Pr of HK Cit22s in bridged mono to drive AR9s?

Hi everyone,

If someone can give me some advice on my power amp/speaker problem, I'd sure appreciate it.

I'm on a very tight budget and want to drive a pair of vintage, late 70s AR9s. These are power-hungry 4 - Ohm speakers--very power inefficient beasts.

The spec sheet on the AR9s say that they need a min. 50 watts per channel, but from what I remember about these speakers that that would be WAY underpowering them.

Here's what the spec sheet on the AR9s says:

>>50 watts minimum, per channel, is recommended. 50 watts (into one speaker only) will produce 104dB SPL in a 3000 cu. ft. room of average reflectivity (energy coefficent of 0.15). 100 watts (50 watts into each channel) will produce 107dB in the same room. May be used with amplifiers capable of delivering 400 watts continuous power per channel being driven to clipping 10 percent of the time on normal music source material.<<

I was thinking of using a pair of Harman/Kardon Citation 22 power amps (which can be operated in bridged mono)--until I read in a online Citation 22 user manual that bridged mono should only be used for 8 Ohm loads.

My question is, is a single Citation 22 enough power to drive a pair of AR9s safely to a moderately high volume without danger?

Also, since the manual says bridged mono "should" only be used for 8 - Ohm loads, does that imply that in some cases a 4 - Ohm load is OK? What about in this case?

Should I use one Cit 22 in stereo, or two in bridged mono?

As I said, my budget is tight, I don't have the money for a lot of the nice audiophile gear a lot of you can afford, so I thought the Cit 22 might be a good, low-cost/high power option.

Please help me out here if you can and keep it simple (Low-tech understanding here :-))

Thanks in advance for any help on this.


PS: Here's what the Citation 22 manual says about bridged mono, and the Cit 22 specs are below that:

>>Eight - Ohm Mono Operation

The Citation 22 has exceptional capabilities as a mono amplifier, either in pairs (dual mono) or for use with a single 8 - Ohm subwoofer.

Operation in this mode differs from stereo in four important ways.
1. The Bridged-Mono switch is set to the ON position.
2. The Speaker Operating Mode switch is set to the 4 - Ohm setting (even though mono operation should only be with 8 - 16 Ohm loads).
3. Input signal is received only through the LEFT input socket.

4. The single set of speaker connectors are connected to the LEFT and RIGHT (positive-red) output terminals. In this special case, the LEFT terminal acts as a positive and the RIGHT acts as a ground.

Make sure the Indicator button on the far right amplifier front panel is set to the "4 - Ohm or 8 - Ohm mono" setting.<<

Stereo Power Amplifier (200 watts)


Audio Inputs : 1 stereo pair
Power Output : 200 watts per channel @ 8 ohms
Total Harmonic Distortion : 0.08% @ 8 ohms
0.08% @ 4 ohms
Output 4 Ohms : 200 watts per channel
High Instantaneous Current Capability (HCC) : +/-120 amps
Negative Feedback : 12dB
Frequency Response : 0.1Hz - 250kHz +0/-3dB
Slew Rate : 160 volts/microsecond
Rise Time : 1.4 microseconds
Transient Intermodulation Distortion (TIM) : Unmeasurable
Damping Factor : 120
Signal-to-Noise (dBA) : CD, VIDEO, etc - 123dB
Input Level/Impedance : CD, VIDEO, etc - 1 volt/22k ohms
Power Consumption : 610 watts
In my HT system, i'm using a pair of 9's for my mains and 90's for the rears. The center channel is a custom built piece using identical drivers as found in the 9's & 90's i.e. two of the 8's and the 1.5" dome upper & .75" dome tweeter. All of these have been highly modified i.e. internal wiring has been replaced with Kimber of the Teflon variety, the caps have been upgraded and bypassed, binding posts replaced, cabinets have been thoroughly braced and damped, etc... The sound is FAR more open, spacious, dynamic and transparent to say the least.

I also have a Citation 22 that i purchased for a system that i'm assembling for a friend. Since he is on a phenomenally tight budget, i picked it up very reasonably. It was severely damaged ( shattered circuit board ) but i was able to repair it with some TLC. I'm only including this info so as to give you some background where i'm coming from and that i'm quite familiar with the gear that you are trying to use.

Having said all of that, i would not try to use the HK amps in bridged mode to drive the 9's. As one can see, this amp does not "like" lower impedance loads as evidenced by the same power rating at 8 and 4 ohms. As you've noted, the 4 ohm load that the 9 presents would be seen as a 2 ohm load by the bridged amp. Even if the bridged amp would deal with the low impedances that the 9 presents, it simply isn't enough power to really make these speakers sing. I am talking about the Citation either running in bridged mono mode or just one amp running in stereo. After all, if 400 watts bridged mono per speaker isn't enough, 200 wpc from one stereo amp is surely way short of the mark.

In my experience, you really need at least 600 wpc @ 4 ohms to do these speakers justice. Quite honestly, even more would be better. Given your statements here about the 9's being power hogs, i'm pretty sure that you can understand where i'm coming from. Many other folks may think i'm crazy with the figures i'm mentioning here, but you ( and other owners of 9's and similar speakers ) probably have no problem relating.

The least expensive amp that i've found that will drive these speakers pretty well is the smaller Sunfire amp ( 300 @ 8 / 600 @ 4 ). This amp is pretty conservatively rated as they typically clip at well over 700 wpc @ 4 ohms. That is, if you have enough AC feeding them. This amp did pretty well but was actually running out of steam on very loud passages. Most people would have never noticed or wanted to play this loud, but i do play things that loud and i did notice : ) If you or anyone else decides to go this route, i would suggest having Sunfire perform their "Apogee" modifications ( designed for low impedance / high reactance speakers ) and adding a few large value filter caps for increased power supply reserve. Changing a cap to a higher grade unit in the feedback circuit can also improve this amp quite a bit.

I'm currently using a Sunfire Signature ( rated at 1200 wpc @ 4 ohms, mine actually clips at 1480 wpc ) that has had the "Apogee mod" and increased filter capacitance added. I can now say that i can REALLY drive these speakers with authority and do it cleanly to any volume level that you want. This combo works better than when i was passively bi-amping the 9's with a Perreaux 2150 ( 400 wpc @ 4 ) on top and a Perreaux 3150 ( 500 wpc @ 4 ohms ) on the bottom.

Have you already purchased one or both of the Citation 22's or are you still in the "planning" process ? My next suggestion will hinge on your response to this question. Sean
I agree with Sean. You will blow your citations by driving them with 1/2 the impedance they can handle. The decible gain from 200 watts to 400 watts is only 3db. So, if you try running the 9's with one amp and it doesn't cut it, you probably won't be happy with a measly 3db gain (It takes 10db to double the perceived volume).

My advice is try using a single amp. If that isn't enough, you will need to get your hands on a monster to do the job! Consider selling the pair of amps and spending the money on the biggest adcom you can find if power is what matters. Personally, I would probably be happy with a 60 watt tube amp-it will sound better but have less volume for the same kind of money.
Elevick may be right. A tube amp will tend to fill out the 9's slightly "tight & dry" low Q bass and lend a bit of "liquidity" and "airiness" to the mids and treble that the 9's lack in stock form. Then again, i would shoot for a bigger tube amp than a 60 watter though. After all, we want it to sound "good" AND "loud" : ) Sean

PS... As i've mentioned before, one is always better off with higher sensitivity speakers when possible. So long as you can find something that suits your sonic preferences in a higher sensitivity, you'll be dollars ahead in terms of how much wattage you need. This is not to mention how much wider the selection you'll have when you don't need a kilowatt or two to get the job done. If you are dead set on using the 9's, so be it. Just don't expect to get them to crank or sing without investing a good amount of money into your amplification. On top of that, some personal elbow grease inside the speakers can go a long way too.

PPS... While 200 to 400 watts is only 3 dB's when doing the math, the increased power and "sense of ease" that comes with less stress on the amp can make a big difference in the sonic presentation. Only problem here is that the Citation itself just doesn't want to see that type of a load in bridged mode. Going the passive bi-amp mode may help, but i'm still thinking that it may not be enough. Then again, we might have different tastes, listening habits and expectations : )

The citation 22 can handle difficult loads. It is engineered to give the same power output in 4 and 8 Ohms. By using the speaker impedance switches the amp wil increase (or decrease) the maximum voltage output so the power output will be the same in 4 and 8 ohm. This is done so that 8 ohm speaker owners have the same amount of power as 4 ohm speaker owners. The amp can also handle 2 ohm loads (in the 4 and 8 ohm setting) for a short amount of time. It can't handle continous 4 ohm loads in bridged mono setting. It just isn't designed that way. If you use the amp in stereo mode in the 4 ohm setting there shouldn't be a problem.
I don't know if 200 watts rms is enough for your speakers. I think it should be, but I don't know them, so no statement on that one......