Who has actually done the A7 Kitty Litter Bass Horn bracing.

[GM]

You're welcome! I'm surprised you still aren't using the RCAs.

GM

[LowOhms]

I was moving, sold all the six Ubangies, and the field coils and horns. I am JUST as happy, so far, with ALTEC drivers, that tell the truth, are VERY uncolored, and I may prefer them over the RCAs, don't know quite yet, need to finish setting up my A7-800 system.

UPDATE as of 1-31-2016 : In the last two days, at Lowe's ( hardware chain ) I have purchased 36 pieces if red-colored concrete, 11.7 inches by 11.7 inches, by 1.7 inches thick, which I will be placing on top of my STOCK 825 enclosures, to mass load them. The "red" slabs are only $1.78 each, and a gray concrete colored slab is only $1.48 each, I LIKE the looks of the red, aginst the gray ALTEC box, and in my living room.

I have been continuously listening to various weights on top of the STOCK boxes, using 53 pound multiple boxes of L.Ps, my collection of heavy ( low DCR ) power transformers and chokes, bricks, and now, these red Concrete flat " foot square-roughly " concrete blocks. I THINK these will be my solution, to get these A7s to perform, without modding the stock 825 box. Each block weighs 17.6 pounds, give or take an ounce, so 18 per side will be adding about 316.5 pounds per box. THAT will stabilize it. AND, its easy to manipulate 17.6 pound concrete blocks, one at a time, and, they look pretty. Most will be in the rear, in back of, and on either side of the high frequency horn, and over the woofer's rear-wave compression chamber. I'll post initial and final photos as I work on this.

Having 'lotsa fun, LISTENING to all these A7 box changes, with my newest DC Type 45 SET and newest triple-12 AWG speaker cables, it lays it all out in bold relief !! FUN !!

Jeff Medwin

[GM]

While RCA has its followers, they didn't fare well around here, so managed to pick up a quite a few for scrap prices in the mid '60s. Their steel was first rate though, so we had them turned into thin coils to stamp out small armature blanks, never having a clue in our wildest dreams they would ever be high end collectibles and frankly, multi-cells too, so usually sold for scrap as the big cinemas were either downsized or converted to something else. In '69, the [3] tar filled 805/288Bs and [4] 210 cabs [sans wings] cost me the princely sum of two six packs of Pabst Blue Ribbon beer for the two workers that brought them to our new house on their way home, even helping me move them into the 'great' room.

Hmm, thought I'd mentioned it here, but a 'must do' mod if not using a large horn 'sled' screwed to the top is to add a full size ~3/4" no void plywood top plate to stiffen up the horn, ditto on its bottom side. heavy mass loading or not, at least in theory it won't necessarily stop the cab's large panels from flexing, so a bit of bracing is a good plan long term. In my teens, I was at a country music concert in a small local cinema where I could hear/see what I would later learn were inverted A7-8s setting on the stage vibrating, 'talking' to me/us even with the horns 'in my face' during a Sonny James' set, subconsciously teaching me a valuable lesson I would recall later when designing speakers, shipboard electrical controls and seismic rated switchboards, panel boards, motor control centers for several different nuclear reactor power plants.

Of course, I doubt you'll ever play them this hard, but these stock cabs are acoustically pretty 'loosy-goosy' as you've found out via mass loading them, so not much cost/effort just in case all this extra weight proves too much for them long term.

GM

[LowOhms]

While RCA has its followers, they didn't fare well around here, so managed to pick up a quite a few for scrap prices in the mid '60s. Their steel was first rate though, so we had them turned into thin coils to stamp out small armature blanks, never having a clue in our wildest dreams they would ever be high end collectibles and frankly, multi-cells too, so usually sold for scrap as the big cinemas were either downsized or converted to something else. In '69, the [3] tar filled 805/288Bs and [4] 210 cabs [sans wings] cost me the princely sum of two six packs of Pabst Blue Ribbon beer for the two workers that brought them to our new house on their way home, even helping me move them into the 'great' room.

Hmm, thought I'd mentioned it here, but a 'must do' mod if not using a large horn 'sled' screwed to the top is to add a full size ~3/4" no void plywood top plate to stiffen up the horn, ditto on its bottom side. heavy mass loading or not, at least in theory it won't necessarily stop the cab's large panels from flexing, so a bit of bracing is a good plan long term. In my teens, I was at a country music concert in a small local cinema where I could hear/see what I would later learn were inverted A7-8s setting on the stage vibrating, 'talking' to me/us even with the horns 'in my face' during a Sonny James' set, subconsciously teaching me a valuable lesson I would recall later when designing speakers, shipboard electrical controls and seismic rated switchboards, panel boards, motor control centers for several different nuclear reactor power plants.

Of course, I doubt you'll ever play them this hard, but these stock cabs are acoustically pretty 'loosy-goosy' as you've found out via mass loading them, so not much cost/effort just in case all this extra weight proves too much for them long term.

GM

Dear GM,

Dennis Fraker, ( Cinema Design ) who has owned MANY MANY MANY A7s, ( he would use eight in a small theatre ), has advised me NOT to add panels to these 825s with too-thin 5/8 ths enclosures, ( not that they don't need it !! ). He says, there will be voids when DIY adding panels, which sound terrible.

So, I am TRYING to leave the box stock, and do REVERSIBLE mods. If I like it all ( which I expect I will ). I do have one inch Baltic birch, EuroPly, (five) five by five foot sheets, and I can perhaps do a from-scratch A7 out of that. But, I may just listen to music with the mass loaded 825s !! :-) THANK YOU for all your help.

In 2014, I was GIVEN these 515Bs, and 802Ds, and 511 Horns, and in 2016 I was GIVEN the 825s, from two different local Kansas City audio friends I had "mentored" over the years in amp building. I swapped-out the 511 horns for the equivalent of Emilar EH-500s, and 1 inch to 2 inch adapters, so my overall $$ outlay is minimal.

'Am getting back to the 604B sound my Dad had in our recreation room when I was 8 years old, many decades ago.

I am liking the horn loading on the 515Bs, as I improve the boxes.

My amp has real drive into the load, all 1.5 Watts. I use the equivalent of 9 AWG internal wiring in my amp, and I am able to switch OUT the Thermistor and fuse, for " attended listening". Serious attempt for " maximum dynamics " while maintaining that glorious Type 45 DHT's pristine sonics. Fun. Much fun.

Jeff Medwin

[mah]

I just had to add this HESA thread. Relative Altec content but the reply by Merdy is a gem.

High Efficiency Speaker Asylum




P.S. Over the years I have noted many attempts to turn an Altec 825/828 with 416/515 into a high-end reproducer for in-home use. I don't believe anyone really succeeded.

Ultimately the cabinet's flimsiness, truncated horn and mismatched bass relex performance are inherent qualities working against the design for critical HiFi listening.

The Exemplar project was an attempt but showed what was required in attempting to turn a 'sow's ear' into a 'silk purse'. It was no longer a VOTT.

Exemplar Project: Sound Practices Article Reprints Download SP VOL1 #4 article.

PS The Small Vott was designed for use in smaller commercial theatres with the intention of providing, through a perforated projection screen, reasonable audio coverage across the audience seating area. It did what it designed to do very well. It was never designed to do any more than that. It did find its way into other commercial applications but not HiFi.

There are better ways to utilise Altec transducers in the home for critical listening.

[Phil-G]

I just had to add this HESA thread. Relative Altec content but the reply by Merdy is a gem.

High Efficiency Speaker Asylum

merdys comment is priceless.

[kwingylee]

Hello GM !!!

I am having a LOT of fun hearing ALTEC all over again. For the last eight years, at RMAF audio shows, I have listened to a GPA 604 MLTL YOU computed for Dennis Fraker in Montana, driven by his Serious Stereo 2A3 amps, to good effect. Dennis reports to me, your math and design work was meticulous and "perfect !! "

[B]Here is what I wanna tell ya all. I am " coming back" to ALTEC ........

This is my testemony. I want to thank you GM, for helping Dennis, and all of us up here. Its going to be a LOT OF FUN, to hear ALTEC again, especially with better wire, amps, and implementations than as a child.

Jeff Medwin

So Jeff, do you know if Dennis displayed/demo his MLTL speakers at the RMAF 2015 with custom made 300b amps? These were in fact designed by GM?

[GM]

He seems to have moved on...........: http://www.audioasylum.com/cgi/vt.mpl?f=hug&m=175268

GM

[LowOhms]

He seems to have moved on...........: http://www.audioasylum.com/cgi/vt.mpl?f=hug&m=175268

GM

Hi GM !!

Yes, and I have moved on, since then.

I discovered last week the crossover pictured needed about 12-14 pounds of added mass loading ( three regular bricks are about right on mine ), it develops a SWEET SPOT, and the A7 VOTT system plays ( a) louder (b) clearer (c) more dynamic !!

I had to SUBTRACT that added crossover weight from the mass loading I did on the flimsy 825's plywood 5/8ths thick enclosure.

My Type 45 DC SET is now up to SIX bricks, as of two nights ago. Clearer and better sounding that way ( versus five bricks previously ) . ALL my components seem to respond to proper mass loading, my ATTENUATOR certainly did, big time !!!

FUN stuff to discover. Working now - next - on film bypassing of my main crossover caps, and I'm making a permanent " mass loading platform " for the crossovers, above their L and C components ( a " flat roof " ).

Jeff Medwin

[kwingylee]

Hi GM !!

Yes, and I have moved on, since then.

I discovered last week the crossover pictured needed about 12-14 pounds of added mass loading ( three regular bricks are about right on mine ), it develops a SWEET SPOT, and the A7 VOTT system plays ( a) louder (b) clearer (c) more dynamic !!

I had to SUBTRACT that added crossover weight from the mass loading I did on the flimsy 825's plywood 5/8ths thick enclosure.

My Type 45 DC SET is now up to SIX bricks, as of two nights ago. Clearer and better sounding that way ( versus five bricks previously ) . ALL my components seem to respond to proper mass loading, my ATTENUATOR certainly did, big time !!!

FUN stuff to discover. Working now - next - on film bypassing of my main crossover caps, and I'm making a permanent " mass loading platform " for the crossovers, above their L and C components ( a " flat roof " ).

Jeff Medwin

Jeff:
God bless you man, you solutions have ZERO chance in my home... my wife, bless her soul and she is super tolerant, will throw me out if I try any of your options.....