Tuesday, December 29, 2015

Squires Natural Reference 1 - Compression and Distortion




Comparing the 95 db and 70 db signals.  What errors you can see are probably due to me being lazy and using the Logitech Squeezebox volume control.


Distortion elements

Please note that while the shape of the distortion in these charts is accurate the scale is NOT!   You cannot read the actual distortion values off these charts due to a limitation (or feature) in OmniMic.  The distortion figures on on a scale not shown.  What I will say here is that the actual distortion figures are ridiculously low all the way to 100 db. :)


Distortion at 70 db

Distortion at 80 db

Distortion at 85 db

Distortion at 90 db

Distortion at 95 db
Energy Storage, flat EQ

Wednesday, December 23, 2015

Squires Affordable Reference 1, SAR-1



DIY Speaker

The SAR-1 uses a Dayton Audio AMT3-4 ($160/pr) tweeter and  ScanSpeak 7", 4 Ohm Revelator 18W/4531-G00 woofer ($420/pr) with a target crossover of 2.8kHz.

The speaker to the right however is not the SAR-1 but the Squires Natural Reference 1 (SNR-1) a much more expensive variant on the theme which uses the Mundorf AMT25CM1.1-R ($960/pair). The cabinet design and execution is from Taylor Speakers.

Done right the SAR-1 should look fairly similar.  The Dayton AMT3-4 is almost the same height but about 6mm narrower.  Both tweeters suffer inadequate flange lips at the top and bottom though, so be prepared for a really fun time mounting.

I'm really pretty proud of the SNR-1 though I know it may still be too expensive for many hobbyists. For the SAR-1 the goal was to get as close as possible to the SNR-1 at under a thousand dollars, and at least on paper it looks possible.

Introduction

The total cost of the SNR-1 seemed too much for a DIY project for most so instead I have redesigned the crossover for the much less expensive Dayton tweeter while keeping the magnificent Revelator woofer. If you build your own cabinets the SAR-1 could be done for around $800 + lumber depending on the cost of your crossover parts.  Add another $850 for custom cabinets.

I hope at least some enjoy making a pair of SAR-1s, and I know many will enjoy criticizing it. I call it the "Affordable Reference" because compared to the Squires Natural Reference-1 (SNR-1) this is a much less expensive design due to the tweeter and crossover costs.  SNR-1 is still proprietary but I've used the SNR-1 frequency response and bass crossover as a reference line to design the SAR-1 from.  In terms of frequency response and phase angle matching SAR gets pretty close to the SNR-1 with some limitations, of course.

I should also thank SpeakerDoctor at DiyAudio for his help in pushing me along to use AMT's, particularly the Mundorf tweeters in my design. 


Sound

I can only attest to the sound of the SNR-1 which is in a word, fantastic. I do not know how close an $80 tweeter will get you to a $430 tweeter, but I can tell you the 7" ScanSpeak driver in this enclosure is simply amazing.    The Dayton data for the tweeter is also very good, but here is where we can separate the quality of the tweeters.  Let's discuss the two tweeters without crossovers.

Tweeters

As you can see, the Dayton tweeter has a constant rise from 2kHz, with a a peak at around 10kHz followed by a rapid rolloff after 12kHz of almost 20db/octave.  Sadly we're just not going to get the last half octave out of this tweeter.

Compare that with the Mundorf tweeter in yellow which is completely flat after 2kHz. Also the Mundorf tweeter is a 6 ohm unit while the Dayton is 3.  Just no getting around the frequency response and impedance challenges. Another potential issue is the power handling of the Dayton is a little limited, but then again, it's very efficient.  This is why you see 24watts of resistors padding it down.

Woofer

Remember kids, in-room bass is never ever smooth. Fortunately by placing the speakers assymetrically you can get lucky and get each speaker to fill in the weak points for the other.

Anyway, my point is, for a 2 way, in a medium San Francisco apartment, the SS 7" in the right cabinet has more than enough bass for anyone. If you want better bass than this, you don't need a bigger speaker, you need a bigger home.

The $320 Illuminator 7" driver will add $200 and is almost a drop-in replacement, but has higher distortion which you trade for higher output.  If you really have a larger living room, this is an option you should consider.  Note the cut-outs are NOT exactly the same though.  If you plan on experimenting play close attention to the driver spec's.


Cabinets

To the right you can see the SNR-1 again.

We use ScanSpeak's recommendations mostly, a 1 ft3 enclosure but with a 6" long, 2" port. This port change is based on the Klang Tong Nada kit design. It can easily be adapted to a sealed enclosure as well by using a 0.4 ft3, but as I learned from Lee Taylor that the larger volume is totally worth it. It's like having twins. You were only expecting one baby, but you got two. The volume is a bit of a surprise, but totally worth it. The volume and port also lend themselves to floor-standing versions.




Crossover

The crossovery is third order high low pass.

The simulation assumes 1.44" of woofer delay at 3'.  Without having the Dayton I can't tell how correct this is, but my gut tells me it will be within 0.25". Close enough to compensate for in the woofer, see below.

The Tweeter section has an unusually high number of inductors due to a notch filter and a treble boost formed by R6/L4/C2.  This adds a little compensation for the step roll-off after 12kHz.  It can be safely omitted.

 Capacitors

For the SNR-1 I used Clarity MR caps in the tweeter and Clarity ESA caps for the woofer. Clarity Caps have proven to be amazing. Better to my ears than Mundorf Supreme's and SIO's in that they lack a lot of character the Mundorf's seem to add. The one area where they seem to have character is in strings, which take on a nearly warm, soapy feeling, as if the bows had been lathered in wet soap. I am sorry, that's probably a terrible description.

Sadly, the tweeter caps will still be expensive, around $180 per speaker pair. If that's still too rich the lowest I'd go with your final caps are the Clarity ESAs, around $79 for tweeter caps.

You will be tempted to skimp here, thinking that the Dayton tweeters don't justify the cost.  Please don't.  If you can afford them at all, take the plunge.  The tweeters will show you the difference.  How do I know?  I'm in the camp that says that any decent tweeter will demonstrate the effects of caps changing.  I'm not alone either.  Troels Gravesen has written similarly.

Of course, you are welcome to use your own particular favorite caps, but these are the only one's I feel I have any experience with so I can't comment on substitutions.

However if you'd like my opinion on your favorite caps, please write your question on the back of a pair of Deuland 10uF VSF speaker capacitors and send them to......

Inductors

I really like the Jantzen air coil inductors.  Bargain priced, spot on specification.  If you want to get fancy for the woofer, go with either a Goetz foil or Mundorf either in 14 gauge should work and it's what I use.

Resistors

I use Mills resistors exclusively.  Nothing added, nothing gained, absolutely transparent, and as a bonus, often smaller than equivalents from others.  Also, not too expensive, but you'll pay $60 for a set so maybe the MResist from Mundorf will help you save a little more.

Cautions

Now, before you get TOO excited, this design is virtual and was designed with the help of OmniMic + DATS and XSim from Bill Waslo. The woofer measurements are based on my measurements in my cabinets in a room. The tweeter data however comes from Dayton. It's likely you'll need to adjust something before yours is completely dialed in. I strongly recommend the use of these tools.  XSim has been amazingly accurate, so if you trust that and you trust Dayton's data, this crossover should be pretty close.  You may have to experiment with the resistors in the woofer section to get perfect alignment.

I suspect that if the Dayton data is correct the most you'll have to do is dial in the correct tweeter to woofer distance and compensate for this in the woofer circuits.


Virtual Measurements

 OK, enough chit-chat! Down to the dirty stuff. In the first chart, the frequency response, I plot the SNR-1 with the Mundorf Tweeter above the SAR-1. Note the actual sensitivity is identical, I've offset for clarity.  Remember, the squigglies below 400Hz or so are in-room artifacts.




Next the individual driver response. 



Tweeter Inversion Test

To test the accuracy of the phase matching we invert one driver and look for a deep, symmetrical null.  Here you have it, textbook! At 1/24th octave smothing it almost 16 db.  Not the best, but not bad either. 



 

Impedance

And finally, the impedance plot.  After examining the lowest point, I decided to remove the impedance compensation network as it was vestigial. By not using it the low impedance point is now 3.2 Ohms at 1.4kHz with almost exactly 0 degrees.  A little low, but with such low phase angle hopefully most SS amps will deal well with this faux pas.





Saturday, December 12, 2015

Noes - XSin vs. Actual

A big thanks go out to Bill Waslow for his excellent and free XSim.  Together with OminMic and DATS I did in weeks what it would have taken me years if ever.

To make the long story short, here is a comparison between the simulated crossover, and XSim's expectation.  Blue is simulated.  Differences in phase are probably due to inexact placement of the microphone between early measurements and now. 

If we take that data, and overlay it on the simulation from LEAP


Saturday, December 5, 2015

I love XSim! 

Here is the test schematic


Sorry about the part numbers.  I can't reorder them.  On top is the 2nd order design, on the bottom is the first order. 

Here we have the impedance of each, seen from the amplifier's point of view:

The top, yellow curve is the 2nd order filter, the bottom green line is the first order. 

Next, let's take a look at the power dissipation in the series resistors in each. 


R1 and R6 are part of the first order , R3 and R5 part of the second order filter.  You can see in each case the power of the 2nd order filter lags (is lower) than the first order filter, except at the very end for the first resistors in the circuits.  

Here are the simulated frequency responses, but please bear in mind having a good response was not part of the experiment.   Tweaking the crossover becomes very arbitrary.  The goal of this experiment was just to examine how power and impedances changed based on 1st vs. 2nd order.  Also, the first resistor is not really needed, it's again there for the investigation.



 

Thursday, December 3, 2015

XSim - Simulated Noes Xrossover

A quick posting for the currently simulated crossover.  As soon as the real one is built we'll compare!  

And here is a weird pre-ringing issue with the tweeter.  minor, but weird.

 

Friday, November 27, 2015

Noes - Desesperation Crossover

What do you do when you have a long weekend, great new speaker drivers and your crossover parts are still a week away?  Improvise!

The Noes design calls for a 2.8kHz crossover point with a 3-5 db tweeter pad, among other things.  My plan was to tinker with the crossover during the long Thanksgiving weekend, and have them close to finished by Monday.  So I had two choices:

  • Do nothing and use the woofer full range
  • Find crossover settings that would work with the parts I had.
Desperate, I chose the latter.  I ended up with a crossover point at around 6.8kHz with the tweeter about 5 db lower than desired.  Why?  I only had 10 ohm power resistors left in my arsenal, and this was the lowest I could cross the woofer over with the parts I had.

How does it sound and look?  Surprisingly good!

Thanks to Omnimic I was able to quickly tell I had to reverse the tweeter.  Not my favorite situation, but desperate times call for desperate measures!

I've had the opportunity to listen to some fabulous recordings via our local classical internet station, KDFC.  The Mundorf AMT's are spectacular, I can't wait to finish the real crossovers.

 The crossover breadboards.  The top section is the tweeter, bottom is the woofer. 

Tuesday, November 24, 2015

Noes - First Mesurements

I still don't have crossover parts, but that's no reason why I can't do some interesting measurements.

Fee Air ScanSpeak Impedance

 Fresh out of the box in free air the speaker resonance is around 49 Hz at around 31 Ohms.  I believe I read somewhere that ScanSpeak specifies the Fs after break in, so I should probably measure this again in a week or so.

To begin with, a full-range frequency response chart for the woofer.  Incredibly clean at the upper end of the spectrum, even when averaged at 1/24th octaves.  This is with the speaker on a chair and microphone 3ft away on the woofer axis.

Next up is the impedance measurement in the cabinet.  The woofers have only been playing for about 4 days with low to medium jaz 24 hours a day.  I'm going to have to go back to Lee to ask for help interpreting both of these.  From the first chart I worry the box is a little large.  Below is the chart I really don't know well, the speaker + cabinet impedance. 

I can see the port resonance at 24 Hz, and a second resonance at 69 Hz.  The valley's nadir is around 35 Hz, somewhat lower than the driver's Fs when first purchased.  ScanSpeak specifies the Fs at 33 Hz after break in, in which case the tuning would be spot on.

I have a week before I can assemble the crossover, so I have time to plan ahead.  With Thanksgiving coming up parts will be slow in arriving.

Of course, there will be more later.

Saturday, November 21, 2015

My First Speakers

Well, at least the first speakers I have designed from the ground up, and I use the term "design" loosely.  Component selection was mine, cabinets are from Lee Taylor of Taylor Speakers, partial crossover design was from Madisound.  I say partial because they designed a crossover for a different tweeter than you see here.

The cabinet is much better looking than this, especially the veneer.  I'm afraid my phone doesn't do the quality of Lee's work justice, so please bear that in mind.  His web site has pictures much closer to reality.

In a sense, this is a fail.  I was trying to design some smaller satellites with these components, and Lee was trying to guide me to a floor stander.  These speakers are really very tall and deep so I'm not sure most satellite stands would work for them.  It's a bit like trying to have a baby and getting twins though, I am not at all unhappy!  I just got more than I was expecting.

Drivers

The original design called for a smaller Mundorf AMT tweeter but that was out of stock and weeks away from arriving in the U.S. so i went for it's bigger brother the Mundorf AMT 25CM1.1-R.  One weird thing about this driver is that it takes banana plugs, not spades or bare wires.

Thd mid-woofer remains the same though, the ScanSpeak Revelator 18W/4531-G00 7" driver.  The 4 Ohm version is more sensitive so mean less damping is needed in the tweeter section.   I chose the Revelator in part out of cost ($220 vs. $320 ea.) concerns but part was also that in the high end of the driver I liked the response better than it's Illuminator counterpart, then when I read that Zaph rated the Revelator better than the Illuminator in terms of distortion that cinched it for this design.  I admit the basket does not look as cool though.  

Despite the larger tweeter having a lower useful crossover point I'm keeping the crossover frequency the same for a number of reasons.
  1. I don't want to redesign the crossover from scratch
  2. Higher crossover frequency = higher power handling
 One big advantage here as well is controlling the vertical dispersion.  The taller the tweeter, the less floor and ceiling reflections and clearer the sound at the listening position.  Like ribbons and electrostatic speakers, we should get enhanced clarity and detail than with conventional round drivers. 

 

Test Wiring

Per Lee's suggestion I'm going to keep the crossover external until I have tweaked it perfectly.  For this to work of course I'll use a separate pair of banana jacks for each driver.  Internally I'm using plain old 14 gauge zip cord which happens to be made by Monster.  I had it lying around from the surround sound installations in previous apartments.  It's thick, flexible, finely stranded and best of all, free and taking up space under my bed in the wiring box.

The white cable with the bananas of course goes to the tweeter, the pinkish cable to the SS woofer.  This being a test harness I didn't want to spend too much effort, but after installation and looking at the kinks in the wires I decided that the heat shrink was going to be necessary for proper strain relief.

The Sound! 

Of course, anyone with a checkbook and drill can get speakers this good looking, but how do they sound?  Magnificently quiet.  You've never heard speakers that disappear like these..... My secret?  They don't work yet! :(  Crossover parts were delayed due to a series of errors on my part but I should be able to start putting that part together soon.  Of course, being unable to resist, I am currently breaking them in by running the woofer's full-range.  They sound surprisingly good by themselves!  I had to go back to the charts and look but they have useful output to 10 kHz so I can run these as my main speakers without going completely nuts due to the lack of treble.

Sunday, November 15, 2015

Focal Profile 918 - Final Charts

I'll be posting more info on this in the DIYaudio forums, but for now here are the pics.

The chart below shows the final measurements, taken from my seating position with 1/24 octave smoothing and a 2mSecond window.  The RED trace is with the grill (as recommended) and the BLUE trace is with the grill removed:


The image below is from the Sound and Vision review with the grill on.  Note in particular the 10K peak and ragedness around 5kHz which are gone, those are probably thanks to the liberal use of felt on the grill and tweeter housing:


And lastly the grill removed, which is the image most make fun of:
Not only is the grill less important, but the tweeter balance is different.  Instead of trying to push the tweeter up at the last octave, I've gone for a smoother response from 2-10k, that goes generally downward.  Crazy?  Well, by accident it actually measured much closer to the Focal Utopia's of 2004.  Check out this chart from Stereophile:

Of course, I'll never get the output, especially in the bass, of the Utopia, but it does sound much smoother and coherent than it did before.  Should you buy a Profile 918 and hack the crossover like I did to get a poor man's Utopai?  No way.  The value just isn't there overall.  The value IS there if you want to take this on as a learning experience though. 

Sunday, October 25, 2015

Focal Profile 918 and Dayton DATS V2

I've been using DATS to test a few drivers and inductors I have lying around.  I also tried measuring the Focal Profile 918s and made a startling discovery.  The minimum impedance is around 2.3 Ohms!  Also, the impedance between 75 and 250Hz remains below 3 Ohms.

No wonder these speakers can tell the difference between a mediocre and stout amplifier.  They are just ridiculously difficult to drive for their class.

This low impedance is probably a direct result of the crossover topology, 2.5 way means that the mid/woofer and woofer are both working in the bass.  Since both are about 6 Ohm devices this would imply a minimum impedance of half this.  Ouch. 

Please note the maximum and rising impedance in the treble are probably my fault.  I've made some EQ changes to the treble which means this is probably not what a stock speaker would measure like above 1 kHz.

Sunday, October 18, 2015

First Impressions of the Mundorf AMT25CM1.1-R


I was so excited to get one of these in the mail I wanted to start blogging right away.  I'll cover the response and harmonic distortion measurements in a future posting. 

  Electrical

Based on my handy dandy DATS V2:

 Fs = 1666
Re=6.105
Le=9.47 uH

As expected with such low inductance, the phase plot is practically flat.  Highest measured impedance was around 6.4 ohms at resonance.  Compared to dynamic drivers, this is a remarkably simple and resistive load.

Mechanics

The mechanical drawing, while accurate, doesn't really do the size of the body justice.  The body is really big about the size of some laptop chargers and the flange top/bottom are small and difficult to cut for. 

The front of the tweeter.  Sorry about the rotation.  Note blemishes are due to the plastic shipping film still being on. Kind of a boring shot.

Here is a side view of the tweeter where we can see just how monstruous the body really is.  Mundorf provides a rubberized pad on the flange. 

Here are a couple of interesting things.  Unlike my expectations, Mundorf provides full sized banana jacks and a pair of banana spring clips to attach speaker wire to. I  was expecting spade lugs or quick disconnects.  The left edge is the bottom of the tweeter. Notice the big difference in the width of the flange on the sides (top) vs. the top and bottom (left).  As Lee Taylor of Taylor Speakers pointed out, this can be a real bothersome situation for a cabinet maker.  I suspect the choice was to make this tweeter more palatable for line-array speakers.   In fact I'm kind of tempted to start working on one next.

Also, the corner radius are very small and non-standard 4mm.  Just to be nice, I'll throw in the dimensions below.  As you can see there, there is a 5mm spacing on the top and bottom flanges.  That's not a mistake.  One last comment, the housing is rater flimsy.  It feels like a thin version of the poly carbonate material in the uber-expensive suitcases being sold today and there is no visible way to remove it.  Speaker makers using this would probably want to encase the driver in it's own, well damped, sub cabinet.

The Drivers Arrive

For me this is a bit like Christmas and my Birthday present.  Madisound was kind enough to drop ship one set of tweeter and woofers over to Lee Taylor over at Taylor Speakers. While he is busy with the speaker cabinets I can at least play with them and do some basic tests.  That's all fine and dandy, but something else happened I did not expect.  You can see the problem here. 

I did not realize that the speakers were packed in pairs.  Madisound did a fine job of packing and shiping, but if I had known this was the consequence I might have bought all the drivers at once.  Here's the same view of the tweeter box.