B15 type amp and double baffle speaker cab build

[dr_root]

Hi everyone,

Ever since I started playing bass and I got to knew the ampeg b15, I always wanted to have a 1964 b15. I've never played a real B15 myself, however I watched a lot of videos of people playing it and fell in love. I'm pretty hooked by the sound of the early 60th versions.
A few month back I decided to build an b15ish amp and a double baffle speaker cabinet. Even though I've never build neither an tube amp nor a speaker cabinet, I dared to tackle the challenge.
The amp is not going to be an exact copy but a simpler version than the original b15. It will only have one channel. However I am planning to add some useful features like an integrated load at the output transformer. Further I will add a Bo Hansen type DI to the through signal, the preamp out signal and to the secondary of the output transformer, respectively. This will become handy when the amp will be used in a recording situation. I am not quite sure about how the integrated load will be implemented, either resistive or in form of an reactive speaker emulation...this also depends a bit on how much space is left in the housing and time will tell. I already started working on the turret board, however up to now I spend most of the time working on the cabinet. In the upcoming Christmas vacation I'll try to work on the amp and get it done. The amp is not going to look like an b15 but rather like the (I believe discontinued) Shaw audio roctal amp..I dig the look.
Now let's talk about the double baffle speaker cabinet. I managed to finish it last week..it was a slow on and off process and took a few weeks. The result is imho quite pleasing though. I made most of it it out of 18mm (sorry, no inch measures, I'm from Germany ) birch plywood. I bought the tolex at fliptops and it looks pretty amazing. I decided to use an eminence beta 15a because fliptops recommends it for their cabs. Anyways, here are some pictures.

Cheers
root

 

[MarkA]

The cab looks solid! Hope the sound and function of the whole package end up being what you're aiming for.

 

[lucas303]

Forgive me if this is a stupid question, but what is the purpose of the double baffle?

 

[JimmyM]

Forgive me if this is a stupid question, but what is the purpose of the double baffle?

There are much more elegant ways of porting cabs these days, but the double baffle stands as one of the earliest, if not THE earliest example, of porting a bass cab. And it worked very well, revolutionized the world of bass cab design, and it still holds up 60 years later.

 

[BitMoBass]

Wow ..... Beautiful .... Excellent looking cabinet.

 

[Blues Bass 2]

Very nice work ! Looks awesome !

 

[NKBassman]

Awesome! Following along.

 

[bass4more]

Beautiful! I can't wait to see the amp.

 

[dbase]

I had a 1966 B15..It had a beautiful buttery tone .. If only it was 300 watts.

 

[daveman50]

Beautiful work!.
Here's a simple explanation of the double baffle from the Talkbass Portaflex Wiki:
Technical - Speaker Cabinet | TalkBass.com

 

[Pdaddy1978]

My hats off to you friend.
Like you, I've always wanted a real deal B15.
But the idea of "can't buy one so I'll build one" is way out of my wheelhouse.
Looking forward to hearing how yours turns out!

 

[TransylvaniaE]

There are much more elegant ways of porting cabs these days, but the double baffle stands as one of the earliest, if not THE earliest

Fender Showman 1960
Also had a ported 1x12 and ported 1x15
Otherwise known as the tone ring cabinets.
both standard with JBL Speakers.
100 watt amplifiers

Either way seeing both examples in today's world
Still give me goosebumps.

 

[kesslari]

Dang, that's nice work!

 

[beans-on-toast]

Forgive me if this is a stupid question, but what is the purpose of the double baffle?

Here’s a visual. Backwards going sound waves from the cone are directed towards the back and corners and routed out the front ports.

 

[beans-on-toast]

Hi everyone,

Ever since I started playing bass and I got to knew the ampeg b15, I always wanted to have a 1964 b15. I've never played a real B15 myself, however I watched a lot of videos of people playing it and fell in love. I'm pretty hooked by the sound of the early 60th versions.
A few month back I decided to build an b15ish amp and a double baffle speaker cabinet. Even though I've never build neither an tube amp nor a speaker cabinet, I dared to tackle the challenge.
The amp is not going to be an exact copy but a simpler version than the original b15. It will only have one channel. However I am planning to add some useful features like an integrated load at the output transformer. Further I will add a Bo Hansen type DI to the through signal, the preamp out signal and to the secondary of the output transformer, respectively. This will become handy when the amp will be used in a recording situation. I am not quite sure about how the integrated load will be implemented, either resistive or in form of an reactive speaker emulation...this also depends a bit on how much space is left in the housing and time will tell. I already started working on the turret board, however up to now I spend most of the time working on the cabinet. In the upcoming Christmas vacation I'll try to work on the amp and get it done. The amp is not going to look like an b15 but rather like the (I believe discontinued) Shaw audio roctal amp..I dig the look.
Now let's talk about the double baffle speaker cabinet. I managed to finish it last week..it was a slow on and off process and took a few weeks. The result is imho quite pleasing though. I made most of it it out of 18mm (sorry, no inch measures, I'm from Germany ) birch plywood. I bought the tolex at fliptops and it looks pretty amazing. I decided to use an eminence beta 15a because fliptops recommends it for their cabs. Anyways, here are some pictures.

Cheers
root

Good job. If it sounds as good as it looks, you’ll be well ahead.

So what was the hardest part?

 

[iiipopes]

I have played through an "original" B-15 Portaflex, complete with the XLR plug for the speaker plug. Two observations, both having to do with the small physical volume of the enclosure, in spite of the porting:

1) Efficiency. Because of the design limitations, the originals are not too efficient. The trade-off for extension of response is reduced efficiency.

2) Compliance. Choice of driver with the proper compliance to the cabinet specs is critical. Too loose, and you get speaker farts at anything above a bedroom volume. Too tight, and the cabinet will have a really annoying hump in the mid-bass response, effectively killing any character of the bass played through it.

 

[JeezyMcNuggles]

Hi everyone,

Ever since I started playing bass and I got to knew the ampeg b15, I always wanted to have a 1964 b15. I've never played a real B15 myself, however I watched a lot of videos of people playing it and fell in love. I'm pretty hooked by the sound of the early 60th versions.
A few month back I decided to build an b15ish amp and a double baffle speaker cabinet. Even though I've never build neither an tube amp nor a speaker cabinet, I dared to tackle the challenge.
The amp is not going to be an exact copy but a simpler version than the original b15. It will only have one channel. However I am planning to add some useful features like an integrated load at the output transformer. Further I will add a Bo Hansen type DI to the through signal, the preamp out signal and to the secondary of the output transformer, respectively. This will become handy when the amp will be used in a recording situation. I am not quite sure about how the integrated load will be implemented, either resistive or in form of an reactive speaker emulation...this also depends a bit on how much space is left in the housing and time will tell. I already started working on the turret board, however up to now I spend most of the time working on the cabinet. In the upcoming Christmas vacation I'll try to work on the amp and get it done. The amp is not going to look like an b15 but rather like the (I believe discontinued) Shaw audio roctal amp..I dig the look.
Now let's talk about the double baffle speaker cabinet. I managed to finish it last week..it was a slow on and off process and took a few weeks. The result is imho quite pleasing though. I made most of it it out of 18mm (sorry, no inch measures, I'm from Germany ) birch plywood. I bought the tolex at fliptops and it looks pretty amazing. I decided to use an eminence beta 15a because fliptops recommends it for their cabs. Anyways, here are some pictures.

Cheers
root

You can get the old school ampeg logo plate for that off fliptops.com

 

[Redbrangus]

Here’s a visual. Backwards going sound waves from the cone are directed towards the back and corners and routed out the front ports.

View attachment 4083054

Except now, in the fullness of time, we understand what's happening a little differently... right?

 

[TransylvaniaE]

For the most part.

Reflex or Ported or Vented cabinet is a newer term from the early 70s
After Neville Theile was awarded his PHD degree in 1972 and the 9 papers he published. Consider now a classic for electrical acoustic science.

Prior to that Dr John F Blackburn Designed and established equations for a ported cabinet in 1935 for the Altec Lansing Iconic.
He used the terminology
" Resonating Baffle" which is essentially what we now consider a Reflex Cabinet.

 

[beans-on-toast]

Except now, in the fullness of time, we understand what's happening a little differently... right?

Yes, cabinets both suck and blow, as speakers do.