AR98 LSI

[sebtus]

Hi,

i have AR 98LSi speakers fully re-caped. i love the way sound , real nice to my ears and they look nice, but i have a bit problem. My set up can drive them past 12 o'clock volume on me pre-amp. My amp simply clips and there is no sound.
i have pioneer SX-1250 which can not handle them. then i got accuphase p-300 amp and accuphase c-200 pre-amp . I got them re-caped and readjusted. same results. recently i got PL-400 and i'm thinking about rebuilding it with White oak kit. Do you guys think it will be able to handle my speakers??. if not what else can i do? what amp should i look into?

thank you

 

[Billboard]

That does not sound like clipping. When you have clipping the amplifier is distorting on the peaks, sounds bad, and is worse for your speakers especially the delicate tweeters.

What you have sounds like your equipment is going into protection.Most likely because of overheating. What is the Ohm ratting of your speakers? if less than 8 you most likely need a fan on your amplifier.

If at less than 8 ohms you will need a fan on your phase linear at louder volumes.

If you have 8 ohm speakers, perhaps they are going into protect for being over driven, what is the power handling (max power) rating?

 

[sebtus]

You are right about the clipping, my bad . The protection circuit kicks in. The sound goes out of a sec and then it comes back and then does it again until i lower the volume. it seems to me that speakers demand lot of current at high volume and over-current protection kicks in. AR 98lsi are 4 ohm 250w speakers.
I don't think it is overheating problem since it happens even when the amp is cold.
when i did the adjustments for the accuphase P-300 i had tested it at 200W at 8ohms (load resistor) and it worked fine for both channels. but i never did it with 4 ohm load.
A while back had a PL400 series 1, early version which i re-caped and readjust but i was afraid to us it with my AR since i did not have any protection circuit installed.

 

[laatsch55]

If your 400 still has the stock output transistors (xpl909) I b would not run it without DC protect installed. A 4 ohm load on those 40 year old outputs is a disaster waiting to happen.

IMHO, with speakers like that, I would be running a fully White Oaked 700. Plenty of current for those puppies...

 

[62vauxhall]

Those speakers will present lower than 4 ohm impedances to an amplifier. Closer to 2 ohms in some instances.

 

[sebtus]

I would like to get my hands on PL700 and rebuild it but they are expensive... I was looking for a repair one but i cant find anything. Maybe one day something comes up. For now all i have is pioneer sx 1250. Accuphase p300 and newest addition PL400 which needs to be at least recaped. It is amazing how much power those ARs need. I think 50% volume will have to do for now. And maybe one day i come across something that can handle my speakers.


My accuphase P300's protection board is set to activate when impedance goes below 2ohms. So if that is the issue im having it means that speaker imp. goes lower than 2ohms at higher volume.

 

[laatsch55]

No, not at high volume, but at certain frequencies. Speakers will exhibit different impedence at different frequencies. Somewhere there is an impedence/frequency graph on those speakers, that will tell you a lot....

 

[laatsch55]

It may be sensing that two ohm load easier at high volume, but it's still there at moderate volume too...

 

[sebtus]

Specification sheet indicates that the minimum impedance is 3ohms. Does it go lower? I dont know. No way for me to check.

 

[laatsch55]

The spec sheet is not an impedence plot. With a little digging you might find it..

 

[sebtus]

i am looking but no luck so far.

 

[laatsch55]

I looked for awhile, couldn't find anything either...

 

[Northwinds]

 

[OneTonScoutII]

I would like to get my hands on PL700 and rebuild it but they are expensive... I was looking for a repair one but i cant find anything. Maybe one day something comes up. For now all i have is pioneer sx 1250. Accuphase p300 and newest addition PL400 which needs to be at least recaped. It is amazing how much power those ARs need. I think 50% volume will have to do for now. And maybe one day i come across something that can handle my speakers.


My accuphase P300's protection board is set to activate when impedance goes below 2ohms. So if that is the issue im having it means that speaker imp. goes lower than 2ohms at higher volume.

It's not like a white oaked 400 is anything to scoff at, I think you would be supremely happy with the 400 done up too.

 

[WOPL Sniffer]

It's not like a white oaked 400 is anything to scoff at, I think you would be supremely happy with the 400 done up too.

SUPREMELY HAPPY, would HAVE to include 700, tickled pink would be for a 400

 

[OneTonScoutII]

SUPREMELY HAPPY, would HAVE to include 700, tickled pink would be for a 400

Fair enough but going from a non WO 400 to a WO400 is a massive jump

 

[laatsch55]

True dat....

 

[sebtus]

Is it possible that there is an issue with my speakers which causes the amp to go into protection mode at high volume?

 

[Northwinds]

Is it possible that there is an issue with my speakers which causes the amp to go into protection mode at high volume?

I was wondering that myself, if one thing was done wrong when redoing the crossovers, you can cause a huge problem

 

[62vauxhall]

As was mentioned, those speakers will dip down pretty low impedance wise at some frequencies. The lower the impedance, the closer to a dead short so the amp's protection circuit is doing exactly what it's supposed to do. This was the case initially with a Double Advent system I had in the mid 70's. For optimum performance they were to be wired in parallel and although each speaker cabinet was rated at 8 ohms, they were actually closer to a nominal 6 ohms so in parallel, the amp saw 3 ohms on occasion. My "dealer" at the time let me take equipment home to try out over a weekend and several power amps could not tolerate impedance that low and shut down. As you are experiencing, this manifested when the volume was turned up but low level listening was fine. I lived in a house back then where loud music was de rigeur and it took several auditions to find an amp I could afford that would not shut down. Early on, the service department of the shop I bought the Advents from suggested a load resistor on each speaker to bring up the impedance but that made me blow tweeters.