Digital crossover - made me rethink a lot

[davidismynaim]

I have recently gone through a fairly radical change in my system, which I thought I would share as I am sure it will provoke a lot of views.

I picked up a very tidy pair of Innersound Isis speakers, they are hybrid electrostatics and transmission line bass. Having heard some very nice sounding ML hybrids before I really liked the sound stage and pure mids. I have also owned, many years ago, a pair of Cambridge R50 transmissions line. I loved the thought of this combination, so I gave them a go.

This in turn started a bigger change than I had intended. I made contact with Roger Sanders, the designer and then builder of the Innersounds, and questioned him about the possibility of going active, as I liked my experience with Naim and SBLs driven actively. I also knew his new company Sanders Sound Systems employ an active arrangement. He agreed and told me I could achieve special results with some work.

So after spending more than I had intended, I now have the speakers driven actively using a pro DBX Venu 360 loudspeaker management system into two sets of power amps. My existing Nord oneup ncore500's being used to drive the transmission line bass and one of Sanders ESL power amps driving the panels. With the cross over point set to 233Hz.

My big reservation with this setup is that the dbx is converting analogue from my Chord Hugo TT DAC and my vinyl source into digital, to perform the DSP, then back out through the 4 of the 6 DACs built into analogue again to be sent to my power amps. The thought of taking digital to analogue back to digital, through dsp and then back out in analogue sends a bit of shiver through me. The quality of the DACs in the DBX will be let's say utilitarian by comparison to say a chord.

The theory Roger espouses and I have to say I am coming round to, is that the quality of modern DAC is so good they really are not worth worrying about, the speaker is where it is at, and to do that right you must use electrostatics driven by the right type and power. Removing passive crossovers is another key aspect to get a seamless experience between ELS and convenintial cones, the best way to achieve this is to do it in the digital domain, the equivalent passive crossover would be near impossible to achieve.

The dbx is doing the crossover, some low <500Hz room correction, a little bit of bit of parametric EQ to help the panel out at the lower freq range and a bit of delay to time align the bass with the panel.

My conclusions is the speakers sound amazing, the best sound stage I've ever had, crystal clear mids and strong, quick and very integrated bass. I will be interested in others views. Might have to get the popcorn

 

[Woodface]

This is one of those occasions when you have to trust your ears & not worry about the technical aspects.

 

[irb]

Interesting post!
I owned a pair of Isis for a while. I was hugely impressed by the electrostatic panel, but wasn't totally happy with the low mid/bass from the dynamic driver. I suspect that the passive crossover in the Isis wasn't up to much. The nominal crossover point was 900 Hz, and when I measured the output from the woofers, there actually seemed to be a wide overlap above that frequency.
There was also an L-pad level control on the woofer. I'm not convinced that was a good idea, even though level matching between a dipole line-source panel and a monopole point-source woofer is a real problem, and if there's no adjustment it's pot luck whether the levels will be right.
I ended up with a rather unorthodox solution - a Bryston active crossover used in addition to the passive crossover. The Bryston rolled off the woofer more quickly, and handled the level matching. The results were much better than using the passive crossover alone, but I still felt the woofer wasn't right. (Not surprising really, since my set-up wasn't properly sorted.)
I ended up selling them rather than working out a better solution. Part of me still regrets that - the panel was really special, despite the amazingly narrow sweet spot. Digital crossover is probably the right solution, but as your post indicates, it's not obvious how best to do that. Paradoxically, I'm now exploring digital crossovers myself.
I'll be interested to hear how you get on going forward.

 

[irb]

Incidentally, 233 Hz is a long way below 900 Hz. Did Roger Sanders suggest crossing over that low?

 

[davidismynaim]

Roger supplied to the dbx pre-set up, so yes he did set the 233. I think its made possible by having a much more sophisticated way of crossing over and by lifting the lower range of the panel digitally. His amplifier is a beast too. He is convinced you need a lot of power (specifically volts) to drive the panels properly.

 

[davidismynaim]

good to get the woofer out of the critical freq range, and letting the panel do the work in the 900Hz range.

 

[irb]

Roger supplied to the dbx pre-set up, so yes he did set the 233. I think its made possible by having a much more sophisticated way of crossing over and by lifting the lower range of the panel digitally. His amplifier is a beast too. He is convinced you need a lot of power (specifically volts) to drive the panels properly.

Yes, that makes sense. And I guess Roger will have set a nice steep slope the high-pass too. His amps have a great reputation for driving electrostats. Not cheap though.

good to get the woofer out of the critical freq range, and letting the panel do the work in the 900Hz range.

Yes, I think the issues I had with the woofer were partly to do with the wide range it was covering.

 

[irb]

Good to hear how pleased you are with the results. Roger has been an advocate of crossing over digitally for quite a while now.

 

[davidismynaim]

48db/oct slopes, I managed to get a reconditioned unit from Roger, so not too bad, still more than I had intended. But it is a beast and exceptionally well made. Costs mount up a bit with shipment and duty though.

 

[Darren L]

I heard the Innersound Isis at a Hifi show, Michell Engineering were using a pair on the end of a full Michell system, sounded lovely with the bass driver integrating seemlessly with the ESL panel.
Probably the best affordable real world system on show that year.

 

[JemHayward]

I'm running modified Martin Logan Summits driving the bass at line level directly into the built in DSP - but rather than using the 25Hz and 50Hz trimmers on the speakers I use a miniDSP balanced unit with room correction determined by REW - this operates up to 380Hz. The panels are driven via my Radford STA25, and still use the passive x-over. I could go further but I'm reluctant to do any non reversible modifications to my speakers. They sound absolutely stunning.

 

[davidismynaim]

I heard the Innersound Isis at a Hifi show, Michell Engineering were using a pair on the end of a full Michell system, sounded lovely with the bass driver integrating seemlessly with the ESL panel.
Probably the best affordable real world system on show that year.

Interesting, funny, I have a Gyrodec, maybe I will pick up a pair of Michell Alecto if they are model B boards so I can get them updated with more power, as I have always loved the industrial design. but would need the extra power, the Nords are not too shabby especially now only focused on the bass.

 

[davidismynaim]

I'm running modified Martin Logan Summits driving the bass at line level directly into the built in DSP - but rather than using the 25Hz and 50Hz trimmers on the speakers I use a miniDSP balanced unit with room correction determined by REW - this operates up to 380Hz. The panels are driven via my Radford STA25, and still use the passive x-over. I could go further but I'm reluctant to do any non reversible modifications to my speakers. They sound absolutely stunning.

I was very tempted by a pair of Summits, but probably a little too big for my room and a lot more money than the Innersound, that were a bit if bargain. The Innersounds seem just about right for my room size. Interesting how you have these driven. I may try and figure out how to use Roon (my digital source) to do the DSP there and drive two DACs, that way I may be able to take the dbx out of the loop, compex to manage the vinyl source though.

 

[Darren L]

Interesting, funny, I have a Gyrodec, maybe I will pick up a pair of Michell Alecto if they are model B boards so I can get them updated with more power, as I have always loved the industrial design. but would need the extra power, the Nords are not too shabby especially now only focused on the bass.

John was using a Gyro SE with an SME v tonearm, Ortofon Rohmann? MC into his own phonostage, Orca pre and two stereo Alecto poweamps, I thought they were the mono blocks but was told that he preferred the stereo power amps and that the Innersound Isis was his new favourite speaker, he had used Quad ESL 63's since there release at home and when developing the Michell amps.
I was using a Gyrodeck myself at the time and was very interested in the Alecto power amps, hence the questions and conversation, it was also my first time hearing large electrostatic speakers coupled with a moving coil bass cone, it sounded great.