Need some Amp help - a little new to properly powering speakers

Don't waste your money! Going from 150 watts to 300 will only give an increase of a mere 3db more SPL. And that is at the rated limit of the LSIM707's! If you want more clarity at lower volume you need two things: a better speaker and a better amp.I suggest a pair of Quad Electrostatics with Quad amplification! Buying either Emotiva amp is a waste of money! And will not give you the desired clarity. Your Polks and the Yamaha receiver are the limiting factor - typical mid-fi gear! 

@moskaudio You are wading into a subject that will reveal different opinions fairly quickly. I try to get as much quality wattage as I can into my speakers without endangering either them or my hearing. My reasoning is akin, I think, to what you are expressing. For example, my speakers recommended amplifier power is up to 350W (8 ohms). I drive them with monoblocks rated at 430W (8 ohms). I have heard the speakers with an integrated amplifier (by the same amp manufacturer that makes the monoblocks) rated at 1500W per channel and they sounded great, although not as good as how they sound with the monoblocks, IMO. I would describe the effect as the amplifier seeming to have more reserve to allow dynamic recordings to sound abundant while maintaining excellent attendant speed. Of course, you don't want to crank the volume past a certain point or you will be buying new speakers. In sum, I think I'm practicing your assumption and I find it satisfying. And FWIW there is nothing wrong with your gear. It is your ears that hear it and if you enjoy the sound being produced that should always be what matters most.  

I can see that. I figured a fairly expensive flag receiver would produce decent quality power but I guess I should try hooking these up to a 100watt per channel rotel amp I have and see how it sounds.

Don't worry about the 300 watt rating on the speakers. That is a max level and no indication of what is needed to drive them in a particular sized room. If you can attain the volume levels desired and are happy with your amp/speaker combo then enjoy.

What Rob and others said. Although, I guess he was joking about the Quads. Your rig sounds pretty good at high volumes but giving it bigger amps will only make it a little louder. You need to get better quality gear to make it sound better at lower volumes.

Agree with the sentiment of pursuing higher "quality" amplifier (true for all audio products make quality the priority ) rather than higher power. 

i agree with the foregoing sentiments (which makes me re-think why i'm posting...). more watts, as opposed to higher-quality watts, won't really help. your yamaha seems like a good match for your speakers; you seem to enjoy it and i'd be inclined to leave it as is.

I don't know of any proper test of the Yamaha, but it may well be pretty good (and not mid-fi) if it compares to e.g. the Yamaha AS700 tested here: http://i.nextmedia.com.au/Assets/Yamaha_AS-700_Amplifier_Review_LoRes.pdf
The need for power largely depends on the music you play, the size of the room and the sensitivity of the speakers (88dB in this case). Unless the room is very large 150 watt per channel should be OK, even if (up to a point) more is always better (for cleaner response to dynamic peaks). More amplifier power does not need to cost much, of course. Better speakers would make a bigger difference, but will cost significantly more.

FWIW, Polk in general are looked down upon by audiophiles with some good reasoning. Vintage Polk not so much as they were much more suited for the audiophile world. Polk headed in a downward spiral after they courted the mass market and nothing they produced after could match their vintage products. I am currently, and have been for years, running an HT system with all vintage Polk speakers powered by an Emotiva XPA5 and a Lexicon processor.  That said Polk speakers require some power to make them sing but 250w is more than enough to get there with plenty of headroom to spare. It' kind of ironic that you should be driving the speakers with a Yamaha as I experienced similar issues when I had mine mated with a Yamaha processor. The yammy had to go. I also strongly suggest fixing your listening environment before spending a lot of money on equipment. Nothing you buy will sound "right" until the supporting environment is corrected. Doing that will save big future dollars. You might also find it solved your immediate problem. Just saying.  PS: Emotiva does make exellent and affordable equipment in its price range. It will never compete with the higher end equipment and it is not meant to.

Emotiva won't solve your problem.  They are inexpensive amps that try to border on high end.  Your Yamaha receiver probably sounds as good.  You need to go to a better brand and there are many out there at the price of the Emotiva.  I speak from experience as I owned that brand at one time.

I gave them a shot this morning with a Rotel RX-1052 stereo receiver i had laying around. 

I know this is also just mid-fi gear but the polk lsim707s sounded much clearer at lower levels with the rotel stereo receiver even though it is rated at 100 watts per channel. The bass was also less flat. Kindof surprising. 

But yes I know I'm playing with kiddie toys here =). It's hard not to bite when there's a $2,800 sale for 2 polk LSIM707s towers, 2 polk LSIM703s, a polk LSIM706C, and a $1,500 yamaha aventage 3070 receiver that some sites rated as the best home theater receiver of 2017. Seemed like a no brainer.  

After reading all of your commends I would have to agree. I think I will be leaving the powering of these speakers alone, and move towards higher end speakers and gear before giving the amp anymore thought. In a few months I will probably Ebay the bookshelves and center off new in box, and work towards a pair of Kefs or Martin Logans. 

I notice at lower volumes a lot of the imaging and clarity disappears.

That's a problem with the Yamaha. Going to higher power won't help it.

There is this thing called the 'first watt', which is the idea that the first watt of power is the most important. Apparently the Yamaha isn't doing that bit fairly well. I suspect if you look at its specs, at lower power levels the distortion might be quite a bit higher than at higher levels.

Better quality amplification is better at that problem. If you go with tube gear, even better...

No it is not a problem with the Yamaha but with human hearing. Louder will always sound better. Did anyone bother to look at the test results for 1 watt that I posted? Here, for data on an even cheaper Yamaha, the AS 500, the predecessor of the current AS 501 that now also has digital inputs: http://i.nextmedia.com.au/avhub/australian-hifi_reviews_2014_2014-02_yamaha_as500_amplifier_review_a...

Apparently it is the Yamaha. The OP just posted above that lower volume sound quality improved significantly when the Rotel replaced the Yamaha component. OP, I would heed the considerable knowledge/wisdom of atmasphere. He’s absolutely right in that high quality amplifiers sound very good in their "first watt" range of power. Providing more power from a lesser quality amplifier (poor first watt performance) won't solve the problem. 
Charles 

Such comparisons are only valid if the level is equal within 0.2 dB. For that you really need a volt meter.

Your speakers are of relatively low efficiency. That's the issue, not power or quality of power. As willemj pointed out, unless you level matched the Rotel and Yamaha for your comparison, it's likely the Rotel was playing at a higher volume when you perceived the improvement.

If you want low volume dynamics, you simply need speakers of high quality and greater efficiency. 

Moskaudio (OP) didn’t say the Rotel played louder. What was  pointed out is that the Rotel played at lower volume levels was "clearer"`(and better bass) sounding than the Yamaha at similar lower volume. This would suggest that the intelligibility was improved with the Rotel driving the same Polk speaker. This indicates the Polk is capable of better low volume performance when a better amplifier was substituted.

The Polk wasn’t the limiting factor, it was the Yamaha and its limitations. Can you improve beyond the Polk speakers? Yes you can, you can also go further in quality than the Rotel amplifier as well. Some people downplay the importance of high quality amplification and this is an error. Speaker quality matters no doubt but the same can be said for quality power amplifiers. [ can recall experiences where merely changing only the power amplifier resulted in substantial sound quality improvement. 
Charles

Moskaudio
Atmasphere mentioned tube amplifiers in his reply to you. You Polk is rated at 88 db sensitivity and an 8 ohm load. It would be very informative to listen to your speakers driven by a good quality push pull tube amplifier of suitable power. You may find they have more to offer  than you're currently experiencing with the solid state receivers, 
Charles 

@kosst,

The OP stated that it "sounded much clearer at lower levels." He did not say it played "louder."

The fact of the matter is that a fair comparison of amplifiers requires matched levels.

High efficiency speakers manage greater low-level dynamics for a given volume.  His original post stated that he noticed a lot of "imaging" loss at lower levels. Maybe he was referring to imaging in the true sense of the word, but I'm betting that dynamics is the more appropriate adjective. I've never had an issue with low-level imaging, but all mid-efficiency speakers I've owned struggled to produce decent dynamics under 70db, regardless of the paired amp.

 I know...I know...you'll tell me I've never owned any decent speakers and that I apparently haven't heard the Focal Arias...

You do not need more efficient speakers for more detail. The most detailed speakers may well be Quad electrostats, and they are horribly ineffcient. The Harbeth range is also very detailed, at both high and lowe levels, and they are not particularly efficient either. All that such speakers need is power, and the more the better.

@Helomech, dynamics are the more appropriate adjective. There was some mid range and high range loss, but anything below -35DB on the Yamaha receiver (150 watt @8ohm) (which again, is a $1,999msrp receiver), had a LOT of dynamic loss.  

Then when paired with the Rotel Receiver (100watt @8ohm), the dynamics were more apparent at lower volumes. As the Receiver measures its volume in DB, the Rotel does not (0-100). Around 30, the Rotel receiver brought out more dynamics, and mid ranges that sounded lost with the Yamaha, at what was a much lower volume. 

I'm pretty new to this, but overall after doing some DB sensitivity research and other things, it's pretty safe to say that Polk LSIM707s definitely aren't the most responsive towers on the market. 

However, @Charles1dad, I think I'm gonna give a tube amp with them a shot. Seeing as how I'm new, the experimentation would be fun =). 

@Charles1dad, what tube amp would you recommend in or under the $1000 range? I don't mind buying used audio equipment on Ebay. I do however live in Oklahoma and needless to say....there isn't a whole lot of after market trading here. 

Also, I feel the need to thank everyone who has posted their opinions and thoughts here. 

It has helped broaden my understanding. I also read the research on the 1watt charts that were posted. I then looked at the emotiva amps and as someone posted above, I'd basically be throwing the same power that the Yamaha receiver is already producing which would indeed be a total waste. 

It is much appreciated 

Very few have done wrong by using tubes over transistors. My (now unused) 70watt KT88 tube amp drove my Spendors to deafening levels with serious bass. The Polks being 88dB at 8R should sound great with even a 30w integrated tube amp especially if the OP isn't cranking it.

Amojan,
It was atmasphere who made the positive comment regarding tube amplifiers in his post yesterday. Did you not see this? I personally believe that the key issue here is amplifier "quality " be it tube or transistor. People suggesting just get a more powerful amplifier (quantity) and throwing more watts at the speaker aren't  helping moskaudio (OP).

Moskaudio, I don’t have experience with tube amplifiers in that particular price range. I would look into known reputable brands such as Cayin, Quicksilver and Primaluna on the used market. Those 3 come to mind but I’m sure there are other candidates as well.
1 Regarding tube amplifiers qualify output transformers and power supplies are essential for good sound and performance.
2 Push pull topology with minimum 30 to 35 watts and up (assuming good quality) should work well for you. If you have to exceed the budget a "bit" I’d do it to ensure that the quality of the amplifier is good.
Charles

Although I almost always agree with my esteemed Audiogon friends and colleagues Atmasphere and Charles, and although I am definitely a fan of tube amplification, I would be hesitant to pair a tube amp with these speakers, at least without an in-home trial having return privileges.

While the speaker’s published specs indicate a nominal impedance of 8 ohms, the measurements shown here indicate as follows:

Impedance reaches a minimum of 3.75 ohms at 66 Hz and a phase angle of –47.96 degrees at 83 Hz.

While that information is not nearly as complete as I would have preferred to see (a graph of impedance magnitude and phase angle covering 20 Hz to 20 kHz would have been more informative), it is suggestive that these are probably not tube-friendly speakers, especially when it comes to tube amps in a price range that would make sense. (As opposed, for example, to a vastly more expensive Audio Research Reference series amp, which I suspect would do ok with these speakers).

The problem with the 3.75 ohm figure is not necessarily that value in itself, but rather that given the 8 ohm nominal impedance there is likely to be a wide **variation** in impedance between the bass region and the impedance at higher frequencies. And given also the likelihood that the speaker was designed with the expectation that it would probably be driven with solid state amplification that variation is likely to result in unintended tonal aberrations, such as weak bass, if it is driven via the higher effective output impedance of most tube amps.  And the fairly severe -47.96 degree capacitive phase angle at 83 Hz would most likely add to the problem.

I can also say specifically that based on measurements I’ve seen in Stereophile many PrimaLuna models, especially the lower priced ones, have particularly high output impedances, even for a tube amp, which casts further doubt on their suitability for use with these speakers.

Good luck. Regards,
-- Al

@Almarg even more light shed and more difficulty added to the mix =).

Although, this would make sense. The tweeter and small mid woofer appears to be the same exact design as the LSI25s, which are rated at 4ohms.....most likely due to the woofer being self powered. 

So many fun things to play with =D. Now.....to study up on capacitive phase angles at certain critical sound frequencies.....

You do not need more efficient speakers for more detail. The most detailed speakers may well be Quad electrostats, and they are horribly ineffcient.

The first statement is true, the second is partially false. Quads are planar loudspeakers, and so the 1 meter measurement does not give their true efficiency. In general you can add 6 db to the measured figure and be a lot closer to their actual efficiency. This is true with any planar. 

Al, If a tube amp were used on this speaker, it would probably do fine if used on the 4 ohm tap and if also running about 20 db of feedback. The impedance curve would then present no worries.

I only mentioned a tube amps simply because the OP is dealing with a lower volume loss of detail. Low level detail is something that tubes can do considerably better than transistors. IMO this has to do with the linearity of the devices themselves; even pentodes are not that bad at lower power levels.

@kosst,

You completely misread my post. I was speaking of low-volume dynamics. I don’t know how you confused my statement unless you simply read it too fast. This is what I said,

His original post stated that he noticed a lot of "imaging" loss at lower levels. Maybe he was referring to imaging in the true sense of the word, but I’m betting that dynamics is the more appropriate adjective. I’ve never had an issue with low-level imaging, but all mid-efficiency speakers I’ve owned struggled to produce decent dynamics under 70db

Since you mentioned LS50s, I happen to own a pair, and they, like other low efficiency speakers, have weak dynamics at low volumes. It doesn’t matter if one feeds them tube, SS, class A, or AB power, nor does high or low damping factor make a difference. They simply need a certain level of voltage to open up and that means louder volume.

Anyway, the OP subsequently confirmed what I suspected, that he was actually referring to dynamics, not detail or imaging.

What folks here seem to fail to comprehend is that many listeners want the same "jump" factor (mostly regarding bass) at low volume that they get at higher (80db+) volumes. Amp manufacturers began to compensate for this with "loudness" controls once low efficiency speakers became the norm. Then the movement toward minimalism and home theater came about. AVR manufacturers know that most will only use these products for home theater, so inclusion of a loudness control is no longer worthwhile. The boutique minimalists swear that any such control compromises the sound, and/or the BOM for the rest of the amp. That leaves one the option of using separate DSP, an EQ, or high efficiency speakers to attempt to compensate for the loss of low-level dynamics.

Any honest speaker designer will attest that high efficiency speakers produce superior dynamics at low volume. I know you don’t like to read that based on the speakers you own, but it’s the reality.

I own both high and low efficiency speakers. I don’t consider either approach inherently superior. Each approach has strengths and weaknesses.

Hi Al,
 Thanks for the additional specifications,  I was relying on information from the Polk website. "If"  the tube amplifier has good quality transformers and power supply (PS) I feel the same as atmasphere.  This type of tube amplifier using its 4 ohm tap has a very reasonable chance of success. Atmasphere's recommendation for about 20 db of NFB (or thereabouts) makes sense as this would lower output impedance and conversely increase the DF (Damping factor). 

Meeting this criteria and the need for quality transformers/PS is the challenge for the stated budget for such a tube amplifier. 
Charles 

30 watts was a minimal recommendation to provide moderate/reasonable listening levels. All 30 watt amplifiers aren’t created equally. There is a hierarchy of quality that definitely exists. For example I would be confident that the VAC Renaissance 30/30 amplifier (excellent output transformers and PS) could drive this speaker from its 4 ohm tap and produce beautiful music while doing so. Problem is you won’t find a used one anywhere near 1K dollars. A used Cayin, Line Magnetic or Quicksilver in the 50 watt range push pull class A/B would work pretty well I believe. Interesting thread.
Charles

Moskaudio, am I to understand that you are now considering replacing both the speakers and the amp and going to a 2 channel system? If so I would suggest that you search out the desired speaker first, pair them to your Rotel stereo amp, which seems as no surprise to me to be superior to the Yamaha AVR, while your explore the market for an upgrade in amplification. Finding speakers that are at least moderately easy to drive maximizes ones budget towards amplification. 

@moskaudio What one needs to understand from the get-go, is that the number of watts is only one part, one quite small part, of the story.  For starters, take a look at the current output rating (not all manufacturers publish) and the damping factor.  Generally speaking for both, the higher the better.  Then you get into the jungle of class A vs. AB vs. D, and solid state vs. tube.  So not even two amps with identical measurements on all those parameters will sound the same hooked up to the same set of speakers.

DF (Damping Factor) desirable level really depends on the speaker in question. Some speakers definitely require more than others, some speakers require very little DF. Too much DF can be detrimental to sound quality. There’s no such thing as the more DF the better in every circumstance. Increased DF reflects an increase in NFB and there can be undesirable  sonic effects as Atmasphere has  eloquently explained in past posts.
Charles

As for the Quad electrostats. Right now I am listening to my 2805s driven by a 2x140 watt Quad 606-2, at almost full power. The sound is glorious, but to be honest, realistic level would require more power. For a larger listening room like mine Quad's UK engineer recommended their 2x260 watt QSP monoblocks. They are on my wish list. The modern 2805's are far less sensitive than my older ELS 57s.

Too late to correct: QMP monoblocks. The QSP is the modern equivalent of my 2x140 watt 606-2.

@willemj , I think you might be confusing sensitivity with efficiency. They are not the same; the latter is based on power and ignores impedance, the former is based on voltage and impedance thus matters quite a lot!

Now if you are driving a larger room, you will need serious power regardless. If that is the case, you might consider a set of Sound Labs, as they are better at playing the higher sound pressure levels you might need in a larger room.

Many good suggestions here, two that stand out are:

If you increase power and keep the same mass market level of product, you will hear little improvement.  Be sure to go up in quality vs. power, you will hear the difference.

You should audition a good quality tube amplifier.  Tubes have a different sound that many of us prefer.  My preference is for Conrad-Johnson products in both areas, many c-j amps are available on the used market.

Enjoy the search...

@moskaudio     

I hope all of this hasn't been too confusing.  To directly answer your question... No, you do not need more power simply because a speaker can handle that much power.  You might have seen that others quoted that you have an 8 ohm speaker that is rated at 88db sensitivity.  What that tells us is that you could get away with as little as 30 watts per channel, if the amplifier is built well enough to give you that full rich sound that you seek with higher power.  One thing that I have found is that on lower priced items, that it does require more power supply to create more power, so because of that, more powerful amplifiers can often sound better at low volumes,  but overall, If an amplifier is well designed, then you don't necessarily need much. Your Yamaha is a fine receiver, but it is not in the realm of good audiophile equipment. With that, I might recommend a good receiver like maybe an Outlaw or maybe a 50 to 100 watt integrated amp, a used Audio Refinement or Arcam would do a great job.... There are a ton of good integrateds.  If you like that Idea, you'll get plenty of suggestions.  I've heard your speakers, set up properly with good amplification they are a very satisfying sound.  I hope this helps, Tim 

How happy are you with the sound of the Polk/Rotel combo? 
If you are not yet satisfied; I'd try 'better' speakers with the Rotel, first. 
I'm talking only about 2 channel music here.
I had a Rotel RX-1052 powering old Boston Acoustic T-830 acoustic suspension speakers. That combo sounded great at low volumes. I later upgraded to Canton Ergo 1002 DC bass reflex design larger towers. They need to play quite a bit louder to get everything out of the music. Both are rated at 90 dB @ 1W @ 1M, but the Cantons actually play louder at the same volume setting.

Tim,
We have a similar assessment of moskaudio's current audio system. The speakers are pretty decent and will respond to better quality amplifiers. The Yamaha receiver is the relative weak link in this system. Evidence is that  lower level sound quality improved noticeably when the Rotel replaced the Yamaha. I do believe that moskaudio has recognized the necessity for moving toward a amplifier of "higher quality ". There’s more potential with the Polk speakers to be gained.
Charles

Hello moskasudio,
   Let me start of by stating that my technical knowledge can be fit into a thimble,and still have enough room for a thumb!  That being said,how large of a room are you listening in? Also,how far are you seated from your speakers?  That information should be quite helpful. 
      
       Ray

The very first thing you need to know is that wattage rating on loudspeakers tells you exactly zero about how they sound.  All it tells you is that if you exceed that wattage, you can fry your loudspeaker.  

I think your current setup is actually quite well matched.   People who reside on the Audiogon forum will pretty much universally dislike both Japanese receivers and Polk Audio loudspeakers, but if you enjoy what you're hearing, then keep enjoying them.

If you really want to move up, then begin by listening to as many other loudspeakers as you can.  Visiting the local audio showrooms is OK, but your best bet is to meet other local audiophiles and listen to what they have.  Learn why they made the choices they did, both in loudspeakers and amplification.  

I have plenty of opinions myself, but what you really need to do is get more experience with the gear others own.