CurtPalme.com Home Theater Forum

416ray4538 · Joined: 14 Jul 2009 Posts: 517 Location: near Toronto Ont

I know that "some" of you are down on Bose equipment; I hope that it's their more recent efforts that have formed that view. I have 2 of their amplifiers. One is a 1800 series 3 that I bought because I had an 1801 since the early '70's. The 1801 has worked flawlessly, it's fairly powerful and doesn't seem to care how hard it's driven, and it was because of it that I bought the 1800. I bought the 1801 new and about 5 years later the house burned down. The meters melted, the knobs melted off, but it still worked so I had it sandblasted to clean it up and I still use it. My problem is the 1800 is fan cooled by a 2 stage fan. After about 10 minutes even without an input , the fan goes to high speed which would suggest that it's working when it should be sleeping. I don't like the noise. Shipping these things for the sake of repair would be kinda expensive.
Anybody in the Toronto area know someone who might be able to fix it?

**Curt Palme** · Posted: Thu Dec 08, 2011 1:27 am Post subject:

Finding vintage audio tech guys that work at a component level is really hard. I do it, and actually have worked on an 1800 and 1801, but seriously, they are HORRIBLE pieces of crap. (no offense).

Bose made them because at the time, very few people made amps powerful enough to drive their really inefficient 901 speakers to decent levels. They were power pigs (still are). They were marginally built and poorly designed. The one I repaired caught fire on one channel, but somehow I managed to get it going back 18 years ago and sold it dirt cheap to some guy that swore by them.

Any electronics that Bose made, or had made for them in the 1970s and 80s was crap. In your case, you're dealing with maybe bias that's off (do the heatsinks run hot?), or a leaky transistor or something that's failed marginally. Heck, maybe the fan sensing circuit is off. The thing is, with the dirt cheap price of power amps, both new and used, you can do a lot better than spending $70+ an hour repairing something that's ending it's useful life regardless. Very few people will have the schematic for this amp, fewer will be willing to work on it.

Just my $.02.

macgyver655 · Joined: 22 Aug 2007 Posts: 8508

Jeremy112 · Joined: 28 Sep 2006 Posts: 2649 Location: Fond du Lac, WI

no highs, now lows, must be BOSE!

My dad has a pair of 901 series 6 speakers, and yes, although 98% of the world craps on Bose, when you pair the 901 with a decent amp (Such as a Pioneer SX-1280, SX-1980 stereo receiver), they don't sound bad at all, I have heard plenty of expensive speakers costing as much as a pair of 901s and the 901s when properly setup sounds pretty darn good.

Though I will admit, I will take my Jamos over BOSE any day (at least Any Jamo speakers made before klipsch got ahold of them Sad

)

**AnalogRocks** · Posted: Sat Dec 10, 2011 1:19 am Post subject:

I always wanted to hear a set of BOSE 901's

416ray4538 · Joined: 14 Jul 2009 Posts: 517 Location: near Toronto Ont

I'm only using the 1801 to drive a pair of Altec 817's from 80 Hz to 800 Hz so not very demanding

Jeremy112 · Joined: 28 Sep 2006 Posts: 2649 Location: Fond du Lac, WI

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

According to this post, the 901's have a DC resistance (NOT impedance) of 12.9 ohms.

E = I * R. I = E / R. Current = 110V / 12.9ohms = 8.53 AMPS.

Do you really think those voicecoils can run over 8 AMPS without frying!?

By comparison a 100W lightbulb uses roughly 100W. Power = E * I, so I = Power / E, and voltage is 110V. I = 100/110 = 0.909 amps. The bulb's filament is designed to run at white-hot temperatures, AND it's in a vacuum. Run 9x more current through those 901 voicecoils and they'll get very bright, but only very briefly. Laughing

Jeremy112 · Joined: 28 Sep 2006 Posts: 2649 Location: Fond du Lac, WI

**Curt Palme** · Posted: Sat Dec 10, 2011 6:29 pm Post subject:

THE later Bose amp were made by Carver, late 90s.

These are the originals, the one with the big VU meters was terrible, the one below it with the LEDs up the middle was better.

http://www.ebay.com/itm/BOSE-1800-1801-SERVICE-MANUAL-PARTS-PCB-SCHEMATIC-BND-/300558902379?pt=Vintage_Electronics_R2&hash=item45fab4e46b

THe smaller Carvers kicked serious ass, the only mod that Bose had done was to put in a slow for their eq modules for their various speakers. THe Carver ones did put out 450 watts RMS per channel into 8 ohms, the older ones about 250-300 or so.

Ever cut open a Bose speaker? 16 gauge voicecoil wire (almost). Super thick, each speaker was 1.2 ohms, but they series'd them to make 8 ohms.

We put some Bose 402s and 502s into a 2500 seat arena. Lots of sound from tiny speakers...sounded great.

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

16ga voicecoil wire!?

OK, I retract my previous statement. The fuse would probably blow before the voicecoils did. Laughing

**Curt Palme** · Posted: Sat Dec 10, 2011 7:10 pm Post subject:

Well, not QUITE that thick, but way thicker than 'normal' speakers.

The 402s are rated at 100W RMS. At a Ritchie Brother's auction lot, we installed 12 of them, with 2 per channel on one of the late model 1800 amps. The only thing that drowned them out was a D9 bulldozer. Everything else could be heard.

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Looks like Bose is applying their "voicecoil" technology in creative new markets:

http://www.youtube.com/watch?v=eSi6J-QK1lw -- be sure to watch at least through 2:00
http://www.youtube.com/watch?v=cffHXhbIfaU

Jeremy112 · Joined: 28 Sep 2006 Posts: 2649 Location: Fond du Lac, WI

Holy crap, a company that makes speakers makes those technologies? That is amazing in itself, plus how smooth of a ride the Bose suspension was compared to standard.

Maybe they should have just started out with that instead of speaker design and manufacturing lol Smile

Very cool

416ray4538 · Joined: 14 Jul 2009 Posts: 517 Location: near Toronto Ont

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

A Hungarian firm copyed the Bose 901 in the '70s

These were terrible speakers for hi-fi, but at least they were extermely sensitive (2 Watts for 96dB SPL), I always thought that the Boses are also this sensitive speakers...