Jubilee, Khorn, Dx38, biamp & triamp guys.... question...

[Coytee]

Brett is looking to maybe bi/tri amp his Khorns.

He's got various items in his hands, including now, one of my Dx38 crossovers.

Right now, I think it's fair to say he's only experimenting to see if he wants to pursure bi/tri amping further.

So... the Dx is 2 in, 4 out BUT it has the parallel outputs.

I'm thinking he should be able to take one of the outputs, run it back into the second input and now, have 1 in & 4 out so he could triamp a single Khorn? (I think the answer is yes)

If yes, then what's next? Oh...I should mention that what ever type Khorns he has, his has the bare wire going to the woofer so he's got easy access to all three sets of wires. Seems there is no woofer crossover parts inside the bass bin.

On the Dx, if we designate the woofer is channel 1, midrange is channel 2 and tweeter is channel 3 then:

1. Where to cross each?

2. Any of those shelves?

3. Any PEQ's?

4. What kind of delay for the mid:

5. What delay for the tweeter?

6. What other items to deal with?

I know I've brought this up on more of an individual basis, I thought I'd bring it up publically so it's out in the open for anyone to comment and more specifically, for him to see himself.

[djk]

No delay is needed on the bass, so you can triamp a pair of Klipschorns with this piece by the expedient of a stereo lowpass filter at 400hz. All the other filters can be generated by the EV, just remember to subtract the latency time from the delays you need.

I have used a $30 car stereo crossover for the stereo lowpass filter at 400hz.

[Coytee]

All the other filters can be generated by the EV,

Which might be? (I'll admit I've not got the foggiest idea)

[djk]

Whatever you think for your horns and drivers, 400hz and 4.5Khz should work for most.

[Don Richard]

You should be able to loop thru a single DX-38 for tri-amping a single Khorn. If he's using K-77 tweets, be very careful. It would be very important for the tweet amp not to have turn-on or turn-off thumps, as they would sooner or later pop the little diaphragms. Since this is an experiment, put a 20 uF cap in series with the + leg of the mid driver, and a 4.7 uF cap in series with the tweet. This is common practice with hi-power sound reinforcement rigs, won't affect the sound but will help protect delicate diaphragms from low freqs and DC.

I am not familiar with the DX-38, but if it has selectable slopes, use 24 dB/octave. Use the stock xover points for his year Khorns, at least at first.

Good luck!

[djk]

If he just wants to fool around with tri-amping one channel, see fig. 6.3 on page 15 of the owners manual.

http://www.electrovoice.com/documents/ev/dx38_manual.pdf

[Coytee]

Yes, I was perhaps more aware of that ability than I had let on. Where my ignorance is coming into play is exactly what crossovers to use on the Khorns (mentioned above), does he need any PEQ's, any shelves, delay values?

In other words, I can help him program his Dx, I just have no idea of what ingredients need to go into it to do a Khorn properly.

[AltmanEars]

Yes, I was perhaps more aware of that ability than I had let on. Where my ignorance is coming into play is exactly what crossovers to use on the Khorns (mentioned above), does he need any PEQ's, any shelves, delay values?

In other words, I can help him program his Dx, I just have no idea of what ingredients need to go into it to do a Khorn properly.

What I'm beginning to find by reading a bunch of the responses in the forum is that many people go down the active path, do it poorly and decide its not for them. A few things I've learned in my travels:

1. At the inception of your active project it is probably better to use the same amps. This simplifies the setup process and allows you to perform a basic passive triamp test. The triamp passive test will tell you if the additional amp to speaker and amp to preamp cabling is an issue. Please note I have no experience with cheap y cords etc.. Ive only used preamps with multiple amp outputs.

2.Using the same amps sounds like one is suboptimizing but it helps with the listening tests. You have to get the critical crossover points correct by ear.

3. Always use the same speaker cables and interconnects - at the beginning of your process.

4. I've only used the really expensive spectrum analyzers but there may be software and the beringer 5000 test microphone which will allow you to take measurements in the listening room. This in and of itself takes experience since the flatest smoothest response doesnt sound the best.

5. In the cases I've run the passive settings for slope and crossover point are never the same you would use in your listening room -- but you need to start somewhere.

6. I have not experimented with time delays but in theory you may need some tailoring even if you align the acoustical centers of the drivers in your Khorns.

As an aside it would appear that people can disagree on what time alignment actually is. In my odd world you need to begin with the acoustical centers of drivers to have some shot of time alignment. There is another school of thought that as long as the front of the drivers are flush with the motorboard the system is time aligned. (Apparently this is a belief held in some parallel universe)

For reference, the attached picture is of a Living Voice horn where the designer paid attention to time alignment. The designers of the living voice claim the tweeter to mid alignment is significantly more important than bass to mid... (go figure)

Please note as far as listening is concerned, arranging the speaker so the acoustical centers of the drivers are correct, works in concert with having a crossover which has been engineered to be transient perfect meaning you need to run a series of impulse tests.

At this point we still have not addressed the power response of the loudspeaker or other very valid aspects of performance.

[djk]

The speaker shown may be aligned by a passive network on the woofer, though the off axis sound in the transition from the woofer to the mids will not be aligned.

If you mounted all the fronts of the drivers in the same plane and used digital delays it would not produce the same results (except on axis). Off axis sound would not be aligned, where as it would be if mechanically aligned.

Constant directivity horns with long 'tails' in the throat area have their own special problems as their apparent apex is different in the horizontal and vertical planes. The K402/Jubilee has the same apparent apex in the bass and HF, so a digital delay works in this instance.

[AltmanEars]

The speaker shown may be aligned by a passive network on the woofer, though the off axis sound in the transition from the woofer to the mids will not be aligned.

If you mounted all the fronts of the drivers in the same plane and used digital delays it would not produce the same results (except on axis). Off axis sound would not be aligned, where as it would be if mechanically aligned.

Constant directivity horns with long 'tails' in the throat area have their own special problems as their apparent apex is different in the horizontal and vertical planes. The K402/Jubilee has the same apparent apex in the bass and HF, so a digital delay works in this instance.

Yes you are absolutely right... I'm not sure you read the whole post --- the engineers did not think the mid woofer transition was that important --- at least as far as the listening tests were concerned. In the design phase they assumed it would be critical.

On one hand thats a neat looking speaker --- on the other LV has embodied virtually every high end cliche and put together an ambitious product --- who knows if it will sound good...

[djk]

Perhaps I wasn't clear enough.

I view a delay on the woofer as essential, and the mechanical mis-alignment as unfortunate.

If you examine this huge JBL cinema system, you will notice that even though delay units are readily available that mechanical alignment was chosen (even though it is much more difficult).

(photo from DB Keele site, ex EV, Klipsch, JBL)

[AltmanEars]

djk --- While english is not my first language I thought the word agree means harmonize or in accord. If you are looking for someone to disagree with you probably need to take it up with LV not me...But it appears even LV agreed with the technical premise you discussed.

In addition manufacturers often state some technical issue they can't surmount doesnt make any difference in listening tests. On the other hand there is room that they (LV) are being completely candid.

[Coytee]

I view a delay on the woofer as essential

Lemme ask this to clarify some of my own confusion.

(my reference point is a Khorn so perhaps another reference point might change the answer?)

I thought the woofer was the longest horn therefore it would be the reference point that all other horns would be delayed to match?

In other words, the woofer would have zero delay and the K400 would have 'some' (exact amount unknown to me) and the tweeter would have a little more than the K400.

This would in essence, shove the MR/HF back to meet up with the woofer. Am I misunderstanding something?

[AltmanEars]

I view a delay on the woofer as essential

Lemme ask this to clarify some of my own confusion.

(my reference point is a Khorn so perhaps another reference point might change the answer?)

I thought the woofer was the longest horn therefore it would be the reference point that all other horns would be delayed to match?

In other words, the woofer would have zero delay and the K400 would have 'some' (exact amount unknown to me) and the tweeter would have a little more than the K400.

This would in essence, shove the MR/HF back to meet up with the woofer. Am I misunderstanding something?

We are talking past each other on the thread. To answer your question ---with an active crossover you can correct for the delay and as far as it goes what you are saying is correct.. In practice the dynamic performance of the speaker at the various listening positions requires more work.

When you say "I'll loan my pal a crossover and with the idea that we will determine whether we want to go along this path to improve his system" is tantamount to saying I'm going to loan my pal a gallon of rocket fuel to determine if he should fly to the moon. In fact the most important thing you can do at this stage is to define a process for evaluating and testing the system.

Here is a good quote from a speaker designer ---

A Brief Digression about Crossover Design: There is misinformation promoted in some Internet news groups that all you need is the currently fashionable expensive driver and an off-the-shelf active crossover to equal $1,000 to $10,000 commercial designs. This, to be blunt, is just plain wrong. The most exotic and advanced drivers are notoriously hard to integrate into a speaker system, and professional designers know this. The best people in this field take anywhere from 6 to 18 months to design a system that is ready for sale, and that's with years of design experience and daily access to advanced test equipment.

If you found some unusual drivers on eBay, good for you, but now it's up to you to find a professional designer and pay them for their time (I am not volunteering). To give you a idea of what this might cost you, I generally charge US$20/hour for design services, and the XXXX took me 6 months to design (pretty fast for me), so by a quick reckoning that's $20,000 of my time, at least 80% of which was spent refining the crossover. Matching the crossover to the specific drivers in the XXXX took 25 years of experience, $16,000 of hands-on time, and $5,000 of test equipment. That was with drivers that were very easy to work with.

Here is a bit on process ----

Since speakers are electroacoustic transducers and antennas at the same time, they have complex behaviour that cannot be reduced to simple graphs or curves. Even the most sophisticated instrumentation only hints at what's really going on, so careful listening is still an essential part of designing a speaker system. I use a combination of listening to music and pink-noise, and measuring the speaker with several different MLSSA test modes, such as impulse response, group delay vs. frequency, frequency response at different angles, and the cumulative decay spectra.

Careful listening to pink-noise is a very sensitive way to discover resonant colorations (more so than music, and much more repeatable), but it can fail to detect notches in the spectrum unless they are very sharp and deep. So you have to be careful when you tune a system so you don't inadvertently create broad depressions. In addition, pink-noise testing tells you nothing about dynamic qualities, so you can end up with speakers that are smooth and inoffensive but don't sparkle and sing on real music. Still, pink-noise testing lets you quickly detect and remove resonant colorations; just alter the crossover and add or remove cabinet damping until the speaker really begins to sound like an actual waterfall.

MLSSA, FFT, LMS, or 1/3 octave measurements provide an essential cross-check to make sure that you're not subtly skewing the spectrum as your ear gradually adapts to the sound of pink-noise. (Adaptation is a serious problem with pink-noise testing. Listening and tweaking sessions should be kept under 10 minutes so your mental reference point doesn't begin to shift.)

All tests have their blind spots, so cross-checking is very important, especially when you listen to music. You may have to choose between a sense of verve and directness and a tuning that is relaxed and neutral; this is your call. The drivers in the XXXX are exceptionally flat, which makes the system tuning easier. If the drivers had large peaks like metal-dome tweeters, Kevlar, or carbon-fiber drivers, the tuning process becomes far more difficult, and requires a lot of experience in knowing what to equalize and what to leave alone.

In practice, subjective tuning results in a 3-way round of testing, using pink-noise, measurements, and music listening. This is the sequence I use:

1. Aim for the intended acoustic target slope (4th-order Gaussian or whatever) by using computer optimization with LEAP or XOPT, or use old-fashioned cut-and-try with many repeated measurements made at 2 meters distance at 0 degrees, 15 degrees, 30 degrees, and so on.

   (WARNING: Do not make system measurements at a 1 meter distance. For all multiway speakers, not just the Ariels, the crossover radiation pattern doesn't fully "gel" until you get at least 2 meters away. If you fine-tune the system at a 1-meter distance it will almost certainly be wrong at 2 meters. Fortunately, the measurements at 2, 3, and 4 meters are very similar, so the 2-meter measurment is valid for greater distances.)

2. Fine-tune the new crossover in half-dB steps by ear and repeated MLSSA, LMS, or IMP measurements. Keep doing this until you are satisfied with the overall technical and subjective performance.
3. Record the measurements, crossover description and topology, and the version number.
4. Have music-listening sessions using several amplifiers and a wide variety of sources. Instead of listening critically, ask yourself if you're enjoying what you hear. Do you feel the music? Does it move you? Focus on the emotional qualities, not just the usual audiophile sonics. In other words, what does it do well?

Go back to Step 2 until you feel genuinely satisfied that the whole system has reached its full potential. For example, crossover on this Web page is actually the 15th go-round using this multi-step procedure above. So don't expect perfection the first time around, and don't expect music-listening or measurement sessions to do it all. It takes both.

HOPE THAT HELPS

[Coytee]

Heh... I feel like I just took a sip of water from a fire hose!

Altman, this isn't directed at you specifically as much as it is an expression of a thought I've had during this thread.

This isn't rocket science.... it's not like nobody has triamped a Khorn... I would like to think that the basic ingredients are reasonably well known such that if someone took 3 amps, used "X" delay, used "X" crossover points and maybe one or two more ingredients... you would end up with a working, triamped Khorn. Perhaps it might need some tweeking to fine tune to your room or listening tastes....but you'd have a functional starting point.

Where's Maron when I need him...... Oh yeah.... he's over at AK muddling about in the HPM 100 forum..... [6] [A]

[Islander]

2.Using the same amps sounds like one is suboptimizing but it helps with the listening tests. You have to get the critical crossover points correct by ear.

It's often suggested that a bi-amped system can use a much lower-powered amp, often a small tube amp, to power the tweeters, but if a fairly low (300-600Hz) crossover point is chosen, the power demands for the tweeters and woofers are very similar. In that case, a pair of similar or identical amps, usually with a fair bit of power, will work much better than a pair of dissimilar power amps.

As well, matching amps should give a more consistent sound across all the drivers.

[6l6gc]

I just bi-amped my khorns this weekend, using DCX2496 unit (it has 6 channels so can tri-amp as well), and the DEQ2496 with ECM8000 as measurement aid,

I was curious to see what effect the delay might have, also wanted to be able to use that tube sound I love for the highs and that controlled SS bass for the lows. but ended up this weekend with both amps being SS due to a missing cable.

At this point of this experiment, I left the passive Klipsch crossover for the squawker and tweeter in place for protection, connecting that part to the high fr amp, and connected the bass bin directly to the low freq.amp.

Getting the levels right using two different amps was relatively easy, with pink noise and tones and the mike.

I started out with steep Butterworth(?) 48db slopes at 447hz, tuning the crossover point from about 380 to 550-600hz did not yield any significant changes
in how music sounded.

The automatic calibration of the DCX decided to invert the woofer, and apply 9msec delay on the high section, (an Altec 511b sitting on top of the high khorn section so maybe a little more distance from the bass which I thought should have been 7msec) .

Enabling disabling the delay gave a very subtle effect, when watching the speaker you can tell sounds are coming from the bass unit and the treble unit, but when delay is on, then more of the sound appears to be formed in front of the speaker instead of separately, but this was very very subtle, hardly worth the trouble of bi-amping, I also twiddled abit with the delay adding and subtracting msecs with no real audible benefits when listening to music. (perhaps plotting signal sweeps would have shown something, but we are listeing to music not excel sheets)

Later I ran quick tone test signal sweeps between 300-600hz, and by ear I thought I heard a dip at the crossover point. I played with the crossover points
the low part crossed at about 500, and the top being crossed at about 400hz overlapping until the dip was gone, it could be that 48db is too steep, and I should try 24db curves next experiment rounds.

also this time when I ran the auto calibration, the dcx decided not to invert the woofer, delay stayed the same.

my conclusion for this short weekend experiment is that if you like lots of knobs leds, DIY , and turning your stereo into a complicated spacecraft, then this is for you,
for audio Nirvana I'm not convinced there is any benefit apart from driving tubes for the high, and SS for the lows.
with both channels run with SS, there was no significant change in audio enjoyment worth the extra bother and expense.
Khorns seem to be perfect as they are, its true one can argue that I was still using the upper section of the passive crossover, but I doubt this would have made a significant change if at all. one day I might try tri-amping,better have a spare k-77around just in case, it is risky.

On another note, I am not familiar with the dx38 capabilities , but I find it odd that you might have a very expensive audiophile cd player with a special pure DAC to convert 44.1 to analog, only to be converted back from analog to 48khz for the dx38 internal process and then its own DACS back to analog, with the dcx unit, you can use direct digital at any data rate 44.1 to 96khz, from a transport, without this double (D to A and A to D and then D to A again) conversion. its only one D to A after processing. also one unit is enough for tri-amp, or bi-amp with sub or mid channel.

[AltmanEars]

Islander

The engineer's reccomendation was a sound one that works in practical terms --- the reason he does not like disimilar amps is because he wants to design the crossover points, slopes, amplitude, delays etc... without adjusting for the transfer function of amps with varying topolgies. Does that make sense? In fact it has nothing to do with power.

Not to say this is what you are hearing but there are many who state as you do and as I thought that you are better off with running a Khorn with SS bass and tubes elsewhere but some of the roughness one hears in the mid and high's are not artifacts of the amps but artifacts of the crossovers.

The other factor a really good engineer mentioned to me was that the mid and tweet of a khorn like any other speaker are not fixed resistors but will have varying impedance with amplitude. If used with a passive crossover the speaker may have a slight tendancy to sound brighter as amplitude increases.

[djk]

The DCX2496 has room for improvement, specifically the 17 $0.25 quality opamps and 15 polarized electrolytics in the signal path.

Easy to see why you are not impressed.

Most pro gear is little better, so I modify it.

[AltmanEars]

6l6

Did I really read your response correctly? You tried a bunch of experiments none of which included actually triamping and running the speaker active yet you are convinced active would not sound better?