JBL stereo tweak

Hoo Boy! Where do I begin?

One word.... Phase Shift! The human ear is sensitive to phase shifts as little as 1% if it produces odd-order harmonics (like the system in the Prius).

One of the most annoying features of the Prius system is that it is highly equalized to get a reasonable semblance of flat frequency response out of those crap JBL speakers. In doing so they created some hefty phase shifts. Hard phonemes in the right frequencies have a real edgy sound to them... it almosts sounds like clipping. Low end is boomy and unnatural. I can't believe that a company (JBL) with this many years of experience still can't get it close to right. In the audiophile circles I've been in over the last 35+ years JBL wasn't even on the radar for good reasons.

Throwing on another filter will exasperate this condition further. Without a good transient analysis of the system it's all just guesswork.

That said, it depends on where you're going to do the filtering. If it's at the last stage (power amp to the speakers) you really don't want an active crossover since it has to deal with a lot of current.

Active crossovers work well when placed in the early amplification stage (preamp to amp connection). Since the impedence of the amp is more or less constant, you'll get better spectral behavior. The active crossover needs much less critical design than a passive one and (for the most part) won't change over time since the components aren't stressed.

An interesting thought just occurred to me... With the inverter pushing relatively high voltage already why didn't someone harness this in an electrostatic speaker? It would require working with Toyota closely, but it has the potential to make a system that far exceeds the audio accuracy of anything on the road (as long as you're not a dB freak).

 

The front speakers are already filtered digitally at the preamp stage. There are 4 front speaker outputs, not counting center (which also has a high pass on the preamp side). Right and left lower speakers, and right and left tweeters. Only the rear speaker outputs are full range, with passive highpass for the tweeters.

 

Well, prepare to be surprised because Dan is right.

Quote: These work very different then crossovers. (Active or passive.)
Uhh... no they don't. I don't mean to sound snotty here but a crossover IS a high and low pass filter.

Everything GAGendel said was correct too... except "phase shift" is two words :mrgreen:

 

You're right it is semantics. Simply put, a high pass filter is any device placed anywhere in the signal chain that filters lower frequencies and allows higher frequencies to pass through, regardless of whether it is passive, active analog, or active digital. Same with low pass, but for low freqs. A crossover is a combination of each (again regardless of position in the signal chain, and circuitry). The rest is marketing talk.

Tri-way or tri-mode refers to using an external device that produces L, R and mono outputs (the mono generally has low-pass filtering). You could try such a device with the JBL amp to see how it sounds, but since five of the seven outputs already have filtering it could introduce a phase shift which may make it sound worse than it already does.

The only outputs that aren't already filtered are for the rear speakers. If you really wanted to do it right, and still retain the stearing wheel controls, beeps, etc. (and have the money burning a hole in your pocket), you could do the following...

Disconnect all of the speaker outputs and take the rear door L and R outputs and attenuate them down to line level. Run that signal into an active crossover with front/rear fade adjustment, and sub-out. Run those outputs into new amps to power your door speakers and sub (which you'll want to add), and don't connect the front center speaker at all. If you keep the JBL tweeters in the rear doors, you should remove the capacitor (high pass filter) on the back of each.

Anything shy of that will be a compromise (which is fine if you don't want to spend the cash). Do some searching/reading of the old posts here to get a better handle on what you're up against with the JBL "Premium" :roll: system.

I've got some other ideas that are less drastic (read: cheaper), but I've run out of time here. I'll post more later.

 

My understanding with tri-way or tri-mode is an amp system where the signal is split into 3 bands: low, mid, and high, and usually each band is then individually amplified. The amplifiers can be designed to be more efficient for the band they are intended to amplify, and the ban splitters can be designed cleaner and cheaper since they don't have to deal with high currents, and usually don't have inductors.

I took a look at the crossover description however, in this context, tri-way/tri-mode means 3 outputs: R&L outputs with high pass filtering where cutoff is fairly low, a bit below where the sub would take over, and a mono output with a low pass filter so that the sub would not get mids and highs that it doesn't need.

 

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You're probably right about that, but as you noted in the second paragraph, in this instance Crutchfield is referring to an external crossover/L+R sum sub out device. I used to work in the audio field, and they really like to invent/recycle jargon.