I miss my radio shack mach ones

[Stash]

Despite all the negativity conjured up whenever someone mentions RADIO SHACK, I miss that retailer. During the 70's & 80's they offered many fine components and an enormous assortment of speakers systems.

I bought a pair of MACH ONE speakers in the latter 70's. The 40-4024A. My very first hifi purchase. And I've always regretted not keeping them.

To rebuild them using many 40 year old parts does not really make sense to me. So, I redisigned the MACH ONE with modern components.

Of course, I used the GRS MACH ONE REPLACEMENT WOOFERS from PE. And, yes, these woofers do offer the same warm bass tones as the originals.

I found a NIPPON bi-radial horn lens measuring 16.5"x 6.25" x 9" which approx mimicks the original MACH ONE horn (16.75"x 4.5" x 9"). These NIPPON lenses offer curved protruding lips reminiscent of the MACH ONE horns. Their bi-radial design provides exceptional spaciousness and an almost 3-dimensional sound. Very nice. The throat is a standard 1.375" x 18 TPI with a metal threaded insert.

As for the midrange horn driver, I used a TIMPANO AUDIO compression driver, purchased from PE. These TIMPANO drivers are solidly built of die cast aluminum, much superior to the original horn drivers. The TIMPANO diaphragm is Phenolic, which I chose to keep the same as the originals. Phenolic diaphragms tend to sound natural as compared to metal midrange diaphragms. The TIMPANO diaphragm measures 2" diameter. This is a good size for a mid-driver and is less likely to distort near the lower crossover point.

The original MACH ONE employed a plastic small rectangular bullet horn super tweeter. I found a pair of PYRAMID super tweeter bullet horns here at PE. The overall dimensions of these horns is 3.375" diameter. They are solid die cast aluminum. Again, much superior to the originals. Their actual horn measures 1.5" diameter. These horns use a Titanium diaphragm and are ferro-fluid cooled. This fluid also aids in damping diaphragm movement.

My old MACH ONE speakers featured crossover points of 1,200Hz and 4,500Hz. I always felt they sounded slightly shrill and/or pinched in the midrange/treble region. The original MACH ONE crossover was 800Hz and 8,000Hz. I decided to go with the original design, as they are said to sound the best of all the MACH ONE versions.

i researched the MACH ONE crossovers. I cannot find any modern crossover model which corresponds to the crossover components of the original MACH ONE. For instance, the originals employed a 33uf cap with a 3mH coil for a -12dB low-pass 800Hz woofer crossover point. These values do not correspond to Riley-Linkwitz, Butterworth nor Besel 2nd order crossovers.

Also, I may have found a flaw in the original's crossover design. From what I could find, the originals incorporated 2 resistors, 4 caps but only 3 inductors. Therefore, it is my guess the MACH ONE crossovers offered -12dB slopes for the woofer and bandpass, but may have only offered a -6dB 1st order crossover for their super tweeter. This may account for the shrillness I sometimes noticed, due to excessive overlapping of mid and tweeter drivers as well as the tweeter playing frequencies too near its lower end limitations.

So, using the Riley-Linkwitz model, I designed an 800Hz/8,000Hz full 3-way -12dB crossover utilizing 4 caps, 4 inductors and a 4 ohm padding resistor in series with the PYRAMID tweeters (as they are rated 4 ohms).

The TIMPANO midrange drivers claim a response range of 400Hz to 8,000Hz. This is almost an exact match to the original's midrange of 800Hz to 8,000Hz. The TIMPANO's suggested lower crossover point is 500Hz.

The PYRAMID super tweeters have a claimed extended response up to 25,000Hz. This is also an exact match to the original MACH ONE tweeter's claimed response of 25,000Hz.

I also bought 15 watt 8 ohm mono L-pads from PE. The original MACH ONE offered mid and tweeter level controls. The L-pads are definitely required. As you can see in the pics, the horns are turned down substantially.

Enclosure construction is simple 5/8" particle board with a vinyl laminate birch wood finish. The baffles are painted gloss black.

The original MACH ONE featured an internal shelf which separated the midrange section from the woofer compartment. I also included this shelf. The shelf also acts as cabinet reinforcement.

The original MACH ONE featured removeable rear panels to access the mid and woofer compartments. I chose not to do the same.

The original MACH ONE had poly or fiberglass damping suspended from the internal shelf, behind the woofer, not unlike curtains on a window. I used about 0.6lbs polyfill for the woofer section and about 0.1lbs polyfill in the midrsnge compartment. I purposely did not overfill as my experience indicates less is better than too much.

The original MACH ONE grilles were a brown foam type. PE carries 3/8" foam grill material which is easily cut to size and attached via velcro, just as the originals.

The terminal cup is a standard spring-loaded type. The original MACH ONE featured old fashioned screw type terminal connections.

The original MACH ONE measured 28 5/8" x 17 3/8" x 12". My redesigned MACH ONE is 31 1/2" x 17 3/4" x 11 1/4". The difference in dimensions is due to the NIPPON lens being slightly larger in height.

The original MACH ONE had a rough woofer Vc of 1.75ft. My enclosures are approx 1.89ft. Original Fc was rated 65Hz. My Fc should be about 60Hz with a F3 of 63Hz. Originals weighed 65lbs. Mine weigh 59lbs.

The sound is AWESOME! Playing MARIAN HILL's Breathe, I cannot believe the depth of her voice. Treble is extremely smooth and subtle. No harshness whatsoever. Bass is full and deep. As stated in the beginning, the sound is almost 3-dimensional. I love these speakers. Very impressed with the outcome.

I have a YAMAHA 5.1 receiver which I play in 2 speaker stereo mode for music. All tonal controls/EQ flat except for a 2.5dB boost in BASS control (50Hz).

[Stash]

Some additinal pics of my redesigned MACH ONES

[blue934]

I love it! I keep thinking of doing a project like this to replace a friend's Mach Ones since she lost them yrs ago.

[Stash]

Go for it! Construct an 800/8,000Hz 2nd order crossover. Make certain to include L-pads, unless you prefer your music extrememely bright.


The spaciousness and definition of these redisigned MACH ONES is phenominal. Very accurate and detailed. And surprisingly, my wife likes the look lol. A win-win for me.

[blue934]

17" x 6" ABS Plastic 1 3/8" Bi-Radial Screw-On Horn Flare for Speaker Cabinets - listed on the Bay.
Is this the horn you used? I don't see the exact size you quote.
Or maybe this one on Carid?
NIPPON America NTX617 - 6" x 17" Horn Lens

[Stash]

The horn midrange lens is a NIPPON NTX617. It also goes by the brand AUDIOPIPE NTX617. They are identical. To my understanding NIPPON and AUDIOPIPE are related brands or owned by the same parent company.

I found the least expensive vendor was JBTOOLS, believe it or not. About $15 each plus $9.99 shipping. Received them in less than a week.

Look around. Many ebayers charging double or triple the price. Same goes for Amazon and Walmart 3rd party vendors.

[JazzyG]

Great job, man! Way to take your dream and make it a reality with some ingenuity and hard work. I did not appreciate Radio Shack as much as I should have back in the day, they truly did have some neat designs. I modded some LX5's and have them in my bedroom now, cool little die cast aluminum speakers! How long did it take you to design and construct them?

[Stash]

I spent a several days researching the original MACH ONE crossovers. I tried to find actual pics of the crossovers to see for myself how they were constructed.

Then I spent about a week debating on a midrange horn. That is when I happened upon the NIPPON horn lens, which is just about a perfect replacement.

I relied on PE for the rest. The tweeter, woofers, crossover components etc. I looked for bargains in PE closeouts.

I then designed the enclosures. As I had owned the MACH ONES many years ago, I remember the basic design. I simply looked up old pics and RS catalog references regarding the original MACH ONE to detetmine dimensions, crossover points, system resonance and so on.

It took me two days to cut all the panels for each speaker and assemble them.

I used 5/8" particle board shelving from Lowe's, sold in precut pieces 11.25"x 48" x 5/8". These shelving pieces were cut to size to form the sides and top/bottom.

I bought 2'x4'x5/8" particle board from which I cut the baffle, rear and internal isolation shelf which separates the midrange chamber from the woofer chamber.

I used 1"x2"x96" wood strips to make the internal framing.

Wood glue (yellow), caulking assorted screws and some nails. I will post additional pics detailing construction of the enclosures

[Stash]

I'm not great with woodworking. Made mistakes as I went along.

Basically, cabs are 31.5"x17.75"x11.25" .
baffle panel is 30.25"x16.5"x5/8".

Woofer cutouts 13.75"
midrange cutout 15"x 5"
Tweeter cutout 2.875" plus notches for terminals.
I drilled 7/16" holes for each L-pad. L-pads are 1 inch stems.
(I made mirror imaged pairs. The L-pads are on the left side of one speaker and the right side of the other).

Center of woofer is 9 inches from bottom of baffle panel.
Center of midrange horn is 3.125" from top of baffle panel.
Center of tweeter is 10 inches from top of baffle panel.
L-pads are 8.5 inches and 11.5 inches from top of baffle panel and 3.5 inches from the right (or left side) of baffle panel..

Rear panel is a 2.25" cutout for spring loaded input terminals.

Enclosures are sinple butt joints. No miter cuts, since I covered with simulated wood laminate.

i bought a couple of 1/8th inch thick rubber-backed carpeted mats from Dollar Tree. I cut them to size and glued and screwed them to the interior sides of the woofer chamber to reduce bass resonance. See bottom two pics. First is rubber backed mats upside down and cut. Last pic is carpeted mats installed inside woofer chamber.

I had a king sized pillow I didn't like, which I ripped open and split the polyfill betwern the two enclosures (about 0.7lbs each).

The simulated vinyl wood laminate is from Dollar Tree. Two rolls per enclosure plus some extra tacky spray glue, also from Dollar Tree.

[Stash]

Additional pics

[johnnyrichards]

This is why we DIY. Awesome job!

[Stash]

Thx 👍.

[tomzarbo]

I also have a deep love also for some of Radio Shacks offerings back in the day. They were making some really nice looking and sounding speakers back then, and I still honestly like the look of some of them 30 some years later.

I miss my smaller pair of 12" three-ways I had at the time also and had at one point considered making an 'homage' speaker pair based on a RS speaker I loved but never owned....

But Dang...YOU went there!

I love it!!!

TomZ

[Stash]

Well, PE carries a pretty good variety of drivers. Some are similar to drivers carried by RS back in the day. In fact, I just had this conversation with one of my nephews. We were looking at tweeters similar to the old RS 1-inch recessed soft mylar domes with large 8-10oz magnets. PE carries one or two which are vitually identical, except their dome material is silk fabric vs mylar, which is an acceptable trade-off.

Many PE pre-constructed crossovers will work. I custom built my crossovers to reproduce the sound of the original MACH ONES. Building your own is not difficult. Only time consuming. I used a piece of 1/8th inch thick hardboard, 6"x 6", for each crossover board. Simple hotglue holds all components onto the board. All components connected with leads and jumper wires. More time consuming than anything. I also searched online for crossover calculators. Google "ersa crossover calculator". This calculator provides many combos for 2-way and 3-way, 1st, 2nd, 3rd and 4th orders. Def a good place to begin.

Building the cabs is also a bit of work. However, you will feel a sense of accomplishment in the end. And it is nice to hear others compliment your finished product.

Most people know very little regarding electronics in general. Building something as simple as a pair of nice floor standing speaker systems seems like an impressive feat to many.

I like my redesigned MACH ONES. They remind of an era long gone. They sound nice. I guess, anyone can buy a pair of decent speaker systems. But no one will own a pair like mine. This fact makes mine special.

[RedK9]

So if these have an F3 of 60hz, what is the F10..? In the 1978 catalog it says they can play down to 20hz. So the 20hz must be around the F30 mark..?

[Stash]

The F3 is around 60Hz. Maybe a few hertz lower due to the effect of damping material.

Acoustic suspension systems typically slope at about -12dB/octave. Therefore, an approximate low end response of 25-30Hz at -15dB is a realistic expectation, for these speaker systems.

I say, "these speaker systems" to make a point. These Mach Ones feature large woofers which are capable of true low-end output at reasonable volume levels. Many speakers, especially many tower design speakers nowadays feature much smaller woofers, 5 inch to 6 5 inch. With bass ports, they may deliver claimed low-end frequency response at low volumes. But they are still small drivers. Unless they are very high end, they will distort, bottom-out or rupture at medium to loud volumes. At higher volumes, midrange will be muddied, due to excessive cone movement. My point being, it's not only about frequency response. Small drivers cannot, IMO, deliver the deep full bass of a large driver at medium to loud volumes, nor can they deliver the 'big sound' of a large driver floor speaker system. The sound simply is not the same, in my experience. Even when coupled wirh a larger subwoofer, the big sound of a large old school spealer system is noticably different.

Many old school speaker systems claimed 20Hz-20Khz. Most were overall response ratings, meaning, they were very vague. No reference to a +/-dB variation. That practice still goes on today. However, good quality old school large speakers usually could deliver some bass output down into the lowest bass octave.

The Mach Ones originally were rated 25Hz to 25Khz. I don't think the 25Hz rating is too far off, as speakers go. Once placed in your room, the speakers couple with the floor and walls which will boost some low-end output. I play these speakers FLAT, bypassing all eq/tone settings. They deliver a full clean sound.

It seems to me, many people, especially younger audio enthusiasts mistakenly compare old school large floor speakers to current subwoofer/satalite systems. This comparison is wrong and leads to much confusion.

Back in the 70's and going into the 80's, speaker systems served a very different purpose. Audio systems were primarily for music reproduction only. And recording technology of that time was not as wide ranging as today's recordings. For example, even good quality recordings of that time, by bands such as Pink Floyd or Emerson, Lake and Palmer sound compressed compared to modern recordings. The assumption of that time period was, a speaker system needed to reproduce a band range of about 40-50Hz to 20Khz, in which most music material lies.

IMO, two major changes occured in the 90's. Rap music and the advent of home theater. Rap music began the use of increasingly low end subsonic bass tones. Home theater required the reproduction of subsonic sound effects (explosions, gun fire, etc). Thus, came the subwoofer, to deliver only subsonic bass tones.

Subwoofers and old school woofers may look similar, but are very different in design. True subs are only designed to reproduce the bottom octave or two lowest octaves of bass. Old school large woofers are designed to reproduce a balanced range from low end bass through upper bass and some low midrange tones. Two very different designs with very different outputs.

I personally prefer the sound of old school speakers in stereo mode. Surround sound is nice for movies. But, I hear distortions caused by D-A converters, simulated surround effects, etc, which ruin the music for me. I much prefer listening to music on just these two Mach Ones, bypassing all tonal adjustments, in discreet straight amp, stereo mode. I find these speakers sound their best at moderate volumes. Playing higher end recordings by artists such as Marian Hill, for example, these speakers present a large sound stage. Music sounds natural. Voice is exceptional. Clarity is very good. Music detail and nuance is nice. No distortions.

For me, the subwoofer/satalite systems sound incoherent. They do not sound natural. Great for sound effects. Not great for music reproduction. Music sounds piece-mealed and broken down. Almost digital as compared to old school analogue large speakers.

Whenever comparing old school speaker systems to modern speakers, please keep in mind the goals of those older speakers were quite different from those of today's audio speakers. These redesigned Mach Ones can play rap music quite well. But they still sound balanced. Not terribly bass heavy.

It comes down to what kind of sound you prefer, really. Sorry for the long reply lol.

[Steve Lee]

This post ^ needs to be a sticky!

What more of a beautifully written and excellent explanation for the correct application of drivers can you ask for?

There is NO replacement for displacement.


Thanks, Stash!!

:D

[Stash]

Steve,
Thank you so much for the compliment.

[Steve Lee]

Stash, you put in the effort without being paid and did it well.

You earned my respect and deserve the compliments. (Few these days understand what you did).

Consider this your participation trophy!

:D

PTL and later, mang!


Steve.