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Author Topic: tweeter crossover question  (Read 14213 times)

David Morison

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Re: tweeter crossover question
« Reply #20 on: January 05, 2013, 08:46:52 AM »

It's a very small line array, LOL. 1 box on each side, 2x12" mids and 3 horns, with the horns as close as physically possible. Yes, I could get a more coherent sound and better HF extension if I spent another $600 on better drivers and devised some kind of multiple-entry horn, but I wasn't up to fabricating something like that.

Sticking 3 90ox40o horns one above the other does not a line array make, especially when it results in the drivers having a minimum centre-to centre spacing of at least 200mm. Those drivers will stop behaving in any kind of coherently coupled manner above a few hundred Hz (assuming the 1/4WL coupling requirement for maximum coherency), and you're probably not even running them that low in the first place.

You would be far better replacing all three with one higher quality driver & horn, and would almost certainly find that your whole HF (including the top octave where you perceive your biggest problems at present) sound improves.

Speak to Jack Arnott of Assistance Audio who sometimes posts here (assuming you're in the US) about getting some BMS drivers - he'll be able to advise you on the most appropriate models for your usage. Once you sell off your current 6 drivers and horns, you won't find them too expensive.

HTH,
David.
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Fenris Wulf

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Re: tweeter crossover question
« Reply #21 on: January 05, 2013, 01:47:16 PM »

OK, after some searching I found various 1" compression drivers with 200w power handling. That would do the job. The system has to produce high SPL outdoors and be fairly idiot-proof.

The system is small enough that the max. path length difference is about half an inch, so the coherency isn't as bad as you say, but it's not great either.
« Last Edit: January 05, 2013, 01:51:56 PM by Fenris Wulf »
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Ivan Beaver

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Re: tweeter crossover question
« Reply #22 on: January 05, 2013, 02:04:08 PM »

OK, after some searching I found various 1" compression drivers with 200w power handling. That would do the job. The system has to produce high SPL outdoors and be fairly idiot-proof.

The system is small enough that the max. path length difference is about half an inch, so the coherency isn't as bad as you say, but it's not great either.
You need to STOP thinking about just power handling.  Start to think about REAL sensitivity (not just the numbers on the spec sheet) and REAL frequency response.  THOSE can make MUCH MUCH of a difference than any "power specs".

Just look at the MEASURED data of the devices-NOT the simple numbers on the front of basic spec sheet.

How do you figure you have the devices within 1/2" of each other?  Yes at some freq the different drivers will sum together and make it louder-but at other freq they will cancel each other out-resulting is a less clear sound-which sounds like one of your basic problems.

What is "high SPL"?  A or C weighted" fast or slow response?  at what distance?

Until; THOSE questions are answered-you cannot even start to think about what drivers to use.

And once you start doping the math-you should quickly realize that a simple wattage number is not going to give you the answer you want.  Unless the sensitivity spec is also not representative of the overall pass band level. 

I am not aware of any horn driver that is rated at 200 watts continuous.  So are you using the program or peak wattage in your "calculations"?

It may be just me-but I think there is a good bit of basic understanding that is being missed here.  And more of "just throw drivers in a box and turn it up" type of thinking.
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Ivan Beaver
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Fenris Wulf

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Re: tweeter crossover question
« Reply #23 on: January 05, 2013, 04:50:52 PM »

Whoops, I got fooled by a spec sheet that failed to specify RMS or peak. It looks like 80 watts rms is about the max for a 1" driver. A single driver isn't going to do it, the system needs to be bulletproof even if it's abused.

The distance between drivers is about 8", but the path length difference (from drivers to ears) is about half an inch.

Sorry I wasn't forthcoming with the system details. The system is too large for a single driver and too small for a proper line source, so I may have to live with the compromised sound. A properly designed multiple-entry horn system is out of our budget and it isn't a task for a DIY'er. I could try a passive crossover to split the horns into different frequency ranges, but it may cause more problems than it solves.
« Last Edit: January 05, 2013, 06:06:25 PM by Fenris Wulf »
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Luke Geis

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Re: tweeter crossover question
« Reply #24 on: January 05, 2013, 11:51:07 PM »

Your typical CD horn lens will never work as a line array element, EVER...... Another thing to keep in mind is that just because you take a conventional speaker and place it sideways, does not make it a line array element. The general consensus is that it takes a minimum of four line array elements ( real ones ) to even start to acquire the benefits in which a true line array will operate.

Point source elements are different in that they have very small coverage patterns that the entire bandwidth emitted from them will follow. When you take several of these point source elements and splay them together, you get a larger coverage area with minimal interaction between boxes.

Your speaker design may be a gem if you can keep it simple enough. You may be able to fix most of your problems with some after crossover EQ and or perhaps phase alignment? Sound emitted from a conventional CD horn comes out in rounded fashion almost as if you were trying to blow a bubble with it. The phase plug that is part of many of the drivers is there to reduce that effect. But the stark reality is that the sound that travels down the side of the horn travels a longer distance than the one beaming straight out. That is why so much RND in horn lens in line array elements is being done. In general the goal is to try and make two or three drivers combine into one while making it so that all paths in which sound travel are equidistant to each other. The second part of that goal is making it so that box to box the transition is seamless and in essence creates one very large horn when all the boxes combine.

We know now that your box is sideways, has two 12" speakers and has what sounds to be a horn on each side of the box? If you have two horns in the box try turning one off and see if it helps? It may or may not if that is in fact the case. As for the volume that can be created with said driver and horn I would rely on the specs to get an idea and apply some simple math. If the driver is rated for 80 watts and has a sensitivity of 103db @ 1W-1M, it may only actually produce at best 122db @ 1M at full rated power ( this is at best )? This may be loud enough for you? Just because there are two of them does not mean you will achieve coupling at all frequencies. This may be why you have the sound you have? I would not add more to it and complicate the issue. I would see what I could do with what I already have.....
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Fenris Wulf

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Re: tweeter crossover question
« Reply #25 on: January 06, 2013, 12:33:30 PM »

Each side is a square box, 2x12" woofers in a vertical line, 3x1" horn drivers with CD horns in a vertical line. Technically a "line source," but not a proper line array. 6x15" subwoofer in the middle. Aside from the top octave, it's surprisingly good sounding for a system built quickly and cheaply and tuned by ear.

Maybe a gigantic ribbon tweeter? You can DIY electrostatic drivers from scratch, but with the high-voltage polarization, I'd hesitate to use them in a live setting.
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Ivan Beaver

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Re: tweeter crossover question
« Reply #26 on: January 06, 2013, 12:39:24 PM »

Each side is a square box, 2x12" woofers in a vertical line, 3x1" horn drivers with CD horns in a vertical line. Technically a "line source," but not a proper line array. 6x15" subwoofer in the middle. Aside from the top octave, it's surprisingly good sounding for a system built quickly and cheaply and tuned by ear.

Maybe a gigantic ribbon tweeter? You can DIY electrostatic drivers from scratch, but with the high-voltage polarization, I'd hesitate to use them in a live setting.
How do you figure that "technically" it is a line source?

The HF devices are to far apart-and depending on how high your MF/HF crossover point is-the 12" drivers are also to far apart.

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Ivan Beaver
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Luke Geis

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Re: tweeter crossover question
« Reply #27 on: January 06, 2013, 04:04:46 PM »

" Your typical CD horn lens will never work as a line array element, EVER........"

Add that to include line source as well........

You would have better luck creating a long run of ribbon drivers and butting them together. Be prepared to trim the ends to get the elements as close as possible. Your typical CD horn no matter how small or close it is to other similar ones, do not work very well together. The only way to couple multiple drivers, is to have a single wave guide that collects all the drivers and distributes them evenly out of an aperture that creates equal paths for them all.
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Fenris Wulf

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Re: tweeter crossover question
« Reply #28 on: January 06, 2013, 08:31:12 PM »

I've been looking into ribbon drivers. Glad to know they can be trimmed.

So, any leads on a good multi-entry waveguide design? I can knock something together that will be equal-path as you say, but I know there's going to be issues with weird cancellations inside the horn.
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Ivan Beaver

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Re: tweeter crossover question
« Reply #29 on: January 06, 2013, 08:43:19 PM »

I've been looking into ribbon drivers. Glad to know they can be trimmed.

So, any leads on a good multi-entry waveguide design? I can knock something together that will be equal-path as you say, but I know there's going to be issues with weird cancellations inside the horn.
2 things.  You MUST pay attention to the sensitivity of whatever driver you use-NOT just the wattage.  You can get into real trouble real quick if you don't.

There is a lot more to a multi waveguide than just "knocking it together".  How you get the drivers to sum together with minimal interference/cancellations is what the real designers spend a lot of time/effort trying to do.

I doubt there are many "plans" out there.  And if you did find plans-building it will not be easy.
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A complex question is easily answered by a simple-easy to understand WRONG answer!

Ivan Beaver
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ProSoundWeb Community

Re: tweeter crossover question
« Reply #29 on: January 06, 2013, 08:43:19 PM »


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