How to upgrade your 1st Gen Klipsch Jubilees to 2nd Gen (Heritage) Jubilee Acoustic Performance

[weltersys]

My basic view is that reflex ports are really a relic of using passive crossovers without corrective EQ (as DSP crossovers can and do provide).

In the Heritage Jubilee, the reflex ports are the only way to get the ~22Hz extension and keep cone excursion to the point of not ruining the upper response, the significant amplitude modulation (AM) you mention in your paper.
The Heritage Jubilee ports appear to be ~ 12" long, so their first pipe resonance would likely be above 500Hz, high enough to be removed with steep filters and not interfere (too much) with the low crossover point made possible with the Axi2050 HF driver.
Like Roy Delgado said, this design won't work without DSP

I did see the higher Q disturbances in the bass bin amplitude and phase response (acoustic) as well as apparent higher Q boosts and notches in the transfer function output from the Klipsch-provided DSP crossover (with about a 320 Hz crossover frequency, shown below)....Note the higher Q corrections at 62, 115, 175, 215, and 260 Hz that are (I assume) there to correct perceived min-phase amplitude issues.

The correction at 62Hz probably is around where the relatively short expansion horn response starts to fall off and is augmented by the bass reflex port response. The other boosts and notches in the transfer function may be related to the various horn sectional resonances.
It would be nice if all the sound waves actually marched along like the blue arrows

I'd definitely prefer the 2-way sealed MEH/ TH sub approach you took with your home system rather than pushing the limits of what is possible with a separate two-way horn system covering 20-20kHz.

There is no special DSP correction at 80 Hz, saying to me that this is much more likely a room mode (i.e., the owner's room) instead of a bass bin design issue. (I don't have anechoic measurements of this loudspeaker.)

..I think that's a quarter wave floor bounce cancellation of the microphone placement. When you move the microphone up or down, that notch frequency moves with it. Remember that all these measurements are taken in-room, not outside.

Late night oversight, should have realized the measurements have floor bounce and are off axis to the LF horn exits.

I realize few would be willing to haul these monsters outside, but it would be interesting to see a ground plane measurement near one of the bass bin exits.

Cheers,
Art

 

[Cask05]

In the Heritage Jubilee, the reflex ports are the only way to get the ~22Hz extension and keep cone excursion to the point of not ruining the upper response, the significant amplitude modulation (AM) you mention in your paper.

That clearly is a controversial design decision. Instead, offering a separate horn-loaded subwoofer to complement the 1st-Gen bass bin design would have been a much more workable approach.

Other questionable design decisions include:

1) The provided DSP crossover apparently produces only IIR filters (that aren't correcting phase growth)...and the DSP unit is fixed, i.e., the user can't adjust anything to dial-in these $35K-$40K/pair loudspeakers into their chosen room placements. The crossover filters used produce a pretty big kick in the phase growth (audible excess group delay spikes at crossover--as mentioned above). And since the bass bins have such large mouth areas, they easily pick up boundary gain, leading to overwhelming low frequency bass response that the Klipsch DSP box can't correct with its fixed settings. This leads to a second controversial design decision...

2) The fixed EQ from the DSP box was only designed to have flat response in half space (i.e., 20+ dB of bass boost is built into the DSP unit) to turn these corner horns into free-standing loudspeakers (with its attendant increase in bass modulation distortion at higher SPL). When you consider that almost anything near the front of the owner's room will eventually be inside the 1/4 wavelength boundary gain radius at some low frequency point, they've created an unresolved issue. Owners apparently have uniformly had problems getting these loudspeakers to integrate well below 100 Hz in their listening rooms, not aware of the fixed half-space EQ implementation in DSP. This is nuts...since this loudspeaker possesses full-range directivity in order that it can be placed in a room corner without incurring midrange/midbass early reflection issues incurred by typical direct-radiating loudspeakers placed in corner loading. Trying to use these loudspeakers in room corners will produce overwhelming bass response of 18 dB too much bass at ~25 Hz.

I've also found that all the canned "room correction software" packages are ill-equipped to deal with this type of loudspeaker (i.e. full range directivity down through the midbass region). They consistently produce thin sterile sound via overcompensation of midbass response that negates the directivity advantages of these loudspeakers through the room's Schroeder frequency.

Chris

 

[weltersys]

Owners apparently have uniformly had problems getting these loudspeakers to integrate well below 100 Hz in their listening rooms, not aware of the fixed half-space EQ implementation in DSP.

The owners must have not "experimented" like the manual suggests

"• Placing them near a corner or wall provides the greatest amount
of bass while moving the speakers away from room boundaries
reduces bass energy.
• Asymmetrical placement of a pair of speakers from adjacent side
walls can smooth room-induced bass unevenness.
Experiment with the above guidelines to suit your taste and to
compensate for your room’s acoustic characteristics."

Just get your crew together and move your speakers, video monitor, sofa and room furnishings around until it suits your taste

 

[Cask05]

...but first, just make sure that each loudspeaker is at least ~20 feet from the walls or ceiling.

How absurd.

Get yourself a good DSP crossover--something like a Xilica Solaro or better--and a measurement app like REW plus measurement microphone with stand.

I've got PEQs and crossover settings for DSP crossover that Heritage Jubilee owners can use to jump start the process of dialing them in with a good third-party DSP crossover. Send a PM if interested.

Chris