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Author Topic: News To Me!!!  (Read 4629 times)

Mr.Nightro

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News To Me!!!
« on: August 29, 2004, 04:48:05 am »

I happened to find myself helping out a friend set up his system for his birthday party at a local club this evening when I was given a little information that smacks against the grain of logic I am used to using. First are we all in agreement that mixing different models of horn subs isn't generally a good idea, especially if you aren't applying the appropriate time delays? I was placing the subs for the night (4 Cewrin Vega folded horns) in a center cluster (system being used for DJ playback) when I noticed that one of the folded horns where different from the other three (looked like a knock off with the removable plate for loading the speaker in a totally different location, & no Cerwin Vega handles or 1/4" speaker jack plate). Not knowing if the length of the horn was the same as the other three I decided to leave this sub out of the cluster (I was too far from home to lend him one of the Cerwin Vegas I have in my collection of speakers) & run just the three in a cluster ( unfortunately it wasn't my system & my friend doesn't have the equipment or know anything about delaying his tops to these subs). I place his two full range tops on tripods (a pair of Peavey SP 2X) then run all the snake runs back to the amps & fire up the system that I must admit for the size of the hall was sounding really good given the situation at hand (lack of top end delay, high pass filter, EQ or an adjustable crossover since all he had was a Peavey Kosmos as his lone processor outside of my no longer needed Rane compressor that I just gave to him this evening as a gift since I have a DBX Drive Rack). Now here is where things get interesting (hmmmm  Confused ) a guy who was sitting at the bar watching me set up the system for the evening walks on over to me & introduces himself as a sound tech for some company or other (I have never heard of him or his company before & this is a SMALL community) that does audio installations for small churches, bars etc. he then proceeds to lecture me on the lack of proper equipment to process this system (as though I didn't already know this) so before I could explain myself he went on to tell me that I should of used the  sub that was different from the rest (even though I explained to him the reason behind my leaving it out) cause as he put it "Bass is bass" (yeeaahhh  Rolling Eyes ) & if I was going to leave it out of the cluster I should only run two of the subs instead of the three cause "When ever you run subs in odd numbers the odd number would cancel out the others & you will end up with less bass rather then more"  Laughing . So by now I am trying to keep a straight face as I tell him this is news to me as he goes on to (edumakate) me further to tell me that the human ear can't distinguish between the sum of three subs compared to two subs in a cluster because of this reason. OKay!!!! So tell me what book did I forget to read to be able to be blessed with this level of knowledge?, or maybe I should just find out what it was he was drinking? But for what it's worth he seemed to like the Peavey tops cause he said they are top of the line & "ALL" the pros use them as their "A" rigs when they plan to charge top dollar & that I would of been better off using the Peavey SP subcompact 18X subs or the SP 118 instead of the Cerwin Vega folded horns cause their design produce greater subs then a folded horn could........ I guess I have had it wrong all these years, what could of I been thinking of... SILLY ME!  
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Mac Kerr

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Re: News To Me!!!
« Reply #1 on: August 29, 2004, 09:50:27 am »

I guess you have to consider the source. I know I always appreciate guidance from a guy at the bar. Laughing  You probably made the right decision on leaving out the mismatched sub. I wouldn't worry about timing the subs to the tops IF you are using a center cluster of subs, and left and right mains. Because of the separate locations of the subs and mains you could only align them in time for a very small area of the audience anyway. Subs and mains can only be time aligned when they are physically close to each other, but then you have the alternate problem of nulls and power alley.

Mac Kerr
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Tim Padrick

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Re: News To Me!!!
« Reply #2 on: August 30, 2004, 12:26:01 am »

Mac Kerr wrote on Sun, 29 August 2004 08:50

 I wouldn't worry about timing the subs to the tops IF you are using a center cluster of subs, and left and right mains. Because of the separate locations of the subs and mains you could only align them in time for a very small area of the audience anyway. Subs and mains can only be time aligned when they are physically close to each other, but then you have the alternate problem of nulls and power alley.

Mac Kerr


IME, properly delaying the subs is a big help regardless.

Lets say the tops are not delayed to the subs, and the subs are centered.  If the lister is in the center and up close, the tops may be sufficiently farther away that they are aligned for that listener.  But as the listener goes back or off center the delay will reduce and the tops will eventually lead.

If the subs are delayed to be correct when with the tops, but are centered, the subs will lead if the listener is close and centered, but as the listener moves away or off center, the subs will lead less and will eventally be aligned prettly closely.  This will give a better result for a larger portion of the audience than the above.

If the subs are delayed to be correct when with the tops, and they are with the tops, they will be correct for anyone in the center of the room no matter what distance from the stage.  But for anyone off-center, the sub timing and response will be a mess.  Definitely the worst of the three scenarios.  

Mac Kerr

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Re: News To Me!!!
« Reply #3 on: September 01, 2004, 11:53:40 am »

TimmyP wrote on Mon, 30 August 2004 00:26

Mac Kerr wrote on Sun, 29 August 2004 08:50

 I wouldn't worry about timing the subs to the tops IF you are using a center cluster of subs, and left and right mains. Because of the separate locations of the subs and mains you could only align them in time for a very small area of the audience anyway. Subs and mains can only be time aligned when they are physically close to each other, but then you have the alternate problem of nulls and power alley.

Mac Kerr


IME, properly delaying the subs is a big help regardless.

My point was that you cannot physically or electronically time the subs to the mains so that in impulse signal from both reaches the listener at the same time if they are not physically near each other. If you are trying to get them within 20ms of each other, sure it's easy. If you are trying to get them within 5ms of each other, and 5ms is a pretty gross approximation of "in time", you will have an ally about 5-8 feet wide running from the stage to the back of the house where the timing is correct. It will not be correct for the rest of the room. Because of crossover phase response the subs will lag behind the mains to some degree. Depending on the crossover slope and speaker design this could be anywhere from 6-7ms to as much as 20ms. Depending on location in the room acoustic delay could be 5ms for the subs and 20ms for the mains, or it could be 5ms for the mains and 20ms for the subs. Which situation are you going to base your measurement on?
Quote:

Lets say the tops are not delayed to the subs, and the subs are centered.  If the lister is in the center and up close, the tops may be sufficiently farther away that they are aligned for that listener.  But as the listener goes back or off center the delay will reduce and the tops will eventually lead.

If the subs are delayed to be correct when with the tops, but are centered, the subs will lead if the listener is close and centered, but as the listener moves away or off center, the subs will lead less and will eventally be aligned prettly closely.  This will give a better result for a larger portion of the audience than the above.

How? If the mains are delayed relative to the subs at what spot in the room do you base it on? The subs are going to lead or trail at various spots in the room no matter what you do. The real question is what is the tolerance of delay error that you can live with?
Quote:

If the subs are delayed to be correct when with the tops, and they are with the tops, they will be correct for anyone in the center of the room no matter what distance from the stage.  But for anyone off-center, the sub timing and response will be a mess.  Definitely the worst of the three scenarios.  

The sub timing will not be off for someone who is not on center. Because the speakers are physically close together the acoustic delay will remain fairly constant and keep the time together throughout the room. The downside to this arrangement as I said earlier is that it will create a power ally in the center of the room, and may cause uneven coverage due to interference patterns.

Mac Kerr
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Tim Padrick

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Re: News To Me!!!
« Reply #4 on: October 04, 2004, 02:34:02 am »

Quote:


The sub timing will not be off for someone who is not on center. Because the speakers are physically close together the acoustic delay will remain fairly constant and keep the time together throughout the room. The downside to this arrangement as I said earlier is that it will create a power ally in the center of the room, and may cause uneven coverage due to interference patterns.

Mac Kerr


The timing will indeed be off for someone off center if the subs are with the tops, because the subs are NOT close together (unless we are talking about a center cluster instead of a L/R configuration).  If there wasn't a timing problem, there wouldn't be a power alley/comb filtering problem.

Mac Kerr

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Re: News To Me!!!
« Reply #5 on: October 04, 2004, 08:18:38 am »

TimmyP wrote on Mon, 04 October 2004 02:34

Quote:


The sub timing will not be off for someone who is not on center. Because the speakers are physically close together the acoustic delay will remain fairly constant and keep the time together throughout the room. The downside to this arrangement as I said earlier is that it will create a power ally in the center of the room, and may cause uneven coverage due to interference patterns.

Mac Kerr


The timing will indeed be off for someone off center if the subs are with the tops, because the subs are NOT close together (unless we are talking about a center cluster instead of a L/R configuration).  If there wasn't a timing problem, there wouldn't be a power alley/comb filtering problem.

You are taking my quote out of context. The timing issue I was referring to is the timing between the subs and the mains. My point was (and is) that there is no way to time the subs to the mains unless they are physically close together. I said in that post that there are problems created by each method. With the subs close to the mains you get a power ally, with the subs in the center it is not possible to time the subs to the mains for more than an "time ally" up the center of the room.

Mac
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Tim Padrick

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Re: News To Me!!!
« Reply #6 on: October 06, 2004, 12:27:05 am »

Mac Kerr wrote on Mon, 04 October 2004 07:18

TimmyP wrote on Mon, 04 October 2004 02:34

Quote:


The sub timing will not be off for someone who is not on center. Because the speakers are physically close together the acoustic delay will remain fairly constant and keep the time together throughout the room. The downside to this arrangement as I said earlier is that it will create a power ally in the center of the room, and may cause uneven coverage due to interference patterns.

Mac Kerr


The timing will indeed be off for someone off center if the subs are with the tops, because the subs are NOT close together (unless we are talking about a center cluster instead of a L/R configuration).  If there wasn't a timing problem, there wouldn't be a power alley/comb filtering problem.

You are taking my quote out of context. The timing issue I was referring to is the timing between the subs and the mains. My point was (and is) that there is no way to time the subs to the mains unless they are physically close together. I said in that post that there are problems created by each method. With the subs close to the mains you get a power ally, with the subs in the center it is not possible to time the subs to the mains for more than an "time ally" up the center of the room.

Mac


Now I see what you are saying, and I concur.  I hope you agree that the time alley is not nearly as big a performance compromise
as the power alley/comb filtering.
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