Directivity study- woofers and subwoofers.

[tktran]

First up, the KEF LS60, a floor standing speaker only 13cm wide, with all the modern features of wireless Bluetooth, Airplay, streaming. No amplifier required- just plug in and go!

Data comes courtesy of Erin Hardison, who purchased it himself. Erin like to test drivers, previously having done so for DIYMobileAudio.com, as well as his (previous) website Medley's Musings, before rebooting as www.erinsaudiocorner.com. Recently he's been testing complete speakers, and has his own YouTube channel Erin's Audio Corner - YouTube



First the on-axis response, which is straight in front of that tweeter that's that you see behind the copper colored center of the midrange.



You may have noticed two things- the elevated and extended level of bass. And things look a little rough in the midrange. Perhaps you also notice the dip around 9-10Khz too. But let’s see how it all pans out in a standard CTA2034A "spinorama" representation.

Refresher: How to read Spinorama graphs:
sausalitoaudio.com/wp-content/uploads/2018/07/Interpreting-Spinorama-Charts.pdf





You may have noticed two things- the elevated and extended level of bass. And things look a little rough in the midrange. Perhaps you also notice the dip around 9-10Khz too. However this is because you're getting very high resolution of measurement with Erin's Klippel Near Field Scanner (This device is capable an extremely high resolution that beats ordinary windowed measurements. It is capable of a resolution of 2Hz, which is why you see warts and all)

DId you notice the DI line being negative below 200Hz? No? Well it can be hard to discern on a standard CTA2034A, which has a Y scale of 50dB.

Let's have a closer look:


The DI (red) trace read from the Y axis on the RIGHT. It's is almost -1dB, from 20Hz to 200Hz when it crosses the zero line.
What does that mean exactly?

Let's investigate further: Here's the line chart of horizontal responses: from directly in front of the tweeter, to your right and then behind the speaker (0 to +180 °)



Here's the horizontal response to the left side and then behind the speaker (0 to -180 °)



Here's the vertical response from the front to ceiling (0 to +180 °)


And the vertical response from front to floor (0 to -180 °)



These maps show that there is MORE bass directed to the side, and behind the speaker than to the front of the speaker.

Here are the POLAR MAPs: Horizontal



POLAR MAP: Vertical



These POLAR MAPS may help us understand the radiation pattern of bass when woofers are side mounted, and ports are rear mounted.

[tktran]

KEF Blade 2 Meta:

This one has four 6.5" woofers- 2 woofers on each side panel, combined with rear facing ports:

Data courtesy of Erin Hardison of www.erinsaudiocorner.com

[Reet]

Side firing woofers, greater power response than forward facing. That's got to mess with your brain a little. Interesting how the response of those is balanced, they seem to weigh power response over anything else.

[tktran]

Yes. Interesting the DI is -ve from 200Hz and below. We've seen some side firing woofers. Let's take a look at front firing woofers:

KEF R11 Meta uses four 6.5" mid-woofers in a front firing arrangement, with ports on the rear:
This one was measured by AudioScienceReview.com










A) The droop in the region below 100Hz perhaps is intentional, if this speaker has been tuned for near-wall placement.
B) Narrower vertical response than the Blade WWCoaxWW alignment
C) Directivity index is negative below 100Hz due to combination of front firing woofers but rear firing port