what new in electronics

This one is for Earle Weston of Weston Acoustics ...

Ever noticed how much mediocre music lives on the radio, regardless of the channel? Well, in the interests of promoting musis that is actually worth hearing, that you might not hear on the radio, let me introduce some local talent. Stewart Kohinga is Melbourne singer and songwriter who recently performed live as part of the Live at Baker street series.


I would describe his music in poetic terms, but you can hear it for yourself on youtube >

Stewart Kohinga online:

Facebook page
Website

Live at Baker Street series >

This is a rare treat. A studio in Melbourne this Saturday are offering a live music experience where you then get to hear the recording on a $150k system.

Read more on StereoNET >









There is also a session on Thursday 30th.

• clear finish
• directivity measurements
• passive crossover

Once complete, it will be available for demos with a Weston Valve amp, with various upgrade options. I'm currently considering the choice of finishes, where I may build future versions out of MDF with a choice of veneer.

We've all seen the equal loudness contour:

It tells us quite a few things, many of them missed in casual observation. The first thing we might notice, is that our hearing is most sensitive to midrange from about 200 Hz - 14 kHz. Bass is subjectively "turned down" indicating that it's actually not very important in the functional sense. Bass doesn't tend to occur in nature in isolation of much higher frequency content. We also note that our ears are especially sensitive around 3.5 kHz.

This was made clear to me when as a teenager, I measured my first system. I found a huge peak around 3.5k and playing test tones and measuring with an SPL meter outside the science lab in high school, those 107 dB peaks were just plain nasty! No doubt that was a big part of what made little 15W speakers sound loud to my teenage ears.

This 3.5k peak in sensitivity does have implications. Many midrange drivers have cone breakup around this region, and many crossovers are not far removed from this point. A very large part of our internal hearing mechanism is dedicated to 1 - 7 kHz primarily, this region is critical.

SPL and tonal balance

Notice how things change with level. At a typical quiet background noise level of about 26 dB, we need over 90 dB at 20 Hz before we perceive the bass as simply matching in loudness. Many subwoofers fail to even register as a quiet background noise level! Now if we listen at a moderate level of 60 dB, we need 110 dB @ 20 Hz or about 94 dB @ 40 Hz. We probably need about 25 - 30 dB increase in bass level to get it to sound about the same in level across the bass spectrum.

If we boost the level to 80 dB, we need about 20 dB increase in bass level. The bass is starting to sound a bit more solid. If we increase the level to 100 dB, we are now in the very loud range, and the bass only needs about 12 dB boost to match the level.

So why don't we all boost our bass by these crazy amounts? These effects are partially allowed for in the recording process, so you don't want to invert these curves and use them for EQ. But these curves reveal that the tonal balance changes with level and in this regard, it is the bass that changes the most.

I had previously thought that the equal loudness contours explained the harshness of some speakers when turned up loud. The contours don't support that view. Perception of treble stays about the same at high levels. In reality this might be explained in terms of system stress where distortion causes the treble to sound louder, especially where the amp is clipping.

What do we learn?

• 10 dB in the midrange sounds twice as loud
• 6 dB in the bass range sounds twice as loud - this number decreases at high SPL levels
• Maximum sensitivity - 200 - 7k
• Peak sensitivity 3.5k
• A dip in sensitivity occurs around 10k

This is a placeholder right now for the acoustic treatment I'm using in my room, which is a work in progress. Who wants their room to look like a stack of stock panels have been thrown up into their room? Even if you have a dedicated room, you really don't want that look and sometimes you need to go for custom work to get the look you want. The scheme I'm working on includes:

1. Large corner bass traps (floor to ceiling and 1.1m wide) which serves as a baffle for Synergy horns and also hides my active woofers.

These are made and waiting for my S3 point source horns. They include a pegboard membrane on the front and are wrapped in black cloth and use rigid fibreglass.

The baffle will allow me to have an ideal mouth termination on the horn. It will also visually integrate the horns into the room. Basically they will disappear, I'm going for the invisible built-in look.

2. Rug on the bare timber floor (probably).

3. Soffit bass traps at the ceiling/wall junction over the listening position.

This location is the most "out of sight" and in a small room this is important.

4. Rear corner bass trap.

This could either be a large broadband trap, which I've used here previously, or an arrangement of L shaped pressure traps or helmholz resonators. The broadband trap works, but will conflict a little with the surrounds on the side walls. It's a good excuse to go to the extra effort to experiment with narrow band low profile traps.

5. Diffusers.

In my room which is small, the focus is firstly on treating the bass and then on improving the overall sonic signature of the room. The Synergy horn changes the game a little, because it eliminates first reflection points. There are less reflections to deal with, so room reflections take on a longer path and are less dominant. Being a small room, the focus shifts to retaining some of that energy and diffusers tend to have a more natural sound than a bare wall.

You may recall this reverb time chart posted recently:


The orange line is my S2 and you can see the even reverb that is quite a bit lower than the other two rooms. The blue line is a room at the Australian hifi show. The red is a large and open room with some Linkwitz Orion speakers. Apart from the unexpected anomaly in the midrange, the orange line shows close to ideal performance in a small room.

Custom treatment and room analysis

In combination with my room meaurement service, I also now offer custom room treatment. No longer can you say "yes but my wife won't approve!" This service is available in Melbourne.

Not in Melbourne? I'm now introducing a remote room consultation service, whereby you take your own measurements, following instructions provided, and I will then analyse the results and make sense of them for you. In many cases, online help in this area on forums is a case of the blind leading the blind, and many people  don't have time for a wild goose chase. You need to know what tools to buy, exactly how to measure, what to measure and then how to interpret the results and then what to do with them. I can help with all of these aspects, and in the end, if you make further changes in your system, or even move house, you will still have the tools.

Request room measurement service >

Do you want to have your room measured? I provide a service in Melbourne, but if you aren't in Melbourne there is another option. There are a couple of challenges and I can help with all of them:

1. Knowing what to buy

It's very easy to buy equipment that doesn't work. Rather than go through a trial and error process, I can save you the hassle and expense, pointing to the lowest cost effective options.

2. Knowing what to measure

I can provide instructions. Online threads with different individuals of varying experience often means going through a wild goose chase. When you know what to measure, you can do it in one sweep. If you are waiting for a time slot with the kids away, this matters!

3. Understanding the results

Very important!

4. Knowing what to do with them

This is critical - the point in measuring is then being able to use those measurements to improve your system.

One of the benefits of this service is that you can repeat your measurements later as you make changes in your system.

Enquire about this service >

Read more about room measurement >

This term has always annoyed me:

"You get what you pay for!"

It's the line that people use when justifying spending more where it's not really clear what extra you are getting. Sometimes we fall for the price quality illusion. We instinctively feel that the more expensive product must be better. In many cases, it may have more to do with what the manufacturer knows they can charge.

Today I stumbled across a story I had heard before. One high end manufacturer got caught out when they packaged up a much cheaper Bluray player into a new case, then jacked up the price. The Oppo original cost US $500. Lexicon added $3000 to the price without changing the internals. Whilst this is a blatant example, I'm sure there is a lot more of this going on.

Why does it happen? I believe the main reason is that they can get away with it. The reason they can get away with it is that the performance differences between a $500 and $3500 player are often more imagined than real. If manufacturers were expected to produce a product that is easily recognised as superior and if this were really evaluated properly, this kind of thing would not happen. A manufacturer who tried something like this would get a bad name. I believe modern manufacturing and engineering means that decently transparent devices can be made affordable. Lexicon know that people will pay for their name and their better case.

So in this case, what are you paying for? You're paying for a nice case. You're paying for their marketing. You're paying for the perception that their name confers better performance. You're paying for staff to think up ways to charge more without actually offering real performance.  

Yep, you get what you pay for ... but that doesn't make it a good buy!

Read about it on Audioholics >

JV60 crossover upgrade


This is an upgraded crossover to the Jaycar JV60 kit. It uses good quality Jantzen audio components.

This works well with the transmission line design shown elsewhere.

Painting over butt joins can be a challenge. Previously I've shown some samples where I've tried different methods of achieving a seamless butt join with a paint finish over, using automotive paint. They are now complete:



This one illustrates the problem. Ply also has issues:



A cheat solution (shown in ply) is grooves:

 

A better solution uses fibreglass reinforced filler, with two part filler over



You can see the end grain has started to show through.

The best result was achieved with MDF:


It turns out that MDF is actually easier to work with than ply, where the entire surface must also get some attention. 

Synergy horn flat pack deposits are now due. One allotment is now being made, with payment due on July 31. If there are more orders then they will be added to the next run in September, but payment in advance is required - basically right away.

If you are outside Australia and have not done so already - please send through your email address so we can send you a Paypal invoice.

For those within Australia, please contact me and I will send you the details for direct deposit.

I don't like to rush people, but unfortunately I was not aware of the deadline except for a few days before. My apologies and I hope that this does not prevent people from being able to take advantage of the kit.

At this stage, due to the short notice, we are asking an amount that allows us to cover the cost of ordering drivers.

Contact form >

I have just sent out an email to everyone who has expressed interest. Time has come to put down deposits (for those who need the drivers).

If you didn't get the email - subscribe here >

If you previously expressed interest and didn't hear back - let me know!

I believe I have responded to all enquiries (although one did bounce back).

The S3 design is taking longer than expected! This is often the case with anything worth doing, where you insist on getting it "just right." Currently I'm working on the details of how it will be machined and how the parts will all fit together. I hope to have an update in the next two weeks.

The box for HE2 is almost complete. This one was built manually and it's the demo/prototype. It features a very narrow baffle for 10" drivers with a 13mm roundover and a generous shelf port which eliminates port compression. Bitumin rubber damping also makes the box more dead. Future versions will be CNC machined to keep the price down.


The internal compartment behind the midwoofer will be completely filled to keep the midrange clean and neutral. Most of the box won't be filled to preserve the bass response.


The crossover will be mounted behind the waveguide. You can see the texture of the side walls where bitumin rubber has been mixed with 6mm screenings. The bitumin rubber adds both mass and damping whilst sealing the box. 


Once finishing touches have been applied, it will have a clear finish. I currenly have a Weston Acoustics valve amplifier to test the match. This speaker is intended for valve amplifiers. I'm currently considering making two different crossovers available - depending on whether one intends to use a valve or solid state amp. The valve version would use ferrite cored inductors which have the lowest possible DC resistance, better preserving damping factor and maximising efficiency. The solid state version would use air cored inductors with a slightly higher DC resistance due to the extra copper required. The solid state version might also have more bafflestep compensation.

Box built. B&C 8PS21 8" woofer + Dayton round 10" waveguide + DE250.

This surround will sit as shown here as there is just one row of seating, this is why the horizontal mounting. There will be a slight vertical tilt down and the off axis response will cause seats near the surround to still image well.


Bitumin rubber box damping has been applied to the box, so it is quite dead. This box is my trial speaker for a finishing method I have in mind, aimed at eliminating butt join seams which always appear when MDF is painted. I'm using layers of fibreglass reinforced auto filler and fibreglass resin. The result is a very hard and durable skin applied to the MDF. It makes painting much more labour intensive!

1. 6" stand mount kit

Two way passive speaker - bass reflex.
SB Acoustics midwoofer and ring radiator tweeter.
Flat pack with 18mm MDF.
Pre-assembled crossover.
Active crossover option available.
Box and crossover upgrades.

There are a lot of "me too" stand mount speakers out there, but there are two reasons behind this offer. The first is that the demise of LSK has left a void in the market. The second is that I would like to lift the standard of kits. Typical kit offerings have butt jointed MDF, meaning a painted finish won't work well as seams will appear. Veneering is a good choice but ends up with square edges and no attention to baffle edge diffraction. The design I have in mind here allows for a painted front baffle - easily done with a low cost spray can. All other edges can be veneered and there is a groove between the two finishes.

There are options out there for small, cheap speakers. This isn't an attempt to compete with those, but instead it's aimed as competition to higher end speakers.

2. Transmission line floorstanders

Two way passive transmission line.
SB Acoustics midwoofer and ring radiator tweeter.
Flat pack with 18mm MDF.
Pre-assembled crossover.
Active crossover option available.
Box and crossover upgrades.

The transmission line speaker shown here is my most popular page to date. The beauty of a transmission line is that you get the extension of a bass reflex yet the design allows the entire box to be filled, resulting in a very neutral and natural midrange and tight articulate bass.

3. Open baffle kit

High sensitivity design with a hybrid active/passive crossover, neo compression driver with a waveguide, 6" mid and pro woofers.

4. Home Cinema LCR

5. Surround

6. 18" HT sub

7. 18" active woofer

TBA ...

Upgraded crossovers that have been assembled are now available for JV60.

Made to order. Including Jantzen caps, MOX resistors and custom wound air cored inductors.

Compared to the JV60, all parts are better quality. All the parts that aren't needed have been removed. Tweeter Lpad added. Ferrite cored inductors are not suitable for this speaker, so they are replaced with custom wound air cored inductors with AWG 13 copper. That is heavier gauge than just about any inductor you can buy as a standard item.

Contact me if you would like to enquire further or order

Currently considering offering speaker kits, including a flat pack of 18mm MDF, drivers, crossovers and accessories. 

Conventional designs available as a stand mount or floorstander.

It's also possible that I could create designs based around waveguides, compression drivers (or horn loaded ring radiators) and high sensitivity drivers. 

I could offer 3 levels.

Budget kits

These would use good quality drivers that would not be familiar. Don't worry, they wouldn't be junk drivers, but would need to be good value and good quality. They need to be well-behaved drivers because in a budget kit, you can't throw money at too many crossover parts to fix problems. They would also use low cost crossover parts (no electro caps though!)

Mid level kits

These would use more familiar drivers like SB Acoustics, Vifa and Peerless. Crossover parts would also bump the price up a little more, including more familiar name brand parts.

High end kits

My recent poll shows that people are most keen on budget kits, but if the interest is expressed, I can also offer high end kits using high end drivers like Scan Speak, Acoustic Elegance, B&C and the like. The cost would be quite a bit more, but your money is going into better parts.

It's quite likely I'll be developing the budget and mid level kits in the coming weeks. With high end kits however, it will take an order to kick start it.

Currently considering offering a flat pack with some efficient 18" pro woofers, ideal to run below Synergy horns and also ideal for a very high output dynamic system.

A number of posts back you can see 3 Celestion woofers on offer.

Contact me to express interest

One useful feature of REW is the ability to measure reverb time. Here are 3 rooms compared:


Red: Pixelplay's room with Linkwitz Orions - a large room open to other spaces with glass and bricks, minimal treatment on the rear wall. See room >

Blue: Earle Weston's room at the Melbourne hifi show. A small hotel room with no treatment, concrete floor, carpet and some solid party walls. See room >

Orange: My room with 3 large bass traps and prototype Synergy horns.

You can see that with my room, the reverb time is lower due to the much larger amount of absorption used and the size of the room. It is consistent with high frequency energy only slightly diminished and the lower midrange starts to drop down, which explains partly why this region sounds very clean and dry, the bass traps are doing a great deal in that region. For the sake of a more consistent reverb time, and in the interests of perfectionism, I might add membranes to the traps. In fact I have done just that since taking this measurement. Some may prefer a little more reverb for a music system, but in a small room it's generally better to have it slightly dead than have a more coloured room. The constant directivity of the Synergy horns is also a factor in getting a consistent reverb time - there is less reliance on room reflections and the response is more "speaker dominated."

Earle's show room is more like many will be familiar with, where the midrange is getting more boost from room reflections. Carpet and furnishings are reducing the top end reverb, but aren't thick enough to work lower down, so you see the uneven reverb. Selective treatment in this room could pull down the midrange but preserve the top end. As it stands, it was a bit coloured and for critical longer term listening would need some attention.

Pixelplay's' room shows a similar reverb but at a higher level. The use of a dipole speaker with a reflective front wall is part of what is seen here. The space is open with a mezzanine above and openings to a space behind the room and there is a high ceiling.

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.

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:

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.
 

For all who have expressed interest

If you have not heard back from me, please try contacting me again. I have replied to all enquiries (unless I have missed any by mistake). I've just had one email bounce back.

Celestion midranges

The order has been placed.

Cost

To be confirmed, as there are a few things still being determined that may affect the price. Better quality ply will be used, and this costs more than what was originally intended.

Plans

At this stage plans won't be provided.

Progress on the design

Still finalising the 3D form with all the details sorted for CNC. This part is quite detailed, and it will be more elaborate than S2. It's quite a bit of work to get it to the stage that it can all fit together for quick assembly. I'm aiming for a flat pack that can be assembled in a day.

What is coming

I will be getting one assembled and tested before taking deposits. This means you can see what you are getting, at least on the blog, before putting money down.

At that point I will revise the price with the final CNC quote and show the results. Then we can roll them out.