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Portaflex dimensions / construction

marsbel

marsbel

Jun 21, 2006
78
54
Belgium
#1
Hello,
I'm a member for some time, but did't get around posting until now.
I have in my posession 2 '72 square magnet CTS speakers which I salvaged from a wornout Fender cabinet in the early '90's. They’ve sat on a shelf with no real pupose since then.
Some time ago I bumped into the official Portaflex thread here on TB and discovered that the B-15’s also used CTS speakers.
So here’s my plan: build a ‘60’s double baffle cab and a ‘70’s Thiele cab in which to use these speakers.
I did some searching on construction and dimensions and so far I’ve come up with these (Please correct me if you find any errors!):

‘70’s Thiele Cab:
- H: 24”
- W: 21”
- D: 14”
Amp Gap:
- W: 21”
- D: 11 ½”
- From front: 1 ¾”
- From back: ¾”
- Inner lip: ¾”
Distance from front to grill: 3/8”

‘60’s Double baffle Cab:
- H: 21”
- W: 21”
- D: 14”
Amp gap:
- from front: 3 ½”
Strip across speaker: 1”
Grill baffle thickness: ½”
Gap between baffles: 3/8” (1/4” spacer + nut thickness)
Face frame width: 1 ¾”

I would measure everything myself, but old Ampeg’s aren’t really common here in Belgium so I want to ask you guys to double check these measurements.
Also, in the event that I ever come across a B-15N head, I’d want to be able to use it with one of the cabs, so the dimensions of the amp gaps are very critical.

I’ still need some other measurements though:
- corner radius
- port size and position on thiele cab
- port dimensions (LxW) on double baffle
- face frame thickness (DB)
- latch positions
- Lid dimensions
- Position of amp feet, cups, etc…

Detail pics would be nice too.
Any help would be very much appreciated!

Oh, and I do know that readymade cabs can be bought from Fliptops and Vintage-Blue amongst others, but I just like to build things myself… I will be buying specific from them though.

Thanks and best regards,

Mark
 
#2
First off, you need to determine that these CTS's are the actual speakers Ampeg used in the 70's. A pic would help. Second, if they are the ones used in the B-15's of the 70's, then you should only build a Thiele cab for them, as they don't work well in double baffle cabs. They're a pretty dark speaker without a lot of high end, and they sound kind of muffled in a double baffle cab. But they sound absolutely gigantic in a Thiele cab.
 
#4
Probably they're not exactly the same ones as used in Ampegs; I understand that these were specifically built for each manufacturer, but I don't think the difference would be very big. Constructionwise, except for the label, these speakers look exactly the same as the ones used in portaflexes. I don't have pics right now, there in storage, but I've dated them to '72, manufacturer code was 137.
I did hear the recordings of your cabs in another thread, and I liked the thiele cab the most, but I'd still like to try a double baffle cab to have some diversity. If it doesn't work out, I can always get a Delta 15.
Mark
 
#5
Now I've received some great info from Mark (Vintage-Blue) for the double baffle cabinet, could anyone inform me on the thiele cab?
I've listed the basic dimensions in the first thread. Are they correct?
Also can anyone shed some light on the baffle? I thought I've read it was a ported design, but the pics I've seen don't reveal the porting.
Regards,
Mark
 
#6
Hey guys,

I'm bumping this because it seemed like the most relevant thread.

I work part-time at a recording studio in Brooklyn and our number-one recording bass amp is a B-15n head with a bogus "home-made" cabinet. It's got some issues like rattles and buzzes and is hardly a "copy" of the real thing but it gets the job done... sorta. I made a new baffle for it and chased some of the noises so it's usable now... however I can only imagine what this thing would sound like with a proper cab... and how much easier life would be with a bass amp that behaves as it should ;)

I would really like to make a proper cabinet for this, either a double baffle or a regular single baffle. I'm not too picky and would welcome suggestions for which would be best for the studio.

However, I cannot find a source for accurate plans for either. I know about Fliptops and Vintage-Blue but unfortunately there isn't the budget right now and honestly I'm a cabinet maker by hobby and have a full wood shop in my basement as well as access to good baltic birch and lumber .

I've made a few EV TL-606 and 806 custom cabinets as well as some really nice hi-fi speakers... how much harder would a Portaflex cab be? I'd love some help getting measurements and details on what Mark mentioned above.

Seriously though if we had the money for a Vintage-Blue we would just buy one of those... but this seems like the most economical option giving my skills. Also it leaves me the ability to add any features that may be useful in the studio.

Any help would be awesome!

Cheers,
David
 
#7
david, sorry i can't help you with building, but ever think of trying one of those ev cabs you built with it? i'll bet it would kill. a proper double baffle cab would be very cool indeed, but the ev cabs would also rock hard.
 
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#8
We have a Dietz (EV copy) at the studio... but I think ditching this abomination of a cab and replacing it with a spec'd portaflex one would do well to give the studio a little class and variety.

Also I'm excited for the project...

BTW: how are the Fliptop single baffle cabs? Does Bruce use felt under the grillcloth and proper spacers, etc with these? I hear they are nice but still sometimes are prone to some buzzing.

Is it true that the single baffle design has a deeper bass?

Does anybody know what Hz these enclosures are tuned to? They seem to be regular Helmholtz boxes but the unconventional porting makes it hard to measure in any box-plot program...
 
#10
Bump!

I'm making a bunch of TL606s for people next week and ordering up a bunch of Baltic Birch... would love to make this Portaflex cab at the same time.

I could really use some more measurements... I'm not hellbent on a double baffle so if any folks wanna take some measurements on there single baffle cabs I would greatly appreciate that equally.

Cheers,
D
 
#11
i can't remember where in the portaflex club threads those measurements are posted for the double baffle, but i'll try to find them tonight later. i'm pretty sure it's somewhere in the 2nd thread.
 
#16
Tronographic said:
Wow! thanks for the link. there's a bunch of good info in there.
Click to expand...

Glad it's useful to you. There's still some information missing if you have to build one.

This is a cab design I became curious about after I saw JimmyM mention it in an earlier thread. I own a Magnavox-era Portaflex, but it's on long-term loan to a friend in another state. I have never looked closely at that cabinet.

Back to the DB cab... tonight, I'll try to reconstruct some of the missing dimensions from photos. Will post what I come up with, unless that would violate someone's intellectual property rights. ??
 

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