AR 90 first time listen and amplifier pairing question

[uarnutz]

I just did my first audition of my AR 90s. I redid all the foam surrounds as soon as I bought them since they were totally disintegrated. Good news, all the drivers are working and they sound good.  I am driving them with a Yamaha a/s 500 rated at 85wpc 8ohms. I can get decent sound level but bass is weak compared even to my AR2ax.  Also, upper mid seems dominant and somewhat harsh. I attenuated the UMR one step down and it seems more balanced that way. I am pretty sure that I am not hearing anywhere near their potential with this amp. I have a 2600 cu. ft space on a concrete slab subfloor with cinderblock walls and probably 1/3 of the perimeter is glass.  After much research, I have narrowed down my amp choices to vintage NAD 2200/2400 or Adcom GFA 545/5400.  It seems that I can pick these up for around $250 which, with a decent preamp, falls within my budget. I would be interested in opinions on suitability of these for the AR 90s. Of course, I am open to other suggestions. The NAD preamps also look attractive since they have decent phono quality which is a requirement for me since a I have a large vinyl collection. For this reason, I am also considering an Apt Holman preamp.

[Aadams]

1 hour ago, uarnutz said:

I can get decent sound level but bass is weak compared even to my AR2ax.

You sure you have everything wired in phase? Inside and out? The 90 is very close to a 9. 

[uarnutz]

I was very careful to label all the terminal wires. Will check again. You think the amp is adequate?

[briodo]

You mention refoaming, but nothing on capacitor replacement.  This issue is what my AR9's had before I replaced the capacitors.  Essentially night and day in sound performance. 

Amp is not enough to blow the windows out, but should give you reasonable sound at low volumes.  i would check the caps have been replaced and wiring is correct before changing amp.

Edited January 11 by briodo
typo

[Stimpy]

9 hours ago, briodo said:

You mention refoaming, but nothing on capacitor replacement.  This issue is what my AR9's had before I replaced the capacitors.  Essentially night and day in sound performance. 

Amp is not enough to blow the windows out, but should give you reasonable sound at low volumes.  i would check the caps have been replaced and wiring is correct before changing amp.

I totally agree.  New caps made a world of difference on my 90s.

Also, to the OP, double-check the wiring.  My woofers were wired wrong, from the factory.  At least I think so?  My AVR reported the speakers as being out of phase, and having it correct phase, restored my bass!

As to amps, I use an Adcom GFA-5400.  It works great on the speakers.  Warm and spacious.  The 5400 provides over 200wpc into the 90's impedance load.  Plenty for me!

 

[Stimpy]

[lance G]

I think the following applies to your amplifier ? It may be of some relevance to your perceived issue ?

IMPEDANCE SELECTOR switch
Do not change the IMPEDANCE SELECTOR switch
while the power of this unit is turned on, as doing so may
damage the unit.
If the unit fails to turn on, the IMPEDANCE SELECTOR
switch may not be fully slid to either position. If this is the
case, remove the power cable and slide the switch all the
way to either position.
Select the switch position (LOW or HIGH) according to
the impedance of the speakers in your system.
Rear panel

CAUTION
Switch
position Impedance level
HIGH
• If you use one set (A or B), the impedance of
each speaker must be 6 Ω or higher.
• If you use two sets (A and simultaneously,
the impedance of each speaker must be 12 Ω
or higher.
• If you make bi-wire connections, the
impedance of each speaker must be 6 Ω or
higher. See page 6 for details.
LOW
• If you use one set (A or B), the impedance of
each speaker must be 4 Ω or higher.
• If you use two sets (A and simultaneously,
the impedance of each speaker must be 8 Ω or
higher.
• If you make bi-wire connections, the
impedance of each speaker must be 4 Ω or
higher. See page 6 for details

[Stimpy]

Hope this works.  A very detailed wiring diagram of the AR90 crossover boards.  Download from the linked thread. Thanks to DavidR for posting it.:

 

AR90 Wiring Diagram pdf

[Stimpy]

With Yamaha amps, changing the Impedance Selector switch from High to Low, limits current delivery into the low impedance load.  This switch is a protection device for the amp, and does not improve performance, switching to the Low setting.  Sound quality will suffer in the Low setting.  Good judgement, careful use of the volume control, and the Impedance Selector set to High, is your best bet.

[DavidR]

On the AR90 the tweeter/UMR and LMR are wired out-of-phase and the woofers are wired in-phase unlike the AR9 where all drivers are wired in-phase.

You will notice in the wiring schematic all the plus (+) side of those drivers go to the negative (-) speaker binding post (but not the woofers).

My recap also improved SQ and really brought out the LMR.

Many of my caps measured within the 10% variance BUT were acting as a resistor. My upper mid and tweeter were totally muted. IMO, there is no need to use the more expensive film caps. Today's non-polar (NPE) are much better than the originals and the speakers 'behave' as intended and sound more authentic. I did, however, add a small film bypass (0.01uf) capacitor in parallel to all series caps.

[uarnutz]

Wow. A wealth of very good information here. Thanks everyone.

[uarnutz]

Aaah. That's more like it. I started with the polarity at the speaker terminals and the amplifier.  Speaker terminals were in phase but, polarity was reversed from amp.  So, I reversed the speaker terminals. Shazam! I now have bass to shake the walls. I next reset the impedance on my amp to the Hi setting.  Not sure how much difference that made but, it all seems fine. In terms of internal polarity. I could use a little clarification.  For the 10 inch speakers, I should go with the color coding on the schematics and assume they are wired correctly from the board?  Also, the woofer terminals are not clearly marked for polarity. I assumed that the red dot on the label was positive. Is that correct?

[uarnutz]

1 hour ago, DavidR said:

On the AR90 the tweeter/UMR and LMR are wired out-of-phase from the woofers unlike the AR9 where all drivers are wired in-phase.

You will notice in the wiring schematic all the plus (+) side of the drivers go to the negative (-) speaker binding post.

My recap also improved SQ and really brought out the LMR.

So, is the out of phase wiring by design? If so, what is the effect of putting them all in phase? Is that a common "fix"?

[uarnutz]

3 hours ago, Stimpy said:

I totally agree.  New caps made a world of difference on my 90s.

Also, to the OP, double-check the wiring.  My woofers were wired wrong, from the factory.  At least I think so?  My AVR reported the speakers as being out of phase, and having it correct phase, restored my bass!

As to amps, I use an Adcom GFA-5400.  It works great on the speakers.  Warm and spacious.  The 5400 provides over 200wpc into the 90's impedance load.  Plenty for me!

 

Thanks. A recap is in the plan but, I tend to follow a step-wise approach in my restorations. I find it is more fruitful to control the variables. When you say that your speakers were wired wrong from the factory, that was based on the DSP test alone, not a trace of the wires against the schematic, right? The DSP reverses phase for you?

[Stimpy]

13 minutes ago, uarnutz said:

Thanks. A recap is in the plan but, I tend to follow a step-wise approach in my restorations. I find it is more fruitful to control the variables. When you say that your speakers were wired wrong from the factory, that was based on the DSP test alone, not a trace of the wires against the schematic, right? The DSP reverses phase for you?

Yes, DSP test tones, from YPAO in my Yamaha RX-A3030 AVR.  Once completed, bass much better. 

I've never traced the actual wiring, but I do plan to do so.  I've been using AR-58S speakers, and new to me Martin Logan ElectroMotion ESL's, so my 90s haven't been used lately.  A shame too, as they're fine speakers.

Oh, the Red Dot is positive...!   

[DavidR]

6 hours ago, uarnutz said:

So, is the out of phase wiring by design? If so, what is the effect of putting them all in phase? Is that a common "fix"?

It is obviously by design. That is how the AR engineers made the crossover.

You'd have to ask the AR engineers about changing the phase and its effect on SQ.

"Common fix" > not a 'fix' if you change what they did. If you want to wire it like an AR9 then reverse the wires on the tweeter, UMR and LMR. But why do it? They did it for a reason.

[ar_pro]

1 hour ago, DavidR said:

It is obviously by design. That is how the AR engineers made the crossover.

You'd have to ask the AR engineers about changing the phase and its effect on SQ.

"Common fix" > not a 'fix' if you change what they did. If you want to wire it like an AR9 then reverse the wires on the tweeter, UMR and LMR. But why do it? They did it for a reason.

Whenever this anomoly has come up in discussion, I've always wondered about the "how come?".

I once owned a pair of unmolested AR-90 systems, and they were in such good original condition, that there was no need to open them up. This was in the '90s, before this board really got started, and there was very little reliable info available online - that reversed phase issue would have driven me nuts. 

[DavidR]

33 minutes ago, ar_pro said:

that reversed phase issue would have driven me nuts

The crossover schematic(s) matches what is in my (early; s/n around 1500) AR90s. I do not believe this is a mistake.

For example, on the tweeter, the blue wire (neg) goes to the series capacitors (the 4 and 6); the yellow wire (positive) goes to ground/negative - exactly as shown.

I bought them from VintageAR.

I have Ken Kantor's email addy, perhaps I will see if he has any knowledge on this. He was a young engineer at AR at the time.

I took a pair of cheap Yamaha speakers and only re-used the woofer. It had a single cap but was a three way design. I modded it and bought a better mid and tweeter and made a 'crude' wiring crossover. I wired all in-phase. It didn't sound right. Don't know what made me try this but I ended up wiring the tweeter out-of-phase. It then sound 'right' and has stayed this way.

[uarnutz]

OK. I accept that the polarity difference between the two systems is by design.  It seems to be well understood by speaker designers that reversing polarity between drivers can overcome some "bad" effects of certain crossover designs.  Still, it is harder to  understand  why there would be a different approach to polarity between these two systems that appear identical except for the size of the woofers.  I know this is off topic for the thread;  just wondering.

[DavidR]

When polarity is different the drivers move in and out opposite to each other. Sound would arrive at a slightly delayed time for those drivers not in phase. Perhaps the smaller woofers of the 90 were 'drowned out' with all drivers in-phase. By having the upper 3 drivers delivering sound with that slight delay the bass would appear stronger; and remember the longer waves move slower. Just a guess as to why.

[AR surround]

11 hours ago, uarnutz said:

OK. I accept that the polarity difference between the two systems is by design.  It seems to be well understood by speaker designers that reversing polarity between drivers can overcome some "bad" effects of certain crossover designs.  Still, it is harder to  understand  why there would be a different approach to polarity between these two systems that appear identical except for the size of the woofers.  I know this is off topic for the thread;  just wondering.

 

9 hours ago, DavidR said:

When polarity is different the drivers move in and out opposite to each other. Sound would arrive at a slightly delayed time for those drivers not in phase. Perhaps the smaller woofers of the 90 were 'drowned out' with all drivers in-phase. By having the upper 3 drivers delivering sound with that slight delay the bass would appear stronger; and remember the longer waves move slower. Just a guess as to why.

I would surmise that speakers with drivers out of phase to each other isn't all that uncommon.  In the Audyssey (room correction software) manual, they specifically note this condition and state that Audyssey will pick up the out of phase condition; and that it should be ignored.

 

 

[uarnutz]

Ok. Back to basics. I got around to checking all the polarity of the speakers that I just reinstalled. Sure enough, one of the 10 inch speakers had its connections reversed. All back together and what a difference!. The tympani and bass drum come through loud and clear now. Maybe I will have to keep these after all. Thanks for all the sound advice. Researching 3rd order crossovers and polarity anomalies, just because.

[Stimpy]

8 hours ago, uarnutz said:

Ok. Back to basics. I got around to checking all the polarity of the speakers that I just reinstalled. Sure enough, one of the 10 inch speakers had its connections reversed. All back together and what a difference!. The tympani and bass drum come through loud and clear now. Maybe I will have to keep these after all. Thanks for all the sound advice. Researching 3rd order crossovers and polarity anomalies, just because.

Awesome, glad they were miswired...!  

Also, the tweeter circuit is 3rd order, with 18db slopes.  I believe everything else was 2nd order. Not that that clarifies much.  

I posted a few years back concerning the woofer phasing on the 90s, and why they differed from the 9s.  No one knew why the 2 weren't matched?  Still strikes me as strange.  Maybe I should rewire my 90s and see (hear) what happens?  

[DavidR]

The wiring schematic for the 9 and 90 show both their woofers are in-phase and are in parallel to each other. So no difference.

The 90 has a smaller shunt cap and has a zobel circuit whereas the 9 has the 2500uF 'tank' circuit.

[johnfalc]

DavidR - not according to my experience nor the factory schematic.  Here, in our library is this:

AR-90 Schematic | The Classic Speaker Pages (woofers out of phase with remainder)

whereas the AR-9 schematic shows:

AR-9 Schematic | The Classic Speaker Pages (woofers in phase with remainder)