Harbeth Nelson Bass Extender with Stand
3 600,00 €
Harbeth Nelson is an active bass extender and stand for compact sealed-box bookshelf speakers. It is optimised for the Harbeth P3ESR and BBC LS3/5A. Its integrated 50 W RMS digital amplifier extends the speakers’ low-frequency range. DSP manages the crossover, phase and response shaping, while the listener adjusts only the bass level. An integrated cable takes the signal from the main speaker terminals.
Harbeth Nelson bass extender is an active low-frequency module that also serves as a stand for a compact loudspeaker. According to the seller, it is optimised for the Harbeth P3ESR and BBC LS3/5A models. Compatibility with other sealed-box bookshelf speakers must be checked before purchase. An integrated 50 W RMS digital amplifier drives the bass unit. In free-field conditions, the system covers 35-75 Hz within ±3 dB.
Speaker stand and bass module in one
The main speaker sits on a mounting plate positioned 730 mm above the floor. The bass driver is installed in a bandpass enclosure, allowing the additional low-frequency module to fit beneath the bookshelf speaker. This arrangement removes the need to find a separate position beside the speaker for a conventional subwoofer cabinet.
Digital signal processing (DSP) controls the crossover frequency, phase and frequency-response shaping. The module operates in the range where the main speaker’s bass output begins to roll off. These parameters do not need to be adjusted with measuring equipment.
Connecting it to your system
An integrated cable takes the signal from the same main-speaker terminals that feed the loudspeaker. The system therefore does not require a separate low-level output from the amplifier. The impedance of the transformer-balanced active input exceeds 5 kΩ, so the input circuit presents the main amplifier with an almost negligible additional load.
Switch off the amplifier before making any connections. Check the terminal polarity carefully and make sure every cable has secure contact before powering the system again.
Adjusting the bass level
The listener is given a single bass-level control. It allows the module to be matched to the recording, the room acoustics and personal preference. DSP handles the crossover frequency, phase and response shaping, so there are no separate switches for these parameters to configure.
Begin with a low setting and listen from your usual seating position. Increase the level until the bass supports the main speakers without masking or overpowering vocals. Then compare several recordings you know well. This helps prevent choosing a setting that works for only one track.
Dimensions and positioning
The enclosure’s 350 mm diameter determines the required floor space. Adding the spikes increases the overall stand height by 20 mm. The chosen position should be level and provide enough room for the entire base of the enclosure.
With a P3ESR speaker installed, the total height to the top of the speaker is 1,145 mm. The P3ESR tweeter is then positioned at a height of 970 mm. These two measurements apply specifically to the P3ESR. With another speaker model, the listening-axis height will depend on its cabinet dimensions and driver layout.
Technical specifications
| Type | Active bass extender and speaker stand |
|---|---|
| Intended application | According to the seller, optimised for Harbeth P3ESR and BBC LS3/5A models; compatibility with other sealed-box bookshelf speakers must be checked |
| Bass driver | Manufactured by Harbeth |
| Enclosure type | Bandpass enclosure |
| Amplifier | Digital, 50 W RMS |
| Frequency range | 35-75 Hz, ±3 dB in free-field conditions |
| Input | Active, transformer-balanced |
| Input impedance | More than 5 kΩ |
| Signal connection | Integrated cable for the main speaker terminals |
| User control | Bass level |
| DSP-controlled parameters | Crossover frequency, phase and frequency-response shaping |
| Power requirement | 24 V DC, 2.5 A |
| Power connector | 5.5/2.1 mm, centre-positive |
| Power protection | Reverse-polarity protection |
| Mounting-plate height | 730 mm |
| Height increase with spikes | +20 mm |
| Height with P3ESR | 1,145 mm to the top of the speaker |
| P3ESR tweeter height | 970 mm |
| Diameter | 350 mm |
| Unpacked weight per unit | 7.6 kg |
| Packed weight per unit | 11.2 kg |
FAQ
Is this a subwoofer or a speaker stand?
It performs both functions. A bookshelf speaker sits on the upper mounting plate, while the active module extends the speaker’s low-frequency range.
Does the amplifier need a subwoofer output?
No. The integrated cable takes the signal from the main speaker terminals, allowing the module to be connected to a conventional stereo amplifier’s speaker circuit.
How should I set the correct bass level?
Use a familiar recording and begin with a low setting. From your normal listening position, gradually raise the level until the bass complements the music without becoming noticeably dominant.
Can it be used with other bookshelf speakers?
According to the seller, the model is optimised for the Harbeth P3ESR and BBC LS3/5A. Before using another sealed-box bookshelf speaker, check compatibility, the size of its base and the resulting overall height.
What power supply is required?
A 24 V DC, 2.5 A power supply is required. It must use a 5.5/2.1 mm connector with a centre-positive contact. The supplied accessories have not been confirmed, so check before purchase whether this power supply is included.
