SNR-1 : A Two Way High End DIY Monitor

Merry Christmas fellow music lovers. For Christmas, 2017 I give you all the complete designs for a high-end two way mid to large monitor. Alternatively, the cabinet can be done as a floor stander.

The design uses a Mundorf AMT in the tweeter and a ScanSpeak cut-paper 6.5" mid-woofer. I was inspired somewhat by the Klan Ton NADA but wanted to reduce the vertical dispersion to better fit my small apartment ceiling. I was also inspired by the recordings of Halie Loren, who despite having shoestring resources produced excellent recordings.

The concept and electronics are all mine, but the cabinetry is by Taylor Speakers.  My picture does not do the quality of the maple finish justice.

I would call this a full-range speaker, but it is not boomy at all. Ideally you'll want it about 1-2' from the rear wall for the best bass performance. The dispersion is also very wide, so space from the sidewalls is also going to be necessary for the transparency of the unit to come through. Some may find it a little too lean. I think of this as an ideal jazz/classica/movie speaker but not a rock'n'roll speaker at all.

Build cost is around $3k. $1k for the cabinetry, $1k for the drivers, and the crossover can vary a great deal depending on what you use for caps and coils.

I have been sitting on this design for a while, wondering if I should make it a commercial project or not. I have finally decided not to, the financials and work involved are just not worth it. So instead I'm sharing it with the world in the hops that others may enjoy the benefits of the design.

For simplicity and communication I have started a thread with the technical data you will need at DIYAudio. Feel free to comment and ask questions on the thread.

The Crossover

You should refer to the link above for the files, and to discuss building, but here is a picture of the schematic (as measured) and a picture of the prototype:

Fix / Upgrade or Refresh an Old Speaker or Subwoofer

Subwoofer Upgrade

The Dayton Audio SPA250DSP plate amplifier. This is essentially all of the guts of a subwoofer except for the actual driver.

Of course, you can use this amplifier in a new subwoofer, but for just under $200 it makes for a great solution to an old subwoofer!

The biggest hindrance to most mid-fi subs is not really the motors so much as the lack of good EQ capabilities, and good crossovers.

This little unit can take your old sub and do crazy good things with it. I highly recommend it!

Speaker Conversion

A possible mod is to convert full-range speakers to a speaker + subwoofer.

There are a number of manufacturers like Vandersteen, Thiel, etc. take the approach of using a built-in subwoofer amp in their full range speakers. The big advantage is a beefy bass amp and being able to carefully tailor the bass response of each speaker.

Typically you run your amps "full range" so there is no crossover in the critical mid-bass/mid/treble region. If you are spending big dough in your preamp and DAC that's probably how you want to go.

On the other hand, if you are more about high value, high performance, th SPA250DSP includes a line-level crossover, making it ideal for using low power amps for the mid/treble. 

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.

A better tweeter for the LM-1 ... Maybe

A fellow DIYAudio member pointed the NE25VTS tweeter to me.

Has a very useful range, from around 2kHz up through 20.

Advantages over XT25BG60 - The diameter is about half the size. This allows very tight mounting next to the tweeter.

Disadvantage: Frequency response. The XT25BG is unbelievably flat through 30 kHz. The NE25 is more ragged, rising response and not as extended.

If I was re-thinking the LM-1/LM-1C, this tweeter would be a top contender as a replacement,especially with the LM-1C as it would allow much closer positioning of all 3 drivers. If you are looking to design a two-way near-field monitor and must have very close center to center spacing AND a low crossover point then this may be an ideal compromise.

It is certainly not a drop in replacement for the XT25BG however. Using it would require you to measure it in place before attempting the correct crossover for it.

Focal Mezzo Utopia Be Upgrade Kits

Readers:

I'm considering offering a modern, luxury upgrade for the Focal Mezzo Utopias.  If you would like more information or want to give me some feedback before I launch the project, please visit me here:

Focal Mezzo Utopia Be Upgrade