VBS-10.2
Value Buster Series 10" Two Way
Design description and goals:
Bigger Brother to the VBS-6.2 this is another design that delivers a very high level of bang for your buck. A 10" 2-way with a horn loaded compression driver that does not sacrifice sound quality in its ability to deliver high output for very reasonable costs. Ideally suited for home theater use as mains and surrounds or for high output stereo use when paired with subwoofers and subwoofers are required as the lack of bass will result in a lean sound without them.
Drivers, horn & crossover costs come in just under $160 per speaker at the time of writing this page up which is a nearly unbeatable value considering the quality of the overall design.
The VBS-10.2 is just a straightforward clean and dynamic design for which I tried to voice it in a way that imparts minimal coloration to the sound, you hear what was intended not the speaker itself. Even when pushed to very high output levels that would cause conventional speakers designs struggle with the VBS-10.2 remains both transparent and dynamic.
For in home theater/stereo systems amplifier power levels in the 200-400w @ 8 ohms could be used if looking to get the most out of the speakers but these are not very power hungry so lower power amps are perfectly acceptable as well. Even a few dozen watts will still provide a decently dynamic experience pushing well over 100dB.
Driver selection:
Woofer: The GRS 6PT-8 woofer really surprised me in the VBS-6.2 so I wanted to test out the larger GRS10PT-8 which again looked like a great value. It models well in a compact sealed enclosure, looking to easily reach the standard 80hz subwoofer crossover frequency which was my target. The published frequency response looked decent outside of a dip around 850hz but for a budget design I wasn't too worried about for the most part it is a non issue. (more details lower on this page). The driver also had plenty of xmax for a pro 10" (7.8mm listed in the spec sheet) which helps greatly in a sealed design like I was planning. Overall for the cost the I think the 10PT-8 is an unbeatable value and you would have to spend much more to find a similar woofer with better performance.
Horn: For the horn/waveguide I choose the Eminence WG-10, it's no longer available from Parts Express but can be found directly from Eminence as well as a few other retailers. The shape of the WG-10 looked very promising, large round overs at the mouth, smooth transitions from between the vertical and horizontal sides of the horn and a constant directivity design which accepts bolt on compression drivers (opens up driver options). The rated dispersion looked a little narrow on paper but I figured that would match the VBS-6.2 and I was pleasantly surprised when the dispersion from both horns ended up measuring a little wider then rated. Directivity behavior while not 100% perfect is better then most the off the shelf horns that are available, especially in the 1" bolt on format.
Compression Driver: Originally I chose the Peerless/Tymphany DFM-2535R00-08 for this design, it was a very smooth measuring compression driver with a nice low frequency roll-off, handled low crossover points well without distortion and was an excellent value as well. Of course in the months between ordering the driver and finishing the design Parts Express had stopped selling the driver and it appears this was because Tymphany/Peerless is exiting the DIY market focusing solely on OEM sales. Sadly this also killed my Slipstream design shortly after completion which used a fairly unique low profile woofer from Peerless.
The original VBS-10.2 design info using the Peerless driver can be found here.
June 2023 Update: I finally got around to finding another compression driver that I feel is equally suitable for this design, the LaVoce DF10.101L. I had the idea to try this driver as its screw on twin worked so well in the Flex-8 designs I had recently worked on. Mounted to the WG10 the DF10 did require some more crossover work then used in the Flex-8 but overall it actually requires one less part and provides a slightly smoother response in the treble range while costing less then the original Peerless did making the design an even more insane value. The only downside is a little less high frequency extension from the DF10, however I find this to be very minor considering the intended use. The DF10 even handles the relatively low 1400Hz crossover point without giving any signs of increased distortion or compression, which is amazing for the 1" voice coil! That makes the low frequency better then many of the drivers with 1.4" voice coils I've tested and even a few at the 1.75" size.
Enclosure Design:
Similar to the VBS-6.2 I wanted to use a fairly compact sealed enclosure though the GRS 10PT-8 woofer is also well suited for use in slightly larger ported enclosures. which could easily be an option if more extensions and output below 80Hz is desired.
I used polyfil damping in this enclosure, the loose pile of poly was about twice the size of the enclosure before stuffing it all in there. A light fill with fiberglass, rockwool or recycled denim would also be adequate.
I did flush mount both the woofer and the horn and placed a large 5/8" roundover on the cabinet corners. Surface mounting both should not introduce too many issues, same goes for the roundovers if you intend to build the cabinet without them.
Cabinet Cut List:
The dimensions for the cabinet I ended up with are 20.5" tall x 13" wide x 10" deep using 3/4" material. This is just over 1cuft gross, probably a tad under 1cuft after subtracting for the drivers and bracing.
Baffle/Back - 20.5" x 13"
Sides - 20.5" x 8.5"
Top/bottom - 11.5" x 8.5"
Braces - (2x) 8.5" x 1.25" & 11.5" x 1.5"
SVG profile for the Eminence WG-10 waveguide.
Includes both inner cutout and outer dimension.
Crossover Design:
I wanted to crossover where the woofer and horn directivity would match up, so I was aiming for something in the 1200-1600hz range not yet knowing how the drivers would behave and where the passive crossover would want to fall in place with the right mix of slopes for the correct time aliment and frequency response. It ended up working out right in the middle at 1400hz which did provide a near seamless transition between the woofer and horn.
The low pass is 4th order with an LCR notch filter. Highpass is 3rd order on paper but due to the other filters I used to straighten out the response the electrical slope ends up near 4th order as well. Much of the high frequency padding is done in the reactive components of the highpass so very little power is wasted as heat in the resistors padding down the compression driver to match the woofer. This is why the impedance is 12+ ohms over much of the high frequency range though it drops back down at the top end where the sensitivity from the horn/compression driver is the lowest.
Since the horn dispersion causes a slight dip directly on axis between 9-15k which fills in just a little off axis along with being ever so slightly hot in the 3-6kHz range I did not want to make on axis response perfectly flat as it would shift the power response/ listening window in a negative manner. I find striking a balance between on axis and the power response to give the best results. With that in mind the overall flattest frequency response is achieved if you toe the speakers either in or out about 10-15 degrees. Though overall voicing is certainly not bad listening directly on axis.
Suitable Crossover Parts:
C1 (22uF) - C3 (17uF) - C4 (6.8uF) - C5 (3uF) - C6 (10uF) - C7 (12uF)
L1 (3.0mH) - L2 (2.5mH) - L3 (6.0mH) - L4 (1.5mH) - L6 (0.15mH)
R1 (15/16 Ohm) - R2 (2 Ohm) - R3 (10 Ohm) - R4 (5 / 5.1 Ohm) - R5 (12.5 Ohm)
Drivers:
Woofer (GRS 10PT-8) - Compression Driver (LaVoce DF10.101L) - Horn (Eminence WG-10) (US Speaker Still has Stock)
Note: This page contains affiliate links which if used allows me to earn a small commission if those products are purchased at no additional cost to you.
All of the drivers and parts for this design were purchased by myself, nothing was sponsored or 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.
Crossover sim with individual driver response, sum and inverted response
The Capacitors of the 3uf, 10uF & 12uF values should be Polypropylene, while the 22uF, 17uF & 6.8UF were designed to be Non-Polarized Electrolytic. Those latter three can be made poly but expect a slight increase in midrange output with the change.
For the inductors the 3.0mH, 2.5mH and 6.0mH were designed using 18 Gauge I-core, Air cores can be used for the 3.0mH and 2.5mH if DCR is kept low (16 gauge or larger). The 6.0mH could be an air core of smaller gauge wire but reduce the value of R1 to keep the total circuit resistance on that leg equal.
Resistors should be 10w, standard wirewound are suitable.
The R5 resistor can be changed from 12.5 Ohm to 15 Ohm if you wanted a slightly more subdued high frequency response (-1dB) or 20 ohms if you want it noticeably more laid back (-3dB).
Update December 2023:
I created an optional In-Wall or Baffle-Wall variant of the crossover for the VBS-10.2. This version of the crossover removes the baffle step compensation from the design resulting in a more even frequency response and greater efficiency when using the cabinet/baffle mounted flush in a wall. This crossover design may also be used when installing these in large columns.
The following are the updated component values used in this crossover, the remaining components are unchanged from the standard crossover. This variant is also compatible with the optional crossover PCB.
GRS 10PT-8 Woofer Surround Resonance:
In the second round of testing to develop the crossover for the LaVoce compression driver the additional measurements made clear there is some temperature dependent surround resonance occurring with the woofer.
When I first did the detailed measurements with the peerless driver back in November 2021 the ambient temp was around 60 degrees F and the dip/resonance was not seen. In this second round of testing it was a warm June day and the temp was in the mid 80's. At this temperature the dip was much larger which can be seen on the included measurement.
I ended up waiting until the evening when temps had fallen to the low 70's closer to standard room temps to do the final measurements. At this temp the dip had shrunk but not completely disappeared.
I surmise that at higher temps the surround softens up allowing the resonance to occur, the surround motion moving out of phase with the cone at that specific frequency. While at the cooler temps it stiffens up and the effect is less pronounced or if cool enough doesn't occur at all.
At normal room temps I feel the resonance/dip becomes small and narrow enough that it does not hurt the overall sound quality and is basically imperceptible in listening.
Surround resonance response dip seen at an ambient temperature of the mid 80's.
Note: This measurement was not the final version of the crossover. 14ms gate, no smoothing, not blended to the near field LF measurement.
VBS-10.2 Design Measurements
Measurements taken 4pi at 2.83v/2m and scaled up 6dB to approximate 2.83v/1m (Nominal 1 watt / 1 meter)
Measurements gated at 14ms and blended to diffraction adjusted nearfield woofer response below 300hz.
No Smoothing Applied.
On Axis SPL & 10 Degrees Off Axis showing how the high frequency response flattens out as you move slightly off axis.
CTA-2034 Style Spin
Estimated In-Room Response
Horizontal Off Axis Waterfall - Normalized
Harmonic Distortion @ 85, 95, 100 & 105dB/1m - (Measured at 50cm)
Overall very decent staying below 1% at the highest 105dB sweep level except the in the bass which is where we are less sensitive to it, using subs and a high-pass at 80Hz will reduce that further.
The distortion performance from the 10" GRS is not quite as exceptional in the midrange as the 6" used in the VBS-6.2 but it is still very good. Great performance from the Lavoce DF10 compression driver as well, it's largely dominated by benign 2nd order harmonic with very low 3rd order below 0.1% at the 105dB sweep and the higher orders are basically non existent.
Compression at 85/95/100/105dB normalized against 75dB:
