Jager crossover frequency spec

[joepiecuch]

2800 Hz; what order/slope?

[Paul Birkeland]

2800 Hz; what order/slope?

Electrical or acoustical?

[joepiecuch]

Well...I don't know. I need to order the circuit board modules for a marchand xm26 in anticipation of switching from straight 8s to Jagers. I thought I pretty much understood what I was asking, but I guess I don't!

[Paul Birkeland]

That's the electrical side. 

The tweeter is a 2nd order Linkwitz-Riley at 2.8kHz.

IIRC the woofer should be a 3rd order Linkwitz-Riley at 2.8kHz. 

I'd let PJ weigh in before ordering modules, as those suckers are pretty spendy.

[Jamier]

PB didn't mention the acoustic slopes, but a Marchand is 24db/oct, so can you use the Marchand with a Jaeger?
The Silver Flute cone doesn't have a big breakup above the xover point, so the slope is probably not that steep in the stock xover.

Jamie

[Paul Joppa]

The woofer is 3rd order Butterworth, tweeter second order Linkwitz-Riley.

[Paul Joppa]

To clarify, the drivers are passively equalized between the crossover and the driver. This is done to make it possible to use standard, well-known external crossover functions.

The equalized tweeter acts like a second-order highpass at 2800Hz, with a Q of 1.0. If it is driven with a second-order high-pass function with a Q of 0.5 (i.e. a second order Linkwitz-Riley), the combination approximates very closely to a fourth-order Linkwitz-Riley.

The equalized woofer acts like a first-order lowpass at 2800Hz. If it is driven by a third-order Butterworth filter, the combination approximates very closely to a fourth-order Linkwitz-Riley.

Thus the acoustic crossover is a fourth-order Linkwitz-Riley.

[Jamier]

The Silver Flute has some cone breakup around 4300 Hz. Although it is not a huge bump, would the passive EQ from the stock Xover remain in place to smooth this out,even with an active Xover in place? I think this was what you were describing in your explanation. Now that I see the curve I can see why you went with 24db/Oct (with a Xover point of 2800 Hz. )

Jamie

[joepiecuch]

The XM26 can be configured with 6, 12, 18 or 24 dB/oct curves. The frequency modules are only $15/per, but a $60 investment is nothing to sneeze at. I am curious to know if it's advisable to leave the tweeter side of the passive in place downstream of an active. Thank you, all.

[Paul Birkeland]

You want to leave all of the components mounted in the box in place if you use an active.  The tweeter is not so delicate IMO that you need the protection cap.  One way that I deal with that concern differently is to buy the hole plugs for the banana portion of the speaker binding posts, then plug the holes in the tweeter binding posts and only use your banana speaker cables for the woofer side of things.  That way it is more difficult to accidentally connect the woofer amp to the tweeter amp.

[joepiecuch]

Do you mean leave just the impedance compensation board in place? (I figured that would be the case.) Or leave both that and the passive xover board in place but connect directly to the binding posts on the back of the cabinet?

[Paul Birkeland]

Yes, leave the impedance boards in place.  The x-over board in the bottom cubby can be removed.

[Paul Joppa]

The Silver Flute has some cone breakup around 4300 Hz. Although it is not a huge bump, would the passive EQ from the stock Xover remain in place to smooth this out,even with an active Xover in place? I think this was what you were describing in your explanation. Now that I see the curve I can see why you went with 24db/Oct (with a Xover point of 2800 Hz. )

Jamie

Yes, the passive eq inside the cabinet removes the bump, leaving a first order (6dB/octave) rolloff from 2800 to about 9kHz. It also cuts out the lower woofer above around 500Hz, and compensates for impedance fluctuations form all the eq and and woofer inductance, leaving a constant ~8 ohms.

The tweeter eq reduces its sensitivity to match the woofer, provides some treble boost to flatten the response, and compensates the impedance fluctuations leaving a constant ~8 ohms.

The real reason for targeting a 24dB/octave was to maintain the beaming to straight ahead; odd-order crossovers send the interference beam either up or down through the crossover region. For that reason I do not advice trying different order filters than the ones specified.

[joepiecuch]

Thank you both again.

[Jamier]

PJ, in my limited experience, Beaming is an issue when ever I cross woofers near the upper end of their useable range. The upside is these designs often are very good on axis (but lose coherency off axis). 2.5 way TMMs are generally not very good in the near-field because the “sweet spot” is not focused in a location for near-field listening and floor bounce is hard to control. Would the Jaeger, perhaps, be a good near-field TMM? The bass response of the speaker might be too much for a small room (10x15x8), but that could be adjusted, perhaps? The straight forward Beaming has me interested since these cones are wool. Beaming with metal cones tends to be obnoxious, but with softer materials it can be used constructively, especially in the near-field.

Jamie