McKnight MiniMac "Re-echo" Project, with audio clips

[Tim McKnight]

Sorry that we've been absent from the forum for a while but a lot has been going on in our lives which has spread us pretty thin. We've kept our nose to the proverbial grindstone (work bench) but haven't had much free time to post any build pictures. In between glue drying and finish curing we've been helping our daughter Adrianne with her latest adventure, remodeling an old church built in 1881. She and her fiancé Jeremy are converting it into a home, which is quite the project.

Mary and I have been holding a steady 2 year back log of orders for several years now which has left me zero time to do R&D work, which is a real passion of mine. I've got lots of ideas scribbled on paper and even some drawn up in CAD but haven't had the luxury of time on my side to put those ideas to work. I retired from my day job three years ago and it seems I am busier now than I've ever been in my life. I wonder how I even had the time to actually go to work. Since time has been compressed I decided to schedule a couple of builds just for R&D work because it seems that was the only way it was ever going to get done. Long story even longer, this brings us to the title of this post, the MiniMac Reecho.

Why did we choose the MiniMac model for this project? Well, it’s been our top selling model for over 28 years and I do like building them. The project began with a unique and one of a kind set of Australian Black Heart Sassafras back and sides. We've had this set in our inventory for a LONG time and its one of our favorites to show off to clients when they visit our wood room. It’s one of the most strikingly beautiful sets that we have ever seen.

Unfortunately we've not been able to sell it. You see not all beautiful wood is an ideal candidate to build a musical instrument from. We like to explain the tap tone process to visiting customers and they are fascinated when they hear how woods sound different and unique from each other. Strong and long sustain are always good indicators of the “Q factor” or quality of the back or top when tapped. The better the Q factor is the higher chance that the final instrument will be a great sounding guitar.

Mahogany, Koa, Tasmanian Blackwood, most Rosewoods, Wenge, African Blackwood, Padauk, Osage Orange, Zircote and Pernambuco woods all [generally] have very high Q factors when tapped. In comparison Black Heart Sassafras probably has the lowest Q factor of any wood I’ve ever tapped on. The high Q woods, when tapped, go BahWongggggggggg and seem to have sustain to the moon and back while this set of Sassafras is so dead and lifeless that 12” thick concrete would have a more exciting sustain than this set. Gee I wonder why no one has picked this set to build with. Duh! It may sound like I am shooting myself in the foot and losing any hope of ever selling this guitar but please bear with me.



Here is a picture of the back just to show you what we are starting out with:








I considered using our floating internal “Hollow Back” design which would certainly add life to transform this dead set of Sassafras into an active back and wonderful sounding guitar. I could have also built a Nomex honeycombed core double back to make this back into a passive reflector as we have done successfully so in a few past builds. However, I’ve had another idea on the back burner for far too long and it was time to turn my ideas into wood.

I thinned the Sassafras back out to about 1/3 the thickness of a normal back to reduce weight. Next I laminated (you must be joking right) a very thin mahogany inner back to bring up the Q factor and increase the structural stability of the Sassafras, then added my radial bracing pattern to the inner mahogany back and the back was beginning to have real potential when tapped. The back's tap tone and Q was vastly improved and much better than most of the lower Q woods I’ve built with like; Walnut, Maple, Zebra Wood, Cherry, Oak, Myrtle and Hickory. When tapping the braced and voiced back it still had some room for improvement to increase its chances of being a phenomenal sounding guitar.

The end goal all along was to transform the dead and lifeless Sassafras back into a powerful "active" back that would sonically couple with the top. The last step was to finally employ my “Re-echo design”.

Any guesses what the reecho is?

[Lonzo]

.. and good looks.
Reecho like re-echo.... so maybe some structure applied to have sound reflected not only once ?

[Steve Kinnaird]

Lovely set, Tim! Did that come from our old friend Tim Spittle?

SK

[SJ VanSandt]

Originally Posted by Lonzo

.. and good looks.
Reecho like re-echo.... so maybe some structure applied to hav sound reflected not only once ?

That seems like a good guess. Personally, I don't have a clue, but I will be following along closely for sure! I've missed your build threads, Tim!

[Tim McKnight]

Originally Posted by Lonzo

.. and good looks.
Reecho like re-echo.... so maybe some structure applied to have sound reflected not only once ?

Your on track Alonzo and yes it’s re-echo.

[Tim McKnight]

Originally Posted by Steve Kinnaird

Lovely set, Tim! Did that come from our old friend Tim Spittle?

SK

Yes it did Steve. Do I vaguely remember you building one with almost a sister set to this one?

[Tim McKnight]

Originally Posted by SJ VanSandt

I've missed your build threads, Tim!

Hey thanks Stan. I’ve missed being around here too. I hope to post more pictures in the coming days and weeks. I’m trying to get this one finished in time for the Artisan Show in April.

[David Wren]

Hey Tim ... really looking forward to this build thread! We've all worked with some highly figured backs where the grain was so wonky that it was mostly end grain (highly quilted Sapele comes to mind) and have used every trick in the book to get these woods responsive. I'm interested to see your approach!

[gitarro]

It's always interesting to see luthiers push the envelope so I'm going to be keeping a close eye on this thread!

[The Growler]

Good to see you back Tim. You've been missed.

I enjoy your build threads. I always learn something new.

[TomB'sox]

Also glad you are back and am very interested in what you have planned here. Seems like there are a lot of cool innovative builds going on right now whether it is a new design or cool unusual woods or both from traditional to modern looks!

We are lucky to have such talented people as members of the AGF.

[Tim McKnight]

Originally Posted by David Wren

Hey Tim ... really looking forward to this build thread! We've all worked with some highly figured backs where the grain was so wonky that it was mostly end grain (highly quilted Sapele comes to mind) and have used every trick in the book to get these woods responsive. I'm interested to see your approach!

Thanks for following along David.

Originally Posted by gitarro

It's always interesting to see luthiers push the envelope so I'm going to be keeping a close eye on this thread!

I truly miss pushing that envelope so stay tuned for what I anticipate is an interesting push.

Originally Posted by The Growler

Good to see you back Tim. You've been missed. I enjoy your build threads. I always learn something new.

Hey thanks Growler.

Originally Posted by TomB'sox

Also glad you are back and am very interested in what you have planned here. Seems like there are a lot of cool innovative builds going on right now whether it is a new design or cool unusual woods or both from traditional to modern looks!

We are lucky to have such talented people as members of the AGF.

Thank you Tom. Its good to be back again. Please stay tuned...

[Tim McKnight]

I am firmly convinced that the back plays a very vital role in the overall tone and volume of the guitar. Not that you need convincing but here is an experiment that I would like each of you to do and then please report back what you heard.

Lay your guitar case flat on a level surface. Open your guitar case but don't remove your guitar from the case. The neck should be toward your left and the lower bout should be on your right as you stand in front of the case. Take your right pointer or middle finger TIP and tap vertically, several times, on the center of the guitar's bridge. Listen to the volume, sustain and overall sound it makes. Commit those sounds to your memory.

Next place your left hand under the peg head or nut and raise the neck to about a 45* angle. Do not touch or dampen the strings. The bottom of the guitar should still be resting in the case and the guitar's back should not be touching the bottom of the case. Be conscientious of the case's lid and don't allow it to flop closed. Take your right pointer or middle finger TIP and tap vertically, several times, on the center of the guitar's bridge. Repeat both exercises a few times.

Does one position, with the guitar laying flat or elevated 45*, sound different from the other and if so how?

[Tim McKnight]

^^^ Did anyone try the experiment in my post above? ^^^If so, please post your results. Thanks...

[canuck7]

I tried it on my Goodall Maple b&s/Cedar top...I can’t tell any difference with resonance, sound output or character. Could it be that my case doesn’t dampen the back quite as much as another case would? Case is not totally snug. I repositioned the guitar and the same result...
Jeff