Bi-amping K2 S5500

[Peter W.]

I recently traded-in my S3100 MKII for the K2 S5500. Could someone please help me find the Operator’s or Owner’s manual for the K2 S5500? Thank you.
I’d like to bi-amp the S5500 and there is a bi-amp switch on it, but I read from Mr. Greg Timbers comment to JBL 4345 Club that it is better to “Get rid of the bi-amp switch. Hardwire it in which ever mode you want it. The switch is not that great.” I wonder if this recommendation also applies to the S5500.

[BMWCCA]

I recently traded-in my S3100 MKII for the K2 S5500. Could someone please help me find the Operator’s or Owner’s manual for the K2 S5500? Thank you.
I’d like to bi-amp the S5500 and there is a bi-amp switch on it, but I read from Mr. Greg Timbers comment to JBL 4345 Club that it is better to “Get rid of the bi-amp switch. Hardwire it in which ever mode you want it. The switch is not that great.” I wonder if this recommendation also applies to the S5500.
The manual should be here: http://manuals.harman.com/JBL/HOM/Owner%27s%20Manual/K2-S5500-om.pdf

Looks like you'll need an electronic crossover though.

On the 4345 the switch looks like an ancient device with a huge rotary contact plate, leaves, and, as I recall, even some ball bearings. Lots of places for high-resistance connections particularly given it's occasional use. I'm sure the K2 uses something a bit more modern.

[Peter W.]

So much the better if I don't have to make any changes to the bi-amp switch. I do plan to use the DEQX HDP-3 for the bi-amping and room correction.

[Robh3606]

You need to use specific Voltage Drives to replicate what the passive crossover does. Do a search for DX-1 and you should find the correct Voltage Drives. The DX-1 was the JBL crossover used to Bi-Amp those speakers.

http://audioheritage.csdco.com/vbulletin/showthread.php?t=1908&highlight=DX-1

Rob:)

[Peter W.]

You need to use specific Voltage Drives to replicate what the passive crossover does.
http://audioheritage.csdco.com/vbulletin/showthread.php?t=1908&highlight=DX-1

Rob:)

Thanks BMWCCA , Rob for the helpful information. The DX-1 with the S5500 card is hard to get. Base on what I read here and room correction is essential for my listening area, I have purchased the DEQX but have not set it up yet. The DEQX may not replicate what the passive crossover does, but will it still work?If not, how can I make it work its best?
:)Peter

[4313B]

The DEQX may not replicate what the passive crossover does, but will it still work?If not, how can I make it work its best?Try to get it to yield the same voltage drive as shown in that thread. Once you get the DEQX and start playing around with it you'll see how to manipulate its voltage drive.

The DX-1 with the S5500 card is hard to get.Yep. Those who have them and know what they have won't part with them. They aren't all that versatile compared with alot of the current active offerings on the market but they sound several orders of magnitude better. If I remember correctly Levinson made them.

It's rather a shame that several hundred of them got shredded in Singapore by mistake. The President of JBL Consumer was all set to supply this forum with as many as we wanted at Factory cost (that's below Dealer cost) but then when it came time to ship them they didn't actually exist. It came to light that they had all been destroyed. :rotfl:

[K2-enthusiast]

So much the better if I don't have to make any changes to the bi-amp switch. I do plan to use the DEQX HDP-3 for the bi-amping and room correction.

Most interesting combo!...we may have a couple of tips to share with your K2+DEQX setup.

Down under, in recent years, we have much success running the Project K2 S5500 and S9800 with DEQX (both PDC 2.6P and HDP-3) in Full-Digital tri-amp active crossover setup.

In regards to your concerns with the Bi-amp switch, with S5500, we went with the by-pass approach to hard-wired the bass driver directly to the amp. The speaker cable goes thru the rear port. We get much better bass control this way. We are now running 600W amps to drive the bass drivers (twin McIntosh MC7300 in mono-parallel mode; one channel per bass driver) for the S5500; for the S9800 we run KRELL Evolution 600 monoblocks.

For the high-frequency compression drivers, best results were found when we run with the ultra-high bandwidth Goldmund JOB4 module. Here, we use StellaVox PW1 monoblocks on the S5500 with excellent results; on the S9800, we use Goldmund Telos 250 with equally impressive results.

For the S5500, we also augmented it with a pair of UT045Be, which runs on passive crossover with the unit, to extend the high-frequency response. It made a huge improvement...definitely recommend this! The UT045Be is driven by another pair of StellaVox PW1 monoblocks.

Assuming you've got good amps and quality source, the key to success with this combo, boils down to two main aspect:

(1) Running the entire setup in Full digital mode at 24bit/96kHz;

(2) Calibrating the DEQX correctly using a microphone with extended response;

The Project K2 S5500 & S9800 when driven in a full-digital active crossover setup, takes on a completely different character when compared to them being driven in passive crossover setup. When you have the DEQX setup correctly, it will sure to make you smile! Guaranteed jaw-dropping results! :)

We noted with the DEQX unit, for utmost transparency, it is best NOT to use its digital volume control, analogue input/output, A-to-D & D-to-A converters as they are not exactly the best...decent as they are, it is always a compromise. This means going with digital input to / digital output from the DEQX unit. Just use the DEQX as a pure-digital processor (w/o digital volume control) and it will sound extremely transparent! The Digital Output Board is an option which you can get when purchasing/upgrading your DEQX unit. It is definitely worth it as it completely elevates the performance.

To control the volume without losing resolution at low volume, we are running with Goldmund Universal Preamp, with excellent results! Both the Goldmund SR8 and Mimesis 30 sounds equally good in this setup. Note: The Goldmund unit will convert any analogue or digital input into PCM 24-bit/96kHz with great precision. Once this is achieved, all signal transmission between Goldmund->DEQX->Apogee will be fully PCM digital.

On the DAC end, we are running with Apogee DA16x, which provides 16 channels D-to-A conversion at 24bit/192kHz...however, in our setup, we only run it in 96kHz (sounds good enough to our ears).

The DEQX is capable of running a steep crossover slope of -300db/oct. For both K2 setup, we run a -132db/oct crossover at 800Hz and get DEQX to time-align the drivers and achieve flat response over 20Hz - 40kHz during calibration over the 6 partitioned frequency regions we have defined.

One final note with the DEQX calibration, ditch the standard Behringer mic that comes with the unit and get yourself a proper Earthworks M50 mic. This is what makes or breaks the DEQX calibration results with the K2s. The calibration done with the M50 (even without the calibration file) sounds way, way better! Also, make sure you calibrate the amp's gain to the closest db, between the tweeter amp and the woofer amp...the best DEQX calibration results comes when both are about the same.

In retrospect, comparing what the Project K2 sounds before and after this full-digital active crossover make-over, it would be like comparing Heaven and Earth...simply no comparison! We would not look back to the days when the K2 were being driven passively...what a waste of the K2 potentials...

If you think the K2 sound good in passive crossover mode, wait till you hear it sing in full-digital active crossover with DEQX :)

K2 + DEQX (In full-digital active crossover mode) -> Way to GO!

PS. With the DEQX calibration, there are a couple of tricks to know. If you are not getting a 38-42db confidence factor after the calibration of a particular channel, it may be an issue. Let us know and we can provide you with some tips.

[PP_65]

I've just bought a pair of K2 S 5500, I plan to actively bi-amp them with two TACT 2150 , I have a question about slopes , the manual speaks of "third order crossover at 800 Hz" , is this value correct ?
Thanks .

[Mr. Widget]

Most interesting combo!...we may have a couple of tips to share with your K2+DEQX setup.Interesting post... I just bumped into it.

I used a PDC 2.6P for a number of years. Mine did not have digital outs and I often wondered if the sound might not have been much improved with a much higher end A to D on the front end and external DACs... the DEQX is pretty good with a digital input and pretty weak with an analog input. I always felt a better DAC would help.

As for speaker calibration... I am sure the better mic would help under ideal situations, but for me, I was never able to take my massive horn loaded speakers outdoors, or able to remove the room's influences. I had better luck using a separate measurement system time windowed and then manually controlled the DEQX.

I never was happy with their "room correction". It seemed to me that the whole system was designed to work best with small stand mounted mini-monitors and a sub... I think the speaker and room calibration would have been much more successful in that scenario.

Thanks for describing your setup... sounds very interesting.


Widget

[Peter W.]

The Project K2 S5500 & S9800 when driven in a full-digital active crossover setup, takes on a completely different character when compared to them being driven in passive crossover setup. When you have the DEQX setup correctly, it will sure to make you smile! Guaranteed jaw-dropping results! :)

:bouncy:I am so glad that you are sharing your experience in K2 S5500 + DEQX. I have already got the DEQX HDP-3 with the Earthworks DM30. I just haven't got time to set them up yet. My system will be set up as follows and I welcome all your comments:

Accuphase DP85 SACD/CD player ; Wilson Benesch Circle+Linn Linto LP
First Sound Presence Deluxe MKII preamp
DEQX HDP-3
Master Sound Reference 845 power amp for low frequency
Master Sound Mono 845 power amps for high frequency, each channel uses two 845 tubes, parallel single ended, with about 40 to 50 wpc.
K2 S5500 + Pioneer PT-R100 super tweeter

I shall have more questions when I start setting the system up. My first question is, if running the entire setup in full digital mode at 24bit/96kHz is best, should I use the DEQX's preamp in place of the First Sound preamp?If I do so, I will be using the DEQX's digital volume control which is also not recommended. :confused:

[K2-enthusiast]

Interesting post... I just bumped into it.

I used a PDC 2.6P for a number of years. Mine did not have digital outs and I often wondered if the sound might not have been much improved with a much higher end A to D on the front end and external DACs... the DEQX is pretty good with a digital input and pretty weak with an analog input. I always felt a better DAC would help.

As for speaker calibration... I am sure the better mic would help under ideal situations, but for me, I was never able to take my massive horn loaded speakers outdoors, or able to remove the room's influences. I had better luck using a separate measurement system time windowed and then manually controlled the DEQX.

I never was happy with their "room correction". It seemed to me that the whole system was designed to work best with small stand mounted mini-monitors and a sub... I think the speaker and room calibration would have been much more successful in that scenario.

Thanks for describing your setup... sounds very interesting.


Widget

Definitely agree with Mr. Widget’s assessment of DEQX’s issues and challenges.

From an end-user perspective, if we were to rate the DEQX’s issues in descending order of significance, these will be:

(1) When running in full-digital mode, the “loud” (digital) pop that can occur, when turning the unit on/off and occasionally during certain calibration phases;

(2) Sound quality of the D-to-A converters and output stage;

(3) Loss in resolution when the digital volume control is engaged;

(4) Transparency of the A-to-D converters;

(5) The calibration file that comes with the Earthworks M50 mic, which simply does not work. And DEQX is not doing any follow-up work on this issue, as the user(s) impacted by this issue is minimal (actually, only 1 according to the list of calibration files issued on their website). Having said that, we have no issues with getting good calibration results with the M50 even without the use of calibration file.

(6) Heat issue. Having realized that DEQX features twin high-speed SHARC DSPs and is essentially a computer, we have to accept the fact that this number crunching process will generate heat. Having said that, the unit seems to run ok (despite running very warm) in Oz Summer, even in ambient temperature in excess of 40C.

The DEQX as brilliant as the concept is, it’s not perfect in its execution. To make the unit affordable, the production units have to live with certain economic constraints. If it is was designed/manufactured by one of the major Japanese Audio companies, this may be a different story and end-user experience altogether… As end-users that supports this technology, we are fully grateful to Kim Ryrie (CEO of DEQX) in bring this revolutionary technology to the market. And we respect the challenges he faces and design compromises/balance he has to make.

In our experience, to gain success with the DEQX deployment, the key to success is to fully understand its strengths and weakness. To fully exploit its strength, whilst suppressing its weaknesses in our setup.

Issue (1) is certainly the most important one on the list. However, this issue generally applies to any active digital crossover setup where the tweeter/woofer amplifiers are set at full maximum or close-to-full-max gain, with drivers exposed to the full force of the input signal.
So here is the warning for those who are considering the path with active digital crossover setup: Safety always goes First! <- We simply cannot emphasize this aspect more enough.

ALWAYS ensure signal stability (eg. Digital signal-lock is achieved at DAC end) BEFORE turning on your amp…otherwise, disastrous consequences can follow. This applies not only to normal listening sessions, but more importantly, during the calibration process. Whenever there is doubt, turn off ALL your amps, check the DEQX calibration GUI screen for a lock on the Clock-signal before proceeding (ie. Especially during the transitions from screen to screen during calibration). With regards to this issue, we would have hoped that DEQX would have addressed this major concern their customers have by now…unfortunately, this issue is still a very real threat to us all, even with the HDP-3 implementation. We can only speculate that not many DEQX users that run their setup in full digital mode to create sufficient number of complains.

Most members in our K2 club have learnt about this issue the hard way…dearly. For me, when this issue hit me during one of the calibration session, it blew the voice coil on one of my JBL UT045Be unit, with not just a loud pop, but an ascending high-pitch whirling signal! It was a truly scary experience…my concerns were not only for the unit itself, but also for suffering permanent hearing loss…and certainly a costly experience as well! This happened when I was running the super-tweeter in active crossover setup. Since the accident, I have decided to run the UT045Be in passive mode and utilize the third DEQX channel for subwoofer integration, which the DEQX does exceedingly well! Another mate was running the DEQX on his KRELL LAT-1000 speakers (prior to upgrading to his current K2). He blew his tweeters 6 times before giving up on his KRELL+DEQX setup! We now run a series of verification checks on our “pre-flight” checklist, prior to powering up the system (or performing calibration). Some of our members in our K2 club are in the process of getting their pilot’s license and have commented that our K2’s “pre-flight” checklist is more intense than the one they use in real flights! Strict discipline is the keyword here.

All my audio friends bitch about the DEQX hazards constantly…:banghead: unfortunately we cannot live without it – It is a necessary evil in our system…and we have to live with its most scary mode – Digital I/O mode. Having said this, with proper respect and proper safety measures, the DEQX benefits can be fully realized in a safe manner.

I agree with Mr. Widget comments regarding the relative DEQX’s sonic qualities of the A-to-D and D-to-A converters. In early implementations of DEQX in PDC2.6P, the D-to-A converters and output stage are certainly the weakest link of the setup. This concern, in the case of the K2 S5500 (which has quite a decent passive crossover unit), I would even argue that, the benefits gained from deploying a DEQX active crossover setup, may even be offset by the loss that is attributed to a drop in signal transparency imposed by the DEQX’s analogue output constrains. It is simply not a truly convincing case to go with DEQX and I can understand why many DEQX users have felt dissatisfaction this way and gave up eventually.

This issue got resolved when one of our new members ordered a DEQX unit with Digital output. Without surprise, DEQX soon received a group of new orders for Digital output upgrade :P

With regards to the A-to-D quality, in our experience, it would be boarder-line acceptable, if the system is tuned to have a frequency response within the normal 20kHz ceiling, with DEQX running in 48kHz. In fact, I have lived with this setup prior to the introduction of the UT045Be and the Goldmund Universal Preamp, while I was running a McIntosh C39 preamp. It was certainly “livable”. That is until we have experienced what the K2 + Digital DEQX (especially running in 96kHz) can actually achieve!...then suddenly it becomes not totally enjoyable, as we constantly know in our minds that this can certainly be further improved.

For setups that are aiming for a higher resolution and extended frequency response (eg. 45kHz), with DEQX running in 96kHz, in our listening test, we felt that using the DEQX A-to-D always introduces a layer of veil in the presentation, which offsets the benefits that can be expected from the deployment of super-tweeters. It is like seeing thru a window via a piece of glass that is not perfectly clean. This issue is certainly not too noticeable until we start A-B comparisons, on system with identical setup but different DEQX configuration. Then like most outstanding issues with audio, which have a known solution but are pending for resolution, it becomes annoying. We initially attributed the issue to cabling, impedance mismatch, the front-end transport/DAC or even the fact that the external A-to-D conversion + 24-bit/96kHz up-conversion might play a role in causing this difference. To rule out the transport as a factor, we ran the setup with the venerable Esoteric X01 & P03 Universal, which features one of the most formidable CD/DVD transport Neo-VDRS. There is no doubt that many factors may be in play here, with such extended frequency in the analogue domain... At this point, for the extended frequency evaluation, the target end-user group is less so for the Vinyl source but more so for SACD type input, because 20kHz is usually good enough for Vinyl. In reality, this may not be a serious concern, as it is uncertain if many of the DEQX users will be using the analogue input, unless they really do not have a choice, like in the case of Vinyl, which might not require the extended frequency response. Is there a large DEQX user-group who listens to SACD? We are not sure... Most of the DEQX end-users will tend to run using PCM digital input to DEQX. To minimise the number of unnecessary Analogue/Digital conversions, one will feed the DEQX digital input instead, given that all the DEQX computation must be performed in the digital domain (so the conversion to digital is unavoidable).

With regards to the DEQX volume controls, it is a pity that the fine quality of the Burr-Brown analogue volume controls cannot be put into practical use, due to the constraints imposed by the DEQX DAC and output stage. The Digital volume control is weak when compared to its analogue cousin. It simply loses too much resolution below anything but the maximum setting. It will serve as a good digital “Mute” switch if one has to temporarily lower the system volume to take a phone call or conduct a conversation…but for everyday listening, it is not a viable long-term solution. In our setup, for satisfactory performance, we max out the digital volume control so that it is constantly disengaged.

Mr. Widget has raised a very interesting challenge for most DEQX users: Getting a good calibration with large speakers in a simulated anechoic measurement. Booking a session in an anechoic chamber will be the ideal case, but few of us can have this realized. To get the next best compromise, in our early attempts, much success have been gained from outdoor measurements, with speaker setup to face skywards, hanging the measuring microphone using a tripod fitted with a boom (which can be commonly found in recording/lighting setup). Wind noise can be an issue though, depending the time of day… But as Mr. Widget mentioned, this is not entirely feasible with larger speaker setup, especially when many setup also caters for AV requirements, with the speaker tugged behind a giant SoundScreen. For these setup, we have found that it is possible to perform a satisfactory indoor measurement if we:

(a) place the measuring mic in close proximity to the speaker (eg. 1m);

(b) toe-in the speaker in a manner (during calibration) much more than usual listening to avoid the first reflection from the side wall; this works well even behind a sound-screen.

(c) turn up the amp gain and DEQX ‘master volume gain’ to attain a mic feedback sound pressure in the region of 116-118db (which is quite loud for the ears and would advise to leave the room during calibration) without clipping;

(d) perform the calibration in a quiet room or quiet time of day. This should attain a high confidence factor from DEQX in the 38-42db range.

(e) Calibrate both the tweeter and woofer amplifier gains to hit the same output, measured from the mic during DEQX calibration, using the same DEQX ‘master volume gain’ setting. This is an important setup, which many DEQX users have commonly skipped. Without this step, there may be a risk that the calibration process will result in a measurement that requires the DEQX to compute a correction filter that will max out the 20db headroom window. This will result in less than satisfactory calibration results.

(f) Choosing the appropriate point to window the impulse response. Hopefully with step (b) perform, with experience, this will provide useful measurement range for DEQX computation.

(g) Try to add sufficient partitioning windows during calibration process. Due to the complex DEQX GUI design, many DEQX users have just stuck with the default and achieved a less than satisfactory calibration result. The objective of this exercise is to make each window cover the min/max frequency response whilst minimizing the overall height of the window. It is much better to have more narrow windows than fewer tall windows to cover the frequency spectrum, for the DEQX to generate the correction filter.

(h) Based on the frequency response, define a sensible correction range. Asking DEQX to do the impossible may not be ideal. Sometimes less is more. The judgment made is performed in a case-by-case basis, depending on the drivers being measured.

The “Room Correction”, as Mr. Widget has mentioned, actually does not achieve very much more than a fancy auto-EQ. We would have hoped that this function can be more sophisticated. But as of currently implementation, it will still require a lot of user-intervention. The way we see this, the main benefits we can get out of this function is to address the room’s resonance mode to deal with any lower frequency anomalies resulting from the speaker placement in relation to the room’s dimension. In addition, we can add parametric EQ points to suit each listener’s taste. In our setup, we don’t benefit much from this feature…it is mainly used to control any possible bass boom, if it exists.

In our experience, we believe that the path with DEQX is certainly not a straight-forward or easy one and can almost be guaranteed to be one that is laden with obstacles, after obstacles. The key to success is Persistence!:barf:

[K2-enthusiast]

:bouncy:I am so glad that you are sharing your experience in K2 S5500 + DEQX. I have already got the DEQX HDP-3 with the Earthworks DM30. I just haven't got time to set them up yet. My system will be set up as follows and I welcome all your comments:

Accuphase DP85 SACD/CD player ; Wilson Benesch Circle+Linn Linto LP
First Sound Presence Deluxe MKII preamp
DEQX HDP-3
Master Sound Reference 845 power amp for low frequency
Master Sound Mono 845 power amps for high frequency, each channel uses two 845 tubes, parallel single ended, with about 40 to 50 wpc.
K2 S5500 + Pioneer PT-R100 super tweeter

I shall have more questions when I start setting the system up. My first question is, if running the entire setup in full digital mode at 24bit/96kHz is best, should I use the DEQX's preamp in place of the First Sound preamp?If I do so, I will be using the DEQX's digital volume control which is also not recommended. :confused:

Hello Peter,

It is great to be able the share the end-user experience of the K2+DEQX setup with others around the world. This is one great aspect about this forum.

On behalf of other K2 fans in Oz, we would look forward to hearing your feedback with your setup. Please keep us posted. Actually we have member located as far as Dubai in UAE. He has a S5500 Project K2 as well in his setup. I guess the S5500 still have its attraction over the single bass driver setup of the S9800/S9900...

Given that your Linn Linto LP outputs a line level signal, it is sufficient as an input to A-to-D conversion. Based on our experience, we have reservations on the A-to-D quality of the DEQX (see my earlier post to Mr. Widget’s feedback). However if you chose to experiment with using the build-in A-to-D of the DEQX, this still a viable setup.

However, you will now faced with making a decision to tap either the digital or analogue output from the DEQX unit.

The analogue output has a quality Burr-Brown volume control, but this is coupled to the less than ideal DAC and output stage. Suggest to audition this setup first before making a judgement. It may sound ok for you.

However in our setup, this interface is not ideal, as our system requires an extended frequency response with utmost transparency, which the DEQX failed to provide via its DAC and output stage.

The digital output can have two configurations: (1) with digital volume control engaged; (2) with digital volume control dis-engaged. It is easier to evaluate the performance difference in this regards, but will require you to have external DAC connected….and also a means to control the volume outside of DEQX. We encourage you do this evaluation and hear for yourself what impact the DEQX digital volume control has, especially on the ambience and soundstage of the material you listen to.

Our choice to settle with using the DEQX as a full digital 24bit/96kHz active crossover setup (ie. as a pure digital D-to-D converter/processor) is pretty much arrived via a series of elimination processes. It is the only choice we were left with, if we were to fully exploit the full benefits of DEQX, without all the dreaded shortcomings from its implementation.

One aspect a full-digital active crossover setup will encounter, is the issue in relation to volume control, whilst aiming to achieve maximum S/N ratio.

The concept will be no different to any audio setup involving multiple components, with one or more source input feeding line-level signals to amplifier. It would be preferable to have a relatively hot-signal as input to maximize S/N ratio and only apply volume control to trim it, prior to amplification.

However, in the case with our full-digital active crossover setup, the boundaries require to be redefined. The analogue output stage does not really start until the output stage of the external DAC. Your normal source from LP and CD, via the DEQX and the external DAC can logically be grouped in one, to become your traditional line-level source in analogue audio setup.

As you can see, if we were to apply the principle to maximize the S/N ratio between external DAC and the multiple amplifiers, we are faced with a number of challenges:

(1) Ideally, we want to run as “hot” as possible a signal from external DAC to multiple amplifiers; with or without a digital volume control prior to DAC, the DAC will be running in full output.

(2) You can setup individual gain controls on each amp to match their sensitivity in relation to the drivers connected, but they are not designed for the master volume control we are seeking.

(3) In our normal setup, we do not have an easy means to control all the analogue output from the DACs in a ganged-fashion. The Apogee DA16x can actually achieve this goal via the use of its convoluted menu. but certainly not in an easy manner... The ideal case would be to insert a quality passive preamp that supports multiple channels, which are all ganged together, between the external DAC and multiple amp. This will be the ideal setup. Unfortunately, this is not a common product available in the market. We are actually building a custom design ourselves to address this need., with individual trims for each channels.

(4) At low volume, you may notice a background hiss of the noise floor depending on how optimal the various gain controls in your setup. It is possible, with optimized tuning, to drive this down to a very low level. This subdue hiss is certainly not noticeable at your typical listening position, but if you stand real close to the K2 and place your ears next to the horn/compression driver, you may be able to detect it. It is a result from the combination of high efficiency of the horn+compression driver in conjunction with the maxed out volume setting at the DAC output stage (with no preamp to trim the output level of signal/background-noise in between), when no input signal is fed; Having said that, this is a small price to pay as you enjoy all the benefits of a full-digital active crossover setup and is certainly a highly configurable component, which will require you to experiment and decide on how “hot” a signal you’d like to run between DAC and your amps, in relation to the “typical” listening volume you enjoy your music. To keep in mind that with a full-digital active crossover setup, without a passive preamp inserted between DAC and amps, you are essentially listening at full-volume setting in an analogue setup. If you turn your volume on your preamp in an analogue setup all the way to 100%, you will realize the background noise-floor referred to above. In any case. this is not normally noticeable if a signal is fed, because with signal, high signal-to-noise ratio can be realized when there is a contrast; however without signal, you will be comparing the ambient background noise in your listening environment against the background noise from your audio setup (turned up to full amplification). And because these two have amplitudes that are comparable in their order-of-magnitude, it can be noticeable as your hearing adjusts. This is the relative nature of S/N ratio. An analogy would be walking in into a noisy environment, at first it will sound noisy to your ears and will bother you, but after a while, your hearing sensitivity adjusts and it becomes less noticeable.

Of course, with the ideal setup as mentioned above, a quality passive multi-ch preamp will be inserted between external DAC and those of multiple-amps. But this preamp will have to meet the special requirements as mentioned above…not exactly easy to find.

One suggestion to DEQX, as an enhancement, is to provide a set of 6-ch XLR inputs, which when used in conjunction with their AES/EBU digital output to an external DAC, allows a loop back to DEQX to utilize the internal "ganged" Burr-Brown volume control in its analogue output. And provide an option to set the analogue output stage as a passive pass-thru...in essence, implementing the conceptual multi-ch passive preamp above, but in a neater package inside the DEQX chassis. DEQX seems to be trying too hard to implement features that may not be fully utilized by their high-end users, whilst driving the unit price up...perhaps something for Kim to consider?

As an interim measure, a good compromise can be made to use a quality digital volume control, prior to the signal feed to the DEQX digital input. The choices are increasingly more available, as quality digital preamp becomes popular.

FYI, we run the Apogee DA16x not only for its quality DAC, but also for its ability to lower the jitter via its C777 circuitry, it also has an output stage with audio-transformer like properties to match impedance, with a highly configurable gain to output very ‘hot’ signal, if and when required. This in essence, has partially addressed some of the challenges we have listed above. Having said that, the user-interface of the DA16x may not be the easiest to work with... :P

Unfortunately, when it comes to full-digital active crossover setup with DEQX, the answer to your first question is not a straight-forward one. But hopefully, with the above, we have shared with your our experience to provide you with the info you need to progress with your setup. :bouncy:

[K2-enthusiast]

I've just bought a pair of K2 S 5500, I plan to actively bi-amp them with two TACT 2150 , I have a question about slopes , the manual speaks of "third order crossover at 800 Hz" , is this value correct ?
Thanks .

We would suggest going with the factory recommended 800Hz for a start.

Suggest to experiment with steeper crossover slope than the factory 3rd-oder / -18db/oct. With passive crossover, it becomes increasingly difficult to build ones beyond 4th-order. However, since you are running in active crossover, this limitation does not necessarily apply.

For steeper crossover slope, we have achieved good success with 750Hz as well.

Of course, with JBL specifying -18db/oct, the drivers alignment is designed for this purpose. If you use other slopes, you will need to cater for the phase lag compensation between the drivers, via the calibration process.

Happy listening with the K2s :applaud:

[pos]

By looking at the voltage curves posted on these forums, it looks like the electrical HP for the S9800 is a 6dB/oct filter!
The S9900 looks much steeper.

[hjames]

I have an excellent nearly pristine pair of jbl k2 s5500 speakers that i bought in asia and now wish to sell. They are my pride and joy but my current circumstances require me to part with them. Serious enquiries only please.
My name is Richard and I can be contacted at [email protected]. Thank you.

Posted your ad into every existing K2 thread here, didja?

I think you would do better to start your own thread, and - hey, posting pictures is always a welcome thing when selling up-market gear.

[PP_65]

Finally some news : when I've made my first bi-amp configuration ( 800 Hz , 3rd order slope) , it was not very good , the speakers linearity was gone ; fortunately someone posted here, in another thread, the curves of the active X-over cards that JBL had made for the 5500 (http://audioheritage.csdco.com/vbulletin/showthread.php?1908-DX-1-XPL-200-x-over-cards-on-the-way&highlight=DX-1) , then I have set the Tact to copy these curves and now I'm really pleased with the sound . Maybe I can do better, but I need some more time .

[PP_65]

Finally some news : when I've made my first bi-amp configuration ( 800 Hz , 3rd order slope) , it was not very good , the speakers linearity was gone ; fortunately someone posted here, in another thread, the curves of the active X-over cards that JBL had made for the 5500 (http://audioheritage.csdco.com/vbulletin/showthread.php?1908-DX-1-XPL-200-x-over-cards-on-the-way&highlight=DX-1) , then I have set the Tact to copy these curves and now I'm really pleased with the sound . Maybe I can do better, but I need some more time .