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

[LowOhms]

In addition to GM, WHO has done the full banana " fill the A7 bass horn curved flairs with Kitty Litter " modification ???


GM explains it both (a) infinitely braces of the thin curved panels, and (b) that it mass loads the enclosure beneficially. Makes sense !!

Q1. : Has anyone done Kitty Litter of the A7 bass horn flares?? ( besides GM )

Q2. : What was your experience in (a) actually doing it and (b) your before and after LISTENING description ?



Comments welcomed - IF you have direct experience doing and / or listening to this. Thanks !!

LowOhms Jeff Medwin

[LowOhms]

Hello,

Its been a month and NO ONE has replied. Fine. Last night ( 11-30-2015) , I had my FIRST opportunity to hear my 515B in a single A-7 ( 825 box - stock ) in my home listening environment.

NO tweeter, just a cleaned-surround 515B well-wired with double 12 AWG Mil Spec wire ( equals 9 AWG ) to each terminal. Driven by a 1970s Harmon Kardon 330C receiver, as a temporary start-up, 'till I add my Type 45 SE DC amp, etc., later this month.

Here are "my" first-night listening impressions, after living with same 515Bs on the floor for several months, with NO enclosures.

(1) Stock 515B and 825, nothing to write home about !!!

(2) added a large 5 inch high, 3/4 inch thick, 18 inch long oak board into the port area, to reduce open port size. Hey, NOW we are getting some wheres.

(3) added a second 5 inch wide oak board, to block more open port area. HEY, its getting better to my ear. It SEEMS to me, that the ideal open port area, for my 515B and my room, in a dead stock 825 box, will be in the 90 to 100 square inch range.

(4) SURPRISINGLY, I could easily / consistently differentiate the difference of less than one square inch of open port volume, on the music's playback. To do so, I move the second board 1/8th of an inch ( times 5 inches is 5/8th square inches ) . As of "the first night" I am SURE I want to tune port size by ear in the future, to less than one inch. I feel that it has to be within "about" 1/2 inch to get the optimum from my 515B !!


(5) After "locking in " on the difference a small increment made regarding port size, I decided to try out GMs " mass loading" idea to the stock 825 box. I had no tweeter on top of the 825 enclosure, so, I took a cardboard box of my stored LPs, 12 by 12 by 16 inches long, and placed them on top of the 825, over the woofer's baffle board mounting area. Guessing 40 -42 pounds of weight added to 825 . HOLEY SMOKES, LOVELY !!! Lower distortion, better color, better dynamic resolution.

(6) I added a second record collection box to the first one, another maybe 40-42 pounds, so I has 80 pounds of mass loading. THAT was audible in the same direction, but it was INCREMENTAL .

FIRST LISTENING night's conclusions :

(a) Tune port size by ear, each time you mess with box internally . It is audible to 1/2 of a square inch.

(b) It is HIGHLY BENEFICIAL to mass load ALTEC 825 enclosures. I would ESTIMATE adding 50 to 120 pounds of mass, to each enclosure.

HOW TO EXECUTE (b) ABOVE :

I plan to do a combination of one inch thick DOW-brand Styrofoam, " Residential Sheathing Insulation" to fill up about 1/2 the space, beside the 825's side walls ( behind the curved flair ), and then, put multiple packets of cloth ( canvas, cloth or hemp - will outlast any plastic, is safer also ) bagged kitty litter ( thanks GM !! ) between the resonating curved flairs, and the added Styrofoam, maybe 50 pounds of Kiddie Litter, behind each flair. Seal off the entire volume, with a removable cover that extends the woofer baffle board to the side walls, as did ALTEC in the later 828 enclosure. My local grocery store sells Kiddie Litter for $2.99 a 25 Pound Bag. Wal Mart, in their automotive department, sells " oil spill pick up " for $3.22 a 25 pound bag.

This provides mass loading to the entire enclosure, ( hidden inside !! ) AND infinite bracing to the 825 flaired bass horns, and could benefit all A-7 boxes IMHO.

I was up till 2:20 AM this morning, listening to all of this. FUN and encouraging to me.

Jeff Medwin



(6)

[GM]

FWIW, a number of folks debated/experimented with different tunings ages ago and the consensus was 75"^2 [~42 Hz IIRC] for all but SE amps, which should ideally be tuned to the driver's actual Fs for best overall efficiency and what I tuned the 416A loaded A5-500 pair I had before converting them to a two way with a 411 'sub' in the bottom ~2/3rds.

Don't forget to brace/mass load the horn's bottom as you have found that short of massive concrete horns there's no such thing as too much mass/stiffness, just a point of diminishing returns.

Anyway, welcome to speaker design and particularly Altec 'our way' .

GM

[LowOhms]

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 !! "

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

When I was a little boy, my dad, a Post Office employee ( middle class ) secretly bought a ALTEC 604B and he sneaked it into our basement one midnight, while his wife / my Mom and I slept. Our basement consisted of two rooms, Mom's laundry room, and via an adjoining wall, the family's Rec Room on the other side. Dad cut a hole in the laundry room wall, and mounted the 604B while Mom and I were sleeping. It fired into the family Rec Room.

Of course, if Mom didn't like the ALTEC, she'd have a BIG circular hole in the Rec Room !!!

Dad demoed the speaker to the family the next day, and it paid off, no divorce ensued !! We all loved the sound. A second 604B followed, the next year. SO, I grew up since age 8 listening to good music ( Carousel, My Fair Lady, etc etc ) on ALTEC 604Bs !!

My first speaker purchase after college was a pair of 15 inch Tannoy s in GRF enclosures. Then, a life-long search for " state of the art ". Single and double KLH 9s, Infinity Servo Stats, Fulton FMI -80s, Fulton P-12 Premiers, etc etc etc. A multitude of amps, which is what "I" consider to be the WEAKEST link.

I was lucky to be mentored by Bob Fulton from 1978-1988 in Triode amp building, Robert was like a Dad to me !! In 2013-2015 WONDERFUL NEWS, two Kansas City audiophiles I had mentored in DHT amp building, have given me for free, the following : FREE FREE FREE , two nice 515Bs, two 802Ds, two 511B horns. FREE is hard to beat. In October of this year, one of the guys I amp-mentored 23 years ago gave me a FREE pair of ALTEC 825 enclosures, in near mint condition !!

I am out of pocket on ALTEC 800 HZ crossovers, and I traded -off the 511Bs for a pair of EMILAR EH-500 horns and 1 to 2 inch adaptors. I had GPA remagnetize the 802Ds, and put in new OEM diaphragms. Sometimes SOON this month, I am hoping to get the A7-800 system going in my modest living room ( 12.5 by 18 feet ) .

My GUESS is, after hearing Dennis Fraker's MLTLS and, from what I experienced with 604Bs as a child 63 years ago, I will REALLY ENJOY this new-to-me A7-800 system.

BTW, I will use a directly-coupled SET Type 45 DHT amp, I designed / built in mid 2015, on these A7-800s.

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

[bowtie427ss]

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 !! "

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

When I was a little boy, my dad, a Post Office employee ( middle class ) secretly bought a ALTEC 604B and he sneaked it into our basement one midnight, while his wife / my Mom and I slept. Our basement consisted of two rooms, Mom's laundry room, and via an adjoining wall, the family's Rec Room on the other side. Dad cut a hole in the laundry room wall, and mounted the 604B while Mom and I were sleeping. It fired into the family Rec Room.

Of course, if Mom didn't like the ALTEC, she'd have a BIG circular hole in the Rec Room !!!

Dad demoed the speaker to the family the next day, and it paid off, no divorce ensued !! We all loved the sound. A second 604B followed, the next year. SO, I grew up since age 8 listening to good music ( Carousel, My Fair Lady, etc etc ) on ALTEC 604Bs !!

My first speaker purchase after college was a pair of 15 inch Tannoy s in GRF enclosures. Then, a life-long search for " state of the art ". Single and double KLH 9s, Infinity Servo Stats, Fulton FMI -80s, Fulton P-12 Premiers, etc etc etc. A multitude of amps, which is what "I" consider to be the WEAKEST link.

I was lucky to be mentored by Bob Fulton from 1978-1988 in Triode amp building, Robert was like a Dad to me !! In 2013-2015 WONDERFUL NEWS, two Kansas City audiophiles I had mentored in DHT amp building, have given me for free, the following : FREE FREE FREE , two nice 515Bs, two 802Ds, two 511B horns. FREE is hard to beat. In October of this year, one of the guys I amp-mentored 23 years ago gave me a FREE pair of ALTEC 825 enclosures, in near mint condition !!

I am out of pocket on ALTEC 800 HZ crossovers, and I traded -off the 511Bs for a pair of EMILAR EH-500 horns and 1 to 2 inch adaptors. I had GPA remagnetize the 802Ds, and put in new OEM diaphragms. Sometimes SOON this month, I am hoping to get the A7-800 system going in my modest living room ( 12.5 by 18 feet ) .

My GUESS is, after hearing Dennis Fraker's MLTLS and, from what I experienced with 604Bs as a child 63 years ago, I will REALLY ENJOY this new-to-me A7-800 system.

BTW, I will use a directly-coupled SET Type 45 DHT amp, I designed / built in mid 2015, on these A7-800s.

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

That is a great post and story of the 604B's!

Sincere thanks for sharing.

[LowOhms]

That is a great post and story of the 604B's!

Sincere thanks for sharing.

Hi BowTie!!

I fired up the A-7s, with JUST the 515Bs in them, NO crossover, running full range, and three cartons of LPs on top of each enclosure, ( estimate 120 pounds, on each 825 ) to mass-load each STOCK 825 cabinet.

Wow, it is going to be a LOT of fun to own these. Started listening this past Sunday PM at 7 PM, and went to bed 4:15 Monday AM. I used a VERY good phono unit, as an analogue source, and it was wonderful. Piano blew my mind !! Listened to Artur Rubinstein play Bethoven's Appassionata ( early RCA Victor LP ) and I was stunned at the dynamics, clarity and realism. Thrilling. This system will be fun.

Jeff Medwin

[Old Guy]

I think the lack of replies was due to kitty litter specifically-very few used it. A number of things have been tried from bracing to foam to even concrete. Sand/epoxy mix I have heard personally. It helped smooth LF response substantially. A previous 250 hz peak was very reduced. This was back in less sophisticated days.

[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