June 25, 2012

Simply Electronics

You need to be careful when buying online!

Have you made the mistake of getting too comfortable with buying online? Do you find that you take a punt, and don't always check who you are buying from that they have a good reputation?

We all get lazy sometimes.

Well, I bought an item from Simply Electronics. I should have been more careful. The item was offered for $200 with free shipping, it's about $225 elsewhere. Long story short, after 18 days they had not sent my item and they were not replying to my emails. I initiated a Paypal dispute and pointed out that I would make some noise about this. They sent the refund the same day.

In the process of investigating, I found countless stories similar to mine. I'm not entirely sure if they are very poorly run or a complete scam. Either way, save yourself a lot of hassle and don't buy from them. If you manage to save $20 and you actually get your item you will feel that you have earnt it many times over.

This is a good time to remember - before buying online, check out the seller first!

Paypal is good!

Use Paypal rather than giving them your credit card details. Paypal comply with security standards that many online stores don't. Paypal provides good back up - they might not be perfect, but it's better than counting on the seller's integrity alone.

Check first!

There are websites dedicated to reporting scams and companies that don't deliver. 5 minutes can turn up a great deal.

June 22, 2012

Coming soon: Cinema series

There are few speaker options in the market that cater well to a serious home cinema system intended to reach reference levels cleanly with controlled directivity and good sound in every seat. I'm putting together my cinema series to provide some options.



There are 5 main models shown here and they all feature high sensitivity and controlled dispersion. HT1 is a slim design that is similar in size to a typical floorstander. The extension is right where it needs to be to cross easily to a sub and the waveguide allows better integration than a typical dome tweeter. HT2 is similar but has greater output and efficiency. HT3 has very high output and enough sensitivity to avoid the need for any more power than you can get out of  an entry level AV receiver. Being relatively slim, it has a chance to live in a normal living room. HT4 is more likely to find a home in a dedicated room. It features a higher end midwoofer with greater power handling. The sensitivity is a little lower than HT3, unless you opt for the dual driver version. HT3 is a more value oriented option that can reduce the need for a power amp, HT4 would suit those with a good power amp with some grunt. HT5 goes one step further but the size means you may want to think about how to integrate it into your room.

HT1 - HT3 are designed for non-dedicated rooms, HT4 and HT5 are intended for dedicated rooms.

To match the mains I'm offering 3 surround speaker options:
These are intended to be installed into a plasterboard wall. SR1 can be made flush with the wall so that the baffle overhangs the cut out. SR2 protrudes a little further but is still almost flush. SR3 is intended for higher output systems and the box is a little deeper. If installed into the wall cavity, the profile is still quite modest, but it has a level of dynamics and output similar to an actual commercial cinema speaker. Surround speakers are typically very compromised to fit into a small box. These are designed to reach reference levels cleanly. They are also intended to be finished in such a way that they appear as acoustic treatment panels, where they can be blended in to the treatment scheme in a dedicated room.

I'm currently putting together a demo system.

These will be available on a made to order basis, with various custom options available.






June 21, 2012

Let's talk about inductors

I have a lot of crossovers coming together at the moment. My coil winder:

Why wind  your own? Basically, a good inductor for woofers especially has a lot of copper. In a sensible passive crossover design, the inductors are expected to be the most expensive part. Winding your own cuts down on cost if you have a good source of copper. It's also useful if you need a value that is not available.

Inductors, capacitors and resistors


All conductors have an inductance, but in inductor is a component that stores energy in its magnetic field where a capacitor stores energy in its electric field. A resistor doesn't store energy, but converts it into heat.



Resistors tend to have a small amount of inductance - wire wound high value resistors are a lesser choice. Mox resistors are used in crossovers for their lower inductance. Resistors are the least problemmatic parts in a crossover and they are also the cheapest parts.



Capacitors are more expensive again, but their faults are also relatively benign. Electro caps should of course not be used for serious long term use and they are known to lose their value over time.

Inductors are more problemmatic in a crossover. The most desirable is air cored. Cheap inductors use a ferrite core to increase inductance whilst keeping resistance down.

Unfortunately a ferrite core introduces distortion and is not a good choice for audio.

A good inductor for a crossover looks like this:

A good large value inductor might use AWG 14 copper to achieve reasonably low DC resistance.

How an inductor works


An inductor is essentially an electromagnet and it tends to resist any change to the current flowing through it. In other words, it has inertia as if it does not like the way that a music signal changes rapidly!

Inductance is based on four things:
  • The number of turns (more turns = higher value)
  • Core material
  • Cross-sectional area of the coil (more area = higher value)
  • Coil length 

Power rating

Due to resistive losses, all inductors have a power rating. Ferrite cores tend to saturate as power goes up, which means that the core can't support any more magnetism. Performance is seriously degraded.

Inductors can also exhibit microphonic effects where mechanical vibration causes the inductance to change.
 

Speaker measurement jig

Speaker measurement jig:


The Sound Easy guide suggests probes with resistors added, but they are built in here for robustness and convenience. Caps are for tweeter measurements.


June 19, 2012

RSA HE2 in progress

This is a 2 way passive speaker that I'm developing, featuring a high sensitivity pro 10" midwoofer and a waveguide loaded compression driver. Due to the high sensitivity, it will work well for valve amps and also home theatre use. It features 94 dB sensitivity with an 8 ohm load and 50 Hz bass extension. A careful balance of bass extension, box size and sensitivity has been chosen. Higher sensitivity requires more or bigger mid drivers, or giving up bass extension which makes a subwoofer necessary. The box is ply and will have a clear finish.

Ply cut the old fashioned way:


 Pieces on the left are for a shelf port. Very generously sized with flaring on both ends (not yet shown). A front port was chosen for flexibility, avoiding the need for feet with downfiring, or making offset from the rear wall critical.
10" waveguide with 10" midwoofer:


 Bracing:


A groove has been cut where butt joins have been used. This groove is painted black to give a nice fine line. 


After paint applied to grooves:


It looks like this:


Box damping with a mix of screenings as an aggregate with bitumin rubber. It's quite expensive, but very effective and also provides the benefit of sealing up the box. In the actual box I've used a fine aggregate with 7mm screenings and it looks very much like a bitumin road. However, it has some flexibility which is desired since the intended result is not simply a heavier box but one that is dead and well damped.
 










Priming of the box interior prior to applying bitumin rubber damping:

Upside down with vent shown on top:

Baffle not yet attached. Damping applied. I have since applied more along with the screenings, but around four applications are required.

Baffle held in place:

S3 flat pack ply


Samples of ply for the S3 flat pack:

These are not the best photos, but you can get an idea that this is good ply - premium Russian birch. Shown here is 30mm, with some budget 18mm ply on top. Both sides of the premium ply are suitable for finishing, although one is slightly better than the other.


June 18, 2012

Does home theatre require different speakers?

How well has the audio industry responded to the demand for home theatre? Not very well at all! The solutions offered would seem like a knee jerk reaction to the need for multi-channel audio. We've added centre speakers and small surrounds that can be mounted on walls, but there is little consideration given to what is required to create the genuine experience. Virtually none of the speakers marketed for the purpose have the capability to meet THX standards for home cinema adequately. New designs are needed that reflect the opportunities afforded by having a dedicated room, along with re-thinking the science of reproduction as it applies here. Current products here reflect two channel thinking.

Stereo listening

In a serious stereo system the focus is on music reproduction and that involves both good design and personal preference. The speakers are more likely to be placed into the room and usually there won't be a dedicated room. Room treatment most often won't be included. Only one seat needs to be optimised, so a small single-seat sweet spot is fine. In that seat the imaging needs to work and the sound balanced. The bass requires optimisation only in that spot. Personal preference plays a greater role in the choice of speakers. One might prefer the delicate top end of ribbons or exotic tweeters. The deep sound stage of dipoles. The slam of horns. Or perhaps a slightly warm sound coming from the right mix of speakers and electronics. The imaging of single fullrangers. The range of valid choices for stereo listening is vast, but home cinema suggests different challenges, specific requirements and a much smaller range of options that are well designed for the purpose.

What we need for home cinema


When setting up a dedicated home cinema room, the requirements are quite different. We want to achieve:

  • Much greater clean dynamic output - 105 dB in each seat, with 115 dB in the bass
  • Balanced sound in every seat with minimal seat to seat variation in response
  • Good imaging in every seat, rather than just in one central sweet spot
  • A room that has less reverberation
  • A good view of the screen
  • An enveloping sound stage that extends beyond the walls, coming from any place in the room as well as outside it
In order to achieve this we need:
  • Speakers with high efficiency, high power handling and controlled directivity
  • Multiple subwoofers optimised in placement and response with EQ
  • Acoustic treatment for the bass so that the much greater amount of bass will remain under control, rather than sound boomy and bloated
  • Surrounds installed for maximum envelopment (not floorstanders on the floor!)
  • Centre speaker oriented correctly and installed appropriately
  • Calibration with measurement tools and all EQ and high and low pass filtering correctly setup and tested
  • Acoustic treatment to an appropriate level of reverberation
In other words, the requirements of home cinema converge on a very limited range of solutions in terms of speakers. The ideal speakers for home cinema are those with constant directivity, with compression drivers and waveguides. A point source horn is the ideal choice for front main speakers, or a speaker based on a waveguide loaded compression driver matched to a high sensitivity mid. Coaxial speakers have a desirable point source characteristic, but care is required in their selection as some of them have a nasty harsh sound and poor sounding coax drivers are abundant.

June 4, 2012

Currently developing: RSA HE series

Currently developing a series of high efficiency speakers aimed primarily at valve enthusiasts.

HE1 - 8" full range driver + super tweeter
HE2 - 10" midwoofer + waveguide + compression driver
HE3 - 3 way design - 2 x 10" woofer + 6" mid + waveguide + dome tweeter

Designed with a careful balance of sensitivity, bass extension and box size.

Prices expected to be around $995, $1495 and $2495 respectively.

HE1
An entry level floorstander with the most critical range covered by one driver. A super tweeter coming in at high frequencies adds the sparkle that a full range driver tends to lack.

HE2
A two way floorstander that achieves just enough bass extension to avoid the need for bass augmentation whilst maintaining high sensitivity. The waveguide controls dispersion and yields a very wide sweet spot. This is a speaker designed with simplicity in mind, intended to behave well in a non-treated room.

HE3
A three way floorstander with wider dispersion and higher sensitivity than HE2.

This series features plywood enclosures which is rare in this price range. Plywood is lighter and stronger than MDF and has the right character and charm to match valve amplifiers. In this price range most speakers don't even include veneers. Those that do are limited to square edges which not only make a speaker look cheaper, but they are also sonically undesirable due to edge diffraction effects.

These will be made to order with custom options available including:
  • various stains 
  • satin or gloss clear finish
  • crossover part upgrades 
  • active versions available (crossover filter information provided, amps & crossovers not included)
  • rubberised bitumin internal box damping
  • driver upgrades
  • bi/tri wire crossover and terminals
  • higher grade ply
  • waveguide foam upgrade
All speakers in the HE series are floorstanders. Stand mount versions cost only a fraction less to produce and whilst shipping is reduced, the cost of buying stands is a disadvantage. Small HE speakers have no bass, and small speakers with bass have no efficiency!

Home theatre and high output music use

HE1 is not suited to demanding high output use. HE2 is ideal for home theatre use. We can offer a home theatre version with dual woofers in a sealed box. It has enough extension to mate with a subwoofer and has double the power handling along with 3 dB greater sensitivity. HE3 is designed for two channel systems but will also suit home theatre.

June 3, 2012

What happened to the Loudspeaker kit? LSK

You may have heard rumours about LSK (The Loudspeaker Kit) closing down. Some had posted online about not receiving their kits. I now have an update. LSK is back!

The third generation of LSK is here - I'm bringing it back, better than ever.

You will soon see an LSK forum back online.



June 1, 2012

Point source horn flat pack kit

Note: This kit has evolved into a new design: PSE-144. 




I will be offering a kit in Australia for a limited time. This is a one-off run. You will need to jump on board right now, because this is not a commercial ongoing venture. Instead I will make this available to a small group, with a view to making this accessible to non DIY types and sharing CNC costs around a group.

If you are interested, shoot me a message on my contact form, and I will keep you in the loop.

Some preliminary details ...


Kit will include:

1. CNC cut flat pack panels – over 40 pieces of birch ply and MDF. 
2. Compression driver (optional). 
3. Dedicated mids 4” closed back
4A. Passive version – assembled passive crossover
4B. Active version – including filter details for the crossover  

Prelim specs

  • Size: approx 900mm wide x 660mm high x 500mm deep
  • Sensitivity: 103 db 1w1m (passive), 107 db 1w1m (mids), 109 db 1W1m (tweeter)
  • Impedance: 8 ohms min
  • -3db @ 250 Hz (estimated, but could be 220 – 300 Hz)
  • Beamwidth: 80 degrees horizontal, maintained down to 350 Hz, pattern widens below
  • 60 degrees vertical, maintained down to 640 Hz, pattern widens below

Options

I will be suggesting the addition of foam to the horn to reduce coloration. Considering offering it cut as an option, if I'm able to construct a suitable cutting device soon enough.

What's so good about point source horns, in subjective terms

This point source horn is everything good about horns - dynamics and slam, good match with flea powered amps, unlimited output. It solves all the problems with horns - their need for a large room, their problems with imaging and the tendency of some to artificially distort the acoustic image. It also avoids the harshness and coloration that is a problem with many designs, often leading to the use of certain valve amps to try to tame them.

There is some similarity to the sound of Martin Logan stats, but without the amplifier difficulties and with much higher output.

The imaging and wide sweet spot is similar to waveguide speakers like the Econowave, but there is greater resolution of midrange detail, greater clarity and the clean output goes to another level.

It creates a large sweet spot like omnis and open baffle speakers, but the image is sharper and more pin-point in nature. This means vocals in movies don't appear artificially stretched.

They can work in a small room and can actually work quite well placed close to boundaries, where other speakers become muddied. They also work better in untreated rooms due to their controlled directivity.

They aren't for everyone - if you like small speakers, horns aren't for you! If you only listen to casual, low level, mellow music like acoustic guitars, easy listening jazz and the like, you won't appreciate everything a point source horn can do. You may find you prefer a nicely crafted Sonus Faber in that case. Or if you have a taste for a very airy top end, if you've fallen in love with the delicate shimmer of cymbals on ribbons or other exotic tweeters like Plasma or AMTs, then you may find point source horns or any speaker with compression drivers don't deliver that experience. However, my experience has been that the point source horns play nice with a very broad range of music. They don't draw as much attention to their air and shimmer, but overall I find them more natural.