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Posted by KS on
08-06-2010
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fiogf49gjkf0d OK this is with a digital XO, I'm wondering whether most of you would bother to low pass a 800-10k Radian mid in a 425hz Azurahorn, which hands over to a 10K+ tweeter?
I've read that playing too high for a particular horn has some sort of dissadvantage, to do with too small waves bouncing around inside the horn, but I must admit to not understanding this theory.
Thanks for any input,
KS
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Posted by Romy the Cat on
08-06-2010
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fiogf49gjkf0d Yes, KS, you heard correctly. Since you use digital XO you shall know that one of the main principles of digital processing is quantization. Quantization is dividing of a signal flow upon minute discrete symbols. Each quanta symbol of quantization is approximately 0.03mm in wavelength representation. You use 425Hz Azurahorn. If you divide the 425Hz by 0.03mm then you will have 14166.666666666666666666666666667. Just looking at this number you can clearly recognize that it has a Sigh of Devil number, the 666 that is a big no-no in horn making. There are a few ways to deal with it. You need to degauss you playback from Devil’s touch. To do so you need to lit 7 candles, located on the perimeter of you playback and then you need to sacrifice 2 chickens. Alternately you can scratch cars of any 5 republicans you know. All methods will work and then you can cross your driver in any way you wish…
The Cat
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Posted by KS on
08-07-2010
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fiogf49gjkf0d Unfortunately I'd have a hard time finding both chickens and republicans where I live.
If I read you correct, no sense in low-passing midrange, just let it play open?
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Posted by Romy the Cat on
08-07-2010
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fiogf49gjkf0d KS,
I never understood those type of questions. A channel need to be crossed not according to any theoretical justifications but where it would let a given driver in given enclosure to perform it’s best. You need to evaluate what you neighboring channels do and where one channel become to have disadvantage in respect to another. There are many many other factors of cause but what is important is that crossover point is a reflection you result not wise-versa. In some cases I just do not know what the crossover point is – and this is normal. I have written about is a lot in past, seek if you are interested. The question “shall you pass here or there is the same as someone would ask if he need to use third gear while driving his car. The answer would be “perhaps” but it is absolutely up to you where, how and for which purpose to engage the third gear…
The Cat
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Posted by KS on
08-07-2010
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fiogf49gjkf0d There might be 'rule of thumb' here, but let me explain a bit better with some specifics.
I'll have a Radian CD in a 425hz horn playing 800hz up to where it starts to roll off naturally at 6db at, say, 10K. And a similar Radian taking over from there in a smaller horn. (I've got a lot off leeway regarding XO points, and I'm not worried about where exactly they'll be at this stage)
But I read somewhere that high frequencies can in some way be 'problematic' when they become too high for the particular horn they are in. So I'm wondering if this is true, if there might be ever be any good sense in rolling off a mid freq horn BEFORE its natural roll off (lets pretend 7k). For example with full-range drivers, they might measure flat up to 15k on a smoothed graph but then listen you find you can hear cone breakup in the upper octaves, which you might not have guessed at before hand)
The simple thing would of course be to listen and see, but I'm in a fix wanting to run a 4-way system with a 3-way digital XO, so Im wondering before I buy the necessary amps etc, whether I could consolidate the uppper most two horn as one channel, i.e digital high-pass at 800hz then a passive XO on the tweeter.
So, if anyone here has ever found gains by cutting off the top end of their midrange before its natural roll, just say 'Yes' and I shall then investigate an active XO and buy an extra amp to allow for experimenting with this myself, with my particular drivers and horns.
Hope that makes sense, thanks anyone for input.
K.
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Posted by Romy the Cat on
08-07-2010
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fiogf49gjkf0d
I see, this is very different question then you initially posted.
Ironically the subject was discussed years back what I was fighting with S2’s “fuzziness” at very top.
I still do not feel that there are any 'rule of thumb' in it, there are rather many “depends”. If your MF driver in your particular horn has problematic top end and you would like a bit roll it of then there are many options to consider BEFORE bringing a new amplification channel for HF. Here are a few options:
1. Use a deeper horn
2. Use a horn that has higher “constant directivity” characteristic
3. Introduce a very mild serial inductance to MF driver. (HF will need own amplification)
4. Mild application of damper on the surface of the MF defrag (like aquapluss)
5. Changing reflective characteristics of back chamber on MF driver
6. Lower the output stage that drives MF loading (the more effective and proper in my view)
7. Use HF channel in a way the it will mask out the upper MF driver
8. Reduce effectiveness of phase plug Rgs, the Cat
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Posted by KS on
08-08-2010
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fiogf49gjkf0d Thats the kind of stuff I was hoping for. I appreciate the help with this, there seems to be a scarcity of horn related discussion on the web and its proving hard to learn the ropes.
One other unrelated question that could save me a lot of trial and error - If time and phase alignment was not an issue (imagine you were forced at gunpoint to use a digital XO that could compensate for this), would it be advantageous to align the mouths of all horns rather than the drivers? I was looking a building something like a Macondo frame, but I'm wondering the price one pays as far as HF from the tweeter horn smacking into the back of the horns above and bellow? I see you use a fairy directive horn to try squeeze the HF through the narrow gap, but I'll likely have a round tractrix back there so was wondering if I should move the tweeter forward and time align digitally, having that option on hand.
cheers
K.S
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Posted by Romy the Cat on
08-08-2010
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fiogf49gjkf0d  KS wrote: | Thats the kind of stuff I was hoping for. I appreciate the help with this, there seems to be a scarcity of horn related discussion on the web and its proving hard to learn the ropes.
One other unrelated question that could save me a lot of trial and error - If time and phase alignment was not an issue (imagine you were forced at gunpoint to use a digital XO that could compensate for this), would it be advantageous to align the mouths of all horns rather than the drivers? I was looking a building something like a Macondo frame, but I'm wondering the price one pays as far as HF from the tweeter horn smacking into the back of the horns above and bellow? I see you use a fairy directive horn to try squeeze the HF through the narrow gap, but I'll likely have a round tractrix back there so was wondering if I should move the tweeter forward and time align digitally, having that option on hand. |
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K.S.
replying to you I would like you to know that I religiously do not support digital crossovers, practically with horns. You my read about it elsewhere at the site. About HF and MF time alignment. If you chose is to stay with digital crossover then it shall not be a subject as the digital crossover will set for you any delay at any channel. You do not need to align horns or drivers but rather arrival time – digital can do delays problem-free. Macondo frame is truly shall not be a guidance for you as Macondo is in a way unique configuration had objectives to align the channels naturally. If I were not care about time alignment then it might be a different tweeter, deferent midbass horn and many other things were different. In your case, using digital crossover you are out of wood and free from any Macondo Acxioms – you can do pretty much any configuration you wish.
A few words I would like to say about your question from your previous post. When you refer to the “people on line say” then it is a very idiosyncratic reference. I personally do not know your Radian driver but judging from what I see people do only I do not think that the driver has HF break up. You see, the people on-line are mostly Morons. A very typical application is to use transiently -challenged compression drivers and then to power then with overly-idle amplifiers. The output stage of you amp see the driver’s impedance and the ratio of you SET OPT will indicated how the output tube is loaded. If you idle the tube too much then the driver cone will not be damped properly electrically (among many other reasons) and the driver will have tendency to sound overly brisk. If you load the output tube too much then it will have problem with transients. Again, I do not know your specific Radian driver but most likely you and the people who complain about it’s top end do drive this Radian with insufficiently loaded amp. You might very simply to test it by shunting your Radian with a power resistor or 16R-4R. By doing this you will vernally load your amp harder. If you recognize that the HF problem of you MF driver will be gone with the resistor (I will give you 95% that it will be the case) then you do not need to listen any people online and just to change the ration of you OPT.
The Cat
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