Driving these AR3a speakers

[Ray O]

So I have determined I may be making huge mistakes in my choice of amp/speakers.  I have two pair of AR3a in very nice condition.  Driving them with a Pioneer SX-1280 (185W per channel).  I have one pair connected to Speaker A and the other connected to speaker B.  Usually drive both sets together.  These speakers are 4 ohm, and my receiver specs are written for 8 ohms.  There is even mention in the service manual where I may have problems with the limiter section of the amp driving speakers less than 4 ohm.  However, the guys at the local stereo repair shop say the amp should have no problem driving these speakers.  They do sound great, and I have not hit the limiter much and only when the gain is 80-85%.

So my questions; Am I making a mistake driving 4 ohm speakers with an 8 ohm amp?  And considering 185 Watts per channel may be too much, should I insert a fuse inline to protect the speakers?

Thanks, 

Ray

[harry398]

the 1 pair of ar3a is 4 ohm nominal

 

driving 2 pair at once is 2 ohms or less

this is a HUGE no no.....especially with what amp you have.   the amp may have 185 w , but can it handle 4 ohm?  certainly I doubt it can handle 2 ohms.

1 pair at a time...moderate levels.....that amp should be ok.................but I recommend something better myself.   you will be sad if you take out some drivers....

[genek]

At certain frequencies, the impedance of the 3a can dip as low as 2 ohms, which means running two pairs may result in 1 ohm across the amp. 

You shouldn't even be running one pair of 4 ohm speakers on an amp rated for 8 ohm speakers.  Find another stereo repair shop.

[JKent]

Ray

Please don't construe this as rude but you already know the answer. You blew 2 drivers. 

The Pio is a beautiful and powerful receiver but it can't handle those loads. According to hifi engine's site the amp can handle a minimum of 4 ohms but as Gene wrote the ARs can dip as low as 2 ohms and as you know, the Pio is only rated for 8 ohms.

There are lots of options for 4 ohm amps to drive the 3a's. Maybe use the Pio with a nice set of 8 ohm speakers.

Did the guys at the local shop know you were driving 4 AR-3's? If so, I'd say Gene is right (find another shop).

Good luck and keep us posted. Great speakers, great receiver. Just not together.

-Kent

[Ray O]

OK.  Thank you for telling me what I already knew.  And I was so hopeful.  I love this amp, and the speakers are oh so perfect.  With the blown AR3a I have substituted a pair of Bose 501s for the secondary speakers.  I can drive the heck out of these, and as long as I don't go above 75%, I do not have any problem with the amp limiter circuit.  

So, this brings another question.  What vintage receivers would drive the two pair of AR3a?  Maybe I should seek an external amplifier.  Any suggestions?

Really like this forum.

[genek]

I doubt there has ever been any receiver made designed to run two pairs of four ohm speakers at the same time. If that's what you want to do, you need another power amp for the second set of speakers.

[JKent]

20 minutes ago, Ray O said:

What vintage receivers would drive the two pair of AR3a?  Maybe I should seek an external amplifier.  Any suggestions?

I think your Pio has a Preamp Out. If so, you "could" keep the Pio tuner/preamp and add a couple of modern & powerful & cheap Crown amps. Something like the Crown XLS 1502. The 1502 delivers 525wpc into 4 ohms for $400. The XLS 1002 will give you 350wpc for $300. The subject of modern high power low impedance power amps for AR speakers has been discussed quite a bit in these pages. QSC is another brand. Or in the "almost vintage" category the Adcom 555 works well. I use a 555/II (325wpc) with some 4 ohm AR-91s.

-Kent

[Martin]

Why not connect two AR3as in series (rather than in parallel) on each channel? It seems like this would solve several  problems simultaneously, particularly if you usually like to use both pairs together.  

 

[Ray O]

I thought about connecting them in series, but for some reason that just sounds wrong.  

[onplane]

20 hours ago, Ray O said:

So, this brings another question.  What vintage receivers would drive the two pair of AR3a?  Maybe I should seek an external amplifier.  Any suggestions?

RAY, not vintage, but the Sherwood RX-5502 (see datasheet attached) would handle 4 AR-3a's.  Reason for this is this unit has 4 full range amps (i.e. 2 stereo amps) in a single box.  Each amp is rated 100 wpc at 4 ohms.

Beauty of this scheme is you get two independent volume controls so you can balance the two set of speakers to get similar volume in spite of room placement. With a single amp, one speaker set with dominant the other just due to its position in your room.

 

Regards,

Jerry

Sherwood-RX-5502-datasheet.pdf

[Aadams]

On 2/10/2018 at 9:39 PM, Ray O said:

So, this brings another question.  What vintage receivers would drive the two pair of AR3a?  Maybe I should seek an external amplifier.  Any suggestions?

Acquiring a vintage receiver or integrated you can trust to reliably to drive 4 AR3as will probably cost as much as 3 Crown XLS 1002s that each crank out  550w per channel at 2 ohms. 

 

On 2/10/2018 at 9:51 PM, genek said:

I doubt there has ever been any receiver made designed to run two pairs of four ohm speakers at the same time. If that's what you want to do, you need another power amp for the second set of speakers.

Maybe a Macintosh Integrated or receiver will do this. Their layout gives this impression, they have protection circuitry but they will not come close to the wattage of a digital power amp and even used will cost more than the smallest QSC or Crown and almost certainly have zero warranty. 

[Martin]

On 2/11/2018 at 2:20 PM, Ray O said:

I thought about connecting them in series, but for some reason that just sounds wrong.  

It's not wrong, it's right.

[DavidR]

Thread title should be "Releasing the Magic Smoke"

<sorry, couldn't resist>

[Ray O]

Funny.  I will be able to appreciate the humor once i get this speaker fixed.  In the mean time, resolving to take it easy.  

[lrmccloudjr]

You will lose 3db in series, however you will now have an 8ohm load.  You gain 3db for each additional speaker, so basically a wash.  How loud are you trying to go?  I would definitely concur on the pro amp route.  Crown and Qsc will both drive a 2ohm stereo load.  You would want significant headroom so as not to overtax the amp and get fan noise.  I would go for about 500 a channel.  Pro amps use IEC rating at 1kz.  Who I will be about 10% less if converted to RMS.  Hope that helps

[Anita]

I am frustrated in trying to replace a receiver for my original AR3a speaker pair.  I made a stupid mistake when my original receiver died..I forget which it was..1969.  I remembered a number of receivers from that time period & bought a Kenwood that ‘worked’ not realizing it needs to be refurbished whatever I buy.  This was 2013...died 2019.  I did folk singing + guitar & into those vinyls.  I have a Miracord phono.  The sound from these speakers has been a delight for this music.  I have never needed any service on the speakers. The receivers that have been suggested are Marantz 2230 only 30 watts.  Original booklet said only 25 watts needed,  but at 4 ohms I can get 45 watts out of a Marantz 2240B.  Then there is Pioneer SX780 also 45 watts then someone saidPioneer 850 at 65 watts worked well with these speakers..Yamaha CR-620 might be good.  I am a senior..HELP!

Anita

[Aadams]

2 hours ago, Anita said:

I am frustrated in trying to replace a receiver for my original AR3a speaker pair.  I made a stupid mistake when my original receiver died..I forget which it was..1969.  I remembered a number of receivers from that time period & bought a Kenwood that ‘worked’ not realizing it needs to be refurbished whatever I buy.  This was 2013...died 2019.  I did folk singing + guitar & into those vinyls.  I have a Miracord phono.  The sound from these speakers has been a delight for this music.  I have never needed any service on the speakers. The receivers that have been suggested are Marantz 2230 only 30 watts.  Original booklet said only 25 watts needed,  but at 4 ohms I can get 45 watts out of a Marantz 2240B.  Then there is Pioneer SX780 also 45 watts then someone saidPioneer 850 at 65 watts worked well with these speakers..Yamaha CR-620 might be good.  I am a senior..HELP!

Anita

If vintage is what you require the Pioneer 850 or 780 would be good but an old 850 that you could trust with your speakers would cost about as much as a new Cambridge AXR 85 which has everything you need + a warranty and also got a great writeup on this site about a year ago, though I can't remember the member's name right now.  User "Der" gave the Yamaha 701 integrated amp good marks, the Yamaha 501 which is similar but lower cost seems to have what you need if you don't require an FM section.

Adams

[Anita]

Really..a new one can be used with these speakers?  I didn’t think that an option. I appreciate all your suggestions...thank you!

[Johann_Cat]

For others interested in this issue (the demands of the great-sounding but low-efficiency 3a), I recommend class D power amps for AR 3as; class D amps can drive 2 ohm loads and generate a tiny amount of the heat (undetectable heat in my use--I can't tell to the touch that this NAD C268 is generating any heat) that a vintage class A amp can.  3As as a single pair can demand loads of under 4 ohms, even 2 ohms intermittently, and a vintage class-A (rated safe for 4 ohm loads) confronted with that work can get fry-an-egg-near-the-heat-sinks hot: not good, stop, change course.  I still use a vintage amp (a Sansui 999) as a pre-amp and control surface (it was designed with the ability to uncouple its power stage), and class D power amp.  Until I got 3As, I didn't know much about class D amps.  One can investigate them in detail at audiosciencereview dot com.

[ReliaBill Engineer]

My 1981 Sherwood amp has handled 1 ohm loads just fine over the years. The only thing I’ve had to replace in 43 years is the power switch.

What most are neglecting here are the true specs of any given amplifier. 

Every amplifier has an output current rating that must not be exceeded. At lower impedance, that max current rating is reached at lower volumes. So you can safely power low impedance speakers, but not at the same volume level as for standard nominal 8 ohm speakers. 
 

It really comes down to the max current rating of your amp, and that can’t be exceeded. That max current rating is reached at lower volume settings when using lower impedance loads. Physics. 
 

A high current amp will have max output ratings for 8 ohm, double that for 4 ohms, double again for 2 ohms, and double again for 1 ohm. But very few can handle that doubling down to 1 ohm. What you’ll see is a DERATING as the impedance is reduced. That derating reflects the current limitations of the amplifier. 
 

My Sherwood is rated at 90 w/ch (clean RMS) into 8 ohms, 180 w/ch into 4 ohms, 200 w/ch into 2 ohms, 200 w/ch into 1 ohm. Doubling of power stops at 4 ohms.

So the Pioneer amp can be safely used to power 2 paralleled sets of 3a’s, but at reduced volume settings. Don’t exceed the current rating of the amp.

[Johann_Cat]

" the Pioneer amp can be safely used to power 2 paralleled sets of 3a’s"

I know we are in the hazards of following an ancient post, but note please the key detail above in the OP's posts is that he blew two AR 3A drivers (likely woofers) in trying to drive 2 paralleled sets of 3as at less than 4 ohms.  Several people, and I, recommended using a power amp rated for loads of less than 4 ohms; he showed up here because someone had already told him it was likely fine to use a vintage class A in this labor, and that experiment spectacularly did not work.  Empirically, based on my experience of several class A amps (rated at 70 watts at 4 ohms) getting hot driving 3As, I don't think it is a good idea, and I'd rather play it safe with a class D power amp; if someone can drive a Sherwood at 1 ohm as you say, good for you.

[Andre_Db66]

Class D is something completely different in sound signature, and a good one producing  450 watts at 2R sets you back at least 1600$, a NAD is probably even more.

What is preferred in this situation is a pro amp without fans, with clipping circuitry.

Obviously we have someone here who loves to drive his speakers hard and doesnt seem to know when to quit. The killing of drivers is evidence. Lucky for the author the Pioneer still works and only 2 drivers were fried as DC coming out of a power amp@ 185watts will kill the lot, including amp imho.

I have personally stacked two pair of ar6 in series with a 30 watt amp and that works fine.

My double ar3a are driven by 2 yamaha pc2602 and they are the only speakers which got the fans running, ever... A yamaha M2 rated a little lower than the pc26p2 started clipping when driven hard on 1 set. We are talking 240@8R/400@4R and 225@8R respectively.

Quad 303 is unconditionally stable, you cannot blow it even if you short circuit the speaker leads. However rated at 30 volts@3A will not still the power hunger of the author.

To keep things without added cost other than new drivers set it all up in series. 8R load. Beware of heating the amp though.

To go easy on the wallet and vintage buy 2 Crown D300(preferably mk2), they have clipping circuitry and are affordable. Important fact... they also sound great.

The adcom 555 is another great deal but not vintage.

Yet another road is a tube amp because of the circuitry it uses it will simply start to sound bad when close to clipping and one will automatically turn down the volume. Most tube amps have 4R outputs. Finding one with required power can be expensive as it will take something like a push pull 845 tube amp. I have a set of monos from icon audio @100 watts p ch, but second hand would set you back around 3500.

Crown K1 or K2. No fan, clipping circuitry, endless power.

NO MCINTOSH. It is overrated and massively expensive for what you get.

Any questions? Ask me... i have many many amps and tried many also.

Krell, icon audio, bryston, yamaha, sansuu, crown, dateq, purifi, adcom, rotel, vanmedevoort... list is longer

[DavidR]

[Andre_Db66]

Nice!

Borrow a forklift to bring it home... 🤣

 

 

Grand total of 4.9Kw