which crossover?

**Stovebolt6** · April 27th, 2003, 06:38 PM

I'm putting together a pair of speakers with 511b/909-16a (16 ohm) and 515e (16 ohm). Which crossover should I use?

Thanks,

Dan

**eibei** · April 28th, 2003, 05:20 PM

Hi Dan:::

If everything else works out for you stay with the lowest crossover possible [at 500 Hz your woofer is begining to break up.] Assuming that you feed the woofer a pure tone [500 Hz the cone is no longer action as a rigid piston.]
So with a 416 type woofer and 800 series horn drivers - I would like 500 Hz.

Lynn

**AllanCT** · April 28th, 2003, 08:57 PM

Variable electronic one is what I would use. forums

**dennis gilliam** · April 29th, 2003, 03:09 AM

Perhaps the thing to do is try a number of CO frequencies, as there is no hard and fast rule other than the cutoff for the horn & driver. since you already have a pretty low-working horn, the choice is where you like it.

I'd recommend something between 500 Hz and 1200 Hz.

Things will vary widely according to the divisions brought about by the CO freq.

The most cost-effective thing to do is use an electronic CO ahead of a biamp setup, and twist the knob whilst listening to your favorite program material.

Short of having this facility, you might try piecing together a cheap & simple CO network for one speaker, taking note of where you like the transistion and then buying an Altec CO pair closest to that.

It makes an amazing difference on systems like the A7 & A4 with this technique, on parallel with important adjustments like horn/woofer alignment, bass port size, and room volume.

Best of luck and obey your ears,

DG

**ngccglp** · December 16th, 2007, 02:40 AM

Originally posted by Lynn W. Russell:
Hi Dan:::

If everything else works out for you stay with the lowest crossover possible [at 500 Hz your woofer is begining to break up.] Assuming that you feed the woofer a pure tone [500 Hz the cone is no longer action as a rigid piston.]
So with a 416 type woofer and 800 series horn drivers - I would like 500 Hz.

Lynn

How is this possible when the stock A7 crossover point is 800 hz? The spec of the 416 states flat response up to 1600 hz. Is this correct?

**LICORNE** · December 16th, 2007, 03:05 AM

I'm not getting at what your trying to explain.
The A-7 is a horn type cabinet . When used with a 416 you need a lot of room to appreciate it's prowess. Now the crossover points would be in the
500 and 800 region to remain with in the A-7 characteristics. The 416 is also suited for the Magnificient, Valencia and the Model 19 wich have XO of 800 and 1200 HZ.

Hope this answers your question.

**bfish** · December 16th, 2007, 08:40 AM

TL 237 gives a good explanation of the effect. Figure 3 shows generalities of the relationship of driver diameter to frequency-related directivity. Some specifics are given for the 416-8B (in a 140" perimeter flat baffle) in Figure 7. It shows 160 degree or greater dispersion (to -6dB) up to 800Hz. At 800Hz, it abruptly begins to narrow, and by ~1200Hz, is down to 90 degrees. The charts also show that the effect is impartial to brands and models, it's strictly a size thing.

In an A7, the LF horn has some control of directivity through its' BW, but above that, directivity is more a function of the driver diameter.

With the goal of making a smooth transition from LF to HF, it becomes obvious that one should select a crossover point at which the directivity of the LF and HF horns are ~equal. Keep in mind that while a HF horn may be rated at 90 degrees, it loses control at a (unit dependant) point, and begins to widen at lower frequencies.

TL 201 gives frequency dependant directivity data for many Altec horn/enclosure combinations.

[ December 16, 2007 05:19 AM: Message edited by: bfish ]

**ngccglp** · December 16th, 2007, 04:26 PM

Hi Convergence.

What I was trying to understand is the meaning of 416 breaking-up at 500 hz? Thanks

**bfish** · December 16th, 2007, 04:41 PM

Originally posted by ngccglp:
...How is this possible when the stock A7 crossover point is 800 hz? The spec of the 416 states flat response up to 1600 hz. Is this correct?

When the wavelenth is larger than the driver, the cone moves as a piston, and dispersion is broad and fairly uniform. As F rises, the WL gets smaller. When it becomes smaller than the cone, the cone "breaks up" (physically wrinkles) in a region corresponding to the wave size, and the dispersion begins to narrow rapidly. To say a 15" driver (~13.5" cone) has smooth response to 1.6KHz is somewhat misleading, as it only references the on-axis response.

The 500-800Hz XO points on A7s were chosen to best match the collapsing LF directivity to the respective HF horn patterns at those XO points.

[ December 16, 2007 05:31 AM: Message edited by: bfish ]