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Title: How much less than full volume will this be?
Post by: Joseph D. Macry on May 20, 2014, 09:41:22 am
I'm dealing with a gym sound designed specified by non-audio guys.
They specified the Octasound SP820A speaker cluster for a middle school gym, powered by Telecor 125 watt amp. The speaker is rated at 200 watts program. I suggested they upgrade to the Telecor 250 amp (250 watts @ 8ohms), otherwise the speaker will operate at "less than full volume."
They came back and asked "How much less than full volume ?"

Now I'm wondering how to quantify this, especially in a way that they will understand.
(There are political reasons for staying with the same brand of amp.)

Link to the speaker: http://www.octasound.com/products/360-x-180-models/sp820a-12-inch
Link to the amp: http://www.mytelecor.com/products_Amplifiers.php
Title: Re: How much less than full volume will this be?
Post by: Steve M Smith on May 20, 2014, 09:47:42 am
Does it need to operate at 'full' volume?


Steve.
Title: Re: How much less than full volume will this be?
Post by: Joseph D. Macry on May 20, 2014, 10:23:07 am
Does it need to operate at 'full' volume?

In a gym full of a few hundred middle school kids, I would expect that more is going to be better. Other than that, there is the general principal that the amp should be equal to or greater than speaker rating. Yes, it will work with the smaller amp, as long as it isn't clipping. Oddly, the manufacturer specs say that "optimum" power is 50 to 150 watts, which is right where the specified amp is rated.
But for now, the question is, how to quantify the volume difference between this speaker running with a 125 watt amp versus 250.
Title: Re: How much less than full volume will this be?
Post by: Steve M Smith on May 20, 2014, 10:36:28 am
About +3dB more volume.

Probably only about a 10% difference.

You would need about ten times the power to perceive a doubling in volume.



Steve.
Title: Re: How much less than full volume will this be?
Post by: Joseph D. Macry on May 20, 2014, 11:28:34 am
About +3dB more volume.

Probably only about a 10% difference.

You would need about ten times the power to perceive a doubling in volume.

Steve.

Thank you, Steve. I just got a message that they accepted my proposed upgrade, without the question being answered. Seems the cost difference was not excessive.
Title: Re: How much less than full volume will this be?
Post by: Craig Hauber on May 27, 2014, 12:56:30 am
Thank you, Steve. I just got a message that they accepted my proposed upgrade, without the question being answered. Seems the cost difference was not excessive.
Good, now talk them out of that speaker unit and they'll be even happier.

Those octosound units seem to be always under-spec'ed for the room and I've never heard one not being driven to death just trying to keep up with basic speech, let alone music.  (In fact I can safely say I've never heard one sounding good at all!)
Title: Re: How much less than full volume will this be?
Post by: Mike Caldwell on May 31, 2014, 11:27:35 pm
Good, now talk them out of that speaker unit and they'll be even happier.

Those octosound units seem to be always under-spec'ed for the room and I've never heard one not being driven to death just trying to keep up with basic speech, let alone music.  (In fact I can safely say I've never heard one sounding good at all!)

I'll just sum up Craig's response with "they sound like crap!"

I personally replaced two of the mid sized Octosound speakers in a gym with a nothing fancy system consisting of four properly powered 12 X 1 speakers evenly spaced along each side of the gym aimed into the bleachers and there was no comparison between before and after. That upgrade cost more than the original but the customer was finally happy with the sound in their gym.

Lets just say the speaker components in Octosound boxes I looked at were less than durable, defiantly not Eminence as the website now states.

I will say the design of the box does not lend itself to what they are used for, mounted high up along the roof with the horns all pointing more or less straight out.

Maybe they would work in a lower ceiling install for general paging where the background noise is low.

Here's another major fail I've heard used in gyms.
http://www.soundsphere.com/products/

 

Title: Re: How much less than full volume will this be?
Post by: David Sturzenbecher on May 31, 2014, 11:40:46 pm
I'll just sum up Craig's response with "they sound like crap!"

I personally replaced two of the mid sized Octosound speakers in a gym with a nothing fancy system consisting of four properly powered 12 X 1 speakers evenly spaced along each side of the gym aimed into the bleachers and there was no comparison between before and after. That upgrade cost more than the original but the customer was finally happy with the sound in their gym.

Lets just say the speaker components in Octosound boxes I looked at were less than durable, defiantly not Eminence as the website now states.

I will say the design of the box does not lend itself to what they are used for, mounted high up along the roof with the horns all pointing more or less straight out.

Maybe they would work in a lower ceiling install for general paging where the background noise is low.

Here's another major fail I've heard used in gyms.
http://www.soundsphere.com/products/

 

As I was reading your post all I could think of was the thousands of sound sphere gyms out there.... and then I read your last line and laughed out loud. Apparently people still buy them..... they are still at trade shows.
Title: Re: How much less than full volume will this be?
Post by: Mike Caldwell on June 01, 2014, 12:03:09 am
As I was reading your post all I could think of was the thousands of sound sphere gyms out there.... and then I read your last line and laughed out loud. Apparently people still buy them..... they are still at trade shows.

As bad as Octosound sounds I would say that Soundsphere is the clear winner as to how bad a sound system can sound in a gym.
At one time Soundsphere had a "high power" model that appeared to nothing more than one of their spheres with a bunch of piezo tweeters in it pointing out in all directions.
Maybe and again I say maybe.... in the right controlled environment even the Soundsphere might work, in noisy gym packed full of people during a basketball game, not a chance.....ever!
Title: Re: How much less than full volume will this be?
Post by: Jason Lavoie on June 01, 2014, 09:19:23 am
As bad as Octosound sounds I would say that Soundsphere is the clear winner as to how bad a sound system can sound in a gym.
At one time Soundsphere had a "high power" model that appeared to nothing more than one of their spheres with a bunch of piezo tweeters in it pointing out in all directions.
Maybe and again I say maybe.... in the right controlled environment even the Soundsphere might work, in noisy gym packed full of people during a basketball game, not a chance.....ever!

Interestingly, Soundsphere has recently (few years?) provided EASE data for their speakers, and funny enough since then the tweeters are only on the bottom side of the sphere now. so it appears that they learned something from the process of measuring their speakers.

Jason
Title: Re: How much less than full volume will this be?
Post by: Jason Lavoie on June 01, 2014, 09:42:06 am
I'll just sum up Craig's response with "they sound like crap!"

I personally replaced two of the mid sized Octosound speakers in a gym with a nothing fancy system consisting of four properly powered 12 X 1 speakers evenly spaced along each side of the gym aimed into the bleachers and there was no comparison between before and after. That upgrade cost more than the original but the customer was finally happy with the sound in their gym.

Lets just say the speaker components in Octosound boxes I looked at were less than durable, defiantly not Eminence as the website now states.

We used to sell a lot of their speakers before I knew better, but the tipping point was that they were swapping out components based on subjective listening tests done in their shop.
These changes were in some cases bad enough that replacing an old speaker with a new one of the exact same model would sound bad enough to require a DSP to bring it back to 'good'.

To maintain the hundreds of these speakers that we had installed over a decade or so I currently stock 4 different diaphragm models, and that doesn't even include the Eminence ones because none of those have ever blown (I know there were some units with Eminence because I've had to repair crossovers and come across them)
That also doesn't include one driver model that seems to have come from overseas that I haven't been able to source, so on those I have to replace the whole driver.
And if you're thinking that 6 different drivers doesn't sound too crazy from one manufacturer it's important to note that I never liked the smaller models, and the biggest has never blown a driver yet, so these 6 drivers are all for different (undocumented) generations of the same SP840 model.

Quote
I will say the design of the box does not lend itself to what they are used for, mounted high up along the roof with the horns all pointing more or less straight out.

Maybe they would work in a lower ceiling install for general paging where the background noise is low.

Exactly. The fixed angle of the horns changes it from what it is marketed as (all-purpose speaker) to what it really is (single-purpose speaker)
Not to mention that directly below the speaker there is a good 60 degree cone of muddiness, which isn't such a big deal in a hockey arena (where they started) but in a gym that could be filled with rows of seats that's a whole other issue.

Jason
Title: Re: How much less than full volume will this be?
Post by: Mike Caldwell on June 01, 2014, 12:30:26 pm
My last comment about Soundsphere and Octosound will be that they must hire some really good traveling medicine show sales people to put in their trade show booths.

Title: Re: How much less than full volume will this be?
Post by: Tommy Peel on June 01, 2014, 05:13:52 pm
A couple of weeks ago I was "DJing" for the youth at one of the churches I help at for a Dodgeball tournament in their gym. We had a single SRM450 and it worked fine for moderate volume music and speech.  I didn't have a small mixer handy so I had my laptop and a Shure VHF wireless mic plugged into a guitar A/B switch which outputs to the 450 with an adapter.  :-)  One of those I had to use what was available situations. A 4ch mixer would have been great.

(http://img.tapatalk.com/d/14/06/02/mytezany.jpg)

Sent from my Nexus 4 running Purity+ (http://forum.xda-developers.com/showthread.php?t=2762988)(All-F2FS and ART) + HellsCore b46-t4 (http://forum.xda-developers.com/showthread.php?t=2495373) using Tapatalk Pro

Title: Re: How much less than full volume will this be?
Post by: Tim McCulloch on June 02, 2014, 09:50:32 am
A couple of weeks ago I was "DJing" for the youth at one of the churches I help at for a Dodgeball tournament in their gym. We had a single SRM450 and it worked fine for moderate volume music and speech.  I didn't have a small mixer handy so I had my laptop and a Shure VHF wireless mic plugged into a guitar A/B switch which outputs to the 450 with an adapter.  :-)  One of those I had to use what was available situations. A 4ch mixer would have been great.


Secret weapon that fits in your backpack - Shure SCM-268.  Around $100 on fleabay.  It's heavy because it has transformers on the inputs and output.  Can supply 12v phantom, accepts -10 inputs on RCA jacks, balanced mic/line switchable output level.

The companion SCM-262 is a stereo mixer with a ducker, fewer XLR mic inputs, outputs on TRS 1/4", but still a versatile piece.  Also around $100 used.

I personally own several of each.  Highly recommended.
Title: Re: How much less than full volume will this be?
Post by: Joseph D. Macry on June 02, 2014, 11:15:12 am
Good, now talk them out of that speaker unit and they'll be even happier.

Those octosound units seem to be always under-spec'ed for the room and I've never heard one not being driven to death just trying to keep up with basic speech, let alone music.  (In fact I can safely say I've never heard one sounding good at all!)

Two reasons I'm going with the Octasound:
1. It was specified by the Architect.
2. I might get an upgrade job down the road.

As far as the tweeters shooting horizontally from on high, Octasound recommends placing them so that the bleachers are at a 15 degree down angle from the tweeters. This often conflicts with local competition league requirements that basketball courts be clear of obstructions for 25 feet above court.
Title: Re: How much less than full volume will this be?
Post by: Mike Caldwell on June 02, 2014, 11:28:27 am
Two reasons I'm going with the Octasound:
1. It was specified by the Architect.
2. I might get an upgrade job down the road.

As far as the tweeters shooting horizontally from on high, Octasound recommends placing them so that the bleachers are at a 15 degree down angle from the tweeters. This often conflicts with local competition league requirements that basketball courts be clear of obstructions for 25 feet above court.

How many of them were speced, is it just one centrally hung in the gym.

- That system is doomed to fail.
- Any architect who specs them in a school or college gym is an idiot
- Complete waste of the schools tax payer dollars.
Title: Re: How much less than full volume will this be?
Post by: Ivan Beaver on June 02, 2014, 12:08:54 pm
How many of the were speced, is it just one centrally hung in the gym.

- That system is doomed to fail.
- Any architect who specs them in a school or college gym is an idiot
- Complete waste of the schools tax payer dollars.
+100.
Title: Re: How much less than full volume will this be?
Post by: Tommy Peel on June 02, 2014, 12:15:09 pm
Secret weapon that fits in your backpack - Shure SCM-268.  Around $100 on fleabay.  It's heavy because it has transformers on the inputs and output.  Can supply 12v phantom, accepts -10 inputs on RCA jacks, balanced mic/line switchable output level.

The companion SCM-262 is a stereo mixer with a ducker, fewer XLR mic inputs, outputs on TRS 1/4", but still a versatile piece.  Also around $100 used.

I personally own several of each.  Highly recommended.

A SCM-262 would have been pretty nice with the ducker, though either would have done the job well. I'll have to try and pick one up sometime. Thanks for the info!
Title: Re: How much less than full volume will this be?
Post by: Cailen Waddell on June 02, 2014, 02:26:33 pm

A SCM-262 would have been pretty nice with the ducker, though either would have done the job well. I'll have to try and pick one up sometime. Thanks for the info!

We put one at all our ball fields (baseball, softball, etc). Can't say enough nice things about how easy and simple they are for non sound people to operate.


Sent from my iPhone using Tapatalk
Title: Re: How much less than full volume will this be?
Post by: Joseph D. Macry on June 04, 2014, 12:10:09 pm
How many of them were speced, is it just one centrally hung in the gym.

- That system is doomed to fail.
- Any architect who specs them in a school or college gym is an idiot
- Complete waste of the schools tax payer dollars.

Yes, one central unit specified. This architect has a history of specifying really bad designs. Sometimes we try to shove a redesign through, but this has always been painful and difficult. This time, we decided to do it as specified, although we made them upgrade the amp from a 125-watt model to 250, and replace the wall rack with one that is deep enough for the gear. Again, maybe we'll get a request for an upgrade next year.
Title: Re: How much less than full volume will this be?
Post by: Scott Carneval on June 04, 2014, 12:23:30 pm
Yes, one central unit specified. This architect has a history of specifying really bad designs. Sometimes we try to shove a redesign through, but this has always been painful and difficult. This time, we decided to do it as specified, although we made them upgrade the amp from a 125-watt model to 250, and replace the wall rack with one that is deep enough for the gear. Again, maybe we'll get a request for an upgrade next year.

So who's responsible if when the speaker fails and you changed the architect's design to double the power?

I get it that it's sometimes easier to build it to spec, but when you know for a fact that those specs aren't suitable for the application I believe that it's your responsibility to your industry to explain why, in writing, and offer an alternative.  You say that you've worked with this architect in the past, and if he won't budge then I would turn down the job. 
Title: Re: How much less than full volume will this be?
Post by: Mike Caldwell on June 04, 2014, 02:40:25 pm
The "upgrade" from a 125 to 250 watt amp is a drop in bucket and basically pointless.
The first time they play some pre game warm up music to pump up the crowd as just about all schools do these days either one of those amps is going to be driven into full clip as they try to get that woefully inadequate speaker to rock the house.

Personally if I was given that system spec to install I would explain to the school just how lacking it's going to be despite what they've be told be the architect and turn down the job. After it's installed the architect will long be forgotten but your name will be all over it and who they come calling to with the problems.

The architect should be made to sit in the bleachers for a couple of games so he could hear his work in action.

My guess it that architect has never been out to hear one of their "designs" in action at all and just stays in the office designing systems based on what they read on product cut sheets. I would not be surprised if they never hooked a speaker to an amp and made sound come out!
Title: Re: How much less than full volume will this be?
Post by: John Jackson on June 16, 2014, 05:00:41 am
I'm dealing with a gym sound designed specified by non-audio guys.
They specified the Octasound SP820A speaker cluster for a middle school gym, powered by Telecor 125 watt amp. The speaker is rated at 200 watts program.

From the Crown website:

"If you can prevent the power amp from clipping (by using a limiter), use a power amp that supplies 2 to 4 times the speakers continuous power rating per channel. This allows 3 to 6 dB of headroom for peaks in the audio signal. Speakers are built to handle those short-term peaks. If you cant keep the power amp from clipping (say, you have no limiter and the system is overdriven or goes into feedback) the amplifier power should equal the speakers continuous power rating. That way the speaker wont be damaged if the amp clips by overdriving its input. In this case there is no headroom for peaks, so youll have to drive the speaker at less than its full rated power if you want to avoid distortion."

http://www.crownaudio.com/how_much_power.htm
Title: Re: How much less than full volume will this be?
Post by: Tim McCulloch on June 17, 2014, 12:40:05 pm
From the Crown website:

"If you can prevent the power amp from clipping (by using a limiter), use a power amp that supplies 2 to 4 times the speakers continuous power rating per channel. This allows 3 to 6 dB of headroom for peaks in the audio signal. Speakers are built to handle those short-term peaks. If you cant keep the power amp from clipping (say, you have no limiter and the system is overdriven or goes into feedback) the amplifier power should equal the speakers continuous power rating. That way the speaker wont be damaged if the amp clips by overdriving its input. In this case there is no headroom for peaks, so youll have to drive the speaker at less than its full rated power if you want to avoid distortion."

http://www.crownaudio.com/how_much_power.htm

Mr. Macre already knows this.  He's pointing out that as a subcontractor, the equipment noted is specified by the project architect.  He is not free to redesign the system, nor is he in a professional position to challenge the architect in front of the client.
Title: Re: How much less than full volume will this be?
Post by: Joseph D. Macry on June 19, 2014, 07:22:22 pm
Mr. Macre already knows this.  He's pointing out that as a subcontractor, the equipment noted is specified by the project architect.  He is not free to redesign the system, nor is he in a professional position to challenge the architect in front of the client.

Thank you, Tim, that is exactly correct.
No DSP, no power module, no playback (just an AM/FM tuner!). Yes, I do consider this substandard in many ways. I am not the designer, and have not been invited to redesign. I am the installer, and I will give them what they ask for.
I did request they change rack models because the specified one was four inches to narrow for the specified gear. No cost increase, so they went with it.
Title: Re: How much less than full volume will this be?
Post by: Mike Caldwell on June 20, 2014, 12:10:42 am
Thank you, Tim, that is exactly correct.
No DSP, no power module, no playback (just an AM/FM tuner!). Yes, I do consider this substandard in many ways. I am not the designer, and have not been invited to redesign. I am the installer, and I will give them what they ask for.
I did request they change rack models because the specified one was four inches to narrow for the specified gear. No cost increase, so they went with it.

Keep in mind that your name will be the only name associated with that system that any one will remember, the direct customer and any possible future customers who may hear the system in use.
Title: Re: How much less than full volume will this be?
Post by: Joseph D. Macry on June 20, 2014, 09:24:02 pm
Keep in mind that your name will be the only name associated with that system that any one will remember, the direct customer and any possible future customers who may hear the system in use.

Wrong, Mr Caldwell. The architect and General Contractor have their name on this, not I.
Title: Re: How much less than full volume will this be?
Post by: Mike Caldwell on June 21, 2014, 07:43:10 am
Wrong, Mr Caldwell. The architect and General Contractor have their name on this, not I.

At least in my experience when doing a service call or upgrade on a system the customer refers to who installed the system during the conversation. There are times when I know a system was installed to a designed spec from an architect and the installer's name is still the only name mentioned, that can be good or bad for the installers reputation depending on the design and quality of installation.
Title: Re: How much less than full volume will this be?
Post by: Joseph D. Macry on June 21, 2014, 10:53:38 am
This thread has migrated from a question about increasing amp power to one about installing a substandard design, which is indeed the more interesting question. I think I'll start a new thread on that topic later today.
Title: Re: How much less than full volume will this be?
Post by: Steve M Smith on June 21, 2014, 12:54:25 pm
Wrong, Mr Caldwell. The architect and General Contractor have their name on this, not I.

Make sure their names are actually on it. i.e' apply a label stating "Specified by  Xxxxx and Yyyyy"


Steve.