Tag Archives: Bose

Everything to Know about the Bose 901 Series IV Speakers & Active Equalizer Repair

Posted on August 10, 2026 by retrovoltage

A detailed look at the Bose 901 Series IV speaker system and Active Equalizer, with a brief history and explanation, plus repair tips and tricks, schematics, a discussion of the 5 different Active Equalizer versions for this generation, and a parts list with direct links to buy. Continue reading →

Posted in Audio, Bose, DIY, Electronics, Hi-Fi, Stereo, Vintage | Tagged , , , , , , , , , , , | 3 Comments

Everything to Know about the Bose 901 Series III Speakers & Active Equalizer Repair

Posted on July 31, 2026 by retrovoltage

A look at the Bose 901 Series III speaker system and Active Equalizer, with a brief history and explanation, plus repair tips and tricks, schematics, and parts list with direct links to buy. Continue reading →

Posted in Bose, Electronics, Hi-Fi, Stereo, Vintage | Tagged , , , , , , , , , , , , , | 1 Comment

Everything to Know about Bose 901 Series I and Series II Active Equalizer Repair & Speaker Systems (and the 800, too!)

Posted on June 12, 2026 by retrovoltage

A deep dive into the history and repair of Bose 901 Series I and II, plus the Bose 800, sourced from direct experience repairing more than 500 Active Equalizers. Includes vintage ad copy, photos, tips and tricks, schematics, and parts lists. Continue reading →

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Upcoming Projects for 2026

Posted on June 2, 2026 by retrovoltage

Having had a chance to unpack some of my shop from storage and settle in to the new space, I’ve got an idea of what projects I’ll be working on myself in between projects with my shop partner. Bose Active … Continue reading →

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Bose® Active Equalizer Test Platform

Posted on April 13, 2016 by retrovoltage

This project is going to take a while since I’m slammed in the shop, but I’m in the process of converting a Bose® 901 Series I Active Equalizer to  a test platform. With sockets for the transistors, and clip connections … Continue reading →

Posted in Audio, Bose, DIY, Electronics, Stereo, Test Equipment | Tagged , , , , , | 3 Comments

The Speaker Spotter – March 3rd, 2016

Posted on March 3, 2016 by retrovoltage

Some interesting stuff on Craigslist in this week’s The Speaker Spotter, a curated selection of Seattle’s local speakers for sale online. As always, Retrovoltage is not affiliated with any of these sellers and you should click through the link to the … Continue reading →

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What do we have here?

Posted on December 1, 2015 by retrovoltage

I was reading about how to build a capacitor checker from the December 1959 issue of Popular Electronics and stumbled across something that looked very familiar. I know that shape. Nearly identical to a Bose® 901 Series I/II cabinet, and even … Continue reading →

Posted in Audio, Bose, Collections, Commentary, DIY, Electronics, Vintage | Tagged , , , , , , , , , , , , , | 2 Comments

Bose® 402E Active Equalizer #102853 Repaired

Posted on November 30, 2015 by retrovoltage

The first Bose® 402E Active Equalizer, for the Panaray speaker system, just came through the shop. It’s a small speaker array system, designed around similar drivers in the 901, and uses an Active Equalizer for the same effect. They’re designed … Continue reading →

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The Speaker Spotter – Speakers of Craigslist: June 3rd, 2015

Posted on June 3, 2015 by retrovoltage

It’s back – the Speakers of Craigslist, a periodic round-up of what’s interesting on my local Craigslist these days. Sorry for the hiatus, putting these together is a bit of work! As always, I am not affiliated with any of … Continue reading →

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Bose® 901 Series VI Active Equalizer #199732 Repaired

Posted on February 20, 2015 by retrovoltage

A first for my shop, I recently worked on a Bose® 901 Series VI Active Equalizer! These are considerably newer than the Series I-IV that typically come through the shop, although they’re still getting to be 25+ years old at … Continue reading →

Posted in Audio, Bose, Electronics, Projects, Vintage | Tagged , , , , , | 1 Comment