The two most common mistakes are bass and treble

Why is it that speakers with 90-98 db efficiency but steep phase angles and impedances in the 3 ohm range for bass can sound superb with well designed 30 watt amps?  I also prefer more efficient speakers but have recognized that low efficiency speakers (mid-80 db) with benign phase angles and nominal 8 ohm impedances are just as good and easy to drive.   Only a few high end box/dynamic speakers are both efficient and have 8 ohm nominal impedances.  The room acoustics are so important to the reproduction of sound and musical pleasure that this discussion of bass and treble seems banal.  There are many ways to make a good match between speakers and amps that no one method is "best."   

Btw, we have to remember too that speaker/amp manufacturers depends of what the parts suppliers/manufacturers have on hand/offer.

R.

Dear @erik_squires : Probably not to have clear what he is looking for that could satisfy that gentleman.

An audiophile that wants to buy a new speakers must have defined his targets about, each one of us have a " little " different audio/MUSIC kind of sound that we like it and our priorities about just are different too.

After that he needs to made his own research through the " infinite " audio forums in the internet and the digital speakers reviews by magazynes as TAS or ST or many others. If all those is not enough for he can has 3-4 speaker alternatives to look for then start a thread in Agon or other forums looking for whole advice.

I think that after all those the key to decides about is to have the opportunity ( looking for. ) to listen the speakers at his place that several times is not posible to do it.

Yes, a rookie normally made all mistakes you posted and several of the ones other gentlemans posted in the thread.

Bta, @clio09 posted " We’re not going to see a huge spike in the manufacturing of high impedance, high efficiency speakers anytime soon just because it’s the better method. "

Certainly not. It’s stupid to think that today SS electronics are designed like in the very old times. SS electronics has no problems about, tube alternative is " touched " by all those problems and that’s why are crying for what you said clio.

From more than 10 years now the SS electronics designers are improved its designs and they design for " any " kind of characterisitcs of almost any speakers in the market. Even today we don’t read threads in the audio forums talking of today SS clipping in amps due that the designs comes with a wide headroom.

In the other side today speakers designers know everything to avoid all the in theory " problems " posted here with their designs. Again is stupid to argue about. Of course that do not exist the perfect speaker always there are trade-offs  down the whole design and those trade-offs are not only by thechnical aspects but with some limitation because the manufacturer designs for a market's price.

Gentlemans we are living in 2021.

Btw, audio distributors/dealers improved its quality service/advise to the customers too because they want sold their products but at the same time they don’t want it to " buy " problems with their customers.

As any other activity the whole audio community improved/enhanced over the years and customers too. Obviously that nothing is perfect down there and could be some kind of " problems " with rookies/newcomers but nothing dramatic or critical.

Today people is better informed if know from where take the information, something that’s easy to do.

Well, at least all those is my take and an additional opinion here.

Regards and enjoy the MUSIC NOT DISTORTIONS,
R.

Within a specific power envelope ?

The other problem you deal with is of course that you get thermal compression if the speaker lacks efficiency. You can’t solve this by getting a more powerful amp

No, you can solve it by various aspects of speaker driver and crossover designi. I don‘t think anyone could state that the ATC SCM50 (85db/W/m) suffers unduly from thermal compression. There are many other manufacturers who are cognisant of the impacts of thermal compression and design their drive units accordingly.

We make amps from 30 to 500 watts. And certainly, anyone *could* state that the ATC SCM50 (85db/W/m) suffers unduly from thermal compression.


You can't solve thermal compression via crossover design or internal amplifiers for the loudspeaker system. Thermal compression is a function of the voice coil itself.

Rather than explain how this works I've linked a Wiki page below.


This is not mysterious; thermal compression has been a known thing for a long time. https://en.wikipedia.org/wiki/Power_compression

I even see I. Audiophile community- referring to the same 3-4 brands of “high end” speakers over and again when they describe their systems.  

Baby got Back.

I like speaker than can follow gentle harmonic structure and textures on Indian Girl by the slick Rick.

You're a legend in your own mind.

IMO to many people do not have a clear understanding of what bass actually is. Bass should be what the artist and producer have made it as part of the whole sound. Most artist have what I would call tight bass guitar that harmonizes with the drummer. This is where you need to separate bass into the multiple categories that it is. A kick drum I want to feel like a punch to the gut, a bass guitar I want to provide a solid tight rhythm to the track. What really confused most listeners was when Tool and others introduced drop D tuning. This lead listeners to think all songs should play down there, but they don’t. To many time people want to over produce “all” bass and you end up with mud or a lot of uncompressed vibrations. This is very common in hip hop as it masked over the crap sound of everything else that is all just over sampled tracks they borrow. Then you also run into the track production. If the artist and produce did not put the bass in you can’t make it appear out of thin air and expect it to sound good. Yes different speakers make bass in different ways but in the end you want to hear what the artist gave us. Everyone wants to be or thinks they are “producers” and can or could have done better. I think speakers and their numbers should best the main type of music you listen to. If a Marshall bottom is running 8 ohm and 90 db on most music I like I want my speaker to try and reproduce the sound the artist has made.

@clio09 I wasn't really saying you were wrong, nor did I feel that you were saying that I was either, but I felt from your comments that I should flesh some things out a bit more. I agree with everything Roger states from your comment above. Despite conversations like this nothing is going to change; although people reading this might be a tad more careful.


Older solid state amps tend to run too little feedback which is why they can sound bright and harsh. Driving higher impedances helps with this simply by reducing distortion, which is the source of the brightness.

I think Roger didn't like that we run no feedback in our OTLs but the reason was I knew that if we used feedback, the phase margins of the amps would never permit enough to be applied. That's actually true of every tube amp. So to prevent the dreaded brightness coloration we ran no feedback at all and relied on other means to keep distortion at bay.

Its always important to be careful about conflating personal anecdote with how things are: just because you have one efficient speaker that is bested by others of lessor efficiency does not mean that what I’m saying is incorrect.

@atmasphere I don't believe I was indicating your statements are incorrect. I actually said you made good points regarding distortion and speaker efficiency. My anecdote was strictly to illustrate my subjective preferences. In learning from one of the best engineers in the business who touted that greater benefits could be achieved from his amps if they were light loaded due to lowering distortion, making the amp work more efficiently, and extending tube life, that obviously aligns with your comments. From an engineering and design perspective, this is just the way it works, there is nothing otherworldly about it. That same engineer designed OTL amps. His preference would have been using them with 16 or even 32 ohm loads and he often lamented the lack of speakers being manufactured with those specs. As I told him and as I'll state now, unfortunately the audio world we live in isn't going to change course. We're not going to see a huge spike in the manufacturing of high impedance, high efficiency speakers anytime soon just because it's the better method.

To Atmasphere: I’m on my third pair of low impedance, super-inefficient Magnepans. I’ve had many other brands of speakers - Altec, Allison, Advent, AR, B&W, Definitive Technology, Elac, KLH, Klipsch, and Wharfdale.
In my opinion, Magnepans are the most neutral speakers made, as well as fantastic bargains.

You can imagine with Manapan in my town and being on a first name basis with the owners (one of them called me last summer when my stolen bicycle turned up on Offerup, for which I am grateful) that I’ve heard them a lot . ’Some of my best friends own them’ although a trope is actually also true. They are good speakers no doubt. Imagine though what they might sound like if higher impedance: They would be less sensitive to speaker cables. The amps playing them would have less distortion. In a nutshell, you’d experience more impact in the bass (owing to the speaker cables not robbing you of impact) and smoother, more detailed sound through the mids and highs (owing to lower distortion from the amps).

I think @erik_squires is correct that planars suffer less thermal compression than lower efficiency cone drivers.

In my collection, my best speakers are not the high efficiency Audio Note AN-e or my DIY single driver using an Audio Nirvana driver, they are my Spendor 1/2e, Quad ESL, Acoustat Model 2, and Analysis Audio Omega. None of which should be confused with high efficiency.

@clio09 Its always important to be careful about conflating personal anecdote with how things are: just because you have one efficient speaker that is bested by others of lessor efficiency does not mean that what I’m saying is incorrect. I have a similar anecdote- a set of desktop Coral loudspeakers that I bought at a garage sale for $5; they are 98dB but sound pretty mediocre; the cabinets resonate and they lack definition and bandwidth, entirely because they simply weren’t built to be anything other than cheap. Obviously the Audio Notes are not that but you get my point.


The Quads and Acoustats are not as inefficient as they appear on paper; generally speaking add 6dB to any planar’s measured values to sort out where they actually sit (some amps have trouble driving ESLs which is unrelated to their efficiency). This is because when measured, the microphone is placed at 1 meter. At that distance, a good deal of the output of the speaker is not picked up by the mic. You have be back from the speaker a good 10 feet to really understand its efficiency. ESLs do not suffer thermal compression as they have no voice coils.


Efficiency and impedance are important, but like class A vs AB in amplifiers, a lot has to do with execution. As an amplifier manufacturer that makes both class A tube amps and class D amplifiers, I see how distortion plays out in systems all the time. In solid state, you lose power as the impedance is increased but you also lose distortion. Now if sound quality is your goal then your amplifier dollar will be best served be a speaker of higher impedance; if *sound pressure* is your goal then you have a weak (3dB) argument for 4 ohms.


Higher efficiency speakers require greater precision in their construction, which makes them a lot more expensive. They were the only game in town when tubes were King; speakers had to make the most of amplifiers whose power is expensive. OTOH when solid state became practical, amp manufacturers realized the benefit of no output transformer and no filament circuit- so they could make an amp of the same power that cost 10% of the cost of a tube amp and sell it for 90% of the price of that tube amp. Speaker manufacturers saw this and realized that if they went to 4 ohms and less efficiency the lower cost to build the speaker meant they could make more money too. Solid state amplifier power is cheap, so this has worked great market-wise but its been one of the barriers between sounding like real music as opposed to a really good stereo.

Inefficient and low impedance speakers are IMO/IME a mistake.


All amps make more distortion playing into lower impedance. If you want the amp to sound smoother and more detailed, set it up to drive a higher impedance.


Inefficient speakers need really powerful amps to play properly, and they suffer thermal compression. Really powerful amps that actually sound like real music are not that common and likely pretty expensive, when the whole thing could have been solved without any loss of bandwidth or resolution by simple getting a speaker that's easier to drive.


Speaker cables get far more critical on low impedance speakers too. You can easily spend $$$$s on speaker cables, but if you have a higher impedance speaker the cables simply won't bring as much to the table.

There's truth to this, I find. Obviously efforts have been made by the industry to cover up more or less a progressing deficiency in speaker sensitivity (in tandem with lower impedance) for decades now, as pointed out by John DeVore:

https://www.youtube.com/watch?v=PEcFkSQMc8g

Speaking of difficulty of load though low impedance may be a much lesser issue than what's faced with complex passive cross-overs and their potentially high phase angles. While higher impedance as an isolated phenomenon relieves the amp in a sense, the negation of a passive cross-over, not least a complex one, will have much bigger implications here. Just like with high(er) impedance and its lessening of the importance of cables, the same is offered us going active and the importance here of amps: an important culprit of what make amps sound different lies in the passive cross-overs of speakers, and how well a particular amp is able to remain electrically indifferent to the load presented to it; remove the passive cross-over and amps start sounding somewhat more similar (though not completely similar) looking directly into the specific driver, while seeing their fuller potential much more easily realized. 

Active also means being able to direct more power and quality to where its needed. I have 30 watts pure class-A designated to the 111dB sensitive horns, some 2kw Lab.Gruppen to the 100dB sensitive bass cabs, and 500 watts Crown to the 97dB tapped horn subs. 

I'm sure many don't feel they're making any outright mistakes with their choices of lower efficiency (/low impedance) speakers, and I'm sure many of them have great sound. Coming down to it, that's all that matters. From my chair though speakers have been way too inefficient for too long, and too small and too expensive at that. I simply don't buy into the "small speakers small room, big speakers big room" mantra that's so often leveled at us. It's an excuse to make us buy generally small(er) speakers and make us feel good about it, when most of us don't have bigger spacings allocated for our audio passion. Truth is though big, pro cinema speakers can sound fantastic in a moderately sized domestic setting, even though they're build to fill auditoriums for hundreds of people. Talk about being preconditioned to a certain way of thinking. 

Boiled down the mistake is buying into it all and everything - all this "hifi." Let physics have their say with speakers, be critical of the industry, and keep an open mind - not least a pair of open ears. 

When we talk about speaker distortion and thermal compression I’m not sure it’s fair to lump systems without voice coils like Magnepans with normal to low efficiency cone speakers though I know it keeps happening. The physics of the heat and distortion are entirely different as far as I know.

To Atmasphere:  I'm on my third pair of  low impedance, super-inefficient Magnepans.   I've had many other brands of speakers - Altec, Allison, Advent, AR, B&W, Definitive Technology, Elac, KLH, Klipsch, and Wharfdale.
In my opinion, Magnepans are the most neutral speakers made, as well as fantastic bargains.  

I kind of would really like to hear @atmasphere and Fritz in a room together sometime. I think that would potentially be a phenomenal match up.

Yes it is a nice set up. Fritz and I did a show several years ago with my Atma-Sphere amps and his speakers. We also had a 300B SET amp and it was surprisingly a great match for the speaker. Fritz's speakers are typically 6 ohm and a pretty flat 6 at that, with very benign phase angle. They are not high efficiency either. Duke LeJuene has praised them as the closest thing to a free lunch and I often point out to people they are the best kept secret in audio.

While I think @atmasphere made some very good points about distortion and speaker efficiency (pay attention to his example of the 4 ohm efficiency calculation using 2.83V), there is something to be said for designs that are not high efficiency. In my collection, my best speakers are not the high efficiency Audio Note AN-e or my DIY single driver using an Audio Nirvana driver, they are my Spendor 1/2e, Quad ESL, Acoustat Model 2, and Analysis Audio Omega. None of which should be confused with high efficiency.

The point of using mid to low power amplifiers with high efficiency, easy to drive speakers is not wrong, btw. I don’t disagree with it but it is kind of it’s own sub-genre of audiphilia.

I kind of would really like to hear @atmasphere and Fritz in a room together sometime. I think that would potentially be a phenomenal match up, given Fritz has ruler flat impedance above the bass.

@bjesien

That’s probably the most rational view of audiophile spending as a hobby I’ve ever heard. To set a budget for the amount of money you are willing to go out and play with.

That’s a different take than those trying to get to their final system. My budget there is all tied up in new GIK hardware though, and maybe a new DAC. I have to keep reminding myself that upgrading the room acoustics often makes upgrading the hardware unnecessary.

Of course, one of the most cost effective ways to experiment and learn in this hobby is to make your own from kits. :)

That's also part of my point Erik. Savvy steering can cost non savvy audiophiles money. It all comes down to getting out and listening, or like me, setting an experimentation budget of $X per year as part of the excitement and enjoyment in audio. 

I apologize if I sound like this- I’m coming from the perspective of engineering and as an amplifier manufacturer of the last 45 years.

No problem at all but I wonder how much will change when you are making high power solid state amps instead of mid-power tubes? :-)

All I really asked for was a couple of numbers.

I apologize if I sound like this- I'm coming from the perspective of engineering and as an amplifier manufacturer of the last 45 years.

I've always respected your posts on these forums and have learned a thing or two along the way. You contribute to this forum in a way that makes people see you as an authority. Over time you have created an environment where people know like and trust you.
You are not only an accomplished engineer but a marketing master. It's no coincidence that you have nearly 10,000 posts on a worldwide website ripe with prospects and perhaps the largest percentage of target market tuned in right here daily.
On top of that you make a neat and clean product in the USA and get rave reviews and accolades on your upgrades and product support.  I've never considered one of your products because I don't like the unprotected chassis design. With young kids in the house and nothing being "off limits" it never made sense.
Finally, no need to apologize to me, I'm taking notes. Well done you've earned it IMO.  

Another prime example are my original Acoustic Energy AE1‘s, which are notoriously inefficient, but were designed specifically to combat thermal compression, having their voice coils thermally bonded to the aluminium speaker cones to dissipate heat.

They sound atrocious cold, and really need a bit of warming up before they begin to sound good; sounding better the harder you drive them. They love heat. Their lack of compression at high levels is quite astonishing, even today, and makes nonsense of the idea that thermal compression has to be a limiting factor in low efficiency speakers. Their ultimate performance is mainly constrained by the driving amplifier.

I’m coming from the perspective of engineering and as an amplifier manufacturer of the last 45 years

Within a specific power envelope ?

The other problem you deal with is of course that you get thermal compression if the speaker lacks efficiency. You can’t solve this by getting a more powerful amp

No, you can solve it by various aspects of speaker driver and crossover designi. I don‘t think anyone could state that the ATC SCM50 (85db/W/m) suffers unduly from thermal compression. There are many other manufacturers who are cognisant of the impacts of thermal compression and design their drive units accordingly.

Hello,
I feel so fortunate that the store where I get my Hifi gear lets you try before you buy. A few of my pieces of gear would not have ended up in my system like the Puritan PSM156 or the Nordost digital coax cable. I am excited because they have become the Ayre dealer in the Chicagoland area. Demoing gear in the home is the most important thing you can do. Even if you bring in your gear to the store it will not sound the same. If you are in the Chicagoland area and want to demo things right try: https://holmaudio.com/

Not saying you are incorrect, but give me an idea of a couple of common inefficient speakers, and a couple you think do a great job.

What is your cut-off for efficiency and impedance, more or less? What is good, and what is bad?

What a joke about not purchasing speakers with sensitivity ratings lower than 90 or lower than an 8 ohm load. In this 1 sentence, you pretty much eliminated every "best" speaker on the market. Most of these "best" speakers have sensitivity ratings in the middle to upper 80's and some go down below 4 ohms (some in the 2 ohm range). All this means, if you buy the best speaker, you also need to buy a better/best amp to drive them.

A speaker that is low efficiency (less than 88db if 8 ohms) is simply not 'the best' plain and simple. It might be very good, but not the best. Its a common misconception that when the speaker is inefficient it trades off efficiency for transparency. This idea is simply false. One of the most transparent speakers I've heard (and this is compared to Wilson, Magico and others) is 98dB (and also is flat to 20Hz), made by Classic Audio Loudspeakers. Transparency and efficiency are unrelated.

IMO/IME when the speaker gets below 89 dB you are into a situation known in the radio world as 'gold plated decibels'. You also have to pay attention to impedance; if the speaker is 89dB and 4 ohms its actual efficiency is 86dB, because 2.83 volts into 4 ohms is 2 watts, not 1. Think about it this way: in most average rooms to work with a speaker that is 89dB and 8 ohms you'll need about 250 watts to really play whatever you want without clipping the amp. But if the speaker is 95dB you'll only need 60 watts to do the same thing. Its far easier to find a good sounding 60 watt amp than it is to find one that makes 250 watts. As the power goes up, the field narrows dramatically!


Amplifiers might be able to drive 4 ohms and less, and they might be able to double power well below that, but because they can do that isn't the same as saying that amplifier is sounding its best. This is all about distortion: its distortion that causes us to hear differences between amplifiers. The brightness coloration of solid state is caused by distortion- the higher ordered harmonics, even though the THD might be only 0.01%. The ear uses the higher ordered harmonics to sense sound pressure and so is keenly sensitive to these harmonics.


Its a simple fact that all amplifiers have less distortion into higher impedance. You can see it in their specs and you can hear it as well. If you want a solid state amp that suffers from brightness to sound a bit smoother and more detailed, have it drive a higher impedance.


Not all solid state amps have brightness- this coloration occurs when the amp had insufficient feedback which is describing most of the amps built in the last 70 years. You can get away from this by having no feedback at all, or you can get around it by having really a lot. But its important to understand that you can't just go out and 'buy a better amp'; there are not that many really powerful amps that sound like music.


The other problem you deal with is of course that you get thermal compression if the speaker lacks efficiency. You can't solve this by getting a more powerful amp, it gets worse the more power you put into the speaker.

P05129 that’s what I mean- so many people try to speak with authority and absolutes but they don’t know jack other than what they know and like.

I apologize if I sound like this- I'm coming from the perspective of engineering and as an amplifier manufacturer of the last 45 years.

Agree with the requirement to try them at home first. Many showrooms have odd acoustics and it’s not always possible to properly place the speakers in that room. 

An important factor in my enjoyment of music is sound pressure level.  I’ve seen that others here tend to listen at higher SPL than I do, and I find it hard to relax at higher than medium-to-low levels.  If I’m up doing things around the house, then louder is fine, but just kicked back enjoying the music, I like the music to be an element in the room and not consume the room.

When I first got into higher-level equipment a year ago, friends and family assumed that I would be rocking the neighborhood.  I think some believe I over-spent if all I was looking for was mellow.  But I can hear everything fine without the music bellowing at me.  

Like knighttodd, I have the ML 60XT’s but paired with the Parasound A21 amp. I also have two subwoofers, but sometimes I forget to turn them on and the sound is still pleasing.  They are efficient at 94, so not hard to drive even at 4 ohm impedance.  Everyone likes something different.  

The most important factor is not the necessary well match which is needed for sure between amplifier and speakers, and everyone learns that easily, but the most important factor is the room controls OVER the speaker and the room controls designed AROUND these specific speakers...A fact which is less easily understood and learned...

Acoustic is the KEY..... Not electronic design only and mainly, even if for sure it is important....In all audio thread all is about electronic design market....BUT it is secondary to acoustic... Nothing exceed the power of acoustic to give the most rewarding experience with ANYTHING well designed with an optimal S.Q./cost ratio....

And acoustic cost TIME not necessarily money.....And remember that acoustic is NOT only passive treatment but more than that, activation of the room...

Saying anything opposite will induce complete misunderstanding in beginners and worst will ignite upgrading chase of our own tail or worst, chasing of the moon....

Underestimating acoustic is the common error in most audio threads....I already paid the price for ignoring that myself....Nobody advised me CLEARLY and LOUDLY about this fundamental task....Then i speak to beginners here....Beware...

Dont think about a 10,000 bucks dac, speakers or amplifiers to be SOLUTION... Think about the time to create acoustical settings for your system.... It will cost time not so much money....

The 2 main factor about speakers/room are ASW and LEV not bass and highs....

While I understand some of the arguments around high impedance and high efficiency speakers I also have to ask how often does this happen?  How often does a buyer mismatch his speakers and amps? 

Or is the argument if you aren't buying 16 Ohm/110 dB speakers you made a mistake?

Worst mistake for me is not to hear the speakers in your room with your gear before purchase.
I doubt impedance or sensitivity alone say a lot about the speaker sound. My worst speakers were with 8 ohm and north of 100 dB. Eversince I am around 4 ohm and below 90, increasingly satisfied with every next upgrade. And it is very true they require appropriate amplification. Every thing costs another thing. That’s life.

Forget the specs and judge each speaker on its merits. Use them only as a very broad guide to room matching and amplifier selection. Even then you sometimes get surprising outcomes that shouldn’t work well on paper.

OP:  Always run a long-term home test before buying speakers.
Give yourself plenty of time to climatise yourself to the sound.
You will have years to enjoy your choice not years to regret it.
I am sure you know this.

To all the posts about low ohms and low efficiency, your opinions are nothing but mindless prejudice.  Nothing at all wrong with 4 ohms and 86db.  As has been said, most of the greatest speakers on offer are around those figures.

My last speaker selection was narrowed down from 5 different makes, I had my own amp hooked up in their demo room and it took me 2 hours to select one, I then explained I would need to try this speaker at home, I had to buy them but on the agreement that if they wasn’t the right speaker for my room I could return for further auditioning, 
As for base and treble, my amp isa Sugden A21SE so no bias adjustment or even balance, and that’s in my opinion the way it should be.
Incidentally the speaker turned into a happy purchase and all is well.

And for all newbies out there, never buy your HiFi from a store that sells washing machines. 

I cannot speak to the science but I can share my experiences and do trust my ears

I've got a pair of Revel F36 speakers that are rated at 6 ohm they sound fantastic in a simple 2 channel configuration with no sub and many times have put them through some punishing paces, especially when testing new gear

Vocals, percussion, reed instruments and keyboards always rise to the occasion and I've had some drum licks catch me by surprise and spook me

I've got a 4 ohm pair of Tekton's on order and confident they will perform well beyond the Revel's

P05129 that’s what I mean- so many people try to speak with authority and absolutes but they don’t know jack other than what they know and like. Another common one is when you own the same component as the “know it all” and don’t like it. “Must be your cable, your room acoustics, your electricity, etc.” Okay you dim witted crab clawed keyboard jockey try to find another reason to be right about something in your windowless basement. Oh my, I need to get rid of this site so many of the good people from years ago are gone. Still many here but maybe there’s hope in the new generation.

What a joke about not purchasing speakers with sensitivity ratings lower than 90 or lower than an 8 ohm load. In this 1 sentence, you pretty much eliminated every "best" speaker on the market. Most of these "best" speakers have sensitivity ratings in the middle to upper 80's and some go down below 4 ohms (some in the 2 ohm range). All this means, if you buy the best speaker, you also need to buy a better/best amp to drive them. If you want something cheap, then it really doesn't matter much.

Good read 

https://ohmspeaker.com/news/impedance-or-how-many-ohms-do-your-speakers-have/

Speaker impedance.  
Nominal or low?  
Big difference.

The most common mistake is selected amp not capable of driving speakers to their max. Like putting the wrong engine in a car and expecting optimal performance. 

Higher impedance easier load speakers alone are no guarantee of better sound. I’ve heard supposed easy load speakers run the gamut from very good to ear bleed just like any other.

I had the exact same experience noted here.  But could not get out of my head the fantastic sound of the speakers in the show-room.  Finally, I got a cheap tube amp, and I've never worried about my system since.   (I realize this may be a case of the the tubes having LESS resolution, and the amp being less accurate.  But since what I want is music, I'm happy.  Apparently the pluses and minuses of the various parts of my system now balance out just fine, and it looks cool as hell--which is something that cannot be dismissed!)

For many years I chased resolution and got the ear drill after long term listening I’ve learned to listen to speakers for what they are and just enjoy the music. A friend in high end once told me that what I want might not exist. I was able to relate to that. I do think there is a certain mental condition that goes deeper than just hearing well associated with this pursuit. Some get flat out addicted to audio. I think the designating something as better because it's a personal preference is a path to support the  illness. That's more of a mistake than bass or treble!

to say low a lower ohm speaker that doesnot have a high sensitivity are not worth buying is  not a very sound statement 
there are many excellent Loudspeakers that are 4 ohm or lower 
this would eliminate all planer and Electrostat speakers ,as well as some of the best in the world like MBL 101s.  That is why there are many exceptions to the rule !!

The biggest mistake is buying a low impedance non efficient model that taxes an amplifier to the point that the sound suffers badly and the speakers o modern times all seem to have drive difficulty problems that you need a superamp to overcome.

Nowadays the biggest mistake is not looking at as many measurements as possible including klippel NFS so you have a good idea where your problem areas will need to be addressed. 

I have a pair of Martin Logan Motion 60 XT driven by an Parasound A21+. The ML are 4ohm. The paring makes awesome bass even at 65-75 dbl.

There are a lot of potential mistakes those new to the audio world. Yes, there is a natural propensity to mistake too much treble for detailed and therefore better. It was the first rule I learned in the late 1970’s. I certainly have heard my share of ear drills. However, If they are really good speakers the drill experience can come from the electronics driving them.

Yeah, the quest for bass can drive us to make dumb decisions on speaker size. It is guys and speakers... pretty predictable... bigger is better.
Two very common mistakes.

What do you think the biggest mistakes are when buying speakers?

Never try them before at your home (not easy but always the same mistake), i know some will demur.
Not knowing well enough your amp/amps or your spouse. 

G

Jacked up fake leading edge detail and loud continues to sell a lot of gear to the treadmill crowd.... Roger Modjeski ( RIP ) was a stickler for level matching....

No free lunch, high output at what cost ?

the laser scan of the cone compared to the input signal does not lie...

iF life were this simple the world would be ruled by OTL 30 wpc tube amps....

best to own and run planers , dynamic and horn speakers to understand what each does well, and otherwise...

Hey Ralph, I finally got the speakers. Roger has labeled them 645-8's. I put a picture of them on my system page. I have a new Cosmos coming from Sota and a Schroder CB to put on it following which it will be time to think about amplifiers:-)

@mijostyn Sound Labs, like most speakers with rear-firing information, need at least 5 feet from the wall behind them. I can't tell if that is what you have or not.