Speaker Replacement in an Express Cruiser.

This project covers goes into some detail concerning speaker and enclosure design. I have included a discussion on designing speaker enclosures for a boat - which is often a compromise". This information may be helpful should an alternate speaker arrangement be chosen.

A primer on speaker selection and enclosure design.

The cockpit speakers are known as infinite-baffle, as there are no dedicated enclosures behind them. The Polk speakers I am using work well in both infinite-baffle as well as defined enclosures, and since there is not a lot of access behind the speakers, I opted to retain the infinite-baffle style.

As is typical of many boats, this boat has an asymmetrical speaker arrangement in the cockpit. The first speaker to tackle is the port-side cockpit speaker. The speaker is a common 6 1/2" coaxial speaker, mounted behind a vinyl rub-panel. The speaker opening is behind that black part of the panel. It is made from a piece of speaker grille cloth stapled over what looks to be starboard. While this is adequate, the years of being outside has resulted in watermarks and fading of the cloth. It just looks old. So I will be upgrading the speaker as well as replacing the grille.



My solution is to replicate this panel in wood - and I am going to use Bubinga! While the boat's interior is Cherry, the fake woodgrain dash in the cockpit matches Bubinga, and Cherry doesn't stand up to the outside elements very well. Bubinga is an exotic tropical wood and can be found - or at least a plastic imitation - on many modern boat dashboards.

As shown here, I have constructed the piece to be used as the grille out of solid Bubinga, along with a metal grille and piece of grille cloth that will be attached from the rear.


On the left, the original factory speaker grille cover, which was a piece of speaker grillecloth stapled around a piece of starboard. As you can see, the cloth was not very well suited for the outdoors, and had water stains. On the right, my completed replacement speaker grille with a solid piece of Bubinga, with a metal grille siliconed to the rear of the wood.

The speakers I selected are Polk db65xs (db-650, db-651, db-651s, and so on). They have an automotive aftermarket standard pins, which requires the use of a 1/8" and 3/16" terminal connectors, rather than the standard 1/4" connectors that the boat had.

The mounting solution was either to solder the speakers directly to the wires, or find the small terminals. I went to the local Best Buy that had a stereo installation department, and was able to buy a set of adapters designed to retrofit GM (General Motors) vehicles. I cut off the "GM" end and replaced them with standard 1/4 connectors to match the existing wiring harness. Since this writing, I have located a source of the smaller 1/8" and 3/16" connectors (www.mouser.com). However, on the day of the speaker installation, I needed something quick, and didn't have the time to order the connectors.

The speakers were the same size as the originals, so I didn't have to do any hole cutting or patching. To improve the speaker installation, I ran a bead of silicone sealant behind the speaker frame then and screwed them into the original location. It is important to silicone the speakers so that there are no air gaps, or chance of vibration between the speaker and fiberglass. As the silicone makes the speakers air tight, it provides an infinite-baffle type of "enclosure". It is very important that the speakers are air tight, otherwise any air leaks will reduce the fidelity of the speakers.


Use silicone here rather than more aggressive marine sealants such as 3M 101, 4200, 5200, or other like compounds. Silicone will provide an adequate air-tight seal here, yet allow the speaker to be removed (with a bit of effort). If any of the marine sealants are used, the speaker may be permanently glued to the boat.

The installation of the speaker cover is complete. The change out of the cloth to the wood panel gives the cockpit a richer feeling. And it is easier to maintain. All that is required to keep the piece new looking is a periodic maintenance coat of wood finish.

The starboard cockpit speaker was also siliconed in place, but this time, the stock speaker grille was used rather than the custom made wood cover.

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