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This Beta-8 version of the Flex-8 stands apart from the others as the woofer has much higher efficiency (~91dB / 2.83v or 1W/1M). This high efficiency however comes at the expense of bass extension (F3 ~72Hz 4pi) so subwoofers would be required for most content unless you don't need much bass like basic background music / radio.
Along with the high efficiency comes higher power handling then the other woofers, this results in much higher maximum SPL from the design. It also means lower compression, as measured there is only about 0.5dB on average from the woofer at the 105dB sweep compared to 75dB which considering that's 1000x the power level is not bad at all.
Frequency response from the Beta-8 is also very good, a nice even response without any large issues. This makes the tonality excellent with good detail and smoothness, things sound like they should.
Harmonic distortion performance is the only weakness of this woofer, while not bad at lower levels it ramps up more then the others at high levels. Not sure why it suffers more as power though the driver is far lower then the other designs at equal SPL. I didn't notice anything bad during normal playback as the levels still stay low enough that they remain masked by general content.
The high frequency performance/sound quality is largely the same in all the designs so this section will likely be a cut/paste for each. The LaVoce DF10.101LS with the Celestion H1SC-8050 is a very nice combo, the smooth easy to work with frequency response results a very clean clear uncolored high frequencies with remarkably low distortion and compression. The high frequency driver has to work very little in this design so its composure is maintained well beyond the point where the 8" woofers are begging for mercy. The only things to point out are the slightly more narrow coverage of the horn then most designs and the drop in high frequency output past 16kHz. For the cost I don't mind as they are not glaring issues that you notice immediately if you notice them at all and the narrow dispersion can actually be a benefit depending on the desired use of the speakers or the type of sound you like.
The high sensitivity and high power handling certainly make this design the variant of choice if looking for high output levels for a large home theater or blasting music in a garage assuming you have good subwoofer to pair with it. It will even do so without needing a high powered amp but at the same time it can handle amps in the 200-450w range with the appropriate crossover so very high output levels are achievable if needed (115dB+ from a pair of speakers).
Don't let the talk of high output scare you away, these also sound incredibly good at lower levels with a frequency response that is within +-1dB from 100-10khz the detail and clarity is excellent and exceeds many designs that can be purchased for even far greater price then these can be built for.
Crossover Schematic:
On this crossover the C1 cap on the highpass should be polypropylene and C2/C3 and C5 cap on the low pass designed to be non-polarized electrolytic.
Resistors are standard 10w wire-wound.
L1 inductor should be a 20 gauge air core, L2 and L4 should be 18 gauge I-core, L3 should be a 18 gauge air core.
Crossover BOM with links to suitable parts.
C1 - 3.0uF Poly
C3 - 15uF NPE
C4 - N/A
C5 - 22uF NPE
L2 - 1.5mH 18awg I-core
L3 - 1.0mH 18awg Air Core
R1 - 10 Ohm 10w
R2 - 2.7 Ohm 10w
R3 - 6 Ohm 10w
Loudspeaker Drivers / Horn:
Compression Driver - LaVoce DF10.101LS
Horn - Celestion H1SC-8050
Note: This page may contain affiliate links which if used allows me to earn a small commission if those products are purchased from that link at no additional cost to you.
All of the drivers and parts for this design were purchased by myself, nothing was provided by the affiliated retailers. Any commission earned just helps offset the cost of the build and allows me to continue to design and publish more free DIY speaker plans like this one.
Full measurements for the Flex-8 Beta-8 Variant
The following measurements were performed on my 10' tall outdoor turntable, measurements taken at ~2.83v / 2M on the tweeter axis and scaled 6dB which provides the same approximate SPL as 2.83v / 1M.
The measurements were gated at 14ms and blended to diffraction adjusted nearfield woofer response below ~300hz.
No smoothing applied to the frequency response measurements.
On Axis Response
CTA-2034 Style Spin
Estimated In-Room Response
Horizontal Off Axis Waterfall - Normalized to On Axis
Flex-8 (Beta-8) Harmonic Distortion at 85, 95, 100 and 105dB/1m
Compression at 85/95/100/105dB normalized against 75dB:
Flex-8 (Beta-8) Impedance:
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