PMC Twenty.21 Bookshelf Speaker Review

[Thomas_A]

Off-axis performance is also pretty garbage. You fix some of the 5khz+ issues, but introduce new issues below that. Its just badly designed. With regards to your comments about frequency response: the research shows that ruler flat speakers are preferred by everyone.

Just a note again regarding that ruler flat speakers are preferred by everyone. It is certainly correct as principle, but given the timbral errors in different systems (particularly mono-stereo), there is no absolute preference by everyone. If it a flat response is preferred for a mono source with one center speaker, it cannot at the same time be preferred for a mono source in a stereo setup. The equation is just impossible.

 

[Koeitje]

Just a note again regarding that ruler flat speakers are preferred by everyone. It is certainly correct as principle, but given the timbral errors in different systems (particularly mono-stereo), there is no absolute preference by everyone. If it a flat response is preferred for a mono source with one center speaker, it cannot at the same time be preferred for a mono source in a stereo setup. The equation is just impossible.

As far as I know is mono the best way to identify differences in preferences between loudspeakers and adding more will just make it harder to establish preference (but in the end it is still the same preference order!).

 

[GelbeMusik]

Just a note again regarding that ruler flat speakers are preferred by everyone. ... The equation is just impossible.

To name it 'impossible' is true. What additionally wasn't considered is the vastly varying decay time in total, and its change over frequency, aka RT60 in living rooms. The geometry takes a decisive role, since we encounter the possibility of early reflections interference at the listening position etc pp and so forth and more endlessly.

The spinorama may be a valid predictor, but only on average and is by that maybe valuable for an OEM. But is actually not the criterion for an end consumer, who has (a) a measurement microphone and (b) an EQ at hand. There are people here who rather EQ their gear to the spinorama than to what they actually find at home. I think such attempt is indicative of an overestimation of its importance …

On the other hand, the speaker in question here leaves nearly no room for a positive verdict. Nearly every thing else is more easy to integrate to whatever room one might have in mind. The distortion sky-rockets in midbass, no bass extension to speak of, lower midrange contaminated. I think it is a waste of time to discuss it outside of a monitoring context. The exaggerations in FR, and the HD point to a quite particular use-case, in that these little guys are just literally monitors, focusing on quite a limited set of properties of the program. They are obviously without any doubt not made to enjoy music. ( same with BBC's LS3/5, which is often well misunderstood )

 

[Thomas_A]

As far as I know is mono the best way to identify differences in preferences between loudspeakers and adding more will just make it harder to establish preference (but in the end it is still the same preference order!).

Sure it is the simplest way, but if the preferred response of a mono speaker is perfectly flat, you will hear that the timbre will change playing the same mono source when putting the same perfectly-flat speakers in a stereo setup. Toole, Shirley et al knows this. Their suggestion is to skip stereo and use mc audio.

 

[tuga]

There are dozens of examples of very good sounding speakers which don't measure ruler flat.
Equally there are dozens of very bad sounding speakers which do measure ruler flat.
If there was a "correct" target frequency response everybody would be using it.
There isn't because there are too many variables involved. Everybody hears differently and the human hearing sensitivity changes hugely across the frequency bands. A flat speaker frequency response to a flat microphone doesn't mean a flat response to the ear brain system, when you consider how hearing sensitivity changes with frequency.
To judge a loudspeakers performance on how close it comes to a flat line is not taking into account the full picture.
And that is coming from someone who measures speakers for a living.
Of course one can use DSP alongside loudspeaker drive units, cabinet enclosures and crossover components to achieve a flat response however many designers don't have DSP available and have to as much as they can in the box.
Even if you do get a flat response out of the box your room will EQ the system as well as your ear brain system.
So you still have to listen and measurements can only be used to guide you in the right direction.

No.
Sounds good is subjective anyway.
There's nothing wrong about liking a speaker that doesn't not perform well in the test bench but it doesn't make it a good (accurate) speaker.

 

[richard12511]

Wow, I'm honestly surprised at how terrible these are. No doubt they sound terrible, too. If these were $50 I could give them a pass, but even then, the $100 Pioneer speakers probably sound much better than these.

 

[richard12511]

PMC recommend that you listen to twenty series loudspeakers off axis. This is from the twenty 21 manual:
To further enhance the audio picture or soundstage the speakers can be angled/toed-in’. Start with the speakers angled so they will cross approximately 50cm (2ft) behind the listening position. (See stereo set-up diagram) Varying this angle will also subtly affect the vividness of the audio picture, so again experiment.
Over the years (and this is an old design) they have further developed this concept. This is from the more recent twenty 5 21i manual:
To enhance the audio picture/soundstage and sound balance, the speakers can be angled/toed-in. With the speakers facing straight ahead play a well recorded vocal track. Gradually toe-in both speakers by small increments (max 5° at a time) (see stereo set-up diagram) until the voice is vivid and centrally placed. You can ensure this is best position by going ‘one step too far’ then returning. Then, use a track with extended high frequencies such as cymbals, check that they sound clear but not overpowering. If they sound too loud or harsh subtly toe the speakers out by very small increments until you achieve the ideal balance; then repeat both listening tests to confirm.
So they clearly expect listeners to listen off axis and to use the associated HF roll off to achieve a "balanced" response. Had this of been considered the frequency response measurements would be, flatter and more useful.
As it stands the on axis frequency response measurements are not valid.
Might be an idea to get a better understanding of the intended use of the system before posting findings.
I'm sure the lovely folk at PMC would be only too happy to engage to prevent scenarios like this.
My experience of PMC is that they are a very good company with sound engineering pedigree who make great products.
There are dozens of examples of very good sounding speakers which don't measure ruler flat.
Equally there are dozens of very bad sounding speakers which do measure ruler flat.
If there was a "correct" target frequency response everybody would be using it.
There isn't because there are too many variables involved. Everybody hears differently and the human hearing sensitivity changes hugely across the frequency bands. A flat speaker frequency response to a flat microphone doesn't mean a flat response to the ear brain system, when you consider how hearing sensitivity changes with frequency.
To judge a loudspeakers performance on how close it comes to a flat line is not taking into account the full picture.
And that is coming from someone who measures speakers for a living.
Of course one can use DSP alongside loudspeaker drive units, cabinet enclosures and crossover components to achieve a flat response however many designers don't have DSP available and have to as much as they can in the box.
Even if you do get a flat response out of the box your room will EQ the system as well as your ear brain system.
So you still have to listen and measurements can only be used to guide you in the right direction.

Do you have research to back up these claims? The research I'm aware of contradicts most of what you claim to be true, but I'm certainly open to new research.

 

[Thomas_A]

To name it 'impossible' is true. What additionally wasn't considered is the vastly varying decay time in total, and its change over frequency, aka RT60 in living rooms. The geometry takes a decisive role, since we encounter the possibility of early reflections interference at the listening position etc pp and so forth and more endlessly.

The spinorama may be a valid predictor, but only on average and is by that maybe valuable for an OEM. But is actually not the criterion for an end consumer, who has (a) a measurement microphone and (b) an EQ at hand. There are people here who rather EQ their gear to the spinorama than to what they actually find at home. I think such attempt is indicative of an overestimation of its importance …

On the other hand, the speaker in question here leaves nearly no room for a positive verdict. Nearly every thing else is more easy to integrate to whatever room one might have in mind. The distortion sky-rockets in midbass, no bass extension to speak of, lower midrange contaminated. I think it is a waste of time to discuss it outside of a monitoring context. The exaggerations in FR, and the HD point to a quite particular use-case, in that these little guys are just literally monitors, focusing on quite a limited set of properties of the program. They are obviously without any doubt not made to enjoy music. ( same with BBC's LS3/5, which is often well misunderstood )

Agreed that the speaker presented in this thread has nothing to do with what a good speaker should look like, whether it should be used in mono or stereo configuration. It is a terrible result overall.

 

[BYRTT]

Not to know if below visual EQ decoration for ASR sample of Twenty.21 will sound good to anyones ear but it looks quite positive relative to pages back in general ...

 

[Thomas savage]

Do you have research to back up these claims? The research I'm aware of contradicts most of what you claim to be true, but I'm certainly open to new research.

They say they measure speakers for a living , @Listen first it would be helpful if you could then declare your industry affiliations.

 

[amirm]

I'm sure the lovely folk at PMC would be only too happy to engage to prevent scenarios like this.

Well, those lovely folks would do well to make their own measurements and provide them in their marketing material for the speaker. If they do not, they either don't have them or don't think it shines a good light on their product. Regardless, if they had published such measurements, it would have made it easy to verify our work with them. That they don't, is on them, not me.

Anyway, instead of complaining to me, go and message them and see if they like to engage us. Otherwise, since they did not provide a review sample, nor have responded to this review or contact me, then I am moving on to the next review.

 

[amirm]

PMC recommend that you listen to twenty series loudspeakers off axis. This is from the twenty 21 manual:
To further enhance the audio picture or soundstage the speakers can be angled/toed-in’. Start with the speakers angled so they will cross approximately 50cm (2ft) behind the listening position. (See stereo set-up diagram) Varying this angle will also subtly affect the vividness of the audio picture, so again experiment.

That is the way I listened although I did not make precise measurements as such. And I do experiment by moving my seating position. Above is pretty generic advice on speaker positioning so not sure why you think this is something unique to PMC to be followed.

 

[amirm]

So they clearly expect listeners to listen off axis and to use the associated HF roll off to achieve a "balanced" response. Had this of been considered the frequency response measurements would be, flatter and more useful.
As it stands the on axis frequency response measurements are not valid.

They provide no measurements to back this stance. But we do:

The dashed green line is the Listening Window. It includes an average of 9 measurements including +-10 degrees vertical and +-30 degrees horizontal. Despite this, the frequency response errors basically remain the same.

 

[MZKM]

They provide no measurements to back this stance. But we do:

The dashed green line is the Listening Window. It includes an average of 9 measurements including +-10 degrees vertical and +-30 degrees horizontal. Despite this, the frequency response errors basically remain the same.

To be fair:

The response is more neutral at 20°-30°.

 

[amirm]

My experience of PMC is that they are a very good company with sound engineering pedigree who make great products.

Well, in this forum, we don't go by stories behind companies. We want to listen to music, not their stories. If those stories result in good performance that we can verify -- not some anecdote that they "sound good" -- then we praise them. Otherwise we remain grumpy. There are a lot of good speakers with good stories as well. Surely that is the combination you want, not just the ones with good stories.

 

[amirm]

To be fair:

The response is more neutral at 30°. However, you do lose a ton of SPL >12kHz or so, maybe 20° would be the ideal middle ground.

Better is not the same as good. There is still 4 dB rise around 10 khz than the dip around 4 kHz. And of course it does nothing for aberrations in bass.

 

[amirm]

To judge a loudspeakers performance on how close it comes to a flat line is not taking into account the full picture.
And that is coming from someone who measures speakers for a living.
Of course one can use DSP alongside loudspeaker drive units, cabinet enclosures and crossover components to achieve a flat response however many designers don't have DSP available and have to as much as they can in the box.
Even if you do get a flat response out of the box your room will EQ the system as well as your ear brain system.
So you still have to listen and measurements can only be used to guide you in the right direction.

I did listen. And I did attempt to EQ. Did you not notice the directivity error? You can't fix that with EQ because it is upstream of the speaker so it can't impact that. Both on and off-axis will be changed together resulting in no improvement in directivity.

That said, you could probably make it sound better than it is but why? You spent this much money and now you have to try to make something out of the speaker? There are so many better choices out there that don't require jumping through hoops so much.

I don't know how someone measuring speakers for a living is not offended by measurements like this. If you measure a speaker and it looks like this, do you not have an opinion about its design? Do you just say it is as good as any other speaker?

 

[MZKM]

And of course it does nothing for aberrations in bass.

Is that being chalked up to the port being out of phase in that region, or is the woofer inherently down in that region?

 

[BikeSmith60]

Well, those lovely folks would do well to make their own measurements and provide them in their marketing material for the speaker. If they do not, they either don't have them or don't think it shines a good light on their product. Regardless, if they had published such measurements, it would have made it easy to verify our work with them. That they don't, is on them, not me.

Anyway, instead of complaining to me, go and message them and see if they like to engage us. Otherwise, since they did not provide a review sample, nor have responded to this review or contact me, then I am moving on to the next review.

I hope you do get to the ATC SCM19 when time allows, would be an interesting comparison, even if the natural competitor to the PMC x.21 would be the SCM11. FWIW, this weekend I will home demo both the PMC Twenty5 22 and the ATC SCM19. Heard both already on my own amp at dealer. Strictly no show-stopper grievances with either model during the demos, even if their sound presentations are quite different. The ATC was particularly impressive, as an infinite baffle, for clarity, cohesiveness and LF definition and texture. Unfortunately, they are somewhat FUGLY for a domestic setting while the new PMC Twenty5 22i looks nicer. For me, SQ will decide and I'll just have to deal with the wife!
Brgds.

 

[amirm]

I hope you do get to the ATC SCM19 when time allows, would be an interesting comparison, even if the natural competitor to the PMC x.21 would be the SCM11.

I have measured it but need to redo something and have an urgent review to get out before it. So expect it by tomorrow if not later tonight.