Crossover jbl k2 suggedtions

I fancy trying my conrad johnson se 350 on bass duties alongside the cymer monos I bought from Dave a while back, I think the monos are better at some things but prefer the cj at others so thinking why not try both

I guess I need a digital crossover, the speakers provide for splitting bass and treble so what should I look for and how to wire it up is the advice I am looking for

Even better if someone has the kit and fancies a loan or pop over to staffs for a bit of experimentation


I use a little minidsp 2x4HD for the same job. Easy to use and works well (and the software allows frequency band tweaking if you want). Previously I made up and used a Linkwitz-Riley analogue active filter kit from KMtech but the minidsp is much more versatile.
There are better things around, but this is straightforward and works well enough.
Might be able to pop over from Sheffield - where in Staffs are you?

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I have a mini DSP you could borrow.


Thanks for the replies

I am in leek so about an hour from Sheffield, assistance with the tech would be wonderful if you are up for a trip over the hills at some point

Loan would be great too but suspect I would be better with some help as not great at anything high tech, if it’s plug and play then different story of course


This suggests the passive crossover has seperate inputs for bass and treble, so you dont need a digital anything, just a way to set the gain the same on both sets of power amps. Do either or both have built in volume controls?

Hey Simon, will read it again but pretty sure the manual said I need a crossover, bit more research required. Neither amp has gain tweak function that I am aware of

Are they the K2 S9900?

Bi-Amp Switch
The bi-amp switch is located under the battery access cover and allows the
system to be set up for the use of an external low-level crossover. This switch
removes the passive components in the low- and high-frequency networks that
have to do with the actual crossover blending of the low-frequency and highfrequency transducers. Level attenuation and equalization circuits remain active.
In the case of the K2 S9900, the voltage drive required from an external
crossover network is very unusual and, in most cases, is not likely to be achievable with standard crossover networks. It is for this reason that active bi-amplification of the K2 S9900 is not advised

Nope 9800 k2

Manual says they sell something called a dx1 to do the job

For bi-wiring or bi-amplification appli-

cations, four identical amplifiers or two

dual-channel units may be used,

although specialized low frequency and

high frequency amplifiers offer clear

advantages. (If four amplifier channels

are used, the high frequency amplifier

may be up to 6 dB less powerful than

the low frequency amplifier. Due to the

12/4/01 12:10 PM

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Project K2 S9800

power versus frequency distribution of

the music, the low frequency section

requires approximately four times the

power of the high frequency section.)

P roject K2 S9800 specialist dealers can

recommend amplification to best suit

individual needs. In all cases, the left

and right amplifiers for each section

must be identical. Make sure that the

input sensitivity of the two amplifiers is

equal or that input level controls are

provided to maintain the proper low to

mid/high balance. If two identical

stereo amplifiers are chosen, each

amplifier may be located near a loud-

speaker and drive low frequency and

high frequency sections through short

wire runs.

The addition of a crossover network

such as the JBLDX1 Electronic

Crossover will allow the direct connec-

tion of the low and high frequency

components of the P roject K2 s y s t e m

to frequency dedicated amplifiers, and

is required if the system is to be bi-

amplified. The DX1 crossover is

specifically matched to the response

characteristics of P roject K2 S9800

and will ensure optimum performance.

The DX1 may be purchased from

P roject K2 S9800 specialist dealers

Happy to pop over to Leek, will PM to arrange date

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From the manual online it looks like you have a few options:

  1. Single wire or bi-wire
  • use a single stereo or pair of monoblock amps
  • use built in passive crossovers
  • single wire - and bridge at the speaker
  • bi-wire from the amps to the two pairs of terminals on the speakers
  1. Bi-amp - passive
  • use 2 stereo amps, or 2 pairs of monoblocks
  • use built in passive crossovers
  • use one amp (or pair of monos) for bass
  • use on amp (or pair of monos) for mid/treble
  • you need to use identical amps, or have a way of ensuring the gain of all amps is the same
  1. Bi-amp - fully active
  • use 2 stereo amps, or 2 pairs of monoblocks
  • DO NOT use built in passive crossovers - i.e. remove back panel plate and flick switch to Bi-Amp mode
  • buy JBLDX1 Electronic Crossover (finding one of these looks like a challenge) (this is the bit a mini-dsp could replace, but you would have to replicate the crossover design)
  • place electronic crossover between preamp and 2 stereo amps, or 2 pairs of monoblocks
  • wire power amps speaker terminals - which are now directly connected to drive units, and passive crossover bypassed



I think the likelyhood of finding a DX1 are extremely rare.

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I would go for option 2 and use the in built passive crossover tbh

it would probably just need a passive volume control between the preamp and the more sensitive of the sets of power amps

The DX1 story gets even more tricky.

It seems the DX1 was used for a range of different JBL speakers, and inside there are module cards for bass and mid/treble which were different for each specific speaker.

Some photos show them here:

The schematics online therefor show various resistor and capacitor values marked as TBD on each of the two module cards

yes that does look tricky - perhaps start with biamp and work up to full active - my manual says something about 6db bneing the max difference in power amp output - is that going to be a problem as the gain is very different between the two (based on where the volume starts and gets too loud with the cymer (very useable) v the Cj (small amount of travel before too loud)

Gain and power output are not related

If the CJ has a much smaller travel on the volume control than the Cymer, for the same sound level, it sounds like you need a passive volume control between the preamp and the CJ, then just turn up the volume on the CJ until you get the correct level of bass…(assuming you have the CJ on the bass)

if you dont have a passive pre, the CJ will make the bass super loud

something like this should be enough to get you going if you dont already have one:

The circuit for the dx1 does not look too tricky to replicate.

You could probably get someone to work out what the crossover is doing to the signal, and replicate that with an active or digital crossover. It may be possible to work it out from clear photos of the actual crossovers and drive unit labels.

Indeed it may have already been done - that JBL forum may well be the place.

Crossover Frequency: 800, 10000Hz

You’re probably looking at the 800Hz crossover. I imagine it will be second order, so dead easy to do using a digital thingy that Dave can take. Just remember to reverse the positive and negative on the bass (probably, but not definitely).

You might get even better results from replacing the 10k crossover as well, while you’re doing it, but this will be more complicated for the wiring. I would stick with the inbuilt passive for now.