Impedance, Efficiency, Watts...Fetal Position. - AVS Forum
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post #1 of 9 Old 07-15-2013, 04:24 AM - Thread Starter
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Hi everyone,

I recently moved into a new apartment and am working on building a stereo system for a living room that is on the humble side of moderately sized. The room has a bar, and above it are four holes (front facing in a line) cut into the wall to accommodate 4 front facing bookshelf speakers that the previous inhabitant installed. I suppose I am looking to recreate the same setup, but better. On the opposite side of the room is a coat closet that is door less, (old Victorian style) in which I plan to discreetly place a powered subwoofer. Now to the problem. Firstly, I'm on budget, so the idea would be spend the least of amount of money and get obviously, the loudest and best quality sound I possibly can (everyones goal I suppose). Second, I haven't ever divulged into the world of stereo so I have no idea what I'm doing. I have a Sony STR-K502 receiver and want to purchase 4 bookshelf speakers, but I have no idea which speaker specifications would be ideal. The receiver is rated 100 watts per channel (RMS?), 8ohms, and 20-20,000hz. Not entirely sure what Im describing, but the exact specifications can be found here http://www.manualowl.com/m/Sony/STR-K502/Manual/66670?page=46 on pages 46 and 47. I've been trying to look into purchasing speakers but I am deathly afraid of burning out the amp in the receiver, or worse damaging the speakers Im about to invest in. I am unsure if it would be best to purchase speakers rated for 100 watts, or above, or even in that range for that matter. I read that even if thats met correctly, you can still have poor sound quality because of the efficiency. Im pretty confused at this point, any help would be greatly appreciated.Thanks in advance!

-Austin
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post #2 of 9 Old 07-15-2013, 10:41 AM
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For a modest system powered by a AVR that is all about budget, it is hard to beat Polk speakers. You didn't say how big the holes for your speakers are but I would assume they are sized for small bookshelf speakers - maybe these Polk 35B at about $75 each:

http://www.amazon.com/Polk-Audio-Monitor-35B-Black/dp/B009WSLBJK

I have seen clearance prices on these several times so you could shop for some small bookshelfs and get an even better deal so that you could afford a really great sub. Just realize that running 4 speakers from that budget AVR will be taxing its amplifier especially with its 8 - 16 Ohm rating so you will need to wire the speakers in series to get 16 Ohms (+ speaker output of AVR to + terminal of first speaker, - terminal of first speaker to + terminal of second speaker, - terminal of second speaker to - speaker output of AVR) - that will prevent a speaker load too low for the AVR's ampifier to handle.

Speakers in series like this will not play as loud with a given volume setting as a single speaker because the impedance is higher and the amplier won't put out as much power. You may have to turn the volume way up - it is hard to say if the additional volume from two pairs will overcome the lowered volume. The good news is that the load on the amplifier would be an "easy" load and it would never overheat. I guarantee if you connect two pairs of speakers to this Sony AVR in parallel for a 4 Ohm load (both + and both - to correct outputs on AVR) the amp section will overheat and shut down unless you keep the volume VERY low - even my freind's Sony ES AVR has this problem and it even has a 6 Ohm switch on the back.

Or you could just use one pair of speakers and put the extra toward a better sub. I recommend one of the new budget SVS models - look online at SVS.com

Good Luck
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post #3 of 9 Old 07-16-2013, 06:11 AM - Thread Starter
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Hey, Mtn thanks for your help so far. Its much appreciated. Well it appears that holes were made to accommodate speakers that had dimensions similar to the following 5-9/16"W x 9-11/16"H x 8-7/16"D. In accordance with those sizes I've found a few different rather budget friendly speakers that fit into those spaces that I will list below. I really don't want to leave any of those holes without speakers, considering it will throw off the symmetry of the room quite a bit. Which of the below would be the loudest (without damaging anything) when linked to my receiver in a pair of 4? And what exactly is 2 way (MTM)? Thanks again!

http://reviews.cnet.com/separate-speakers/dayton-audio-b652/4505-7869_7-35265150.html

http://www.parts-express.com/pe/showdetl.cfm?partnumber=303-400

http://www.parts-express.com/pe/showdetl.cfm?partnumber=300-670

http://www.parts-express.com/pe/showdetl.cfm?partnumber=302-019

Throwing this one in simply because it fits the space requirement, but is rated for 400 watts!?

http://www.parts-express.com/pe/showdetl.cfm?partnumber=310-2268
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post #4 of 9 Old 07-16-2013, 03:57 PM
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Wow - those are really small openings. You are going to have a hard time finding speakers that small that put out much sound. I would stay away from the BIC or the Pyle, especially the Pyle. Obviously that 400w rating is pure fiction. Some thoughts:

A 5 1/4" woofer should be minimum but none may fit - you might need to go to a 4" model
Look for a wood or metal cabinet - more rigid / usually sound better than plastic speakers
You may need to look at metal indoor / outdoor speakers - they tend to be smaller
If there is a port, it should face forward so the sound isn’t trapped behind the speaker
Bass will require sub - for a super budget sub look at Amazon's Polk subs - OK for $100

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Originally Posted by Szumaj View Post

Which of the below would be the loudest (without damaging anything) when linked to my receiver in a pair of 4? And what exactly is 2 way (MTM)?

The loudest speaker will have a higher efficiency / sensitivity - higher the number the louder the speaker (if you can believe the ratings). 2 way means there are two drivers which handle two different frequency ranges - in this case a tweeter for highs and a woofer for mids. MTM is a speaker with Mid - Tweeter - Mid arrangement of drivers (D'appolito speaker) – those aren’t going to fit those openings either.

This is the most sensitive speaker you linked that also has a front port - but according to your measurements it won't fit:

MTX Monitor 5i 5-1/4" 2-Way Bookshelf Speaker Pair
Sensitivity: 88 dB 2.83V/1m
Dimensions: 10 1/2" H x 6 1/2" W x 8 1/2" D.
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post #5 of 9 Old 07-17-2013, 03:16 PM - Thread Starter
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Thanks, MTN you've been a life saver. One last inquiry here hopefully, I found these speakers that fit and are rated pretty high in terms of reviews http://www.amazon.com/Micca-MB42-Bookshelf-Speakers-Tweeter/dp/B009IUIV4A/ref=pd_cp_e_0 . They are however rated 4-8 ohms? I don't quite understand how speakers can have range of impedance as rating, I am aware that it fluctuates with frequency but as a rating? Will they be okay with my 8-16 ohm receiver at its supposed 100 watts per channel rating? Should I give up on the idea of running four speakers, or could I possibly run these in series in stereo mode and still achieve decent results considering the impedance? Since they are in stereo will I be limited to 100 watts for all of them? Speaking of subs, I have one its a Yamaha YST-SW80 http://usa.yamaha.com/products/audio-visual/speaker-systems/subwoofers/yst-sw80_black__u/?mode=model. Will it still fire in stereo mode? Thanks, again I can't express how much I appreciate the help.
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post #6 of 9 Old 07-18-2013, 12:08 PM
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Actually, a 4-8 ohm speaker would be ideal for running two speakers per channel in series on your AVR. The two speakers in series will be 8 - 16 ohms combined which matches the rating of your AVR and won't be too low to cause over-current / over-heating issues but also won't be so high that the current output is limited (and therefore the power output won't be limited).

Did you find any outdoor speakers with thin metal enclosures that would fit? These look very promising at only $58 each:

http://www.amazon.com/Polk-Audio-Atrium-Speakers-Black/dp/B00378KMF0

Quote:
Originally Posted by Szumaj View Post

I don't quite understand how speakers can have range of impedance as rating, I am aware that it fluctuates with frequency but as a rating? Since they are in stereo will I be limited to 100 watts for all of them? Speaking of subs, I have one its a Yamaha YST-SW80

I agree it is strange how some mfg's spec the impedance as "nominal" and others give a range. Ideally, a range would me the minimum and the maximum, but that probably isn't the case - here it probably means that they are "compatible" with an amp that can drive 4 ohm or an amp that can drive 8 ohm loads. Again, if you are using 2 per channel in serial it will double the effective impedance so you shouldn't have a problem.

If your AVR has true bass management (for stereo and multi-channel), set up the speakers as "small" and connect the sub to the LFE output. Unfortunately, very few AVR’s have this and only do bass management for multi-channel. I looked in your manual and like most AVR’s it doesn’t really say one way or another – you will just have to try it. If it only sends a signal out the LFE for multi-channel usage, you can just run the speakers full range and connect the sub to the speaker wires and use it’s crossover to blend them so there isn’t too much overlap.

And as for the power handling, when running two speakers in series each will only see 1/2 the voltage so the power handling is increased - you won't have a problem there either. Just remember that if you turn up the volume until there is audible distortion you could still damage your speakers.

Good Luck
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post #7 of 9 Old 07-22-2013, 04:44 PM - Thread Starter
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Thanks again. I am considering those out door speakers seeing as the ones I want have gone out of stock on Amazon. So the question being how do I wire them in stereo? Can't I just leave the receiver in multichannel and put a pair each in series at the left and right front wire terminals and then I won't have to worry about wiring and the sub? Or will leaving it in multichannel distribute the sound as if three more speakers were connected?
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post #8 of 9 Old 07-22-2013, 10:25 PM
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That's another way you could go if your AVR had a "5 channel stereo" mode - you could use the front channel and rear channel amps to run all four speakers. But according to your manual, your AVR doesn't have that mode so you would have to use "hall" or "jazz" modes which aren't worth while. I would still suggest you run two speakers in series on each channel in stereo mode.
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post #9 of 9 Old 07-25-2013, 10:07 AM - Thread Starter
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I've been doing some research and speaking to people on other forums and it seems my receiver will send a signal to my Sub even when played in stereo mode. So that's good news. The not so good part being that the speakers that suit my room perfectly won't be in stock for 2 months. The speakers that were left in the room are rated at 6ohms. Would it be dangerous to series those and run them until my new ones come in? 12ohms just seems like an odd number, plus I have no idea what the wattage each can handle. Thanks.
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