Can I use Sansui AU-717 and Sansui AU-X901 for bi-amping?

jameswei

Super Member
I got so many Sansui amps now that I think is a waste letting sit idle, so I have a KEF 105/3 speaker that I am thinking about bi-amping. So if I use the AU-717 to run the top part of the speaker and use the AU-X901 to run the bottom half, how would I do that? I am guessing using the pre-out of the AU-717 connect to the power amp direct of the AU-X901. Is this correct?
 
Let me rephrase the question, do I use the pre-out or the pre-in if I want to bi-amp my speakers? Can anyone help?
 
I am guessing using the pre-out of the AU-717
Yes, however I am not familiar with the input options on the AU-X901, I think you should also set the pre/power rear panel switch on the AU-717 to 'connected - capacitor coupled'.

Remember to connect up the gear with the POWER OFF, turn the volume controls to zero or very low, and tread carefully.
 
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This is the back of the 901 and in the top middle there's the (power amp direct) I am thinking I should use that to connect to the Pre-out of the 717 and yes I will power off everything when I am connecting, I learned my lesson the hard way. Thanks Hyperion:thumbsup:
 
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So I should use the Pre out not the power amp in and do the connected and capacitor coupled? correct?
 
I connect everything accordingly but couldn't get sound out of the left channel so I try connecting to ( CD) on the 901 instead of (power amp direct) and it worked, so I am going to leave it at that for now.
 
I connect everything accordingly but couldn't get sound out of the left channel so I try connecting to ( CD) on the 901 instead of (power amp direct) and it worked, so I am going to leave it at that for now.

Connecting the 717 pre out to the 901 CD (or whatever, except phono or power amp direct) is probably the better way to go. That way, you can be sure to balance the levels of mid/high to lows by using the separate volume controls on each amp. If you use the power amp direct on the 901, you are at the mercy of whether or not the two amps have same/similar gain. Using the other type of input gives you more control over that.
 
Maybe a stupid question but I'll ask it anyway; is there a way to use the X901 as pre-amp only in the absence of a pre-outs?
I just cannot understand why a newer amp does not have this option compared to other similar line older Sansui integrateds.
 
Using the AU-717 and AU-X901 for bi amping didn't sound too good , especially you have two different volume control to mess with, so I end up just using the AU-717 only but did a bi-wiring. I think either its just imagination or the idea of extra wires but I felt the bi-wiring sounded even better. However, tragedy struck yesterday. After a full day of playing Saturday, I turn on the AU-717 on Sunday morning and discover that the right channel was out, so out it goes to my tech this morning.
 
To answer jojo0416's question, from my point of view, the pre-amp section of the AU-717 is the better of the two, so its not worth the effort the other way around.
 
you are probably sending full-range power through two different amps to both
the high-side (tweeter section) and the low-side (bass section). each section
has to deal with the frequency ranges it wasn't designed for. workable, though
as you did try it.

using a crossover means each section gets only the frequencies you dial in
(with allowances for the design of the respective sections of the KEF), you
can then boost one relative to the other (frequency and volume). Your KEFs
will sound better.

worthwhile to continue trying.
 
To answer jojo0416's question, from my point of view, the pre-amp section of the AU-717 is the better of the two, so its not worth the effort the other way around.

That's a very interesting observation James... as it's hard to say exactly how the preamp section of the 901 sounds given that we can't separate the preamp and power amp sections and listen to the preamp individually, and compare it to directly to other preamps.

That said, I'm assuming you prefer the preamp section of the 717 as you've used it to drive the power amp direct inputs on the 901, and prefer the warmer sound that this delivers versus the 901 in its original pre/power amp configuration??
 
you are probably sending full-range power through two different amps to both
the high-side (tweeter section) and the low-side (bass section). each section
has to deal with the frequency ranges it wasn't designed for. workable, though
as you did try it.

The two sections of the speaker don't do anything differently when fed full range signals from two different amps than they do when fed a full range signal from one amp with the sections strapped together. Simply removing the jumper straps doesn't alter the high pass going to the tweeter not the low pass going to the woofer.

Of course, when using two separate amps one has to be sure things are connected in proper polarity, and difference in levels certainly can alter the tonality - but those are different matters.
 
the OP says it didn't sound too good. the two sections when split apart is tweeter only, and bass only.
not quite the same as having the speaker cross over route the signal so that only the highs
go to the tweeter and no lows, with the bass section getting only the low freq signals and no
highs.

so the tweeter gets full range, and perhaps the excessive bass energy at below the intended cross
over frequency for the tweeter interferes with the sound.

if it were the case that you can feed full range to tweeters and full range to bass units and have good-to-great
sound then there would be no need for crossovers inside speakers.

having used crossovers for a long time (see my upgrading the dahlquist DQ-LP1 thread), with a cross
over, the treble monitors sound better handling only the treble, and the bass sounds better handling
only the bass. both are somewhat full-range but it was clear to me that having two speakers
optimized for their ranges without trying to handle all the frequencies makes sense in practice.

so, for example, if you have a small monitor like a NHT zero, and a bass speaker like a
subwoofer, you're not asking the NHT to handle 20-100Hz bass notes, and you're not
dumping high frequency into the subwoofer.

I came to this conclusion after listening to the uber expensive speakers in the days I
tracked the stuff but couldn't afford the 5K+ speakers from Infinity, and tried lots of
intermediate speakers, like timewindows, DQ-10s, early magnepans, etc. Also
heard Quads, Linns, shahinians, etc.

full range didn't do it for me.

However, if you've tried this parallel amp to separated sections and it has worked
for you (unlike the OP), then I'd like to hear from you how you did it and with
what speakers. I would consider giving up my system since it is unwieldy at
times and old enough to have occasional age problems (hence the upgrading
of Haflers and Dahlquists and lots of other components).
 
the OP says it didn't sound too good. the two sections when split apart is tweeter only, and bass only.
not quite the same as having the speaker cross over route the signal so that only the highs
go to the tweeter and no lows, with the bass section getting only the low freq signals and no
highs.

so the tweeter gets full range, and perhaps the excessive bass energy at below the intended cross
over frequency for the tweeter interferes with the sound.

What you're saying is only correct in the case of active bi-amping, where the internal crossover in the speaker is removed entirely, and an external crossover is used.

I think it's fair to assume that James is experimenting with the easiest option, which is to remove the bridging connections between the biwireable speaker binding posts, and simply connecting one amp to the woofer connections, and the other amp to the mid and tweeter connections. With a passive bi-amping setup such as this, the internal crossover is still in place, so there's no risk of the wrong frequencies being reproduced by the wrong driver (ie. they are not running full-range)

This is the speaker in question:

20151159.jpg



If James has indeed removed the crossovers and is powering each driver directly from each amp (without an external active crossover to divide the signal between each amp), then your statements hold true. I doubt this is the case though.
 
according to the label in your picture, the upper posts are MF/HF and the lower ones are
LF so how is the cross over still in place (main question of my input in this thread).

the rationale is that the speaker cross over that's inside is moved outside for an active crossover
so at the tweeter the full-range signal is filtered to pass only the high, and conversely, the cross
over with filters sends only low frequencies so that the bass unit sees only the low frequencies.

again, if the label is true, you are sending full-range to what the label says should be
MF/HF and you are also sending full-range to LF.

if both set of posts are still connected to a full crossover, then what's the point of
having a cross over, and specifically, having the labels split the highs and lows.

it would make more sense that if the cross over is still in place, and the labels being incorrect,
then it is a bi-wire system.

are we armchairing this or am I asking the wrong questions. the OP tried this and it didn't
sound good, I have tried lots of speakers and came to the active crossover as a solution.

if the crossover is still in place, putting a mini-monitor on the LF side, and a subwoofer
on the MF/HF side would sound the same as if it were (properly) reversed. and this is
without the links to combine the crossover. and therefore the question is, is if the
crossover is intact with or without the links, then why are the links there.

I have two sets of speakers, two sets of stands, a crossover, a signal switcher, a
pair of power amps, and four ugly speaker cables. If I could simplify this I would.

I would like to hear from people who have taken a speaker with two sets of inputs
(not bi-wire) and have not used an active crossover to split the sounds using
only the speaker's internal crossover.

IOW you may think I'm wrong, but please refer to what you've tried, not what you think is
happening, so I can fix my problem.
 
the OP says it didn't sound too good. the two sections when split apart is tweeter only, and bass only.
not quite the same as having the speaker cross over route the signal so that only the highs
go to the tweeter and no lows, with the bass section getting only the low freq signals and no
highs.

so the tweeter gets full range, and perhaps the excessive bass energy at below the intended cross
over frequency for the tweeter interferes with the sound.

if it were the case that you can feed full range to tweeters and full range to bass units and have good-to-great
sound then there would be no need for crossovers inside speakers.

Removing the jumper straps does nothing to change what gets to the tweeter or what gets to the woofer.

All the jumper straps do is provide external parallel connection of the speaker's internal low pass filter (LPF) and high pass filter (HPF). Removing the jumpers is not removing nor disabling the crossover, removing the jumpers merely separates the crossover HPF from the LPF.

Conventional.png

Biamp.png
 
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@pete_mac

in almost all crossover-based dual speaker systems I have listened to or used, the speaker's
internal crossover is not replaced or bypassed. it is still needed because the crossover
arbitrarily sets the external cross over frequency and the high-side speaker doesn't
see frequencies above this even though it can potentially handle frequencies below
this externally-set filtered signal. similarly, the bass speaker can certainly handle the
highs but doesn't for the same reason.

HP of TAS, when he built the QRS/1D took two full-range speakers, added a crossover,
sent highs to one and the lows to the other. I do not recall whether he eliminated the
crossovers.

crossovers do not, as a rule, simply set a frequency whether they are in speakers or
as an active device. they can tailor the sound.

see the 11ohm and the 15om versions of the LS3/5a for why they are so complicated
in their crossover designs.

in the picture of the KEF 105, the internal portions of the respective crossover sections
are not bypassed, they are intact, and in place and signals are still processed by
the internal sections of the crossover.

I will admit that I did look at speakers that had the capacity for really full range
like the original Ohm F and perhaps, current designs in OB that may or may not
have crossovers.
 
Removing the jumper straps does nothing to change what gets to the tweeter or what gets to the woofer.

All the jumper straps do is provide external parallel connection of the speaker's internal low pass filter (LPF) and high pass filter (HPF). Removing the jumpers is not removing nor disabling the crossover, removing the jumpers merely separates the crossover HPF from the LPF.

you're confirming what I'm trying to say, which is not that the crossovers are being removed, but you
are still sending a full-range signal to both the High side and the low side.

and the point is not that it does nothing to what gets to the tweeter and what gets to the woofer BUT that
a full-range signal goes to both.

in my opinion, using crossovers for a long time, its that a full-range signal to a monitor (or a crossover supported tweeter
from a speaker that can separate its internal crossover into high and low section) and the same full range
signal to a bass/woofer speaker (with its still connected crossover but with or without its high section disabled
or bypassed) is not the same as a filtered treble signal to tweeter sections and a filtered bass signal to
a bass section.

the OP said it didn't sound right.

Again I'm looking for a solution based on someone who did some work looking into this.

I would go out and buy a KEF 105 if this worked.

so PLEASE, if you have tried this and it worked PLEASE give me the details. we are now down
to which angels on that pin head are left-handed versus wearing red shoes.
 
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