AR9 bi-amping

[Guest dogmeninreno]

I have a set of Vintage AR9's and am using them as mains in my HT system.

They are being driven by two Adcom GFA-555II power amps and a GTP-750 preamp/tuner combo.

I am currently using one 555II for left and one for right channel driving the woofers from one channel and the uppers from the other channel on each amp (Vertical bi-amping each speaker with individual amps).

I am really pleased with this combo and like the 8 ohm load to the Adcoms but would I be better off to take one of the Adcoms and bridge it to feed the woofers from the subwoofer output on the GTP-750 (since it does not have 2 sets of main outputs) and use the other 555II to drive the L&R uppers?

This would allow me to raise the bass output at lower levels.

I am currently letting the preamp put out full frequency and letting the AR9 deal with it thru the xovers. The GTP-750 puts out full range thru the subwoofer output. This would also give me remote access thru the GTP's remote control for sub volume at low listening levels.

Any comments would be appreciated.

Dale in Reno.....

[Guest Bret]

>I am really pleased with this combo and like the 8 ohm load to the Adcoms but would I be better off to take one of the Adcoms and bridge it to feed the woofers from the subwoofer output on the GTP-750 (since it does not have 2 sets of main outputs) and use the other 555II to drive the L&R uppers?<

Dale,

I haven't quite gotten the hang of this, yet, but I am told that the upper cabinet on an AR-9 is 4 ohms and the lower cabinet is 4 ohms and that "strapped" together they are still 4 ohms.

The only way I can see that this would be true is if the impedance to the amplifier is frequency specific; that is to say, if the bottoms are 4-ohms to 200Hz and the top cabinets are 4 ohms from 201Hz+ (of course allowing for the crossover rolloff, I'm not being literal).

That way if you stuck an amp on the bottom it sees 4 ohms, if you stick an amp on the top it sees 4 ohms and if you stick an amp across both top and bottom it still sees 4 ohms. That's all I can figure.

Bottom line? It might be a very, very bad idea to bridge the 555MkIIs mono as they will sometimes see impedances below 2 ohms.

I've been told many times that the 4-ohm top/bottom thing is true even if my explanation of it is completely wrong.

Bret

[rrcrain]

The secret to the impedance puzzle is this. The bass drivers are connected directly to the amp, but the rest of the drivers are behind a constand impedance network.

Given the reputation the AR9 has for bass reproduction, I do question the need for a subwoofer.

[Guest Nigel]

Dale;

Leave them the way you have them. I now have mine similarily wired (but with different amps) and found that no other hook-up scheme worked as well, let alone better.

[ar_pro]

Your set-up is fine the way it is, Dale - a bridged 555 has a higher level of noise & hum than the two-channel configuration. If you're interested in fine tuning the 9's bass, consider Adcom's passive line controller as a replacement for the GTP-750, feeding a high-quality LF equalizer (Audio Control's "Richter Scale" and "Octave" equalizers come to mind) for your bass channels, while leaving the midrange and tweeter uneffected. Some of the best depth & imaging that I've heard through 9's was with this set-up...powerful bass, too.

[Guest dogmeninreno]

Well, with all your good advice, I reconnected my GFA-555II's to now feed the woofers on two channels individually from the 2 L&R subwoofer outputs (full range but with gain control) on the GTP 750 and connected the uppers to the ramaining channels. I recall reading a post here that when you vertical bi-amp the 9's, the resulting impedence is 8 ohms top and 8 ohms bottom? Did I miss read? Not important since I now have seperate control of the woofers using the subwoofer control on the remote??? Thanks, Dale

[Guest Bret]

> I recall reading a post here that when you vertical bi-amp the 9's, the resulting impedence is 8 ohms top and 8 ohms bottom? Did I miss read?<

That was probably me saying something completely wrong and was toasty after Nigel's reply. Not Flamekist, but warm.

So if it was me you remember reading, you have learned a valuable lesson (as I did), I should never assume anything but especially not anything dealing with electricity.

Bret

[Guest Barrydor]

>I haven't quite gotten the hang of this, yet, but I am told

>that the upper cabinet on an AR-9 is 4 ohms and the lower

>cabinet is 4 ohms and that "strapped" together they are still

>4 ohms.

>

>The only way I can see that this would be true is if the

>impedance to the amplifier is frequency specific; that is to

>say, if the bottoms are 4-ohms to 200Hz and the top cabinets

>are 4 ohms from 201Hz+ (of course allowing for the crossover

>rolloff, I'm not being literal).

>

>That way if you stuck an amp on the bottom it sees 4 ohms, if

>you stick an amp on the top it sees 4 ohms and if you stick an

>amp across both top and bottom it still sees 4 ohms. That's

>all I can figure.

>

>I've been told many times that the 4-ohm top/bottom thing is

>true even if my explanation of it is completely wrong.

>

Your explanation is absolutely correct

Barrydor

[Guest dogmeninreno]

>> I recall reading a post here that when you vertical bi-amp

>the 9's, the resulting impedence is 8 ohms top and 8 ohms

>bottom? Did I miss read?<

>

>That was probably me saying something completely wrong and was

>toasty after Nigel's reply. Not Flamekist, but warm.

>

>So if it was me you remember reading, you have learned a

>valuable lesson (as I did), I should never assume anything but

>especially not anything dealing with electricity.

>

>Bret

Well Bret, It does give me control over the woofers at all volumes. I do not see why this is not the best of both without any problems, 4 ohms or not? Dale

[Guest Bret]

>I do not see why this is not the best of both without any problems, 4 ohms or not?<

It's great. Just don't bridge the 555MKIIs. That was my only point.

Bret

[Guest Bret]

>Your explanation is absolutely correct<

Well, it's good to know I haven't gotten too old to be educated.

Bret

[Guest dogmeninreno]

>>I do not see why this is not the best of both without any

>problems, 4 ohms or not?<

>

>It's great. Just don't bridge the 555MKIIs. That was my only

>point.

>

>Bret

Thanks Bret, I think this will do fine and thanks you all for your input and suggestions! Dale in Reno.....

[Guest coppertop]

>>I do not see why this is not the best of both without any

>problems, 4 ohms or not?<

>

>It's great. Just don't bridge the 555MKIIs. That was my only

>point.

>

>Bret

HELLO! I am a young AR lover who is new here. You seem to know so much. What about using 3 amplifiers on the Acoustic Research 9 speakers that are my new gift. Would that work better than 2? What about using one amplifier for each woffer?

- Coppy

[Guest dogmeninreno]

>>>I do not see why this is not the best of both without any

>>problems, 4 ohms or not?<

>>

>>It's great. Just don't bridge the 555MKIIs. That was my

>only

>>point.

>>

>>Bret

>

>HELLO! I am a young AR lover who is new here. You seem to

>know so much. What about using 3 amplifiers on the Acoustic

>Research 9 speakers that are my new gift. Would that work

>better than 2? What about using one amplifier for each

>woffer?

>

>- Coppy

I am not sure what you would gain with 3 amps? I am assuming that each has 2 channels which would give you 6 in/outputs and assuming you are not bridging two of the amps for the woofers for extra output (or two are monoblocks), I don't see what the point would be (unless I misunderstood the ?) Dale

[Guest coppertop]

>>HELLO! I am a young AR lover who is new here. You seem to

>>know so much. What about using 3 amplifiers on the Acoustic

>>Research 9 speakers that are my new gift. Would that work

>>better than 2? What about using one amplifier for each

>>woffer?

>>

>>- Coppy

>

>I am not sure what you would gain with 3 amps? I am assuming

>that each has 2 channels which would give you 6 in/outputs and

>assuming you are not bridging two of the amps for the woofers

>for extra output (or two are monoblocks), I don't see what the

>point would be (unless I misunderstood the ?) Dale

Hello Kitty! Help me out here, guys. I'm as lost as Little Red Riding Hood. Three amplifiers should be better than two. More power, right? That's what my brother used to tell me. (Wish I could ask >him

[ToastedAlmond]

I have finally found a bi-amp combo for the AR-9's that I can live with. I'm driving the woofers with a Onkyo M-5090, 200wpc pwr amp, and the lower/upper mids and tweets with a Carver TFM-35, 250wpc power amp. The Carver has recently replaced a Onkyo M-504, 165wpc amp. The M-504 was competent, but the Carver appears to be just a bit sweeter. The M-5090 is about an 80lb. beast and it does a wonderful job of driving the woofers. No idea what it's doing into 4/2 ohms with those woofers, cause it's hard to find info on it, other than that it cost $2K back in 1983. If I could find/afford the REAL BIG Onkyo, the $4,000, 300wpc job from the 80's, I'd drive them with that!

Preamp is a Apt "Holman".

[Guest Bret]

>Three amplifiers should be better than two. More power, right? That's what my brother used to tell me.<

As with everything there is a point of diminishing returns. Generally speaking, it is recommended that you drive speakers with the same amplifier top and bottom. Failing that, you'd want to drive them with the largest amplifier on the woofers. I wouldn't think you'd ever want the amps to be too different, say 350w/channel on the bottom and 25w/channel on the top.

There seems to be a concensus opinion that bi-amping cleans things up. The story goes that this keeps the woofer's backwash out of the amplifier driving the upper cabinets, making both upper and lower cabinets "cleaner" by making all the amps' jobs easier.

Is that true? I haven't a clue. Does it work whether it is true or not? I've never done it; no experience with the difference. People swear by it. I'd like to try it eventually.

If it were me I wouldn't bridge woofer amplifiers on an AR-9 and so three amplifiers isn't something I would do, personally. As an earlier post asked, if you aren't bridging them, what's the point?

Can you tell us what kind of amplifiers these are or would be?

By the way, I know very little. Sometimes it's dangerously little. The more I learn the more I learn I don't know.

I do know this, though: If you do have great big amplifiers and you have limited experience with speakers like the AR-9 you need to learn to recognize how loudly you are listening by something other than by how badly your speakers are breaking-up. Given enough amplifier the AR-9s will play cleanly into that volume which will make your ears ring and eventually cause hearing loss.

Bret

[Guest Nigel]

>breaking-up. Given enough amplifier the AR-9s will play

>cleanly into that volume which will make your ears ring and

>eventually cause hearing loss.

...and can cause hearing loss rather quickly.....

[Guest dogmeninreno]

>>breaking-up. Given enough amplifier the AR-9s will play

>>cleanly into that volume which will make your ears ring and

>>eventually cause hearing loss.

>

>

>...and can cause hearing loss rather quickly.....

Nigel, Point well taken. I used the preamp subwoofer R&L channels for the woofers and the main outs for the uppers. This gave me control of the woofers at low volume since the Adcom did not offer a loudness control or contour. It seems to be a great solution?? Dale