Wow! It looks amazing! Is that a giant passive radiator on the back? I'm wondering how low can it go. Would you mind doing a nearfield measurement? And how does the bass sound compared to common bass-reflex speakers?
I wanted a Jeff Bagby designed speaker.
It is important to keep the position of the tweeter from the baffle edges the same. and the relative driver (midwoofer) positions the same.
Any changes to the drivers require a crossover redesign. And the crossover is the heart and brain of any speaker design.
I have seen the MW13TX measurements but given the strengths of Jeff's design, I haven't felt compelled to re-design it.
Jeff was commissioned by SB Acoustics to design a speaker around the 5x8" passive radiator and beryllium tweeter SB29BAC
https://sbacoustics.com/product/5x8in-sb15sfcr-00/https://sbacoustics.com/product/sb29bac-c000-4/
The fact that he paired it with the MW13P-4 to get an in-room response of down to 40Hz, and a sensitivity of 85dB/2.83V in only 7 liters is one of the things that make this a great little speaker.
A few, crossed over correctly to a subwoofer, would make a sensational home theater setup.
But a pair is also great for (smaller room) music listening.
Here's what Jeff himself said about his Revolution Mini Reference
"OK guys, if you are interested in building either the original Revolution speaker, or the Revolution Mini Reference with either the Beryllium dome or soft dome tweeter here are the crossovers I used. Responses are very flat. I will try to post one below, but I will have to get it from a different computer. The Mini cabinet is 7 liters, and is flat to about 50 Hz, with good output into the low 40's, and that is very rare. Dimensions are 13" tall x 8" wide x by 7.5" deep. The larger Revolution is 13" tall x 8" wide x 13" deep. Both have the new SB Racetrack passive radiator mounted on the back with no additional weight added. Both have Dacron polyfill behind the drivers but none right next to the radiators. Meniscus or Madisound would be glad to provide you with drivers. Meniscus will even sell you assembled crossovers if you want. If you're ready for something special, here's your chance.
Jeff Bagby
22/10/2018
(comment from: DIY Project Pad group @ Facebook)
I understand that this was the last small speaker designed by Jeff.
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@tktran303 could you let me know how the Revolution Mini's perform in near wall situations? Reading what Jeff said, I think I might be better building his Sopranos as they are designed for flexible placement, near wall and desktop.
Apparently the Continuum's are easy to place as well, but 8.5" depth... I'm trying to get 8" depth or less.
If you could let me know, I'd appreciate it.
Apparently the Continuum's are easy to place as well, but 8.5" depth... I'm trying to get 8" depth or less.
If you could let me know, I'd appreciate it.
Or, I building it sealed without the racetrack and lose a bit of low end extension.... I'd still have more output than the 4" used on the Sopranos.
The revelation be i have is particularly open sounding, i attribute it to the passive radiator at least not reducing the size of the rear wall if not absorbing part of the internal ringing.
Combined a birchply, its pretty impressive!
Built a Rev mini for friend, no issues in near wall situations.
How near?
In my experiences the rear passive radiator (or port) needs a few inches from a boundary to function correctly. A minimum of ~ 1-2” from the rear of the Rev mini cabinet to the wall will suffice.
In my main listening room (4x5m) the speaker was setup in a way that the front baffle is 20” front the wall, It sounded just right.
Further out into the room you get better imaging but lose some low bass.
I did try it closer to the wall, in a smaller room, as a single speaker, simulate a mono setup and replace a typical Bluetooth speaker and the bass becomes too much, and the quality was over the top of a bedroom/BGM listening.
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1-2 inches would make it pretty flexible, but as you say if the bass becomes overblown then I might be better with the Sopranos… or just exclude the passive rad and tweak the design of the Revolution slightly to match the boundary gain.
Troels 3WC bookshelves are actually designed to be on a wall or corner, great design but somewhat big for my application (office desk close to wall)… there aren’t really many DIY speakers that are designed for this position, almost all are intended for free space.
Troels 3WC bookshelves are actually designed to be on a wall or corner, great design but somewhat big for my application (office desk close to wall)… there aren’t really many DIY speakers that are designed for this position, almost all are intended for free space.
A sealed box works well when you are that close to a wall. Maybe make as ported tube reflex and plug when near wall. Release for more bass when away from wall.
tktran303,
I notice jeff uses 4ohm drivers. Questions:
1. DId you use 4 ohms?
2. if you drive xover from a single amplifier can driver impedances pose any problems to the amplifier with both drivers at 4 ohms?
I notice jeff uses 4ohm drivers. Questions:
1. DId you use 4 ohms?
2. if you drive xover from a single amplifier can driver impedances pose any problems to the amplifier with both drivers at 4 ohms?
Why do you ask - you running tube amps? Just use an amp that is stable at 4 ohms and of sufficient power for the speakers rated sensitivity… job done.
Do you know the lowest impedance? I not sure you know if so don't push it aside.
Check out the graph of the woofer, it doesn’t drop beneath 4 ohms
http://sbacoustics.com/wp-content/uploads/2020/02/5in-SB15CAC30-4.pdf
http://sbacoustics.com/wp-content/uploads/2020/02/5in-SB15CAC30-4.pdf
I can confirm that although both drivers are 4 ohm nominal, the complete speaker system never drops below 4 ohms:
Depends the size/dimensions of your room, and how you like to listen. In my previous room 4x5m room with the speaker baffle 50cm from the front froom it was a was a good match:
My current (2022) room is 4.8m x 6.4m x 3.2m.
My speakers are along the 4.8m wall, 2.4m apart, baffle 0.5m from the front wall.
When I place the Revolution mini in this room, it's clear it cannot play at live levels (eg. nightclub, pre-Covid, remember those?) with the assistance of a subwoofer:
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Edit: Measurements in CTA2034A standard (50dB scale) in original post.
PS. To do justice to Jeff's design, the original Beryllium dome (and complete spinorama) is in the works...
PS. To do justice to Jeff's design, the original Beryllium dome (and complete spinorama) is in the works...
I'm bumping this thread, and am interested, @tktran303, in any results with the Be tweeter as well as whether you've continued to enjoy these. As may be the case with some of JB's other designs, the quantitative measurements seem just OK (big scoop from 1-6K, directionality just OK and could suffer at the high end if the Be tweeter is tamer up top), yet the listening experience is described as great including great imaging.
I'm currently shopping for a design (or starting point) for a build meant to be an heirloom gift and in this case something compact and suitable for less-than-live volumes in a mid-sized room is what I'm looking for.
Any further impressions, etc. appreciated!
I'm currently shopping for a design (or starting point) for a build meant to be an heirloom gift and in this case something compact and suitable for less-than-live volumes in a mid-sized room is what I'm looking for.
Any further impressions, etc. appreciated!