Jbl L60 Studio Monitors: Reconditioning And Restoration Guide

The JBL L60T studio monitor is a two-way, floor-standing loudspeaker system with an 8-inch low-frequency transducer. It is known for its deep, tight bass and clear highs, thanks to its signature JBL sound and titanium tweeter. Over time, the foam surrounds on the woofer may deteriorate and need to be repaired or replaced. Some owners choose to recondition their JBL L60T studio monitors themselves, while others seek the help of professionals like Iwan Arjanto, a master craftsman based in Indonesia who specialises in restoring vintage JBL studio monitors.

Repairing rotted enclosures

Assess the Damage:

Begin by carefully inspecting the enclosures of your JBL L60T studio monitors. Look for signs of rot, deterioration, or any other damage. Rotted enclosures are often characterised by soft or crumbling wood, discolouration, and a musty odour. It's important to identify the extent of the damage to determine the best course of repair.

Disassemble the Speakers:

Before you can repair the enclosures, you'll need to carefully disassemble the speakers. This will involve removing the drivers, crossover components, and any other internal parts. Take photos or make notes during this process to ensure you can reassemble everything correctly later. Be gentle with the components and store them safely to avoid any further damage.

Repair or Replace the Enclosures:

If the enclosures are badly rotted, it might be more time-efficient to build new enclosures from scratch rather than attempting to repair them. This involves carefully measuring the dimensions of the original enclosures and replicating them using new materials. However, if the damage is minimal, you can try to repair the rotted areas. Use a wood hardener to consolidate and strengthen the rotted wood, then fill in any holes or cracks with wood filler. Sand the surfaces smooth after the filler has dried.

Refinish the Enclosures:

Once the structural repairs are complete, you can refinish the enclosures to restore their original appearance. This might involve staining or painting the wood to match the original colour. Pay attention to the type of finish used on the original enclosures and try to replicate it as closely as possible.

Reassemble the Speakers:

After the enclosures have been repaired and refinished, it's time to put your speakers back together. Refer to the photos or notes you took during the disassembly process to ensure you're reconnecting everything correctly. Be careful not to overtighten any screws, as this could damage the wood or the components.

Testing and Fine-Tuning:

Once your speakers are reassembled, connect them to an amplifier and test their sound quality. Pay attention to any unusual noises or distortions. Fine-tune the placement of the drivers and crossover components if needed to optimise the sound.

Repairing the JBL 4355 port

When repairing the JBL 4355 port, it is important to have a clear understanding of the speaker's design and functionality. The JBL 4355 is a large and powerful speaker system that was originally released in the 1980s and has gained a reputation for its exceptional sound quality.

The first step in repairing the port is to carefully inspect the speaker and identify any damage or deterioration. Over time, the foam surrounds on the woofer can rot and deteriorate, affecting the bass response of the speaker. This is a common issue with the JBL 4355 and other vintage speakers. It is crucial to replace the foam surrounds with a suitable repair kit or seek the services of a professional repair centre that can perform re-foaming at a reasonable cost.

Additionally, it is important to inspect the condition of the speaker drivers, as they may require reconing or replacement if they are damaged or worn out. The JBL 4355 utilises a combination of different drivers, including the JBL 2245, 2202, 2440, and 2405, among others. These drivers should be handled with care and expertise, as they are crucial to the speaker's performance.

When repairing the port, it is essential to consider the placement of the speakers. The JBL 4355 benefits from being placed away from walls, especially the back wall, to prevent the low bass from becoming overwhelming. Raising the speakers slightly off the floor can also improve the bass response and create a cleaner, better-defined sound.

Furthermore, the JBL 4355's design allows for customisation and experimentation. Some enthusiasts have shared their experiences with building their own enclosures, crossovers, and even creating a unique "soundbar" system by combining multiple JBL 4355 components. While these modifications may not be for everyone, they showcase the versatility and dedication of the JBL 4355 user community.

Lastly, it is worth noting that the JBL 4355 is a rare and sought-after speaker system. With only a limited number of pairs produced, finding replacement parts or complete systems can be challenging and expensive. It is always advisable to consult experts or trusted repair centres when attempting any repairs or modifications to ensure the best possible outcome.

Sourcing parts

The JBL L60T studio monitor is a loudspeaker that was released in the early 1980s. It is a two-way, floor-standing system with an 8-inch low-frequency transducer and a titanium high-frequency transducer (035Ti). The 035Ti tweeter has a very wide frequency curve, allowing it to be used in various speaker configurations.

One common issue with the L60T is the foam surrounds on the woofer, which tend to rot after a few years of use. Kits are widely available to replace the foam surrounds, and many professional repair centres can also perform this service at a reasonable price.

Another important component is the rear bass port, which helps to enhance the bass response of the speaker. It is important to note that the L60T should be placed away from back walls to prevent the low bass from becoming overwhelming.

Additionally, the L60T can be paired with stands to improve the bass response further. Custom stands for the L60T are available from A&M Fabrication.

For other parts, it is recommended to consult with professional audio equipment repair centres or authorised JBL service centres, who may have access to replacement parts or be able to advise on suitable alternatives.

Testing and refurbishing

Testing and Inspection:

• Inspect the speakers for any visible damage, such as rotted foam surrounds on the woofer, which was a common issue with the JBL L60T woofers after a dozen years of use.
• Test the horn and tweeter assemblies, as these are often unbreakable and can be salvaged.
• Check the network crossover and L-pad for any issues. Vintage monitors may have old capacitors that are no longer precise and need replacement.
• Assess the condition of the enclosure. JBL used particleboard for old models, which could break down over time due to extreme humidity.
• Test the bass response by placing the speakers away from walls and corners, as the rear bass port can cause overwhelming low bass if placed too close to reflective surfaces.

Refurbishing and Repair:

• For damaged enclosures, consider reconstructing a new one from scratch, as it may be more time-consuming to repair a badly rotted enclosure.
• Source replacement parts such as bass drivers, compression drivers, horns, and crossovers from local suppliers or online platforms like eBay.
• If you plan to re-foam the woofer, proceed with caution and consider seeking professional help. While kits are available, the process is tedious and requires careful centering of the cone during the final gluing step.
• When refurbishing vintage studio monitors, test them extensively before sending them to customers to ensure optimal performance.
• Consider joining online communities and forums, such as the Lansing Heritage Forum, to seek advice and measurements from other enthusiasts working on similar projects.

Building new cabinets

Planning and Materials

Before you start building, it's important to have a clear plan and gather the necessary materials. Determine the size and shape of your cabinet, considering factors such as bass extension, efficiency, and volume. Gather materials like 3/4" medium-density fiberboard (MDF), plywood, silicone or latex caulk, screws, braces, and damping material like fiberglass or polyester.

Construction

When constructing the cabinet, use butt joints or more advanced woodworking techniques to assemble the panels. Seal the joints with caulk and reinforce the structure with braces to reduce vibrations. Follow the steps outlined by HUMAN Speakers for installing the terminal plate, crossover, and drivers. Remember to test the speakers gradually to ensure proper functioning.

Finishing

You can finish your cabinets with paint, real wood veneer, or fabric. For paint, follow standard auto body preparation techniques, including sanding and applying body filler. If using wood veneer, consider mitered or notched joints to maintain a high-quality appearance. You can also add moldings to integrate the cabinets with your home decor.

Tips and Tricks

• Building speaker cabinets is time-consuming and requires the right tools and patience.
• Expect the project to cost more than initially anticipated.
• Designing a good crossover can be challenging without an electronics background.
• Use a cardboard mock-up to test the design and finish before building.
• Rounding the cabinet edges can reduce frequency response peaks and troughs.
• Use medium-density fiberboard, plywood, or a combination of both for the cabinet material.
• Brace the cabinet internally to reduce panel vibrations.
• Place the braces asymmetrically to minimize the impact of standing waves.
• Counter-sink all drivers to improve sound quality.
• Separate the midrange driver in its own internal enclosure for cleaner performance.
• Allow for a minimum of 3-5 full days of work for a high-quality tower loudspeaker cabinet.

Frequently asked questions