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Topic: Amp & Speaker Compatability (Read 4173 times) previous topic - next topic
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Amp & Speaker Compatability

Hi there,

I've decided to delve in to the world of in-ceiling speakers for my new single-storey 5m wide (16ft) kitchen extension as stand-alone's won't really fit anywhere. I didn't include a speaker system in my budget so i'm mindful of not going crazy so my budget is in the GB £400 mark and having seen the following Pioneer amp on offer at £99 it got me thinking...

I've been reading up on ohm and wattage compatibility and I get the basic idea but after a quick nip in to the local Audio shop the chap recommended using two stereo speakers for a better spread and this is where i'm now unsure of my amp/speaker options. I know that stereo speakers typically use four channels from the amp, but can I get away with using two channels; I'm thinking of this:

http://www.pioneer.eu/eur/products/42/202/...51-K/specs.html
2 channel; Power RMS 50W + 50W (4Ω)

http://www.monitoraudio.co.uk/products/ci-...#/specification
Impedance (Nominal): 6+6 ohms
Recommended Amp Requirements: 20 - 65 W

If I wire the speakers in series will this work?

1 Amp Channel = 50W, 4 ohms
1 stereo speaker = Recommended Mon 20W, 6 + 6 ohms, wired in series = 12 ohms
 
I hope this makes sense! Is it viable and if so is it realistic? I don't play my music particularly loud but then again I don't want to be worrying if I turn up to cut above general kitchen/people noise so if this setup is particularly risky to amp or speakers then i'd prefer to re-assess my options and consider two mono speakers instead.

Any help or guidance you can provide would be very much appreciated!

Cheers,

Steve

Amp & Speaker Compatability

Reply #1
Don't ever wire speakers in series, as there could be an undesirable interaction between them.

Wiring them in parallel is OK, but you end up with a load on your amplifier of half the impedance, which could be too low for some combinations of amplifier and speakers.

Amp & Speaker Compatability

Reply #2
Did you link to the right amp?  The page I get is for an entire system.

Amp & Speaker Compatability

Reply #3
Stereo is 2 channels, not 4.

If you intend to use just a single one of those speakers (as it appears to be designed) then it will have terminals to wire 2 channels to the speaker. Either 4 separate terminals or 3 with a common ground. (I'm not thrilled with a 3 terminal situation)

In this case you would get less than the 50W per channel from the amp driving a 6 ohm load per channel, but it will work. In the kind of space you are talking about there should be room to mount 2 speakers in there. I think you would be far better served by separate speakers.

The specs on that speaker are pretty abysmal, though I've not looked at speakers designed for that use before. As far as general speakers go though they aren't that hot on paper.

Amp & Speaker Compatability

Reply #4
Quote
but after a quick nip in to the local Audio shop the chap recommended using two stereo speakers for a better spread and this is where i'm now unsure of my amp/speaker options.
I agree, and with two separate speakers you don't need that special speaker with two tweeters.

Quote
I know that stereo speakers typically use four channels from the amp
If you are thinking the woofers & tweeters need separate amplifiers, they don't.  There is a "crossover network" built into the speaker that sends the lows to the woofer and the highs to the tweeter.

Quote
I don't play my music particularly loud
In that case I wouldn't worry about it.  Speakers usually get "blown" at loud parties and/or when there is alcohol or immaturity involved.  The specs say 20-65W, and that should be a reasonable guideline.  I wouldn't worry about using a 100W amplifier (or more) as long as you don't get crazy with the volume.  If the kitchen noise gets really loud, it's unlikely that you are going to want even louder music to drown-out the noise.

It gets really complicated...  Speaker specs in generally are fairly useless.  Power ratings are especially tricky for a couple of reasons...  Music has a peak-to-average ratio of about 10:1 (depending on the music, of course), which means if you amplifier is hitting 50W on the peaks (just below clipping/distortion), it's putting about 5W average into the speaker.  And, the high frequencies in music have much less energy than the mids & bass (again depending on the music).    So, you are probably fine with 50-65W of undistorted music. 

But, you could probably fry the tweeter with a constant  20W high-frequency test-tone, and you could probably fry the speaker (woofer or tweeter) with highly distorted music (which might have 50-65 of average power).  If you wanted to be perfectly safe, you'd end-up with a 5-10W amplifier or a 500W speaker which doesn't make any sense either.

Amp & Speaker Compatability

Reply #5
Hi all,

Thank you for your replies, much appreciated.

Just to clarify I realised each single speaker had two/stereo inputs  I was wanting to check if using the 2-channel amp as above could sustain 2 stereo speakers.

A couple of comments are now making me think that two stereo speakers may not be such a revolutionary solution as first thought and it does add a level of complexity especially when trying to use a basic 2-channel amp (Lithopsian, the link was correct but I would buy the component only, not the speakers).

DVDDough - thanks for affirming the numbers can get a bit confusing! It's good to know the setup would work.

Non-stereo speakers are a fair bit cheaper and i've had my eye on Polk Audio in-ceiling speakers of which the RCI series get good reviews for the price-level. So while still being mindful of budget but wanting to have a reasonable intro system i'm thinking of the following:

x1 http://www.pioneer.eu/uk/products/22/98/40...20-K/specs.html
A pair of these for the main kitchen area: http://www.polkaudio.com/products/rc80i
A pair of these for the adjacent dining area: http://www.polkaudio.com/products/rc60i

By not using stereo speakers and from importing from the USA the cost works out pretty much the same as the previous setup bought in the UK (£390) and I get to pop a secondary set of speakers in the other room.

Can anyone see any reason why this setup would not be successful, the Pioneer amp has an A/B split button with eight output terminals on the back.

Pioneer 100W + 100W
• 4-16 Ω (A / B)
• 8-16 Ω (A + B)
• 4-16 Ω (Bi-Wire)
x2 6 ohm mono speakers 8.5 inch woofer (kitchen) Polk recommend 20 - 100W for this speaker
x2 6 ohm mono speakers  6.5 inch woofer (dining room) Polk recommend 20 - 100W for this speaker

If I now understand correctly with all 4 speakers running at the same time the amp load/total will be 16 ohms, with all 4 speakers running the speakers will total 24 ohms but there is enough wattage per channel (even if in reality there are 2 speakers powered by each channel of the amp) to sit nicely in the middle (circa 50W with headroom) of the speakers recommended amp power...?

I hope all that makes sense!!

Many thanks,

Steve

Amp & Speaker Compatability

Reply #6
The A + B switch position will connect the speakers in parallel, not series, so the load impedance is not 12 ohms (and certainly not 24 ohms) but 3 ohms. This is slightly below the manufacturer's recommended rating. I would look for 8 ohm speakers instead, which would provide a 4 ohm load, as per the manufacturer's spec.

Amp & Speaker Compatability

Reply #7
Quote
Pioneer 100W + 100W
• 4-16 Ω (A / B)
• 8-16 Ω (A + B)


If I now understand correctly with all 4 speakers running at the same time the amp load/total will be 16 ohms, with all 4 speakers running the speakers will total 24 ohms
No. With both speakers switched-on, the A+B switch will put them in parallel for a result of 4 Ohms.  That's how they "always" work, and the fact that you must use speakers of 8 Ohms or greater with A+B is another clue.

Quote
x2 6 ohm mono speakers 8.5 inch woofer (kitchen) Polk recommend 20 - 100W for this speaker
x2 6 ohm mono speakers 6.5 inch woofer (dining room) Polk recommend 20 - 100W for this speaker
The RC60i & RC80i are 8 Ohms.  (Thanks for giving us a link to the specs.  )



...A couple more technical things that you don't really need to know - The amp is rated for 50W per channel at 4 Ohms.  With four 8-Ohms speakers, that's 25W per speaker. 

Solid state amplifiers tend to be "constant voltage" devices.  The voltage isn't really constant, since music isn't a constant tone.    What constant voltage means is that you get the same voltage out with a 4 or 8 Ohm load.  The current (and power) depend on the load impedance (Ohm's Law), so you'll probably get about 25W per channel with 8-Ohms speakers.  And, if you are listen to the kitchen speakers only and you switch to A+B, the volume (wattage) in the kitchen shouldn't drop when you switch-in the 2nd pair of speakers.


Amp & Speaker Compatability

Reply #8
Hi there,

Thanks for the replies.

Well spotted - yes my error the speakers are 8 ohms each!

So to clarify before digging in to the detail below, my circuit/ohm logic was wrong but this setup will work with the last equipment I listed above?

DVDdoug, just when I thought I understood...!  Please bear with me on the wattage - using both A+B is a parallel circuit resulting in the ohms per speaker halving; would that not also make the 100W channel essentially 50W per speaker (2 speakers per channel in my setup)? Or is it that the parallel circuit halves everything so each channel is then 50W, with two speakers doubling the resistance on the same channel that's 4 ohms and circa 25W per speaker? If so, I know the recommended range by the speaker manufacturer is 20 - 100W but is 25W from the amp enough for moderate listening volumes without pushing/strain to amp or speaker(s)?

As you may have guessed I'm no rocket scientist but then I don't consider myself a moron but the tech-side of this has me rather confused 

Cheers,

Steve

Amp & Speaker Compatability

Reply #9
With two 8 ohm speakers in parallel you need to know what is the rated output power of your amplifier into 4 ohms. This power is then divided equally between the two speakers.

For example, if the amplifier is rated at 100W into 4 ohms then you get 50W into each 8 ohm speaker.

 

Amp & Speaker Compatability

Reply #10
Quote
Please bear with me on the wattage - using both A+B is a parallel circuit resulting in the ohms per speaker halving; would that not also make the 100W channel essentially 50W per speaker...
You amplifier is rated for 50W per channel at 4 Ohms.

Let's just consider one channel (left or right)...  As you know, two 8-Ohm speakers in parallel are 4-Ohms.  With 50W total, that's 25W per speaker.  With one 8-Ohm speaker, you'd typically only be able to get half the power out, so you'd still be getting 25W per speaker.

Back to that "constant voltage" concept...    It's like the wall power in your house.  You've got 220V (or 240V?) at the wall socket at all times.  If you plug-in one 100W lamp, that's 100W.  If you plug-in another 100W lamp (in parallel), that's 200W.  At some point, if you plug-in too many lamps you "pull" too many amps and blow the breaker. 

A 50W lamp has higher resistance (impedance) than a 100W lamp.  The resistance/impedance is resistance to current flow.  The lower the resistance/impedance, the more current (and power) you get (assuming the voltage stays constant).

Quote
If so, I know the recommended range by the speaker manufacturer is 20 - 100W but is 25W from the amp enough for moderate listening volumes without pushing/strain to amp or speaker(s)?
I think so.    You never really know in advance...  If you know how loud you want to listen (in dB SPL) and how far you'll be from the speakers, you can check the speaker's sensitivity/efficiency and make an estimate, but usually in a home situation you just have to guess.   

The ceiling speakers in a grocery store are typically running at less than 5W each, and that's the maximum when they are making an announcement.    The background music is probably less than 1W per speaker.


BTW - Polk has a good reputation, but those speakers are rather expensive!    Personally, I'd get something like this or this, especially if I didn't have a chance to listen to the speakers before buying...  Maybe if I heard the Polks and they sound really great, I'd be willing to spend more money.  (The cheaper speaker I linked to don't come with a mounting kit, so you'd have to buy that separately.)


---------------------------------------
And, just to overload you with technical information....  Power (Watts) is calculated as Volts X Amps.  You plug-in that 2nd lamp, or the 2nd speaker, you get twice the current (amps) and therefore twice the wattage.    And with a 2nd lamp or speaker, the net resistance (impedance is cut in half).

 
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