For most trucks, buy the Midland 21-406: a 20-watt, 8-ohm metal speaker with a 6.5-foot cord that fits any CB with a 3.5 mm external speaker jack. If your cab is loud, the Cobra HG S300 adds a noise filter. On a budget, the plain rectangular 5-watt speaker that sold 400 last month on Amazon does the basic job. For a doorless Jeep or a GMRS MicroMobile, get the IP67 Midland SPKMINI.
Whatever you choose, check two numbers before you order: the radio wants an 8-ohm speaker, and it goes in the jack marked EXT SP, not PA.
Quick picks
| Best overall | Midland 21-406 | Amazon |
|---|---|---|
| Best for loud cabs | Cobra HG S300 | Amazon |
| Best with talk-back | Cobra HG S500 | Amazon |
| Best budget | Rectangular 5 W communications speaker | Amazon |
| Best for open Jeeps and GMRS mobiles | Midland SPKMINI | Amazon |
| Most-reviewed compact | RoadPro RPSP-15 | Amazon |
| Cheapest noise filter | Astatic 302-VS6 | Amazon |
| Best PA speaker | Workman 5-inch PA horn | Amazon |
How we picked
We pulled Amazon's results for "cb radio external speaker," "cb radio speaker" and "cb pa speaker" on Oct 21, 2026, then the full listing for each contender. The generic rectangular 5-watt speaker led on sales at 400 bought last month with 1,879 ratings; the Midland 21-406 and the SPKMINI each showed 200+, and the RoadPro RPSP-15 had the deepest rating history at 2,835.
Then we read the radio side. Cobra's owner's manual for the 29 LTD Classic AM/FM and Midland's MXT500 manual both state what the external speaker jack expects, so every pick had to list 8 ohms (or come from a maker whose CB line uses 8-ohm jacks) and a 3.5 mm plug. Speakers whose listings contradict that were moved to the cautions below instead of getting a card.
"How we pick" means listings, manuals and the FCC rules, not a bench test. How we research.
The fit check: three jacks, one right answer
Most full-size CBs have three connections on the back besides power: the antenna, a PA speaker jack and an external speaker jack. The two speaker jacks look alike and take the same 3.5 mm plug. They do different jobs.
Cobra's manual for the 29 LTD Classic AM/FM spells it out. The external speaker "should have 8-ohm impedance and be rated to handle at least 4.0 watts," and plugging one in disconnects the internal speaker. The PA jack wants the same 8 ohms and 4 watts, and the radio sends 4 watts into it with the CB/PA switch on PA. Midland's MXT500 manual gives the same rating for its external speaker jack: 8 ohms, 4 watts minimum.
| Check | What to look for | Why it matters |
|---|---|---|
| Impedance | 8 ohms, matching the radio manual | A lower number loads the radio's audio amp harder than its spec |
| Power rating | At least 4 W for a full-size CB | A speaker rated above the radio's output is fine; one rated below can distort |
| Plug | 3.5 mm (1/8 inch) mono | The standard on CB and GMRS mobiles; adapters add a loose joint |
| Jack on the radio | EXT SP for listening, PA for a horn | The most common reason a new speaker "doesn't work" |
| Cord length | Radio to mounting spot, plus slack for routing | A semi's overhead console needs far more than a dash mount |
The FCC side is simple. Part 95 lists "headphone and speaker output connections and related selector switch" among the connections a CB may have (47 CFR 95.987(d)), and a receive speaker changes nothing about what you transmit. No speaker adds range; the antenna does that.
The 8 best CB radio external speakers
Midland 21-406
Midland lists this one for CB radios and GMRS mobiles, its own MXT line included, and that's the case for it: one speaker that will move to whatever radio you own next. The metal box and swivel base hold up to washboard roads, the 6.5-foot cord reaches across a full-size cab, and 20 watts of handling is far more than any CB will send it. With 994 ratings and 200+ bought last month, it's also the most-owned name-brand speaker in our search.
- Power20 W
- Impedance8 ohms
- Driver3.25 in
- Enclosuremetal
- Cord6.5 ft
- Mountswivel base
Why it stands out
- Rated 8 ohms, 20 W
- Metal enclosure, swivel base
- Works across CB and GMRS mobiles
Think twice if
- You need it sealed against rain or dust; the listing says it isn't water resistant
Cobra HG S300
Cobra's noise filter is the reason to pay a little more. It's aimed at the hiss and harsh top end that make a long shift on AM tiring, and the 4-inch driver with a 5.5-ounce magnet is bigger than the 2-inch-class speakers inside most radios. Two practical touches: the ratcheted bracket holds its angle on a bumpy road, and a headphone jack on the speaker lets a team driver keep listening while the sleeper stays quiet.
- Power15 W
- Driver4 in, 5.5 oz magnet
- Filternoise canceling
- Bracketratcheted, 180 degrees
- Extra3.5 mm headphone jack on the speaker
Why it stands out
- Noise filter for engine and road noise
- Headphone jack on the speaker
- Ratcheting 180-degree bracket
Think twice if
- You want talk-back too; that's the S500
Cobra HG S500
The S500 is the S300 plus variable talk-back, which lets you hear your own voice through the speaker as you transmit. That matters when you're setting up a new mic or a power mic and want to hear what everyone else hears without asking for a radio check every minute. It has 794 ratings. The listing doesn't explain how the talk-back lead connects, so read Cobra's instructions for your radio model before you start cutting into the install.
- Power15 W
- Impedance8 ohms
- Driver4 in, 5.5 oz magnet
- Filternoise canceling
- Talk-backvariable
Why it stands out
- Talk-back for setting mic gain
- Same filter and driver as the S300
Think twice if
- Your mic is already dialed in; the S300 does the listening part for less
Rectangular 5 W communications speaker
This is the plain rectangular speaker you've seen bolted under a thousand dashboards, and it sells: 400 bought last month, 1,879 ratings. The listing confirms 8 ohms and a standard 3.5 mm plug, with a bracket and screws in the box. Five watts covers what a 4-watt CB sends it. For a work truck, a spare or a scanner on the shop bench, there's no reason to spend more.
- Power5 W
- Impedance8 ohms
- Sizeabout 4.5 x 2.5 x 2.25 in
- Plug3.5 mm
- Includedbracket and hardware
Why it stands out
- 8 ohms, 3.5 mm plug, bracket included
- Small enough for tight dashes
Think twice if
- You want a noise filter or a metal swivel mount
Midland SPKMINI
An IP67 rating means the speaker is sealed against dust and water, which is the spec that counts in a Wrangler with the doors off or a side-by-side. Midland lists it for CBs and GMRS mobiles, MXT MicroMobiles included, all through the standard 3.5 mm plug. It's compact, so it fits on a roll bar or grab handle where a 5-inch box won't. Midland backs it for three years.
- Power10 W
- Impedance8 ohms
- SealingIP67
- Plug3.5 mm
- Bracket180-degree
- Warranty3 years
Why it stands out
- IP67 sealed
- Small footprint for roll bars
- Three-year warranty
Think twice if
- Your truck has a roof and doors; the 21-406 gives you more speaker for the money
RoadPro RPSP-15
A truck-stop staple with 2,835 ratings, the most of any speaker we found. Eight feet of cord, a swivel bracket and a metal mesh grille in a 2.75 by 4.5-inch box. RoadPro labels it "for use with CB radios only," which tells you it was built around CB audio rather than music.
- Power5 W
- Impedance8 ohms
- Size2.75 x 4.5 in
- Cord8 ft
- Plug3.5 mm
- Grillemetal mesh
Why it stands out
- Huge owner base
- 8-foot cord and swivel bracket
Think twice if
- You also want it for a ham or scanner rig; RoadPro only lists CB
Astatic 302-VS6
The budget way to get a noise-canceling speaker, from the company best known for CB mics. The 10-foot cord is the longest among our picks, which helps when the radio lives under a seat or in an overhead console and you want the speaker near the windshield. It has 486 ratings.
- Power10 W
- Impedance8 ohms
- Filternoise canceling
- Cord10 ft
- Plug3.5 mm
- Includedbracket and hardware
Why it stands out
- Noise canceling at a low price
- 10-foot cord
Think twice if
- You want a metal enclosure; the listing says plastic
Workman 5-inch PA horn
This is the other kind of CB speaker: a weatherproof horn that mounts under the hood or on the grille guard and plugs into the PA jack. With the CB/PA switch on PA, your mic talks through it, which is handy at a trailhead, a work site or a parade. It's 8 ohms and 12 watts, which suits the 8-ohm, 4-watt PA output in Cobra's manual. It has 1,045 ratings. Point it away from the cab so the mic doesn't feed back, as Cobra's manual warns.
- TypePA horn
- Impedance8 ohms
- Power12 W
- Plug3.5 mm
- Buildweatherproof plastic
Why it stands out
- Weatherproof for outside mounting
- 8 ohms, 3.5 mm plug
Think twice if
- You want better cab audio; a horn in the EXT jack sounds harsh
Comparison table
| Speaker | Watts | Ohms | Cord | Filter or extra | Weather |
|---|---|---|---|---|---|
| Midland 21-406 | 20 | 8 | 6.5 ft | Swivel base | Not sealed |
| Cobra HG S300 | 15 | Check listing | Check listing | Noise filter, headphone jack | Not sealed |
| Cobra HG S500 | 15 | 8 | Check listing | Noise filter, talk-back | Not sealed |
| Rectangular 5 W | 5 | 8 | Check listing | Bracket | Not sealed |
| Midland SPKMINI | 10 | 8 | Check listing | 180-degree bracket | IP67 |
| RoadPro RPSP-15 | 5 | 8 | 8 ft | Swivel bracket | Not sealed |
| Astatic 302-VS6 | 10 | 8 | 10 ft | Noise filter | Not sealed |
| Workman PA horn | 12 | 8 | Check listing | PA use only | Weatherproof |
Pick by rig
| Your setup | Start with | Mount it |
|---|---|---|
| Pickup on the highway, radio under the dash | Midland 21-406 | Dash top or A-pillar, cone toward your ear |
| Semi with an overhead radio | Cobra HG S300 or Astatic 302-VS6 | Headliner or overhead console; long cord helps |
| Doorless Jeep or side-by-side | Midland SPKMINI | Roll bar or grab handle, near head height |
| GMRS mobile with an EXT SP jack (Midland MXT500 and others) | Midland 21-406 or SPKMINI | Same as CB: 8 ohms, 3.5 mm |
| Home base on a desk | Rectangular 5 W or RoadPro RPSP-15 | On the desk, away from the mic |
| Talking to a crowd outside | Workman PA horn | Outside, facing away from the cab |
Members of the JK-Forum who added speakers to Jeep CBs mostly mounted them on the sound bar, roll bar or just under the dash, and every one who answered said it was worth doing. One of them added a caution worth repeating: a weak antenna or ground can also make audio sound low, and no speaker fixes that.
Speakers to double-check
- The Uniden BC20 sells well (1,143 ratings), and its bullets say it's non-powered with a 10-foot cord. But the spec table on the same listing gives the impedance as 4 ohms, while the CB manuals we read ask for 8. Confirm the rating with Uniden before you pair it with a radio that calls for 8 ohms.
- The Midland SPK200 is an amplified, IP67, 20-watt speaker with a 12-volt input. It needs a power feed as well as the audio plug, so it's a bigger install than the passive speakers here.
- Icom's SP-35 5-watt speaker is listed for Icom commercial mobiles. It uses a 3.5 mm jack, but the listing doesn't give an impedance, so check Icom's spec before using it on a CB.
Installing it in 15 minutes
- Hold the speaker where you plan to mount it and drive around the block with the radio on. Head height and pointed at your ear beats a bigger speaker aimed at your knees.
- Stay out of airbag deployment zones (your vehicle owner's manual marks them) and keep the cord away from pedals and hot vents.
- Plug into EXT SP. The radio's own speaker should go quiet, which is how you know you picked the right jack.
- Turn the volume back up. Then set squelch and RF gain with the engine running, since that's when the noise is real. How to adjust a CB radio walks through each knob in order.
- If a PA horn is going on too, mount it outside and away from the cab. Feedback is the horn hearing your mic.
Handheld CBs are a different story: most take a speaker mic, not a separate dash speaker, and that's covered in our handheld CB radio guide. Still choosing the radio itself? Start with the best CB radios for trucks, and if people say your voice is muddy rather than the speaker, a better CB microphone is the fix.
Using these speakers on a GMRS mobile
The same speakers work on GMRS mobiles that have an external speaker jack, because the jack is the same 8-ohm, 3.5 mm design. Midland's MXT500 manual lists its external speaker jack as 8 ohms, 4 watts minimum. Not every MicroMobile has one: our MXT275 vs MXT575 comparison lists a speaker jack on the MXT575 and a speaker-mic jack on the MXT275. For speaker placement in a Wrangler, the Jeep Wrangler GMRS install guide shows where the radio and wiring usually go, and best GMRS radio for a Jeep covers which radios have the jack.
If you buy one speaker
Get the Midland 21-406, plug it into EXT SP and mount it where your ear is. In an open Jeep, swap that for the Midland SPKMINI. If the channel still sounds rough after that, the problem is upstream: check the antenna with our truck CB antenna guide before you buy anything else.
Sources: Amazon listings and search results (checked Oct 21, 2026); Cobra 29 LTD Classic AM/FM owner's manual (speaker, PA and spec sections); Midland MXT500 owner's manual on support.midlandusa.com (external speaker jack); JK-Forum thread "external speaker cb"; 47 CFR 95.987(d) (eCFR up to date as of Oct 19, 2026). How we research · Affiliate disclosure