Przem's Phase Linear 700 Series II White Oak Conversion

[Northwinds]

More on the recent discussion: Audio magazine, April, 1976. pp. 44-56. By Richard S. Burwen

[...] Each of the five speaker horns is 13 ft. deep and has about 64 sq. ft. of mouth area. [i.e. 8 foot x 8 foot] The horns are conical, in preference to exponential, in order to produce a gradual low frequency rolloff, instead of a sharp cutoff. As it turned out, due to reinforcement from the room, the average low frequency response on one third octave bands is flat down to 16 Hz without equalization.

Each speaker horn contains 30 Cerwin-Vega tweeters, a midrange horn with two JBL 2440 drivers, and two Empire 16 in. woofers. In addition, the left-front and right-front horns have two 24 in. Cerwin-Vega woofers, mounted on the doors. These woofers are equipped with feedback windings to linearize their acoustic output over their range.

The rear speakers, which are shown diagrammatically in the room plan, point towards the rear of the room so as to provide reflected sound....the storerooms between the front speakers constitute a 200-cu. ft. back enclosure. The rear speakers vent into the room at the ceiling level in the manner of a bass-reflex speaker....

The entire room is solidly constructed of concrete, cinder clock and extra heavy plaster. Although the horn walls are made of 4-in. filled cinder block, I am amazed at how much these can vibrate. If I were to build a room like this again, I would use 8-in. thick walls.

The ceiling is wavy so as to diffuse the sound and the low points of the ceiling conceal heavy steel beams which support the house above.

Phase Linear-400 amps To drive these speakers there are a total of 17 Phase Linear 400 amplifiers [200 watts RMS/channel @ 8 ohms].... Each woofer, midrange horn, and set of 9 or 12 tweeters is driven from one 200 watt amplifier channel. With the electronic crossover at 50, 400 and 5,000 Hz ahead of the amplifier, the speakers can produce the same sound level that would be produced by a single 20,000 watt amplifier.... The crossover filters utilize UM201 modules to produce 6-, 12-, 18-, and 30-db/octave cutoffs for the various drivers. In addition, the crossover provides equalization to lat acoustic response.

In designing and adjusting the crossover network, I used one-third octave noise measurements based on a six microphone average of omni-directional microphones for low frequencies and an average of two cardiods located in from of the left-front and right-front horns for high frequencies. The microphones used for adjusting the crossover frequency response are the same ones used for making recordings here, so the entire system is flat. On one-third octave noise bands, it measured flat within 1 1/2 db from 15 HZ to 20 KHz. Nevertheless, I find that when reproducing much of the prerecorded program material availible I use from 3 to 30 db of low frequency boost.

When you have a high powered sound system like this, one of the difficult problems to solve is to keep from blowing out 169 speakers at once. That is the reason for having so many speakers in the first place. The tweeters are wired three in series so that each can receive only 1/3 of the amplifier output voltage. All the speakers can handle the clipping levels of their respective amplifiers without mechanical damage. Nevertheless, during sustained clipping the voice coils can get too hot. To prevent overheating, there is an elaborate speaker protection system in each of the rear horns and one for the three front horns. The protection system has a total of 34 channels, each of which measures the amplifier power output, computes the voice coil temperture and disconnects its speaker with a relay before the voice coil gets too hot. The same system eliminates turn-on and turn-off thumps. In over a year of operation there has been no damage to any of the speakers. [...]

And in addition, an interesting short article on ‘why to upgrade your system with electronic x-overs’… - http://scrounge.org/speak/dynamic.htm

That is just straightup crazy!!!! I would worry about all the nails and screws in the studs starting to back out from vibration LMAO!!!

 

[laatsch55]

Yep....A very real concern.....even at my house....

 

[laatsch55]

Ive spent the last 20 years going to concerts. This home audio shit is still a new thing to me. I've had my technics sp-15 for years. But other than that it's been get me by best buy crap. So there's a lot I don't know about

What's the best system you've heard so far?

 

[Northwinds]

What's the best system you've heard so far?

Loaded question LOL

I think it would be tough to beat what he has now but for those with deep pockets, I suppose the sky is the limit but then the Law of Diminishing Returns comes into play...

 

[Skynyrd77]

What's the best system you've heard so far?

The flat out best sounding I have heard was in Chicago . Cary ss amp,modwright pre, rotel cd. But that was 18k worth of shit also and in a room for sound. I heard some new mcintosh stuff in south bend but again 12k worth of shit in a listening room. Real life situations has been my setup now. So I'm prob more struck by the sound room then the gear. Make any sense??

 

[Northwinds]

The flat out best sounding I have heard was in Chicago . Cary ss amp,modwright pre, rotel cd. But that was 18k worth of shit also and in a room for sound. I heard some new mcintosh stuff in south bend but again 12k worth of shit in a listening room. Real life situations has been my setup now. So I'm prob more struck by the sound room then the gear. Make any sense??

I never did ask Jason but did he crank that stuff to concert levels? That would be the test. Anything can sound great at lower levels in a sound room. Put the gas to it and see if everything works the same. I would discount the Rotel right off the bat, I just don't see a CD player sounding THAT much better then a good quality less expensive player. I would put my dbx DX5 against any CD player. If it means I have to spend a grand to sound incrementally better, I would not bother

 

[Northwinds]

I just looked at the specs of the Cary SA-200.2 and don't see it being better then a FC WOPL at all....

 

[Skynyrd77]

I never did ask Jason but did he crank that stuff to concert levels? That would be the test. Anything can sound great at lower levels in a sound room. Put the gas to it and see if everything works the same. I would discount the Rotel right off the bat, I just don't see a CD player sounding THAT much better then a good quality less expensive player. I would put my dbx DX5 against any CD player. If it means I have to spend a grand to sound incrementally better, I would not bother

It was a hundred wpc Cary ss. And he got on it pretty good. If you ask me the WOPL is every bit as good as that Cary . But the pre is where I feel I could do better. And as cdp's go his was 8k so it had to of played a part.. The CD player was more than the amp or pre!! Lol

 

[Skynyrd77]

This is the pre I won't shut up about lol.
http://modwright.com/products/ls-100-tube-preamp.php

 

[P.L.F.]

I wonder if this approach proposed by Nick (THD+N): http://www.audiokarma.org/forums/showthread.php?t=310160&referrerid=56853 can become a 'standard' add-on to the WOPL conversion for those having two identical amps?

No advice or comments? Can't believe, not in here!

 

[Northwinds]

No advice or comments? Can't believe, not in here!

What about the heat generated? From what everyone has said, these amps should never be bridged

 

[laatsch55]

Przem, it can be done. There is some debate as to whether it would live an hour or a day...

 

[Northwinds]

Przem, it can be done. There is some debate as to whether it would live an hour or a day...

I know with the Amber 70s, they got so freaking hot in bridged mode. One made it a month. Some amps just are not made to do some things. I later found out this was a no no... I could have just used one channel on each amp to run each speaker but I had to go all out and that's what happens when you have no clue what your doing. That was the last amp I have blown up. The WOPL's are formidable beasts but they just don't have the heat dissipation needed to be able to run like that for any length of time and survive. I imagine the thermal fuses would trip first. I don't remember if the Amber's had thermal protection but either way, it did not help

I still feel guilty about blowing that amp up but man did it sound good before it bit the big one

 

[P.L.F.]

Przem, it can be done. There is some debate as to whether it would live an hour or a day...

Not for me Lee. My speakers are 5 ohms of impedance nominal (http://www.thevintageknob.org/jbl-Ti5000.html)... Bi-amping & bridging would burn something for sure... But for more than 8 ohms? Worth of trying on one of PL700 'test' gears, if available from a Forum Member?

 

[P.L.F.]

What about the heat generated? From what everyone has said, these amps should never be bridged

Always with cooling fans on... !

 

[Northwinds]

Always with cooling fans on... !

Dude, I had a big box fan on them on high

 

[laatsch55]

Not for me Lee. My speakers are 5 ohms of impedance nominal (http://www.thevintageknob.org/jbl-Ti5000.html)... Bi-amping & bridging would burn something for sure... But for more than 8 ohms? Worth of trying on one of PL700 'test' gears, if available from a Forum Member?

One of these days when.i have some time.

 

[P.L.F.]

Dude, I had a big box fan on them on high

Practical on winter time, it can be cold and snowy in Connecticut I suppose ...
By the way, same here. And a fireplace becomes old-fashioned, so let's go for WOPL, even not bridged! A new dimension of your "What do you mean it's too loud?"...

 

[Northwinds]

Practical on winter time, it can be cold and snowy in Connecticut I suppose ...
By the way, same here. And a fireplace becomes old-fashioned, so let's go for WOPL, even not bridged! A new dimension of your "What do you mean it's too loud?"...

I used to have a picture posted here of Blackie wearing her giant ass fan LOL. I literally lay the fan blowing down on top of the amp(s). I don't have that problem with the FC 400 since Jer installed a custom fan set. Works great, fans are going at least a couple times a day when I am cranking the living fuck out of it playing along with my guitar and tube amp

 

[premiumplus]

I know with the Amber 70s, they got so freaking hot in bridged mode. One made it a month. Some amps just are not made to do some things. I later found out this was a no no... I could have just used one channel on each amp to run each speaker but I had to go all out and that's what happens when you have no clue what your doing. That was the last amp I have blown up. The WOPL's are formidable beasts but they just don't have the heat dissipation needed to be able to run like that for any length of time and survive. I imagine the thermal fuses would trip first. I don't remember if the Amber's had thermal protection but either way, it did not help

I still feel guilty about blowing that amp up but man did it sound good before it bit the big one

Isn't it funny how they always sound their best just before they go up in smoke? Every time I'm playing guitar and think my tone is stellar I start worrying about the amp getting ready to blow. It always seems to happen with tubes...they sound great just before they fail.