Pioneer HPM-100 circuit questions. (Super tweeter and transformer)

[Audiotexan]

I am truly trying to follow all of this.
My hat is off to the math wizards.

Mine too!

My only question is 'why crossover the tweeter at 12K?'

Same. (expounded on below)

Xovers that I have worked on run the gamut from 1.5K to 4K for silk dome 1" tweeter.
Maybe up to 8K for a bullet tweeter.

Precisely. And for the most part, that's what they've done for the regular tweeter. Crossover specs as listed in the SM are: 3k (mid), 4k (tweet), 12k (super tweet).

The thing is, I've had speakers with better high frequency response from the soft dome silk tweeter types you mention, than what they chose to use here.

The tweeter is a cone type, so I'll assume that it stops off around 8k...if it was silk/mylar I'd give it another 2-6k (roughly) leeway on the high end. (I really need to freq.sweep the entire cabinets at this point, to see just what exactly is going on! As I hate pulling numbers outta my keister. But as I said before, aside from tweak the 12k crossover point, it's mostly academic/personal curiosity.)

They list the total frequency range as 30hz to 25khz.

I would assume that it depends on the resonant frequency (FS) of the tweeter itself.[/QUOTE]

Agreed. I'm under the impression that that is 10k. So it's not being 'efficient' or maximised, which is why it sits further back in the SPL mix.

This is the super tweeter, there is also a tweeter, drawing is in first post.
So my question, why do you want to lower the xover point for the super tweet?

Good question! As above, I'm under the impression that it's because of being crossed over outside (above and beyond) it's assumed Fs of 10k.

1. So things that it could handle with ease (8k-10k) aren't being routed to it at all. (Which dropping the S.T. x-over point would offset any short-comings of what the T. can't reproduce -if any-)

2. The area of the S.T. that it would have it's natural emphasis (Fs/resonant frequency) is being denied by crossing at 12k. (So anything 12k and higher would naturally sit lower in the SPL mix further reducing the effectiveness of what it's job is.)

[Given that if you swept a speaker in it's usable range, when the Fs of a given speaker is hit, it would output the highest db/w. So that -6db hit @ 12k, might well be a -10db hit since most speakers roll off several db outside of their Fs (assuming since the Fs of the S.T. would appear to be 10k])

At best, all that's being output in it's current state would be a measily 2.5k range. (12k-14.5k as audibly measured through just the transformer and speaker itself out of circuit @ 2v RMS.)

[Audiotexan]

In principle, your figures of -6dB and -15dB are correct if you include the transformer .

But... they don't reflect the actual system performance. It's the sound pressure level that hits you ear that matters and the system i.e. filter, transformer, tweeter, enclosure e.t.c. is much more complex than that simple model.

Hope that helps.

Very true! And also would be the reason I'm in the thick of all this. lol
I also know that they've played with the phase on the ST's (as well as the mids) in this series/model several times. So it was obviously an ongoing issue within Pioneer for some time as they had *at least* 4 different models of crossover within the HPM-100 series alone:
SWN-117-0 (50w vers.)
SWN-117-A (50w vers.)
SWN-158-? (100w vers.)
SWN-166-B (100w vers.) [mine]

Thanks for everything so far nick!

With everything else about these speakers/cabinets being SO phenomenal, it's hard to let the one little tidbit go. *chuckles*
If everything else fails though, at least I can sell them in good conscience, working 100% as designed, and just go back to using my JBL 4412's as my mains.

I also have to think that Bart Locanthi was saddled by Pioneer with the task of using the "high polymer molecular film super tweeter" (where HPM's acronym originates) as a marketing tool. Again, with the rest of the cabinet/speakers being SO perfectly in sync...it's almost as though the ST's were an afterthought. Either that or they couldn't get real quality control on a brand new design. Hard to say.


As an aside... I've actually started looking for a crossover sim, as a result of all this. It'd be nice to play with numbers and get a rough approximation of what to expect before taking iron to pcb. =)

[Jazz P Bass]

Here is a nice Java program: Crossover Design Chart and Inductance vs. Frequency Calculator(Low-pass)

[km6xz]

I did not follow all the thread but from the original post, I suspect nothing is wrong with the headphones at all. You would not expect to hear anything below a very high frequency, the tweeter crosses over to the Piezo at above 18khz so feed it 20k and measure with a scope. By the way, don't expect ANY program content about 21khz if you have program that at some point was 16bit digital, CD or other digital consumer source. The super tweeter is a marketing gimmick and not needed at all. Harmonics up in that range even in live situations away from any digital conversion would be a tiny fraction of the total signal, 0.3% of less, and most heard would be noise. If you were able to hear 22k easily as a child, under 8 it is not terribly unusual but anyone who has been around a few more years or been exposed to loud sounds will be lucky to hear 16K. It is not even important to hear the highest harmonics. Our brain synthesizes higher harmonics of a lower harmonic sequence. Same goes for missing fundamentals when an entire sequence of harmonics above the fundamental is present. Ever listen to old records and not have any problem hearing the kick drum? The fundamental was not even there, but we were aware of it because the second and high harmonics were. We don't hear it but we are immediately aware of it and that it is a kick drum. Records intentionally limited both high and low frequency content, but broadcast legal, disc cutting, time limits, and playback tracking distortion reasons. The more bass on a record the shorter the playing time because the grooves had to be wider between grooves. Broadcast limited bandwidth for technical reasons like adjacent interference, and deviation legal limits.

[Audiotexan]

Here is a nice Java program: Crossover Design Chart and Inductance vs. Frequency Calculator(Low-pass)

Thanks for the link JPB =)

[km6xz]

If you are going to keep going in the "repair" mode instead of looking as function and intent(which appears to be working as designed), be sure to properly assign a value to the transducer that does not throw the calculations off. It is not a low z transducer except at very high frequencies, well above the range of audio since it is essentially a capacitor.

[Audiotexan]

If you are going to keep going in the "repair" mode instead of looking as function and intent(which appears to be working as designed), be sure to properly assign a value to the transducer that does not throw the calculations off. It is not a low z transducer except at very high frequencies, well above the range of audio since it is essentially a capacitor.

Noted and thank you Stan! I do understand the fundamental difference.

Repair-wise, it was done the moment I tested the components and replaced the supertweeters.

The rest is just my extraneous curiosities bubbling to the surface.

I can't do proper planning without driver specs. That's a given.
So trying to sub an abitrary "value to the transducer that does not throw the calculations off" would be pretty much impossible (at least for any semblance of accuracy) at least with my limited knowledge. If you have a/any suggested value(s), I'm all ears!

I have continued to search for sites that have crossover calculators, but everything I've found thus far has been similar to what JPB kindly linked (ultra-basic at best) but they typically don't allow for circuit manipulation, or at least in the manner I need to.

I'm almost tempted to see if I can come up with a way to simulate it in LT Spice. But I've only used that briefly thus far, and initial impressions lead me to believe there's quite a learning curve. Though this might be simple enough for me to give it a whirl.