State-of-the-Art Loudspeakers

[Sal1950]

It has a passive high pass filter for the horn.

JBL M2 Tech Manual

View attachment 21277

Humm, @dallasjustice describes it somewhat differently.
"The JBL M2 is 2 way speaker system without a passive crosssover. There is a protection circuit built into the speaker which is designed to protect the D2 compression driver from DC and excessively loud low freqeuncy noise. Harman recommends an 800hz crossover for the JBL M2.
https://www.audiosciencereview.com/...nse-digital-crossovers-w-subs.2369/post-66200

 

[RayDunzl]

Humm, @dallasjustice describes it somewhat differently.

He's a lawyer. You can't trust what they say, especially of you aren't paying them.

---

How would you describe the circuit shown above?

Hint:

The JBL network has an additional resistor (R1), forming a voltage divider with R2, that would further reduce the voltage applied to the compression driver.

 

[Sal1950]

How would you describe the circuit shown above?

I'm not qualified.

 

[andreasmaaan]

He's a lawyer. You can't trust what they say, especially of you aren't paying them.

---

How would you describe the circuit shown above?

Hint:

View attachment 21281

The JBL network has an additional resistor (R1), forming a voltage divider with R2, that would further reduce the voltage applied to the compression driver.

IMO it corrects the HF driver’s downward sloping response and attenuates its output to match that of the woofer.

 

[RayDunzl]

The M2 is properly characterized as a semi-active loudspeaker.

In that case, my Martin Logans are properly characterized as semi-active loudspeakers, too.

They don't have a crossover, just separate filters.

 

[Blumlein 88]

What would you call this circuit for Acoustat full range panels? You split the ratio for different frequencies in the transformer, but then mix it all together again. Is this active, passive, semi-ap or what? It might be considered a frequency contouring circuit.

 

[RayDunzl]

Looking at that 500meg resistor on the Acoustat bias supply...

 

[DonH56]

The circuit to the M2's tweeter is technically a high-pass filter but is not a 5 kHz crossover; it's corner frequency is much lower. I'm not sure the driver's impedance but the corner looks to be around 200 Hz; the specified crossover frequency is 800 Hz so I think the capacitor is just for protection as stated above. It's main function is to protect the driver from DC and/or excessive LF energy. The network seems mainly to attenuate the signal to the driver to match the woofer's sensitivity making it easier to use a simple crossover and amplifiers with the same or similar gain.

 

[vitalii427]

It has a passive high pass filter for the horn.

JBL M2 Tech Manual

View attachment 21277

Sure, but still you can’t use one amp.

 

[Theo]

In the 70's/80's, Philips and Cabasse (and probably others) were making active loudspeakers with a motion feedback sensor helping reducing distortion. I suppose today's digital models are able to predict the speaker behavior, thus being able to process the signal without a sensor (a la Devialet SAM system?). Is there any active design including sensors today?

Coming back to the OP, as the room is part of the speakers in it, isn't room treatment the way to go rather than new speakers. You may be able to do a lot of redecorating with 10k$+.

Speaking of SOTA, here is a non-conventional (passive) speaker design. Any thoughts?

Leedh E2

 

[Deleted member 2944]

The circuit to the M2's tweeter is technically a high-pass filter but is not a 5 kHz crossover; it's corner frequency is much lower. I'm not sure the driver's impedance but the corner looks to be around 200 Hz; the specified crossover frequency is 800 Hz so I think the capacitor is just for protection as stated above. It's main function is to protect the driver from DC and/or excessive LF energy. The network seems mainly to attenuate the signal to the driver to match the woofer's sensitivity making it easier to use a simple crossover and amplifiers with the same or similar gain.

Apparently that published schematic has a misprint and the 33.3uF capacitor is actually a 3.3uF capacitor. So, more of a HP filter than it seems.
Dave.

https://docs.google.com/document/d/...accepted+++&rm=minimal#heading=h.267sxg2itu1h

http://www.audioheritage.org/vbulletin/showthread.php?39267-JBL-M2-DCX2496-settings

 

[RayDunzl]

Using R for 32 ohm impedance of the compression driver:

 

[jhaider]

Why would a speaker which is designed to run bi-amplified downstream of a DSP have a passive high pass filter on the HF unit?

Don't forget that the M2 is a studio monitor originally designed to be used with touring amplifiers. I suspect the reason for the resistors is not to match levels (easily doable in DSP) but simply to reduce hiss by attenuating the signal.

 

[DonH56]

@dreite -- Thanks, that makes more sense. So my earlier analysis was wrong and it probably is the 800 Hz high-pass filter for the tweeter (hey, not my fault, GIGO, or what I get for trying to post whilst working, but it was Saturday, and here I am working and posting on Sunday too).

For 800 Hz, using an 8 uF capacitance (3.3 uF + 4.7 uF = 8.0 uF), the R would need to be about 25 ohms. Ray's circuit shows 13 + 11//32 or about 13 + 8 = 21 ohms, reasonably close.

The divider is to attenuate the signal to the driver to match gains or, as @Ron Texas said, to reduce hiss (probably more likely). It does not influence the corner frequency, but the driver itself is not a pure resistance and will shift the curve.

 

[andreasmaaan]

The acoustical crossover slope is a lot steeper (approx. 48dB/octave IIRC) than that provided by the passive filter. I haven't actually looked at the DSP settings (not sure they're published in any case), but I presume there is an additional rather steep active HPF interacting with the passive filter to produce the correct acoustical filter slope and a flat response in the passband.

 

[Deleted member 2944]

Yes, it does seem a perfectly simple solution that kills three/four birds with one stone. Provides a portion of the necessary crossover HP.....provides a simple pad to better match the efficiency of the woofer....provides post-amplifier noise reduction.....and provides DC (and some transient) protection for the compression driver.

 

[DonH56]

I don't know about the acoustic crossover (that would be at the output of the driver and usually refers to the cabinet construction, not sure that applies here?) The electrical crossover in the DSPs I do not recall, have to check with some friends, but I am pretty sure it is at least 24 dB/oct (standard Linkwitz-Riley) very likely higher (not disputing your 48 dB/oct number, but strongly suspect it is in the crossover before the driver and not part of the acoustical design of the horn/waveguide).

 

[andreasmaaan]

I don't know about the acoustic crossover (that would be at the output of the driver and usually refers to the cabinet construction, not sure that applies here?) The electrical crossover in the DSPs I do not recall, have to check with some friends, but I am pretty sure it is at least 24 dB/oct (standard Linkwitz-Riley) very likely higher (not disputing your 48 dB/oct number, but strongly suspect it is in the crossover before the driver and not part of the acoustical design of the horn/waveguide).

Yes, I think my earlier post was misunderstood. By acoustical crossover, I meant the total acoustical output, which is mostly accounted for by the active filter. So I think we're in agreement actually.

 

[Sal1950]

Speaking of SOTA, here is a non-conventional (passive) speaker design. Any thoughts?

Leedh E2

Looks more like a Shoe Shine machine

 

[Hugo9000]

Looks more like a Shoe Shine machine

In the 70's/80's, Philips and Cabasse (and probably others) were making active loudspeakers with a motion feedback sensor helping reducing distortion. I suppose today's digital models are able to predict the speaker behavior, thus being able to process the signal without a sensor (a la Devialet SAM system?). Is there any active design including sensors today?

Coming back to the OP, as the room is part of the speakers in it, isn't room treatment the way to go rather than new speakers. You may be able to do a lot of redecorating with 10k$+.

Speaking of SOTA, here is a non-conventional (passive) speaker design. Any thoughts?

Leedh E2

View attachment 21289

I was thinking the designer came up with it after spending too much time at the gym using elliptical trainers haha! See the footpedals (and the slope of the base), the handlebar area, and where the electronic display would be?