My expectations Bose 901 and setup

[whoaru99]

As mentioned earlier in the thread, unless the 901s are used over a pretty narrow range, the 901 EQ has a lot of affect on the response specifically tailored to the 901s. The correction it does you really wouldn't want applied to the sub or to the added HF unit.

For broadband tuning, if desired, then perhaps an EQ between the receiver and the crossover but the 901 EQ still in path to the 901s.

 

[peterp1]

As mentioned earlier in the thread, unless the 901s are used over a pretty narrow range, the 901 EQ has a lot of affect on the response specifically tailored to the 901s. The correct it does you really wouldn't want applied to the sub or to the added HF unit.

For broadband tuning, if desired, then perhaps an EQ between the receiver and the crossover.

Does the Bose EQ do EQ over the entire frequency range (while only making the Bass and Treble adjustable) or does it only act on the bass and treble frequencies? (sounds like from your comment it is the entire range)

The sub would be bypassed from EQ when driven by the receiver preamp out. Unfortunately, there is probably no way to bypass EQ for the super-tweeter since it is driven by receiver speaker-level outputs.

 

[whoaru99]

The EQ correction curve (for 901 Series V/VI) is posted back in #17. As you'll see there is no point on the curve where it's actually flat. Only through a rather narrow swath is it even remotely close to flat. Those are 5dB increments on the vertical scale.

 

[Lombardo]

To me, there is a very simple solution that doesn't require any crossovers and likely won't require any EQ either.

For lows: Add a powered sub, driven by the receiver pre-amp left/right outputs (don't use the left/right speaker outputs to drive the sub if you are applying EQ to the 901's). The sub has a built-in crossover and level control that will allow you to tune it to blend with the Bose 901's -- that's all you need for the bass. The external crossover does not help you at all for the sub, nor does EQ, either one would make things worse for sub performance. Sub requirements: 1. Sub must have left and right RCA inputs (some subs only have a mono LFE input). 2. Generally, a sealed sub is better for music than a ported sub (ported are more efficient, but tend to have group delay that makes it more difficult to time align with mains). 3. Probably better to have a phase knob rather than a phase switch (for time-alignment with 901's).

For Highs: Add a super-tweeter with adjustable crossover and adjustable level (this will allow you to fill out the highs and tune them to blend with the 901's (e.g. the Super-tweeter takes over where the 901's start trailing off). This will give you much better control and better quality treble than trying to blend in bookshelf speakers with tweeters. Unfortunately super-tweeters (powered by speaker-wire) will pick up any EQ you do on 901's, but you won't need to boost highs with super-tweeters in the system. The Aperion Audio Planar-Ribbon Super Tweeter (back panel control picture shown below) are $299 a pair on Amazon.

For Mids: Power 901's with the receiver speaker outputs, you likely won't need any EQ with a sub and super-tweeter tuned properly. If you do decide to add EQ, you can buy some high quality 10 or more band eq's for not very much on auction sites since analog EQ's aren't really in favor these days (for whatever reason). I've got to imagine that a 10-band can give you more control than the bass/treble Bose EQ (<- but I have NO experience with the Bose EQ unit, so hopefully somebody will correct me if I'm wrong).

All great info thanks. I appreciate the input with the Sub and will try tonight to disconnect from speaker wire and plug into pre amp.

 

[Lombardo]

Good specs and power, 240 wpc @ 8Ω (stereo), 700 wpc @ 8Ω (mono)

VS Pioneer Spec 2 (slightly higher asking price) which would you recommend?

 

[peterp1]

The EQ correction curve (for 901 Series V/VI) is posted back in #17. As you'll see there is no point on the curve where it's actually flat. Only through a rather narrow swath is it even remotely close to flat. Those are 5dB increments on the vertical scale.

Thanks. I saw the curve, but I thought that chart was the room response with a 901 being driven by an amp using the Bose EQ rather than a plot of the EQ itself.

The peak level in that curve shows the signal at -10db, and some frequencies are down -30db. Could the overall attenuation of the EQ unit be part of the reason people are some people are mentioning volume issues on the 901's?

 

[whoaru99]

Thanks. I saw the curve, but I thought that chart was the room response with a 901 being driven by an amp using the Bose EQ rather than a plot of the EQ itself.

The peak level in that curve shows the signal at -10db, and some frequencies are down -30db. Could the overall attenuation of the EQ unit be part of the reason people are some people are mentioning volume issues on the 901's?

The graph is not aligned to a specific dBV or whatever, it wasn't really intended to show anything other than the big effect/overall shape of the curve. But, my understanding is that there may be small area of cut in the mid range, but it's mostly boost and rather dramatic boost at that as you see. Maybe at some point I'll align the graph to a known reference value but not likely any time soon. That won't change the relative values though.

 

[peterp1]

The graph is not aligned to a specific dBV or whatever, it wasn't really intended to show anything other than the big effect/overall shape of the curve. But, my understanding is that there may be small area of cut, but 90% if it is boost, and rather dramatic boost at that as you see.

Thanks. This all makes sense. Your chart makes it clear how much the 901 needs the EQ to hear what was intended. An upscale lounge we used to go to had 901's hanging from the ceiling -- looked beautiful but sounded godawful -- I'm guessing the were running without EQ, and the placement was probably wrong also. I've never heard a properly set up set of 901's, would love to though.

 

[wallacefl]

Ran a party years ago in an A frame house with 901s suspended from rafters ...fun but my conclusion was that the stacked quad OLA we used on the the floor were way more fun....really if I were to try it the 901 again I would try it as a midrange only triamped with a Heil tweeter and a JBL woofer.

 

[Lombardo]

I know the Spec 2 has been known to underestimate their power and overestimate their harmonic distortion. But besides that how important is frequency response range? Notice the Spec 2 is a much broader range. Is this good or bad? Let me guess. It’s complicated...

Pioneer spec 2
Power output: 250 watts per channel into 8Ω (stereo)

Frequency response: 5Hz to 80kHz

Total harmonic distortion: 0.1%

Damping factor: 50

Input sensitivity: 2V

Signal to noise ratio: 110dB

Speaker load impedance: 4Ω to 8Ω

Semiconductors: 55 x transistors, 75 x diodes

Dimensions: 480 x 186.5 x 445mm

Weight: 24.3kg

Year: 1976

Yamaha
PC2002M

Power output: 240 watts per channel into 8Ω (stereo), 700 watts into 8Ω (mono)

Frequency response: 10Hz to 50kHz

Total harmonic distortion: 0.05%

Damping factor: 200

Input sensitivity: 0.775V

Signal to noise ratio: 115dB

Dimensions: 480 x 413 x 183mm

Weight: 20.5kg

Year: 1982

 

[whoaru99]

It wouldn't be a big factor in my decision overall, and even less than usual since you'll be using just a small part well away from either end powering the 901s as mids.

Much bigger fish to fry...

 

[Lombardo]

It wouldn't be a big factor in my decision, even less than usual since you'll be using just a small part well away from either end if powering the 901s as mids.

Just curious though is it better to have a broader range?

Also

how important is Input sensitivity and dampening factor? They seems far apart on those as well.

 

[whoaru99]

Just curious though is it better to have a broader range?

Also

how important is Input sensitivity and dampening factor? They seems far apart on those as well.

I don't care to get wrapped into splitting those hairs. Maybe someone else will care to run down those three or four or five rabbit trails with you.

 

[eiraved]

VS Pioneer Spec 2 (slightly higher asking price) which would you recommend?

I know the Yamaha can be run as monos with 700 wpc if you choose to go in the direction of dual mono amps. I don't know if the Pioneer has that ability. I would go dual mono and really give those 901's a workout.

 

[peterp1]

I know the Spec 2 has been known to underestimate their power and overestimate their harmonic distortion. But besides that how important is frequency response range? Notice the Spec 2 is a much broader range. Is this good or bad? Let me guess. It’s complicated...

Your SX-950 is plenty powerful at 85 wpc. Does it really not go loud enough for you? Unless it doesn't go loud enough, I wouldn't in a million years upgrade to a higher power amp. I never understand the "it never sounds good until you have 200 watts" comments -- unless you are blowing out the windows, 190 of those watts won't be used.

I care a lot about amp sound quality, but I don't even look at power almost at all. My 2-channel system is a 13 wpc tube amp -- it's not a party amp for sure, but it goes loud enough with 90db speakers. My garage system is a 1972 Rotel RX-400, which is only something like 20 wpc (I literally don't know exactly and don't care) and it will go much louder than I ever listen to it. I always just tilt my head sideways when I hear comments about needing 250 wpc -- unless you are running something crazy inefficient like electrostatics. I've not heard that the 901's are that inefficient, but I haven't owned them, so maybe I'm wrong.

Regarding amp specs, my experience is that they are practically useless for evaluating sound quality. Power output is helpful of course, but frequency response beyond 20hz to 20khz isn't going to make a difference because speakers can't produce frequencies outside that range and humans can't hear them. Tenths of a percent difference in distortion doesn't make any difference, and the sine waves they use to test distortion are practically useless compared to the extremely complex signals that are processed in music. Passing a THD test is like naming the first animal in the cognitive test with all but one of the letters filled in. Things like slew rate and damping might have the potential to give some insight into how the amp reproduces real music, but I don't know of any magic formula you can plug specs into to determine sound quality.

The best way to find out is from people's listening experiences with specific amps. The old Pioneers, like your SX-950 sound great. Some would argue that vintage Marantz from the same period as your SX-950 don't sound as good as the Pioneers, even though the Marantz look cool and sell for a lot. I bought my Rotel RX-400 because it shares the same amp design as the Harmon Kardon 330, which is universally admired for sound quality even though it is an inexpensive, low-power amp -- the cap-coupled output is part of its secret sauce makes it more tube like (but you won't see that in any spec). I think you'd be hard-pressed to do better than the SX-950 unless it just isn't loud enough. The 901's have frequency range limits because of non-pliable physics -- that's a genuine problem -- I would just focus on those with Sub/EQ/tweeter.

 

[whoaru99]

Your SX-950 is plenty powerful at 85 wpc. Does it really not go loud enough for you? Unless it doesn't go loud enough, I wouldn't in a million years upgrade to a higher power amp. I never understand the "it never sounds good until you have 200 watts" comments -- unless you are blowing out the windows, 190 of those watts won't be used.

I care a lot about amp sound quality, but I don't even look at power almost at all. My 2-channel system is a 13 wpc tube amp -- it's not a party amp for sure, but it goes loud enough with 90db speakers. My garage system is a 1972 Rotel RX-400, which is only something like 20 wpc (I literally don't know exactly and don't care) and it will go much louder than I ever listen to it. I always just tilt my head sideways when I hear comments about needing 250 wpc -- unless you are running something crazy inefficient like electrostatics. I've not heard that the 901's are that inefficient, but I haven't owned them, so maybe I'm wrong.

Not long after I got them, I did a quick test with my 901s where measured 80-85dB(a) at ~13ft on axis (using trusty old Rat Shack SPL meter) and the power amp meters were peaking up around 100W. Well beyond library levels for sure, but by no means ear bleeding or blowing out the windows (IMO). 2-3 more decibels and 200W is all used up. That was in about 22 x 24 room.

And, yes, a lot of the time it won't even be that loud but when people say the 901s are power hungry, they are. I think it's not necessarily being insensitive, but with so much boost on the low end frequencies it really peaks up the power demand. Running them as midrange cabinets could help that a fair bit if the crossover is high enough.

 

[peterp1]

Not long after I got them, I did a quick test with my 901s where measured 80-85dB(a) at ~13ft on axis (using trusty old Rat Shack SPL meter) and the power amp meters were peaking up around 100W. Well beyond library levels for sure, but by no means ear bleeding or blowing out the windows (IMO). 2-3 more decibels and 200W is all used up. That was in about 22 x 24 room.

And, yes, a lot of the time it won't even be that loud but when people say the 901s are power hungry, they are. I think it's not necessarily being insensitive, but with so much boost on the low end frequencies it really peaks up the power demand. Running them as midrange cabinets could help that a fair bit if the crossover is high enough.

The original Bose 550 receiver made for the 901's with built-in EQ was only 40 wpc, so it doesn't seem like they could be insane power hogs. I suspect something was wrong to have that low volume at that power level, but you might be right that it's working to boost low-end excessively. That excess power for bass overboost shouldn't be necessary for the OP because the powered sub will handle the low frequencies and the 901's no longer need to be over-EQ'ed in the bass region as they would need to be without the sub.

 

[motorstereo]

Something you may want to take into consideration is there's no protection relay on that old Yamaha; I'd be looking for something else rather than putting all those drivers at risk.

 

[whoaru99]

The original Bose 550 receiver made for the 901's with built-in EQ was only 40 wpc, so it doesn't seem like they could be insane power hogs. I suspect something was wrong to have that low volume at that power level, but you might be right that it's working to boost low-end excessively.

There isn't any technical problems with the gear. Big bass boost is inherent to the 901 EQ. Different versions have slightly different curves but all characterized by double-digit dB boost at the low end and high end. 15-18dB bass boost really sucks up the power, the bass tone control on a typical stereo is a "mere" 10-12dB maxed out.

Started the 901s on a HK PM650 thinking pretty much the same thing. But crankin' it up a bit in the garage quickly revealed not enough in that use case. The P-2200 sufficies most of the time. If I need more than what the P-2200 and 901s can dish it's probably time to break out the bigger rig anyway.

 

[whoaru99]

Something you may want to take into consideration is there's no protection relay on that old Yamaha...

Yup.