Don't trust JBL "True 4-ohm Technology" !!

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I had a JVC KD-R980BTS stereo which recently got replaced by a Kenwood eXcelon KDC-X303 to hopefully solve a problem I've been having which is that after about 20 minutes of loud listening it'll begin to distort real bad and eventually cut out entirely, so I thought the amp in the JVC was going out. Lo and behold, the Kenwood did the same thing! I was super upset and then I remembered something: I replaced all my door speakers with JBL GX602s about a year ago, which then come to think of it, is the time the JVC began acting up the way it had been. I looked up my JBL speakers and they're not actual 4 ohm speakers like the salesman told me. They're 2.3 ohms but marketed as having "true 4 ohm technology," supposedly, after you account for the resistance from the car's wiring harness, up at the headunit the speakers will be seen as 4 ohms. Spoiler alert, that's a load of bull! I pulled my stereo out of the dash and metered at the harness, the highest resistance I saw was 2.6 ohms. I pulled the JBLs out and dropped in a set of Fosgate Punch 3-ways and problem solved. They lasted over an hour at full tilt so they pass my test lol.
 
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Not an audio guy, but I'm guessing the speaker should look like 4 ohms at 20Hz through 20k, right? and who cares at DC? Are you running some sort of AC sweep to look for impedance over frequency? As far as distortion after 20 minutes... is the amplifier getting hot by any chance? Then again, you say you replaced the JBL's and all is fixed, so problem probably isn't amp related. Are these pure speakers? I wonder if they have some crossover component that is heating and drifting (or breaking down). Then again, I still wonder about the amps running hot with the bad speakers.
 
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Impedance versus resistance. In home audio you need a lot of amplifier to run speakers that have low impedance at certain frequencies. I still have a couple amplifiers that weigh in near 50 pounds and they aren't the heaviest out there by a long shot. Of course there may be an issue with the JBL's or you just might not have enough real amplifier. I'm not counting the class D's that drive the sub(s).
 
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You don't test speaker impedance with DC. But if the VC r measures well below 3 ohms DC, it's not a 4 ohm speaker The speaker impedance will dip pretty low above the bass resonance point to near 1/2 its "average" rating then level off in the upper bass /lower midrange at the near Nominal rating. Here is a plot of an 8 ohm nominal speaker in a ported enclosue ( note the camel-hump shape of the curve in the bass) Note the approx 3-1/2 ohm measurement in the lower midrange [Linked Image]
 
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Interesting. I have some very nice JBL 6x8 from a few years back that sound amazing. Finally put a HU in which is worth a dang and they are just fantastic. Sorry to hear the new models aren't up to snuff.
 
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The speakers were asking to much from the amp, I think they call that clipping. Glad you fixed it with new speakers. OP how do they sound at lower volume, the Rockford's were on my list but went with Infinity instead.
 
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Paired with the Kenwood eXcelon headunit, they sound absolutely beautiful. So crisp and clear it's almost unreal, not too "tinny" sounding, it's nice, full and rounded. I have the HPF set at 120hz so I'm basically only using the tweeter portion anyhow, my subs in the trunk take care of the lows.
 
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Harman pulled the same stunt with the JBL sound systems offered as an option in Toyotas - except they use the JBL amp and low impedance speakers. The amp has a DSP and uses digital trickery for fade/balance, the head unit/HMI simply pipes in analog stereo and IEBus commands to the amp.
 
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Originally Posted by ARCOgraphite
You don't test speaker impedance with DC. But if the VC r measures well below 3 ohms DC, it's not a 4 ohm speaker The speaker impedance will dip pretty low above the bass resonance point to near 1/2 its "average" rating then level off in the upper bass /lower midrange at the near Nominal rating. Here is a plot of an 8 ohm nominal speaker in a ported enclosue ( note the camel-hump shape of the curve in the bass) Note the approx 3-1/2 ohm measurement in the lower midrange [Linked Image]
A speaker presents a mostly inductive load to the amplifier. Impedance varies with frequency. It's impossible to get an even impedance over any significant frequency range.
 
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Used to be speaker manufacturers would advertise their speakers as "nominal impedance" when referring to their established number (2, 4, 8, 16 ohm, etc.). Nominal: , being, or relating to a designated or theoretical size that may vary from the actual
 
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Originally Posted by cwilliamsws6
I had a JVC KD-R980BTS stereo which recently got replaced by a Kenwood eXcelon KDC-X303 to hopefully solve a problem I've been having which is that after about 20 minutes of loud listening it'll begin to distort real bad and eventually cut out entirely, so I thought the amp in the JVC was going out. Lo and behold, the Kenwood did the same thing! I was super upset and then I remembered something: I replaced all my door speakers with JBL GX602s about a year ago, which then come to think of it, is the time the JVC began acting up the way it had been. I looked up my JBL speakers and they're not actual 4 ohm speakers like the salesman told me. They're 2.3 ohms but marketed as having "true 4 ohm technology," supposedly, after you account for the resistance from the car's wiring harness, up at the headunit the speakers will be seen as 4 ohms. Spoiler alert, that's a load of bull! I pulled my stereo out of the dash and metered at the harness, the highest resistance I saw was 2.6 ohms. I pulled the JBLs out and dropped in a set of Fosgate Punch 3-ways and problem solved. They lasted over an hour at full tilt so they pass my test lol.
So I just quickly googled these speakers and found: [Linked Image] The manual, AVAILABLE HERE confirms this. So yeah, driving a 2.3ohm load with an amp designed for 4ohms, it is not surprising that you had problems.
 
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See that right there is why I am as upset about it as I am. Depending where you look you'll find the speakers I had listed as being 2.3 ohm, 3 ohm, or 4 ohm. It's confusing and I doubt I'm not the only one who has had this issue because of it.
 
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Originally Posted by cwilliamsws6
See that right there is why I am as upset about it as I am. Depending where you look you'll find the speakers I had listed as being 2.3 ohm, 3 ohm, or 4 ohm. It's confusing and I doubt I'm not the only one who has had this issue because of it.
Yup, the manual lists them as having 3ohm coils with the nominal impedance as 2.3ohms, per the above chart. I could definitely see them causing an issue with an amp that's not capable of comfortably driving loads below 4ohms.
 
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for those of us who've been doing pro audio and being around for a long time, 2.3 ohms is mildly terrifiying. there's not much room between 2.3 and a short. of course it pulls on the amp harder. It also could make the cone harder to control, as the amp has to dampen the charge backfed from the speaker, and less coil makes it harder to do that. I'm all about one 8 ohm driver per amp channel, when I can have it my way. That said, with a tolerant amp, I've had the 2.3 ohm JBLs sound just fine in several cases once adding a compensation network for the overly-present tweet separates. PS if you're in a pinch, a low beam bulb is about 2.6 ohms when hot. put it in series with a 2.3 ohm speaker and you effectively have 5 ohms, which is amp safe, and less resistance when cold. IDK maybe 2. That's at 55W. A 65W high beam would be a little less. But note - If you push your system /hard/ they will light up and warm up. Though I've never tried it, I don't think it would effect the sound much. It might warm up the lows. (haha)
 
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You mentioned the speakers in question were the vehicle's door speakers, but many car's stock speaker configuration nowadays will have tweeters in the sail panel or dash speakers (acting as tweeters) which will be wired in parallel with the door drivers. I am wondering if your vehicle has this setup...if it does, the load the h/u's amp sees is the combined impedance of the door driver and tweeter/dash speaker (multiply the two speakers' nominal impedance values and divide that by their sum; the result is the impedance the amp sees). Just a thought, not much help now though. Good to hear you got it resolved eventually though. Nuke
Originally Posted by cwilliamsws6
I had a JVC KD-R980BTS stereo which recently got replaced by a Kenwood eXcelon KDC-X303 to hopefully solve a problem I've been having which is that after about 20 minutes of loud listening it'll begin to distort real bad and eventually cut out entirely, so I thought the amp in the JVC was going out. Lo and behold, the Kenwood did the same thing! I was super upset and then I remembered something: I replaced all my door speakers with JBL GX602s about a year ago, which then come to think of it, is the time the JVC began acting up the way it had been. I looked up my JBL speakers and they're not actual 4 ohm speakers like the salesman told me. They're 2.3 ohms but marketed as having "true 4 ohm technology," supposedly, after you account for the resistance from the car's wiring harness, up at the headunit the speakers will be seen as 4 ohms. Spoiler alert, that's a load of bull! I pulled my stereo out of the dash and metered at the harness, the highest resistance I saw was 2.6 ohms. I pulled the JBLs out and dropped in a set of Fosgate Punch 3-ways and problem solved. They lasted over an hour at full tilt so they pass my test lol.
 
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United States
Originally Posted by The_Nuke
You mentioned the speakers in question were the vehicle's door speakers, but many car's stock speaker configuration nowadays will have tweeters in the sail panel or dash speakers (acting as tweeters) which will be wired in parallel with the door drivers. I am wondering if your vehicle has this setup...if it does, the load the h/u's amp sees is the combined impedance of the door driver and tweeter/dash speaker (multiply the two speakers' nominal impedance values and divide that by their sum; the result is the impedance the amp sees). Just a thought, not much help now though. Good to hear you got it resolved eventually though. Nuke
This is not accurate. All speakers on a passive crossover circuit are wired "in parallel". In the configuration you describe between the capacitor on the tweeter and inductance of the voice coil of the woofer the apparent load on the amp will not be half the impedance of both drivers.
 
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920
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My stock 3.5" dash speakers were 8 ohm, and the stock door drivers were 4 ohm. It was my understanding that configuration presented a nominal impedance of approximately 3 ohm to my stock head unit. My current dash speakers are 4 ohm, and the doors are 3 ohm. It is my understanding that my amp sees approximately 2 ohm (nominally) on each channel out of that configuration. If I am misunderstanding all that, I would appreciate knowing what is the correct info or how to calculate it. But either way, my point with the original reply was to point out the expected impedance at the head unit from the new speakers would not be what it actually sees if the car had other speakers wired in parallel on the same channel. Surely we can agree that is correct?
Originally Posted by CaptainHazelwood
Originally Posted by The_Nuke
You mentioned the speakers in question were the vehicle's door speakers, but many car's stock speaker configuration nowadays will have tweeters in the sail panel or dash speakers (acting as tweeters) which will be wired in parallel with the door drivers. I am wondering if your vehicle has this setup...if it does, the load the h/u's amp sees is the combined impedance of the door driver and tweeter/dash speaker (multiply the two speakers' nominal impedance values and divide that by their sum; the result is the impedance the amp sees). Just a thought, not much help now though. Good to hear you got it resolved eventually though. Nuke
This is not accurate. All speakers on a passive crossover circuit are wired "in parallel". In the configuration you describe between the capacitor on the tweeter and inductance of the voice coil of the woofer the apparent load on the amp will not be half the impedance of both drivers.
 
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