WE 755A

[Clark B.]

Xavier,

I just got 2 sets of Altec 755c's and I'll send the person who gave them to me a set of these installed in cabinets in order to earn the second set for myself...

Was also thinking of presenting the same offer to the person who is willing to purchase 2 sets of Feastrex D9 Monster Alnico drivers and give me one set of them in return for some absolutely awesome cabinets for the owners' pair.  Word on the street is that this particular model is very affordable right now as the permanent magnet versions are being discontinued in favor of an all electromagnet product lineup.  I, however, am privy to the fact that these MA's are really really good sounding.  And I also already own an electromagnet 5," so why not round out the stable a little? 

I bring it up to you though as if you like the 755, then a 9 inch Feastrex will just flat blow your socks off.  (but hopefully not your budget).   They too get right to the heart of the music, but they just have immensely greater resolution, dynamics, and are also non fatiguing.  The 755 actually served as inspiration for the Feastrex designers, so much to the point that their "Type I, II, or III" electromagnet circuits are almost the same shape as the 755 electromagnet.

I worked with the Line Magnetics 755 electromagnet last year and it was alot of fun, actually.  My initial impressions were somewhat luke warm in terms of their price to performance ratio, (and lack of high frequency extension/refinement, and minor hiccups at 3k)...(however...don't get me wrong I VERY much enjoyed the musical things that those drivers did well!!!)  And you are so right - that they make themselves easy to listen through their faults.  Good points that outweigh the bad.  And it seems that the speakers I built have improved greatly anyways after a full breakin process.  Enough so that I've reconsidered the situation that I probably owe it to the driver model to give them another chance. 

So we'll be making an aperiodic for the 755c's we've gotten in.  Should be a fun project.  I like classic audio sound very much.  It is so important as a designer for me to keep one ear turned back to history in order to effectively shape the things to come in single driver technology.  So I've embarked on these classic speaker cabinets in the manner that I am definitely looking towards the future - to do justice to the Feastrex 5"s and 9"s.   

Cheers!

-Clark

[xcortes]

Hi Clark,

I've never heard the Line Magnetics one but I have had several pairs of Es and Cs in the past. To be very candid with you there's no comparisons between the E/C and the As. My As are WE and have not really heard the Altec As. The E and Cs are nice but they are not magical as the As. Neither they go as "high". They need a tweeter. Two different ball games imho.

I've never heard the Featrex either. So i can't comment. Hopefully the good pricing moment lasts for a few months and I may be able to think about it.

Saludos

[Paul Joppa]

Xavier, I think the 200Hz dropout is a ground reflection - unless you tested these 20 meters into the air at a test distance of 2 meters!. An experimental test is to turn the speakers upside down and see if it goes away (or moves to a higher frequency).

The combination of speaker rolloff, ground reflections, and baffle step effect makes it difficult to easily interpret what you see below 500Hz. All of these effects are calculable, and can even be done in a spreadsheet, but it's a pain in the backside to actually do it. I have not done so myself, because you still have the effects in a real room, with the addition of all the wall and ceiling reflections - a.k.a. "room acoustics"!

72mS is 25 meters, not centimeters. Is there a house 12.5 meters away that might produce a reflection?

Other possible causes are edge diffraction (look for the shareware "edge" program to explore this more easily), or the back-mounted speaker. That short wide tube in front of the speaker is amazingly effective at coloring the sound.

[Doc B.]

PJ and I have set cabinets up on a step ladder to shift the ground reflection around a bit. IIRC we got some amazingly smooth bass response curves with that method. Shoot it once at regular height, then raise the cabinet on something that is "acoustically skinny" like a ladder and shoot it again. Check to see if the suckout shifts position.

[xcortes]

Thanks PJ and Dan!

Thinks are starting to make sense. The 200hz dropout absolutely has to be a floor reflection. If I input to this calculator:

http://mehlau.net/audio/floorbounce/

the parameters of my speaker and measurement distances I get a first cancelation at 277hz!

On the high end one there's my kids slide and playhouse just behind where the mike was and very likely around 12.5 m behind.

And yes, these big boxes are more colored than the good old WE slant boxes partly maybe from the wave in front of the driver and partly from being more resonant. And I'm really not gaining bass.

Still a lot to learn!.

Saludos!

[xcortes]

Last night I put the speakers back in the WE slanted boxes.

No measurements now. Just listening. First, they are much less colored. As Paul suggested the wave in front of the rear mounted driver does color the sound. I don't think I was getting much benefit from the big boxes since there's no hump on the response on the "small" ones and there was not perceivabable nor measured increase bass with the big ones. In could front mount the speakers on the big ones but I think the experiment is over.

I have a cool new experiment to try. I just remembered John Swensons old posts about a high impedance amp, he suggested 2 times vas. I have a pair of Lowther dx3 that has a vas of 45 liters. I can jusr drop them in this 100 liters boxes and connect them to the big pre that has 50, 200 and 500 ohm taps at around 1.5 watts. More fun!

Another finding. I believe that with the WE the Paramount 300b sound thin compared to the 2a3 ones. I'll put the 2a3 in today to confirm the observation.

[xcortes]

Only two moths lasted my life without horns. Yesterday I put them back. They are sounding amazing after initial adjustments. The good thing is that the WE can jump in anytime without taking the horns back.

Taking the horns out allowed me to rearrange the room and to do a few other adjustments that altogether were worth the effort of taking everything off and back again. I did learn a lot and it's reflecting in the sound.