Noisy Tweeter after JBL amp replacement

I have a 2nd gen with the JBL audio. I'm building a custom head unit, and evidently the JBL head unit uses some digital signaling paired with magic in the JBL amplifier to work, so I figured I'd just toss the system and throw in my own. So I did. I have a line output now going from the head unit into a balun over ethernet cables to where the amp is located (I am paranoid about electrical noise over that wire distance).

I put in

$84 Blaupunkt 1500W 4-Channel, Full-Range Amplifier

this Blaupunkt 1500W amplifier (I thought it would be smaller...) and wired the speakers to it. I put the front and tweeter speakers on the same terminals because I thought that should work. Anyway, when I power the thing on, the right tweeter crackles occasionally. This happens without any sound going through. There is also occasional crackling on the main speakers (but it doesn't really happen when sound is playing, just when idle and particularly when turning on or off).

I suspect maybe the tweeter itself is bad now, since the same thing doesn't happen on the left tweeter? I read that the JBL amp has a built-in crossover, and maybe I needed to put one in. So I picked up some of

$29 300 Watts 2 Way Crossover - (2 Pack) Passive Car Audio Speaker Tweeter Mids and Highs CRX-203

these, and it didn't make a difference (except the tweeter output is very quiet).

Anyway, is there something I'm missing here, or am I looking at needing to replace the speakers at this point? Is there a better setup I could be using?

 

for starters, you'll definitely need the crossover units you got to feed the correct signals to the correct types of speakers.

and you said custom head unit? what are the specifications of it's output, both hardware, and software? (i've had issues in a previous audio-focused carpc build related to audio drivers causing similar problems)

i don't really believe baluns work in within a vehicle setting, as the EMI from other wires tends to be far too close to allow the cancellation to occur-- an important definition here that balanced systems seek to achieve, is to subject both wires to any EMI to effectively cancel out the effects of that injection. this can be effective with some distance from AC signaling wires, and is further mitigated by utilizing data streams with parity packets.

but as in the name, balanced/unbalanced converters don't have the data streams, or utilize any other form of parity packet, and rely entirely on the natural cancellation effect of equally subjecting both the 'supply' and 'return' paths to the noise, in some ways raising the noise floor. vehicles tend to be different running off DC, which offers a slightly more non-varying concentrated EMI field, as well as wires being bundled more tightly to be confined within the body panels. some times, the dc can 'charge' wires creating more discharges than the same principles dealing with varying signals in a data or AC noise.

i've found it to be far more effective to seek to instead block EMI injection via thorough grounding/shielding means instead, by using cables more like instrument or coaxial tv cabling, in other words, ruggedized cables that have a full-coverage outer negative ground plane shield, with a single inner conductor used for the positive signal path. a good grounding path would both shield the signal wire, as well as offer an immediate grounding path for the EMI--one of the benefits of RCA cables outer ring to be directly connected to ground in the majority of equipment.

that said, as someone that's spent far too much on too many brands and types of interconnect cables than i should admit, the signal path is going to be the least-likely culprit, the baluns were really just a waste of time/money--the Street Wires Zero Noise RCA interconnect series was entirely dedicated to using twisted-pairs for signal transfer based on the math behind balun behavior.

but also important to note-- due to the vibration element of vehicles, stranded cable is a requirement. solid-core wiring will break down over time and develop further issues.

that leaves two likely culprits in this case. either your power and/or ground aren't sized appropriately, and/or connected well enough, effectively 'choking' the amps power supply, causing the internal capacitors to unreliably charge/discharge. or the amp itself, being a class a/b design is causing some of the issues-- either because of a different internal problem, or because of some nearby interference it's picking up.

moving forward, the first easiest thing to do would be to either un-bundle balun interconnect to get it as far away from other wires as possible, or run a new loose interconnect wire across the truck cab. if that were to repair the noise, it would be a noise injection issue, and your interconnect wire needs to be ran differently to correct it, or replaced with a different type of cable better suited for the noise rejection desired.

next would be verifying the amp wiring sizing, and accounting for using pure copper, or cca wire--cca needs to be uprated one size for the additional resistance of the aluminum core. as well as checking all the connections in the system for proper wire insertion to the connectors, and tightness of the fastening screws. sometimes even a bad fuse can cause issues, though it's very rare. also verify your ground point is to a solid point on the truck body, preferably on or near a factory ground point, and with the paint sanded off so the ground is connecting to clean metal.

after all that, the next step would be to try a different amp to eliminate an internal problem within the amp.

 

Thanks for confirming about the crossovers. Any reason why the tweeter output would be quiet? The product says the range should be 3.39khz+, maybe I'm just getting old

The custom head unit is basically a raspberry pi with an audio out to

$57 MB Quart MBEQ7B 7-Band 9 Volts 1/2 DIN Pre-Amp Car Audio Graphic Equalizer with Front 3.5mm Auxiliary Input, Rear RCA Auxiliary Input and High Level Speaker Inputs,Silver

this equalizer. It has both a 3.5mm and RCA inputs. Regardless, I am testing by using my phone into the aux input, because as you mentioned about software and haredware driver issues, I wanted to eliminate that as a possibility.

I think you're right about the baluns, I've also read elsewhere that there's a minimum length for them to be effective as well, but your point about the types of EMI sound spot on. The other appeal of using ethernet was that I only had to run 3 relatively small cables rather than 6. I'll try just using better cables - though the ZeroConnect cables you mentioned don't seem to be in stock anywhere.

My ground connection reads < 1 ohm, so I'm not sure that is it. (I have a 8 awg wire nearby that runs straight to the battery, and it reads about the same). The point about incoming power is interesting; I re-used the power line from the old amp which sits on a 30A fuse so I assumed it would be enough. All the amp wiring is done with 14ga stranded copper, except where I've wired them into audio harnesses (where the wiring is whatever comes on the harness, which is probably cheap garbage to begin with...)

Anyhow, sounds like I still have a couple of things to try. I don't have a different amp to swap out and test with, so any recommendations are welcome!

 

i don't really see a reason the tweeters should have a significantly lower output. at the very least, verify the tweeters are connected to the "T+/T-" outputs, with the woofer being connected to the "W+/W-" output. that's really the only thing i can think of that would cause a lower tweeter output.

i haven't used that specific model, but have a different variant in a project, and the tweeters are equally balanced with the woofers.

$27 Audiotek -CX2-300 Watts Maximum Power 2 Way 4 Ohm Car Audio Passive Crossover Networks/High and Low Frequency Response/Crossover- 3500 kHz (Pack of 2)

https://www.amazon.com/gp/product/B08FBMNSPG/

the model you have is built with slightly better quality components, but is functionally identical.


streetwires zero noise cables are no longer available, i believe the streetwires brand was absorbed by another company about 5-10 years ago. but the principle is still very much alive in a number of other cables. though after all the money i put into them, i never found any performance difference. the marketing team never even sent me a thankyou card either.

this is a newer variant of the same twisted pair concept

$15 RECOIL RCI417 100% Oxygen Free Copper 17ft 4 Channel RCA Audio Cable Twisted Pair with Noise Reduction, Speaker

https://www.amazon.com/Recoil-Oxygen-Channel-Twisted-Reduction/dp/B08DCLKNL9?th=1

but i would instead recommend something like this

$38 Bass Rockers 17ft Interconnect RCA Audio Cables (Bulk 10 Pack) - BRC17 (17 Ft)

https://www.amazon.com/Bass-Rockers-Interconnect-Audio-Cables/dp/B01IRO1TWS/

i've found that many of the 'house brand' interconnects tend to perform as well or slightly better than any of the name-brand products on the market, where most of the twisting, coloring, and extra price really only goes towards the marketing team, and not improved end-user performance. that above cable has a full shield around the center positive conductor, and gold-plated ends, which is what all the really high-dollar cables use, only with longer marketing paragraphs, fancier-looking connectors, and higher price tags.

if that's still far too cheap for your preference, my next-higher recommendation would be crutchfields house-brand cables, or monoprice's cables that offer similar performance with slightly better end-fittings for slightly more money per cable.

my car's audio build also uses instrument cable, similar to these cables, but i built custom-length cables from parts express components

17 Foot RCA Cable Pair - Audioblast HQ-1 - Ultra Flexible - Dual Shielded (100%) High-Definition Audio Interconnect Cable and Neutrik-Rean NYS Gold RCA Connectors (2 Cables, Each 17 Foot Long)

https://www.amazon.com/Foot-RCA-Cable-Pair-High-Definition/dp/B07CVTQXH3

my later tacoma build(currently side tracked to other projects) will be using mogami w2528 zipcord cabling with ali-express-sourced fittings, but is essentially the same as the above pre-fab cables, only with extra steps so i end up with the perfect cable length.