Need a crossover for my new 400 lb center channel speaker...

**aditya** · August 7th, 2012, 12:40 AM

Many thanks "Panomaniac" for the graphs. I am yet to see a thread on 210s with real graphs. This will be very useful for ref. sake.

From the impedance graphs it seems the dual 515s (assuming they are in the parallel mode) are really 20-24 ohms each (@ 1 K Hz.), as specified. It is surprising that the DC values are at 9 ohms, as measured by 'AA'. Or may be he also had measured the value in the parallel mode, and while the actual value was at 8 ohms (which also is confirmed by the posted graphs), the extra 1 ohm was the meter leads error.

**Audio_by_Goodwill** · August 7th, 2012, 01:10 AM

Originally Posted by aditya

.......the extra 1 ohm was the meter leads error.

One ohm for a short piece of wire would be a serious error.

**aditya** · August 7th, 2012, 05:15 AM

Originally Posted by Audio_by_Goodwill

One ohm for a short piece of wire would be a serious error.

Its more to do with the 'contact points' than the short piece of wire.

**Panomaniac** · August 7th, 2012, 09:36 AM

I didn't get a chance to measure the 515s separately, but in parallel they dip down to about 8 ohms at the lowest. I might call them nominal 20 ohms. From the twin peaks it looks like the box is tuned at about 35Hz.

Doing some work last night I may have a good passive design done. 2 caps and a coil for the low pass - 3 caps, 2 resistors (or L-Pad) and 1 coil for the high pass. I was wrong about needing big inductors (that's good) but the caps will be large. Will post details tonight.

**analog addict** · August 7th, 2012, 09:39 AM

I'm all ears....

BTW, the 515's are marked as 20 ohms....

**Panomaniac** · August 7th, 2012, 09:13 PM

OK, here you go.
LP is: 3mH-53uF-0.9mH
HP is: 11uF-2.2mH-40uF then 6R series resistor paralleled with 4uF followed by a 9R shunt.

crossover schema

That takes the horn down 6dB. According to how my active crossover was set, the horn was 10 below the woofers, but that doesn't seem right from what we measured.
If you use that Stromberg amp then you can easily roll the tweeter channel in or out. The 6dB attenuation should help with the noise of the amp. The 4uF bypass of the resistor works as a shelf to tip the top end up.

Let me know how this works out. Hope you have some caps that big. The cap on my low pass filter here is about 50uF. I think I bought a Solen or a Dayton.