I've got Altec 803B low frequency drivers and 804A high frequency drivers with 811B horns. Original crossovers are N-800E (800Hz). The idea is to use the Magnavox 8802 for high frequency and the Magnavox 175 for low frequency. Speakers are 16 ohm, maximum 30 watts and the Magnavox amps are 6 to 8 ohms, with perhaps 12 watts output from push-pull 6V6'es.
I've never done biamping before, so a couple of questions.
There are lots of active crossovers to choose from, some higher cost ones have horn time aligment, while low cost ones, like Rolls SX21 or Sampson S-xover, do not offer the horn alignment feature. I believe that the Altecs, in cabinets per the Altec "Loudspeaker Enclosures: Their Design and Use" (1962) are physically time aligned. Is that correct?
And, I read that I can wire the woofer directly, but for high frequency, use a 50uF cap in series with the horn. Is that correct?
In the mean time, I will "de-pot" the ancient N-800E crossovers, which means archeological extraction of components covered in tarry goo, then replace caps as found.
Appreciate any comments on guidance on this. Thanks!
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I replied to your similar thread over on Audiokarma.
I don't think safety caps for the HF driver are as important when active biamping with a tube amp, since you have the OPT's to protect the drivers.
When I biamped with SS amps, I did use something around 50uf. It would probably be the safe way to do things regardless of the amp choice.
I'm curious about the little box that the horn is mounted to. I would think that would cause some reflections.
Are the Altecs, in cabinets per the Altec "Loudspeaker Enclosures: Their Design and Use" (1962) are physically time aligned? Or would I need an active crossover that includes a horn aligment (time adjustment)??
When biamping, given the original 800hz crossover, is a 50uF cap in series with the horn the right value?
Behringer Super X High Precision Crossover with Limiters CX 2300 + Manual EUC | eBay
The above crossover(long discontinued and replaced with a POS) has adjustable delay on the LF channels to facilitate time alignment. It is of considerably higher build quality than today's Behringer product. For the entry fee, this is a very hard one to beat.Or would I need an active crossover that includes a horn aligment (time adjustment)??
I think there are at least 1 or 2 fellas here beside myself who have one of these units in their inventory.
Do not buy a CX-2310 with the idea that you are buying something that is the same as, or comparable to the CX-2300.
Hopefully somebody here will grab the unit i linked, very hard to find in that kind of possibly NOS condition.
Not all vegetables make good leaders.
That is a good price for the Behringer unit. I paid more than that a few years ago for a much lesser unit.
I think a safety cap is a good idea for anyone cutting their teeth with active bi-amping regardless of amplifier type or output power.I don't think safety caps for the HF driver are as important when active biamping with a tube amp, since you have the OPT's to protect the drivers.
When I biamped with SS amps, I did use something around 50uf. It would probably be the safe way to do things regardless of the amp choice.
As their experience, confidence, and knowledge grows, they can eventually remove the caps from circuit which is of course one of the "hifi" goals of active bi-amping, removing all passive electronics between the amplifier and transducers, that is.
I know you are well aware of this, Don. I posted mainly for the OP's benefit.
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And it's increasing the time interval(alignment) between the HF and LF sections.I'm curious about the little box that the horn is mounted to. I would think that would cause some reflections.
Not all vegetables make good leaders.
I think it's good to start out on the safe side as well.
So why is the horn mounted to the box? I don't remember seeing that in any factory Altec. I know they want the horn a certain distance from the front of the box to keep it aligned with the woofer, but if you move it too far back you would create other problems, like the sound coming out of the horn hitting the front edge of the cab.
I think its much better to have the horn hanging over the front of the cab. I know for HiFi this isn't as convenient, but hey, it's all in the name of good sound right?
Somebody's short path to a flush mount/flat grill would be my guess.So why is the horn mounted to the box?
Apparently, we're not all pricked by the same thorn.I think its much better to have the horn hanging over the front of the cab. I know for HiFi this isn't as convenient, but hey, it's all in the name of good sound right?
While i'm all in with you on the good sound aspect, some folks can more easily live with compromised sound to have more pleasing cosmetics. And, since Klipsch is still making the LaScala, there must be some small segment who enjoy the combination of crappy looks and crappy sound.
Put a grill on that thing, would ya................................................ .....
Not all vegetables make good leaders.
Thank you, the Protection of Compression Drivers .pdf is exactly what I need.
Per Table 2 of the document, for a 16 ohm driver, it'd be 52uF at 400 hz and 20 uF at 1000hz. Assuming a goal of crossing over at approximately 800 hz, somewhere in between, using standard values, would be 33uF.
The document also says:
Caution: Below the cutoff frequency of the capacitor, the power amplifier will be unterminated. If the power amplifier has an output transformer (typical of tube amps...), a 20 W resistor equal to ten times the compression driver impedance should be installed across the amplifier output terminals.
Compression driver impedance at 16 ohms, ten times equals a 160 ohm 20 watt resistor.
As regards the cabinets with horns in boxes as I uploaded, those are long gone and only the drivers and crossover remain. My goal is to build simple cabinets, like Valencia or Flamenco.
The only question remaining is one of time alignment when using active crossovers: can time aligment be a function of horn driver placement in cabinet design, or is time alignment for horns only achieved by using active crossovers that include this feature electronically?
Thanks for all your help on this.
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