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Author Topic: Series parallel  (Read 4791 times)

Christopher Young

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Series parallel
« on: May 02, 2011, 02:32:53 PM »

I've got something open for debate here.  I'm doing a side job (normally I do the all the installed AV for a Univiversity) for a friend of my who owns a bike shop.  It's a brand new big store, (the old one burned down) and we're putting in a BGM/paging system.  The problem is, that as usual, no one thought about AV until the drywall was going up. They brought in a guy to run the wires that were needed but to my taste no where near enough.  So I'm stuck with two pair running to the main floor and 2 pair running to the second floor.    I'd like to put 8 to 12 small good fidelity speakers (probably PSB) on the 2nd floor and another 6 to eight on the Main floor (smaller floor space).  Normally with so little wire I'd just do it all 70V, but normally I'm more concerned about voice intelligibility than music fidelity.  So I'm wondering if anyone can see a reason not to simply combine the speakers in a series/parallel configuration to make up a reasonable impedance.  I've never done it before, but I can't for the life of me come up with a reason not to.

Cheers

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Jonathan Kok

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Re: Series parallel
« Reply #1 on: May 02, 2011, 06:38:45 PM »

I've got something open for debate here.  I'm doing a side job (normally I do the all the installed AV for a Univiversity) for a friend of my who owns a bike shop.  It's a brand new big store, (the old one burned down) and we're putting in a BGM/paging system.  The problem is, that as usual, no one thought about AV until the drywall was going up. They brought in a guy to run the wires that were needed but to my taste no where near enough.  So I'm stuck with two pair running to the main floor and 2 pair running to the second floor.    I'd like to put 8 to 12 small good fidelity speakers (probably PSB) on the 2nd floor and another 6 to eight on the Main floor (smaller floor space).  Normally with so little wire I'd just do it all 70V, but normally I'm more concerned about voice intelligibility than music fidelity.  So I'm wondering if anyone can see a reason not to simply combine the speakers in a series/parallel configuration to make up a reasonable impedance.  I've never done it before, but I can't for the life of me come up with a reason not to.

Cheers
The biggest downfall to series/parallel is the fact that if one speaker in the string goes down, you lose them all.  But if you can find 16ohm speakers, it'll reduce the amount of series wiring required.  Fulcrum Acoustics and Martin come to mind, I'm sure there are others.

Though frankly, there are a number of good quality 70v speakers out there, available from a number of manufacturers.  EAW, Tannoy, JBL, Turbosound, Martin, etc.
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Hal Bissinger/COMSYSTEC

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Re: Series parallel
« Reply #2 on: May 02, 2011, 07:23:32 PM »

I can't see any reason not to use a 70 volt system. You will only use 1 pair to each floor. Forget stereo and the hairbrained idea of series/parallel. That's amateur hour stuff that just isn't done. A 70 volt system will sound just fine if you use quality speakers.
 
-Hal
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Brad Weber

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Re: Series parallel
« Reply #3 on: May 02, 2011, 09:19:56 PM »

It's a brand new big store, (the old one burned down) and we're putting in a BGM/paging system.
Normally with so little wire I'd just do it all 70V, but normally I'm more concerned about voice intelligibility than music fidelity.
Especially for a background music and paging application it's hard to believe that there are no 70V speakers that would provide sufficient fidelity.  And while I am not familiar with PSB speakers, they seem to be a residential product which means that you may want to verify if their warranty covers commercial/professional use.
 
So I'm wondering if anyone can see a reason not to simply combine the speakers in a series/parallel configuration to make up a reasonable impedance.  I've never done it before, but I can't for the life of me come up with a reason not to.
One potential problem challenge with series/parallel wiring is accommodating changes or the possibility of others trying to service/modify the system.  Add or disconnect a speaker and it could have a significant effect.  Another potential drawback in some applications is that unlike a transformer with taps, you have no easy to adjust the level of individual speakers.
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Christopher Young

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Re: Series parallel
« Reply #4 on: May 03, 2011, 09:40:33 AM »

Thanks for the input as usual guys. 

I hadn't thought of someone else having to service it, that is a real concern. I did consider "one goes they all do" but I'm still running several channels so it's not a huge concern.

PSB is the default choice for 2 reasons;
                          The GM,  Owner and I, are all long time friends with someone at PSB
                           I've never heard a pair of PSBs that didn't sound great, and even better, still sound great at their price point.

With all due respect Hal, I don't dismiss a design based on whether "it just isn't done" or not.  I never said anything about stereo.  I'm not interested in a system that sounds 'just fine'.  I've got over 100 systems on campus that sound 'just fine' that is not the goal this time around.  I've installed countless 70V systems from JBL, TOA EAW and have heard several other brands in other locations.  When I walk into a retail store or restaurant and am surprised by how good it sounds, it's never a distributed system.

I'm not saying 70V can't sound good, I've just never heard it.  Really if I was going to go that route, I'd probably buy the PSB's and stick transformers on them, (I'm likely using the Crown 108MAx and a 660) but I'm worried that that would degrade the signal enough to make it a pointless endeavor. We all know good audio transformers are expensive for a reason.
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Hal Bissinger/COMSYSTEC

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Re: Series parallel
« Reply #5 on: May 03, 2011, 08:14:59 PM »

When I walk into a retail store or restaurant and am surprised by how good it sounds, it's never a distributed system.

How could you tell? I might agree that powered subs are used quite often but the rest of most systems I have seen are distributed. How else would you support large numbers of speakers?
 
I'm likely using the Crown 108MAx and a 660) but I'm worried that that would degrade the signal enough to make it a pointless endeavor. We all know good audio transformers are expensive for a reason.
 
If you are designing around a 180MAx you are certainly doomed. If you want mediocre that's a good start.
 
Use an amp that is direct 70.7v drive with several more times the power than you need. That eliminates the output transformer right there. Use a DSP that will give you processing as well as an active crossover for your subs. Use quality speakers.
 
I don't dismiss a design based on whether "it just isn't done" or not.
 
Is that any less a reason for doing or not dong something than-
 
The GM,  Owner and I, are all long time friends with someone at PSB
 
-Hal

 

 
 
 
 
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Brad Weber

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Re: Series parallel
« Reply #6 on: May 04, 2011, 07:15:19 AM »

When I walk into a retail store or restaurant and am surprised by how good it sounds, it's never a distributed system.
I'll bet many of those were distributed systems as multiple speakers distributed around a space all reproducing the same signal is by definition a distributed system.  In fact, there is often no way to readily tell whether a system is 70V, in some cases you could use the same speakers in a 70V or direct driven system and all you do is change a setting on the speaker.  And although it is very common for people to try to assign the results to just the more visible aspects, which are the products, the results for any audio system, whether good or bad, are a actually factor of acoustics, system design, installation practices, tuning, etc. as well as of the products used.
 
I made the comment about the PSB speakers only because some consumer/residential products warranties either won't cover or specifically exclude commercial and/or professional use from their warranty coverage.  I believe that using those products in such applications not only leaves the client at risk but it also seems to indicate that the  products may not be intended for such applications.  After looking at the product data, data sheets, manuals, FAQs, etc. on their web site, I couldn't tell what warranty applies to the PSB speakers, much less if there are any relevant exclusions.  However, their copyright for the web site limiting use of the web site content to personal use and expressly prohibiting 'commercial use' of the content, i.e. printing out a product data sheet to give to a client being prohibited, unless you are an authorized dealer or distributor suggests that their products are not intended for commercial applications.
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Christopher Young

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Re: Series parallel
« Reply #7 on: May 04, 2011, 02:05:01 PM »

Once again all advice is helpful and welcome.

I guess I should have said 70V rather than "distributed" but to me distributed is transformer based.  I agree you can't look at a can or a wall mounted speaker and know if it has been set to 8ohms or tapped.  So to be clear, every time I am impressed by the sound in a location, it tends to be some consumer speakers.  And in my neck of the woods at least, it is often PSBs  Of course this is easy in a small bistro or record store, it becomes much more difficult in a location like I'm trying to do.  Please understand here, I'm shooting for really good sound, with some pretty major location, wiring and budget challenges.   It may not be possible, but I'm going to try.   I've heard some pretty good cans, and I've heard some pretty good plastic boxes, but nothing that satisfies my current goal.   An 80year old family business that I've had a great relationship with burned to the ground 3 years ago, and if I can give these guys something special, I will.  My initial post was just that, a way to get distributed sound without running a lot more wire, or using transformers.  I had planned to source a direct drive 70V amp if I had to go that way, but there is still the matter of the speakers.

The 180MAx is bad?  I haven't heard good or bad on this.  Is it the quality of Satellite radio in general, or is it the box itself?   All my Satellite radio experience is one installation on campus (weight room), and the speakers in there make it impossible to judge.

BTW Brad, PSB does sell a plastic box meant for commercial installs, but I don't think it's 70V.  It's not on the web site yet.  I'll be discussing it with them.

 
Is that any less a reason for doing or not dong something than-
 
The GM,  Owner and I, are all long time friends with someone at PSB

 
I would say yes.  I was a fan of PSB long before my friend took a position there, so I would have been looking pretty hard at them anyways. If we can get a deal, and throw a friend some business, that's good.

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John Roberts {JR}

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Re: Series parallel
« Reply #8 on: May 04, 2011, 02:14:01 PM »

The calculus for installed sound systems involves several parts.

Sound quality is balanced against cost, installation complexity, control options, and significantly reliability and ease of servicing.

Constant voltage (70-100V) systems have been around for a long time because they work so well in balancing all of the the concerns.

If you put in some odd ball series-parallel arrangement, be sure to document the system well, and include your home phone number.  ;D

JR
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Christopher Young

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Re: Series parallel
« Reply #9 on: May 04, 2011, 02:50:17 PM »

I hear ya John. 

Until Brad mentioned someone else having to service it, I hadn't considered it.  If I do go this route, I will most certainly document it and leave notes cached.  I do that sometimes when I am forced to do something wacky like a connection 3 feet inside a conduit.  I leave a note permanently affixed to the offending cable.  In this case a small diagram and note glued to the back of each speaker may be in order.

They'll have my home phone number whether I want them to or not.   :P

Chris
« Last Edit: May 04, 2011, 03:41:51 PM by Christopher Young »
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Re: Series parallel
« Reply #9 on: May 04, 2011, 02:50:17 PM »


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