Saturday, October 14, 2023

Hypex Filter Designer

 I want to make this quick.  After 2 days wrestling with the Hypex Filter Designer, the tool you must use for Hypex DSP products, I can confidently call it unfriendly. 

I am using a Hypex FA 123, 3 channel DSP + Class D amplifiers on a single plate.  Thank goodness their tech support is so friendly and responsive. When I first got it the firmware was misset and the interface kept imagining it was the 2-channel version, the FA 122.  This left me unable to use the 3rd channel which was intended for the tweeter.  

To make a long story short, after getting the firmware patched up (thanks Jeffrey!) I then had a long slog through the channel configurations and filter settings.  The biggest hassle with the HFD is that nothing is instant.  Experiments take about 10x longer to make than they would with say miniDSP.  You must hit upload, wait 20 seconds, and then fix the bug where it resets all of the mute settings.  

This makes it very hard to ease up into the right filter settings.  Once you even get close you want to stop and leave it alone. 

It is seriously about 10-30x more work to set up a filter here than in miniDSP or Roon by comparison. Otherwise, great hardware, guys!

Friday, October 13, 2023

The Center at Scale

 I have the center on my rack ready to start configuration. 


Despite the size (smaller than many!) this is a deliberately limited-low frequency center.   It was designed to cut off ~ 55 Hz and pretty much does.  With the processor's 80 Hz high pass filter the center cannot produce much bass. 

Lets show how this all integrates.  These are measurements from the listening location, so they SHOULD be dirty.  The red line in the background is the center channel, the blue line is my right speaker.  You can see how well the center is matching my main speakers.  This explains the really great integration.

One thing to note is that DSP processing takes time, so the speaker looks like it is about 10" further back than it really is. The Dayton Audio OmniMic DVD is a great help here.  The short sine sweeps run simultaneously from the left and center speakers make sure you get exactly the right delays. 

Please ignore the poor bass in the chart, I had not yet fixed up the subwoofer phase alignment. 

Tuesday, October 10, 2023

The Center Assembly

 

Happy to announced that the center channel has been put together!! The four drivers and plate amp have been wired in and assembled into the cabinet.  Drilling was made a lot easier by pre-existing pilot holes from the cabinet maker which was a super nice touch.  Also they went to the trouble of insetting the plate amp giving the rear a very clean and professional look.

Sadly, this speaker still can't make any sound.  Over the next week I'll use the Hypex software to enable each channel in turn and begin the process of building up the Virtual Point Source crossover. 

I don't know why but those who haven't done this part think it's easy or requires no finesse and careful adjustment.  Nothing is further from the truth.  What is easy is we no longer have to fiddle around with individual crossover parts.  No more resistor, capacitor swapping and tinkering here! 

The worst case scenario  I've seen is builders who take the published specifications at face value, throw in some guessed at curves, and then use global EQ to "fix" the speaker. To be clear, you can't achieve anything good that way. Perhaps with horn speakers that are designed for simple crossovers which have long been understood by the users this can yield good results but to achieve the virtual point source effect we are going for here each driver must be individually measured for frequency, phase and delay so the electronic curves are complementary to each driver and work with the driver physics, not against them.  One key ingredient to this is an excellent midrange that can play beyond it's crossover points.

Wednesday, October 4, 2023

Time for New Surge Suppression

What a difference 20 years makes

If you first started buying surge protectors in the 20th century there are two big things which are different today than then which you need to know about.  The differences is so large that I am replacing out several of my old units.  It may be time for you to do the same. 

Here they are in summary:
  • Whole house units are required as of the National Electric Code (NEC) 2020 and they can save your life and home.  Details below.
  • Several surge protection brands have come around to focusing on low let through voltages instead of joules. This approach is something ZeroSurge has been on the leading edge of for decades in the semi-pro/pro space. 

All of the surge protectors I am recommending have let through voltages of less than 200.  Getting low let through voltages used to be something only exotic brands like ZeroSurge had but now it's widely available in more affordable units. 

The let through voltage of a surge protector is how high a voltage would have to occur before the protection circuits even notice it is happening.  Circuits which limit the let through voltages are key for several reasons: 

  • They work to slow down the surge, reducing the current that flows through your strip and therefore the home wiring. 
  • They improves the reliability of the surge protector.  The same surge won't dissipate as many joules, so you can think of this as a joule magnifier.
  • They start working at a much lower voltage protecting your equipment  
  • They add some noise filtering since they are essentially low pass filters.

 

Joules Don't Matter

Many surge protectors are sold on the amount of joules they will "abosrb."  This is actually kind of a false reading.  This is the amount of joules the MOV's will take before they are destroyed and ineffective.  If you imagine living in a home with constant lightning strikes every month then a strip with more joules will last longer than a strip with less joules, but it is not actually a more effective strip. These cheap surge protectors are still going to be slow to respond and may very high voltages and current flow through your wall wiring. 

Cheap Strips Can Cause a Fire

Cheap strips with high let through voltages can cause a fire through one of two ways:
  • They will blow up with flames shooting out of them (really)
  • They will cause so much current to flow through your home wiring that it can melt the wiring in the wall and start a fire in there. 
For the sake of your life and property therefore I recommend that you use a whole house surge suppressor along with surge suppressors with low let through voltages and those are the only ones I am recommending here. 

Recommendations

Best for General Use

 
This is what I use everywhere except the audio/home theater or where I have a UPS. 

Best for Audio and Home Theater

Furman makes dozens of models of power strips and surge suppressors but the feature mix that are must haves are LiFT and SMP.  LiFT will reduce noise on the line and SMP is a hybrid series mode surge suppression.   In addition they have models for everything with features like remote triggers, voltage regulation, balanced outputs, coaxial surge suppression, separate filter banks, the list goes on!

 
Furman seems to have discontinued the more affordable LiFT/SMP strips so I can no longer recommend them for general use.  If you don't need any of the advanced features beyond surge and noise suppression you should get a Tripp Lite Isobar Ultra instead for the price. 

At the high end of the Furman product line the mix of features and reliability is absolutely excellent.

 
 

Networking

Besides the power lines the other way in which a lightning surge can infiltrate your home is via a cable modem.  I use a gas discharge tube on the outside at the grounding block and use an "air gap" kind of solution inside.  Between the cable provider's equipment and my own I use a 1m fiber optic cable to prevent lightning from traveling through the Ethernet cable to my PC's, TV's and audio streamers. Here's the list of equipment I use:

 
There are Ethernet surge protectors but after doing some reading and looking at the reviews I decided to take it out. They aren't that reliable and introducing a potential path to ground from the Ethernet cable can actually cause a surge current to happen when otherwise there would not have been one. 


Whole House

A whole house surge suppressor can save your life and your equipment. Get an appropriate one for your panel.  I prefer to use the kind that take two breaker slots rather than the kind that are placed in a separate enclosure. They are easier to install and are closer to the bus bars. I have used all but the Homeline here in the list below and while a homeowner can usually install this themselves (not in a rental)
 

As a homeowner I would only live in a home with Siemens or SquareD panels.  If you have any other brand I suggest you check out this website from an electrical engineer who specializes in electrical fire forensics.

 Having said that the Leviton brand of whole house surge suppressors are not bad either. 

 Details

 I first installed a whole house suppressor near Boston in around 2000.  The goal was to protect the air conditioners and woodworking equipment I had.  At the time these were considered accessories but 20 years later the National Electric Code has made these mandatory in new or upgraded installations.  I was curious as to why and thankfully I found the great State of Minnesota posted an explainer:

 I quot them thus: 

During the 2020 NEC code cycle it was substantiated that surge protective devices are necessary to protect against home fires and personal injury. For the typical home, surge protective devices also provide protection for all the sensitive electronic systems, a variety of different equipment, appliances, lifesaving apparatus such as smoke alarms and carbon-monoxide detectors, overcurrent devices such as GFCIs, AFCIs, and much more.

 

The important most important point here is is the fire protection.  A big enough surge coming from the power company can induce enough current in the wiring in the wall to cause a fire which could possibly smoulder in the walls before engulfing your home in the middle of the night.  Also, being at the meter or in the panel these surge protectors can channel a ton of current to ground safely, much better this current happen here than at your PC or TV.  That surge current would travel through much thinner and longer wires.

The secondary considerations here are that we have a number of important and delicate systems in our homes which are now directly wired in, like fire alarms, smart thermostats, remote lights, etc. in addition to major appliances.  Major appliances can take a hit here and there but will eventually wear down after repeated smaller strikes. 

Do not substitute a whole house protector for a surge strip.  Use both.  Here is why: 

  • The best whole house surge protectors clamp around 500 to 600 volts.  The surge strips I am recommending clam around 140 to 190 volts. 
  • While the whole house protector wont' clamp until 500-600 volts it WILL take on very high currents safer than the surge strips you plug in at the wall. 
By taking this dual approach you can both reduce the surge current that could flow AND reduce the voltage your precious gear will be subjected to.