| Crossover Question about building line arrays [message #60892] |
Wed, 16 September 2009 16:45  |
Wendall Evans
Messages: 5
Registered: September 2009
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Esquire |
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Since there are so many speakers involved does this give more crossover options?
Many people have different conceptions of where the crossover points should be handled in a line array. Also I've heard some people say that passive crossovers for line arrays are just too hard, and that people should only be thinking about electronic crossovers. What options are there for that and how expensive is that?
Sorry for all the questions but this seems to be a place where they might be answered by people who have actually built a line array.
TIA,
Wendall
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| Re: Crossover Question about building line arrays [message #60893 is a reply to message #60892] |
Wed, 16 September 2009 18:20  |
AudioFred
Messages: 377
Registered: May 2009
Location: Houston
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Illuminati (1st Degree) |
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Having more drivers doesn't give you any more flexibility in line array crossover design. In fact, it's harder to get it right with a line array because of the effects of driver size and spacing with multiple drivers. There are more variables, and a modeled crossover for a line array is more likely to need tweaking.
Active crossovers solve lots of problems, but they can be very expensive if you're building a high end line array for use with high end audio equipment. You could insert a $300 Behringer crossover betwen a $5K preamp and $10K of amplification, but that doesn't make much sense. However, if you're building a budget array and are willing to buy used pro audio equipment the cost can be very reasonable, and the sound quality of brands like Ashley, Rane, etc is surprisingly good.
Eric, this is your area of expertise, so please chime in here.
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| Re: Crossover Question about building line arrays [message #60920 is a reply to message #60892] |
Fri, 18 September 2009 17:21 |
Marlboro
Messages: 403
Registered: May 2009
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Illuminati (1st Degree) |
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| Wendall Evans wrote on Wed, 16 September 2009 16:45 | Since there are so many speakers involved does this give more crossover options?
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I'm going to answer your questions one at a time and leave a space in between for your answer.
I know what Fred is saying, but I disagree slightly.
One of my design goals(and for a low cost line array you need design goals) were to avoid a crossover in the 200-3000hz region. This really means that I was looking for a midrange speaker to handle at least 1/2 octave above and 1/2 octave below. This means the FR had to be more like 150 to 4500.
This is hard to find a good speaker in this range normally, if you need a cheap one, its worse, if you need a cheap one to play loud, forget about it because of the distortion involved.
And so, IN MY OPINION, its the distortion that is the big concern. Its hard for the human ear to differentiate much less that +/- 5db in a freq response, and even less than that in certain areas of the FR.
But with a line array that has 16 of these "cheap ones" per channel, each one will only be playing .0625 of the music.
So if you want such a wide range of FR for the speaker, you are way more likely to get acceptable distortion when each one only plays 6.35% of the total music per channel. And you can do it even with some very inexpensive speakers.
What do you think?
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| Re: Crossover Question about building line arrays [message #60925 is a reply to message #60922] |
Sat, 19 September 2009 11:13 |
Marlboro
Messages: 403
Registered: May 2009
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Illuminati (1st Degree) |
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| Wendall Evans wrote on Fri, 18 September 2009 19:03 | Why did you want the midrange to be between 200-3000 and have no crossover in that range? Lots of people use crossovers around 500-1600.
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When using electronic crossovers this is less significant. But here is the reason:
"It is not at all uncommon to see systems where the crossover frequency is set right in the middle of what I call the "intelligence band". This is the range of frequencies from 300Hz to 3600Hz, and is extremely important from a psycho-acoustic point of view.
"It is no accident that this is the range of the telephone system (and has been for many years). If we are only to hear a limited range, then this band of frequencies is by far the most important. Just from this we can recognise a person's voice, which musical instrument is being played (even bass instruments!), and - more importantly - what is being said. It contains nearly all the "intelligence" of the sound, which is to say that if this band is "corrupted", intelligibility is greatly reduced.
"So why do speaker manufacturers insist on placing their crossover frequencies within this band of frequencies? The public address (PA) systems used by many rock bands are a case in point - how often does one find that the vocals are completely unintelligible? Mind you, it may also be the case that the band's lyrics just don't make sense, but that's another story altogether.
"Often this occurs because the system is so loud that the amplifiers are clipping badly, but even at lower levels it is quite common. Place a common-or-garden crossover filter right in the middle of the "intelligence band" and this is exactly what will (and does) happen. With phase aberrations and cancellations, this most important frequency range becomes muddied and indistinct causing loss of intelligibility - not only on voice, but instruments as well.
"The effect is also noticeable with some hi-fi speaker systems, except that it usually less pronounced, and it is far less likely that the amplifier will be driven to clipping. Reviewers will often say of a speaker that the vocals seem veiled, or that there is noticeable colouration of either male or female vocals. These effects are often caused by the effects of phase shift around the crossover frequency, coupled with the fact that the crossover frequency falls right in the middle of the intelligence band.
"Should a crossover be unavoidable in this region - due (for example) to available loudspeaker drivers - then the manufacturer must go to great lengths to ensure that "artifacts" created by the crossover are not audible. This often causes greater problems with amplifier loading at the crossover frequency, since impedance dips seem a common problem with many speakers. It will be found that these almost invariably occur at the crossover frequency. "
Read the whole article at:
http://sound.westhost.com
Rod Elliot given permission for posting pieces of his articles but only the home website can be posted as the source. Search through the site for articles, and look for bi-amping, and then search for "intelligence band" and you will find the context this was taken from.
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| Re: Crossover Question about building line arrays [message #60941 is a reply to message #60940] |
Mon, 21 September 2009 09:25 |
selahaudio
Messages: 56
Registered: September 2009
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Baron |
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| AudioFred wrote on Mon, 21 September 2009 08:44 | | selahaudio wrote on Mon, 21 September 2009 08:21 |
I advise against a non-DSP crossover because they typically only have symmetrical slopes and little ability to contour the response for baffle step and driver anomalies.
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Unfortunately this leaves one with the choice of a DEQX, which is as good as it gets, but costs upward for $5K new, or a Behringer DCX-2496, which costs only $300, but is mass market quality and not something I would place between a high end pre and amps driving a good pair of speakers.
What do you think of the Behringer used with a "budget" line array, for example one using sixteen sealed Tang Band W3-1053SC 3" woofers and a tweeter array of Dayton 3/4" neo domes or PT2 planars? It seems to me that entry level electronics would sound no better or worse than the Behringer, and actively crossing this array with the Behringer might sound better than a passive crossover.
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=248-669
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=264-880
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There are some options. DBX has a DSP crossover (DriveRack PA+)for $500. Built better than the Behringer and also has parametric EQ for baffle step and response contouring. I also have access to a 3-way DSP crossover that includes ICE amps. It's more expensive, but for $2,000 you have six amp channels and a DSP crossover.
The AuraSound NSW1 is a better choice than the Dayton because it will cross lower; however, it is beyond the budget for many builders. The PT2 also crosses lower than the Dayton and would make a good match with the TB woofer. The Dayton 3/4" has a Fs=2K which means a crossover point of at least 3.5K-4K and that's not going to work well in an array with 3" woofers.
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