Throughput vs. Attenuation - 2.4 GHz
Focusing on just the AC1750 class routers, we'll take a brief look at throughput vs. attenuation plots to look at the nuances of how the products perform over their entire signal operating range.
For downlink, all three routers are fairly tightly grouped between 137 and 143 Mbps at the start of the test with 0 dB of attenuation. The DIR-868L drops below the other two starting at 12 dB and stays below the pack until about 36 dB. Starting at 21 dB, the Linksys EA6500's curve stays above and to the right (faster) than the other two until it loses connection at 60 dB.
Throughput vs. Attenuation - 2.4 GHz downlinkFor 2.4 GHz uplink, the clear winner is the ASUS RT-AC66U and clear loser the D-Link DIR-868L. The ASUS started out with higher throughput than the other two and remained above the others out to 51 dB. The D-Link started to drop off at 12 dB and its plot was below and to the left (lower throughput) of the other routers until it lost connection at 57 dB.
Throughput vs. Attenuation - 2.4 GHz uplink
Throughput vs. Attenuation - 5 GHz
Surprisingly, for 5 GHz downlink, there really wasn't a clear winner or loser. As you can see from the plots, performance started out very similar and remained that way until about 21 dB where the ASUS took a slight lead. The Linksys was the first to drop the connection at 36 dB followed by the ASUS at 39 dB. AT 33 dB, the results were still tightly grouped in the mid 40's ranging from 45 Mbps to 49 Mbps. Thereafter, throughput dropped off rapidly with the D-Link being the last one standing at 39 dB with throughput of 8 Mbps. It dropped the connection at 42 dB of attenuation.
Throughput vs. Attenuation - 5 GHz downlink
For 5 GHz uplink, there's a little more variation in results. The ASUS and the D-Link each start at 402 Mbps at 0 dB, with the Linksys a tad lower at 392 Mbps. Starting at 9 dB, the D-Link plot drops below the other two and stays there throughout the rest of the range. The ASUS and Linksys track fairly closely though the mid attenuation values, with the Linksys being the first to drop the connection at 36 dB followed by the ASUS at 39 dB. At 39 dB, the D-Link was the last one standing (again) with 9 Mbps of throughput, but dropped its connection at 42 dB of attenuation.
Throughput vs. Attenuation - 5 GHz uplink
As Tim pointed out in his AC1900 retest conclusion, "The V8 wireless test process is definitely tougher than the V7. All tests are used instead of just the best test run and the 360° rotation during test makes it much more difficult for products to maintain a connection at low signal levels". Indeed, we saw that products had difficulty with low signal conditions and dropped connections earlier—especially in the 5 GHz band.
The charts at the top of the article tell an interesting story. First, the average profiles are just that - averages, so you don't really see the highs and lows. Interestingly, in the 2.4 GHz downlink profile, for the average and maximum, an AC1750 router topped the charts. In fact, for the downlink maximum chart, all the AC1750 class routers scored higher than the AC1900 routers. Even for the uplink average and maximum charts, the AC1750 class ASUS RT-AC66U placed second behind an AC1900 router and ahead of the other three AC1900 class routers.
The key take-away from this analysis is that higher link rate doesn't necessarily mean higher performance, at least not in the way you might think. AC1900 routers have a higher link rate than AC1750 routers only in 2 4 GHz (600 Mbps vs. 450 Mbps). The 5 GHz link rate is the same for both classes. Yet, in our comparison, we found generally improved 5 GHz performance from the AC1900 routers, and in many cases better 2.4 GHz performance from the AC1750 class products.
In the end, it all comes down to which band you're looking for better performance in. It also pays to shop carefully – the D-Link AC1900 (DIR-880L) is actually $5.00 cheaper than the AC1750 ASUS RT-AC66U. And the bargain is the Linksys EA6500, which Linksys told us they're discontinuing because people buy more AC1900 routers! You can buy a refurb EA6500-RM directly from Linksys for $95 with free shipping and 30-day money back guarantee.