Bi Amping the AR9 - How do you do it?

[DavidDru]

So, those of you that have the 9's do you bi amp them?  If so how do you have yours set up?  Vertical passive?  Horizontal passive?

What gear have you used?

In my case I have the Adcom GFA 5500 and am thinking about getting another.  I have a few different preamps to choose from including the Adcom GFP 565, Xiang Sheng tube, and my recently purchased Citation 1.

Let's hear your success stories.

[DavidR]

One amp for the Lo Pass and one for the High

[ar_pro]

Wow. This topic brings back memories.

Several years ago, we had two identical Adcom amplifiers (GFA-555II) set up in vertical bi-amp mode, driven by the Adcom SLC-505 passive preamp.

The results were excellent; I can highly recommend this method.

 

[xmas111]

I vertically bi-amp my 9's with two Carver TFM-45 amps.   

Excellent sound from them.

[owlsplace]

If I had the option I'd try SS for the LF amp and tube for the HF amp -- that said, I haven't done it

Roger

[DavidR]

I think vertical bi-amping would be the way to go when you have the same two amps. However, if you have 2 amps with different, let's say, characteristics such as one that's good a driving low loads and has good bass and another that excels at mid and highs, I would go with horizontal bi-amping.

[michiganpat]

the question would be, which might have more variability in output, the left vs. right channel on the same amp, or the same channel on 2 separate but identical amps?

in a perfect world they should all be the same so it doesn't matter....my gut tells me there'd be less variability on 2 channels of the same amp than 2 separate amps, which would lead me personally to horizontally bi-amp...

[iso]

Horizontal passive is definetelly way to go if you are runnig close to power capabilities of amplifiers. When amplifiers are overdriven, this happens most likely to amps driving woofers and other amp driving mid to hf can still perform well. However if amps are true dual mono designs there should not be difference if amplifiers are truly similar.

Kimmo

[frankmarsi]

2-9-16

Back in 2014, when I first hooked up my newly re-foamed AR-9s, I had plenty (6) PL400s to try the ‘bi-amp’ configuration.

Having never heard AR-9s in my home before, I was very excited that I could actually ‘bi-amp’, something I  had read about often but never tried before. 

I didn’t get the pleasure I was seeking because one of the aging amps failed in a few days, then another failed, then another.

Consequently, I have given up until I get those old amps rebuilt, which will probably happen later this year. But, I did a few days of listening.

 

Obvious to me, I did not receive the effect I was expecting while the amp was running just before it gave out. What I did notice first off was that the speakers were not properly set up in the room as the speakers were sitting one third in the room when they should have been against the front wall for best bass output and balance.

 

 As it was, I found, and I could be entirely incorrect here but, the AR-9s seemed to be focused on the mid-range while lacking in the bass. At the time I felt due to improper placement .

But to the point here, I felt there was an off-balance in the speakers output while using identical amps. Was it the amps at fault, the need for new capacitors in the speakers? 

I was feeling, that perhaps if I had a lower power amp for the mids and tweeters, it may have been the better way to go? I didn’t have any smaller amps besides a Dyna ST-35 so, I never got the chance to try it that way. It’s been sitting ever since as shown in the foto.

 

As with the LSTs, I felt the PL400s ran out of steam when attempting realistic sound levels trying to power all of those drivers.

At some point later this year I will make a better attempt and report back.

fm

[DavidDru]

I pulled the trigger on a 2nd GFA 5500 last night.  $326 + shipping in original box.

My options for now will be the Adcom GFP 565 pre, which has multiple outs that can be used for bi amp purposes.

Also have the Xiang Sheng tube pre.

I've been happy with the lone 5500 up to this point on the various high demand speakers in my collection so I figured what the heck, keep going in that direction until I can afford an upgrade that is worthy of the $.  I will likely dial in the preamp first though and would like to go with a tube pre.  For now, the chinese tube pre is fairly impressive, especially for the money invested. (no phono though)

 

I guess I need to think thru my cabling now while the amp is on it's way.

[DavidR]

From the AR9 Manual>>>>>>>>>>>>>>>

[frankmarsi]

3-4-18

Straight from the horse's mouth.

Thank you DavidR, now I am certain. But why I didn't I catch that in the manual?

Small matter though. I only have PL-400's and three PL-700Series II so, even if I tried I can't escape high-power.

Power corrupts, absolute power corrupts absolutely.*

* John Dalberg-Acton, 8th Baronet

P.S. In the foto above of my AR-9 system #2 I'm using two PL-400 amplifiers of identical model with various other vintage components was then in early 2014, it's since been altered.

Nonetheless, this is almost uncanny as today one of the last three or so PL fellas who worked at the company when it was up and running pre-sell-out, called me  out of the clear blue. I had been trying to reach him regarding working on my amps, though I knew he was relocating. I had actually almost given up on this guy.

 This will hinge on what he'll charge for each rebuild of course. But, one thing for certain, I am having the power cut-off relay installed in each one.

Over the years, I have found the smaller PL-400 is a sweeter sounding little monster as compared to it's bigger sibling, it just doesn't have the large balls as it's bigger sibling. I also discussed with him that because of the reticent nature and sound response of AR's I'd like to solely continue using PL amps as they offer a sense of exuberance and slam as does my choice of MC phono cartridges in order to compensate for the AR speakers' reticent nature. This isn't happenstance, it's how I planned my system to sound since '74 when I first coupled AR and PL in my listening life.

I seek excitement and realism, not 1950's or '60s home speaker common sound quality which is fuddy-duddy in its sound quality and is well entrenched in sounding dated, muffled and canned and because it just doesn't move me as a system should be sounding realistic. 

Having to strain and saying to yourself "Uh, I think it sounds good" is not for me. Either it replicates the real thing or it's not. Been there, done that in the beginning, many, many moons ago. That fact is what propelled me to always keep my system growing. Onwards and upwards, no lateral movements for me chucko.

If I had JBL's I'd probably be using laid-back sounding amps to quell and compensate for their nature.

It's all about system-matching and system-synergy and I feel the road I've been on regarding all of this stuff has been the high road. Between my choice of interconnects, speaker cables, choice of MC cartridges, tonearms, ultra-sonic cleaning of vinyl disks, proper handling, et-all, has led me to have a system that is very revealing and probably one of the few vintage systems with as much detail and high resolution that anyone could speak of. It may not be as resolving as a current mega dollar system is but, it'll go toe to toe with most systems out there just not the super-duper silly money  and much costlier stuff.

Am I proud of what I've put together after all of these years in this insane hobby?  You can bet your last dollar I am.

Uh-oh, I went astray again, I'm such a blabber-er.  You must understand, I'm very satisfied with what I've put together.

DavidR, thanks again for posting that information. I may have to look for another PL-700 and try bi-amping again with my AR-9's?

Personally, I don't think AR-9's can handle it at higher volumes using two such high power amps with-out losing a tweeter or more.

FM

[nfmisso]

When I had AR9 speakers set up a decade or so ago, I used the amplifier sections of two Onkyo TX8500 recievers (dual independent power supplies) in vertical bi-amp mode.  They worked great.  Unfortunately, I had to sell that pair of speakers.  I am finally getting around to rebuilding my 2nd set of AR9s; the upper section is ready, a professionally is refoaming the woofers, hopefully I'll get them back on Saturday.  

I am concerned that the TX8500's may need some refurbishing, I got estimates in the $500-$600 each range from a couple of places here in the Bay Area.  I am not ready to pull the trigger on that, and am considering purchasing a digital oscilloscope instead, and doing it myself.  Of course, I don't have the time.....  So I purchase a Crown XLS1502 amp for now.  

 

[Pete B]

Frank, I wonder if the Phase Linear amps do not like the load of just the top or bottom 

of the AR9's.  Hate to see another or newly rebuilt amp fail again.

[frankmarsi]

Pete B, three years later and it finally sank in. Perhaps you are correct about the possibility that maybe the amps I used did not like the load it saw. Funny as I was on another forum and the OP was complaining about a similar situation. On the basis that all amps do not sound the same there may be something to the ability of certain components matching or just plain won't sound good with different speakers. Although the two 400's sounded good, I felt the bigger amp was better on its own.

I finally did shortly after when this post was new purchase a restored Phase Linear Series II PL-700 in immaculate condition, hooked it up to the AR-9's and in all honesty sounded better. The PL400's are excellent sounding amps, especially with AR's but for some reason the singular PL-700 alone with AR-9's seemed a better match.

In the future, I will attempt 'bi-amping' again because on paper seems to be the better way to go. And although sound-quality is my main goal, it's more fun watching four large VU meters operating with two amps in tandem.

FM

 

148

[DavidR]

Frank are your Phase Linear amps a magnetic field design like many of the Carver amps were?

Many Carver amps do not do well with a 4 ohm load which at times hits 3.2 ohms in the 9 and 90.

That's why I finally moved on from Carver, including the modified ones.  I tried many models.

I've never looked back.

[frankmarsi]

On 9/28/2021 at 9:18 PM, DavidR said:

Frank are your Phase Linear amps a magnetic field design like many of the Carver amps were?

Many Carver amps do not do well with a 4 ohm load which at times hits 3.2 ohms in the 9 and 90.

That's why I finally moved on from Carver, including the modified ones.  I tried many models.

I've never looked back.

Hi DavidR, no magnetic-field amps for me though, some Carvers did receive some good press. Many amps in general will not do well at 4 ohms.

All of my PL-400 amps are the original Series I Mk2 designs from the mid '70's.

My PL-700's are Series II, and are Full Complementary from the early '80s and have been rebuilt.

When Carver first introduced those magnetic-field cube shaped amps many folks went after them. Reports were menza-menza though for some folks, there's a new affection for them.

The series of magnetic-field designs you speak of came later and again folks went for them and were popular though, I've never tried one. The 'pro' models were  and still are widely used in commercial applications so, evidently, they're good to go. 

Carver's tube designs have received much praise.

FM

[Pete B]

Driving a woofer alone is a very inductive load and a zobel across it makes a lot of sense.

It does not have to be a perfect match, I'd put 8 ohms, 50W in series with 4uF across the

woofers.

Was it the woofer or tweeter amp that failed.

The other issue is a very light load allows that amp to go deeper into clipping (slowing down

BJT output devices that can result in cross-conduction).  Any load will help avoid this so  22

ohms 50W across the mid-tweeter might help in that regard.

Was the system driven hard when it failed?

Was it a 400 or 700 amp that failed?

 

There was a post on DIYaudio where a top name in audio was testing a few amps with long

(20ft?) speaker cables into speaker loads and two of them where showing oscillations due to

the tweeter inductance.  .1uf in series with 10 ohms cured it and should probably be used in

all speakers to avoid such issues.

[frankmarsi]

5 hours ago, Pete B said:

Driving a woofer alone is a very inductive load and a zobel across it makes a lot of sense.

It does not have to be a perfect match, I'd put 8 ohms, 50W in series with 4uF across the

woofers.

Was it the woofer or tweeter amp that failed.

The other issue is a very light load allows that amp to go deeper into clipping (slowing down

BJT output devices that can result in cross-conduction).  Any load will help avoid this so  22

ohms 50W across the mid-tweeter might help in that regard.

Was the system driven hard when it failed?

Was it a 400 or 700 amp that failed?

 

There was a post on DIYaudio where a top name in audio was testing a few amps with long

(20ft?) speaker cables into speaker loads and two of them where showing oscillations due to

the tweeter inductance.  .1uf in series with 10 ohms cured it and should probably be used in

all speakers to avoid such issues.

Pete, your last paragraph is intriguing but, I would need further explanation. However small, adding more capacitance would decrease 'highs' wouldn't it, and adding a 10 ohm resistor as you suggest brings us to what value that the amplifier sees?

My speaker cables run about 30 or more feet per side, I use 12 AWG with the 2amp slo-blow fuses.

[Pete B]

The 8 ohm and 4 to 10 uF capacitor are in series across the woofers, the cap

impedance goes down when the woofer impedance goes up at high frequencies.

It flattens the rise to about an 8 ohm load at high frequencies so that there is no

inductive "kick back" from the woofers.  Only do this when biamping.

[DavidDru]

Some time has passed and I no longer have the 9's unfortunately.  I had a few audiophile buddies that were just jonesing for them and my room just isn't big enough so I let them have them.  Since then I have come into a pair of big Marantz Reference monoblocks and I wish I had the 9's to try with them.

[Pete B]

@frankmarsi  Have you seen the service bulletins for the PL700 from the factory?  I have

several of them somewhere on my computer.

[frankmarsi]

Hello Pete B, long time no speak  but, to answer your question, no I don't have any copies of service bulletins or any other documents from the factory.

Though now, you've made me wonder if such information would be included in such docs. I would imagine they'd highlight simple items of  possible different loads that may be used but,  the likelihood of any further info would be interesting. I really don't know. I doubt I have any info from my first purchase of Phase Linear amp back in 1974. If you're kind enough to send me file, that would splendid and I would be gratful.

FM

 

[DavidR]

Some one at the Carversite might have info.

https://thecarversite.com/

[Pete B]

@frankmarsi

You can find the 700B and 700 Series 2 service manuals, and many others here in the AudioKarma data base:

http://akdatabase.com/AKview/thumbnails.php?album=94

Many of the service bulletins are included in those docs.

I'm not sure if you have to sign into AudioKarma to have access to the documentation.

Frank, do all of your amps have the White Oak upgrades?

https://www.whiteoakaudio.com/estore.aspx

Pete B.