Starting point for crossover

BigE

Member
2008-08-08 7:08 pm
Toronto
Hi folks!

I'm a TOTAL newbie when it comes to speakers.

I have a pair of ASL6115 with JBL 2226H drivers, and a pair of altec 808-8A with 511b horns.

I'd like to make a passive crossover, but have NO idea where to start. A schematic would be the best. Can I use an Altec VOT schematic even though the bass driver is not horn loaded?

Any help is very appreciated.
 

AllenB

Moderator
Paid Member
2008-10-18 11:31 am
I would want to know where to cross. Doing a little research it seems that the 511b's pattern flips below 1,200Hz. A 15" will breakup above 1,200Hz. The old 511b manual print quality was difficult to read but I estimate these drivers match at 1,200Hz.

The tweeter driver is not important in deciding where to cross when it has a horn on it, however it may be a problem if it can't keep up with the chosen frequency.
 

AllenB

Moderator
Paid Member
2008-10-18 11:31 am
What does "pattern flip" mean? I've never seen that term before.
This horn is short vertically as it is rectangular at the mouth. This shows narrow directivity at high frequencies but is unable to hold this at lower frequencies. It overtakes the horizontal directivity at some lower frequency. This has the potential to sound unusual. No problem, just cross.
Will the 15" *breakup* or *beam*? As I understand it, it will start beaming around 900 Hz, so I was hoping to go to 800 to cross it over. Does that make any sense?
It will beam, then breakup. Why avoid the beaming, that's what the horn does on purpose? Just pick the right place to cross.
 

BigE

Member
2008-08-08 7:08 pm
Toronto
It will beam, then breakup. Why avoid the beaming, that's what the horn does on purpose? Just pick the right place to cross.

Well that's true, beaming is beaming regardless of the source, and the horn *will* beam by definition.

The "right place to cross" is definitely what I am looking for. If the 15" is breaking up over 1200, then the crossover has to be under 1200 for sure -- how close to 1200 will depend on the slope of the crossover I imagine.

One approach would be to take an active crossover and test various points I suppose.
 
One approach would be to take an active crossover and test various points I suppose.

A good approach - you'll probably find a wide range of viable crossover points. Maybe, to your ears, 600Hz and 1200Hz are both fine, but in different ways.

And active eq can help a lot, too.

Note: these components are pretty well known / have had a lot of discussion.

Try a search of this and other forums on the part numbers, e.g.

Altec 808 w/ 511B's What Response? - mdeneen - High Efficiency Speaker Asylum

...which makes it seem like the altec 808-8A has lots of power handling (can cross quite low), but limited HF.
 

AllenB

Moderator
Paid Member
2008-10-18 11:31 am
If the 15" is breaking up over 1200, then the crossover has to be under 1200 for sure -- how close to 1200 will depend on the slope of the crossover I imagine.
I would change the crossover point if I discovered evidence that I should, but not for concern about what is past it.. it is all about the slope. Remember, what looks better for one driver could be worse for the other because you have almost no room for choice. In your case I would assume that the woofer slope would be set by necessity and the tweeter slope would be set to combine with it.

So I looked at the charts in your as1015 link. The peak around 1k6-1k7, take it out (-20/-30dB). The peak just over 1k is the beginning of breakup. Don't worry, it's ok to run on the edge if your slope is good. The downward slope above this peak will help your rolloff. You may have to EQ the sub 1kHz region back into line.
 

BigE

Member
2008-08-08 7:08 pm
Toronto
Thanks! I modded a dcx2496 with Jan diddens boards, and crossed over at 805 Hz with 4th order LR . It's pretty good. Especially with horns on axis. But it could use a real tweeter.

I'm looking at the beyma cp21f or cp25.

Does anyone have any suggestions? This is for home use.

Thanks in advance! I really appreciate all the help from the diyaudio crew. I hope others can benefit from these questions too.

Have a great day!
 

camarillo

Member
2008-04-12 2:11 pm
Hi folks!

I'm a TOTAL newbie when it comes to speakers.

I have a pair of ASL6115 with JBL 2226H drivers, and a pair of altec 808-8A with 511b horns.

I'd like to make a passive crossover, but have NO idea where to start. A schematic would be the best. Can I use an Altec VOT schematic even though the bass driver is not horn loaded?

Any help is very appreciated.


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