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Ifi Audio ''Retro'' LS3.5 Speakers
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Ifi Audio "Retro" LS3.5 Speakers

£595.83 Exc. VAT |  


Ifi Audio "Retro" LS3.5 Speakers

The LS3.5 is iFi’s 3.0 reboot of the classic BBS LS3/5A which is still now, half a century after its launch still in high demand and revered. iFi has taken the design back to its basic underpinnings and then re-engineered the LS3.5 ground-up for the 21st century. From designing the drivers (not OEM) to the cabinet terminals, where we were dissatisfied, we manufactured our own. This is the iFi level of attention to detail.

The Retro LS3.5 is in many ways a synthesis of the best of the BBC LS3/5A and dash of the Le Petite. We eliminated their respective drawbacks using the very latest technological advancements available. So think of the iFi LS3/5A as BBC LS3/5a+Le Petite with an injection of factor X.

iFi’s brand-new tweeter that is smooth as silk, literally

Silk is smooth, so why not make a tweeter from the ground-up using it at the core? The iFi 28mm tweeter is horn-loaded and uses a neodymium magnet. It is very much a 21st century product – that is, at the advanced edge of tweeter technology. The silk dome combines the lack of resonances at the top of the operating range (as found on metal domes) with excellent dynamics in band. The small neodymium magnet structure shifts cavity resonances outside the audible range. Being horn-loaded, it matches perfectly with the wideband driver to create a mammoth sound field.

The tweeter is used only at the very top end of the audible range; the whole range from 59Hz – 8kHz covering the fundamentals of all instruments except those with very low bass notes and all the formants (the tone forming harmonics of instruments) is covered by the wideband driver, without any electrical or mechanical crossover.

This avoids any damage to the phase/impulse response for this critical range. The simple arrangement of the crossover for the tweeter (first order at appx. 10kHz acoustic crossover) and the tweeters waveguide, which insets it for time-alignment with the wideband driver further preserves phase/impulse response.

Ground-up paper cone wideband driver

"natural material for a natural sound"

Natural material for a natural sound. The paper cone 115mm wideband driver by iFi performs more akin to a full-range driver.

In many ways the wideband driver is very traditional, both magnet and basket. Stamped steel baskets can dissipate energy much faster than cast ones. It harks back to the “golden era” of driver design in the 1970’s. Modern finite element modeling and modern materials have improved the driver in many areas (especially efficiency and bandwidth) over classics like the KEF B-110 which was originally used in the LS3/5A.

The wideband driver rolls off after 8kHz. And it reaches down to 59Hz (with correct placement).

Time-Aligned to perfection

The iFi LS3.5 has a coherency that is based upon the simple fact from the outset, the tweeter and driver are perfectly time-aligned. Simply put, this means if one was looking at a cross-section of the LS3.5, the acoustic centre of the tweeter and the wideband driver as precisely vertically-aligned. This means sound waves from both units arrive at ear of the listener at the same time (as opposed to at different times). This is an oft overlooked weakness of many speakers, but not in the iFi LS3.5.

Multi-chamber Voigt design with tuned enclosure

There are two-chambers in one. The enclosure is maybe best considered a variant of multiple reflex, also, by breaking up the larger volume into two smaller different volume/size sections resonance frequencies are spread and tuned to higher frequencies, where the Amino-plastic open cell foam we use for damping has optimal absorption.

The Acoustic Active Tuning with minimal damping drawn from the musical instrument manufacturing sector further assists with dissipating resonance frequencies higher – just think of the LS3.5 as a musical instrument.

This is why the LS3.5 is a speaker that makes music.

Bamboo is best

Bamboo is a grass – hence it is a sustainable material and exceptionally environmentally friendly. It is 2x lighter and 3x stronger than wood. The aforementioned Voigt design coupled with the “stiff as steel” bamboo enclosure and the extra reinforcement by the division plus the acoustic tuning – all combined, makes for a remarkably low sonic signature of the box. This is critical as the use of the single paper driver needed for the wide bandwidth cannot be counted upon to block resonances from inside the box passing through the way a heavy and slower plastic cone is able to.

Hence for environmental and sonic reasons, it made perfect sense to use it as a speaker cabinet material. The LS3.5 is 5x more costly to manufacture than standard MDF cabinets. A simple knuckle tap shows its complete lack of colouration – which is easily audible from the first note.

Advanced Amino-plastic open cell foam

For the very minimal internal damping duties, we scoured the world for the most advanced acoustic materials and settled on the Advanced Amino-plastic open cell foam material. The open-cell surface guarantees that sound waves are not reflected as an echo but can penetrate the cell structure unhindered. The sound energy is reduced in the cell structure, giving an excellent sound absorption capacity.

From our listening tests the ability to ensure the deepest and cleanest bass along with a mid-range that is spell-binding placed it heads and shoulders above all others.

Despite its much higher cost, we just had to have it in the LS3.5.

Binding posts that carry the signal unhindered

Leaving no stone unturned, we sourced a binding post that had the purest copper count, had the maximum surface area contact and had to be gold-plated for long-term enjoyment. Rest assured that even the banana speaker connectors we developed from the ground-up!

The silver-plated copper speaker cables and the gold-plated copper speaker connectors means the sound quality is simply unbeatable and means the LS3/5A can play with the “big boys”.


Sensitivity: 90dB/2.83V/1m
Freq response: 60Hz – 20KHz
Drivers: 4.5″ (115mm) Paper Cone Wideband Driver
  1.1″ (28mm) Silk Dome Tweeter
Crossover: 10KHz acoustic crossover
  no electrical crossover on Wideband Driver
  Frst Order High-Pass on Tweeter
Enclosure Principle: Transmission-Line port
  Solid Bamboo Enclosure
  Acoustic Active Tuning with minimal damping
Size: 146 x 268 x 226mm (W x H x D)

* all specification anechoic, 2pi steradians

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