The Natural Reference One

Cabinetry by Lee Taylor of Taylor Speakers.

Tweeter by Mundorf, Woofer by ScanSpeak. Crossover caps uses the latest Clarity CMR, Mills and Jantzen copper foil inductors.

Introducing the LM-1S

If you are looking for the simplest possible speaker project that is affordable, uses a traditional box, and provides very good sound for the money this may very well be it. Your total cost should be around $195 for the pair, assuming you have all the tools.

The S here stands for simple. The LM-1S uses the same size cabinet as the LM-1 but foregoes the multi-way / multiple driver design in favor of a single full-range driver. As a result we loose the absolute fidelity to the top three octaves the LM-1 has, but we cut the cost in half. Perhaps the S should stand for Surround instead, as these speakers would make ideal companions to a home theater system with the LM-1/LM-1C at the front. 

Compared to the LM-1, the LM-1S is MUCH cheaper, has only 1 driver and no crossover components at all.

The Italian made 4" FaitalPRO 4FE35 has good frequency extension up to 20 kHz and really quite decent off-axis response.

The treble response seems to be a bit peaky on-axis, but this can be adjusted by turning the speakers away from the listener. Compared to boutique full-range speakers, this little gem is really pretty awesome. With the large diameter cone acting as woofer and tweeter you may even find this speaker is unusually clear at a distance compared to more traditional speakers with normal 3/4" to 1" tweeters.

Ported vs. Sealed Cabinet

Visually, the cabinet is a little large for the driver, but that's how we get the 65 Hz cut off. 7L is actually a compromise volume, with WinISD suggesting twice that.

If you use a sealed cabinet, you could use a micro-cabinet of around 3.5L and get down to about 100 Hz.  If you absolutely know you'll use a subwoofer that's a great way to go, especially with a desktop system.

Specifications:

• Sensitivity 91 dB / 1m
• Frequency : 65 - 20 kHz 
• Minimum impedance: Approximately 8 Ohms.

The sensitivity is unusually high because there is no crossover. We pretty much get the full sensitivity of the woofer. 

Shopping List

Here is a list of materials you'll need:

• FaitalPRO 4FE35 8 Ohm Version
• Denovo flat-pack 0.25 cubic feet / 7L cabinet
• 41mm port cut to 57mm / 2 1/4" long
• Speaker terminals
• Wire - about 3' to 4' of  stranded 16/14 or 12 gauge (thinner is easier to solder) wire
• M5 wood screws
• Acousta-Stuf 

I specify the Denovo knock-down flat-pack cabinets ($50/pr) because they are much cheaper than the furniture grade Dayton cherry cabinets ($190/pr) but either will work similarly. If you want something very nice looking and don't feel like doing the finish work yourself the Dayton cabinets are worth the extra.


Tools and Supplies:

• Router
• Hole cutting jig to cut approximately 3 9/16" hole for driver
• Drill and bits
• Wood glue
• Clamps
• Soldering iron and solder
• Wire cutter / wire stripper

If you use the port you'll get an f3 of around 65 Hz, 100 Hz otherwise. Remember not to put the port directly behind the woofer! Not only could it be a tight fit, but you want to minimize high frequencies from exiting. If you never plan to put a tweeter into this speaker, then you could certainly place the port in the front underneath the driver, making this speaker easier to place in tight situations.

I also recommend the use of the 3/4" multi-layer Sonic Barrier products on the internal side walls to reduce cabinet resonances. Build your LM-1S first, and if you think voices are sounding a little "boomy" then I highly suggest adding Sonic Barrier.

Fill the cabinet loosely with Acousta-Stuf before final assembly, making sure to keep the area at around the end of the port clear.

Placement

With no equalization circuit of any kind these speakers will be best with close surface reinforcement. A desktop, bookshelf or entertainment center will work great. Hiding them in a bookshelf would also make them ideal for hidden surround placement. 

If you are using them as part of a HT setup the room calibration circuits will compensate for either stand or shelf use. Just make sure to set them to "small" with a crossover of 80Hz or higher so you don't overload them.

FaitaPRO 5FE120 vs. Peerless 830991

Bass 

I ran the 5" FaitalPRO 5FE120 vs. the Peerless 5.25" 830991 through WinISD for the smallest Dayton cabinet, 0.25 ft^3 / 7L.

What I was really looking for was evidence of significantly better bass response, but truth is these two drivers are pretty equivalent. In the 7L cabinet, with a port the FaitalPRO has a slightly better f3: 53 Hz vs. 65 Hz, but the -10 dB Points are the same.

In ideal cabinets, the 830991 requires a 13L box, vs. 8L for the FaitalPR0, f3 nearly identical.

At least on paper, the FaitalPRO edges the Peerless just for needing a smaller cabinet to reach ideal responses. But the differences are truly small.

Treble

The really big differences between these two drivers are in the top end. The FaitalPRO is remarkably smooth for 2-3kHz more than the Peerless, making it easier to match with a broader range of tweeters. While the LM-1 required a 2kHz crossover, with this little gem we should be able to get up to 3-4kHz. Many less expensive tweeters are going to be very comfortable crossing over here.

The LM-2

I'm listening to the LM-1's on my desktop. They've made fine desktop and shelf surround speakers. But truth is they are shy in the bass. Using a new desktop amp, the bass boost feature helps.

So now I'm thinking about the LM-2. An improved version in the same box. While thinking about designing a 3-way I came across a promising new mid-woofer, the FaitalPRO 5FE120.

It is about the same cost, and efficiency but has some interesting improvements:

• About double the power handling
• Better fit in a 0.25 cubic foot cabinet - Deeper bass
• Even smoother response than the Peerless 830991
• Physically 1/4" smaller. 
• Much better high frequency extension

A good match for it may be the SB Acoustics SB Acoustics SB29RDCN-C000-4 N ring radiator tweeter. It is as smooth as the XT25BG in the LM-1, but more importantly, about 32 mm smaller in diameter faceplate.  It is unfortunately about $20 more expensive.

The LM-1 were designed to be on a desk or shelf, but the LM-2's with the increased power handling and bass I will make stand-alone.

Another, novel idea I may incorporate here is to reverse the position of the tweeter and woofer. I'll put the woofer at ear level and offset the tweeter.