Up for test is SB Acoustics’ SB23NACS45-8, 8″ Woofer.
After looking at Revel’s new(ish) Performa3 Lineup, I realized that they are, at least in part, using SB acoustics drivers. The Revel F208 uses (2) 8 inch woofers, which bear a striking resemblance to the SB’s under review here.Though, most certainly tweaked to fit their needs. 6moons.com did a review on the Revel F206 which contains pictures of the SB labeled drivers, pulled from their cabinets. In these pictures you can see the driver model number, containing the same naming scheme SB has for their drivers. For example: 6moons’ picture of the tweeter in the f206 (here) carries the model number “SB26ADC-C000-4-RVL”. You’ll notice SB’s site has a tweeter model #SB26ADC-C000-4.
Further, if you view the pictures of the raw woofer drivers, you’ll notice a lot of similarities such as the inverse-ribbed cone, and basket design. While it seems apparent Revel used SB as an ally in the production of this speaker, odds are high Revel didn’t just use these SB drivers ‘off the shelf’. One obvious difference is the black cone used in the Revel lineup rather than the aluminum colored cone presented here. That said, the connection me curious about the ‘raw’ driver performance. I went to SB’s site and located the 8″ driver. I contacted Madisound to inquire about the product and was informed it wasn’t on their site just yet as they had recently taken shipment of them. So, I placed an order for a set and got some testing done recently.
First, some photos:
Testing the small signal parameters:
I tested both drivers back to back to compare their consistency. Below are the values obtained for each.
|Sample 1||Sample 2||Units||Description|
|Re||5.47||5.48||Ohm||electrical voice coil resistance at DC|
|Le||0.364||0.358||mH||frequency independent part of voice coil inductance|
|L2||0.401||0.379||mH||para-inductance of voice coil|
|R2||2.18||2.17||Ohm||electrical resistance due to eddy current losses|
|Cmes||455||465||µF||electrical capacitance representing moving mass|
|Lces||61.9||64.17||mH||electrical inductance representing driver compliance|
|Res||50.6||48.9||Ohm||resistance due to mechanical losses|
|fs||30||29.1||Hz||driver resonance frequency|
|Mms||30.81||31.177||g||mechanical mass of driver diaphragm assembly including air load and voice coil|
|Mmd (Sd)||27.223||27.589||g||mechanical mass of voice coil and diaphragm without air load|
|Rms||1.338||1.371||kg/s||mechanical resistance of total-driver losses|
|Cms||0.914||0.957||mm/N||mechanical compliance of driver suspension|
|Kms||1.09||1.05||N/mm||mechanical stiffness of driver suspension|
|Bl||8.23||8.189||N/A||force factor (Bl product)|
|Qtp||0.423||0.42||total Q-factor considering all losses|
|Qms||4.338||4.162||mechanical Q-factor of driver in free air considering Rms only|
|Qes||0.469||0.466||electrical Q-factor of driver in free air considering Re only|
|Qts||0.423||0.419||total Q-factor considering Re and Rms only|
|Vas||60.3473||63.1788||l||equivalent air volume of suspension|
|n0||0.334||0.322||%||reference efficiency (2 pi-radiation using Re)|
|Lm||87.44||87.28||dB||characteristic sound pressure level (SPL at 1m for 1W @ Re)|
|Lnom||89.09||88.93||dB||nominal sensitivity (SPL at 1m for 1W @ Zn)|
Overall, the comparison between the two units is pretty much on par.
Large Signal LSI Klippel Testing:
I didn’t have the time to test both samples so the following is all “Sample 1” driver.
|Displacement Limits||thresholds can be changed in Processing property page|
|X Bl @ Bl min=82%||5.6||mm||Displacement limit due to force factor variation|
|X C @ C min=75%||3.7||mm||Displacement limit due to compliance variation|
|X L @ Z max=10 %||>6.2||mm||Displacement limit due to inductance variation|
|X d @ d2=10%||38||mm||Displacement limit due to IM distortion (Doppler)|
|Asymmetry (IEC 62458)|
|Ak||25.39||%||Stiffness asymmetry Ak(Xpeak)|
|Xsym||-0.61||mm||Symmetry point of Bl(x) at maximal excursion|