drdna wrote:

Is it true that the words "neutral" and "dynamic" and "inner detail" have importance for you?

Kerry Brown wrote:

I used the term 'sophisticated' literally: so - phis - ti - cat - ed Adjective: 1. ( of a machine, system, or technique ) Developed to a high degree of complexity. As do you, I prefer multi-way horns so most DEQX based systems are not interesting to me but most of them are definitely sophisticated.

Romy the Cat wrote:

Topologically digital can’t attenuate (it means to filter)

Markus wrote:

Do you have a link to an explanation of this statement? Given the proliferation of digital volume controls, I'd like to understand more.

ACTIVE CROSSOVERS 

1) Loudspeaker drive units of different sensitivities may be used in one system without the need for lossy resistive networks ( and L-Pads ) or transformers

( DEQX lets me use 98 dB/meter/watt planar magnetic tweeters with 105 dB+ horn drivers ).

2) Distortions due to overload in any one band are captive within that band, and cannot affect any of the other drivers - eg. occasional low frequency overloads do not pass distortion products into the high-frequency drivers, and therefore instead of being objectionable they may, if slight, be inaudible.

3) Amplifier power and distortion characteristics can be optimally matched to  drive unit sensitivities and frequency ranges.

4) Driver protection, if required, can be precisely tailored to the needs of each driver ( DEQX cuts off low frequencies at 20 Hz to protect my subwoofer drivers ).

5) Complex frequency response curves can easily be realized in the electronics to deliver flat acoustic responses at the listening position. Inherent driver irregularities can be easily regularized ( the DEQX processor/crossover 'corrects' my horn's imperfect phase and frequency responses ).

6) There are no complex load impedances as found in passive crossovers, making amplifier performance (and whole system performance) more dynamically predictable. 

8) System intermodulation distortion can be significantly reduced. ( Less band overlap = less i.m. distortion )

9) Cable problems can be dramatically reduced.

10) Low source impedances at the amplifier outputs can damp out-of- band resonances in drive units. A passive filter may function as a buffer and prevent effective amplifier damping.

11) Drive units are essentially voltage-controlled. When coupled directly to a power amplifier, (most of which act as voltage sources) drivers are more optimally driven than with passive filters which can alter impedances between the source and load . When ‘seen’ from the point of view of a voice coil, passive crossover components represent an irregularity in the amplifier output impedance.

12) Direct connection of the amplifier and loudspeaker is a useful distortion reducing system. It can eliminate the strange currents which can often flow in complex passive crossovers.

13) Steeper filter slopes can easily be achieved without loss of system efficiency.

14) Low frequency to high frequency driver+cabinet time alignments are possible which, by passive means, would be more or less out of the question.

15) Drive unit production tolerances can easily be trimmed out ( = perfectly matched drivers ).

16) Driver 'drift' from aging ( less flux = lower spl ) can easily be trimmed out.

17) Subjectively, clarity and dynamic range are generally considered to be better on an active system compared to a passive equivalent (with the

same enclosure, and the same drive units). 

18) Amplifier designs may be simplified, sometimes to sonic benefit.

19 ) In passive loudspeakers used at high levels, voice-coil heating will change the impedance of the drive units, which in turn will affect the crossover termination. Crossover frequencies, as well as levels, may dynamically shift. Actively crossed-over loudspeakers are immune to such crossover frequency changes.

20) Problems with inductor location (to minimize interaction with drive unit voice coils at high current levels) do not occur.

Digital Active Crossovers 

A digital crossover with lower bit depth and sampling rate than the recordings it's processing won't deliver maximum sound quality; unfortunately my DEQX crossover is limited to 24/96 so it can't process hi-res digital files ( early DEQX processors were limited to16/48 ). 

Digital crossovers are expensive compared to active analog crossovers.

Digital attenuation is not a problem with 24 bit processors processing 24 bit recordings. Quantization errors, the only ones specific to digital filters, are not audible when this is the case. Even 16 bit processors can attenuate up to 8 bits without audible 'rounding' errors. 

In terms of dynamics, 6 dB of digital attenuation equals roughly a 1 bit loss of resolution and a 50% reduction of dynamic range. This also applies to analog attenuation . The solution is to use a crossover - digital or analog - with high voltage output. ( Sensitive systems like horn speakers must use amps with low input sensitivity, or you can use voltage splitters. I use voltage splitters. ) You get decreasing Sound to Noise ratios with lower voltage signals whether you use analog or digital filters.

Finally, if the DAC chips in a digital crossover are limited to a SNR of 120 dB, as they usually are, a 24 bit processor ( w/ a dynamic range of 144 dB ) loses 24 dB of dynamic range. In this case the DAC chips themselves add noise to the signal. So an analog crossover can sound better than a digital one if attenuation ranges greater than 24 dB must be achieved. If the range of attenuation is less than 24 dB, a 24 dB processor should give more than satisfactory results with 24/96 files.

Kerry

Kerry Brown wrote:

A digital crossover with lower bit depth and sampling rate than the recordings it's processing won't deliver maximum sound quality; unfortunately my DEQX crossover is limited to 24/96 so it can't process hi-res digital files ( early DEQX processors were limited to16/48 ).

Of cause a crossover sampling rate has absolutely no relation and no connection with recordings sampling rate. The facts that somebody insist I this relation is absolutely laughable.  

Kerry Brown wrote:

Digital crossovers are expensive compared to active analog crossovers.

Kerry Brown wrote:

A digital crossover with lower bit depth and sampling rate than the recordings it's processing won't deliver maximum sound quality; unfortunately my DEQX crossover is limited to 24/96 so it can't process hi-res digital files ( early DEQX processors were limited to16/48 ).

Kerry Brown wrote:

Digital attenuation is not a problem with 24 bit processors processing 24 bit recordings. Quantization errors, the only ones specific to digital filters, are not audible when this is the case.

Yes, it is what the people who sell digital toys to gullible and deaf audio people are trying to “publicly state” in order others to repeat it.

Kerry Brown wrote:

Even 16 bit processors can attenuate up to 8 bits without audible 'rounding' errors.  ).

Kerry, is it something that you recognize yourself or it is something the somebody told you?

Kerry Brown wrote:

In terms of dynamics, 6 dB of digital attenuation equals roughly a 1 bit loss of resolution and a 50% reduction of dynamic range. This also applies to analog attenuation .

What?!

Kerry Brown wrote:

The solution is to use a crossover - digital or analog - with high voltage output. ( Sensitive systems like horn speakers must use amps with low input sensitivity, or you can use voltage splitters. I use voltage splitters. ) You get decreasing Sound to Noise ratios with lower voltage signals whether you use analog or digital filters.

Kerry, do not even enter the conversation about S/N ratio. You have absolutely no idea what happen with digital signal at stop band.

Kerry Brown wrote:

Finally, if the DAC chips in a digital crossover are limited to a SNR of 120 dB, as they usually are, a 24 bit processor ( w/ a dynamic range of 144 dB ) loses 24 dB of dynamic range. In this case the DAC chips themselves add noise to the signal. So an analog crossover can sound better than a digital one if attenuation ranges greater than 24 dB must be achieved. If the range of attenuation is less than 24 dB, a 24 dB processor should give more than satisfactory results with 24/96 files.

Kerry, stop to reiterate the foolishness that you most likly do not understand yourself and make a simple listening test. I told you: take uncompressed file, reduce volume by any amount of dB and listen results. If you do not find that digital attenuation made any difference then… it makes no difference to ... you.

Stephano Two good ears has put a post on his site about his new 4 way passive xover.

I think this is a better direction than the digital xo.  The designer, Thomas, designed also the preamp and I guess he has taken into consideration the input and output impedances in order to make it work perfectly.  6 db only and independent volume control for each channel... perfect!

I would argue that a stepped volume control would limit the micro volume adjustments needed for a perfect integration of the channels, in such case I would rather used those ugly pots or maybe even the optical volume controls like the Lightspeed.  But the effort is great and in a good direction!

Internal Xovers on the coupling stages of the amplifiers, as Romy has it, works better IMHO, I have tried both and there is a certain insertion loss for a Line level passive xover,  but this also will allow the use of different amplifiers and even an amplifier tasting can be arranged, always a lot of fun!  I know Stepaho owns a lot of good quality amps!

Having played with a lot of amps too I noticed every amp has a different phase output, I have noticed that phase output becomes really important to sound, maybe even more than the amplifier itself, if the phase is off between two amps, the sound is terrible, if you use identical amplifiers, it is easier to multiamp with good results.  Of course, phase problems can be adressed by precise time alignement, but a new change of amplifiers, will need a new careful time alignment, and it can become quite complicated.

Kerry:  Can you put a simple series xover on your system, speaker level based on the original data from Bruce Edgar.  Try it against your wonderful DEQX and see what you like better:  invite some friends over to hear their input, it always helps...

Jorge,

You're right about using identical amps. No doubt.

I have not used Dr. Edgar's passive network but I have tried conventional passive networks on Edgarhorns. They worked alright.

And I have used conventional filter networks on other horn systems - including Altec VOTs, JBL Hartsfields, Jensen Imperials and EV Patricians - with OK results.

I have used passive line level networks on tube amps driving Edgarhorns and the system sounded better than it did with conventional speaker level networks.

I have tried the Goldmund active analog crossover and a Behringer active analog crossover and Behringer's best digital active crossover, the DCX whatever it is. They all worked OK, the DCX sounded pretty good. All the active crossovers were more flexible, less problematical and more practical than passive line level filters even if most did not sound as good ( at least in some ways ).

Next I tried the first generation DEQX unit, the PDC 2.6p which was a big step up from the other active crossovers. Over the years DEQX provided online software and firmware updates, each of which improved sonics. The update to 24/96 was quite an improvement. 

Finally I moved to the DEQX HDP3 w/ transformer-balanced outputs and Earthworks calibration microphone, another big step up. It really does make the Edgarhorns sound great. 

I am satisfied for now, but I am always open to more improvement, even if it's from a different machine. I would like to try a couple of Pass Labs XVR1 active analog stereo 2-way crossovers - but you need two in order to tri-amp, three are required to quad-amp, and they cost $4,000 each.

I do have several good friends, musicians with very good ears, who really like the sound of my Edgarhorns. This group includes a very good friend, an acoustic guitar player who audits DIY recordings of himself playing on my system because my horns sound better to him than his own expensive exotic headphones. My horns sound about the same as his STAX 'phones actually, maybe not quite as smooth and silky, but the Edgarhorns can flap your pants, project a realistic image and don't make your ears sweat.

Dr. Edgar has visited here, so has Alon Wolfe and Steve Schell. They have all listened to my DEQX processed Edgarhorns and told me they sounded good. 

Dr. Edgar does not like the way I use my modified Edgarhorns, in a small room, sitting close up, but admits my setup sounds very good. For studio monitors. 

Of course, it's Murphy's Law that as soon as audio guests depart you discover miswired speakers, loose interconnects etc., so none of those guys ever really heard my system at it's best. Not to mention that several other upgrades since any of them were here last have taken the system to new highs. So to speak.

Anyhow, the invitation still stands for any interested listeners to visit and listen to my digital-infected Edgarhorns. If you're anywhere near SF it's worth the drive. 

I think so anyway.

Cheers,

Kerry  

I am not completely thrilled with TwoGoodEars new crossover.

http://vinylsavor.blogspot.com/2012/01/making-of-line-level-crossover.html

First of all , Stephano has a preamp with tube out stage.  The guy in his post says that the line stage has low output impedance but I did not see the line-stages with single out tube to have output impedance low enough to drive 4 passive filters, 100-300R is not low enough, at least if Stephano goes for full ULF and very peaky about getting max dynamics.

The Stephano crossover as I hope is active and it has a buffer stage after filters. So, the filters are passive with buffers. This is kosher but the question is what the buffers are? The quality of the buffers is VERY important in this situation but the best would be not to have the active buffers and to have the crossovers line-level passive. For sure in that case the filter shall sit at the amp input – so bye-bye the sexy box with 4 filters and bye-bye the internet pictures. If Stephano crossover has no buffer stage after filters (and I do not see it on the picture) then how they regulate 12dB gain after the filters. If they do it with the rotary switches that switch the autoformers taps then it is possible but I personally do not buy it. I had a lot of debates in past with people about the autoformer volume attenuation and I am not exactly a huge fun of them. Yes, they can attenuate but they do not drive load as good as other methods. If they use the autoformer attenuation then the filters drive the cable to power amp via the autoformer – this is very far from optimum situation in my view.

What I would like to see, from a perspective of ultimate organization, is the very same filters but sitting right at the Stephano’s power amp imputes, or even preferably in the power amps. There are absolutely no needs for the filter to drive any load and there is no need to be in a separate centralized box.

From a larger perspective I am not sure if the line-level filtration will be reasonably in a long run in Stephano’s case. He use Goto drivers that have notoriously low power handling and there are a lot of people out there who did burn out Gotos, particularly HF and MF. With SS, direct-coupled amps that Stephano uses and line-level filtration the vulnerable Goto drivers will beleft with no protection at all. Stephano has to be VERY careful to use his playback in this configuration and I do not know if it will be practicable.

Anyhow, they are the thoughts at the top of my head. BTW, pay attention what they did – they model the filters via digital crossovers and then replace them with analog filters. This is right direction to go. For sure to change anything from this point will be a main pain in ass but it comes with the territory.

My main interest in the whole project is to see how they implement the MF high-pass filter. I have a feeling that they use a cap but I would like do not see a cap in there. I question the need to use the low-pass filter on the MF channel. Why would one need it and why we do not let the MF to decay naturally? I do not argue this as it would need to know the character of Goto MF driver at very top but I wonder of Goto MF has any own problem at 10-12K the force Stephano to roll off the driver with coil and do not let it to roll off naturally. Stephano uses long Goto MF horns hat do the HF roll off, so why he need to an electrical roll off? For sure I would like to see what they did with HF high-pass filter, is it C filter or RL filter? I hope it is RL but then what base impedance the use?

Anyhow, it is a good project but I might be not the “perfect” project from APPLIED perspective.

Jorge,

You're quite welcome to visit any time you are in the SF Bay Area.

There's a photo attached to this post of my Blokhorn system ( modified Edgarhorn System 80 ). 

The drivers are as follows.

(2) Hi Vi Planar RP2 PRO magnetic tweeters from 5000 Hz on up  

(2) JBL 375s on the tractrix Blockhorns, 500 Hz - 5,000 Hz 

(2) JBL 150s 4Cs on the Edgarhorn 80 Hz bass horns, 80 Hz - 500 Hz 

(2) JBL E145 18" woofers on the Edgarhorn Super Seismic folded horn subwoofers, 20 Hz - 80 Hz

I lucked out at a thrift store one day years ago and bought a mint condition Metregon with the 375s and 1504Cs. Cheap. When I pulled the drivers from that box, they looked new, perfect. I will never sell those JBL drivers, they all original, work great and 'match' each other exactly, even though they sport old ALNICO magnets.

The tweeters are in 'temporary' enclosures, I am working on something better looking but they sound fine as they are.

The Bloklhorns were CNC'd from a laminated-MDF block. There's another photo attached of the back side showing the JBL 375.

The 80 Hz bass horns are mass loaded - all voids filled with clean dry sand. Granite tops cover the fill ports I bored.

You can see part of one Seismic Sub to the left of the horns, there are two - they also serve as supports for a video screen ( which does not hurt the sonics as far as I can tell ).

You can also see a little bit of the shiny red solid-core speaker wire I use, Paul Speltz's Anti-Cable. The interconnects are all Blue Jeans Cable XLR type.

The little aluminum box on the upper shelf with the blue LED is a NuFrorce mono amp, one of two. To the right is a Benchmark ADC1 which bypasses the HDP3 analog-to-digital converter for phonograph and R-t-R analog sources.

The DEQX HDP3, one of two, is the black box with yellow and blue LEDs is on the shelf below.

A PS Audio PWT and PS Audio PP5 are atop the next shelf.

Below that is my Nuforce 7-channel HT amp - 6 channels power the low bass horns, upper bass horns and the tweeters - the multi-channel amp is fitted with exactly the same Ref v3Vse circuit boards as the 'Class D' NuForce mono blocks - the only difference is less capacitance in the PS.

As you can see I have a HT setup in the same room. Those Gallos work very well, sound good.

Cheers,

Kerry

Kerry Brown wrote:

Jorge, You're quite welcome to visit any time you are in the SF Bay Area. .... The little aluminum box on the upper shelf with the blue LED is a NuFrorce mono amp, one of two.  The DEQX HDP3, one of two, is the black box with yellow and blue LEDs is on the shelf below. ... Below that is my Nuforce 7-channel HT amp - 6 channels power the low bass horns, upper bass horns and the tweeters - the multi-channel amp is fitted with exactly the same Ref v3Vse circuit boards as the 'Class D' NuForce mono blocks - the only difference is less capacitance in the PS. ...

Hi Scooter,

Thanks for joining the discussion. My replies to your comments are below, please excuse the cut-n'paste.

Thanks for taking the time to post more details on your set up and photos. 

You are welcome. I would like to see and read about your system as well.

This is a good learning process for everyone so please take any comments as free debate and not a personal critique. 

I agree, I have no problem with debate and I usually try to avoid offending anyone or taking offense in the process. However, metaphysical debate only goes so far. How many angels can dance on the head of a pin ? The only real test of any subjective opinion is objective observation using the Scientific Method. Each and every opinion and or belief system can and should be challenged, including mine.

Maybe once you are happy with the fundamentals of your system, which the DEQX can help with, you consider a more traditional approach. 

I am already happy with the fundamentals of my system and I have already tried more traditional, more politically correct methods. I have tested many passive filtering networks and many different types of amps.

1. Digital processing. I know you are heavily invested in that box and it provides some convenient features. 

Yes, and the features are more than just "convenient".

The trade off is that you are settling major constraints that you can not overcome. Digital processing just kills sound in unrecoverable ways.

Again, the proof of the cook is in the pudding. In spite of political, philosophical and technical objections - all metaphysical at this point in time - and your contrary opinion, my digital processors make very good recordings played back on my system sound very good. Poor recordings sound poor, excellent recordings sound excellent. It's an undeniable fact, and if you could hear it for yourself I wager you'd agree. This is Objectively So. My system has objectively neutral tonal balance, objectively excellent dynamics, objectively confirmable PRAT, etc., etc., etc..

For example, remember most of the music you are listening to has already suffered digital processing, perhaps several rounds of it. Processing a second (third...) time causes massive problems from a mathematical perspective. Effectively you are taking a compromised source assembled with from sample data points and then doing that again. Lots of data is lost forever and new data extrapolation has varying degrees of error. A simple sine wave is easy to reproduce with a limited number of sample points. Music is not. There are other technical problems but I suspect this is among the most insidious.

I get what you're saying, I am aware of the technical objections, I know about jitter, I know what happens at the stop band with digital crossovers, but my system still sounds objectively excellent. 'Cold' or 'dead' or any other negative adjectives do not apply to my system's 'sound'. In fact, my system has no 'sound' it gets out of the way so you can hear what the recording sounds like. Neutral.

2. "Class D" Type amps are an interesting beast. 

I agree.

I have listened to a lot of them and like some of the conceptual ideas. 

I have listened to, and owned lots of amps, both solid state and tube, push-pull and single ended. I have not listened to a lot of Class D amps actually, they are never used at shows and I don't know anyone personally who owns any. I like them conceptually too, but I care less for the concept and more for the results.

Unfortunately I have not ever heard a decent sounding one. 

You should drop by sometime and listen to my NuForce amps. They sound very good.  By the way, I am not the only one who likes them. I know reviews are suspicious in general, subjective, but it means something when so many people like Nuforce amps so much.

Like the DEQX, "Class D" sets major technical constraints on your system that limit performance significantly.

In your opinion, but my system can go toe to toe with any system of any style in a similar room. And like I keep saying, if you doubt me, come listen for yourself.

Stupidly, I purchased some Linn "Class D" amps from a distributor for a small room once. They looked great, were very portable, multi-voltage, and sounded just terrible. 

Sorry to hear that. I have never owned any Linn products. NuForce Class D amps operate differently btw than other Class D amps. Folks seem to like them better than than ICE amps for instance.

However, I had one very interesting observation living the "Class D;" plugged directly into the wall socket, they always sounded the same, regardless of day or time of day. That is the only audio gear I have ever encountered that was so consistent.

My NuForce amps also sound the same pretty much, regardless of time of day, but they do sound better after a short warm up, maybe 30 minutes or so. I leave mine turned on all the time. Anyhow, maybe Linn just had a bad product. It happens. I'm sure there are Class D amps that do sound bad, based on what I have read. Or maybe the Linn Class D amps were too accurate for your taste and/or favorite recordings.

One last comment. My preference, as I have stated, is for accurate playback. Nothing subtracted, nothing added. No extra warmth, or reverb from tubes or ported bass. No euphonic overlay. I want to hear what's on my recordings. I like to hear edits and drop ins. I like to sonically 'see' the musicians and hear all the little mistakes. Fingers sliding on guitar strings. Spittle tone from trumpets, all that good stuff. If you like the sort of euphony you get from bi-poles dipoles and panel speakers you might not like my 'ruthlessly revealing' system. 

I bet most anybody would like my system though with the right recordings. If you listen to a good, minimally processed live recording, recorded either on stage or in the studio on my stereo it sounds like it should. Real. Very good recordings sound very good, bad recordings sound bad. My buddy's minimalist DIY digital recordings sound just like he does. Live. This is immediately obvious on my system. 

Here's a test for you. Listen to a recording on a good headphone system, try STAX. Then play back the same recording on your stereo. 

It's not easy to match the overall sonic quality of good headphones. Most loudspeaker systems fall far short. Far, far short.

Ignore things like imaging. Concentrate on tonal balance, dynamics, detail retrieval, etc.. If your system sounds anywhere near as good as a pair of STAX headphones you're doing well.

This is not to say I like headphones. I don't. I like loudspeaker systems. But, headphones are a very good reality check.

Cheers,

Kerry 

scooter wrote:

However, I had one very interesting observation living the "Class D;" plugged directly into the wall socket, they always sounded the same, regardless of day or time of day. That is the only audio gear I have ever encountered that was so consistent.

Kerry Brown wrote:

Again, the proof of the cook is in the pudding. In spite of political, philosophical and technical objections - all metaphysical at this point in time - and your contrary opinion, my digital processors make very good recordings played back on my system sound very good. Poor recordings sound poor, excellent recordings sound excellent. It's an undeniable fact, and if you could hear it for yourself I wager you'd agree. This is Objectively So. My system has objectively neutral tonal balance, objectively excellent dynamics, objectively confirmable PRAT, etc., etc., etc..

Kerry Brown wrote:

Here's a test for you. Listen to a recording on a good headphone system, try STAX. Then play back the same recording on your stereo.  Ignore things like imaging. Concentrate on tonal balance, dynamics, detail retrieval, etc.. If your system sounds anywhere near as good as a pair of STAX headphones you're doing well.

We have tested live recordings against live sound, a recording of a jazz singer was done on Reel tape on an Ampex ATR modded machine with Fluxmagnetics heads etc.  The microphone used was the legendary Telefunken stereo tube mic. no post production no compression etc.  The singer was crying when she heard the recording through the horn system. she said she had never listened to her real singing voice, she had also just spent a bunch of money in a "pro" studio and the results were crap.  The monitoring was done with the best vintage sony headphones.

Now the same recording played through minimonitors would have saturated immediately!  Listening to the very same "master tape" on a couple other horn systems was also very interesting,  they all sounded pretty much the same,  very good!  Up close it was like the girl was singing on your lap, far away it was like you were sitting at the concert,  just real!   Yes even Girl with guitar with these dynamics would be very hard for a "normal" system.

That being said, I dont really think a live recording is a good test for a system (no pun intended) it is just so good and so direct, that almost any fairly well set up system will do a great job!

Most of my set up tests I do on digital because it reveals the shortcomings of a system very fast!  If the system is not at its best, digital will be unbearable, but maybe vinyl will sound ok, and a good tape will sound great almost anyway you put it!

When we got the DCX digital xover (not DEQX)  the main idea was to use it to play around with Xover points and xover slopes to see what we could use better.
The system it was hooked to was multiamped,  we had Audio note P4 monoblocks for the mid horns with compression drivers, we had an 845 SET amp on the UBH, a First Watt F3 amps for tweeters, the Bass was linked to the UBH channels with a pair of sub amps with internal active xovers.  A lot of care was taken on the set up and a lot of time was consummed testing it.  We thought the sound was really good!  But indeed there was something missing,  thats when we would trimm here and add there and we would not miss the "thing" so much.  Everyone who listened to it was amazed!  On one meeting with very experienced listeners an idea appeared, we started commenting how we liked some things it used to do better without the DCX,  it actually came from a friend who was the strongest supporter of the digital xover.  So they asked me "how difficult would it be to hook the old xover back in?"  It would take a couple of minutes, but it wouldnt be a fair test since we would not be multiamping!  the xover is designed for using just one amp! 
So we went ahead, turned off all the amps, recconected just the 845 SET amp to the series xover, allowed it to warm up a few minutes and played the same track we were listening to:  There was no question, the xover brought back life to the system in every aspect! Even with just one amp!!!
The difference in sound was so huge, that all the "investigation" about xover points was useless!

I also tested a  few SS amps, my favorite is the Chord amp, which I believe has some sort of digital power supply, it is beautiful: clean transparent and very detailed, very! But when I listened to a well designed SET amp (diy by someone else) next to it, there was no comparison,  yes the Chord amp made no mistake, and everything was right there, but it was cold, mechanical.  The SET amp did the same detailing, the same dynamics but with better phrasing of the music, with a warmer touch,  the SS amp was like having the best sex in you life, the SET was like having the best sex in your life, with some one you love!
I am not against the use of good SS amps though!

Kerry, I think when you ever go back to a normal xover, you will be in for a good surprise!  Dump the DEQX and get a lot of money for it!

What RtR machine do you have?

It is all a trip, and your trip with DEQX is not over yet and your are having a lot of fun!  enjoy!

Jorge,

I know what you mean about horns, Living Presence. I love what my horns do. Palpability. Solidity. In an invisible sort of way.

I have two Ampex 300s downstairs, an Otario MX5050 and a Nagra V-S. I have lots of old commercial reel tapes too, 2-tracks and 4-tracks, most of the RCA Living Stereo and London catalogs. Some reels sound great, others not so much, some sound awful.

As far as excellent recordings ?

A Blu-Ray DVD of Monsters Inc. looks good even on a standard def small screen TV. It looks better on a big screen HDTV. But it does not look really good until you project it in 1080P on a 9 ft. screen.

Same thing with excellent audio recordings, their quality is discernible even on low res systems, but they don't really shine until they're played back on a high res ( = accurate ) system.

Have never had the good fortune to try a Chord amp but I am sure they sound good.

Been there and done passive crossovers and single amping. Tell you what though, I will try a passive crossover if you try a DEQX HDP4. 

That DCX thing did not work all that well for me. Maybe the mods you did improved the sound of your Behringer processor, but mine really did add a 'digital' glaze. 

I would love to commission 8 identical 845 or 211 or exotic transmitting tube set amps made to my specs, low gain, balanced, etc., but can't afford a project like that. And I would have to install some sort of no-noise air conditioning system to fight the Death Valley like heat they would generate. Not to mention the electric bills.

The NuForce amps are a low cost alternative that work great.

Cheers,

Kerry