18SOUND 8M400F
18SOUND (Eighteen Sound) 8M400F — 8" / 8 inch · Midrange without Bass (Mid) · Midrange · Ferrite
2" voice coil · 8 Ω
Part no.: 42A-CHS-MT-18S-0008
Documents
18SOUND 8M400F — 8" · Midrange Driver
250 W AES · 100.5 dB Sensitivity · Frequency range 200 Hz – 9000 Hz
Technical data
- Diameter: 8 "
- Voice coil: 2 "
- Power handling: 250 W AES
- Sensitivity: 100.5 dB
- Impedance: 8 Ω
- Magnet: Ferrite
- Weight: 4.9 kg
- Mounting depth: 106 mm
- Frequency range: 200 – 9000 Hz
Datasheet (PDF) · Manufacturer page
Series: M · Part no.: 42A-CHS-MT-18S-0008
18Sound 8M400F: 8" midrange with ferrite magnet and 100.5 dB for horn and top cabinet
A pure midrange with no compromise at the low end: the 8M400F from 18Sound's M series is an 8" driver that wants nothing but the range from 200 Hz to 9,000 Hz. Its ferrite magnet drives a 2" voice coil with BL 13.1 Tm, and because the moving mass of 16.9 g is very low for an 8" driver, it reaches 100.5 dB sensitivity. That figure defines it within the category: as a direct radiator it plays almost as loud as some horn-loaded midranges.
The Thiele-Small parameters match. Qts 0.26 and an EBP of 318 are unambiguous: this is a driver for small chambers, horns or open baffles, not for low-end extension. Fs sits at 89 Hz, Vas at 13.7 l, Xmax at 3 mm. With 250 W AES at 8 Ω and 4.9 kg weight, it is the classic ferrite option for installations where weight does not matter but efficiency does.
Use and enclosure
In a 3-way top or a large system with subwoofers, the 8M400F covers the mids between woofer and compression driver. As a midrange it belongs in a sealed chamber: the guideline is 2.1 l with an in-box resonance around 242 Hz. The calculated vented volume of 4.3 l tuned to 126 Hz gives a lower limit of 153 Hz, so it adds little over the sealed chamber but costs cone control. Our enclosure calculator handles the exact alignment.
Do not cross just above 200 Hz but with some margin above it, so the 3 mm Xmax never becomes the limit. Going up, the range reaches 9,000 Hz, so a 1" compression driver on a horn can take over where it already works comfortably. For use in front of a midrange horn, the low Qts is an advantage; matching 18Sound horns are in the manufacturer's category.
What to look out for
- 8 Ω, Re 5.1 Ω, Le 0.7 mH: allow for the impedance rise at high frequencies in the crossover.
- Ferrite magnet, 4.9 kg: heavier than neodymium, but robust under sustained high load.
- Mounting depth 106 mm, Xmax 3 mm: no lower midrange, no deep bass.
- 100.5 dB: plan the level matching to woofer and tweeter in the crossover.
- Datasheet PDF and driver database at 42.audio.
Frequently asked questions
Can the 8M400F work as a mid-woofer in a 2-way top?
No, it is not built for that. The usable range starts at 200 Hz, Xmax is 3 mm and the EBP of 318 clearly argues against bass duty. A 2-way top needs a driver with lower midrange capability, for example from the NTLW or NMB series.
Which amplifier suits the 8M400F?
Power handling is 250 W AES at 8 Ω. Thanks to 100.5 dB sensitivity you need considerably less power for high levels than with typical midranges. The practical limit is excursion at too low a crossover rather than amplifier power.
What is the difference between the 8M400F and the 8NTLW2000?
The 8NTLW2000, with Fs 74 Hz, Qts 0.26 and Vas 11.3 l, is tuned lower and designed for lower midrange. The 8M400F at Fs 89 Hz is the pure midrange with higher efficiency and a ferrite magnet. If you only need mids, take the 8M400F.
18Sound 8M400F: manufacturer, spellings and classification
18Sound, 18 Sound and Eighteensound all refer to the same manufacturer: Eighteen Sound S.r.l. of Reggio Emilia, Italy. The 8M400F is a 8-inch midrange driver with ferrite magnet from the M series, available from 42.audio, 18Sound dealer in Germany, with datasheet and full specifications in the driver database.
At 42.audio you get the 18SOUND 8M400F with datasheet PDF, all key data in the driver database and the enclosure calculator. More drivers from this manufacturer: Atlas 18Sound.
Thiele-Small parameters
| Nominal impedance | 8 Ω |
|---|---|
| Resonance frequency fs | 89 Hz |
| Total Q Qts | 0.26 |
| Electrical Q Qes | 0.28 |
| Mechanical Q Qms | 4.03 |
| Equivalent volume Vas | 13.7 l |
| Moving mass Mms | 16.9 g |
| Cone area Sd | 227 cm² |
| Linear excursion Xmax | 3 mm |
| Force factor BL | 13.1 Tm |
| DC resistance Re | 5.1 Ω |
| Voice coil inductance Le | 0.7 mH |
Comparable drivers
Same size, same type, Qts within ±30 %.
- 18 Sound 8NTLW2000fs 74 Hz · Qts 0.26 · Vas 11.3 l · in the database
- B&C Speakers 8NDL64fs 80 Hz · Qts 0.25 · Vas 9.6 l · in the database
- B&C Speakers 8NW51fs 76 Hz · Qts 0.25 · Vas 10.6 l · in the database
- RCF MB8N251fs 68 Hz · Qts 0.25 · Vas 13 l · in the database
- B&C Speakers 8MDN51fs 68 Hz · Qts 0.27 · Vas 17.5 l · in the database
- Oberton 8NM250_V2fs 67.7 Hz · Qts 0.25 · Vas 8.39 l · in the database
Specifications
| Allgemein | |
|---|---|
| Manufacturer | 18SOUND |
| Category | Mid Frequency |
| Series | M |
| Magnet | Ferrite |
| Impedance (Ω) | 8 |
| Power handling (W) | 250 |
| Sensitivity (dB) | 100.5 |
| Frequency from (Hz) | 200 |
| Frequency to (Hz) | 9000 |
| Abmessungen & Korb | |
|---|---|
| Diameter | 8 |
| Voice coil (inch) | 2 |
| Mounting depth (mm) | 106 |
| Weight (kg) | 4.9 |
| Thiele-Small-Parameter | |
|---|---|
| Re (Ω) | 5.1 |
| Le (mH) | 0.7 |
| Fs (Hz) | 89 |
| Qms | 4.03 |
| Qes | 0.28 |
| Qts | 0.26 |
| Vas (l) | 13.7 |
| Xmax (mm) | 3 |
| BL (Tm) | 13.1 |
| Mms (kg) | 0.0169 |
| Sd (m²) | 0.0227 |