Everyone,

I’m starting this thread since its parent has grown so large that it’s becoming unwieldy, and several responses have included comments that have morphed to tangent topics.  I’m not attempting to “steal” anything so I wish to acknowledge the original thread: “Sensitivity of the new lines” posted by Russ on 3/11/2008: thanks, Russ, for your contribution.  Also, I hope this post will provide explanation for a few areas not discussed in the original.

As you review this, keep in mind that the loudness (SPL dB), power requirements of the amp (watts), sensitivity of the speaker (XX dB @ 1 watt/1meter), and the impedance of the speaker (X ohms) are all independent measures when examined separately but, once the “action” starts, all of these threads become closely interwoven.

Respondents to this forum have posed questions concerning the sensitivity of Aperion’s new line of speakers, and have wondered why this spec appears low compared to the models they’re replacing.  I’m not in a position to answer this but, I will state that for me, sensitivity (in days past referred to as efficiency) is an important consideration during my selection process.  I’m not saying it’s the most important factor (how a speaker “sounds” to me will always be the determinant) but, if undecided between two models that I consider equal in all other meaningful areas, the one with the higher sensitivity will always be my choice. 

Why?

Because lower levels of speaker sensitivity will significantly increase the power requirements for amplifiers attempting to deliver the same levels of loudness (SPL dB) when compared to models carrying a higher sensitivity rating. 

By how much power?   A bunch…and here are some reasons.

SPL, Sensitivity, and Watts 

For most of us, an increase in SPL of around 3 dB is noticeable.  I’ve also read that some golden-earned audiophiles can distinguish changes of 1-2 dB (I’m not one of them).  Whatever your perception, a 3 dB increase in SPL for a given speaker requires a doubling of power delivered by the amplifier.  At low-to-moderate volumes (SPL) this isn’t likely to be a problem since most AVRs can comfortably handle this demand.  However, start turning the volume UP, and/or play something with some really dynamic swings in levels, and things can change in a hurry.   

Here’s a baseline example for one speaker with a rated sensitivity of 83 dB (Model 83) when compared to another with a rated sensitivity of 92 dB (Model 92), and assuming both are measured at 1 watt/1 meter (the standard reference point for sensitivity published by reputable mfgs).  The speaker’s impedance at this point is not a consideration (but might be later).

SPL       Model 83    Model 92

(dB)          (watts)         (watts)  

 83                 1                <1

 86                 2                <1

 89                 4                <1

 92                 8                  1

 95                16                 2

 98                32                 4

101               64                 8

104              128               16

107              256               32

110              512               64

112             1024             128

115             2048             256

Depending on a multitude of factors (how loudly you listen to your stuff, the size and volume of your listening environment, where you position your speakers, their proximity to reinforcing boundaries, the room’s furnishings, the room’s finish, and probably more.), momentary SPLs of > 112 dB may not be uncommon during musical “peaks” or, more especially, when experiencing movie “effects”  And while both characterizations might be very short-term in duration, the power demands are real and immediate.  It’s obvious from this example that low levels of speaker sensitivity require substantial amounts of amplifier power.  And here’s another consideration (as if we needed more) that will increase power requirements for a given level of SPL: you’re probably listening more than one meter (~ 3 feet) from your speakers.  All of these variables affect SPLs, and each of them can do so in a negative manner. 

Regardless: for two speakers with an initial difference of 9 dB in baseline sensitivity (representing 8 watts max), once we start rockin’ (or thumpin’, or whatever), we’re now looking at 2,048 watts vs. 256 watts for speakers attempting to deliver identical levels of 115 dB SPL.  Reality: less sensitivity = more watts.

Go price an amp of 1,000+ watts to one of 250+ watts and compare.  Fact: more watts = more $. 

This is one of the few examples I’ve ever found in which less means more ;-)

As info: 2,048 watts (more than two kilowatts, and within spittin’ distance of three horsepower) represents an eight-fold increase in power when compared to 256 watts.  If you need this amount of power, I suggest you have a dedicated 120 VAC outlet with a 20 amp circuit breaker for your amp alone.

Impedance

SPLs of this magnitude (and wattage) will also challenge the most robust designs of amplifiers, and as you approach these levels of SPL your AVR’s power supply will need to begin delivering some serious current (amperage).  And here’s where the speaker’s nominal impedance (measured in ohms) becomes important: since the transformer’s secondary voltage is fixed at a predetermined maximum level, speakers having a rated impedance of < 8 ohms are going to place more demands on the power supply since the ultimate power delivered is determined by the transformer’s ability to supply amperage (this is Ohm’s Law operating in one of its basic forms).  Reality: low impedance = more current.

For two transformers having identical primary and secondary voltage, and differing only in their power rating (VA, or kVA, or Watts, determined by current output), the higher powered unit will have more of everything: heat, size, weight, windings of wire both primary and secondary, and larger gauge of wire.  Compare costs.  Fact: more current = more $.

If the AVR you’re considering (or already own) has a provision for setting the speakers’ impedance (via a switch, OSD menu selection, or some other means), there’s a reason for this: it’s probably current-limited and you’ll be engaging some form of protection to keep your AVR from harming itself (and your speakers) during exuberant use.  If your AVR doesn’t have this provision, or some other warning specifically mentioning loads < 8 ohms, I wouldn’t be that concerned (meaning the mfg has probably furnished a power supply capable of handling any load between 4 and 8 ohms). 

How does any of this matter?

If you have a large room with high/vaulted ceilings, heavily furnished (carpet, drapes, overstuffed furniture), need/want high levels of SPL, and are running full-range speakers having low impedance and low sensitivity (all of this describing a worst-case scenario), then be prepared to continue the more reality with even more $$, because everything mentioned applies in spades to your application.

If you’re budget-limited, be aware.  If you’re not, or don’t mind building your system over time…then proceed with enjoyment.

Whatever your situation, my best advice is to find a high quality sub with built-in amplification: even a few hundred watts dedicated to a narrow band of response (< 100 Hz) will substantially reduce the power requirements of your AVR for the remainder of the spectrum (out to 20 kHz)…especially at elevated levels of SPL.

my experience

Excluding the sub, the foregoing accurately described my situation for ~ 15 years.  During this period my system evolved from a basic receiver/2-speaker stereo (carryovers from the military, then college) to an elaborate system of separates employing multiple power amps and speakers.  If I still had the space for all of this, I might not be visiting this forum…but I’d still be interested in a good, small sub (new Bravus line looks ideal for me…..right-on, Caleb!).

The two most eye-opening (ear-splitting?) exposures for me were EQ (won’t be discussed here) and efficient speakers.  Beginning with 2 speakers having a sensitivity of ~ 88 dB (AR), and then adding another pair (Advent), it took me a few years to eventually wind up with a configuration having sensitivities of 92 dB, 94 dB, and 104 dB (Klipsch).  During this evolution I lost many tweeters (six or seven replacements), all during my quest for SPL.  Since I’ve discovered efficiency, in the past 20 years I’ve had to replace nothing.  And trust me…I could entertain the neighborhood with this setup.  And the EQ assisted greatly in making everything sound balanced and clean (and having nearly 800 watts RMS probably made some contribution to this as well).  I spent a lot of money (according to my wife…and, yeah, I guess I did) during this period. 

If I had it to do over, would I change anything?  Yes…I’d grab efficient speakers from the get-go, and save some $$ on amplification. 

Do I have any regrets?  Absolutely not...this became my hobby and passion (one of them, at least), and I learned a lot during this journey.  Plus…I’ve had a helluva’ lot of fun!

Stated differently…as Kris Kristofferson once observed: “the goin’ up was worth the comin’ down”.  Amen, brother!

I hope this helps someone make a more informed decision.

Fred

Fred,

Interesting and very informative post.  I'm new to this area so please forgive me if I ask some 'newbie' questions.  Here they are:

1.  What is the basis for a lower sensitivity:  eg, the new line of speakers just introduced, for the most part, have a lower sensitivity.  Seems speaker for speaker, sensitivity of the new line has dropped between 2 and 3 dbs.  In some cases, the impedance has dropped as well.

2.  What is the advantage to the manufacturer to producing speakers with a lower sensitivity.  Do they cost less to design and manufacture?

3.   The analogy that the new speakers are like sports cars has been used in the past:  not so good on gas but their performance is superb.  Given what you just wrote, I don't know how that can be true.

 4.  What happens to the sound during instances that require 1250 watts but the receiver is only rated for, say 110?

The new 6b has a sensitivity of 83db.  Probably the lowest sensitivity I've seen in my short time researching speakers.  I've preordered a pair but now I'm having second thoughts.

 
Thanks for you guidance.

Bill 

Hi, Bill

1.      As mentioned early in my post, I’m in no position to answer this (Aperion can).  It’s entirely likely that the lower sensitivity and impedance were the results of design changes that allowed Aperion to improve some other parameter that they found desirable: the flatness of the frequency response, lower extension at its bottom end, presentation of soundstage, etc., as opposed to a conscious decision to intentionally lower both of these parameters.  As to what this might be, I can’t answer.

2.      There’s no real advantage that I’m aware of unless there was something mentioned in #1.  I also don’t believe there’s any type of cost savings for any mfg simply because they have an offering with lower sensitivity or impedance.  In fact, it’s entirely possible that their costs could have increased because of these changes, and may explain the price increase associated with the new line (as well as inflation).

3.      That analogy may be pretty accurate.  I’ve heard some very expensive speakers (European) that sounded great and were also pretty power hungry.  Same thinking applies to my ownership of AR and Advent...I loved their sound but they had an appetite for huge amounts of power.  From my desire for SPL, they simply couldn’t give me what I wanted (even with two power amps totaling 800 watts RMS).  I hope I didn’t write anything in my post that implied lower sensitivity (or impedance) means lower quality, so let me state now that…it doesn’t!

4.      If you’re really pushing your system hard (high SPL) and your amp can’t keep up, it’s going to overextend the ability of the amp’s power supply.  When this happens, you’ll either hear the amp starting to distort badly (at these levels it should be very noticeable), some form of protection will activate to reduce levels (if your amp has this feature, and this should also be noticeable), you’ll blow the amp’s fuse or, worse yet, the amp will “clip” (technical jargon associated with over-driving) and probably damage your speakers (tweeter probably the first to let go).  There may be other things that happen…and all of them will be BAD.  In any event, low sensitivity and low impedance will place more demands on the amp than the opposites.  This is also the main reason I suggested getting a sub…a sub can aid significantly in reducing the power demands placed on the amp.

At this point in the game I wouldn’t be having second thoughts.  Get them home, hook them up, and give them a listen for a few weeks (I’m also a believer in “break-in”).  It’s likely you’re going to love your selection. 

The main point of my post was that efficiency/sensitivity proved to be an important factor for me…it may or may not be important for you.  My listening environment was pretty large and I felt I needed everything as described.  My system also evolved and it took me years to reach the point where I was satisfied.  Once I got there, I was in heaven!  I will also add that the WAF (in my case) established permanent residence in the negative range (typical comments were…”abnormal”, “who needs this?”, “insane” – you get the idea).  When I was “in the mood”, she left the room.  However, had I initially purchased speakers with high sensitivity, I could have gotten by with far lesser amounts of amplifier power.  Having said this, 83 dB is one of the lower sensitivities that I’ve seen.

The purpose of this forum is to ask questions, share information and experience and, hopefully, all of us will benefit and make selections that better fit our needs.  And “newbie” questions are a vital part of the educating process (for all of us) so, thanks for your interest.

Hope this helps.

Fred

Fred and Bill,

Fred thanks for the post.  Very informative.  Just a couple of points to bring up.  I dabled in speaker build many years ago and learned just enough to be dangerous.  One way to that sensitivity is effected is in matching the up the drivers.  For instance the 6T and 6B use the same drivers but configured quite differently.  Also there is a possiblilty from a cost effeciency point of view as well as a consitant family sound point of view the crossovers are very similar across the whole line of speakers.  This would be a very unserstandable reason for the sensitivities to be all over the map, which they are.  Only speculation of course.

My current speaker system (2.0) was built by me from a kit about 16 years ago.  It is a very intresting little speaker.  It uses dynaudio drivers (they use to sell raw drives) a legendary tweeter that I have seen used on ebay for $100 and a nice little 6.5 woofer.  It used high quality parts in the crossover and the company has the crossover designed by some legendary audio guy.  It has a sloped face to better time align the drivers and is not ported or sealed.  They called it simulated infinite baffle system.  It has 2 1/2 in. holes inthe back covered with acoustic form the inside.  These things are sweat but a couple of years ago one of the woofers broke.  I found this company called Madisound who does repairs and can even re-surrond dyaudio woofers.  It sent it to them and they found the wire to the voice coil broke.  The resoldered and sent it back to me no charge.  Good company.  I have had to do the same to again and I don't think it can be done again.  This woofer is no longer made.  I have never been able to find used ones anywhere.

Sorry to wander so much.  My current speker are 6 ohms and 86 db sensitivity.  My lowly Onkyo 503 with 75 per drives them fine.  The 5Bs are since Thursday or Friday are listed as 86 db so I think I am going to be fine.  I plan to get a sub that as you pointed out that will help even more. 

I was spoiled on the sound of that dyne audio tweeter and the musicality of the mid and firm bass of the little dynaudio woofer, I sure hope Aperion is as good as so many people think they are.  15 years ago I paid a little more for the kit, that I had to assemble, than for a pair of 5Bs with stands.

Heya Fred,

Great, technically enthusiastic post.

So... if a speaker produces 83db SPL with one watt, then would two speakers with the same rating produce 166db when working together? If there were 5 speakers, each fed with a watt of power, aimed at the same microphone from 1 meter away, would the result be an SPL of 415db?

P.S. Of course, I know the answer, but figured I would stoke the fire on behalf of those who don't.

Hi Caleb,

Sorry for the interception, but there were no receivers where you threw the ball.

How many 83db rated speakers would it take to equal one 89db rated speaker measured in SPL @ 1 watt/meter on axis and these speakers are all Aperion?

I bet that Fred does get this right although I may have given something away and if he does not, we will meet on Caleb Street at High Noon.

Just keeping the fire burning.

Jack Gates:

Hi Caleb,

 

Sorry for the interception, but there were no receivers where you threw the ball.

 

How many 83db rated speakers would it take to equal one 89db rated speaker measured in SPL @ 1 watt/meter on axis and these speakers are all Aperion?

 

I bet that Fred does get this right although I may have given something away and if he does not, we will meet on Caleb Street at High Noon.

 

Just keeping the fire burning.

 

Jack

Bit of a loaded question there Mr. Gates, but the theoretical answer would be two 83db rated Aperions would equal an 89db speaker. This would be assuming that the speakers were placed properly, you were getting no reading in the SPL of room variances from the speakers (I suppose outdoors would be best), you had no phase issues from the 2 speakers, and that you had a pretty kick butt SPL meter to accurately measure this.

It's officially 12:19 PST...not quite high noon, but close!

Hi David,

I appreciate your response, but I believe you would need (4) 83db rated speakers to equal 1 89db rated speaker since doubling the number of speakers increases SPL by 3db. Two should yield 86db and Four should then yield about 89db.

I actually conducted this test myself using Bose cubes in my office. The SPL on axis  using the Aperion SPL meter was 3db higher when both L and R were active as opposed to either L or R alone.

So, if doubling the number of speakers yields a 3db in SPL then quad speakers of the same design should yield a 6db increase in SPL, right? I found a 3db increase in SPL from 1 to 2 identical speakers not 6db.

Reference the links below.

http://www.baudline.com/erik/ht/dB_laws_etc.html

http://www.musiccenters.com/vol.html

Caleb, Jack, David

So many questions…what is this – a gang bang?  But I’ll say up front…something looks fishy (or Caleb never would have asked the question).

My post, I’ll do the math.

Correct that…can’t find my calculator, but since I did find my glasses I’ll do a little arithmetic.

Let’s see:

            1 Aperion        83 dB          1 watt                             

            1 Aperion        83 dB          1 watt

            2 Aperion       166 dB         2 watt

Wait just a minute while I compare to what I had…

            6 Klipsch         117 dB      750 watts

Hold on here…I told you something looked fishy.  Back in a second after I check my manuals and cut sheets.

Oh, my God…

my wife was right…

I was “insane”.

Feelin’ a little woozy right now lickin’ the barrel of my Colt Diamondback (must be the oil).

Forget High Noon, Jack.  Can I borrow some Full Metal Jacket?

If I don’t sign on later, well……

Fred

PS - Before I go, I would have agreed with Jack.

Jack Gates:

Hi David,

 

I appreciate your response, but I believe you would need (4) 83db rated speakers to equal 1 89db rated speaker since doubling the number of speakers increases SPL by 3db. Two should yield 86db and Four should then yield about 89db.

 

I actually conducted this test myself using Bose cubes in my office. The SPL on axis  using the Aperion SPL meter was 3db higher when both L and R were active as opposed to either L or R alone.

 

So, if doubling the number of speakers yields a 3db in SPL then quad speakers of the same design should yield a 6db increase in SPL, right? I found a 3db increase in SPL from 1 to 2 identical speakers not 6db.

 

Reference the links below.

 

http://www.baudline.com/erik/ht/dB_laws_etc.html

 

http://www.musiccenters.com/vol.html

 

Jack

Mr. Gates,

I referenced this book to answer your question:

Anyone who wants to dig a bit deeper into good ol audiophile land should give it a read. It's got tons of great information on anything and everything regarding speakers and components. Anyways, Robert Harley uses a reference to buzzing flys in an analogy on referencing this subject. He states in that under the conditions I stated (in reference to positioning, phase, etc) you would have a 6db increase in SPL. This would mean that each speaker/fly were producing the EXACT same SPL, as well as were also PERFECTLY in phase. This is why I phrased it as such. In a real life situation, the phase relationship between the 2 sounds would be more random, which would only produce an increase in 3db such as you stated.

It would seem we were both correct in our own respects...This is why I made sure to state these conditions before answering said question. 

David (and Caleb and Jack),

I was so busy trying to be a funny Smart Asp (where have I heard that before?) that I posted before finishi