KSP-400 D'appolito Driver Crossover 3rd Order? Update?

[syzygy]

I am ignorant regarding the crossover and driver frequency ranges on the KSP-400. What I would like to know is if the KSP-400 uses the same frequency range for both mid drivers or are they staggered/overlapping? The 400 is supposed to follow the D'appolito design that normally entails a 3rd order crossover. Does that mean there are three frequency ranges?

I ask because the upper drivers on my KSP-400 seem to carry the higher frequnecies more than the lower driver.s. Then again, these speakers are now 15 years old and my lower drivers may be "tired" ? Because, they are mine, they have been played at significant volume more than occassionally.

Also, wanting to know if people have replaced caps or updated their KSP crossovers and to what effect?

Thanks in advance.

[WMcD]

I can't say with any certainty, but the set-up looks like the MTM system by Dr. D'A. It would make sense because it is known for the smooth transition,

I believe that to the extent a 3rd order is needed (not sure) it is the acoustic output which has that characteristic, not necessarily the electrical input to the drivers.

At the risk of being pedantic here: Often textbook articles show how the theoretical electrical output of filters will sum -- but to make that translate to the acoustic output requires drivers have a constant output on either side of the crossover freq -- for an octave or so. That is often not possible.

As you can imagine, if the drivers could be rolling off at 6 dB per octave acoutically at the crossover point on their own and the crossover is rolling off at 12 dB per octave, then you wind up with an 18 dB third order acoustic output. Roughly.

A somewhat related issue arises when you have two drivers (say vertical, one over the other) sending out sound at the crossover freq -- which is typically the case. As the phase of two driver shifts, the combined output tilts. So the total sound from a tweeter above a mid will tilt toward the ceiling,or toward the floor depending on the phase difference. The actual phase is relation is difficult to control and shifts with freq.

What to do? .

Enter the genius of Dr. D'A. Use two mids and one tweeter. That way if the tweeter and upper mid steers things up, the tweeter and lower mid steers it down by the same amount. If I understand correctly, you can still have less than perfect phase control, but the on-axis acoustic output remains constant and any upward and downward lobes are equal. Neat!

I can't say whether your lower mids are actually weak. It seems to me it would be difficult to tell by ear. If this is an MTM, their respective outputs should be equal.

I'd say to cover the tweeter horn with a piece of carpet and give a close listen with an improvised stethoscope, like a tube from a roll of paper towels. Or use a RS SPL meter.

Use a constant tone in a range where the mids should be working. The freeware Audacity has a tone generator.

WMcD

.

[syzygy]

Without a response for 48 hours, I briefly thought the robust Klipsch community had lost some of it's gusto or expertise.

I was wrong.

Admittedly, your explanation is somewhat beyond my understanding of crossovers and output but what I do take from your comments is that the speaker provides similar frequnecy output for both mid drivers. Correct?

I recently replaced both upper drivers with NOS drivers because one of the drivers was audibly "resonating" at a certain frequency. Upon swapping out the first driver only I could hear a distinct difference in the sound from the L vs. R speaker. With both swapped out the sound has improved appreciably. Now it seems both lower drivers lack the "sparkle" and "accuracy" of the new upper drivers, although both have similar audible output.

From your explanation, I may need to swap those as well. Even with only two new drivers, these speakers now are legitimately competitve with my fully refurbished Cornwalls powered by a Stromberg tube amp. Whereas before they were relegated to surround sound only.

Thank you for taking the time to provide such a detailed explanation.

My ears thank you as well.

[WMcD]

Good to hear from you.

One the basic requirements is that the upper and lower mid be working in an identical fashion.

You if you're confident they are not, and you can get the proper part, I would suggest you replace the offending units.

BTW, you say NOS. Is that new-old-stock from Klipsch? If they are not fairly close to what Klipsch uses, there may be a problem with the crossover. The crossover will not work properly unless used with the mids (and tweeter) for which they are designed.

WMcD

[syzygy]

The replacements are New Old Stock from Klipsch. I think this post illustrates an important point for vintage or used speakers. The drivers can gradually lose some of their accuracy or whatever one wishes to characterize it as, over time or if used to party "too hard".

The KSP-400 can play ridiculously loud if pushed and that may be what happened, given my recollection of the prior owner. I have two sets of KSP-S6 which use the same driver in surround. So I can compare not only the KSP-400 drivers but also use the surrounds as reference when playing I play them on multi-channel setting which provides equal output to all speakers.

Dinah Washington or Diana Krall vocals now sound more live and nuanced than ever before.

Once again, thanks. For less than two hundred bucks I can bring these back to their former glory, and have "audiophile" quality sound on the cheap.

[EdmundGTP]

Just out of curiosity, where'd you come across NOS drivers for these? Something you sourced a while back?