Author Topic: 115V Cabinet Build w/ Altec 421A  (Read 7463 times)

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Offline Greg_M

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115V Cabinet Build w/ Altec 421A
« on: December 28, 2011, 12:02:28 pm »
I have a couple Altec 421As without a home. I wonder they would work in that cab?
I was thinking of two cabs instead of one, just so I would only have to lug one, if I could get away with it
« Last Edit: December 29, 2011, 12:32:06 pm by EdBass »

Offline Jeff Troy

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Re: Re: 115V Cabinet Build
« Reply #1 on: December 28, 2011, 05:53:00 pm »
Hi, Greg,

I had 421As in my 2000S cabinets back then. They sounded great at lower volumes, but real farty when you cranked the heads. Sometimes the farty sound was very cool.

A single 421 in that cabinet with a Concert Bass or 200S or similar sunn toobie would most likely sound excellent for small cub or home studio work.

Still need the drawing?

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Offline Greg_M

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Re: Re: 115V Cabinet Build
« Reply #2 on: December 28, 2011, 08:06:38 pm »
I was thinking of solid state for the amp for the 421(s). The best rig I ever had was solid state (Tapco) and four 421s in two cabinets. Everyone always bitched about it being too loud ( I liked having that problem)

Yes on the drawing, but again, no hurry. I have a project or two in line before them (but who knows)

 I was thinking if you made two single 15 boxes you could stack them port to port if you wanted/had to.

Offline loudthud

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Re: Re: 115V Cabinet Build
« Reply #3 on: December 28, 2011, 08:10:38 pm »
Altec 421As always sound farty in reflex enclosures. XMax is only 0.05 inches. In other words, the voice coil can push the cone really hard but only for a short distance. They work best in horn enclosures where they can leverage the high throat pressure into some big sound waves. If you like clean low frequency bass in small packages, go with something else IMHO.

Offline Greg_M

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Re: Re: 115V Cabinet Build
« Reply #4 on: December 28, 2011, 10:34:48 pm »
I've heard that said before.
But keeping in mind that 0.05" is less than 1/16" (0.0625) I can assure you that the ones I played through, travelled much further.

Maybe mine were special

If you check the Altec brochure http://www.lansingheritage.org/images/altec/specs/components/421a/page2.jpg
You can see that the excursion distance is 1/2" (0.50") which I can tell you from experience is more accurate.
I think it more sensible (since I have owned them and played through them and watched them, built cabinets around them  etc etc etc) that somewhere along the line someone mis-wrote or inverted the figure and it has been repeated since without verification. Maybe they just didn't know how to read decimal measurements

I also discovered that quality of amplifier had a lot to do with what sound came out of the speaker(s)
Coloring aspect aside, I found well designed transistor amps had much better control (of excursion), than tubes, for bass (as much as I love my dynaco/sunn amps).
I'll take my McIntosh any time for listening to music, but as I have witnessed, a few hundred watt transistor bass amp was the best I played through.

Not to sure what the term "farty" means.
Another thing that had an enormous effect is how the equipment was run (settings). Nobody played the bonky, trebley bass then, as they do now, so I can see that if you were trying to get something out that they were not designed to do, it might not work out to well.

 

Offline CLD

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Re: Re: 115V Cabinet Build
« Reply #5 on: December 29, 2011, 09:33:22 am »
Gee, I thought "farty" was a widely recognized technical term! I'm sure you'd recognize it if you heard it ...  :-D

I'll take those photos and measurements this afternoon. Sorry for the delay, the holiday festivities have gotten in the way of my Sunn-related activities!
Sunn since June 1971!
1971 Sorado, 2000S, Coliseum Bass, Coliseum Lead
1970 200S; 1974 Coliseum 880

Offline EdBass

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Re: Re: 115V Cabinet Build
« Reply #6 on: December 29, 2011, 10:31:51 am »
I also discovered that quality of amplifier had a lot to do with what sound came out of the speaker(s)
Coloring aspect aside, I found well designed transistor amps had much better control (of excursion), than tubes, for bass (as much as I love my dynaco/sunn amps).
I'll take my McIntosh any time for listening to music, but as I have witnessed, a few hundred watt transistor bass amp was the best I played through.

Transistors over tubes?!?! Pure heresy!  :-o :-D

I’ve always been of the school that the natural compression inherent in tube output stages did a better job than transistors of “calming” those transient peaks that cause speakers to do make weird noises.
Of course, by “well designed” maybe you mean designed with a built in compressor as many bass specific SS amps are.
 


I see that Altec spec sheet, and I see the 1/2" "excursion" rating, but I'm a little confused as to how it relates to current Theile-Small driver ratings. I suspect that Altec's "excursion" rating is not the (now) industry standard T/S "xmax" rating which has been the standard since the mid-late 70's.
Xmax is the point where the voicecoil begins to leave the magnet gap, driver output becomes nonlinear and mechanically induced distortion can start rearing it's head.
Or... half of the VC height not including the top plate thickness.

A .5" (12.7mm) "xmax" would be huge, particularly for a 15" woofer in that era; so huge in fact that I don't see how Altec's "excursion" and T/S's "xmax" could possibly be the same rating. Even if Altec is including incursion with their "excursion" measurement, or "xlim"; the point of mechanical failure or maximum cone travel before the VC comes completely out of the gap or hits someting on the top or bottom, 12.7mm would be impressive IMO.
For comparison, a  JBL K140 has an xmax of 5.08mm (.2"), and that's generally considered to be a quite "generous" excursion for a woofer from that era.

The biggest xmax of any woofer that I am personally aware of is the CV 18" and 21" "stroker" subwoofers at 15.9mm (.626"). It has a claimed 108dB sensitivity 1W @1M in a folded cab.
Anyway, keeping the VC aligned with that freakishly long 1/2"+ linear excursion requires three spiders; two at the VC, one inverted, and a third where the dust cover normally is, mounted to a fixed shaft that runs through the magnet.



So, it's my guess that Greg and 'thud are just on "different pages of the same book".  :wink:

Gee, I thought "farty" was a widely recognized technical term! I'm sure you'd recognize it if you heard it ...  :-D

I'll take those photos and measurements this afternoon. Sorry for the delay, the holiday festivities have gotten in the way of my Sunn-related activities!

By my definition, "farty" or "farting" is caused by a speaker being driven past its safe excursion, flirting with "xlim", causing the travel to become nonlinear and the cone assembly making contact with the magnet structure; even sometimes bouncing off the bottom of the VC gap on the "incursion" phase of cone travel.

It sounds kinda like... well farts; an intermittent burpy/popping sound.


Also, this thread is getting way off topic (and my contributions to it are largely responsible  :-D) so if we continue down the path away from Jeff's nice 115V build I'm going to split the topic.     

Offline loudthud

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Re: Re: 115V Cabinet Build
« Reply #7 on: December 29, 2011, 11:09:09 am »
Maximum Cone Excursion is not Xmax. You don't see any other Thiele Small parameters like Qts or Vas because that sheet is the Architects specifications (an old term for marketing hype). I was always amused by those because of statements like "The musical instrument loudspeaker shall be ALTEC Model 421A". Here's a link to actual Thiele Small parameters. http://www.greatplainsaudio.com/altec_thiele_small.html

Offline EdBass

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Re: 115V Cabinet Build w/ Altec 421A
« Reply #8 on: December 29, 2011, 12:28:10 pm »
Maximum Cone Excursion is not Xmax. You don't see any other Thiele Small parameters like Qts or Vas because that sheet is the Architects specifications (an old term for marketing hype). I was always amused by those because of statements like "The musical instrument loudspeaker shall be ALTEC Model 421A". Here's a link to actual Thiele Small parameters. http://www.greatplainsaudio.com/altec_thiele_small.html

Of course, another reason for the lack of T/S parameters could be because there were no T/S parameters when that spec sheet was written?
I'm not up enough on my Altec Lansing history to know when the 421A was actually designed or in production, but actual  T/S parameters  weren't published until the mid - late 70's.

There are also some discrepancies between the current T/S parameters and the the spec sheet referenced by Greg; most notably the actual model designation, and also of particular interest IMO the Fs, which is listed at 40hz on the spec sheet because that is a very easy parameter to measure accurately.
So while it may just be marketing hype to enhance the 421A as a full range driver rather than a dedicated woofer, which might be a stretch considering the "dive" at 5K on their graph, I'm not sure why they would "fudge" the Fs upwards from the T/S parameters.

Maybe we are actually talking about two different drivers?

Offline loudthud

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Re: 115V Cabinet Build w/ Altec 421A
« Reply #9 on: December 29, 2011, 03:39:05 pm »
Maybe we are actually talking about two different drivers?

Could be Ed. Notice in the link I posted there is a 421-8H, 421-8H II and a 421-8LF. Curious that there is no 421A listed, but all those that are have Xmax at .05 inch.

I had a Sorado cabinet around 1970. It had a pair of 421s in it driven by an Ampeg B25T. One day I discovered that one of the speakers was dead. The voice coil measured open. So, being curious I cut the cone out of it. The voice coil was only about a half inch long. Had it reconed at a place on Sandy Blvd in Portland. The guy used an after market kit and tested it by playing a 1 watt radio through it. The voice coil rubbed when you played bass through it. I had to drag my amp and speaker box down there to demonstrate the rub so he would recone it again.

Offline Greg_M

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Re: 115V Cabinet Build w/ Altec 421A
« Reply #10 on: December 29, 2011, 05:09:35 pm »
I think the "excursion" rating of that era include inward and outward travel. So 1/4" in and 1/4" out.



I got the idea that transistors had better control from Greg Mackie who I went to HS with. I thought it heresy as well. Him and Martin were just starting Tapco then. I wanted a big tube amp but he talked me out of it. Him and Martin hand built the rig. When I tried it out I went out on the front porch of their house in Mukilteo with my EB-3 while they turned it up and listened to it. Four 15s in two cabs and a lot of juice in the front room. They were delighted and eventually I was too. It reminds me now of that film Jackass where guys do stuff to hurt themselves. I'd hit a note and they let out a yell and adjust something and say do it again. I thought that rickety old house was going to shake apart

Previously they had talked me into a 30" EV in a huge box and a Dynaco Mk3. It didn't work that well but it sure got a lot of second looks. Eventually the 30" self destructed and they felt bad so I think the four 15 setup was to make up for it a little
« Last Edit: December 29, 2011, 06:04:02 pm by Greg_M »

Offline Greg_M

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Re: 115V Cabinet Build w/ Altec 421A
« Reply #11 on: December 30, 2011, 10:10:12 am »
Now here's something you don't see everyday (or care too)

The first band I was in called the Marquis. June 1966. I'm second from the right and would have been 15. A Gibson EB-0 through a Fender "Bassman"

I think I remember what farty is......


Offline Johnny Guitar

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Re: 115V Cabinet Build w/ Altec 421A
« Reply #12 on: December 30, 2011, 11:05:22 pm »
Groovy outfits!!!   8-)  That picture is priceless, I think its cool that you have it. 

In 1970 at 15 I played at a neighboring schools Home Comming.  I was wearing white bellbottoms and an American Flag shirt with blacklights across the front of the stage.  No pictures though. :-(

Greg did you ever play in Indianapolis?  In the late 70's I saw a band in a small club and the Bass player had a 30" speaker.  I thought it was awesome, his bellbottoms were swaying in the breeze of air from that speaker!

Johnny G.

Offline Greg_M

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Re: 115V Cabinet Build w/ Altec 421A
« Reply #13 on: December 31, 2011, 09:14:51 am »
We never got out of western Washington State.

My mom made the ruffles for those shirts out of bed sheets. We were inspired by Paul Revere and The Raiders.  :-D