JBL 4365 Active Crossover settings

[bubbleboy76]

I have done a very basic setup with bi-amp and active crossover on my 4365s. In my ears the sound-improvement is big in my system compared to stock crossover and single-amp. The sound is subjectively more clear and dynamic, and much more bass the way I like it.
It is very fun to test different settings, and hear and measure what happens. This is to me the best way to learn.

Equipment:
JBL 4365 with temporarily bypassed internal crossover.
DBX Driverack 260, internal output gain jumper lowered to its lowest setting.
Oppo BDP-105, xlr output 4.2 vrms at full volume. I use this as preamp with the digital volume control in the ESS Sabre dac.
DBX RTA-M microphone.
Focusrite Scarlett 2i2 sound-interface.
REW analysis program, with DBX RTA-M generic calibration file
Hypex nCore nc400 6-channels (DIY). 3 channels with about 12Db lower input sensitivity/gain by removing resistor r141. 26 Db, respectively about 13 Db, gain. I use the high-gain channels to drive the LF, and the low-gain to drive the HF.

I know there are a LOT to work on and improve, but my initial settings sounds surprisingly good!

Measurements done only in one position, the listening position. I plan to sum more positions later on.

2-way at the moment. Hence, the UHF is not in use. I keep it simple for now.

Work on delay in the crossover-region is my next planned step, and off course more work on the crossover region overall. I plan to do it with close microphone, and as far away from the walls as possible. The speakers are huge, so I can not do it outdoors.

48Db slope in the crossover sounds slightly better than 24Db at the moment. I think it is best to keep the crossover narrow until it is finetuned/more correct.

The system is dead silent at idle, even when putting the ear to the horn. I am quite impressed by this. No noise at all.

Comments and tips are welcome, I am a beginner at this. But try to keep it positive, I do this for the fun of it!

Settings, measurements and voltage drive of the original network will follow.

Other owners of 4365, please post your settings if you go this route! I know goophy did active crossover as well.

[bubbleboy76]

My current DBX 260 settings, that roughly gives a JBL/Harman house-curve in my listening-postion.

INPUT:
-6Db

(I want to use as much voltage out from my consumer-level source as possible)

PRE-PEQ:
FC: 78.8Hz
Q: 12.364
Level: -6Db

(My room standing-wave roof/floor reduced)

CROSSOVER HF:
High-pass: 793,7Hz
High-slope: LR 48Db/oct
Low-pass: 20.159Khz
Low-slope: BW 24Db/oct
Gain: +3.2Db

CROSSOVER LF:
High-pass: 20.3Hz
High-slope: BW 24Db/oct
Low-pass: 793,7Hz
Low-slope: LR 48Db/oct

(
790Hz inspired by the M2 filter. Initially, I used 750Hz like the original network. 790Hz feels safer to not stress the 476mg.
LF high-pass to protect the 1501fe, I do not know if it is needed? It sounds better without this filter, more "body" in the bass.
HF low-pass to not make the 476mg go out-of-bounds. I do not know if it is needed? I hear no difference, so it do no harm in that way.)
)

POST-PEQ:
FC: 1.46KHz
Q: 14.065
Level: -6Db

High-shelf FC: 4.76KHz
High-shelf slope: 12Db/oct
High-shelf level: +6Db

Low-shelf FC: 136Hz
Low-shelf slope: 6Db/oct
Low-shelf level: +9Db

(Low-shelf inspired by the M2 filter and the JBL/Harman target curve)

[bubbleboy76]

The JBL/Harman target curve I am referring to attached.

[bubbleboy76]

Voltage drive and frequency response for the JBL 4365. Source: Italian magazine Audio Review.

[bubbleboy76]

Ok, a dummy question!
Why are crossovers done in this overlapping and summing way? Why not cut straight off? Digital dsp must be able to do it?

[bubbleboy76]

Can someone give me advice what protective caps to use on the horns?
The 476mg is 8ohm, and I use 800Hz crossover frequency.

[fpitas]

Ok, a dummy question!
Why are crossovers done in this overlapping and summing way? Why not cut straight off? Digital dsp must be able to do it?

It's not possible to cut straight off, but the slope can be quite steep with DSP. Steep slopes have mathematical consequences, though. For a "conventional" filter topology, a steep slope will introduce a large peak in the group delay and ringing in the time response. DSP can achieve another result using an FIR filter, but the price is pre-ringing.

[ivica]

Ok, a dummy question!
Why are crossovers done in this overlapping and summing way? Why not cut straight off? Digital dsp must be able to do it?

Hi bubbleboy76,

Today DSP driven networks can provide sharp (usually called "brick wall") filters using different type of filters while the price can be "acceptable" (see 'miniDSP' OpenDRC products), but using such type of filter, as drivers are separated each to other (due to its size, or horn size) the listener can get a feeling (in the smaller rooms especially) that a part of the listened music from the instruments is coming from one driver and the other part from the other driver as the reproduced frequency spectrum is divided sharply between the drivers, so a kind of overlapping would give much more smoother passage from one driver to the other.
Drivers directivity is different too.
On the other side we have to be aware, that whenever the same part of spectrum is reproduced by two (ore more) sources, that are some distance apart, a kind of "comb filter effect" would be present when off-axis listening is done (fortunately, the reflection waves have 'soften' that effect).

I believe that 68uF to 100uF capacitor would be good protection of the compression driver with less influence on the sound over 700-800Hz.

Regards
Ivica

[fpitas]

ivica raises a good point about spectral overlap. Some overlap is usually necessary to get good driver integration. I suppose if you sat hundreds of feet from the speakers overlap would not be necessary, but in a typical listening situation, it is.

[bubbleboy76]

I believe that 68uF to 100uF capacitor would be good protection of the compression driver with less influence on the sound over 700-800Hz.

Regards
Ivica

Thanx.

I found some old JBL-guidlines stating 52uF is recommended for 8ohm and 750Hz crossover. Minimum 250v.

Any recommendations of brand/type?

[bubbleboy76]

My next planned thing to play with is time-alignement (with delay of the LF) by measuring max cancellation at the crossover point with the drivers out of phase.

Should I do the measurement in the listening position(s) or close to speaker placed in the middle of the room? Any thought about this would be welcome.

[1audiohack]

Confound you Bubbleboy!!!

I am trying to ignore this thread since I am perfectly happy with my 4365's, however I do have a couple of 260's that are not in use, and there's that pile of amps just waiting,,,

Grrrrr!

[bubbleboy76]

Confound you Bubbleboy!!!

I am trying to ignore this thread since I am perfectly happy with my 4365's, however I do have a couple of 260's that are not in use, and there's that pile of amps just waiting,,,

Grrrrr!

It is your destiny. Join me, and together we can rule the galaxy as father and son!



Edit clarification: You will be the father in that case! I have read a lot of your posts on this forum, and I have great respect for you.

[bubbleboy76]

Take this with a grain of salt, because I am a bit excited just now...

I tried some different delay-settings without measuring, just listening.

OH MY GOOOD! The sound went to the next level.

Done some other changes as well. Just listening, not measuring. I am on the verge to too much bass now, but I am a bass junkie.

My current DBX 260 settings:

INPUT:
-4Db left
-5Db right

PRE-PEQ:
FC: 78.8Hz
Q: 12.364
Level: -6Db

CROSSOVER HF:
High-pass: 771.1Hz
High-slope: LR 24Db/oct
Low-pass: 20.159Khz
Low-slope: BW 24Db/oct
Gain: +3.2Db

CROSSOVER LF:
High-pass: 19.7Hz
High-slope: BW 12Db/oct
Low-pass: 771.1Hz
Low-slope: LR 24Db/oct
Delay: 0.10m

POST-PEQ:
FC: 1.46KHz
Q: 14.065
Level: -6Db

High-shelf FC: 4.76KHz
High-shelf slope: 12Db/oct
High-shelf level: +6Db

Low-shelf FC: 136Hz
Low-shelf slope: 4.5Db/oct
Low-shelf level: +9.5

[bubbleboy76]

One reflection, my measurement system and my driverack is not in sync. For example, if I put a notch-filter at 80Hz in the driverack, then it takes effect at 70Hz in the measurements.
This makes it a bit tedious. I can not just measure and then know which frequency to attack in the dsp. I have to trial and error, until the measurement-curve looks like I want.
I am trusting the driverack more than the measurement-system, so probably something is wrong in the setup.