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

**analog addict** · August 2nd, 2012, 06:40 PM

Originally Posted by Panomaniac

Cool! I like the new arrangement. I wonder if that thing should go on its side?

Hard to ever put wings on it if it's lying on it's side.....

**analog addict** · August 5th, 2012, 11:08 PM

Here's some of Panomaniac's work....

and here's a hashed together working unit to use while I await the results of his work...

**Panomaniac** · August 6th, 2012, 11:00 AM

We had a great time last night, A.A. is always a great host and everyone had a blast. We did have some trouble concentrating on the audio, as Olympic Beach Volleyball was on the TV (sound off). :cool
I think we came up with a pretty good crossover by measurement and by ear. It was nice to have some trained listeners there to verify the sound of things. The crossover turned out to be 3rd order electrical with the horn reversed (IIRC). Acoustically the crossover point is circa 770Hz, but I don't remember the electrical points. It's what sounded best.
I'll get some measurement graphs and other info up ASAP - tonight I hope.

EDIT: Oh yeah, the traces you see above are impedance plots for the dual woofers and the horn+driver.

**Altec Best** · August 6th, 2012, 12:53 PM

Wish I lived closer ! Sounds like you guys had a great time !

**Panomaniac** · August 6th, 2012, 09:11 PM

OK, here are some pretty graphs. You'll see the 288 on 1005 impedance curve in green - the dual 515s are in blue.
What would you call their nominal impedance?
impedance center

On the second graph we see the drivers' measured at the listening position after crossover. Green is the combined response. Don't know why the bass looks so bumpy, might have been where the mic was placed. The crossovers ended up being 3rd order at 600Hz for the low pass, 3rd order 750Hz for high pass. Reverse phase.
final center

I'll work on this some to come up with the values for a passive crossover given the impedance curves. Will post results here.

EDIT: Images updated for better size

**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.