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-   -   Receiver vs Amp (http://www.avsforum.com/forum/91-audio-theory-setup-chat/1478767-receiver-vs-amp.html)

lAresl 06-24-2013 05:45 PM

Howdy,

I was put in charge to purchase an audio system (mainly PA) for a 50'x20' (approx) room to be used as a conference room.

Quick question: use a home theater receiver as an amp, or use a 'real' amp to power speakers?

Long background:

Since home theater is my only experience, my initial thought was to buy a mixer for mic input (4-6 channel) connected to a home theater onkyo 7.1 channel receiver powering Polk OWM3.

While this set-up should work, and probably be under 600$ (receiver, mixer, and 6 speakers), I'm wondering if swapping the receiver with a 'real' amplifier would be better... However, the 'real' amplifiers are going to be more expensive, and a little daunting to set-up... The Crown XLS 1000 for example, has 200w/side @ 8ohms, 700w bridged @ 8ohms. For my 6speaker set-up, I'll more than likely want to bridge. This set-up will also be at least 100+ more than the receiver set-up.

The equipment will probably be used once a week, if that. Maybe 8hr weekend conferences.

Ideas welcome.

commsysman 06-25-2013 05:28 AM

What you should get is not an HT receiver, but a Public Address amplifier with a "70V" output that can drive up to 10 speakers in parallel.

You do not want sound processing that is going to create different sounds for the different channels; you want a monaural system with the same sound from all channels. Many of these PA amplifiers have mixers built in, and they are generally not very expensive.

There are several links online that discus how to set up a PA system with a 70V amplifier and PA speakers.

One of the best is the "System Design Guide' at www.bogen.com/support, which tells you all about the fundamentals and guides you in selecting what you need.

arnyk 06-25-2013 05:46 AM

Quote:
Originally Posted by lAresl View Post

Howdy,

I was put in charge to purchase an audio system (mainly PA) for a 50'x20' (approx) room to be used as a conference room.

Quick question: use a home theater receiver as an amp, or use a 'real' amp to power speakers?

Long background:

Since home theater is my only experience, my initial thought was to buy a mixer for mic input (4-6 channel) connected to a home theater onkyo 7.1 channel receiver powering Polk OWM3.

While this set-up should work, and probably be under 600$ (receiver, mixer, and 6 speakers), I'm wondering if swapping the receiver with a 'real' amplifier would be better... However, the 'real' amplifiers are going to be more expensive, and a little daunting to set-up... The Crown XLS 1000 for example, has 200w/side @ 8ohms, 700w bridged @ 8ohms. For my 6speaker set-up, I'll more than likely want to bridge. This set-up will also be at least 100+ more than the receiver set-up.

I work with rooms like this from time to time.

A sound system for a conference room this size will probably have a preferred orientation, that is one end or one side of the room will be the preferred location for originating presentations. That means that 2 loudspeakers mounted as high as reasonably possible and spaced along that wall will suffice. Therefore the complexities of a 70 volt system is not needed. The two speakers should be high quality "PA" speakers, with Electrovoice ZX-1 or ZX 4s being my first chioce.

The "amplifier" can be what is known as a "powered Mixer" such as one of these:

http://www.behringer.com/EN/Category/Mixers.aspx?s=A500

lAresl 06-25-2013 06:55 AM

Thank you for both replies.

While I specified the specs, I forgot to mention the fact that the room is only 10' high and with paneled ceiling. Below is a 500x200 pixel drawing of the room. The skinny lines are dividers that can be closed/opened depending on room use. A good reference is to think of 2.5 two car garages. with a lower ceiling.

@commsysman:
Quote:
You do not want sound processing that is going to create different sounds for the different channels; you want a monaural system with the same sound from all channels.

The onkyo system that I have cited has a mono sound feature which will cover what you mentioned.

@arnyk:
The rectangular room will have the presenter in one of the shorter sides. With that said, I had planned to put 2 speakers ever 20' or so. I don't think that putting two zx-1's will be a good choice as it will be too loud for the people up front and too faint for the people out back.

Unless you're thinking of putting 1 up front and one in the middle/rear.

I checked those powered mixers yesterday and thought I'd use one of those with the Polk OWM3 speakers that I'm thinking about. However, how will I connect that speakON connector to the Polks?

Again, I appreciate all the discussion.


arnyk 06-25-2013 07:47 AM

Quote:
Originally Posted by lAresl View Post


The rectangular room will have the presenter in one of the shorter sides. With that said, I had planned to put 2 speakers ever 20' or so.

If you do that, you'll need to add extra power amps and delay lines, and not get a lot for your trouble. The reason for this is that the delays associated with the distance down the room will cause fairly pronounced simulated echoes.

I've been in rooms this size with more than 2-3 speakers at the working end and it can be pretty nasty.

I specified mounting the speakers as high as possible to obtain the most uniform sound distribution that would be possible.

I've served rooms about this size and configuration and a simple 2 speaker setup can work.
Quote:
I don't think that putting two zx-1's will be a good choice as it will be too loud for the people up front and too faint for the people out back.

If the ceiling is very low, that could happen. A 9-12 foot ceiling can get even enough distribution. If your ceiling is taller than that, you're in like Flynn.

One rule of thumb is to try to keep the ratio between the minimum and maximum distance within a 2:1 range. Another rule of thumb is that most rooms never have every seat filled very often, and people tend to sit towards the front.

I always use 12 gauge to connect Speakon connectors to speakers.

The last time I connected consumer speakers to pro gear with Speakons, there was a little trip to my workshop for installation of Speakons in parallel with the banana jacks that were already there.. Another approach is to put a male Speakon on a short pigtail attached to the speaker, which connects to the usual Speakon cable that attaches to the power amp.

lAresl 06-25-2013 08:28 AM

Thanks.

I think I'm being pointed to the right direction...

Yay or nay:

Behringer Europower PMP530M

http://www.sweetwater.com/store/detail/PMP530M/

A pair of Electrovoice EVID3.2 (for ceiling mount-able)

http://www.amazon.com/Electro-Voice-twin-woofer-tweeter-White/dp/B0010EGTZ0/ref=sr_1_1?s=electronics&ie=UTF8&qid=1372174080&sr=1-1&keywords=electrovoice+3.2

arnyk 06-25-2013 10:00 AM

Quote:
Originally Posted by lAresl View Post

Thanks.

I think I'm being pointed to the right direction...

Yay or nay:

Behringer Europower PMP530M

http://www.sweetwater.com/store/detail/PMP530M/

Lotsa potential. I use Behringer mixer with a similar configuratino.

I wouldn't. It is important to have the speakers pointed at the listeners and pointable to suit the size of the group you are working with.

Also, the speakers I recommended are vastly different speakers - much more controlled directivity, better dynamic range.

lAresl 06-25-2013 09:08 PM

Going back to the zx1 ideas... The ceiling is about 10' high so would it be a good idea to horizontal 'fly' mount 1 zx1 at the front (15' mark) middle of the room and another one in the 35' middle of the room?

Or would it be best to put both of the zx1's at the front 10-15' of the room? I don't think vertically 'fly' mounting the speakers would be a good idea as kids/people would jump for it and may cause accidents.

arnyk 06-26-2013 09:06 AM

Quote:
Originally Posted by lAresl View Post

Going back to the zx1 ideas... The ceiling is about 10' high so would it be a good idea to horizontal 'fly' mount 1 zx1 at the front (15' mark) middle of the room and another one in the 35' middle of the room?

We're not communicating. I told you why this isn't a good idea, explained it in detail. It will generate strong echoes.
Quote:
Or would it be best to put both of the zx1's at the front 10-15' of the room?

If your intent is to use the space from the speakers to the front wall as working space for the screen and presenter if any then this can work.

The room arrangement would be:

First 10-15 feet - essentially like a stage area. The working area for the screen and presenter. Screen hung on front wall.

Speakers hung from ceiling or side walls. at 10-15' down the room. If there is a projector then it would be hung in this space. Speakers hung as high as possible and if on the side walls, canted inward somewhat. The speakers weigh about 16 pounde a piece so they are relatively easy to hang, If hung on the side walls, then this mount can work:

http://www.parts-express.com/pe/showdetl.cfm?partnumber=248-4660



If you wish to mount the speakers close to the wall with these mounts it is easy to trim the swinging bar and drill new fastening holes. This is a good idea.

If you hang the speakers from the ceiling, then you can use screw eyes firmly fastened to the ceiling structure, threaded screw eyes threaded into the threaded holes in the top of the speakers, with 4 short 1/4" nylon ropes or 1/8" metal chains between the eyes to angle and support.

Next 5-10 feet - space so that audience is sitting a decent distance back from the active elements of the presentation including the speakers

Remainder of room - seating.

Quote:
I don't think vertically 'fly' mounting the speakers would be a good idea as kids/people would jump for it and may cause accidents.

If the ceiling is 10' you should be able to fly the speakers close to the ceiling and still have them way more than 7' above the floor.

The ZX-1 speakers are under 13" high so cleaing 8 1/2 foot should be easy.

lAresl 07-05-2013 06:34 PM

Thanks guys. I'm going to have a professional look and give me more ideas.


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