Crossover component values

[Guest echesky]

I realize there are a lot of variables that changed in the Advent crossovers over time. I found the Large Utility Speaker's crossover design in the library area here. I have New Large Advent drivers and wish to construct the original crossover used with them. I know the woofer coil needs to be .3mH to go back to original. The symbol on the schematic for L1 does not give a value...and what exactly is L1? Any other changes in values?

[Pete B]

>I realize there are a lot of variables that changed in the

>Advent crossovers over time. I found the Large Utility

>Speaker's crossover design in the library area here. I have

>New Large Advent drivers and wish to construct the original

>crossover used with them. I know the woofer coil needs to be

>.3mH to go back to original. The symbol on the schematic for

>L1 does not give a value...and what exactly is L1? Any other

>changes in values?

If you building New Large Advents, then this is the correct original crossover:

http://www.classicspeakerpages.net/dc/dcbo...1269&page=#1445

[Guest echesky]

THANK YOU!! ...many times over!

I will simply opt to use a .3mH Jantzen 18 ga. air-core inductor, a 6.2uF and 6.8uF Solen cap in parallel and use a 2.5 ohm 12 watt Mills resistor. This will achieve exactly what I am looking for...the 'normal' position...without all of the extra wiring/components, etc.

Would you advise using a polyswitch or some other protective measure on the tweeter?

[Pete B]

>THANK YOU!! ...many times over!

>

>I will simply opt to use a .3mH Jantzen 18 ga. air-core

>inductor, a 6.2uF and 6.8uF Solen cap in parallel and use a

>2.5 ohm 12 watt Mills resistor. This will achieve exactly

>what I am looking for...the 'normal' position...without all of

>the extra wiring/components, etc.

>

>Would you advise using a polyswitch or some other protective

>measure on the tweeter?

Your welcome,

Air core is good, however that 18 ga. has lower resistance than the original which will tighten up the bass very slightly. The 20 ga. Jantzen is a perfect match if you want to duplicate the original. And of course the 15 ga will provide even more damping of the fundamental resonance.

The 1.5 ohm is shorted in the "normal" position so it would be 1 ohm to duplicate the original with the original cap. Note that I measured an ESR of about .6 ohms for the cap, so you'd want to add about .5 ohms in addition to the 1 ohm, if you use a poly cap which has very low ESR:

http://www.classicspeakerpages.net/dc/dcbo...ing_type=search

You might be interested in this mod:

http://www.classicspeakerpages.net/dc/dcbo...ing_type=search

You might want to try higher resistance values to the tweeter if you don't use the above mod, as they're rather forward sounding. The Advent/1 uses the same drivers in a smaller box without a switch and has a 3 ohm resistor to the tweeter. The crossover is otherwise the same.

[Guest echesky]

Pete,

Thanks again for your input.

I'm not trying to re-invent the wheel here...just make it roll a bit better possibly. I would prefer to keeping mods on the speaker only so I'll pass on your aditional mod circuit for now.

OK...a 20ga. coil would be like the orginal woofer coil. The 18 guage you say 'will tighten up the bass very slightly' and the 15 guage 'will provide even more damping of the fundamental resonance'. I'm a bit confused/slow...stay with the 20 guage for the best sound...or go to the 15 guage for the best sound?

Is there any reason to not change the cap value slightly and put a coil in parallel with the tweeeter to make it a 12dB roll-off...possibly protect it a bit? Or, would you suggest using another form of over-power protection for the tweeter? ...or just stay with the 6dB x-over and maintain volume control?

So...I'm at a .3mH coil (and the best guage is?), 13uF of capacitor and a 1.5 ohm resistor...to build back to original 'normal' using a poly cap. I don't 'get' what you mean by 'forward' sounding....not to be dense...but please explain.

[Pete B]

This is a situation where my "best" may not be the same as your "best". I disagree with much that's written about Large Advents (LA), but one thing they give us is strong bass down to, and somewhat below, Fc or about 42 Hz. Qtc is about .8 to .9 which gives them strong output at Fc, perhaps too much in some rooms with some source material. A lower resistance inductor will lower Qtc and the output at Fc. If you liked what you heard from the LAs go with the 20 ga.

It is interesting that the system Fc was chosen to match the lowest note on a standard four string bass guitar, E1 or 41.2 Hz. This is a good compromise for much of the source material available, however the lowest note on a standard 88 key grand piano is A0 or 27.5 Hz. I prefer systems with deeper extension.

http://www.contrabass.com/pages/frequency.html

The mod is impressive, too bad your passing on it.

Yes there is a reason not to change the tweeter XO that being if it is correct originally with a first order network on the tweeter, then it will be wrong if you only change the tweeter to 2nd order. A crossover redesign is not a minor mod.

There is a way to retain the first order XO response near the XO point, but provide faster rolloff below the XO point. Put a 2mH inductor across the tweeter. An independent fuse on the tweeter could also be used. Be sure to have enough power, 75 to 150W is not unreasonable. Double Advents are a good way to go if you often need higher levels.

Forward, you can search the forum to see comments about this.

Pete B.

>Pete,

>

>Thanks again for your input.

>

>I'm not trying to re-invent the wheel here...just make it roll

>a bit better possibly. I would prefer to keeping mods on the

>speaker only so I'll pass on your aditional mod circuit for

>now.

>

>OK...a 20ga. coil would be like the orginal woofer coil. The

>18 guage you say 'will tighten up the bass very slightly' and

>the 15 guage 'will provide even more damping of the

>fundamental resonance'. I'm a bit confused/slow...stay with

>the 20 guage for the best sound...or go to the 15 guage for

>the best sound?

>

>Is there any reason to not change the cap value slightly and

>put a coil in parallel with the tweeeter to make it a 12dB

>roll-off...possibly protect it a bit? Or, would you suggest

>using another form of over-power protection for the tweeter?

>...or just stay with the 6dB x-over and maintain volume

>control?

>

>So...I'm at a .3mH coil (and the best guage is?), 13uF of

>capacitor and a 1.5 ohm resistor...to build back to original

>'normal' using a poly cap. I don't 'get' what you mean by

>'forward' sounding....not to be dense...but please explain.