Problems bi-amping 4430’s with 5235 Xover

[Tony]

I wonder if anyone can help with problems I am experiencing trying to bi-amp my 4430’s.

Until now I have been running my 4430’s passive through 2 x Naim 160 stereo amps using one channel for each speaker with very satisfactory results. Recently I have introduced the 5235 crossover with the special 4430/4435 network cards installed using the same two Naim 160 amps one for LF and one for HF and am now having problems.

My first impressions on bi-amping with the 5235 were positive finding the sound to be clearer with more definition and a wider soundstage . However, over the next few days I became aware of bias towards the left speaker – which, of course, I can bring back into balance with the pre-amp balance control. Trouble is the degree of slew seems inconsistent insofar that listening becomes ‘uncomfortable’ with the sense that the balance control must be re-adjusted sometimes even within the same track . The was not necessary beforehand when running passive as described earlier, where the sound was very solidly centred - as it is now again as I have returned the system to run on the internal crossover.

It would seem that 5235 crossover and/or network cards are losing strength of signal somewhere. Or, I suppose it could be with those parts of the internal crossover which remain active when switching the 4430’s over to external crossover.

I am not very technical in these matters and undoubtedly will need to consult a specialist, but I wonder if anyone has had similar experiences or can otherwise suggest a probable cause and resolution?

[mvaldes]

Hi Tony,
I haven’t had any similar problem when biampling my 4430 with the 5235. I must also say that I used it for very short time because I don’t like how the 5235 “sound”, but this is just my opinion.
I suggest you to check the rotary bi-amp switch on the 4430 back. It is a very cheap switch that more than often do not provide a good contact, especially if it haven’t been used for long. (try to move it L and R for few times with the amps powered off)
Try also to check all the connection on the 5235, amps and speakers. It sound like you have a phase problem.

Hope this help

Michele

[doodlebug]

Seems like there have been some other posts regarding issues with that internal/external switch on the 4430s. Might want to do a search here. I believe cleaning was the order of the day.

I'd like to think that would be a really cool setup.

Cheers,

David

[JBL 4645]

Hi Tony,
I haven’t had any similar problem when biampling my 4430 with the 5235. I must also say that I used it for very short time because I don’t like how the 5235 “sound”, but this is just my opinion.
I suggest you to check the rotary bi-amp switch on the 4430 back. It is a very cheap switch that more than often do not provide a good contact, especially if it haven’t been used for long. (try to move it L and R for few times with the amps powered off)
Try also to check all the connection on the 5235, amps and speakers. It sound like you have a phase problem.

Hope this help

Michele

Yeah seems like its got dirt clogging it up. A little spray of (compressed air) might clear it, thou it only means the dirt will be moved to different part of the (variable resistor).

The idea with active crossover is lower lows and higher highs with less distortion.

Wow that a nice JBL speaker!




Tony

Try this out get a sound pressure level metre and use (wideband pink noise) turn off or mute the LF and play the pink noise on each speaker at a single time left and then right! Note the level of each and if one is different adjust the level until each on has the same level on the SPL db metre.

Then mute the HF and test the LF for equal level and get them matched up to the same SPL db level and then play them back with LF and HF all turned on! Listen to some music or film soundtrack and see if that makes a difference.

Note: the hiss or whoosh sound on the HF should have the same tone place them as close together to see if they have the same tone it shouldn’t be like this. (Left hiss and right HISS wrong) if that helps? They should each have the same loudness (left HISS right HISS correct).

If they are spaced apart bare in mind the walls might be closer to one of the HF and if you make hiss sound with your mouth and place your hand in front and move it back and forth it will go whooshy!

I use Behringer DCX2496 on my JBL control 5 LCR and each is tested with HF and then LF to get the same level over the fronts I use a little delay on the centre channel this helps with half panned sounds on the left and right that partly mix into the centre, giving a wider sound image at the front.

Might be you rushed it with the JBL 5235 and don’t own an SPL db metre also an RTA will help to see the frequency response of each speaker in-turn, you might have dodgy HF or maybe a lose wire?

[jblbgw_man]

Hey Tony,

Because I prefer the 4435 active mode over the passive mode I removed the changeover switch and hard wired it into the active mode ..... these switches really are suss and I believe this is most likley to be your problem.

As sugested elsewhere here check all your input connections to the 5235 for phase consistancy between L & R and speaker phase connections both from the amps and on the speakers.

After pulling my hair out for ages to get the LF & HF balance right I now set mine up using a 8 ohm dummy load on the output of each amp and a HP AC RMS Volt meter across that, setting up the amp gains and 5235 drives using a 80Hz tone for the LF and a 10kHz tone for the HF and matching the output RMS Volts across the dummy load........... works fine for me

[grumpy]

... another vote for the input switch, but don't discount the possibility that you might need
to set the 5235 gain settings somewhat differently for the L and R channels..

Matching L/R HF outputs to less than 1dB requires measurement tools (as others have also
already suggested), and the adjustment was fairly sensitive (a small increment of
rotation produced a large change in gain... at least when looking for sub-dB changes).

[boputnam]

Tony...

You've gotten a variety of opinions and advice - but one comment you made has me fishing:

...Trouble is the degree of slew seems inconsistent insofar that listening becomes ‘uncomfortable’ with the sense that the balance control must be re-adjusted sometimes even within the same track .

Uh, that is not good. I'm suspicious that good ol' 5235 is giving up the ghost, so to speak.

Who made the cards?
Where did you buy this from?

I'd suggest you get your hands on another active, adjustable, crossover. Set it's parameters to match the 5235 cards, and see if the symptoms persist. My grab is, the 5235 is past it's "use by date".

[grumpy]

yeah... that comment was weird, but sometimes balance issues are just more noticeable
with certain material. One assumption I was making is that this balance issue wasn't a
problem before (e.g., not just an L-pad wiper problem... which I've had).

Were leads to the speakers swapped L<->R to see if the balance shifted the other way?
(isolate speaker problem from potential crossover/amp issue)

If levels are set, test material is mono, and the problem persists, then there's something to chase.

[boputnam]

Hi, Dave...

Agreed. I'm relying upon his (near) closing comment: "The was not necessary beforehand when running passive as described earlier, where the sound was very solidly centred - as it is now again as I have returned the system to run on the internal crossover."

As usual, us JBL CSI'ers are held hostage to the limited available evidence offered...

[Robh3606]

It it's limited to the HF of one side try running the potentiometer over it's full range a half dozen times. Could just be an oxidized pot. If you hear noise while you are adjusting the level good chance that could be it. Power it down when you run the pots through their ranges just to play it safe. When you bring it back up have the amps turned down too just in case.

Rob

[Tony]

Hi and thank you everyone.

I do not have any equipment to take measurements - only my ears. I shall work through the suggestions beginning first with swopping speakers leads to see if I can isolate the problem to the crossover/network cards or the speakers. I hope I can establish this without having to shift the speakers around! I do not think the poweramps are the problem - the system is now set back to passive on internal crossover and is 'singing' with the soundstage solidly centred. In fact the sound is impressive (especially the the Boss's half-speed mastered Born to Run that I was playing last night) and I have no reason to think that any of the drivers are dicky.
I have two 5235 crossovers (but only one set of network cards) so I can possibly eliminate narrow-down another question. Phasing might be an issue as I had trouble having the interconnects made-up correctly - so there might be an issue here. What bugs me is that on first connecting up using the external crossover etc, I was not immediately aware of the imbalance and was initially impressed with what I thought was a step forward - but perhaps I heard what I wanted to hear; there is, I find, plenty in this Hi-Fi pursuit that can lead you at times to question your own sanity, that is in the sense of - I thought I was decisive etc .

I will report back!

[JBL 4645]

Tony

Even if you were to do this rather incredible simple task!

Use wideband pink noise again!

Take the outputs of the LF and HF and pass them into a graphic equalizer that has spectrum analysis display and take a look at the HF side it should be equal form side to side!

Also the two signals of left and right HF should double up on the display if they don’t when adding one of the HF channels to the other if it is the same level then one side is out-of-phase with the other.

User’s manual for JBL 5235
http://www.jblproservice.com/pdf/Vintage%20JBL-UREI%20Electronics/JBL-5235%20manual.pdf

[Tony]

It would seem that I have found the problem -the internal / external crossover switch on the RH speaker. While I had done this previously I vigorously worked the switch backward and forth, reconnected and low and behold success, the soundstage is back where it should be. Thanks jblbgw man!

While I have followed the threads for 4430's where it seems the 'jury is still out' as to whether the internal crossover or bi-amping with the external crossover is preferred, I hae to say that to my ears it is a definite positive for bi-amping and external crossover (5235 with 4430/4435 networks cards). IMHO the sound is clearer with more definition and a wider and slightly taller soundstage. At this point I am well pleased although shall be looking to have the crossover swithch properly cleaned and/or bypassed as well as hopefully borrowing some measurement equipment.
Thank you to everyone for the help given.

[mvaldes]

It would seem that I have found the problem -the internal / external crossover switch on the RH speaker.

this is what I've suggested since my first replay....

By the way, if you have the possibility, try a different crossover than the 5235. The 5235 is not an Hi-fi product.
If you like the 4430s when biampling, you will love them with a better crossover.

Michele

[jblbgw_man]

By the way, if you have the possibility, try a different crossover than the 5235. The 5235 is not an Hi-fi product.
If you like the 4430s when biampling, you will love them with a better crossover.

Michele

"What is a HI FI product" ?.... I have posted a simple upgrade of the 5235's in previous posts using Burr Brown chips and using high grade electrolytic caps in place of the originals. Look at my post here #8 http://www.audioheritage.org/vbullet...own#post223820 AND this one with pics http://www.audioheritage.org/vbullet...highlight=5235 This explains why you should try and retain the 5235 with the 4430/4435 cards. When looking at the graph of the voltage drives of the 4430/4435 cards you will notice the LF shelving applied ......... this is not insignificant, it is a 5dB reduction at 800Hz! If you can achieve that and the same phase response with something more bling bling then good luck! If the 4430/4435 cards produced standard 12, 18 or 24 dB filter slopes then no problems use anything that is "better" but I would be suprised if there was anything stock on the market that could duplicate the same slopes and phase response AND sounded "better" weather it be digital or analog. Don't forget the main problem with mixing consumer electronics with professional products is the huge nominal operating level difference of -10dBu for consumer and +4dBu for professional products, a whopping nominal 14dB difference! This in my view is why some people don't get the results from professional products that they think they are going to get.