Flex-8 - Silver Flute W20RC38-04
I think this 8" Silver Flute is the best looking woofer of the bunch. It has which I consider a very attractive cone and nice cast aluminum frame and pairs that with one of the smoothest frequency responses from the woofers as well. Sound quality is decent, nothing offensive from the woofer itself and it give a nice neutral perhaps slightly warm sound. The price of the woofer is not bad considering what you get. Bass response is better then the GRS but less then the Dayton models, not too bad by playing by itself but subs are still recommended for full experience.
The internals of the woofer are fairly basic so distortion performance is basic as well. This woofer actually produces quite a large amount of 2nd order harmonic distortion in the low midrange and bass at higher levels. Being 2nd order and at lower frequencies it's largely unoffensive but it is the woofer's primary weakness. I would have liked to see some under spider venting, which may cut that distortion down a bit. Otherwise it appears to start running out of linear travel above the 100dB level which can been seen in the compression graph as there is a large drop between the 100dB and 105dB sweeps centered around 150Hz. This can be heard in music as strong bass notes and drums start to fall flat when the speaker is pushed hard.
Sensitivity is fairly good at ~88.5dB/2.83v (4pi) the highest of the bunch but this is a 4 ohm design so subtract 3dB for the nominal 1w/1m rating at 85.5dB which is more modest.
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 negatives are the slightly narrower coverage of the horn then I would have liked and the early drop in high frequency output past 16kHz. For the cost I don't mind as they are not glaring issues that you notice immediately and the narrow dispersion could actually be a benefit depending on the desired use of the speakers if wanting a more focused dispersion pattern to keep excessive energy off the walls.
Overall decent, with a nice sound. Due the the highest sensitivity it's probably the best variant to be paired with a lower wattage amp assuming the amp is 4 ohm stable. Otherwise best if not pushed too hard, as the woofers starts to tap out around the 100w level in the bass range. A 150-200w amp would be the most I would use for the design this gives a little more dynamic range in the midrange and treble but know your bass peaks will start to get squashed and compress as well.
Crossover Schematic:
Port Tube:
Should be trimmed between 4-6" long. As tested it was cut at 6" long but a slightly shorter length would provide a flatter bass response before rolloff at the expense of some extension.
On this crossover the C1 cap on the highpass and C2/C3 caps on the lowpass were designed to be polypropylene but C5 can be non-polarized electrolytic, no benefit to poly there.
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
C2 - 30uF Poly
C3 - 30uF Poly
C4 - N/A
L2 - 1.25mH 18awg I-core (a 1.2mH value can also be used)
R1 - 10 Ohm 10w
R2 - 1.8 Ohm 10w*
*If 1.8 Ohm is not available a 2 Ohm can be used instead which results in a bit (~0.7dB) more output from the high frequency driver or combine the 2 ohm with a small 15-22 Ohm resistor in parallel.
R3 - 6 Ohm 10w
Loudspeaker Drivers / Horn:
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Full measurements for the Flex-8 Silver Flute Variant
The following measurements were performed on my 10' tall outdoor turntable, measurements taken at ~5.66v / 2M on the tweeter axis which provides the same approximate SPL as 2.83v / 1M. (Since this is a 4 ohm design subtract 3dB for the nominal 1w/1m efficiency)
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
Flex-8 (GRS) Harmonic Distortion at 85, 95, 100 and 105dB/1m
Compression at 85/95/100/105dB normalized against 75dB:
Flex-8 (Silver Flute) Impedance:
