Genelec 8331A Powered SAM Studio Monitor Review (by Erin)

[Sancus]

I'm not disagreeing, but are you aware of evidence that clearly shows these effects?
I see people routinely play the Doppler/IMD-card with little to nothing for evidence.

As I'm sure you're aware, Doppler & IMD are two different things(but often just called IMD) -- every comparably sized 2-way speaker has higher IMD than a 3-way and that's pretty well known and has been studied by eg Neumann(pg16).

The only attempts I've seen to measure the Doppler effect are from Erin. He measured a Kef Q100 driver back in 2013, and that actually did show significant and certainly potentially audible effects.

Kef Q100 Doppler Distortion

Spoiler

He duplicated this test in the IN-5 review and that showed much, much less, although still some effect. That's not surprising because it's a 3-way design and so the midrange needs far less excursion.

Kali IN-5 Doppler Distortion

Spoiler

Doppler distortion is also cited as one of the reasons that Genelec chose to make the Ones 3-way in their white paper on the design.

However, current coaxial transducers suffer from problems such as sound-colouring diffraction due to discontinuities between the coaxially located drivers. Particularly two-way coaxial designs can have problems with Doppler distortion, having to operate each transducer over a wide frequency band. Although a two-way active loudspeaker is the ubiquitous reliable work horse of the industry, a three-way design offers the potential for improving performance in several ways including extended frequency range, better control of directivity, higher output capacity and lower distortion. Particularly for coaxial designs, a three-way construction can also significantly reduce the issue of Doppler distortion in the coaxial transducers.

Now, how audible is any of this? It's an open question short of blind testing. But we *do* have at least one report from Harman blind testing that indicated this type of distortion in Kef 2-ways had a significant impact on preference ratings.

The statistical listening test results rated the speaker lower than the Spinorama measurements would have rated it. Since the Spinorama statistically correlates highly (0.86) to listener preference we felt the need to investigate. Our intention was not to bash the KEF, but to discover which measurement might explain the discrepancy. To be completely correct, we have not studied the issue sufficiently to say with absolute certainty that IMD (Intermodulation Distortion) due to the coaxial alignment is the definitive cause. However, the evidence, meager though it may be, does support this...

However, it is not our intention to abuse the DUTs. We only ran the IMD test up to 8V (~99dB), not 22V, so well within the operational range. Instead of picking the worst case bass frequency for each speaker, we specifically set the bass tone to 90Hz. This was well within the rated operational parameters of all the speaker models; and 90Hz is above the standard (80Hz) electronic crossover to a subwoofer (i.e.: this will happen even if the customer uses a subwoofer!). Incidentally 90Hz was the worst case bass frequency for the Revel, but not the KEF. So, I feel what we did was more than a fair replication of real-world conditions. At 5.67V (4W ~93dB nominal) the KEF has 16% IMD in the voice sweep, 23% at 8V. When listening to this test, the IMD is clearly audible, even 5%. Hence we use it as a demo. Not to bash, but to educate. When the IMD is heard in this way, it is very compelling to accept that this could cause reduced preference by listeners. Listening corroborates the IMD test data.

They conclude:

...this effect will probably be mitigated in a 3-way system. The higher the crossover frequency and more limited the frequency range, the less cone movement and the less IMD. There are other mitigation techniques. But that is what they are. IMD is inherent to all drivers and, while it may be caused by many factors, most are a function of excursion.

Between the measurements, and the conclusions from multiple manufacturers who follow the science that a 3-way is the "gold standard" for coaxials, I think the evidence is clear that 2-way coaxials are indeed inherently flawed. This flaw may not be audibly significant at close distances or low levels, but that is pretty much impossible to determine without very carefully designed blind testing of specific models.

That doesn't mean nobody should buy an LS50 Meta, or that it sounds worse than an 8331A. But if you want the best performing coaxial, and especially if it's important that it sound good while playing loudly, then you want a 3-way.

Size will affect SPL, sure.
Coaxial-ness, though? What's the connection?

Combining the tweeter and the midrange (and/or) woofer can limit the size of the magnet, reduce the driver area, and limit the maximum excursion more than a non-coaxial design. These are just general design challenges though and f ex Genelec has obviously overcome them with the design of the 8361A.

 

[dc655321]

As I'm sure you're aware, Doppler & IMD are two different things(but often just called IMD)

Yep. I meant to imply that those two items seem to be the coaxial-beating-sticks of choice.
Though, I suppose Doppler could be considered a form of IMD? If you squint? Maybe?

The only attempts I've seen to measure the Doppler effect are from Erin. He measured a Kef Q100 driver back in 2013, and that actually did show significant and certainly potentially audible effects.

I knew of those measurements, but I had a spectral (range) measurement in mind and disregarded it.

Now, how audible is any of this? It's an open question short of blind testing. But we *do* have at least one report from Harman blind testing that indicated this type of distortion in Kef 2-ways had a significant impact on preference ratings.

Ah! I was not aware of that story. Thx!

Combining the tweeter and the midrange (and/or) woofer can limit the size of the magnet, reduce the driver area, and limit the maximum excursion more than a non-coaxial design. These are just general design challenges though and f ex Genelec has obviously overcome them with the design of the 8361A.

"General design" issues indeed!
aka "operate components within their comfort zone"

Thanks for the thoughtful post.

 

[TurtlePaul]

2-way coaxials can be SPL limited because you are punching a 2” hole in your woofer and the woofer can’t be much bigger than 5-6” or you start to face beaming.

 

[Tangband]

Nice review by Erin.

Everything is relative. This 8331 is a better sounding loudspeaker than 8030c or 8330 , and goes deeper in the bass .

The price is very high, but one must compare with other loudspeakers to calculate if its worth the money.
This monitor is made for very small spaces or to be used on a desktop . In that context , It might be one of the worlds best loudspeaker and the 4500 dollar price maybe dont seem to high then…

Another thing - This 8xxx monitors have a loudspeaker cabinet made of metal, much stiffer than mdf . This alone also makes a point in sound quality. As a former DIY:er , making thousands of measurements on my own constructions and on the 8330 and my 8340 , the sound seem somewhat clearer than all other loudspeakers . Comparing the 8340 with a Kef R5 , there is clearly a difference where the Kef loudspeaker muddles the sound because of the mdf material releasing delayed energy. This is not something Amirms measurements shows, but you can hear it.

Im sure Genelec could produce a 8331 loudspeaker made of mdf that would cost 1000 dollars less, but the sound would also be worse.

The loudspeaker manufacturer Magico says :

http://www.bm.rs/Magico%20Alon%20Wolf%20Interview.pdf

 

[tifune]

. This is not something Amirms measurements shows, but you can hear it.

Do you know, is there anyone taking such measurements? Not sure what I would be looking for if it's not included w/ Amir or Erin's reports

 

[Marc v E]

As I'm sure you're aware, Doppler & IMD are two different things(but often just called IMD) -- every comparably sized 2-way speaker has higher IMD than a 3-way and that's pretty well known and has been studied by eg Neumann(pg16).

The only attempts I've seen to measure the Doppler effect are from Erin. He measured a Kef Q100 driver back in 2013, and that actually did show significant and certainly potentially audible effects.

Kef Q100 Doppler Distortion

Spoiler

He duplicated this test in the IN-5 review and that showed much, much less, although still some effect. That's not surprising because it's a 3-way design and so the midrange needs far less excursion.

Kali IN-5 Doppler Distortion

Spoiler

Doppler distortion is also cited as one of the reasons that Genelec chose to make the Ones 3-way in their white paper on the design.



Now, how audible is any of this? It's an open question short of blind testing. But we *do* have at least one report from Harman blind testing that indicated this type of distortion in Kef 2-ways had a significant impact on preference ratings.



They conclude:


Between the measurements, and the conclusions from multiple manufacturers who follow the science that a 3-way is the "gold standard" for coaxials, I think the evidence is clear that 2-way coaxials are indeed inherently flawed. This flaw may not be audibly significant at close distances or low levels, but that is pretty much impossible to determine without very carefully designed blind testing of specific models.

That doesn't mean nobody should buy an LS50 Meta, or that it sounds worse than an 8331A. But if you want the best performing coaxial, and especially if it's important that it sound good while playing loudly, then you want a 3-way.


Combining the tweeter and the midrange (and/or) woofer can limit the size of the magnet, reduce the driver area, and limit the maximum excursion more than a non-coaxial design. These are just general design challenges though and f ex Genelec has obviously overcome them with the design of the 8361A.

Thanks! I always thought the midrange driver in the 8361 seemed rather small, but now it totally makes sense.

 

[Tangband]

Do you know, is there anyone taking such measurements? Not sure what I would be looking for if it's not included w/ Amir or Erin's reports

John Atkinsson at stereophile measures the resonances in the loudspeakercabinets .
The time smearing with mdf is very easy to hear, especially with piano recordings where the left hands playing will be slighty blurred. Sometimes the resonances from the cabinet is even higher than the sound from the driver !
Elac B6 :

Elac Debut B6 loudspeaker Measurements

Sidebar 3: Measurements I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Elac Debut B6's frequency response in the farfield; for the nearfield frequency response, I used an Earthworks QTC-40, which has a ¼" capsule and thus doesn't present a significant obstacle...

www.stereophile.com

”A prominent discontinuity in the traces just below 200Hz suggests that the enclosure has a serious resonance at that frequency. While setting up the speaker on my turntable stand to measure it, I noted that the cabinet seemed very lively—investigating the panels' vibrational behavior with a plastic-tape accelerometer, I found a very high-level, high-Q resonant mode at 188Hz that was present on all surfaces but highest in level on the side panels (fig.2). As HR wrote of the sound through the B6es of a recording of male voice and double bass, "I heard that vibrating box—not a little, but a lot. . . . [The speakers] were vibrating like sex toys!" There are also some high-level resonant modes present in the midrange.”

 

[Tangband]

The problems with time smearing in loudspeaker cabinets are sometimes very real, as you can read above - but this is not something that any manufacturer of mdf loudspeaker will ever admit.
ofcourse there are ways to make the mdf cabinet less bad using sandwich construction with matrix crossbracing, but there are very few of those in the market.

The density of aluminium is about 2,710kg/m3. Standard-grade MDF has a typical density of 680kg/m3 – 730kg/m3 A cabinet made of aluminum and 3 mm thick, has the same stiffness as a mdf cabinet that have 80 cm thick mdf walls.

 

[BrokenEnglishGuy]

Nice review by Erin.

Everything is relative. This 8331 is a better sounding loudspeaker than 8030c or 8330 , and goes deeper in the bass .

The price is very high, but one must compare with other loudspeakers to calculate if its worth the money.
This monitor is made for very small spaces or to be used on a desktop . In that context , It might be one of the worlds best loudspeaker and the 4500 dollar price maybe dont seem to high then…

Another thing - This 8xxx monitors have a loudspeaker cabinet made of metal, much stiffer than mdf . This alone also makes a point in sound quality. As a former DIY:er , making thousands of measurements on my own constructions and on the 8330 and my 8340 , the sound seem somewhat clearer than all other loudspeakers . Comparing the 8340 with a Kef R5 , there is clearly a difference where the Kef loudspeaker muddles the sound because of the mdf material releasing delayed energy. This is not something Amirms measurements shows, but you can hear it.

Im sure Genelec could produce a 8331 loudspeaker made of mdf that would cost 1000 dollars less, but the sound would also be worse.

The loudspeaker manufacturer Magico says :

http://www.bm.rs/Magico%20Alon%20Wolf%20Interview.pdf

Do you own the r5?

 

[thewas]

The density of aluminium is about 2,710kg/m3. Standard-grade MDF has a typical density of 680kg/m3 – 730kg/m3 A cabinet made of aluminum and 3 mm thick, has the same stiffness as a mdf cabinet that have 80 cm thick mdf walls.

That calculation is using the wrong assumption/equation and even then I don't know how you come up to 800 mm. The bending stiffness is not dependent on density but is proportional to E*I , where E is Young's modulus and I second moment of area.
Youngs modulus of aluminium is around 68 GPa and of MDF around 4 GPa, the second moment of area of a sheet is b*h³/12 so if the aluminium one is 3 mm thick then the MDF one should be only 7.7 mm thick , you see the large influence of third power in the thickness which reduces the 17 times material advantage to only 2.5 times thickness.

 

[Tangband]

That calculation is using the wrong assumption/equation and even then I don't know how you come up to 800 mm. The bending stiffness is not dependent on density but is proportional to E*I , where E is Young's modulus and I second moment of area.
Youngs modulus of aluminium is around 68 GPa and of MDF around 4 GPa, the second moment of area of a sheet is b*h³/12 so if the aluminium one is 3 mm thick then the MDF one should be only 7.7 mm thick , you see the large influence of third power in the thickness which reduces the 17 times material advantage to only 2.5 times thickness.

A typical good aluminum cabinett has it resonances higher than a typical mdf cabinett, because its stiffer and also less heavy. If the mdf cabinett has resonances at 300 Hz , then the alumina cabinett might have its resonances at 800 Hz with a much higher Q , thus the resonances will dissapear much faster .

The result is often a better sound with the aluminum cabinet.

 

[thewas]

A typical good aluminum cabinett has it resonances higher than a typical mdf cabinett, because its stiffer and also less heavy. If the mdf cabinett has resonances at 300 Hz , then the alumina cabinett might have its resonances at 800 Hz with a much higher Q , thus the resonances will dissapear much faster .

The result is often a better sound with the aluminum cabinet.

Again, the bending stiffness difference in thickness is similar to the difference in density, so if you would make them similarly stiff by using 2,5 times thicker MDF as I showed above also the mass would be similar and thus also the eigenfrequencies. Also MDF has higher material damping than aluminium due to its fibrous glued structure, a reason why most bells are from metal and not from wood. Also in loudspeaker enclosures its often advantageous to keep the eigenfrequencies low where they are less audible then in the mids, see BBC school of loudspeaker design. That doesn't mean that aluminium is a bad choice as an enclosure material, but that your argumentation is not expedient and per se it does not give a better sound. Thus also the main reasons why it is used on the smaller Genelec models are different, namely the freedom of three dimensional shaping, small thickness => higher internal volume and better heat dissipation, for their biggest, loudest and most expensive reference main monitors they use MDF.

 

[Tangband]

Again, the bending stiffness difference in thickness is similar to the difference in density, so if you would make them similarly stiff by using 2,5 times thicker MDF as I showed above also the mass would be similar and thus also the eigenfrequencies. Also MDF has higher material damping than aluminium due to its fibrous glued structure, a reason why most bells are from metal and not from wood. Also in loudspeaker enclosures its often advantageous to keep the eigenfrequencies low where they are less audible then in the mids, see BBC school of loudspeaker design. That doesn't mean that aluminium is a bad choice as an enclosure material, but that your argumentation is not expedient and per se it does not give a better sound. Thus also the main reasons why it is used on the smaller Genelec models are different, namely the freedom of three dimensional shaping, small thickness => higher internal volume and better heat dissipation, for their biggest, loudest and most expensive reference main monitors they use MDF.

Your conclusion is wrong. Loudspeaker cabinets made of metal has its resonanses at a higher frequency than a typical mdf cabinet. In demonstrations with real music , its very easy to hear that the sound is better if you have a really stiff cabinet.

The only reason to have mdf in loudspeakercabinets its because of low price.

Read what the constructor of Magico loudspeaker says about cabinets:

http://www.bm.rs/Magico%20Alon%20Wolf%20Interview.pdf

 

[thewas]

Your conclusion is wrong.

Nope, your generalisations are wrong, eigenfrequencies plainly depend on the material stiffness and mass, as shown per above equations.

Loudspeaker cabinets made of metal has its resonanses at a higher frequency than a typical mdf cabinet. In demonstrations with real music , its very easy to hear that the sound is better if you have a really stiff cabinet.

Stiffness is important but as said can be achieved also by thicker MDF which has also higher material damping, also the eigenfrequencies should be avoided to be in the psychoacoustic most audible frequencies, especially if they have low damping (ringing like a bell).

Read what the constructor of Magico loudspeaker says about cabinets:

http://www.bm.rs/Magico Alon Wolf Interview.pdf

A marketing interview as a proof, really?

As said an aluminium enclosure is per se not superior than a well engineered MDF one, let's talk with facts/measurements, here a well designed MDF example:

Source: https://www.stereophile.com/content/kef-ls50-meta-loudspeaker-measurements

Here the same acceleration response of a sub-optimal aluminium enclosure:

Source: https://www.stereophile.com/content...-701-wireless-loudspeaker-system-measurements

 

[Tangband]

This is a less good mdf cabinet , Elac b6.
This resonances gonna detach each pitch of the piano tone played by the left hand.
The result is a loudspeaker thats not pitch accurate.

 

[thewas]

Here is the difference between a typical good metal cabinett and a very good mdf cabinet.
Beware of the different scales that makes Kef meta look better than it is.

Nope, it is the opposite, the KEF plot scale is at much lower levels than on the Magico one. Here is the link as you didn't quote it https://www.stereophile.com/content/magico-m2-loudspeaker-measurements
By the way $56000 vs $1500 price.

The metal cabinet ( Magico on upper picture ) has no resonanses at all in the most problematic frequencies between 50-500 Hz .

Again wrong, highest audibility of resonances is in the mids, not below.

The high Q resonance at 800 Hz is inaudible, being 33 dB below the fundamental test tone.
The Kef Metas (below ) has a very good cabinet made of mdf sandwich, but you can still se some problems at 125 Hz , 21 dB below the test tone.

You read the plots wrongly, the peak of the Magico resonance is at a 33 dB level and the KEF peak at -21 dB, that is 54 dB lower, also since they are acceleration measurements their values cannot be directly compared or references to the other plots which are acoustic pressure measurements levels.

 

[Tangband]

I advice everyone to listen with your own ears .
I would think twice before buying something made of mdf when there is much better alternatives out in the market

 

[thewas]

I advice everyone to listen with your own ears .
I would think twice before buying something made of mdf when there is much better alternatives out in the market

I would advice to mainly trust measurements, especially since resonances are often difficult to identify and need to be stimulated by the signal accordingly.

Also repeatedly what mainly counts in engineering is the implementation, just the material is not enough and the material hype is mainly (ab)used in voodoo audio.

 

[Tangband]

This is a very interesting thread about different materials in loudspeakercabinets.

Audiogon Discussion Forum

I like the idea of a very strong inert metal cabinet. Besides Magico, Steinheim and T+A.. who else makes metal cabinet speakers?

forum.audiogon.com

Its from the manufacturer Verdantaudio.

Verdant Audio - Leading High End Audio Retailer and Importer

Verdant Audio retails some of the world finest high end audio equipment and brands.

verdantaudio.com

They have made REAL experiments with different loudspeaker materials .

” I have been on the fence about posting on this. These things get nasty at times and I lack the energy to argue with folks.

I have done extensive testing on cabinet materials in the startup of my company. One straightforward approach was too build the same cabinet out of multiple materials. You would be shocked at how much energy goes back into a cabinet and how much strength is really required to damp it.

The frequency with which the cabinet resonates is also extremely important. The lower the frequency, the greater the vibrations that are created and the more it impacts the ability for sound to travel forward from the cabinet and secondarily, the amount of distortion that muddies the sound coming from the drivers.

I used the same drivers, crossover and stuffing in cabinets that were identical other than the material and fine exterior measurements to variances in thickness of the materials.

When you do this, you will find that when you use stiffer materials like Carbon Fiber or even fiberglass stiffened by resin, the sound coming from the speaker will be more natural and fine detail is clear. When the cabinets are less rigid, but still resonate at a high frequency separation of detail will still be good but sound will be damped and dark. The solution is to alter the crossover and make the tweeter slightly more forward.

When the cabinet materials are less stiff and resonate at a lower frequency, the sound will be both dark and muddy. No matter how stiff the drivers are, there is nothing that a manufacturer can do to stop this.

Wood, no matter how heavy, stiff and dense, can’t match it. Some perform better than others, no question. But manufacturers are cost conscious and want to keep prices down. Take a stand mount speaker that is 8"w x 15"h x 10"d. Normal size. The cost of the MDF in that pair of speakers is about $7.50. Baltic Birch plywood will be about $40 and a hardwood would be $100-$400 depending on exactly how rare or exotic it is.

Composites will start above that plus the cost of a mold and much more expensive machining. Same for metal.

There is a reason why Magico’s, Wilson’s, Marten, Vivid, Wilson Benesch, etc... sound so good. The materials they use, whether composite or metal, resonate less and/or do it at a much higher frequency.

Given all that, what material do you think a manufacturer is going to pick when making a cabinet? Especially when everyone is using MDF and it is the industry standard. Unless you are going for high performance, even stepping up to Baltic Birch will add about $100 to your retail price and in hyper competitive markets where there are 80 speakers to choose from, every nickle counts.

MDF is used because it is cheap. And layered MDF does not significantly outperform solid MDF. It bends easier which is why it is used. Strength comes from layers with oriented strands of grain being laid down in opposite directions. OSB or standard plywood are examples of this. By it’s vary nature, MDF does not have oriented strands. It is stronger than particle board but well short of plywood. Having 7 or 9 layers of thin MDF glued together only makes sense when bending ”

 

[sweetchaos]

Video review is here: