Possible monitor/monkey box/coffin group project

The topic of a possible monitor/monkey box group design project using less expensive drivers has arisen in the open source monkey box thread. This is a post to gauge potential interest.

Initial spec:
  • large monitor with a height around twice the width and a depth similar to the width
  • suitable for retro monkey coffin visuals
  • clean output at standard levels (80-85 dB average) at 3-4m and down to 30-40 Hz
  • well controlled radiation pattern with a relatively narrow width compared to towers
  • flexible placement and orientation:
    • vertical on a short stand or low shelf
    • horizontal on a higher shelf or for a centre speaker
    • on/in wall
  • versions:
    • straightforward to build with bought drivers and perhaps bought waveguide
    • more complex to build with project designed and manufactured waveguides
  • replaceable midrange/tweeter assembly
  • most versions suitable for passive crossovers
  • standard range drivers and components

Working files on the project are kept here. If you wish to edit and add files please request permission and your google id will be added to the group.

A website and repository for scripts is here. If you wish to edit and add files please request permission and your github id will be added to the group.
 
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Most of the desirable monkey coffins from the 70s seemed to have 12" drivers: AR-3A, Yamaha NS1000, Wharfedale Dovedale, Celestion Ditton 66, JBL L100, etc... I don't disagree that many people these days like small speakers but I had assumed for a project that has monkey coffin as an objective something like a 12" woofer would follow. Open to debate of course.

There are pros and cons with polls. They equally weight votes from casual observers and the few people that wish to get actively involved with the project. The latter needs to be given more weight w.r.t. decision making otherwise following the results of polls is likely to come up with a design that none of those initially prepared to contribute is particularly interested in designing and building. So long as it is understood that solid posts from people willing to contribute will trump the results of polls what questions should we have in the polls? Size of woofer, active/passive, woofer loading.

Not sure I understand the comment about looks. What is poor about the looks of a 12" woofer, 3-5" midrange (plus 1" tweeter in waveguide) in a wooden monkey coffin?
 
Troels uses a 6” mid (6RS140) in his 12” Faital pro monkey coffin. Maybe a decision on desired efficiency and amplifier friendliness narrows the choice down? There are affordable 3” dome mids, see the relevant thread, which recommends the Scan D7608, not sure if it pairs with an efficient 12” woofer.
 
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...what questions should we have in the polls? Size of woofer, active/passive, woofer loading.

Agreed, those willing to build the project should contribute accordingly and their desire should count.
Questions for polls:
  • cabinet size
  • woofer size
  • woofer loading
  • driver(s) hi-fi and/or PA
  • loudspeaker placement (shelf/2Pi or free space)
  • active or passive
 
Reading the other thread which precipitated this one, there was talk of avoiding boutique parts for those that feel they aren't necessary. In any case there are those who would accept a challenge to create a high performance system from commonly available parts.
 
The 12" goes better with the Monkey Coffin theme, but a 10" may be more practical. Smaller than a 10" and its not a monkey coffin, its just an 8" three-way speaker. I'd go 12" to stick to the "Monkey Coffin" theme.

If you are going to use a waveguide on the tweeter, consider even going to a 6-1/2" midrange, or 5" at the smallest.

Plenty of good affordable drivers to pic from once the preliminary design decisions are made.
 
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I thnk you should first set some goals that the speaker needs to reach before you start discussing drivers. What response, sensivity, dispertion and how big can the speaker be. Then you can start discussin drivers and layout. But there are several 10" woofers that can give you that big monkey box experience. 12" was used in the past, but drivers did become better and many of today's 10" drivers can do better than many 12" drivers of that time.

But the id of a lower cost monkey coffin is not bad, that original tread became far from what most want from a monkey coffin I think, it became a high cost high end speaker that looks like a monkey coffin but is very complex like a studio monitor.

The SB Gema kit is an example of what it could be, but it has some issues with the crossover and driver choice i heared (not first hand info).
 
So let's set some goals first. I think a 85dB sensitivity (if passive) with a max volume of +105db and a 40hz-20Khz response more or less flat to a harman curve is a quiet good target. and that all in a 75 to 100L cabinet (external volume). I think most will want this passive as the original monkey coffins were, a kind of set and forget that works with all kind of amps.

What do you think.
 
So let's set some goals first. I think a 85dB sensitivity...
What do you think.

Those willing to invest in building one should agree on the driver size and cost first. Sensitivity and other concerns could
be established then. If I were interested in building one, I'd like a certain quality standard built into this technology and this is in close
relation to its price.
 
What do you think.

I think you are spot on. I was mentally continuing on from where I dropped out of the previous project but suggestions like 8" woofers strongly suggest a need to establish/re-establish the theme and/or outline spec.

A first go subject to revision:
  • Shape. Retro 70s monkey coffin style in having a wide baffle and not being particularly deep. Large monitor rather than floorstanding. Upright and side use if practical.
  • Size. Large by modern standards but possibly a bit smaller than 70s speakers. The Wharfedale Dovedale is perhaps a good example in originally using a 12" woofer but with the modern retro version opting for a 10".
  • Budget. Not a low budget, high output party speaker. Not an expensive speaker using prestige/premium/boutique drivers. A speaker using good standard range drivers in order to achieve a high technical performance for the price with good design.
  • Technical performance. Clean output at standard levels (80-85 dB) at 3-4m down to 30-40 Hz given large main speakers tend to need highish clean output to justify being large. Lean towards maximizing performance w.r.t. low distortion, radiation pattern rather than, say, retro large light resonating cones.