The Arris S34 is worth buying over the S33 only if your cable plan includes enhanced upload speeds, because the S34 supports mid-split while the S33 does not. Downloads, ports, and chipset are otherwise the same, so on a standard plan the cheaper S33 performs identically.
Last updated: September 2026
Key Takeaways
- The S33 and S34 share the same DOCSIS 3.1 downloads, the same 2.5 Gbps and 1 Gbps ports, and the same Broadcom chipset.
- The single difference is upstream. The S34 supports mid-split, which unlocks upload tiers in the hundreds of megabits where your ISP has upgraded the network. The S33 is limited to standard low-split uploads, typically 20 to 40 Mbps on most cable plans.
- The S34 is on Xfinity's Next Gen Speed Tier list. The S33 is not. If your Xfinity plan advertises fast uploads, the S34 is the only one of the two that will deliver them.
- If your plan does not include enhanced uploads, the S33 gives you the same experience for less money.
- Both run warm. Give either modem open air, and give the S34 a little more.
Arris S33 vs S34: Specs Side by Side
| Spec | Arris S33 | Arris S34 |
|---|---|---|
| DOCSIS standard | S33: 3.1 | S34: 3.1 |
| Channel bonding | S33: 32x8 plus 2x2 OFDM/OFDMA | S34: 32x8 plus 2x2 OFDM/OFDMA |
| Ethernet ports | S33: One 2.5 Gbps, one 1 Gbps | S34: One 2.5 Gbps, one 1 Gbps |
| Max download plan | S33: Up to 2.5 Gbps | S34: Up to 2.5 Gbps |
| Upstream split | S33: Low-split only | S34: Switchable low to mid-split |
| Enhanced upload tiers | S33: Not supported | S34: Supported where the ISP offers them |
| Xfinity Next Gen Speed Tier list | S33: No | S34: Yes |
| WiFi | S33: None (router required) | S34: None (router required) |
| Case | S33: Compact white, horizontal | S34: Compact white, vertical |
| Released | S33: 2020 | S34: September 2024 |
What Mid-Split Means and Why It Is the Whole Story
A cable line carries downloads and uploads on different frequency ranges. For decades, uploads were squeezed into a narrow band at the bottom of the spectrum, which is why cable upload speeds sat around 10 to 40 Mbps even on gigabit plans. That layout is called low-split.
Mid-split widens the upload band. Where an ISP has upgraded the network, a mid-split modem can upload several hundred megabits per second. Xfinity markets these plans as Next Gen Speed Tiers, and Spectrum has enabled mid-split in a growing list of markets.
The S34 has switchable upstream filters that let it operate in either mode, so it takes advantage of mid-split where it exists and falls back to low-split everywhere else. The S33 has no such filters. It is a low-split modem and will stay one no matter what plan you buy.
Everything else on the two modems is the same. Same download channels, same 2.5 Gbps port, same chipset family. You are paying the S34 premium for one feature, and it only pays off if your network and plan can use it.
ISP by ISP: Which One You Need
Xfinity
Both modems are on Xfinity's approved list. Only the S34 appears on the shorter Next Gen Speed Tier list, which is the list that matters if your plan advertises uploads of 100 Mbps or more. An S33 on one of those plans will activate fine and download at full speed, but uploads will stay at the old low-split ceiling. Check your plan's advertised upload speed in the Xfinity app: if it reads above 40 Mbps, buy the S34. Our Xfinity approved modems list has the full Next Gen table.
Spectrum
Both are approved for Spectrum plans up to 1 Gig, and Spectrum added the S33v2 and S33v3 to its list in May 2026. Spectrum has rolled out mid-split uploads market by market, so the S34 unlocks faster uploads only where that upgrade has reached your address. If Spectrum has not advertised faster uploads in your area, the S33 is the better buy. See our Spectrum approved modem list.
Cox
Cox lists both and hosts the S34 datasheet on its own support site. Cox's upload upgrades have been slower to arrive than Xfinity's, so for most Cox customers the S33 is enough today. The S34 is the safer choice if you plan to keep the modem for five years or more.
Heat and Placement
The S33 already runs warmer than older SURFboard modems because of its compact case. The S34 adds active OFDMA upstream channels, and owners consistently report it running hotter still, sometimes enough to cause dropped connections in a closed cabinet. Neither modem has a problem in open air with a few inches of clearance. Do not stack a router on top of either one, and do not seal either one in a media cabinet.
Which Should You Buy?
Choose the Arris S33 if:
- Your plan's advertised upload speed is 40 Mbps or less.
- You are on Spectrum or Cox in an area without mid-split.
- You want the lowest price on a 2.5 Gbps modem.
Choose the Arris S34 if:
- Your Xfinity plan is a Next Gen Speed Tier with uploads of 100 Mbps or more.
- Spectrum has enabled faster uploads at your address.
- You upload large files, stream to Twitch or YouTube, or back up to the cloud and want the headroom when your ISP turns it on.
If your plan is 1 Gbps or slower and you do not need a 2.5 Gbps port at all, the older Arris SB8200 costs less than either. Our S33 vs SB8200 comparison covers that decision.
Frequently Asked Questions
Is the Arris S34 faster than the S33?
For downloads, no. Both top out at the same 2.5 Gbps port and the same DOCSIS 3.1 channel layout. The S34 is faster only for uploads, and only on plans that include mid-split upload speeds.
What is the Arris S33 max upload speed?
The S33 is a low-split modem, which caps theoretical uploads around 100 Mbps and real-world uploads at whatever your ISP provisions on the low-split band, usually 20 to 40 Mbps. It cannot use Xfinity's Next Gen upload tiers.
Arris S34 vs NETGEAR CM3000: which is better?
Both support mid-split and both are on Xfinity's Next Gen list. The CM3000 also supports high-split, which no major ISP has deployed to retail modems yet, and it costs more. For most people the S34 is the practical pick. The CM3000 is worth it only if you want the longest possible runway.
Does the S34 replace the S33?
Not yet. Arris sells both. The S33 remains the mainstream 2.5 Gbps modem, and the S34 is positioned as the upload-optimized version for Next Gen plans.
Does the Arris S34 work with Spectrum?
Yes. It is approved for Spectrum plans up to 1 Gig. Its mid-split feature only engages in Spectrum markets where the upstream upgrade has been completed.
Does the S34 run hot?
Yes, more than the S33. It is stable with open air around it. Overheating reports almost always involve a closed cabinet or a router stacked directly on top.
