Altec Custom VOTT Somethings

[Drugolf]

I found a nice set of custom built speakers loaded with Altec goodies and cabinets that were allegedly built to some Altec build plan about 30 years ago. The cabinets are relatively well built with an internal 1" thick wall surrounded by 3/4" oak ply.
The driver contingent is as follows:
Altec 802D HF Drivers
Altec H-811-B Horns (Gold in color)
Altec 414A woofers - 2 in each
Altec N-500-E Network.

All 16ohm

External cabinet size is 39" high, 26.5" wide, 21" deep.
Internal size is 8.4 CF

Port is 4" x 11.5" deep.

Rotary switch on back for network adjustment.
No insulation.
NO internal bracing.
Back panel is removable and needs more screws.
Cheap Screw terminals.

The Oak is not my cup of tea, but once buffed out again should look fine.
Came with fairly primitive grilles that need new material if I keep them in the same configuration.

Sound quality is impressive. Big and lively being run with my Dynaco St70.
Two of the woofers have cracks in the seem of their accordion surrounds that will need to be addressed unfortunately.

So what do I have the makings of here? I really am digging the sound so far and gotta think with some other refinements these could be really good. I am not sure what if anything has been done with the HF drivers over time.

[Earl K]

Nice setup!
http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=82822&stc=1&d=1542639890

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=82823&stc=1&d=1542639903

I would add some 2" fiberglass insulation/batting ( or the UltraTouch stuff maybe ) on 3 of the 6 inner surfaces ( to begin with ) > since that's how Altec did it.

Re; your splitting of the 414's surrounds.

Personally I'd keep it ( at least the cones & coils ) all original and simply fix the splitting from the backside with applied plasters ( WWI-style wound dressing ) made up of cigarette papers ( which is very thin ) and lightly applied rubber cement ( to glue the paper into the existing surround goop ). Consider that many surrounds are made from linen cloth and you get another type of backing material ( if paper seems too marginal ).

That would be my first course of a DIY type of fix .

:)

[speakerdave]

The 811 horn and 500E crossover are a mismatch, based on Altec and general recommendations to crossover at least an octave above physical cut off. Not sure exactly where that horn unloads, but it us called an 811 for a reason.

The fact that the woofer surrounds are damaged suggests that the speakers have been cranked all the way to eleven and the bass tone control twisted up by a wannabe DJ. That could also mean that your CD diaphragms have been stressed as well.

What you have there are some really nice speakers that would reward a little careful tweaking with hours and hours of very acceptable sound reproduction.

I think the cabinet may be wide enough to retrofit the 511 horns.

[Drugolf]

Thanks Speakerdave for identifying the conflict between horn model and network model. I will check measurements etc and see if I can find enough room to expand the opening in the baffle for the larger 511. Looks like it will be close, but then again the horns on my Santiagos go near side to side. The height might be the bigger challenge. As far as positioning it forward or back, should it be mounted back in the cabinet more than it is now where the horn is mounted on the baffle and then extends out from there. Again, most others I have seen are set back so the point of the horn is about the same as the baffle face.

I am uncertain how these were run prior to my purchase, but based on what I saw at the sellers house, yes, they could have been pushed and by not so great power. The splits in the surround are at the bottom of the woofers so it could also just be aging as they seem a bit dry and were pretty dusty etc. I need to check and make sure the diameter of the cut-outs for each woofer are actually large enough. It appears some of the surround is hidden behind the edge of the baffle there. Hmmm

Earl K, Interesting fix formula! I have emails out to GPA and Gordon W to see what they think about it as well. I would much prefer to keep as much original in-tact as possible of course.

Insulation for sure. Would like to here from folks what the best material is these days for these etc.

[gdmoore28]

Those are some nice-looking speakers.

And I would second Dave's suggestion about swapping out those 811B horns (rated for 800Hz crossover) for the 511B horns (rated for 500Hz crossover). These are the horns that should have been used with your crossover. This is the recommended configuration. But, if you are satisfied with the current rig, carry on. (The 511B horns measure 24" across the front if you want to measure for room.)

As for repairing the splits in the surrounds, there is a guy on ebay that sells the proper sticky mixture for repairing these. It never hardens, as opposed to any other commercially available mixture. Just use a small piece of linen and repair the cracks from the back, like Earl suggested. A repair using the proper sealer and a piece of linen will be a permanent repair. If the speakers and horn drivers sound OK, I wouldn't worry about them.

The biggest (and cheapest) modification that you can make to them is installing the Altec 30923 circuit to your horn leg. This circuit dramatically lowers the mid range "honk" and accentuates the hi frequencies. It's a change that moves the horn's sound more to a Hi Fi characteristic instead of a ProSound curve.

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=54336&d=1325785043
You need to build only the top portion of this circuit. (The bottom portion is a Zobel network not made for your system.) If your 802D driver is still 16ohm, you will need to use the following values:

C1 3mF
R1 7.8 ohms
R2 13 ohms

GeeDeeEmm

[Drugolf]

Excellent! Thanks GeeDeeEmm.

I have the 30904 in my Santiagos that I recapped recently so I am familiar enough with it to be comfortable to make the change. Makes sense.

I will switch out the horns, as long as the larger 511's will fit. It's gonna be close. Will head over to the marketplace section to see if anyone here has any before hitting up EPay where there seems to be a plenty.

Cool fix on the surrounds. Sounds simple enough as long as I can find that ebay seller with the goop.

David



Those are some nice-looking speakers.

And I would second Dave's suggestion about swapping out those 811B horns (rated for 800Hz crossover) for the 511B horns (rated for 500Hz crossover). These are the horns that should have been used with your crossover. This is the recommended configuration. But, if you are satisfied with the current rig, carry on. (The 511B horns measure 24" across the front if you want to measure for room.)

As for repairing the splits in the surrounds, there is a guy on ebay that sells the proper sticky mixture for repairing these. It never hardens, as opposed to any other commercially available mixture. Just use a small piece of linen and repair the cracks from the back, like Earl suggested. A repair using the proper sealer and a piece of linen will be a permanent repair. If the speakers and horn drivers sound OK, I wouldn't worry about them.

The biggest (and cheapest) modification that you can make to them is installing the Altec 30923 circuit to your horn leg. This circuit dramatically lowers the mid range "honk" and accentuates the hi frequencies. It's a change that moves the horn's sound more to a Hi Fi characteristic instead of a ProSound curve.

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=54336&d=1325785043
You need to build only the top portion of this circuit. (The bottom portion is a Zobel network not made for your system.) If your 802D driver is still 16ohm, you will need to use the following values:

C1 3mF
R1 7.8 ohms
R2 13 ohms

GeeDeeEmm

[Drugolf]

So I know my options, is there a network I can use instead of the N-500-E that will work with the 811 horn and 414A's? 16ohm.
I am not sure I will be able to modify the baffle within this cabinet to fit the 511 horn.

Also, is the surrounds goop mentioned below the same as the AR stuff?

[Earl K]

Here's the schematic for the N500-E.

I wouldn't be in any rush to swap it out ( see below for my reasons ).

http://www.audioheritage.org/photopost/data//500/N-500-E.jpg

Notice the 4uF (MFD ) cap used in the horn circuit.
- This starts a highish roll-off for a 10-12ohm driver ( such as this 802d > assuming it has the original 20275 diaphragm ).

This 4uF cap also somewhat negates the need for the 30923 circuit.

Here's a ( very rough ) XSim of this network ( using Zilch's .frd and .zma files for the 414Z woofers, along with some of my HF files > from a custom 802D combo ).
- One can see that when using this collection of drivers the actual crossover point is nicely above 1K.

- Drugolf, your crossover point ( with your speakers ) won't be that much different than what I'm showing here.


That's why I suggest that you shouldn't be in any rush to change it out.

http://www.audioheritage.org/photopost/data//500/Altec_N500-E_with_414s_.png

:)

[Earl K]

Drugolf,

Another thing, the current box tuning of that pair is way way too low ( dangerously low ).

A single 4" ( i.d. ) tube that is 11.5" long, gives a box tuning of @ 17hz. ( the light blue line seen in the picture below )

Tuning a box below the woofers Fs is a great way to destroy the woofers compliance ( and this helps explain your cracked surrounds ).

I'd suggest you take the tuning up to around 40hz ( you'll end up with a more usable bass response ).

2 x 4" ( internal diameter ) tubes that are @ 2-3/8" deep will offer an @ 40hz tuning .

http://www.audioheritage.org/photopost/data//500/Altec414z_x2_17hz_40hz_tuning_.png

I'd place the second port ( diagonally offset to the first ) below the upper woofer ( ie; for visual symmetry ) .

You have enough "extra" length of ducting to create these new ports.

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=82822&stc=1&d=1542639890

:)

[Drugolf]

Great stuff Earle, and thanks for taking the time to go through all that. Good to see Zilch's name come up too!.

This would be really good because while I may be able to widen the baffle opening for the larger 511, there isn't enough height and I run into the top of the higher woofer. Plus the work would not be all that simple to do correctly not knowing how this cabinet was pulled together beyond what I can see upon inspection. Cutting in a single new port hole shouldn't be all that difficult as it looks like there is enough surface area there to run the router on. ( I am working with a master wood craftsman on some KHorns right now and he will be a big help).

I opened up the Network last night and of course found all the tar coated contents. I hope I don't have to dig into that! I did deoxit the switch. Also quickly replacing the terminals to better 5-way posts for now. Of course the "in" screw terminals on the top of the network box do not have positive or com marked. Ugh. the old wire running from it to the old screw terminals also wasn't marked. Do I go with right is red?

Also, do you also concur on adding some insulation on a few of the internal walls? I still need to dig up info on that aspect.


Drugolf,

Another thing, the current box tuning of that pair is way way too low ( dangerously low ).

A single 4" ( i.d. ) tube that is 11.5" long, gives a box tuning of @ 17hz. ( the light blue line seen in the picture below )

Tuning a box below the woofers Fs is a great way to destroy the woofers compliance ( and this helps explain your cracked surrounds ).

I'd suggest you take the tuning up to around 40hz ( you'll end up with a more usable bass response ).

2 x 4" ( internal diameter ) tubes that are @ 2-3/8" deep will offer an @ 40hz tuning .



I'd place the second port ( diagonally offset to the first ) below the upper woofer ( ie; for visual symmetry ) .

You have enough "extra" length of ducting to create these new ports.


:)

[Earl K]

Great stuff Earle, and thanks for taking the time to go through all that. Good to see Zilch's name come up too!.

<<<SNIP>>> Of course the "in" screw terminals on the top of the network box do not have positive or com marked. Ugh. the old wire running from it to the old screw terminals also wasn't marked. Do I go with right is red?

Also, do you also concur on adding some insulation on a few of the internal walls? I still need to dig up info on that aspect.

Your welcome!

Yes, add some insulation.

Use a multimeter ( in continuity mode ) to determine the common input ( measure between either of the 2 black output wires and your choice of the 2 input tabs ).
- One of those 2 input tabs ( measured to the black output wire ) will give a very low Z reading of less than 1R ( ie; showing continuity ).


:)

[Drugolf]

Got it.

Add cross braces? Diagonal strip on back panel?



Your welcome!

Yes, add some insulation.

Use a multimeter ( in continuity mode ) to determine the common input ( measure between either of the 2 black output wires and your choice of the 2 input tabs ).
- One of those 2 input tabs ( measured to the black output wire ) will give a very low Z reading of less than 1R ( ie; showing continuity ).


:)

[Earl K]

Got it.

Add cross braces? Diagonal strip on back panel?

I would add ( full length ) diagonal strips ( 2x3's, glued + screwed with the 2" dimension contacting the plywood wall ) on the back panel and the two sides.

Top, bottom and baffle board I would leave alone for now.

This is definitely minimal bracing >> but I currently follow the creed that form needs to follow function ( + since these are very light-weight cones unlike JBL 12's > with limited XMax > they will pressurize the box a lot less than many other brands of woofers ).

- Less overall box pressure equates to less ultimate need to brace ( in my way of thinking > which of course can still be changed ).

:)

[Drugolf]

So the issue with the surrounds is worse than I thought. Removing all 4 woofers I can now see the full extent of how bad the surrounds are and for the most part the surrounds are pulling away from the the cone. I think the goop has mostly fallen to the bottom edge leaving the surrounds exposed and weak. plus, each woofer cut-out is slightly too small (about 10' instead of the specified 10.25) and the surround probabaly was hitting the edges at times or was at least being restricted. it's also where all the goop had settled and I had to heat it up with a hair dryer to get the drivers off.

I will probably talk to Bill at GPA tomorrow to see if they have the surrounds for these, but I do see some at Simply Speakers that are identified for 12" JBL, but they are the same dimensions as the 414 with the flat cone edge. Will these work?
https://www.simplyspeakers.com/jbl-speaker-cloth-edge-repair-kit-clsk-jbl2213.html

[Earl K]

Will these work?

Bummer, about the fully cracked surrounds.

FYI, I'm not aware of anyone in any of the forums ( that I frequent ) who's replaced an Altec or JBL linen or paper surround ( although maybe I'm just not paying close enough attention ).

Therefore I'd also say that you're in unchartered territory here.

The other surround source ( mentioned over at AudioKarma ) (https://www.ebay.ca/itm/12-ALTEC-LANSING-CLOTH-SURROUNDS-AMERICAN-010-THIN-JBL-W-ALTEC-SNOT-BOTTLE/183125185812?hash=item2aa31c9514:g:MpkAAOSwhHlaqAf o) looks to be the better choice for surrounds.

Some advice; keep all the hardened goop that you collect ( including the stuff still on the old surrounds ).
- You may need to reconstitute it ( if possible ) so that you have a backup supply of something original.

The stuff mentioned in this other link might turn out to be a formula that leaves the new surrounds too stiff ( with a higher than desired Fs > that would need to be measured by doing an impedance test ).

Also, it might be a lot more straightforward to simply make new baffle boards with the correct woofer cutouts ( than to shave back the existing holes > though I don't really know if there's a nifty router bit made for just that job > hopefully ).

:)

[Drugolf]

The trick with boring out the existing cut-outs will be if I can get the router and a template in there without the side panels preventing it. May not be enough room. I can CNC out a 10.15" template and use it once I am able to figure out the centering on the existing. The new port hole is easy.

But yes, a new baffle would also be the easiest if the existing would come out easy. The original builder used staples and a serious looking glue when attaching it unfortunately.


Bummer, about the fully cracked surrounds.

FYI, I'm not aware of anyone in any of the forums ( that I frequent ) who's replaced an Altec or JBL linen or paper surround ( although maybe I'm just not paying close enough attention ).

Therefore I'd also say that you're in unchartered territory here.

The other surround source ( mentioned over at AudioKarma ) (https://www.ebay.ca/itm/12-ALTEC-LANSING-CLOTH-SURROUNDS-AMERICAN-010-THIN-JBL-W-ALTEC-SNOT-BOTTLE/183125185812?hash=item2aa31c9514:g:MpkAAOSwhHlaqAf o) looks to be the better choice for surrounds.

Some advice; keep all the hardened goop that you collect ( including the stuff still on the old surrounds ).
- You may need to reconstitute it ( if possible ) so that you have a backup supply of something original.

The stuff mentioned in this other link might turn out to be a formula that leaves the new surrounds too stiff ( with a higher than desired Fs > that would need to be measured by doing an impedance test ).

Also, it might be a lot more straightforward to simply make new baffle boards with the correct woofer cutouts ( than to shave back the existing holes > though I don't really know if there's a nifty router bit made for just that job > hopefully ).

:)

[Earl K]

The trick with boring out the existing cut-outs will be if I can get the router and a template in there without the side panels preventing it. May not be enough room. I can CNC out a 10.15" template and use it once I am able to figure out the centering on the existing. The new port hole is easy.

But yes, a new baffle would also be the easiest if the existing would come out easy. The original builder used staples and a serious looking glue when attaching it unfortunately.

If they were mine I would simply cut-out the existing baffle boards ( leaving a 2" wide edge to fix a new one to ) and replace it with one made of Baltic Birch plywood ( either 3/4" or 1" thick ).

I see excessive over-hang past the existing baffle board ( from the side panels extending a couple ? inches ).

Significant ridges ( over-hang ) to the side of the baffle board triggers diffraction effects ( which are easily measured when compared to a flush baffle-board ).

So my approach is win-win ( IMNSHO ).

:)

[Drugolf]

Oooh, now you're thinking! Good thing someone around here is.

I will need to see how much overhand there is. I took the cabinets to my storage will I work on the woofers and wait to do the woodworking. Pictures barely show it.
I think it would be close to flush if a new baffle was installed. Might make grilles difficult, but then maybe do a good looking baffle so grilles would not be needed.
Why the Baltic birch?


If they were mine I would simply cut-out the existing baffle boards ( leaving a 2" wide edge to fix a new one to ) and replace it with one made of Baltic Birch plywood ( either 3/4" or 1" thick ).

I see excessive over-hang past the existing baffle board ( from the side panels extending a couple ? inches ).

Significant ridges ( over-hang ) to the side of the baffle board triggers diffraction effects ( which are easily measured when compared to a flush baffle-board ).

So my approach is win-win ( IMNSHO ).

:)

[Earl K]

I favor dense plywood baffles because plywood holds T-Nuts much much better than MDF or particle board.
- This is not an advantage if a person doesn't use T-Nuts ( which I happen to use in Pro-Audio applications > with SR speakers )

Mind you, if one is using wood screws to a-fix woofers( from the back-side to the baffle board ) my preference doesn't matter very much ( since any stripped out hole just means the user needs to find a virgin surface by slightly rotating the woofer ).

:)

[macaroonie]

The bits you need are as follows. A straight
cutter with a bottom guide bearing that is
undersized such that it will remove 1/8 the
You use that to remove most of the material
but you need to stop before the bearing has
nothing to run on. This will leave you with about 1/8 th of a lip
To remove this you need a top bearing flush trim bit. The bearing will run on the area you
previously cut resulting in a smooth cut edge.

Sorry about the giant letters. doing this from my phone.

[Earl K]

The bits you need are as follows. A straight
cutter with a bottom guide bearing that is
undersized such that it will remove 1/8 the
You use that to remove most of the material
but you need to stop before the bearing has
nothing to run on. This will leave you with about 1/8 th of a lip
To remove this you need a top bearing flush trim bit. The bearing will run on the area you
previously cut resulting in a smooth cut edge.

Sorry about the giant letters. doing this from my phone.

Good to know an actual technique is out there to fix this sort of problem ( no-doubt this seems rudimentary to you but,,, )!

Anyways, I'm glad that you popped in with your wood-working wisdom.

:)

[Drugolf]

Unfortunately, the existing cutout is not very good. Whatever the original builder used to cut, it didn't leave a consistent smooth rounded circle. I was hoping to do a better round cut.

[Tim Rinkerman]

For what it's worth, I'm quite sure those are built from the guts of 60's era Seeburg jukebox speakers. High quality for its day. The non adjustable crossover is a big clue. I worked in quite a few clubs, and fixed a few along the way...

[Drugolf]

May very well be. The guy I purchased them from said he only remembers them being low horizontal boxes. The gold horn sure is a give away.
There is a horn adjustment on the back though.
82850


For what it's worth, I'm quite sure those are built from the guts of 60's era Seeburg jukebox speakers. High quality for its day. The non adjustable crossover is a big clue. I worked in quite a few clubs, and fixed a few along the way...

[macaroonie]

Unfortunately, the existing cutout is not very good. Whatever the original builder used to cut, it didn't leave a consistent smooth rounded circle. I was hoping to do a better round cut.

Bummer. Template it is then. Do you have enough ground on the baffle to sit it on ?

[Drugolf]

That's what I am worried about and why we were discussing just cutting out the old somehow and building a new one. I can get the new one cut via CNC so it would be really good. The new added port hole will be easy enough as-is at least.


Bummer. Template it is then. Do you have enough ground on the baffle to sit it on ?

On another note I ordered replacement cloth accordion surrounds for the 4 woofers. GPA does not sell them so I went with that lighter weight option off ebay and got a little better price buying 2 sets. Bill did suggest re-purposing the original goop if needed onto the new surrounds.

[RMC]

Hi Drugolf and Earl,

RE: Bracing in posts # 12 and # 13

I certainly agree with bracing of such a large cabinet with the low frequencies involved.

My point here is simply that if you're going to brace you might as well do it the way that provides the most benefit, specially when the work involved is the same. Diagonal bracing isn't the most rewarding way among the simple methods.

In Ray Alden's "Advanced Speaker Systems" p. 5-6 (with well known Joseph D'Appolito being the Contributing Technical Editor of the book) they show diagonal bracing isn't as profitable within easy methods.

To demonstrate this they show five identical rectangular shaped pieces of wood (like your back and side panels):

1- No brace, panel resonance 60 hz

2- Widthwise brace in the middle, panel resonances of 100 hz on each side of the brace

3- Diagonal brace dividing the rectangle into two triangles, panel resonances of 115 hz on each side of the brace

4- Lengthwise brace in the middle, panel resonances of 160 hz on each side of the brace. As can be seen the gain here is more important than diagonal, and this is for the same work!

5- The fifth method shown is more complicated as it divides the panel in three unequal sections with two Lengthwise braces, panel resonances of 210 hz, 235 hz and 275 hz respectively are obtained.

Bracing's purpose is to minimize cabinet resonance effects, like enclosure coloration, by creating higher pitched resonances when panels are divided into smaller surfaces with brace(s).

Since the work and material costs involved are the same in this case, the issue being only the braces' orientation, it makes sense to go with the more desirable option among the easy stuff (i.e. # 4). Regards,

Richard

[Drugolf]

Thanks Richard! Good info.

To clarify I take this as braces that are strips of wood attached to the back and potentially side panels, about as long as the panels. ?

Would it still be best to have a board that extends across between the two side or also one front baffle to the rear panel?

The one weak point of the cabinet construction are the back panels oddly enough. They are 3/4" press board and there were only 45 screws holding it on. Time for something more substantial?



Hi Drugolf and Earl,

RE: Bracing in posts # 12 and # 13

I certainly agree with bracing of such a large cabinet with the low frequencies involved.

My point here is simply that if you're going to brace you might as well do it the way that provides the most benefit, specially when the work involved is the same. Diagonal bracing isn't the most rewarding way among the simple methods.

In Ray Alden's "Advanced Speaker Systems" p. 5-6 (with well known Joseph D'Appolito being the Contributing Technical Editor of the book) they show diagonal bracing isn't as profitable within easy methods.

To demonstrate this they show five identical rectangular shaped pieces of wood (like your back and side panels):

1- No brace, panel resonance 60 hz

2- Widthwise brace in the middle, panel resonances of 100 hz on each side of the brace

3- Diagonal brace dividing the rectangle into two triangles, panel resonances of 115 hz on each side of the brace

4- Lengthwise brace in the middle, panel resonances of 160 hz on each side of the brace. As can be seen the gain here is more important than diagonal, and this is for the same work!

5- The fifth method shown is more complicated as it divides the panel in three unequal sections with two Lengthwise braces, panel resonances of 210 hz, 235 hz and 275 hz respectively are obtained.

Bracing's purpose is to minimize cabinet resonance effects, like enclosure coloration, by creating higher pitched resonances when panels are divided into smaller surfaces with brace(s).

Since the work and material costs involved are the same in this case, the issue being only the braces' orientation, it makes sense to go with the more desirable option among the easy stuff (i.e. # 4). Regards,

Richard

[RMC]

Hi Drugolf,

RE: "To clarify I take this as braces that are strips of wood attached to the back and potentially side panels, about as long as the panels. ?" Exactly, these are your three largest panels, the front panel being the other. Do at least what Earl suggested, but placing those braces lengthwise in the middle of each panel.

RE: "Would it still be best to have a board that extends across between the two side or also one front baffle to the rear panel?" Subject to the fact I have not followed the thread consistently and in details, the bracing issue simply rang a bell with me:

Well you consider the cabinet's back panel as the weak point. Best? Probably yes, but again practicality also kicks in: access to drivers (yours are mounted from inside if I remember), placement of vents for unaffected air flow, added weight, etc. You'll need to assess that.

These front to back and side to side braces need not necessarily be 2X3" which is good news. Since your panels will be braced with 2X3" on edge (Earl) they gain rigidity and will "expand" less than before from in-box pressures. Weems has an interesting note regarding braces that tie opposite walls together:"Such a brace need not be thick because any tendency for the walls to move must stretch or compress the brace. That movement is in the direction of greatest stiffness."(Note 1). Makes a lot of sense to me.

For my larger boxes, typically I use older 2X2" for front to back and left to right bracing (the cross), in addition to bracing on each panel. The smaller top/bottom panels are braced too, but no top to bottom brace is used here, since smaller panels of same material and thickness are stiffer than larger ones.

I also use an horizontal brace placed on edge on the front panel of my larger cabs. That brace's size varies a little based on box size, space available and requirement to avoid any interference with vent air flow. That type of brace is something you may want to consider in view of your baffle panel's size. You'll need to assess space and brace size you can accept, if any.

RE: "The one weak point of the cabinet construction are the back panels oddly enough. They are 3/4" press board and there were only 45 screws holding it on. Time for something more substantial?" 3/4" press board isn't bad at all when properly braced lenghtwise and front to back, even if the panel is removable. It just needs to be done properly.

On this panel you will likely need to use weather stripping tape and/or removable sealant (silicone). I would use both! to prevent air leaks.

More bracing affects net box volume and cabinet weight. You should measure and keep count of the braces' volume, specially when going for more, to account for this, as well as drivers and vents, in the Vb calculation. If you plan to "rattle the silver" with the boxes you should go for a little more instead of less.

Other than bracing, another challenge you will have with such boxes is maintaining a good box seal (air tight) in order to achieve an acceptable box loss figure. In this context, its a tough job to get up to or better than QL 5 which would probably be the starting point of your modeling. If you use the free Win ISD Pro software remember the default box loss is an optimistic QL 10 wich can be changed to QL 5 in Box tab, then go to bottom of page, click on Advanced, then click on the first item (QL), enter 5 there instead of the 10, and exit. If you save the project QL 5 should stay with it. If you start another project QL 10 will be back so you need to change it again, this time to the standard QL 7?, it depends on circumstances. Regards,

Richard

Note 1: David B. Weems, Designing, Building, and Testing Your Own Speaker System, 4th Edition, P.35.

[Drugolf]

Great stuff Richard, thanks.

I received the new 414A surrounds. They look and fit great. Now the tough part - removing the old goop rings. Acetone + heat for the goop and MEK for the glue if needed. I am going to try and save as much of the goop as possible I guess by melting it off the old surrounds. Would like to have it on hand in the event I do not like the stuff that came with the surrounds. To me that stuff looks like a simple PVA glue product, but the seller says it isn't. I will try it first on one of the old surrounds to see what it does on drying.

[Earl K]

Great stuff Richard, thanks.

I received the new 414A surrounds. They look and fit great. Now the tough part - removing the old goop rings. Acetone + heat for the goop and MEK for the glue if needed. I am going to try and save as much of the goop as possible I guess by melting it off the old surrounds. Would like to have it on hand in the event I do not like the stuff that came with the surrounds. To me that stuff looks like a simple PVA glue product, but the seller says it isn't. I will try it first on one of the old surrounds to see what it does on drying.

Which surrounds did you end up buying?

:)

[Drugolf]

The ones on EBay. Seller stpsmf. Hempopotamus Speakers. Got a little break buying two sets.


Which surrounds did you end up buying?

:)

[Drugolf]

My woodworker partner and I were discussing these today at great length. His thought is to simply build new cabinets and quit messing with the previous build that while not bad, does have some issues that we are trying to work around. On top of all that, they are Oak. Thoughts on the benefits? I can fine tune things down to a size, volume and configuration that would maximize the potential of these components and have a much more beautiful cabinet. And frankly it won't cost a lot depending on the selection of hardwood.

I'm not sure if I would want to get into changing components unless there would be a significant advantage. I would guess the horn would be something to fully vet.

[Earl K]

My woodworker partner and I were discussing these today at great length. His thought is to simply build new cabinets and quit messing with the previous build that while not bad, does have some issues that we are trying to work around. On top of all that, they are Oak. Thoughts on the benefits? I can fine tune things down to a size, volume and configuration that would maximize the potential of these components and have a much more beautiful cabinet. And frankly it won't cost a lot depending on the selection of hardwood.

I'm not sure if I would want to get into changing components unless there would be a significant advantage. I would guess the horn would be something to fully vet.

I'll ponder all that and respond in the morrow.

:)

[Earl K]

So ( just my 2 cents ) my suggestion is to put off for a while the building of new cabinets.

In the meantime use what you have there to figure out the following ( before moving on + building your new ones ) ;

(i) Optimal size ( determine best size for your circumstances and the realities of working with Altec 414's )
- One can always reduce a boxes net volume by temporarily placing known fillers into said box and then adjust box tuning to experience the effect of the smaller box.


(ii) Optimal box tuning ( determine the best box tuning for your room and musical tastes )
- You'll need some box tuning software and the ability to actually measure the resultant box tuning via impedance curves > but this is well worth the effort to learn > since it'll result in a custom tuning for your room .


(iii) Optimal internal damping
- ( ie; determine whether Altec correct in it's minimalist approach of just lining 3 of 6 internal surfaces ? )

(iv) Optimal internal bracing
- ( ie; see if historically if Altec correct in its minimalist bracing approach > typically using diagonal bracing > according to their own enclosure building guides )

EDIT:(v) The best vertical arrangement ( for those twin 414's )
- Unfortunately, only making a test baffle board can accomplish this task / which means cutting out the older baffle board on at least one of the existing speakers > something that may be un-palatable.

:)

[Drugolf]

Makes sense to me. Let's do it! ;)

Item i is probably my biggest challenge. I am not sure I have a circumstance (room) where these will ever really be applicable in an ideal world so I don't think I wont to get too specific with matching my environment. But I say be practical. I need to think about it a bit. Putting off for a while is going to happen irregardless simply because it is winter and working on large cabinets etc is a little difficult at the moment. I am in the midst of my KHorn rebuild with my woodworker at his shop so maybe once those are wrapped up we can at least work on the existing baffle.

In addition, the first thing I need to do is do the repairs on the woofers with the new surrounds and make sure all goes well with that. Good cold of winter inside work.

ii - no problem. I have Woofer Tester 2. Have not used it for box tuning yet though and will need to learn that. Also have a UMIK mic and miniDSP

v- Twin 414's What other applications even use twin 414's? Does it make sense? I happen to have a couple 803B 15" woofer sitting here if for some reason that's a better combo. Maybe the 414's would be best used and re-purposed in a smaller single woofer driver enclosure meant for a smaller room? The thing is, I love large speakers and the big live sound they produce. The problem specific to me is a smaller 13 x 12 main listening lounge and for the most part they are all just too big.

Again, thanks Earl for taking the time with me here on this.


So ( just my 2 cents ) my suggestion is to put off for a while the building of new cabinets.

In the meantime use what you have there to figure out the following ( before moving on + building your new ones ) ;

(i) Optimal size ( determine best size for your circumstances and the realities of working with Altec 414's )
- One can always reduce a boxes net volume by temporarily placing known fillers into said box and then adjust box tuning to experience the effect of the smaller box.


(ii) Optimal box tuning ( determine the best box tuning for your room and musical tastes )
- You'll need some box tuning software and the ability to actually measure the resultant box tuning via impedance curves > but this is well worth the effort to learn > since it'll result in a custom tuning for your room .


(iii) Optimal internal damping
- ( ie; determine whether Altec correct in it's minimalist approach of just lining 3 of 6 internal surfaces ? )

(iv) Optimal internal bracing
- ( ie; see if historically if Altec correct in its minimalist bracing approach > typically using diagonal bracing > according to their own enclosure building guides )

EDIT:(v) The best vertical arrangement ( for those twin 414's )
- Unfortunately, only making a test baffle board can accomplish this task / which means cutting out the older baffle board on at least one of the existing speakers > something that may be un-palatable.

:)

[Earl K]

Twin 414's What other applications even use twin 414's? Does it make sense?

Altec made at least 3 variants of boxes that used twin 414's.

The industrial looking 9844 (http://[/COLOR)and the home models Malibu (http://[/COLOR) and Carmel (http://[/COLOR)

Personally, I like how twin vertically-oriented woofers load a room ( more so than horizontally twinned woofers ).

Even better ( IMHO ) is an MTM setup using twin woofers.

:)

[Drugolf]

I went ahead and busted out the existing baffle board. This now will allow me to fabricate something entirely new and as wanted. I may still build new enclosures, but for now the existing ones will allow some experimentation.

One of the things I did not like from an aesthetics standpoint was how the nose of the horn stuck out from the rest of the baffle and required an odd opening in the grille. I can now inset the horn a little to get it back and behind a full grille. Will this cause any issues? My Santiagos and Valencias had the horn set-back a little.

Also, should I consider any sort of integrated super tweeter?

[Earl K]

I went ahead and busted out the existing baffle board. This now will allow me to fabricate something entirely new and as wanted. I may still build new enclosures, but for now the existing ones will allow some experimentation.

One of the things I did not like from an aesthetics standpoint was how the nose of the horn stuck out from the rest of the baffle and required an odd opening in the grille. I can now inset the horn a little to get it back and behind a full grille. Will this cause any issues? My Santiagos and Valencias had the horn set-back a little.

Also, should I consider any sort of integrated super tweeter?

Hi Drugolf,

Altec themselves set the 811b back almost an inch ( in comparison to the 414's ) in some of the older versions of the 9844 system ( & the Malibu seen below ).
- In case the pic doesn't make it clear, Altec added a 3/4" strip of wood to the back of the baffle board and then rear mounted the 811b to it ( effectively moving the horn close to 1" rear-wards when the thickness of the horms metal flange gets added in ).
See;

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=28915&stc=1&d=1191900237



Doing so will also mean adopting whatever model crossover ( & speaker polarities ) Altec used with that offset.

Later on with the 9844A Altec "flipped" the relation-ship between the woofers & the horn mounting ( moving the woofers backwards in comparison to the previous variants ) .
- That flip-flop amounts to almost 2" of offset manipulation ( fwiw ) that would again need to be accounted for in the crossover ( which I haven't studied to see if Altec actually responded to ).

See;

https://www.picclickimg.com/00/s/MTMzNlgxNjAw/z/Eo4AAOSw3v5Yo1Lr/$/Altec-Lansing-9844A-2-Way-3-Driver-Speaker-Cabinets-Empty-_57.jpg

Your N500E works best ( according to my XSims ) with about an 8" offset between the drivers AC ( acoustic centers > which are typically somewhere around the voice-coil areas )

I'm using Fostex tweeters these days with my 288's ( added in at around 10K ), so that would be a natural recommend from me .

:)

[Chas]

My Carmel’s 811B’s were offset much the same as the Malibu’s as well, only the system was horizontally oriented. I really liked the double 414’s, I later put mine in vertical, ported woofer only boxes and really enjoyed them.

On the subject of improved HF performance, personally I would steer away from adding a tweeter, since this year I experimented and replaced my Valencia’s old 806 drivers with GPA 902’s - they are simply stunning with the 811’s and I no longer feel any need for more HF extension.

Just my 2 cents...

[Drugolf]

8" offset - please explain?

You have the outboard fostex" I use T90A's with my Bozak Concert Grands and recently tried with my AR3's with good results. Or should these be an integrated solution on the baffle and mods to the crossover?



Your N500E works best ( according to my XSims ) with about an 8" offset between the drivers AC ( acoustic centers > which are typically somewhere around the voice-coil areas )

I'm using Fostex tweeters these days with my 288's ( added in at around 10K ), so that would be a natural recommend from me .

:)

[Earl K]

8" offset - please explain?

You have the outboard fostex" I use T90A's with my Bozak Concert Grands and recently tried with my AR3's with good results. Or should these be an integrated solution on the baffle and mods to the crossover?

See what you can get from these links ( click the pics for more detail );

https://upload.wikimedia.org/wikipedia/en/f/f5/TM_lobe_time_aligned.gif (https://en.wikipedia.org/wiki/Loudspeaker_time_alignment)

https://www.daytonaudio.com/OmniMicV4/Zaxis.png (https://www.daytonaudio.com/OmniMicV4/hs110.htm)

:)

[Drugolf]

Good to know about GPA's 902's. I typically like to maintain the original intent or form factor of the original designs with my restorations so an up grade to the 902 would be that. Had considered keeping the horn out of the box. It would also allow me to play with different horn option easier.

QUOTE=Chas;419429]My Carmel’s 811B’s were offset much the same as the Malibu’s as well, only the system was horizontally oriented. I really liked the double 414’s, I later put mine in vertical, ported woofer only boxes and really enjoyed them.

On the subject of improved HF performance, personally I would steer away from adding a tweeter, since this year I experimented and replaced my Valencia’s old 806 drivers with GPA 902’s - they are simply stunning with the 811’s and I no longer feel any need for more HF extension.

Just my 2 cents...[/QUOTE]

[Drugolf]

Thanks


See what you can get from these links ( click the pics for more detail );

https://upload.wikimedia.org/wikipedia/en/f/f5/TM_lobe_time_aligned.gif (https://en.wikipedia.org/wiki/Loudspeaker_time_alignment)

https://www.daytonaudio.com/OmniMicV4/Zaxis.png (https://www.daytonaudio.com/OmniMicV4/hs110.htm)

:)

[Drugolf]

So I am strongly considering building the new baffle to house only the 414's and associated ports within the cabinet. Then coming up with an attractive solution on top for the horn. Thouhgts?

Also, the 414's were rear mounted. Do I want to do the same?

[Earl K]

So I am strongly considering building the new baffle to house only the 414's and associated ports within the cabinet. Then coming up with an attractive solution on top for the horn. Thouhgts?

Also, the 414's were rear mounted. Do I want to do the same?

I too would keep the horn separate & up on top.

Doing so allows adjustment of the "Z" axis ensuring proper summation in the crossover region ( so says the theory > in practice one needs measurement equipment of some type to check the FR ) .

Personally I prefer the look of woofers that are counter-sunk and mounted to the front of the baffle ( that's just my own bias mind-you ).

OTOH, you might not have any choice in how you a-fix those older 414's ( I don't know if they can be mounted any other way but to the back of the baffle board ).


:)

[Drugolf]

Yeah, being able to play with that axis seemed like the smart move. plus the versatility of changing horns etc over time. Will likely keep the crossover out as well of course.

Wit the new additional available surface area on the baffle, any thoughts on re-orientation of the 414's and ports within the now available larger baffle area? Keep the same design and just slide them up a bit to center them?

[Earl K]

Yeah, being able to play with that axis seemed like the smart move. plus the versatility of changing horns etc over time. Will likely keep the crossover out as well of course.

Wit the new additional available surface area on the baffle, any thoughts on re-orientation of the 414's and ports within the now available larger baffle area? Keep the same design and just slide them up a bit to center them?

I'll ponder all that & offer an opinion later ( before the 24hr editing limit is reached ).

:)

[Earl K]

I'll ponder all that & offer an opinion later ( before the 24hr editing limit is reached ).

:)

Well that didn't work as planned .

I happen to like the existing look ( FWIW ).

Anyways, the challenge as I see it is making twin twelves look good & balanced (fengshui (https://en.wikipedia.org/wiki/Feng_shui) ) within such a large baffle face.

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=82822&stc=1&d=1542639890

You'll get better response transitioning ( in the crossover region ) with the top twelve closer ( within 6" ) of the bottom of the horn.

Moving the bottom woofer in lock step then creates a huge area underneath ( where the ports can exist, of course ) that needs to be filled with something.

FWIW, I like the look of the diagonally staggered twelves > so I would keep that look personally.

One can argue ( endlessly it seems ) about the impact on "imaging" from this staggered type arrangement ( but unless one is willing include & maybe go to an MTM arrangement then I feel the debate is wasted breath ).

:)

[Drugolf]

I will whip up a few versions in AutoCAD and see what they would look like.

[Drugolf]

Still working on the new surrounds. Been too cold to go out in the garage to use the MEK. I just picked up a new heater for out there so maybe I will now be able to make some progress on them. So far they are tough buggers. Getting the old gasket off has been the most difficult one I have ever had the displeasure doing.

Meanwhile I messed around a bit on AutoCAD with layouts and all for these which in the end will be easy to do in whatever fashion makes the most sense. But upon further study of the Malibu and Carmels that Earl hinted the 414's were used in pairs in originally my guess is that these were used in Carmels except for teh fact that thes are 802D and not the 806. I like the low boy look of the Carmels, but man they take up a lot of space and don't get the horn up into the desired plane. The Malibus make sense and could be dressed up a bit more from a cabinet design standpoint if so desired.

Will need to study a bit more the design and whatever pros and cons that have been determined about them over time. Like is that cabinet got enough volume? In the end, maybe the Malibu makes sense as a template for a rebuild. (oddly it isn't ported)

[Chas]

Yes, ultimately my Carmel’s dimensions were a PITA, which was the driving factor in stripping out the components for re-use.

I’ve always thought the Malibu was far more elegant and very attractive. If I was any good at woodworking that’s what I would build, only make the cabinet a proper T/S vented box and include some offset for the 811 along the lines of the 846B Valencia.

[Drugolf]

I just purchased a set of Emilar EH-800A horns. What do you think about swapping in these for the 811's? As far as current driver options I have the 802D's (16ohm).

[Drugolf]

83311

[Chas]

I just purchased a set of Emilar EH-800A horns. What do you think about swapping in these for the 811's? As far as current driver options I have the 802D's (16ohm).

1. I’m not familiar with them.
2. With the latest GPA driver, I have no problem using the 811.

[Earl K]

83311
Oops, I posted this in another thread too but probably should go here as a follow-up.

SO here is my initial Winisd graph for a Malibu configuration box. There are two of the 411A woofers and using the plans it appears that the cabinet volume is 7.5 Cf. I took that down to 6.8 for loss for bracing drivers etc.

Sealed box. .707 Max Flat amplitude response alignment.

Does this appear as it should? What is it telling me?



Truthfully, I can not make either model of woofer ( 411 or 414 ) produce such a shallow curve like you're showing here ( in a 6.8cu' closed box ).

How about posting the ( .wpr ) file so that others can see what you are up to?

- Zip it first .

:)

[Drugolf]

not sure what .wpr is, but if you are wanting to see what I ended up with in terms of parameters entered, here is this:
83314
83315

[Earl K]

Vas ( for the 411-8a ) is 31.76 cu' ( not litres, like you have entered ).

[TW14MB]

Drugolf,

As a Malibu owner I read this thread: http://www.audioheritage.org/vbulletin/showthread.php?18913-Altec-9844-8B

I was under the impression that the 802 was closer to the 902, or at least is "better" than the 806a.

Testing the 902/info is detailed in that thread.

[Drugolf]

Ah yes, good catch. Thought I got all those.

Adjusted accordingly and here is the new graph. Blue is sealed at 6.5 Cf volume. Green is one 4" port .33 long. also adjusted QL to 7.00 from 10.00 Tuning Freq on the green vented line I adjusted to 40 (see I remember Earl).

Something I need to look into as a side note here pertaining to the Malibu box, it appears the cut-out for the horn is wider than the horn thus leaving a couple narrow openings each side of the horn. Is this then considered the way they vented the speaker within the design?

83316

[Earl K]

it appears the cut-out for the horn is wider than the horn thus leaving a couple narrow openings each side of the horn. Is this then considered the way they vented the speaker within the design?

All of Altecs enclosures that followed this muddled model are really from the time when pre-TS parameters were codified ( early-mid 1970s ).

The "large horn cut-out approach is not the way to deal with the realities of tuning a Bass Reflex enclosure.

Again, it's an obsolete approach.

:)

[Drugolf]

All of Altecs enclosures that followed this muddled model are really from the time when pre-TS parameters were codified ( early-mid 1970s ).

The "large horn cut-out approach is not the way to deal with the realities of tuning a Bass Reflex enclosure.

Again, it's an obsolete approach.

:)

So seal that off in favor of adding a actual port/vent?

[TW14MB]

So seal that off in favor of adding a actual port/vent?

I am watching for Earl's reply with much anticipation. I have wondered about this. I would like to seal those gaps and add a back or bottom facing port. I am not sure how much collector value I would be ruining by cutting a hole in the back, so I could make a new back piece entirely. For a bottom port option, my Malibu cabinets have a trim piece on the front and sides that elevate the actual cabinet bottom off of the ground. It would have to be calculated to see if that's enough air volume to do the job. That would be a permanent change though!

[Earl K]

So seal that off in favor of adding a actual port/vent?

Yes, seal it off and add a calculated ( & verified by an impedance sweep ) port .

Any other ( unexpected or un-accounted ) holes in the enclosure raises the box tuning ( Fb ) .

:)

[Drugolf]

Yes, seal it off and add a calculated ( & verified by an impedance sweep ) port .

Any other ( unexpected or un-accounted ) holes in the enclosure raises the box tuning ( Fb ) .

:)

Okay what I think I am going to do is do some testing using the original box, but with a baffle I will build that is more in keeping with the Malibu design. I will zero in on ports for it now that I am starting to understand how to determine all of that, at least on paper. The cabinet is a little larger than the original Malibu so I will have to play around with that too, which may be a good way to determine if more internal volume is a good thing.

Richard in my parameters WINISD thread suggested I could drop the tuning down since the 411A FS is pretty low at 18.31. I will poost a drawing of the baffle once I get it drawn up. One with the 811 horn, the other with my new Emilar horn.

[Drugolf]

Okay, here are some baffle configuration options for using the existing cabinet for now. Baffle is 34.5H x 23.75" W. The first two identify the cutout for the 811 horn within the baffle. I would probably set that back so the front of the horn is at the front of the baffle. the 3rd option shows a Emilar bowtie horn mounting on top and using the entire cabinet for just the 414A's. 8.0 CF of volume.

83388

[Earl K]

Okay, here are some baffle configuration options for using the existing cabinet for now. Baffle is 34.5H x 23.75" W. The first two identify the cutout for teh 811 horn within teh baffle. I would probably set that back so the front of the horn as at the front of the baffle. the 3rd option shows a Emilar bowtie horn mounting on top and using the entire cabinet for just the 414A's. 8.0 CF of volume.

83388


I'd go with the third pic ( horn on top ).

:)

[speakerdave]

I'd go with the third pic ( horn on top ).

:)

Agree on that. The look goes back to the original LMCo. Iconic 2-way 800 cycle woofer to a horn monitor, and hasn't been improved on since. Some performance gain, though, may be obtained by baffling the horn.

[Drugolf]

Agree on that. The look goes back to the original LMCo. Iconic 2-way 800 cycle woofer to a horn monitor, and hasn't been improved on since. Some performance gain, though, may be obtained by baffling the horn.

When you say baffle the horns, are you thinking a front only open baffle type structure? Does that add additional stability for resonance purposes, or just a little more wingspan?
I've worked on it already a little. A bit more challenging cut-out of course and for it to look good I think it would be best as a front mount so the cut doesn't have to be perfect and is hidden behind the lip. I could dial in the cut-out and do it with a CNC to get a great cut if that makes a big difference.

[speakerdave]

When you say baffle the horns, are you thinking a front only open baffle type structure? Does that add additional stability for resonance purposes, or just a little more wingspan?
I've worked on it already a little. A bit more challenging cut-out of course and for it to look good I think it would be best as a front mount so the cut doesn't have to be perfect and is hidden behind the lip. I could dial in the cut-out and do it with a CNC to get a great cut if that makes a big difference.

Not a horn expert, but, yes, I think the way the horn is terminated can affect the presence or not of resonances. Also loading and pattern control in the cutoff region. And being bolted to a wood baffle will help damp vibrations in the horn body. The LMCo. horn was tar-filled I believe.

A flat "false front" baffle would do almost as much as having the horn in the box.

I like the horn on top for a couple of reasons. One, I guess is the industrial chic aspect of it-- having the works showing. Mounting the horn to the baffle and securing a heavy CD (more of a problem with large format) inside the cabinet is a lot more work. Also, I don't think having the horn projecting through the baffle/grille plane looks that great, except when done as well as the Eames's did it. I also like smooth looking fully enclosed speaker systems, and so do spouses. With the Emilar EH800 that is easily achieved, except of course, for the tricky cut for the horn. Putting it in the cabinet would give you the advantages mentioned above with regard to baffling.

[Drugolf]

Got some things done here. Fabricated a new baffle to use with the original cabinets from old Khorn front panels that I recently removed to build new ones for. 3/4" plywood. Went with the straight evenly spaced vertical alignment for the 414A cut-outs with the 2 ports flanking in the middle. Rear mount and using inset nuts so I can remove the woofers easily enough later as needed.

The horns will be mounted on top so in the end the cabinet volume is 9.1 cf before subtracting anything for the drivers etc, so I am using a little less for my modeling in WinISD. I am ready to put this all together so here are some graphs for 35hz tuning and 40hz tuning with the 4" round ports. What looks better? Any thoughts on what I might want to adjust? The port length on the 35Hz is 3.6". On the 40hz it is 2".

83638

83639

83640

Also, here are two of the 414A woofers with the new surrounds and gaskets. The goop is white before application but becomes clear in a few hours.
83641

[Earl K]

Ultimately the tuning you go with has to interact nicely with your room acoustics & ever-present room modes > therefore its impossible to predict which of those 2 curves will be best for your particular circumstances.

That said, I like flexibility with box tunings > therefore I would want to know what happens ( or what the predictions say ) if I were to block one of two ports ( stuffing the ducting with foam for instance ).

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=83641&d=1553532149

BTW, you're the first poster that I'm aware of ( almost anywhere ) that has replaced his own linen-based surrounds on a woofer ( so I'm really impressed :applaud: ).

Nicely done!

:)

[Drugolf]

Yeah, I am thinking I start wit the longer ports and go from there. Can try stuffing one, then making them shorter and so on. The 4" ABS is the least of my worries. Got a lot of variables to play with including bracing and insulation yet too. The cabinets are basically 1.5" thick with a 3/4" pressboard box inside a 3/4" ply box. Front to back bracing I think is the best addition at this point for sure.

I was surprised not to find anything out there on installing new surrounds on these so I am gad I found what appears to be a good product to give it a go with. Otherwise the option to do a complete re-cone has is negatives including cost so I am hoping for good results doing this. Won't know until I run them through the paces and maybe do some measurements. They look fine though. If they fly off after the first few big bass notes, I guess we'll know. :blink:

I am heading out of town on Spring Break for the rest of the week so it may be a couple before I get back on this. Meanwhile i picked up a pair of 416-8A woofers to put into the mix somewhere with a build.

[Drugolf]

EDIT: Finding it very difficult to source this material. See new thread.

Zeroing in on my insulation choice. Looks like the Owens Corning unfaced 703 product is ideal. It has a PCF of 3.0
Here is a graph showing the sound insulation results at various thicknesses. Should I stick with the 1"?

83780

[speakerdave]

The 1" non-shedding unbacked fiberglass I've used is sold under the Wrap-on label. They used to deal direct, but I believe now they prefer to go through B.E. Atlas, a jobber in Chicago. Atlas will take a credit card order over the phone. 800 305-4393 (tel:800 305-4393).

[Drugolf]

Not any more. product no longer available.


The 1" non-shedding unbacked fiberglass I've used is sold under the Wrap-on label. They used to deal direct, but I believe now they prefer to go through B.E. Atlas, a jobber in Chicago. Atlas will take a credit card order over the phone. 800 305-4393 (tel:800 305-4393).

[Drugolf]

Well, got something put together. Using the original crossover for now and some Emilar bowtie horns with the 802D drivers.
The new baffles are front panels from a set of Khorns that I removed to install new ones. I added bracing within and used the 2" JM fiberglass on bottom, back and 1 side. I initially hooked these up with some 811's.
I put together a little sled and baffle for the bowties for the heck of it to see how well that helped stabilize things. It of course just adds a lot of mass to the presentation.
Overall I feel these position the horns up to high, but of course that is working with the existing cabinets for now. They are little more than 9 Cf internal area.
I moved them into our family room to the chagrin of the wife for a test in a suitable size room. The garage is just to echoey.

83977