Up for test is JL Audio’s ZR800-CW 8″ Midbass. Specs can be found here.
Small Signal Parameters
Results as measured via Dayton’s DATs measurement tool. Which is a very little handy tool to have. 😉
- f(s)= 56.52 Hz
- R(e)= 5.35 Ohms
- Z(max)= 54.75 Ohms
- Q(ms)= 11.113
- Q(es)= 1.205
- Q(ts)= 1.087
- V(as)= 14.310 liters (0.505 cubic feet)
- L(e)= 0.90 mH
- n(0)= 0.20 %
- SPL= 85.21 1W/1m
- M(ms)= 31.46 grams
- C(ms)= 0.25 mm/N
- BL= 7.05
Frequency Response and the following Harmonic Distortion measurements were taken using Dayton’s OmniMic measurement system.
The frequency response measurements below are on-axis (0 degrees) and off-axis (15, 30, 60 degrees), measured at 2.83v/1m.
The following HD graphs are done in the nearfield, emulating the following SPL levels at 1 meter: 90dB, 96dB, and 102dB in order.
Frequency Response: Average sensitivity in it’s primary range is approximately 86dB @ 2.83v/1m. On the low end, the Qts indicates a high value of 1.087 and a Vas of approximately 0.50 cubic feet, which means this driver is likely built for an infinite baffle type install. According to JL’s literature, that’s indeed the case: “The ZR800-CW is a supremely powerful, dedicated mid-bass driver designed for infinite-baffle or door-mounted custom installations.” This driver exhibits fairly linear response up until about 500hz where some issues occur. Looking at the impedance graph you can see a resonance show up in the 600-700hz region. This shows up in the FR with the strong dip just around 700hz. From 700-1200hz there’s odd behavior, and above 1200hz the response gets better.
Harmonic Distortion: I’ve provided HD measurements at (3) different SPL levels: 90, 96, and 102dB. The reason I do this is to see the general trend of how distortion increases with output. But since this is a midbass and likely will be pushed hard, I’ll evaluate the 102dB level distortion. The 3% THD mark is hit at just under 40hz. From 60-300hz, where these are most likely to be used, the distortion level is approximately 0.60%. At 500hz the THD reaches 1% and rides that range until it begins to fall at ~1200hz.
Bottom line: As a dedicated midbass in a 3-way type system (or a 2-way using a ‘wideband’ driver) this is an excellent choice. From the data, it is seen you can reach pretty hefty levels with very little distortion (less than 1% THD) crossing this driver between 50/60hz to about 300/400hz. This coincides with the FR data as well. I wouldn’t recommend crossing this higher than 500hz, though because the response gets pretty rough above this point and it would be hard to implement a crossover here. Regarding the low end output, keep in mind cabin gain comes in to play in most cars at about the 60-70hz region and increases the SPL below this point by ~12dB/octave. Which means some people may be able to run these without a dedicated subwoofer and be plenty happy … obviously this is very much user dependent, but I will say I’ve done it a few times myself and have had good success using a 50hz/LR2 crossover but I miss my subs too much to not use them. 😉
PS: If you would like to help me keep up funds for testing, there’s a little ‘contribute’ button that goes through Paypal all the way at the bottom of every page. Any little bit helps.