Bose 901 + Tube amps

[Valvomaniac]

Hi,

I have a DIY Dynaco Pas2 preamp and a power amp built after the claus byrith 5-30

I am being offered a set of Bose 901 series VI speakers for a bargain price, will they suit the tube amps ?

I fear that the eqyalizer will effect the valve sound.

[Serge66]

Hi,

Years ago, I lent my Williamson clone to one of my brother's friend.
He had a set of 901, a Bose pre-amp,the equalizer and the power amp (all Bose).
He wired the tube amp in place of the Bose (after the equalizer).
He reported a vast improvement in sound.
He said that it was as if a blanket had been removed from around the speakers.

I was quite pleased with that. But after reading many posts on DIYaudio and others sites, I came across the meaning of the name Bose: Buy Other Stereo Equipment.

I think you will enjoy the change. Keep us posted.

Serge

[grindstone]

I have a friend with a set running off a 6L6 pp mcintosh. His speakers are very old, among the earliest. That combination does rock the house and his normal listening levels are quite loud. Works for him, but it's not a sound that's for me. Reminds me of being young (and him, too, I suspect, which is part of the draw

[kevinkr]

While I no longer remember the input impedance of that equalizer (and DON'T ask why I should!) I suspect it will form a very difficult load for a PAS-2 which really wants to see about 470K load on its outputs.

Without the EQ the speaker really does not perform anywhere near intended - the EQ is not optional because the unequalized response of all of those drivers is not flat or even close to it.

The newer 901 may also be significantly less efficient than the older versions despite the ports. No 901 would win an award for efficiency frankly.

I think there are better speakers out there (for tube amplifiers) - unless you are an avid fan of large symphonic works you will soon grow tired of the larger than life presentation this speaker produces.
I mean how large is that Bosendorfer piano supposed to sound? Any imaging present is shear artifice, and while pleasant it is in no way accurate, and with small jazz or chamber music it can be quite disconcerting.

Personally since this is a used pair and not all that suitable for the gear on hand I would pass. An old pair of Dynaco A-25 or refoamed Advents would be a happier match.

Disclaimer: Just my personal opinion, not one iota of scientific proof for the statements made above!!

[brosenau]

To be honest, you also need to know what's inside the Bose 901 to understand why the equalizer is necessry in the first place. I may be drifting away from the original question - yes, the 901s will sound better than they did before, but they aren't a good reference for sound reproduction in the first place.

Now, it's been a few years since I was on the sales floor (I sold Klipsch, JBL, Infinity, ADCOM, Carver, & a host of others). Case in point, the equalizer is necessary to operate the 901s because the 901s are simply a bunch of full-range drivers in a tuned port box. The problem is the lack of a flat frequency response for the speaker on its own. The EQ alters the sound (I believe) as much as 12db on both ends of the audio spectrum just to get the speaker to sound flat. That's a lot of gain to make up for the speakers' shortcomings.

Next, look at the circuit inside the speaker (if you can). You'll notice another handy device that looks like a light bulb - this is not a crossover network since the speaker only houses one size of driver. This device limits the dynamic range of the speaker and acts as a power protection device by obsorbing energy...that's energy that you, the listener, will no longer be enjoying.

OK, enough Bose bashing - I simply believe listeners would be better off listening to a tube amp through a speaker that offered better performance in the first place. Personally, I've owned many different kinds from JBL (L-7), Cerwin Vega, KLH, (and more) but I finally settled down to the Klipsch KM-6. I bought them back in 1993 and I still have them today.

Short answer - any speaker will sound better with a tube amp...just watch your output power levels accordingly.

Oh, one last note - Once you cannect the EQ into the circuit, you can ONLY run the 902s on that channel. Do not connect a different pair of speakers in parallel with the 901s - they will not reproduce sound correctly. I'd avoid the 901s as they will drastically limit your choices and options.