• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

[Edit] Why did Genelec [Do What They Did] on the 8381A?

Fredygump

Active Member
Joined
Nov 3, 2022
Messages
162
Likes
109
As the title states, why did Genelec choose to use a sealed subwoofer section with the 8381A speaker? What is a scientific analysis of this design choice?

I see the 8381A as the natural next step from the W371A, but obviously it is not "just" a scaled up version. It seems clear that Genelec is making different design choices with the W371A, and I'm trying to learn from those choices as I work on my own design.


It is interesting to me that Genelec are making the "ultimate" full range studio monitor, but it falls just a bit short of the consumer and home theater audio ideal of 20hz to 20khz. Certainly the 8381A has enough headroom to achieve flat response to 20hz, but that is not how they measured it.

That's a long winded way of asking why Genelec chose to go sealed on the subwoofer section and sacrifice a little low end extension, when they are already known to produce excellent ported subwoofers that extend below 20hz?

If possible, I'd like to discuss this question from the perspective of an engineer that is making these decisions.



(I'm asking because I have a speaker design project following the speaker layout of the W371A/ 8381A speakers. I'm currently using a ported subwoofer like the W371A. But with the introduction of the sealed subs on the 8381A, I'm wondering why Genelec chose not to use ported subs, and should I also switch to a sealed design? I've seen many discussions about sealed vs ported, and mostly they just say that ported can sound just as good as sealed, and if sealed was better, you probably couldn't hear the difference because of room issues. But then Genelec chooses a sealed subwoofer when they are good at ported subs....)
 
Last edited:
The W371A is no ported sub, but a combination of a closed (top-front) and vented (bottom-rear) driver.
It uses a software for both channels, that has different options to adapt to the situation.
Nothing you will DIYS in your basement, sorry.
 
Crap...
No, they didn't - https://assets.ctfassets.net/4zjnzn...d8fc6f029aad9fcd87/8381A_Operating_Manual.pdf

"Towards low frequencies, the bass reproduction moves from the front 381mm (15 in) woofer to the bottom enclosure housing two recoil-compensated 381 mm(15 in) woofers in a bass reflex enclosure –with a port opening towards the back of the enclosure"

Ooops...


You say this, and then I start examining pictures. Now I see it. A black slot in the back of a black speaker...and almost all photos are from the front.


But is it still worth asking why they didn't seek to achieve "the holy grail" of flat response down to 20hz?
 
The W371A is no ported sub, but a combination of a closed (top-front) and vented (bottom-rear) driver.
It uses a software for both channels, that has different options to adapt to the situation.
Nothing you will DIYS in your basement, sorry.

I copied the driver arrangement of the W371A, and I added a coaxial driver. So it ended up being a mini-8381A before they announced the 8381A.

And you are right, not something I would build in my basement. I built it in my garage.


20230716_144104_resized_1.jpg
 
But is it still worth asking why they didn't seek to achieve "the holy grail" of flat response down to 20hz?
Would it sell better? What would be the point? Few hz lower wouldn't make any real world difference.

Likely 2x15" with ~150 litre net volume is simply too small for lower port tuning. I'm sure they want to keep respectable SPL numbers in the brochure instead of artificially EQing it lower.

1236A is 17.5hz@-6dB, but it has 2x18" and around 600 litres of cabinet. (Could be much less, not sure how the internals work)
 
Last edited:
But is it still worth asking why they didn't seek to achieve "the holy grail" of flat response down to 20hz?
First, not many mains go to 20Hz. Those that claim are including room gain, Genelec does not. So yeah, 'holy grail' does apply. :cool:
Not many woofers can do 20Hz anechoic. Even the most stout 18" or 21" woofers will struggle to do 20Hz anechoic at the SPL capability of the 8381s. In-room, with correct placement, yes 20Hz is doable with many systems. The key is placement, and most often the best placement for mains is not the same place as the best placement for bass, and in fact can be the worst placement in a room. The deeper the speaker goes, the more critical it is to be able to place the bass speakers at various places in the room including room boundaries and corners where they can be used to manage the bass and resulting room modes, give smoother and deeper bass than any mains can provide.

Like @hedge posted, 1236A can do 20Hz. I would still use them with subs since the in-room bass response would be much smoother.
 
Challenged by my mistake and the generosity of forum members, I went on a quest to model a cabinet with the same size and output subwoofer as the 8381A ported subwoofer. It quickly became apparent that the 124dB criteria was the most difficult constraint.

I came up with this ported cabinet that matches the SPL claim of 124dB, with an F6 of 20hz, and staying within the excursion limits of the driver.

(I made a very rough calculation that the interior volume would be around 140L. The FaitalPRO 15XL1400 seems to do the job better than any other that is currently entered into my version of VituixCAD. I'm not sure if this is the driver Genelec is using, but there is a resemblance.)

2025-01-17 16_41_21-Enclosure_ C__Users_Public_Documents_VituixCAD_Enclosure_VituixCAD_Drivers...jpg



Using the same cabinet size and driver, but reducing SPL to a mere 120dB SPL, it is not a problem to achieve the coveted flat response. (Port design is a problem that would require some attention.)

2025-01-17 17_38_29-.jpg



I tried to see how close I could get with a sealed design, but it seems pretty impossible. As a joke I modeled the M-Force 30" subwoofer in a 140L sealed cabinet, and it was able to achieve 20hz @ ~124dB. But it also is requiring 12,600watts!

For fun: M-Force 30" subwoofer, sealed 140 liter cabinet.

2025-01-17 17_01_43-Enclosure_ C__Users_Public_Documents_VituixCAD_Enclosure_VituixCAD_Drivers...jpg




So after all of this, why the 124dB SPL requirement? I know that mastering engineers care about hearing transients accurately, but they are mortals like us, who will be listening at somewhere around 80dB? Of course marketing people like to impress with big numbers, but I don't see the utility. Nobody is going to set them up for live sound at an outdoor event?

With my project, I have been fully aware that my subwoofer has the lowest SPL capability of all the drivers I'm using. But at the same time, I have 2 subs that can each play 20hz @ ~110dB! It's more than I will ever utlilize! And it's "just" a pair of 12" sub drivers.

But then I look at Genelec's idea of the ultimate speakers and wonder if there is something audible to be gained from a design that has so much headroom?
 
if there is something audible to be gained from a design that has so much headroom?
Marketing value, for sure.

And, in the studio if you are working on uncompressed raw tracks, the dynamic range can be really high. It's conceivable that you'd want the raw audio to come through without distortion, meaning you need to accommodate unusually high peaks.

And anecdotally I've heard mains are in part a client-service piece of equipment. Some muso comes in and wants to hear their stuff "LOUD" and if you can impress them enough it improves their opinion of your studio. A clean 124dB is probably more than anyone can shrug at.

Lastly, mains will tend to be a bit further away - if you're several meters away and you still want massive peaks, you need to start with quite a lot of juice.
 
It sounds to me like everyone is assuming the marketing department chose the 126dB max SPL, and they stuck it to the engineers to figure out how to accomplish it? And therefor the bass roll-off at 30hz is the compromise required to achieve the SPL target?

But is it possible that the engineers are being intentional? Before I posted I was looking at reverberation time, and obviously lower is better. I watched a video by a recording studio showing reverberation time, and his monitors were rolling off at 60hz. Apparently this was by design, and it seemed to me that it takes a lot of confidence to tell the internet that you don't need low frequencies!

Would rolling off low frequencies at 30hz have a positive effect on sound quality? Obviously low frequencies are the hardest to control. So if you roll off at 30hz, your 25hz content is still clearly audible (-3dB), and I think most of us will agree that 20hz is essentially inaudible.

But consumer audio is obsessed with having that flat line down to 20hz; because it might exist, therefore we have to have it. That's the Holy Grail thing. But is it also a short sighted view of audio and sound quality? If I want sub-20hz for movies, I could put a butt-kicker in the floor to give the room shaking effect, without worrying about the inefficient coupling of speaker drivers to the air and then to me and the structure around me....

I'm asking becaulse nobody on the internet is contradicting the self-imposed 20hz requirement for subwoofers. I was thinking maybe I should change my sub's tuning frequency to mimic what Genelec did. But I can't make up my mind if this is a clever thing to do, or if it is a compromise like previous comments have suggested.
 
Back
Top Bottom