Room effeciency or Enclosure designs?

[thecoolguy11]

Option 1
---------
Energy Act 6
Room Effeciency: 87 db
System type: "Acoustic suspension"

Option 2
----------
Athena Micra 6
Room Effeciency 89 db
System type: 2 way bass reflex

From whatever I have read till now, Acoustic suspension designs yield cleaner more precise sound with a cleaner bass while they compromise on effeciency.
With this in mind, what is the bigger factor when considering speakers, Room effeciency or enclosure type? All other factors equal, what should one compromise on; effeciency or system type.
I intend to use the package for both music and movies.
I am currently running Athena Micra 6 on the Yamaha HTR5760.

 

[Pat D]

Option 1
---------
Energy Act 6
Room Effeciency: 87 db
System type: "Acoustic suspension"

Option 2
----------
Athena Micra 6
Room Effeciency 89 db
System type: 2 way bass reflex

From whatever I have read till now, Acoustic suspension designs yield cleaner more precise sound with a cleaner bass while they compromise on effeciency.
With this in mind, what is the bigger factor when considering speakers, Room effeciency or enclosure type? All other factors equal, what should one compromise on; effeciency or system type.
I intend to use the package for both music and movies.
I am currently running Athena Micra 6 on the Yamaha HTR5760.

It's a question how accurate sensitivity specs are for speakers. I suspect they're reasonably close here. Anyway, the anechoic results are probably about 3 dB less so neither one is notably sensitive. I say sensitivity because it is voltage sensitivity, how much output at 1 meter away the speaker will produce with a 2.83 volt input, which is equivalent to 1 watt into 8 ohms. But few speakers have a flat impedance vs. frequency curve, so we don't actually know the watts used. Sensitivity should be measured with broadband noise covering at least the midrange, not just at a single frequency.

I don't think the difference in sensitivity is enough to worry about, assuming your amp can drive both of them. However, in general, sensitivity is more of an issue than enclosure type but 2 dB is not a big difference.

Anyway, don't worry about enclosure types. Those who generalize concerning them don't know what they are talking about. It's a design choice. It's the results that count. Good speakers can be and are made either way. Which speakers do you like best? That's the question.

Do you like the Energy speakers better than your Athena speakers?

 

[Rip Van Woofer]

Anyway, don't worry about enclosure types. Those who generalize concerning them don't know what they are talking about. It's a design choice. It's the results that count. Good speakers can be and are made either way. Which speakers do you like best? That's the question.

Yep! Every theoretical model of speaker design involves tradeoffs. No existing speaker is a perfect implementation of its underlying design principles. It's all in how well the designers implement the model and handle the inevitable tradeoffs. And how well the final result meshes with your idea of good sound. Even a hardcore objectivist measurment freak like me agrees with that!

Right now, FWIW, I'm a "point-source-with-wide-dispersion, open-baffle dipole" guy. Emphasis on the FWIW!

 

[WmAx]

As the other respondents have made clear; enclosure alignment is not so important as long as it was implemented in a manner to optimize the engineering objectives. Of course, their are many variables -- none of which have a place in this generalized summary. Besides, the most distinct thing that one can 'generalize' with concerning alignments is the 'general' effective high pass filter order of the respective alignemnt. But the slope rate is no where near as important as the cutoff point; slope rate, comparatively, has little[1] effect.

-Chris

Footnotes

[1] Quantification of Subwoofer Requirements, Part II: The Influence of Lower System Cut-Off Frequency and Slope and Pass-Band Amplitude and Group Delay Ripple
AES Preprint: 5199
Bech, Søren

Option 1
---------
Energy Act 6
Room Effeciency: 87 db
System type: "Acoustic suspension"

Option 2
----------
Athena Micra 6
Room Effeciency 89 db
System type: 2 way bass reflex

From whatever I have read till now, Acoustic suspension designs yield cleaner more precise sound with a cleaner bass while they compromise on effeciency.
With this in mind, what is the bigger factor when considering speakers, Room effeciency or enclosure type? All other factors equal, what should one compromise on; effeciency or system type.
I intend to use the package for both music and movies.
I am currently running Athena Micra 6 on the Yamaha HTR5760.

e o

 

[av_phile]

Option 1
---------
Energy Act 6
Room Effeciency: 87 db
System type: "Acoustic suspension"

Option 2
----------
Athena Micra 6
Room Effeciency 89 db
System type: 2 way bass reflex

From whatever I have read till now, Acoustic suspension designs yield cleaner more precise sound with a cleaner bass while they compromise on effeciency.
With this in mind, what is the bigger factor when considering speakers, Room effeciency or enclosure type? All other factors equal, what should one compromise on; effeciency or system type.
I intend to use the package for both music and movies.
I am currently running Athena Micra 6 on the Yamaha HTR5760.

By design, bass reflex speakers are meant to impart a higher efficiency compared with accoustic suspension speakers. The latter, however, is preferred by many audiophiles precisely for the reasons you indicated. Those reasons are sufficient to put the issue of efficiency in the back seat. For as long as you have enough power to drive those speakers to the levels you want at your listening position, cleanly and accurately, I don't see a problem. Efficient speakers are often preffered when using low power amplifiers like SETs. Efficient speakers are preferred if all you want is to extract the most power out of your amplifers in a large room. Otherwise, efficiency is often the least consideration when looking for clean articulate and accurate sound from speakers. Some excellent sounding speakers I've heard have very low sensitivity figures below 85db. And many lousy speakers I've heard have very high sensitivity figures in the 92db+ range.

 

[Rob Babcock]

The cabinet alignment may be of importance to the designer, but it needn't be of much concern to the end user. If the speakers must sit very close to the wall, you may want to avoid rear ported models, but otherwise don't worry about it.

In the past there was more difference between sealed & ported speakers, but better drivers and more sophisticated computer modelling has largely relegated that old cliche to the audiophool bonepile.

Small speakers will be less sensitive than larger ones, all else being equal, no matter what the cabinet alignment. 87 dB/W/meter is a tad on the low side of average, but 89 isn't a huge difference. If you don't plan to crank them up too loudly, and the sub is decent, either should suffice.

Go with whichever one you think sounds better. And if WAF is an issue, by all means consider which is better looking. Lastly, look at the warrenty offered by each. Both have good reputations, so just go with the one you like best.

 

[WmAx]

By design, bass reflex speakers are meant to impart a higher efficiency compared with accoustic suspension speakers. The latter, however, is preferred by many audiophiles precisely for the reasons you indicated.

At least you are consistant in ignoring the bulk of valuable posts in every thread, regardless of subject.

-Chris

 

[annunaki]

Chris, it should read "bass reflex enclosures are meant to impart higher efficency....."

That still does not mean that a bass reflex enclosure (ported/vented) cannot outperform an acoustic suspension (sealed) enclosure in terms of sound quality or output. Or vice versa. It depends on the overall engineering design goals.

 

[WmAx]

Chris, it should read "bass reflex enclosures are meant to impart higher efficency....."

That still does not mean that a bass reflex enclosure (ported/vented) cannot outperform an acoustic suspension (sealed) enclosure in terms of sound quality or output. Or vice versa. It depends on the overall engineering design goals.

Actually, the first part of that quoted statement was left to keep the last part in context. My reply was meant to apply to the last part: "The latter, however, is preferred by many audiophiles precisely for the reasons you indicated."

Sorry, but I don't have reason to believe that a general audiophile(or even most hobbyist loudspeaker designers) has a clue what the actual variables are and degree of effect they have on pereception or why. Slope rate in itself has little effect compared to general frequency range coverage, as is concluded by perceptual research and by my own controlled tests into the matter. Just another thing blown way out of proportion by ignoring the many variables and instead speculating. My issue was that av_phile made the quoted statement, seemingly as if he ignored the informaiton up to this point that pointed out that overall engineering objectives were far more important then just the matter of whether or not the bass alignment was sealed or ported.

-Chris

 

[plhart]

When referring to speakers the terms efficiency and sensitivity are often (and erroneously) used interchangebly. Efficiency is given in % and sensitivity is given in dB. An 89dB sensitivity speaker system will usually have an efficiency, which is tied to the woofer's efficiency, of ~0.6%. That right. That is how inefficient speaker systems generally are.

The question of a ported vs. acoustic suspension system is tied into many factors but the bottom line is that a ported system will roll off at the low end at approximately 24dB/octave and an acoustic suspension design will roll off at approximately 12dB/octave. The work for the lowest range of a ported system is handled by the port while in an acoustic suspension design the woofer does all the work.

A woofer in an acoustic suspension cabinet is usually a bit more expensively built because the speaker, which has to do all the work, needs to have a much longer, linear throw or Xmax to have the same measured distortion (this is a generalization) as a ported design woofer. This means a longer and more expensive wind-length of copper on the voice coil former and a bigger magnet (or motor structure) to control it.

In the real world of truly decent (not bottom of the bucket cheapie) designs many low frequency transducers fall into a category wherein they can be used for either type of enclosure. The limiting factor then becomes the sensitivity of the overall system with the acoustic suspention design usually having the lower sensitivity. Think of it like this>

The amount of "work" a woofer can do is already represented by the weight of the moving mass (cone, voice coil etc) and the magnet (or motor) driving it. (This is assuming no restriction from the surround and spider). That "work" is very analogous to the area under the frequency response curve (but remember, we're in the logarithmic scale). So the acoustic suspention design which has the woofer doing all the work is pushing that woofer much further up and down in the gap to get that gentler roll-off slope while the ported woofer can do more "work" more efficiently, up further in the frequency range, and then hand the lowest frequencies off to the port (which in fact cannot be as efficient as a driven piston (the acoustic suspension design) in reproducing the lowest frequencies.

 

[WmAx]

Think of it like this>

The amount of "work" a woofer can do is already represented by the weight of the moving mass (cone, voice coil etc) and the magnet (or motor) driving it. (This is assuming no restriction from the surround and spider). That "work" is very analogous to the area under the frequency response curve (but remember, we're in the logarithmic scale). So the acoustic suspention design which has the woofer doing all the work is pushing that woofer much further up and down in the gap to get that gentler roll-off slope while the ported woofer can do more "work" more efficiently, up further in the frequency range, and then hand the lowest frequencies off to the port (which in fact cannot be as efficient as a driven piston (the acoustic suspension design) in reproducing the lowest frequencies.

ONe would ask about the 'lowest' frequencies to which you refer. Absolute or practical(useful)? Take a single example of a speaker that is suited to both enclosure types(EBP around 50-60), and compare the relative efficiency and frequency response. The 4th order system will have signficant lower practical extension, higher SPL capability and considerably higher sensitivity for a given power input throughout part of the bandwidth.

Here is a simulaiton of a speaker(1 watt power input across the graphed bandwidth) that is suited for either enclosure type, modeled in both(sealed alignment is qtc 0.7 in this example) While further variations are possible upon this example, I chose parameters that provided for the best compromise in frequency response/efficiency for both. For example, I could have used a lower QTC for the 2nd order alilgnment, but this would have provided higher output at the very lowest frequencies(f15-f20 starting point), it would have lowered efficiency of the useful ranges above these. Somewhat similar compromises can be made with the ported system:

I did not provide for more then 14db of resolution in the plots, but past approx. -20dB under reference, the sealed does begin to surpass the output of the ported enclosure. THis is not practical/useful extension. But technically it is possible of 'deeper' response. But useful deeper response? The 4th order system is capable of significantly higher SPL throughout the majority of the low frequency extension as compared to a 2nd order system. Certainly sealed systems have their applications. So do 4th order systems. As a rule, a ported system will be more efficient and allow for greater maximum SPL with the same transducer. If the objective does not require the efficiency gains(for whatever reasons) and the frequency response is adequate for the application, then of course their is no benefit or reason to use a 4th order alignment.

-Chris

 

[plhart]

Your point is well taken Chris if one applies a "classic textbook" comparison set of curves with the acoustic suspension design having a critically damped Q =0.7 as you have illustrated. I know of no commercially produced "full-range" acoustic suspension speaker today which is produced with such a low Q. (However, I can certainly be wrong on that account.)

The scenario to which I was alluding while trying to keep it less technical for the majority of our readers was one in which the driver Qtc was closer to the "ideal" of 0.4 and the Efficiency Bandwidth Product (EBP) is between 75 and 90. I was holding both ported and sealed box Qts =~1.2 in my example to use a figure closer to what is commercially available today.

Note in most of my responses or explanations to our Audioholics readership I is my intention to impart useful information in the most easily understandable way.

 

[annunaki]

Actually, the first part of that quoted statement was left to keep the last part in context. My reply was meant to apply to the last part: "The latter, however, is preferred by many audiophiles precisely for the reasons you indicated."

Sorry, but I don't have reason to believe that a general audiophile(or even most hobbyist loudspeaker designers) has a clue what the actual variables are and degree of effect they have on pereception or why. Slope rate in itself has little effect compared to general frequency range coverage, as is concluded by perceptual research and by my own controlled tests into the matter. Just another thing blown way out of proportion by ignoring the many variables and instead speculating. My issue was that av_phile made the quoted statement, seemingly as if he ignored the informaiton up to this point that pointed out that overall engineering objectives were far more important then just the matter of whether or not the bass alignment was sealed or ported.

-Chris

I got ya.