Carver ALS IV CROSSOVER QUESTION

Now that it is posted in the proper place, I am looking for answers.
I want to try and keep the passive crossover system if possible for the IV's.

Here is the original question with a Rabbit reply. Thank you, this is a good start.

TNRabbit
Post subject: Re: Let's get this site back to talking about Carver


OK, here is some carver talk.

Has anyone here ever modified the plat IV crossover to cut at 180 to 200Hz? Is this a good idea? Will the plat IV subs handle the frequencies to 200 well? Will it upset the balance of the sweet and juicy like these nutz. sound these speakers produce?
I am prepared to do the surgery to extend the longevity of the ribbons. I would also be open to a mod for a bi amp option. Pics and plans would be appreciated. I am picking up a set of Plat IV crossovers this weekend for the potential mod process.

--Clearview actually made active xovers to specifically replace the Carver passive xovers, and if memory serves they DID cross over at 200 hz to take some pressure off the ribbons. SO, I guess the woofers would be up to handling the 200 hz signals....dunno. Maybe James can say for sure....


Also, has anyone ever modded a set of AL-III's to use a sealed sub enclosure? Any crossover changes? What driver was used? What is the volume of the cabinet?

--I've talked about & considered this, but was afraid I'd mess up the good job Bob did with them...if you were actively bi-amping & had a sinewave generator & decibel meter, you could probably make it happen. I use Infinity Perfect 10.1 (automobile apps) subs on my AL-IIIs and love them. The box volume on the AL-IIIs is APPROXIMATELY 1.8 cubic feet.




THERE IS NOTHING WRONG WITH OPERA !!! I listen to it at the shop I even have some on LP.--There are a couple of Operas I like to listen to....

See my reply over where you first posted the question.

Here is what Bill wrote in case that other thread dies:

Beemers has a good question, and I've looked at the schematic. What I'd do is go directly to the woofers (i.e., bypass that part of the circuit, which is pretty easy), and use the existing crossover on the ribbons (which is fairly complex), and feed it only > 200Hz. I think the woofers can handle up to 200Hz, because that's where the Clearview crossed.

As for the AL-IIIs, that's a question I'd like to know the answer to, too (the interior volume of the box). Making that an acoustic suspension cabinet (you'd probably use a lot of packing foam) would be interesting.

As Bob has oft said: "why don't we TRY it!?!"

That sounds like a good plan to me.

If you were going to change the internals of the crossover, it's beyond my ability to do the calculations, because the crossover is odd. It's close to a Butterworth, but not really (perhaps why they call it a quasi-Butterworth. It's third order.

Platinum0001.JPG (230.75 KiB) Viewed 575 times

If you were to bi-amp them, the wire marked "RED" becomes your + terminal, and the wiper on RP3 becomes your - terminal (you'd cut the wire just after L6. You can see L6, L7 and C7+C9 make a third order low pass filter, presumably passing frequencies below 150Hz (could be 100Hz) to the woofers. I tried several Butterworth calculators assuming the speaker array is 4 ohms (I think the woofers are 16 ohms apiece, all in parallel). I tried with 5R3, too, taking into account the resistance of the coils, to no avail.

As you can see, the ribbon section is quite complex, and I don't have the skill to figure it out.

Bill do you have one for the original plats not the MK IV? Eddie!

Yes. It's a lot simpler. The woofer crossover is a simple second order design.

Platinum.jpg (110.96 KiB) Viewed 551 times

Thanks Bill!

I did a little more investigation of that circuit. If you replace C7 and C9, which together form a 300µF capacitor with 100µF, there is equal vlotage (almost) in the legs of the crossover at 200Hz (i.e., that's where it's crossing). The was the crossover is now set up, there is a large overlap between the ribbon and the woofers.