LST ? tri amp with no crossover

[roundhome]

Hello i'm close to finish putting these back together. But still no crossover I have a dbx electronic cross over and six mono blocks what should i put between the drivers and the amps, cap wise to ptotect them from any dc?

Thank you

JIm

[onplane]

>Hello i'm close to finish putting these back together. But

>still no crossover I have a dbx electronic cross over and six

>mono blocks what should i put between the drivers and the

>amps, cap wise to ptotect them from any dc?

>Thank you

>JIm

What DC?

Seriously, your mono blocks better not be putting out any DC. If you want to protect the drivers, most folks use fuses.

Regards,

Jerry

[onplane]

Roundsound, just want to say that I'm impressed with your project. Normally, I'm NOT a big fan of active bi-amping.

These LST's, however, seem like the idea candidate. Driving the units directly with their own amps and eliminating the autotransformer, the coils, the caps and resistor certainly has terrific potential.

My AR-3a's have identical drivers, but NOT nearly as many. Keep us posted on how this goes.

I have enough amps to tri-amp my 3a's (actually I have more than enough - I can tri-amp them 3 times). The electronic xovers are reasonably priced these days and even the mid-priced units have level controls to balance all of the channels.

Could be an interesting project.

Has anyone tried active tri-amping of AR-3a's?

Regards,

Jerry

[roundhome]

>Roundsound, just want to say that I'm impressed with your

>project. Normally, I'm NOT a big fan of active bi-amping.

>

>These LST's, however, seem like the idea candidate. Driving

>the units directly with their own amps and eliminating the

>autotransformer, the coils, the caps and resistor certainly

>has terrific potential.

>

>My AR-3a's have identical drivers, but NOT nearly as many.

>Keep us posted on how this goes.

>

>I have enough amps to tri-amp my 3a's (actually I have more

>than enough - I can tri-amp them 3 times). The electronic

>xovers are reasonably priced these days and even the

>mid-priced units have level controls to balance all of the

>channels.

>

>Could be an interesting project.

>

>Has anyone tried active tri-amping of AR-3a's?

>

>Regards,

>Jerry

I have a driverack PA it will let me tweek them in completly pink noise mic and eq along with slope and crossover pionts and time alignment.

but I recall Ken Kantor tellingme to put some caps in line just can't remember what they were

Jim

PS i didn't take out the crossover I wish I had them these were just boxes when i got them

[onplane]

>I have a driverack PA it will let me tweek them in completly

>pink noise mic and eq along with slope and crossover pionts

>and time alignment.

>but I recall Ken Kantor tellingme to put some caps in line

>just can't remember what they were

>Jim

Jim, the original xovers had a 6MFD in series with the tweeters and a 40MFD in series with the mids. Naturally, you wouldn't put a cap in series with the woofer.

Purpose of those caps was to "block" unwanted frequencies from getting to the drivers. Your xover should completely handle this function.

I wonder if the small dc offset (<50 millivolts) in ss amps has an impact on linearity in the mid and HF drivers? I wouldn't think this would be the case.

Regards,

Jerry

[rrcrain]

Interesting point about the DC offset. If there is a cap in place, there won't be current flow to heat the voice coil but without a cap, there will be current flow thru the amp and voice coil 100% of the time. I've no idea if this will cause an audible effect but suspect it might. Other than that, it will generate an infintesimal(sp) amount of unwanted heat.

Regarding active bi-amping. I've run my speakers single amped, simple bi-amped (no active crossover) and with an active tube bi-amp. The strongest and simplest statement I can make to describe active bi-amping is my wifes jaw nearly fell off the first time she heard it. The WAF was absolutely 100% in favor.

[onplane]

>Interesting point about the DC offset. If there is a cap in

>place, there won't be current flow to heat the voice coil but

>without a cap, there will be current flow thru the amp and

>voice coil 100% of the time. I've no idea if this will cause

>an audible effect but suspect it might. Other than that, it

>will generate an infintesimal(sp) amount of unwanted heat.

>

>

>Regarding active bi-amping. I've run my speakers single amped,

>simple bi-amped (no active crossover) and with an active tube

>bi-amp. The strongest and simplest statement I can make to

>describe active bi-amping is my wifes jaw nearly fell off the

>first time she heard it. The WAF was absolutely 100% in

>favor.

Richard, your ACTIVE bi-amping is really interesting!

Please tell us EXACTLY what you did. If AR-3a's, did you tri-amp?

The active xovers are quite reasonable today, I'm really thinking about giving this a try and lord knows I have amps all over the place, so that's not a problem.

Richard, in your opinion, which drivers contributed the greatest to the improvment you heard?

Regards,

Jerry

[rrcrain]

I should have clarified my bi-amping and my apologies for not having done so up front.

I rebuilt a pair of AR90s about three(four?) summers ago and while I was at it, I investigated the possibility of splitting their crossover to permit them to be bi-amped. I'm the original owner of these speakers and have owned and listened to them since 1980.

The original caps were pretty well shot, having drifted in value the tweeters and upper mids were mostly inactive. In fact, I later discovered the original caps were so bad they masked one bad driver, an upper mid. In any event, this is what led up to the bi-amping.

For the bi-amping itself, that didn't happen for another year or so. During that time, the new crossovers had a chance to settle down, I replaced a couple of bad drivers and played around with passive bi-amping, had the power company damage both amps twice and tried the Dahlquist crossover out.

Personally, I think the Dahlquist crossover is over rated but it does work within reason.

I did more research and decided to purchase a Marchand tube crossover in kit form, saving myself about $1,000. I chose crossover points one octave over and under the speakers passive crossover point to keep from overtly affecting their performance, and the results were out of this world.

At first blush, the bass sounded diminished, but it's actually become very controlled and sounds as if it reaches a lower frequency.The vocals suddenly cleared beyond anything I could have imagined. My wife, who is notorious for not understanding lyrics, was hearing lyrics for some of her songs for the first time ever. The sound stage became much more 3 dimensional, and it wasn't bad before. The high frequencies are as clear can be. I've listened to a pair of $10,000 Canton speakers and prefer my AR90s hands down.

For your project, based upon my results, I would recommend you check out marchand's 3 way tube crossover. It's not inexpensive, but it's very very good.

[onplane]

>I chose crossover points one octave over and under the speakers

>passive crossover point to keep from overtly affecting their

>performance, and the results were out of this world.

>

Richard, now I'm really confused!! Let me see how do I ask this ...

When you have your ACTIVE tube xover running, do you also have the passive xovers still intact inside the speakers?

Regards,

Jerry

[rrcrain]

As odd, and wrong as it may sound, yes, the passive crossover is still present.

AR recommended NOT removing the bass section of the crossover in the AR90 when bi-amping since the circuit is also responsible for phase rotation. They further recommended the crossover points to use with an active crossover, which is why I chose what I did.

As for the rest of the crossover, I wasn't ready to purchase two more amps (total of 4) and try to set up a 4 way active crossover as a replacement for the oassive crossover. Technically, what I have is considered a hybrid arrangement, but it works extremely well.

For your project, I would definitely bypass the passive crossover: leave it physically in place but electrically disconnect them for the active crossover.

[onplane]

>As odd, and wrong as it may sound, yes, the passive crossover

>is still present.

>

> As for the rest of the crossover, I wasn't ready to purchase

>two more amps (total of 4) and try to set up a 4 way active

>crossover as a replacement for the oassive crossover.

>Technically, what I have is considered a hybrid arrangement,

>but it works extremely well.

>

>For your project, I would definitely bypass the passive

>crossover: leave it physically in place but electrically

>disconnect them for the active crossover.

Hi, Richard!!

Well, that's the problem with a 4 way system ... tetra-amping!!

Geez, I can see why you elected NOT to go this route.

Actually what I am doing right now is very similar to what you are doing. I don't have an active xover, but I use tone controls to discard MOST (not all) of the unwanted frequencies. That is, I send very little high frequencies to the woofer (it does, however, get plenty of mid-range). Then to the mid/tweeter I send no fundamental frequencies (by turning the bass control full OFF). I've further verified by watching current going to the respective units that I'm not discarding too much and that the internal xovers are rejecting the unwanted frequencies.

I agree, the next step for me is to go full active. I just don't know if the benefit of doing so is worth the effort. My speakers sound better right now than ever and I'm a little afraid of going backwards.

Regards,

Jerry

[rrcrain]

I used the Marchand XM26 crossover but for your project, their XM126 would be a better choice.

http://www.marchandelec.com/xm126.html

You can get it as a 2, 3, or 4 way crossover and it appears to be identical to the XM26 except for the added crossover points. It's far from inexpensive and if your like me, your going to consider it for a year or more; check out opinions, feedback and writeups on the product and company. I even downloaded and studied the assembly manual before I made a decision.

Good luck, and have fun.