Help. May I speak with one of the Audio-Elders please?

anacortesian

anacortesian

New Member
Let me briefly explain. And I explain this as a reminder to others as well. I (used) to have a nice system. Two AR3a speakers- vintage high end old school. With a Kenwood KA6000 200 watt amp (1969) rated at 45watts per channel I think. All was good. Then I lost the woofers to flooding. Managed to save the mids, tweets, cross-overs, and bandaged up the cabinets. Then I came across these two old school Infinity KCS-120 IB 12" sub-woofers that are labeled 4 OHM 250 watts RMS 450 watts peak. I put those in the AR3a cabinets and all sounded pretty good. It had been so long since I had listened ...that I cranked the volume (only half way or so mind you) ...and smelled something burning...and there was a horrible crackling...and the music faded away... and I watched in horror through the top cover ventilation holes as a pwb and row of 5 transistors lit up and burned. I still don't understand what exactly happened...and I blamed it on the age of the amp. BUT. I also think that I may have over-driven (or under-driven) those infinitys with the Kenwood. I had cranked that Kenwood before with the AR3a's and no problem. So the amp is cooked and gone.

So I need to get another amp. And a matching tuner to work with these speakers. I know I want retro. I like Kenwood (silver face like a KA 3500 / KT 5500 combo or similar). I think the KA3500 is rated 40 watts per channel I think. But I think I had better match correctly here before I go back to ebay... or the same thing may happen again!
Your thoughts?

Thanks
Jay
 
I'm no audio elder, but....
The load that the speakers present to your amp may be too much. The AR3a are 4 ohm speakers as is, but your addition of a non-OEM subwoofer may make them even harder to drive. Make sure whatever you buy can handle a 4 ohm load, maybe even a 2 ohm load.

Also, I assume you pulled the drivers only, and didn't install the subwoofer amplifiers in the AR cabinets? You don't want to send power into your amp through the speaker terminals.

Anacortes, WA? I have family there. I'd love to visit sometime; sounds like an amazing place.
 
Sounds like you need to get a pair of the correct woofers in there and fix that nice Kenwood amp. Tossing in random 4 ohm subs into those previously nice speakers is just asking for what happened to happen. Speakers need a recap I assume too.
 
test the ARs and whatever is left of the subwoofers. you could probably feed mid+highs to the AR and
bass to the Infinitys (could be the infinitys have a crossover net work in place and can run bass
and feed highs back to the ARs - depends on the design and hookups)

your Kenwood was/is approaching 50 YO and unless its been recapped/tuned then
it is probably the root cause (as opposed to something external like speakers or cables
setting it off) and if you were to have it repaired then a full recap is required.

if you do buy another kenwood or another brand, and if its over 20 years old, then
the safe thing to do is a recap and someone going over it to ensure good performance.

it would be like buying a car that's 20-40 YO and changing oil, transmission fluid, belts, brake fluid,
air/gas/trans filters, checking steering fluid and brakes. of course the tires have to be replaced.

if you want something worked over by AK giants, buy something they've fixed or refurbed.
over the long run, they will work better and overall, costs less.
 
Locate and install the correct woofers. Your AR's deserve better. Most likely the replacement drivers were the cause of your amps meltdown.

Have your amp repaired/restored, it will probably cost less and last longer than a reasonably priced alternative.
 
Don't toss that amp.
It sounds toasted and they are a pain to work on, but they are very desired and even the parts have value.
 
Thanks and good advice all...
Can anyone recommend a good vintage amp for these speakers? Again they are Infinity KCS-120 IB 12" sub-woofers labeled 4 OHM 250 watts RMS / 450 watts peak.

Jay
 
I'm gonna keep this really brief & concise.

Dont NOT use those Infinity subwoofers with any vintage home audio gear,they simply were'nt intended for that sorta usage.
They are car audio SUBWOOFERS intended to be used in an infinite baffle speaker design,hence the IB suffix in the part number.
FWIW the AR3A speakers used woofers,not subwoofers,and those AR3A are acoustic suspension speakers,not infinite baffle speakers.
Thus it SHOULD be clear that those Infinity subs are'nt remotely an acceptable replacement driver for those AR3A woofers.

It's not a matter of finding a "better" vintage amp to "match" those Infinity subwoofers...
It's a matter of finding some correct speakers to match the sort of gear that's driving them.

Keep using those Infinity subs w/o regard for the critical details,and you'll likely keep burning $#!t up.

HTH

Bret P.
 
Okay Bret. Tough love. God damn-it! I thought I could mod-and-build something ...but ...your right. I did some checking around. They are car speakers. I think they are niice speakers. ...But they are car speakers. So that's all I needed to hear .I'm going to have to throw them on ebay for some millennial with a high end Acura... and I match a system from scratch.
 
I say figure out what you want as far as sound goes...

Different amps and different speakers combined create a different sound. Learn about the equipment because it’s not going to do what you want. Equipment is just like the many peices of a puzzle, if you don’t put the right pieces together you won’t get the sound you like.
 
anacortesian said:
Okay Bret. Tough love. God damn-it! I thought I could mod-and-build something ...but ...your right. I did some checking around. They are car speakers. I think they are niice speakers. ...But they are car speakers. So that's all I needed to hear .I'm going to have to throw them on ebay for some millennial with a high end Acura... and I match a system from scratch.
Click to expand...

In what part of the world are you located? AKers are everywhere. You might get lucky and find someone that can help fix your ARs or lead you to something else.
 
Yep!!! 4 ohms to low. Any amp would have a hard time driving those without frying. Anything under 8 ohms could prove difficult. Maybe 6 ohms, but don't bet on it.
For example I have a pair of 6 ohm speakers on each side of my amp. For safety I set them up in series and have never had a problem. Maybe 12 ohms but the ohms is based on inductance, not resistance so other issues are present. More like 10 ohms.
Car audio is different for some reason and gets along happily with 4 ohm speakers. This low ohms on car speakers has been around for a long time.
Ever since I have been messing around with audio.1956 the last time I tried to figure out my life's chronology.
 
At this point, I would seriously consider parting out whats left of the AR3a's. Those remaining tweeters and mids, if still functional are worth some $ and you could probably buy another nice set of speakers with that.
 
I am going to be a contrarian here. A speaker designed for car audio use is not fundamentally different than one for home audio use. Now there are dual voice coil subwoofers on the market, and each side of the speaker will be the rated ohm stated, typically 4 ohms, so if you combine them it shows an aggregate 2 ohm load. But that is not the case with the Infinity specifications on this model number, its a single voice coil 4 ohm woofer.

It is meant for different cabinet sizes, actually its designated for open baffle applications, so it has a high QTS. But it will work at some level in that cabinet, especially if its a sealed one. This is not the reason for the amps failure. Now the original AR3a woofer is going to have different spefications such as impedance and efficiency, and its not likely this Infinity is a direct replacement. The sound of the speaker is going to change in the bass region. But that is not going to kill an amp.

In my opinion what happened is that the combination of a 4 ohm load, and the amp being driven hard led to its death. If it has not been restored, its getting long in the tooth, and what you saw was parts failure at some stage in it. I am not that technical a pig, so I cannot say it was power supply, regulation, open capacitors, or what the exact cause was. But it did happen to the amp when being put under stress and driving a lower impedance woofer load. That was just too much for a compromised amplifier to handle.

I would say get the amp serviced. Blhagstrom up in this thread is a good tech, maybe he can service it, if you want to pay to get it repaired. If you buy vintage electronics this is an inherent risk if you don't get stuff checked out and serviced. Sure the speakers deserve the proper woofers, but those Infinity don't deserve all the blame for the amp dying.

Regards
Mister Pig
 
Last edited:
The ( AR3a Restoration ) document that Katalyst posted shows all 3 drivers are about 4 ohms in impedance .

I X-simmed the network ( seen within that document ) while simply using straight 4 ohm resistances for each driver.

The results aren't too surprising.

The overall load of this AR3a network is very low ( 4 ohms & sometimes smaller ).

It would take a robust amp/receiver to not eventually melt-down driving these speakers ( especially if it's older tech that needs attention ).

A Google search for "AR3a amp killer" returns a few interesting hits.

:)
 
I know what I'd do. sell the whole lot and start again. There is still a buttload of good gear out there.
If the 3a enclosures are flood victims, separate drivers and network, sell as a set. If you want to make subwoofers, keep the JL's and make enclosures. If not, sell. Take the top off the amp or inspect through the ventilation grate. If the circuit board is through-holed or burnt along an edge, sell for parts. If not, it can be repaired but that costs fair money. I have some Kenny gear and think it's some of the best made (KA-8150, KT-7550). Listening to broadcast FM through the Kenny tuner will make you a believer.
Good luck with your choices!
 
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