JBL t LSR28P Linear Spatial Reference Bi-Aplified Studio Nahfeld Monitor defekt

JBL LSR28P Linear Spatial Reference Bi-Aplified Studio Nahfeld Monitor defekt
Hochtöner eingedrückt, gibt aber Höhen ab.
Sicherung kommt nach 5sek. voll Pegel.
Es handelt sich um gebrauchte Geräte aus Vermietbestand.
Altersgemäßer Gebrauchtgeräte Zustand, verkauft wird nur, was auf den Bildern zu sehen ist.
Aus dem zum Artikel gehörigen technischen Informationen des Herstellers haben wir folgende Daten entnommen:
The LSR in the title of this monitor stands for 'Linear Spatial Reference' and refers to part of JBL's new‑found design technique. The basic idea revolves around taking accurate measurements of the frequency response in the complete sphere around the loudspeaker, and then optimising the various design parameters to produce as smooth an overall frequency response as possible. The theory is that this approach gives a much more consistent sound than purely on‑axis design techniques, since the direct, reflected and reverberant sound fields created by the speaker (and its cabinet) .
The LSR28P design uses the same titanium composite tweeter as the bigger LSR32s, complete with the Elliptical Oblate Spheroidal (EOS) Waveguide — who dreams up these terms? This waveguide is simply an aid to generating a predictable dispersion characteristic for the treble energy. Coupled to the tweeter is a JBL model 218F 8‑inch bass unit derived from the larger 252G 12‑inch woofer used in the flagship monitors. This smaller bass/mid‑range unit shares the same Differential Drive technology as the 252G, with two driven voice coils plus a central third, shorted, coil which acts as a dynamic brake, and a graphite/polypropylene composite cone.
The cabinet has a 50‑litre volume — the same as the three way LSR32 design — and is ported to the rear via a 'Linear Dynamics Aperture Port' which is a flared design intended to reduce 'chuffing' and port compression by matching the internal and external air impedances correctly. The cabinet resonance is tuned to a low 40Hz. Like that on the flagship model, the 28P's front baffle is made of a carbon‑fibre composite which looks very impressive and is as solid as a rock. The speaker feels as though it's made of stone, too, weighing in at a considerable 20.5kg (45lbs) — much heavier than anything this small (406 x 330 x 324mm) ought to be!
The active crossover splits the audio input into two bands at 1.8kHz, with a sixth‑order Butterworth or fourth‑order Linkwitz‑Riley filter (user selected) for the bass section and a fourth‑order Linkwitz‑Riley filter at 1.8kHz for the top end. The overall frequency response is quoted as 37Hz‑22kHz at the ‑6 dB points, and the bass frequencies are handled by a 200W amplifier whilst a 70W amplifier feeds the treble driver. Audio input connection is via a combi‑jack socket accepting balanced or unbalanced signals on quarter‑inch jack or XLR. The XLR is configured for +4dBu signals, whilst the jack accepts ‑10dBV levels, although a bank of DIP switches hidden away on the rear panel allow a good range of adjustments. A screwdriver‑operated rotary level trim is normally out of circuit, but can be introduced by the first DIP switch if required, for precise and individual level matching over a 12dB range. The second and third switches provide 4, 8 or 12dB of fixed attenuation.
The next three DIP switches affect the bass response of the speaker. With all switches in their off position, the response falls at 36dB/octave and is maximally flat. However, this can be changed to 24dB/octave with switch four, if required, to increase the bass extension slightly (at the expense of reduced power handling). Switches five and six alter the overall 36dB/octave slope by 2dB up or down below about 150Hz, and are provided to compensate for room effects caused by positioning the speakers near a rear wall, for example. Similar provision is available for the tweeter, with +/‑2dB trims above 1.8kHz on switches seven and eight.
Other rear‑panel facilities include a mains voltage change‑over switch (120 or 240V), a mains fuse, a push button to power the unit, and an IEC 3‑pole mains connector. Much of the rear panel is taken up with vertical fins forming a heatsink for the internal amplifier packs, which generally run warm to the touch. The only indicator is on the front panel (obviously) and is normally illuminated green when the unit is powered, but flashes red if the signal level nears the onset of amplifier clipping. When the unit is first powered, there's a switch‑on mute delay that prevents thumps and clicks from reaching the loudspeaker.