18SOUND 15MB650
18SOUND (Eighteen Sound) 15MB650 — 15" / 15 inch · Woofer/Midrange (WM) · Subwoofer / Bass · Ferrite
3" voice coil · 8 Ω
Part no.: 42A-CHS-TT-18S-0020
Documents
18SOUND 15MB650 — 15" · Woofer
400 W AES · 101.5 dB Sensitivity · Frequency range 50 Hz – 4800 Hz
Technical data
- Diameter: 15 "
- Voice coil: 3 "
- Power handling: 400 W AES
- Sensitivity: 101.5 dB
- Impedance: 8 Ω
- Magnet: Ferrite
- Weight: 8.3 kg
- Mounting depth: 167 mm
- Frequency range: 50 – 4800 Hz
Datasheet (PDF) · Manufacturer page
Series: MB · Part no.: 42A-CHS-TT-18S-0020
18Sound 15MB650: 15" midbass with 101.5 dB and 20 Tm for compact vented boxes
101.5 dB sensitivity from a 15" ferrite driver: the 18Sound 15MB650 belongs to the MB series, which is designed for high-efficiency midrange and midbass duty. The 3" voice coil handles 400 W AES, moving mass is 77 g and the force factor 20 Tm. The result is a Qts of only 0.26, an unusually tight motor for an MB driver.
That motor is precisely what sets the 15MB650 apart from the more forgivingly tuned siblings in the MB series: with Fs 40 Hz, Vas 210 l and Qms 3.95 the EBP comes out at 148, which means a small vented box or a horn. The rated range is 50 to 4,800 Hz and inductance is 1.36 mH. With 4 mm Xmax this driver is no excursion champion either; it makes its level through efficiency. Weight is 8.3 kg, mounting depth 167 mm.
Use and enclosure
The vented guideline is about 66 l tuned to 56 Hz, with a lower cut-off around 69 Hz. For a 15" midbass that is pleasantly compact and suits a 2-way top working above a subwoofer. In that configuration you exploit the high sensitivity fully without stressing the 4 mm Xmax in the low bass. A sealed enclosure of roughly 33 l with a system resonance near 109 Hz works as a midrange chamber in a 3-way system where the lower crossover is set high enough. For other alignments, the enclosure calculator at 42.audio is available.
At the top, the 15MB650 can hand over to a compression driver well below 4,800 Hz, and with 1.36 mH inductance this works cleanly with a passive network too. Because the motor is strong and the cone light, the directivity deserves a look: a 15" cone beams in the upper part of its range, which influences both the crossover point and the horn choice.
What to look out for
- Qts 0.26 and 20 Tm: tight motor, wants a vented box around 66 l or horn loading.
- 101.5 dB: one of the most efficient 15" drivers in the 18Sound line-up.
- Xmax 4 mm: plan a subwoofer below it, a high-pass filter is mandatory.
- Re 5.5 Ω, 8 Ω nominal, 400 W AES: a small amplifier suffices, but still set a limiter.
- 8.3 kg, 167 mm mounting depth, ferrite magnet.
Frequently asked questions
15MB650 or 15MB700, which one is right for me?
The 15MB700 with Fs 42 Hz, Qts 0.29 and 202 l Vas sits closer to a classic vented alignment with more volume. The 15MB650 with Qts 0.26 and 20 Tm is the tighter driver, delivers 101.5 dB and fits a more compact box around 66 l. For compact tops with a sub it is the obvious pick.
Can the 15MB650 run without a subwoofer?
In a vented box around 66 l the lower limit sits near 69 Hz, enough for speech and many live applications but not for deep music bass. With only 4 mm Xmax it quickly runs out of excursion without a subwoofer.
Which compression driver pairs with the 15MB650?
For a 2-way top with a high crossover a 1" driver is sufficient; for more headroom at a lower crossover, a 1.4" driver. 42.audio carries 18Sound horns and waveguides in both throat sizes, and the driver database helps with the combination.
18Sound 15MB650: 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 15MB650 is a 15-inch woofer with ferrite magnet from the MB 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 15MB650 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 | 40 Hz |
| Total Q Qts | 0.26 |
| Electrical Q Qes | 0.27 |
| Mechanical Q Qms | 3.95 |
| Equivalent volume Vas | 210.0 l |
| Moving mass Mms | 77.0 g |
| Cone area Sd | 900 cm² |
| Linear excursion Xmax | 4 mm |
| Force factor BL | 20 Tm |
| DC resistance Re | 5.5 Ω |
| Voice coil inductance Le | 1.36 mH |
Enclosure suggestion
The EBP of 148 suggests a bass-reflex enclosure. EBP = fs / Qes = 40 / 0.27
Sealed (Qtc 0.707)
- Enclosure volume Vb
- 32.8 l
- System resonance Fc
- 109 Hz
- Cut-off frequency F3
- 109 Hz
Bass reflex (QB3 after Small)recommended
- Enclosure volume Vb
- 49.3 l
- Tuning frequency Fb
- 63 Hz
- Cut-off frequency F3
- 76 Hz
Vb is the required net internal volume, Fb the tuning frequency of the reflex port and F3 the frequency at which the level has dropped by 3 dB. Calculated approximation after Small. A starting point for simulation, not a finished build plan.
Comparable drivers
Same size, same type, Qts within ±30 %.
- Celestion TF1530fs 42 Hz · Qts 0.28 · Vas 162.2 l · in the database
- 18 Sound 15NMB1000fs 46 Hz · Qts 0.24 · Vas 124 l · in the shop
- 18 Sound 15MB700fs 42 Hz · Qts 0.29 · Vas 202 l · in the shop
- 18 Sound 15NMB420fs 42 Hz · Qts 0.29 · Vas 225 l · in the shop
- 18 Sound 15MB1000fs 48 Hz · Qts 0.31 · Vas 132.5 l · in the shop
- RCF MB15N401fs 42 Hz · Qts 0.19 · Vas 136 l · in the database
Specifications
| Allgemein | |
|---|---|
| Manufacturer | 18SOUND |
| Category | Low Frequency |
| Series | MB |
| Magnet | Ferrite |
| Impedance (Ω) | 8 |
| Power handling (W) | 400 |
| Sensitivity (dB) | 101.5 |
| Frequency from (Hz) | 50 |
| Frequency to (Hz) | 4800 |
| Abmessungen & Korb | |
|---|---|
| Diameter | 15 |
| Voice coil (inch) | 3 |
| Mounting depth (mm) | 167 |
| Weight (kg) | 8.3 |
| Thiele-Small-Parameter | |
|---|---|
| Re (Ω) | 5.5 |
| Le (mH) | 1.36 |
| Fs (Hz) | 40 |
| Qms | 3.95 |
| Qes | 0.27 |
| Qts | 0.26 |
| Vas (l) | 210 |
| Xmax (mm) | 4 |
| BL (Tm) | 20 |
| Mms (kg) | 0.077 |
| Sd (m²) | 0.09 |