GENELEC GO HIGH SPL

[svart-hvitt]

Yesterday, Genelec added a couple of additions to their product range to offer audio professionals and enthusiasts high SPL in a small package:

S360 SPEAKER: https://www.genelec.com/studio-monitors/sam-master-studio-monitors/s360-sam-studio-monitor

7382A SUBWOOFER: https://www.genelec.com/studio-monitors/sam-studio-subwoofers/7382-sam-studio-subwoofer

The new products were launched on an AES conference in Tokyo on immersive audio. This is Genelec’s new brochure on multichannel audio, also launched yesterday:

https://www.genelec.com/sites/default/files/immersive_audio_brochure_180806_web.pdf

The subwoofer is an update to the old 7073a, which Keith Yates (http://keithyates.com/about-us/) tested and reviewed in 2004:

https://www.soundandvision.com/content/way-down-deep-i-genelec-hts6

You would need two old 7073 to achieve the same maximum SPL as that of the new 7382 (129 dB). So you could actually argue that the new 7382a is «big sound in a small package».

The S360 speaker is a two-way, compression driven tweeter. The horn design enables SPL of 118.

A stereo package with two S360s and one S7382 would set you back about $20k. That may be a lot, but are there many turnkey systems around that can be safely driven to 120 dB (bass could be boosted way higher) without breaking a sweat?

This may sound like a commercial, but I think it’s interesting to see how serious, science-driven companies solve audio problems. In the past few years we have had the Devialet Phantom (only consumer oriented) and the Kii Three (both pro and consumer oriented) as examples, where the manufacturers claim big or great sound in a small package. When Genelec solve the same problem, maximum dynamics and high precision, we see the following:

1) Compression driver chosen for tweeter to achieve highest SPL in a given footprint.
2) To achieve the lowest frequencies at very high SPL you need a 500 litres box of 150 kg.

So there seem to be no free lunches, still, if you want the highest dynamics (films, rock concerts, orchestras on a realistic SPL level).

And don’t forget, the S360 speaker and the 7382a subwoofer were introduced to enable multichannel sound on reference level, where needs may be a bit different than for domestic audio in stereo.

Any thoughts on Genelec’s recent design choices? Could higher SPL with less distortion and more precision be achieved in a smaller footprint at a lower cost?

 

[Hrodulf]

Overall this is an interesting development. 1032 series so far have sported a 10” woofer coupled with their regular 1” Seas alu dome tweeter. Compared to these older series designs, it’s evident that Genelec has opted for a more curved enclosure and upped the SPL capability with a compression driver. For most traditional hi-fi and studio monitor designs it really is the tweeter which limits max SPL. It’s hard to cool these units, therefore power handling is around 100W with traditional efficiencies in the lower to mid nineties. Genelec’s choice of compression driver and waveguide/horn configuration is interesting, as theses can have problems with high order modes (see Geddes work) which limit their sound quality.

I’d say it’s fair to ask, how much this speaker is a studio monitor and how much a glorified PA top speaker. Interestingly enough Genelec hasn’t published a proper datasheet for this product, only a brochure with polar response. It seems to have the usual vertical polar pinch at the crossover frequency. The compression driver is crossed very low and I’d expect it to struggle at these lower frequencies, if large SPL are required.

 

[watchnerd]

Competing with JBL 708P? (8 inch woofer, 114 dB max spl)

http://www.jblpro.com/www/products/recording-broadcast/7-series/708p#Specs

 

[andreasmaaan]

Any thoughts on Genelec’s recent design choices? Could higher SPL with less distortion and more precision be achieved in a smaller footprint at a lower cost?[/B]

I’m sure it’s a very good speaker like all Genelecs I’ve known. IME, a typical good PA speaker of the same size would be designed to achieve maybe 6dB higher SPL but with a -6dB point maybe 10Hz higher.

So I see this particular design compromise as the main distinguishing feature of this Genelec.

Or to answer your question, higher SPL could be achieved (not sure about distortion as it’s not spec’d) at the expense of low frequency extension.

Top shelf parts from leading PA manufacturers for a speaker like this would probably cost about €600-€800 wholesale to a manufacturer the size of Genelec is my guess. That’s without knowing anything about the cost of the case. Not sure what they’ve actually used ofc. But it would mean a decent markup.

Would like to see measurements.

 

[svart-hvitt]

Competing with JBL 708P? (8 inch woofer, 114 dB max spl)

http://www.jblpro.com/www/products/recording-broadcast/7-series/708p#Specs

Well, the S360 is much bigger so a direct comparison is not fair.

However, they do compete in a certain segment, where low distortion at very high SPL is needed. While music plays at a «linear» SPL (low deviation around the average), films are another matter. Films go from 50 dB to explosions of 120 dB and peaks of 125-130 dB. If you want to play back such dynamics, conventional tweeters don’t work. And while horns have relatively higher distortions at lower SPL, they have relatively lower distortions at very high SPL, right?

So your SPL and dynamics needs decide whether you choose horn or conventional tweeter, wouldn’t you agree? And for some reason which is not well understood, some even prefer horns for lower SPLs.

I think of Genelec’s S360 as an attempt to cater for another audience; i.e. the multichannel people, which may not be primarily music oriented.

But it would be interesting listening to them when playing music as well. Will the higher horn distortions at lower SPL colour the music in a malignant way?

 

[andreasmaaan]

Will the higher horn distortions at lower SPL colour the music in a malignant way?

Why do you say the horn will create higher distortion at lower SPL?

 

[svart-hvitt]

Why do you say the horn will create higher distortion at lower SPL?

Isn’t that the trade-off of horns? More distortion at lower SPL than conventional tweeter designs? Or is horn a win-win?

I know many horn advocates claim win-win, but I thought it was more complicated. I have never seen the definite discussion on this theme, though... But that may be due to my ignorance.

So if you know of the canonical text on «horns vs conventional tweeter», I am all ears.

 

[andreasmaaan]

Isn’t that the trade-off of horns? More distortion at lower SPL than conventional teeeter designs? Or is horn a win-win?

I know many horn advocates claim win-win, but I thought it was more complicated. I have never seen the definite discussion on this theme, though... But that may be due to my ignorance.

So if you know of the canonical text on «horns vs conventional tweeter», I am all ears.

Yeh, I’m not aware of a definitive study on the topic that involves measurements, but I know of no theoretical reason why a horn shouldn’t reduce distortion of a given driver (all else being equal) at any given SPL, low or high, down to the frequency at which the horn stops loading the driver.

Given the claim horns distort more at lower SPL makes no theoretical sense, I’d say it’s the person making it that would want to show measurements to support it

Also worth noting that all Genelec models employ a high frequency horn. The difference here is that this design uses a compression driver rather than a conventional dome.

 

[andreasmaaan]

@svart-hvitt it's hardly a definitive study, but Heissmann Acoustics have measured a few dome tweeters both with and without horns.

Here for example is the Seas Noferro 900 measured without and with a conical horn at 85, 90, and 95dB.

(Unfortunately the GIFs don't work on the English version of the site but I've copied them from the German version below. Also note there is a typo on the page showing the measurements without the horn - distortion is actually under 3% @ 95dB, not 0.3% as the text states.)

A bit messy with the choice of moving GIF for this, but we can see that the horn gives us a 10-15dB reduction in distortion in the 1-2KHz range at all measured SPLs once the frequency response is equalised, and lesser but still significant reductions at higher frequencies up to about 6KHz, which must be about where it stops loading the driver.

It's not shown here, but the other advantage from using a horn like this will be better controlled directivity throughout the tweeter's whole passband.

I actually find it quite hard to understand why so many manufacturers persist with the high distortion levels and erratic polar responses produced by direct radiating dome tweeters.

Without horn:

With horn:

 

[andreasmaaan]

I should add that the benefits might not always be as great as the 15dB distortion reduction from the combination above. It depends a lot on the geometry and size of the horn and the geometry of the dome. But there should nevertheless always be a significant benefit in terms of distortion reduction from horn loading a dome tweeter (or any driver for that matter).

The trade-off with horn-loading a dome however is that it tends to create some diffraction at the throat of the horn, which will be most significant at the highest frequencies (Geddes calls these diffraction effects "higher order modes"). This is probably going to be a lot less audible though, if at all, than a 10-15dB increase in distortion from not horn-loading, which will be right in the ear's most sensitive range of 1-4KHz (depending on the horn's geometry and size).

This throat diffraction can be reduced by use of a compression driver with a well-designed phase plug, which produces a wavefront very close to a planar wave by equalising the distances from each point on the diaphragm to the compression driver exit. Diffraction can further be reduced by correctly matching the exit angle of the compression driver to the entrance angle of the horn's throat so that there are no discontinuities, and by taking care with the rate and geometry of expansion of the horn between the throat and the walls, which is often not the case due to these matters being poorly understood until recently and/or sloppy design among some PA speaker manufacturers, where compression drivers are normally used. Also, there are also trade-offs to be made between horn geometries that minimise diffraction and those that maximise loading. Finally, many compression drivers do not have great phase plugs and therefore might create their own unwanted diffraction internally, before the soundwave even sees the horn.

Anyway, a horn-loaded compression driver should generally have significantly lower distortion than a horn-loaded dome tweeter (all else being equal) at any given SPL, due to the compression chamber further loading the driver and therefore requiring less displacement of the diaphragm.

There is however a trade-off at higher SPLs, because beyond a certain point the high particle velocities of the air in the compression chamber may cause the air pressure to rise to a high enough level that it begins to significantly warp the wavefront (there is a non-linear relationship between pressure and volume in gases). This particularly increases odd-order harmonics. Fortunately, however, this effect is most powerful at extremely high SPLs, and at higher frequencies, which means that these raised harmonics are more likely to lie outside the audible range.

Interestingly, this phenomenon actually goes against the common wisdom among audiophiles, which is that compression drivers distort more than domes at lower SPLs. As you can see, the inverse is in fact true: as displacement increases in a dome, distortion tends to rise linearly until the driver gives up at around Xmax. In a compression driver, on the other hand, as displacement increases beyond a certain tipping point at which air pressure in the compression chamber gets high enough to have a more than negligible effect, distortion tends to rise faster than linearly (just how fast depends on the air pressure in the chamber at a given SPL and on whether we're looking at odd or even harmonics). It's just that "high SPL" for a dome isn't even close typically to "high SPL" in respect of a compression driver.

Also, because the distortion in a compression driver at high SPLs will likely be due to high particle velocity rather than excessive diaphragm displacement, a compression driver will be less likely to tear apart than a dome at the point at which it starts to distort severely.

There are of course a lot of other factors that are dependent on diaphragm material and design, phase plug design, and horn design. But I've tried to summarise the basic concepts at play here.

EDIT: added some further info that might be of interest.

 

[svart-hvitt]

@svart-hvitt it's hardly a definitive study, but Heissmann Acoustics have measured a few dome tweeters both with and without horns.

Here for example is the Seas Noferro 900 measured without and with a conical horn at 85, 90, and 95dB.

(Unfortunately the GIFs don't work on the English version of the site but I've copied them from the German version below. Also note there is a typo on the page showing the measurements without the horn - distortion is actually under 3% @ 95dB, not 0.3% as the text states.)

A bit messy with the choice of moving GIF for this, but we can see that the horn gives us a 10-15dB reduction in distortion in the 1-2KHz range at all measured SPLs once the frequency response is equalised, and lesser but still significant reductions at higher frequencies up to about 6KHz, which must be about where it stops loading the driver.

It's not shown here, but the other advantage from using a horn like this will be better controlled directivity throughout the tweeter's whole passband.

I actually find it quite hard to understand why so many manufacturers persist with the high distortion levels and erratic polar responses produced by direct radiating dome tweeters.

Without horn:
View attachment 15004

With horn:
View attachment 15005

Thanks for the charts.

But I had implicitly in mind horn+compression tweeter as design, as in S360, while discussing the need for high SPL in certain horn speakers. High SPL potential is what sets S360 apart from other Genelec’s of similar size.

 

[andreasmaaan]

Thanks for the charts.

But I had implicitly in mind horn+compression tweeter as design, as in S360, while discussing the need for high SPL in certain horn speakers. High SPL potential is what sets S360 apart from other Genelec’s of similar size.

Yeh I understand. I tried to address this more in post #10.

The short summary would be that even at low to mid SPLs a well-designed horn-loaded compression driver should be capable of lower distortion than a well-designed horn-loaded dome.

 

[Ilkka Rissanen]

Would like to see measurements.

Hi there,

Measurements are available in the operating manual, link below. If you have any questions, please let me know and I would be happy to help.

https://www.genelec.com/sites/default/files/media/s360_operating_manual.pdf

 

[andreasmaaan]

Hi there,

Measurements are available in the operating manual, link below. If you have any questions, please let me know and I would be happy to help.

https://www.genelec.com/sites/default/files/media/s360_operating_manual.pdf

Thanks. Always good to see manufacturers publishing measurements as Genelec does

 

[changer]

Hey @hardisj, would you test this ultimate big-small two-way for us sometime, when you find some leasure?