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Title: Any rules of thumb for installing speakers in a box-type room?
Post by: Steven Welwood on June 19, 2016, 11:09:35 PM
Hello all,

I have recently had some calls from schools asking me to recommend replacement mixers, mics, speakers, etc. in their aging gymnasium systems. Until now most of it has just been straight-across replacements.

The most recent one, however, will require that the speakers be relocated for various reasons. Since I've never had to choose a location for a permanent install, I was wondering if there are any rules of thumb that would help with determining the best location and aim. Most of the gyms I've been in (including this one) are close in size and layout, with two speakers mounted on the long wall.

For the horizontal mounting position (i.e. distance from end walls), is it better to split the target area in two and place a speaker in the center of each area (the blue speakers in the pic below), or should they be spread a bit further apart and aimed inwards to keep the sound off the side walls (the green speakers)?

For the vertical, I've pictured them at 18' high because that's how high the old ones are, but how should the best height be determined? Is there a certain percentage of the depth of the room that works best? I know the higher I go the more even the sound is through the depth of the room, but there must be a point of diminishing returns, right? The higher I go the more volume I'll need, and more volume is not what I want in a gym.

I normally try to aim the speakers close to the last row, but that doesn't work if there's a back wall close enough for bothersome reflections, besides overshooting the front few rows. I've tried to compromise between the coverage and getting the highs to the back row in the pic.

I know there are many more factors that will determine ideal placement and aiming, which is why I'm just asking for some general rules. I don't expect anyone to say my design will absolutely work. I'm just wondering if there's a reasonable chance that it could work.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Steven Welwood on June 19, 2016, 11:11:32 PM
Side view
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Ivan Beaver on June 20, 2016, 07:25:36 AM
Are you stuck with just 2 speakers?

If not-I would put 1 wide coverage one in the middle, and then explode 2 smaller ones off to the sides to cover the seats left/right down front.

The center one will do the "heavy lifting", while the others are just fills.

The center speaker will also pull the image to the center-NOT to the sides (as speakers on the sides will do)

Generally (depending greatly on the room) you should get the speakers as high as possible (within reason and the seating area) and point the center axis at the rear seats.

Of course the BEST way is to actually model it.

That will give you your best idea of actual coverage.

In a gym, using speakers with large horns helps greatly to control the pattern-resulting in less energy bouncing around.

By having most of the energy going to the people-they are absorbing the 1st reflection, therefore reducing the reverb in the room.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: David Allred on June 20, 2016, 07:56:29 AM
This is a gym?  Are there no bleachers?
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Steven Welwood on June 20, 2016, 01:44:43 PM
David, yes, this is an elementary/junior high school gym. Around here only high schools have bleachers--but even some of the smaller rural ones don't have them.

Ivan, sometimes 1 centre speaker would work. Other times there's a stage between the pair.

Quote
. . . get the speakers as high as possible (within reason and the seating area)

The "within reason" is what I'm wondering about. The pic shows the bottom of the speakers at 18', but it's a 28'ceiling. Should I put them all the way up (25 - 26')?

I tried a couple pieces of modelling software, but didn't like them. However, that was several years ago, so they've probably gotten better. Can you recommend a decent, simple modelling program that's not too expensive?

I'll keep the large horns in mind while I'm looking for speakers.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Scott Carneval on June 20, 2016, 02:34:13 PM

I tried a couple pieces of modelling software, but didn't like them. However, that was several years ago, so they've probably gotten better. Can you recommend a decent, simple modelling program that's not too expensive?

I'll keep the large horns in mind while I'm looking for speakers.

Danley Direct is free and pretty simple to use. The caveat is that it will only model with Danley speakers. The good news there is Danley makes some speakers that would work very well in your application.

EASE and EASE Jr. are both paid software, and have somewhat of a learning curve to them. The advantage is most manufacturers publish EASE data for their speakers, so you can model and compare just about anything using EASE.

You mention that you've never had experience choosing a location for speakers.  Do you have experience with rigging? Life safety is a major concern, especially when working around children.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Ivan Beaver on June 20, 2016, 07:58:36 PM


Ivan, sometimes 1 centre speaker would work. Other times there's a stage between the pair.


A stage in the middle is exactly where a center speaker would work best.

It pulls the focus towards the middle. Where-most likely-the people talking or performing would be.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Steven Welwood on June 21, 2016, 06:54:09 PM
Danley Direct is free and pretty simple to use. The caveat is that it will only model with Danley speakers. The good news there is Danley makes some speakers that would work very well in your application.

EASE and EASE Jr. are both paid software, and have somewhat of a learning curve to them. The advantage is most manufacturers publish EASE data for their speakers, so you can model and compare just about anything using EASE.

You mention that you've never had experience choosing a location for speakers.  Do you have experience with rigging? Life safety is a major concern, especially when working around children.

I never said I don't have experience choosing a location for speakers. You're taking my words out of context. I said I have never chosen speaker location for a permanent installation. There's a difference.

I always make sure to tell anyone that if there is any hanging or structural work to be done, I (or they) will have to bring someone in who is qualified for that type of work. While I don't have any classroom training, and would never present myself as anything close to an expert, for the last few years I have been working with someone who is trained and certified. During that time I have worked with rigging for lights and speakers, but always for event setups--never for installations.

Thanks for the software suggestions. Ease would be nice, but it's way out of my price range--for now at least. Danley Direct looks good. Too bad it doesn't model other brands, but not surprising.

A stage in the middle is exactly where a center speaker would work best.

It pulls the focus towards the middle. Where-most likely-the people talking or performing would be.

I agree, but most of the schools are on tight budgets (always an uphill battle), and they're more interested in clarity and coverage than localization. If it could be done for just a few hundred dollars more it would be feasible, but I don't think it would be worth any more that that to them.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: g'bye, Dick Rees on June 21, 2016, 07:30:51 PM

I agree, but most of the schools are on tight budgets (always an uphill battle), and they're more interested in clarity and coverage than localization. If it could be done for just a few hundred dollars more it would be feasible, but I don't think it would be worth any more that that to them.

The proper single centered speaker should  give you the needed coverage and certainly will give more clarity.  The localization is a bonus.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Steven Welwood on June 21, 2016, 08:10:46 PM
The proper single centered speaker should  give you the needed coverage and certainly will give more clarity.  The localization is a bonus.

Yes, but that's in addition to the pair, so besides another box and mounting hardware, there's also another amp and another channel of EQ to add in--unless I'm misunderstanding Ivan's suggestion. This would add at least CA$1000-1500, and I can't see my clients spending that much more for what would be perceived as an incremental improvement. Even if the front/side fills were run from a single channel, the cost of the extra single speaker alone would be more than they would want to pay.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: g'bye, Dick Rees on June 21, 2016, 08:22:23 PM
Yes, but that's in addition to the pair, so besides another box and mounting hardware, there's also another amp and another channel of EQ to add in--unless I'm misunderstanding Ivan's suggestion. This would add at least CA$1000-1500, and I can't see my clients spending that much more for what would be perceived as an incremental improvement. Even if the front/side fills were run from a single channel, the cost of the extra single speaker alone would be more than they would want to pay.

So you're opting to support their preference for cheap over correct.  Is this the path you want to take?  I prefer to do a proper design over bowing to budget pressure.  IME such organizations always find money for what they want and seldom spend it on what they need.

You just have to decide which side of things you can live with....what's right or what's cheaper.

Edit:

I dispute your cost figures.  They seem to be posted to support your assertion that your two speaker solution is the only one.  With a firmly established budget a qualified designer should be able to implement the LCR config.  And it may be possible to re-purpose the existing pair and other components, but you have yet to post that type of information.

Please don't use supposed penury as a technical argument. 
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Ivan Beaver on June 21, 2016, 09:19:49 PM


I agree, but most of the schools are on tight budgets (always an uphill battle), and they're more interested in clarity and coverage than localization. If it could be done for just a few hundred dollars more it would be feasible, but I don't think it would be worth any more that that to them.
And CLARITY is EXACTLY WHY I start with a center location.

You don't have the interference from 2 speakers covering the same area (as you would with speakers on the sides).

The coverage is much better also with less energy bouncing around.

Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Steven Welwood on June 21, 2016, 09:31:58 PM
So you're opting to support their preference for cheap over correct.  Is this the path you want to take?  I prefer to do a proper design over bowing to budget pressure.  IME such organizations always find money for what they want and seldom spend it on what they need.

You just have to decide which side of things you can live with....what's right or what's cheaper.

Edit:

I dispute your cost figures.  They seem to be posted to support your assertion that your two speaker solution is the only one.  With a firmly established budget a qualified designer should be able to implement the LCR config.  And it may be possible to re-purpose the existing pair and other components, but you have yet to post that type of information.

Please don't use supposed penury as a technical argument.


I really debated with myself on whether to post my question or not, because I figured there was a good chance of it turning into this. Ideally, I would be able to put in the perfect number of speakers at the perfect locations for every client. But you know what? That will often cost more than they have available, so yes, I have to take the cheaper path. I can advise them that another speaker or two would be better. If they don't think it's worth it, do I walk away? No, I try to make the best with what I have. If that means I'm "bowing to budget pressure," then so be it.

You say I'm asserting that my two speaker solution is the only one. I'm not. I just haven't seen a better solution that won't cost significantly more.

You seem to be asserting that the 3-speaker solution is the only one. I won't disagree that it would be slightly better, but I disagree that it's the only solution. I wouldn't be serving my clients well if I recommended a system that they've already said is out of the budget. Like I said, I can advise them that 3 speakers would be better, but I'm not paying for it--they are.

I've been in plenty of gyms that sounded good with two speakers on the long wall, with very even coverage. I recently changed out a pair of speakers using the location of the old pair (but with better aim), and the result was 100 times better than what they had before. Would a centre speaker have helped? Sure, but not enough to justify the price difference.

I appreciate the wealth of knowledge that the "senior members" of this forum share with others with less experience, but too often it seems like they think their reality is everyone's reality. There is usually more than one way to get a job done. Maybe there's one perfect way, but if another way can get 90% of the results at 70% of the cost, that way will usually win out.

I'm not using a limited budget as a "technical argument." I'm using it because it's a reality.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: g'bye, Dick Rees on June 21, 2016, 10:16:19 PM
Steven...

What is in there now?  I have often simply had existing speakers brought back to spec for a nominal cost, then re-used it as part of a better design.  If this is at all possible then your idea that an enhanced single center design may go out the window.  This takes full advantage of whatever meager monies may avail.

I'd advise not being an enabler for cheaping out no matter who the client.  Push for the right design with the right gear.  In the long run it will be less costly than trial and error resulting from "budget first" installs that fall short of the mark.

As to whether or not to post your question there's every chance that you've posted the wrong question or at least prejudiced discussion by limiting things to a two speaker system.  The "rule of thumb" would be to avoid overlapping coverage.  The separated two speaker deployments both violate this rule.


You can dismiss my suggestions and experience if you like, but if you don't listen to Ivan you're missing the boat.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Steven Welwood on June 21, 2016, 10:38:18 PM
Unfortunately the current speakers are ancient, and the tweeters are blown.

Yes, I likely did prejudice the discussion, because two speakers is probably the maximum the budget will allow for. That said, I will look into the possibility of a centre speaker, in case there is some way we can get it done.

Thank you, Dick and Ivan, for your advice. I will keep it in mind going forward.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: g'bye, Dick Rees on June 21, 2016, 11:04:37 PM
Unfortunately the current speakers are ancient, and the tweeters are blown.

I am unaware of any brand/model of loudspeaker marketed under the name of "Ancient".

If you're even half serious about a proper, economical solution the least you could do is provide the information requested.

If these were quality speakers in the beginning it is very probable that repairing and re-using them will do a decent job.  You could even place them both in the center splayed out IF they're of any quality at all.

But if you're making your nut by selling them new gear then this is not within such a business model.  There will be a way to make it work within their budget...if you open your mind.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Steven Welwood on June 22, 2016, 01:25:50 AM
I forgot to mention in my last post that the school wants speakers that can handle a lot more power. They regularly tried to get more volume out of them than they could give, which is probably why the highs are gone. Even if they can be repaired, they aren't the right speakers for the job.

When I visited the school there was no lift available to get close to the speakers and they didn't have any information about them. All I have to go on is that they are Toa, and the picture below. I looked through Toa's discontinued library and couldn't find a match, but maybe I just missed it.


Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: David Allred on June 22, 2016, 07:08:39 AM
Why not bring the 2 speakers (old repaired or new) into a center LR array?  Your layout doesn't show any forward tilt and neither does the picture imply any.  It is hard to get volume when it is firing over the heads of the audience.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Lee Douglas on June 22, 2016, 12:06:50 PM
TOA SL-222

90 x 40 horn with a Piezo driver

http://www.toa-products.com/international/download/spec/sl-122_cs1e.pdf
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: g'bye, Dick Rees on June 22, 2016, 02:55:24 PM
TOA SL-222

90 x 40 horn with a Piezo driver

http://www.toa-products.com/international/download/spec/sl-122_cs1e.pdf

Actually (according to the pic) it would be a 222.  SPL max @ 1m figures out between 124 and 129 dB depending on how they're powered.  The only real gotcha is that the piezo tweeter crosses over from the dual 12's at 5Khz.

In good operating condition they should be OK to fill the front corners of the seating area while a single 110 degree center speaker does the real work.  I like JBL CBT for a single center speaker in this case.  The matching LF  module can be added at any later date.

Go for the sound.  Pay what it costs.  Done. 

Alternative is 2 or 3 blind, budget-limited stabs at it likely totaling double or more what it costs to get it right the first time.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Steven Welwood on June 22, 2016, 03:30:43 PM
Thanks for finding that, Lee.

Dick, I'll look into this as an option, thanks.

David, I made the diagrams in MS Paint, which only allows rotations in 90 degree increments. I figured the lines were self-explanatory. The blue arrow in the second pic is the aim, the other blue lines are the approximate coverage.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Scott Carneval on June 22, 2016, 03:49:29 PM
Actually (according to the pic) it would be a 222.  SPL max @ 1m figures out between 124 and 129 dB depending on how they're powered.  The only real gotcha is that the piezo tweeter crosses over from the dual 12's at 5Khz.


Dick,

According to the spec sheet they have a 96db sensitivity and are rated at 80 watts continuous/240 watts program. That comes out to about 115-120db.

I think a couple of new speakers is in order. Or a single center speaker if you can get the right coverage out of it. Even a 90º speaker will have a wide enough pattern if you can mount it high enough.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: g'bye, Dick Rees on June 22, 2016, 08:59:03 PM
Dick,

According to the spec sheet they have a 96db sensitivity and are rated at 80 watts continuous/240 watts program. That comes out to about 115-120db.

I think a couple of new speakers is in order. Or a single center speaker if you can get the right coverage out of it. Even a 90º speaker will have a wide enough pattern if you can mount it high enough.

I read the specs differently.  I'll check again.

Edit:

Power handling specs read 80W continuous qualified as pink noise 50-20,000 hz for a period of 24 hours and continuous program PH of 240W.

Regardless, they would only have enough SPL for fill/support...which would be their role.  My reservation would be the 5Khz crossover.

I wonder what the intended program use would be and what SPL is sought.  My feeling is that they were degraded (blown tweeters) trying to overcome poor intelligibility with sheer volume or supporting Death Metal bands...
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: Steven Welwood on June 22, 2016, 10:10:34 PM
I wonder what the intended program use would be and what SPL is sought.  My feeling is that they were degraded (blown tweeters) trying to overcome poor intelligibility with sheer volume or supporting Death Metal bands...

While the principal didn't say anything about live music other than typical school productions and choirs, he did say that the kids occasionally played music from their own phones, which I'm sure would include death metal.

I admit I don't know exactly what SPL could be expected for a gym before the sound turns to mush. However, in the case of kids with their own playback, my guess is that they care more about volume than intelligibility.

Would 97dbA at 30' be too much? Not enough? My guess is that with the liveliness of the room, it will sound louder than it actually is, but it'll still be loud. I was asked to include a limiter with the installation, and I expect the kids will test it, though I hope to have a system capable enough that they won't hit the ceiling too hard.
Title: Re: Any rules of thumb for installing speakers in a box-type room?
Post by: g'bye, Dick Rees on June 23, 2016, 09:28:21 AM
Thanks for the info, short on time now.  SPL should be OK, but I'll let others address setting it up to limit things.

Edit:

You should probably gain stage the entire install such that no matter how much they input to the system it cannot be overdriven. 

Do the work at the front end rather than trying to save your a** at the back end, so to speak.