18SOUND 15NTLS3500
18SOUND (Eighteen Sound) 15NTLS3500 — 15" / 15 inch · Hi-Fi/Studio Woofer · Subwoofer / Bass · Neodymium · Dual-Gap
2x3.5" voice coil · 8 Ω
Part no.: 42A-CHS-TT-18S-0058
Documents
18SOUND 15NTLS3500 — 15" · Woofer
950 W AES · 89 dB Sensitivity · Frequency range 30 Hz – 2000 Hz
Technical data
- Diameter: 15 "
- Voice coil: 3.5 "
- Power handling: 950 W AES
- Sensitivity: 89 dB
- Impedance: 8 Ω
- Magnet: Neo
- Weight: 8.3 kg
- Mounting depth: 261 mm
- Frequency range: 30 – 2000 Hz
Datasheet (PDF) · Manufacturer page
Series: NTLS · Part no.: 42A-CHS-TT-18S-0058
18Sound 15NTLS3500: 15" long-throw woofer with 15.3 mm Xmax for studio and hi-fi
The 15NTLS3500 steps outside the usual line-up of 15" pro woofers. 18Sound designed it as a low-frequency driver for hi-fi and studio use: 15.3 mm linear excursion, 28 Hz resonance and Qts 0.42 describe a driver built for deep, clean bass in reasonable volumes rather than maximum efficiency. Its 89 dB sensitivity is the deliberate consequence of 250 g moving mass and a long suspension.
The motor is a neodymium dual-gap design with two 3.5" voice coils, handling 950 W AES and delivering BL 21.6 Tm. The double-gap construction gives more uniform force across the long stroke, which is decisive for low distortion at 15.3 mm Xmax. Nominal impedance is 8 Ω (Re 5.2 Ω), inductance 1.65 mH, weight 8.3 kg, and the stated range is 30 Hz to 2000 Hz.
Use and enclosure
With an EBP of 64 the 15NTLS3500 is one of the few 15" drivers that works well both sealed and vented. Sealed, the guide value is around 77 l with fc 47 Hz – a very tight subwoofer for control rooms or home cinema, where the long stroke makes up for the missing port support. Vented asks for more space: about 175 l net tuned to 26 Hz with an f3 near 25 Hz. That is genuine sub-bass, making full use of the 30 Hz lower limit. You can compare both alignments in the enclosure calculator at 42.audio.
The 261 mm mounting depth is substantial and must be planned into the cabinet. Cross low as a subwoofer; in a large 2- or 3-way speaker the driver can also cover the lower midrange, as long as you stay well below 2000 Hz.
What to look out for
- Xmax 15.3 mm with a dual-gap neodymium motor and two 3.5" coils.
- Fs 28 Hz, Qts 0.42, Vas 141 l: sealed around 77 l or vented around 175 l.
- 89 dB sensitivity: plan for adequate amplifier power into 8 Ω.
- Mounting depth 261 mm, weight 8.3 kg.
- 950 W AES power handling.
Frequently asked questions
Why is the 15NTLS3500 sensitivity only 89 dB?
Because it is designed for extension and excursion rather than efficiency: 250 g of cone mass, 28 Hz resonance and 15.3 mm Xmax all cost sensitivity. With 950 W power handling you make up for it with the amplifier.
Sealed or vented?
Sealed (guide value 77 l, fc 47 Hz) is more compact and tighter; vented (guide value 175 l, fb 26 Hz) goes noticeably deeper with an f3 around 25 Hz. For control rooms with limited space sealed is often the better choice, for home cinema the large vented box.
How does it differ from the 15W750 in the shop?
The 15W750 is a classic pro woofer with ferrite magnet, high efficiency and much less excursion. The 15NTLS3500 trades efficiency for 15.3 mm stroke and 28 Hz resonance, making it the driver for controlled sub-bass rather than sound reinforcement.
18Sound 15NTLS3500: 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 15NTLS3500 is a 15-inch woofer with neodymium magnet from the NTLS 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 15NTLS3500 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 | 28 Hz |
| Total Q Qts | 0.42 |
| Electrical Q Qes | 0.44 |
| Mechanical Q Qms | 8.2 |
| Equivalent volume Vas | 141.0 l |
| Moving mass Mms | 250.0 g |
| Cone area Sd | 881 cm² |
| Linear excursion Xmax | 15.3 mm |
| Force factor BL | 21.6 Tm |
| DC resistance Re | 5.2 Ω |
| Voice coil inductance Le | 1.65 mH |
Enclosure suggestion
The EBP of 64 is in the intermediate range — either works; sealed plays tighter, bass reflex deeper and louder. EBP = fs / Qes = 28 / 0.44
Sealed (Qtc 0.707)
- Enclosure volume Vb
- 76.9 l
- System resonance Fc
- 47 Hz
- Cut-off frequency F3
- 47 Hz
Bass reflex (QB3 after Small)
- Enclosure volume Vb
- 161.1 l
- Tuning frequency Fb
- 27 Hz
- Cut-off frequency F3
- 26 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 %.
- Usher 15PAfs 35.79 Hz · Qts 0.43 · Vas 208.83 l · in the database
- 18 Sound 15W750fs 40 Hz · Qts 0.42 · Vas 182 l · in the database
- B&C Speakers 15PS100fs 39 Hz · Qts 0.43 · Vas 103 l · in the database
- FaitalPRO 15FH500fs 35 Hz · Qts 0.45 · Vas 217.1 l · in the database
- FaitalPRO 15FH520fs 36 Hz · Qts 0.39 · Vas 186.5 l · in the database
- SB Audience BIANCO-15MW500fs 39 Hz · Qts 0.4 · Vas 171 l · in the database
Specifications
| Allgemein | |
|---|---|
| Manufacturer | 18SOUND |
| Category | Low Frequency |
| Series | NTLS |
| Magnet | Neo |
| Impedance (Ω) | 8 |
| Power handling (W) | 950 |
| Sensitivity (dB) | 89 |
| Frequency from (Hz) | 30 |
| Frequency to (Hz) | 2000 |
| Abmessungen & Korb | |
|---|---|
| Diameter | 15 |
| Voice coil (inch) | 3.5 |
| Mounting depth (mm) | 261 |
| Weight (kg) | 8.3 |
| Thiele-Small-Parameter | |
|---|---|
| Re (Ω) | 5.2 |
| Le (mH) | 1.65 |
| Fs (Hz) | 28 |
| Qms | 8.2 |
| Qes | 0.44 |
| Qts | 0.42 |
| Vas (l) | 141 |
| Xmax (mm) | 15.3 |
| BL (Tm) | 21.6 |
| Mms (kg) | 0.25 |
| Sd (m²) | 0.0881 |