

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