Crossovers

[GM]

Altecs solution was the 30923 slope attenuator board added to the horn circuit to tame it down for home use.
Best solution.

Personally, I believe 'best' would be driving them with a ~matching impedance SET amp to get the desired CD horn EQ , with second best being an electrical filter equivalent for a very low output impedance; though I doubt the 30923's component values designed for the more efficient 802 are going to be acceptable for the 806 due to its lower gain BW, faster HF roll off, but not aware of an 511/806 variant.

As you noted, there's still the issue of woofer/horn time alignment at least at the XO point, so for a passive solution, what's really needed is a M19 style XO that effectively has the proper CD horn EQ plus electrical offset for the longer 511 horn, but don't recall seeing one.

Seems then that for the casual DIYer, adjustable active XO/TD is the way to go with this combo.

GM

[Art J.]

Personally, I believe 'best' would be driving them with a ~matching impedance SET amp to get the desired CD horn EQ , with second best being an electrical filter equivalent for a very low output impedance; though I doubt the 30923's component values designed for the more efficient 802 are going to be acceptable for the 806 due to its lower gain BW, faster HF roll off, but not aware of an 511/806 variant.


GM

Yes, the single capacitor filter is just going to provide a general 6db slope no matter which
8 ohm driver is used. The slope probably does not match any drivers exact needs but will help.
The capacitor value will determine where the slope begins but after that, more complex designs
need to be used.

[Altec Best]

What are the exact differences WRT sound ? Between the 30904 and the 30923. I know the 30923 doesn't have the C-2 R-3 Zobel but what difference in the sound in the horn will that make.

I'll understand it much better if it can be explained in these terms.I know the 30923/30904 are attenuators for taming a High efficiency HF driver/horn for home use.

Does anyone know what the sound differences are going to be between the two attenuators 30923/30904.It says in the Altec literature that the 30904's primary function is to mate a medium efficiency woofer to a high efficiency HF driver.

http://www.lansingheritage.org/image...ome/page14.jpg

I had got some answers in a thread i started awhile back about the N1285 and the 30904 that I had received with them.Can be seen here in this thread.

http://www.hostboard.com/forums/1841508-post1.html

But I never found anything that explained what the differences were between the two attenuators just says they do the same thing so why the two variants ?

Thanks for any help on this as this has been bugging me for a bit now.Crossovers are not my strong suit.As most of you may know.

Happy Holidays !

[nikki1]

Kindly allow me to hijack my own thread and bore you guys a bit. When I was a whole lot younger and the "Hi Fi" craze first erupted I built a Klipsch cabinet, stuck a 12" University speaker in it and powered it with a Heathkit amp. Had one of those AR 2 speed belt driven turntables with a fairly good cartridge in it and I was just styling man. The point being that I'm not entirely unfamiliar with this stuff but admittedly nowhere near the level of experience and knowledge as those of you on here.

I have the curse of being an anal perfectionist. I would very much like to avoid having that lovely trait get involved with this little project of mine or I'll end up like the worst (or best depending on your point of view) of you chasing after the most realistic sound I can get. I'll want to close my eyes and be there.

So in trying to keep this at a casual DIY dweeb (ignorance really is bliss) level I gather from what you guys have posted that a N1201-8A CO would be the choice for my collection of stuff, keeping in mind that the phasing will be off, it might screw up HF rolloff and God knows what else that eludes me, as opposed to the 501-8A I'm now using.

As one who is always looking for a free lunch all I want is for someone who knows more than I to tell me "keep your 501's or get a pair of XXXX's". Puhleeze do me this small favor before I pick up my lance and go looking for windmills. After having fallen down the rabbit hole.

Heh heh heh

[Art J.]

Well Lee, keep your 501's or get a fancy digital do everything active crossover setup.
You can play control room any time you want and all changes are reversible.

John, As far as your first link goes,
The way marketers interpret things are often different than what the engineers tell them.
You see in the diagram that I purposely separated the woofer section to show
that its only a separate zobel circuit for the 411 woofer. It does not have to be used
and it has no effect on the horn circuit at all. The 30904 just has 2 circuits on 1 board as shown
in the picture. You have the 30923. The horn circuit is identical. A separate Zobel circuit
can be calculated for any other woofer and does not have to be on the same board with anything else.
A zobel is just another general 6db attempt to control the rising rate of impedance in a woofer.
Hope this helps............

[Altec Best]

Thanks Lee for allowing me to get some help in your thread.:2thumbsup:

Thank You Art,yes I think I understand your meaning, I appreciate.Sometimes I need it to be pounded into my head. I just have issues sometimes with crossovers for whatever reason.If I knew I was going to enjoy this audio hobby as much as I do, I most certainly would have taken electronics in High School instead of electrical construction !!

My motivation was I thought that I was going to be able to earn a better living, but never took into account My Love for Music & Audio! :thankU: Guys !

Happy Holidays !

[nikki1]

Thank you Art. That's all I wanted to hear.

Lee

[GM]

As one who is always looking for a free lunch all I want is for someone who knows more than I to tell me "keep your 501's.......

Fair enough. I'm a firm believer in the KISS system, so keep the 501s, I've used them in various systems off n' on since their release over 40 years ago and they work fine in a HIFI/HT app when a by-pass capacitor chosen to 'taste' is hooked across the pot to let through the extreme HF unimpeded after it's been set, i.e. the pot's attenuation combined with the by-pass cap is the casual DIYer's CD horn EQ.

GM

[nikki1]

GM- Thanks for your comment. Wiring a cap across the pot is an easy job. But the word "taste" indicates various caps will cause various changes. Would you be kind enough to briefly explain the theory behind the mod, what it does and a starting value for caps? It really helps to understand the mechanics behind it as opposed to just slapping things in there without knowing why.

You fellas are really a great source of help, and I want you to know that I appreciate it. I can feel myself getting sucked in here and it's a long winter left to go.

[GM]

You're welcome!

Correct, the only way to have just one 'right' cap value is to have a fixed design (such as an 846) used in only one specific app (such as in a specific studio) where the manufacturer has control over all aspects of the design.

Typically 0.1-1.0 uF has worked for me in 8 ohm apps, but I've seen up to 2.0 uF posted in apps where it made no sense to me, but as long as I don't have to listen to it, whatever 'floats your boat'............

Not much more to tell than I already have. A compression horn rolls off above its gain BW (~2-3 octaves) and normally it will be more efficient than a non-horn loaded bass-bin, so it's necessary to shelve it down to match if we want it to have a ~flat response (tonally balanced) at the listening position. Unfortunately, the shelving lowers the horn's entire BW, so to flatten it out to a higher roll off point we need to let the extreme HF through without being shelved down. The simple solution then is to high pass this part of the signal unattenuated with a 1st order XO (capacitor).

GM