Subwoofer integration - worked example 1

Here is a worked example of setting up, measuring and tweaking bass in a typical room.

Update

I strongly recommend that you aim to add bass traps to your room. Not convinced it's worth it? Take the free bass trap test. I have found bass traps make a bigger difference than the EQ shown here, although both together is even better.


The room is 4.65m wide, 3.9m deep with a fairly high 2.85m ceiling. It's lightly constructed with timber floor, plasterboard lining and light exterior cladding. The entire room is like a big bass trap although I've added some extra layers of plasterboard. Unless you have a very big room, you probably won't get much better and if you have concrete and bricks then you may have bigger bass problems than you see here.

So here is the response for the subwoofers:



Green: left sub
Red: right sub
Black: both combined
Horizontal divisions are 8db

Both are in corners and as I sit left of centre there is a different response for each. Combining them makes their midbass gain wider. They both have a dip around 70 Hz and higher up the crossover kicks in. You can see the combined response tracks the maximum output, and dips are not subtractive. You can see towards the bottom end, they tend to combine better. Down there we get about 4db gain from using two subs - not the 6db that is typically predicted. So you can see that two subs don't gain a massive output increase, but provide some smoothing. In this case, if you were to use just one sub, you would choose the right corner.

Don't pay too much attention to the absolute levels. In some cases I had to adjust the levels between measurements. Only consider the levels relative to the other curves in each chart. These measurements were taken for my own experiments, not for this blog post!

Next the main speakers. These were my TL speakers, which I've since sold to a happy new owner. More details on the speakers >



Magenta: left TL
Brown: right TL
Black: combined

You can start to see some benefit here in the mains having bass, rather than simply setting them to small and rolling off the bass. They are a bit flatter where the corner subs have dips. They still have the mid bass peaks, but don't seem to suffer the 70 Hz dip, which would take quite a bit of power to boost.

Notice how they help each other? Two dips around 100 Hz improve and overall we have a result combined that is better than either curve. If we were to see a 1/3 octave smoothed chart (which is more like what we actually hear) then we would see simply a series of broad peaks. In fact these charts show that if we didn't have EQ ability, the mains would probably sound the most accurate. Most would turn off the subs for music and be happy with that.

No smoothing

I prefer to look at unsmoothed charts for bass as they are useful to see what is happening. However, they tend to exaggerate problems and show things we can't hear. We perceive something more like 1/3 octave smoothing, as shown below:



What this shows is that we could use a little boost for the bass overall, and we could smooth out the bass humps a little, but for an in-room result, that is pretty good.

Now, I'll combine everything:



Green: TLs
Red: subs
Black: all combined
Blue: final result with EQ and smoothing - level raised for clarity

Note: levels are not correct!
During measuring, sometimes the levels have to be changed due to clipping. The level of each curve has been manually adjusted to what I think they probably should be.

So you can see the TLs are nice and smooth, but don't give me all the extension I'm looking for as well as bass impact. The subs have this and do pretty well in their range, but the mains are needed to fill in the 70 Hz dip. The black curve shows all combined with the mains running down to 60 Hz - high pass filtering provided there so they go no deeper than I actually need. Then the blue curve shows the final result after EQ has been applied with some parametric filters. I've smoothed only this curve so you can see it as it would sound to the ears (1/3 octave smoothing). I used a number of parametric filters to pull out the peaks and fill in some dips. I've set it up to avoid the dips being too bad.

Conclusion

With all these four bass sources now combined and calibrated nice and flat, the result is better than I could achieve with any of the parts on their own. What you can't tell from these measurements, is that the bass has more brute force than the mains are capable of, yet the subs are more articulate than they would be if set up without this kind of attention. Desipte being very capable and accurate they could in fact sound fat and bloated through no fault of their own, simply due to room effects. When trying to do this by ear, you end up with an inferior result. You end up changing the volume. You will hear music that hits those peaks and set the level based on them, but at other points the bass is missing so you turn it up. You end up with an unhappy compromise with less bass than you want at times, due to turning it down to try to tame the peaks. The final result that you see here combines the best of both the TL mains and the subs. The subs add impact, extension and force without making the bass less accurate.

Where do I go from here? I hope to get a flatter response still prior to EQ and add headroom to all the bass sources, with my new mains with some Acoustic Elegance woofers and horn loaded versions of the subs, along with a third tapped horn for the very low frequencies.

Equipment used:

Behringer ECM8000 measurement mic
Behringer Xenyx 502 mixer (preamp mic)
Room EQ Wizard software

More about a simple measurement setup >

It's also important to note that in my room, I have two critical seats and they measure almost identically. In many other rooms this won't be the case, and more measurements are needed.

Glossary

Confused about audio speak? Here are some terms I keep using, it's a work in progress.

Room modes
In a typical domestic sized room, the bass response is lumpy - it has peaks and dips which are the evidence of "room modes." They are points in the room where the bass is stuffed.

Shroeder frequency
This is the point above which room modes are spaced so close together that they smooth out and the room no longer causes irregular peaks and dips. This usually occurs around 200 Hz.

Can you simulate room modes?

There are a few different tools to simulate room modes. Are they useful? Let's find out.

Here is a measurement of a subwoofer in my room. It's a nearfield measurement, just to show you what the subwoofer is doing.



You can see the measurement is very smooth so far, and the small peak above 160 Hz is a measurement artifact.

The sub is a Rythmik servo sub:



Next I'll attempt to simulate the response of the room using the FRDC Room response calculator.



Subwoofers are placed in corners, and the "mic" in the listening position. The program assumes perfect response from the subwoofer - totally flat over that range.

Here we have two versions of the same room. One is built like a concrete bomb shelter (no damping). You can see we get narrow dips and peaks with no damping. The other has damping such as we would find in a room constructed more lightly - plasterboard walls, timber floor, etc.

Now let's look at an actual measurement:



At first glance it looks quite different, and it's tempting to dismiss the simulation. Firstly, the room gain appears to be exaggerated in the model. We can see 3 main dips in the measurement - 70, 100 and 150 Hz and these are reflected in the model to a degree.

Conclusion

Are the simulations accurate? As you can see, it's a bit hit and miss. You can't rely on them fully, but let's suppose I gave it some more time and fiddled until I came a bit closer to the measurements. I could use different values for how much each room surface absorbs. I could then use it as a tool to quickly show the impact of different placements quickly. That has some value, but it certainly won't replace measurements. You will need those before you can be confident in your results. If you are hoping to use this tool to design a room before construction, I would use some caution.

Bass horn room integration

There are two aspects of integrating a bass horn. One is a practical challenge of fitting it in your room physically. The other is acoustically getting it to work in your system and room.

Room loading

Ideally a bass horn should load into a corner. That allows the horn to be smaller as the corner becomes an extension of the horn. In an extreme design where the horn mouth takes up an entire wall, the horn sees more loading than a corner so the walls can become part of the horn.



If you create a raised stage as shown below, then you have a mix of loadings. Horizontally it sees more loading than a corner horn, but vertically it sees halfspace loading. A rough guess would be to treat it as half way in between - quarter space loading.



What is all this space talk?

Put a bass horn up in the air and the bass radiates in all directions. We call that full space. Put it on the ground and we've cut that in half so it's called half space. 6db acoustic gain in theory results, less in practice due to transmission and absorption through the enclosure. Add a wall next to it and we call it quarter space as the radiation is divided in half yet again with 6db more gain. A corner adds another wall so we call this eighth space. So if you took the bass horn seen above, which we will describe as quarter space, and loaded it into a corner it could be half the size. We could cut the platform in half and turn it up on it's side on the right or left wall running floor to ceiling. It would do the same job, although it would destroy summetry. Another option would be to extend the front wall which has the screen. The horns would each fire into the corners and not be quite as wide as the room. Which option is preferable depends on the room dimensions.

Room modes

It's important to keep in mind that while a bass horn can be an ultimate solution, it may require more bass sources to even out room response. Generally corner loading is needed and there may be a need to add a few more bass sources to get a smooth result. Typically you will see peaks and dips in the response and extra subs can fill in the dips, then you can use EQ to remove the peaks. So it should be kept in mind that a beastly bass horn won't give you perfect bass.

Measure your room

Before you build a bass horn, measure the room. You'll need a bass speaker which can play low enough to see what you are dealing with. Measure it with the mic right up to the cone, then measure the in-room response. That way you can see what the room is doing to the response. Imagine if you put a corner horn and get a -15 db dip at 60 Hz. You will give up all the headroom gained if you boost the dip.

Combining subs

A better idea is to measure the entire room, then place another sub so that it will remove the dip. You might get creative with positions and consider a coffee table subwoofer. You might also use a combination of front loaded and tapped horns. A TH for deep bass extension, then a midbass horn extending where it leaves off. You might add a smaller sub in a closer position to fill in some dips.

3 bass horns

There are three basic types of bass horn:

• Front loaded horn (FLH)
• Back loaded horn (BLH) - sometimes referred to as a scoop bin
• Tapped horn (TH)

Conventional horns are either front or rear loaded, as shown below:

Front loaded horn

Back loaded horn

The only physical difference in theory is the rear chamber. A front loaded horn is the best choice for efficiency and accuracy with limited bandwidth woofer or subwoofer applications. The sealed chamber helps with controlling the behaviour of the bottom end. It restricts cone motion so that the cone is loaded on both sides - behind with the air spring from the chamber, and in front with the mass of air on the horn. This causes the driver to perform in a more linear fashion than if loaded only on one side as a direct radiator.

A back loaded horn lacks the sealed chamber and so may require a high pass below cutoff to protect the driver. The sound from the rear of the driver causes cancellation and is problemmatic. However, a back loaded design is appropriate for a wider bandwidth and some drivers are made for this type of design. If you see a 15" pro driver with 100db sensitivity or higher, and an early drooping response, it's probably intended for a BLH where the horn brings the sensitivity up. Some full range hifi drivers perform well in this type of horn.

A tapped horn is very different. There is some debate whether it should be classed as a horn and many have described it as a bandpass or transmission line. While there are similarities, there are also differences so I consider it best to simply accept it as a special type of horn with it's own set of characteristics.

A tapped horn can achieve high efficiency but is even more difficult to design. The size is smaller and they can as a result be used practically for a lower cutoff. Often the bandwidth is less than a conventional horn and many drivers don't suit a TH. The response is also peaky.

The best of both

Tapped horns and conventional horns can work together well. Start with a tapped horn for the bass and it will provide as much extension and low frequency output as you want, but over a narrow bandwidth. You might aim for 15 - 50 Hz for a home theatre system or 35 - 120 Hz for a music system. Then you can cross to a FLH which can now be much smaller. Ideally the TH would have more power and a driver with more excursion, and the FLH would use a driver designed for midbass efficiency.

Bass horn SAF

Let's deal with the biggest challenge first - spouse approval. A single guy can build a bass horn as big as he wants, but most audio enthusiasts have to get it past the interior design committee. So for most a bass horn seems out of question. Anything bigger than a tissue box is sometimes met with "can't you make it invisible?" I have some suggestions that can make your wildest bass horn fantasies come true.



Image source >

Are you a home owner?

If the answer is yes then you have a lot of options. A bass horn needs to be attached to the room, but it doesn't have to be in the room. One way to do it is build a false wall and if building from scratch you might allow for this. Or you could build it very much like a fireplace where the chimney is the same width as the bottom part. This could work in a big room.



Image Source >

Consider every surface in the room - ceiling, floor, walls. An attic could become a bass horn, although construction is a challenge. Subfloor space is also possible if you have a timber floor. Unused cupboard space in an adjacent room? Many options here.

Covert subwoofers

If the above aren't options, there is no need for fretting and frustration, here are some alternatives. Firstly, a covert subwoofer. Let's face it - every home has big items that we all accept because we realise they have a function that makes size an issue. Cars, fridges, freezers, Air Conditioners, Heaters, fireplaces, computers, pantrys, wardrobes, built in ducts, dining tables, benches, couches, coffee tables, buffet units, fish tanks. All these are space hungry consumers but how often do you hear of men complaining their wife won't let him have a big fridge?! So the solution for some can be to build a fish tank subwoofer!

Can you make it look like a piece of furniture? Or can you make it look like part of the room? You might build a false wall subwoofer. It simply looks like a part of the room, same paint as the walls, and even a skirting board. It does not need to be actually built in.

Two approaches

So there you have two approaches that could work quite well, depending on your situation. Obviously it won't work for everyone - a lot of rooms don't allow any kind of bass horn and some partners won't come around to the idea of a bass horn. Still, there are a lot of would-be bass horn owners who simply need a new idea. And even if your partner is fussy, you might even be able to work together on something together.

Bass horns online

First, the biggest bass horn in the world:



The most powerful:



Danley Matterhorn. This is a tapped horn with 40 high excursion drivers and 40kw of power. Designed for military use where 105db is required outdoors at 15 Hz one quarter of a kilometer away! The US military approached Tom Danley when they weren't able to meet their target with a sub that fits into a shipping container.

One of the more stylish options:



Avant Garde >

Now let's come back down to earth. Here are some designs that you could actually build and use in a domestic room.

William Cowan sub jr

http://www.cowanaudio.com/hornsubjr.html



Volvotreter.de

http://www.volvotreter.de/th.htm

Compact and large tapped horns



Speakerplans.com

Here you will find a range of horns designed for pro use, as well as bandpass designs.

http://www.speakerplans.com/

Lab horn

This is a diy favourite intended for pro use designed by Tom Danley. It uses the Eminence Lab 12 driver which was designed for the application. Some have had good results for home use.

Pro sound web info >

Pi Speakers bass horn kit



http://www.pispeakers.com/Products.html

This is a commercial subwoofer that is based on the Lab horn - essentially an improved larger version.

Vincent Brient straight bass horn

30 Hz straight horn >

Bass horn introduction

If you are a bass nut, nothing is more impressive than a bass horn. It's the audio equivalent of an all you can eat buffet that costs no more than cheap take away yet has all the refinement of an exclusive restaurant where the main course is more like an entre.



Forum link >

All you can eat bass
Very high efficiency means you can have it as loud as you want.

Low cost
Modest drivers and power amps are fine and MDF is cheap.

Refined bass
Horn loading transforms a modest driver into a more refined reproducer of bass.

It all sounds too good to be true. There must be a downside. Actually there are a few. The small number of commercial options are extremely expensive and tend to be compromised designs. Bass horns are more suited to DIY enthusiasts. Bass horns are bigger than every other type of sub and they are also the most difficult to design. But if you are a serious bass nut, you can overcome all the challenges and get the best bass you can imagine.

Have you dismissed the idea due to SAF issues? Perhaps there is still a way you can keep your spouse and have the bass horn too. Don't write it off just yet. A little creativity might save you from a life time of bass boredom.

In this coming series of articles, I'm going to cover:

• how to get your bass horn approved by the interior design committee without resorting to bribery and grovelling
• how to integrate a bass horn into your room
• different types of bass horns - tapped horn, front and back loaded horns
• how to simulate bass horns
• how to work out the folding and make your design into a box plan
• resource of bass horn designs
• bass horn lingo - what all those nerdy tech words mean in plain English
• bass horn theory - the non boring bits

If you'd like to follow the updates, click on the follow bottom in the right column.

In the meantime, you can see some previous posts on the diy audio wiki.

When you feel the urge to tweak

Ever get the urge to tweak some budget speakers? Can they be a bit better with a little work? Here are some suggestions ...

1. Tweeter level

First, consider tweeter level. You can change this by adding an Lpad, which is two resistors one in series and one in parallel with the tweeter. If you already have a pad, then you might change the value. More about Lpads >

2. Enclosure

Is the enclosure solid and inert? You could add some bracing or dampen it with mass (lead). You could also consider new or different filling and/or lining.

3. Vents

Sometimes it's a good idea to block up a vent. Perhaps you have a subwoofer and may benefit here. Perhaps the vent isn't helping. If you block the vent, then add stuffing and this should improve the midrange as well.

4. Baffle diffraction

This usually receives scant attention in budget designs. Sound travels across the box and at the corner it diffracts. This means it arrives slightly later than the direct sound and it will have a detrimental impact on imaging. A simple tweak to improve the situation is to place foam on the baffle, especially around the tweeter. You can apply a piece of open cell foam, with a cut out for the tweeter.

5. Crossover parts

Tweeter caps could be replaced with better quality caps of the same value. This is often where corners are cut. Cheap caps are very cheap, good caps are quite a bit more expensive. In budget speakers, often the very cheapest of parts are used.

6. Crossover re-design

Feeling ambitious? Often budget speakers are made so cheap that they even cut corners in making the crossover simpler than it should be. Sometimes this might mean a simple cap on the tweeter and nothing more. The extreme simplicity may appeal intuitively, but this is more likely cost cutting winning over performance. You could start with free softare and some basic tools quite cheaply, but be ready for a learning curve.

7. Active crossover

This is actually a simpler option. You'll need preamp outputs and two power amps as well as an active crossover. A low cost option such as MiniDSP is a good choice. More about active options >

Quick 'n Dirty active OB

This is what I'm listening to right now:



This is an active system to keep me happy until I get something serious setup.

Tweeter: Vifa D19TD05
Mid: Modified Vifa C13 (From a Diva Acoustics stand mount)
Subs: Rythmik 12" servo sub
Crossover: Behringer Ultradrive DCX
EQ: Behringer Ultracurve DEQ
Power amps: Behringer A500 and EP2500
Box material: cheapo 12mm chipboard and furry 18mm MDF

The rack:



I'm surprised how good it sounds. I could close my eyes and think that I'm listening to a refined system, not something thrown together out of scraps.

I set it up like this.

1. 4LR crossover set at 160 and 2.4k

2. Pink noise + RTA to set the gain

3. Auto EQ with my standard room curve (1db/octave lowpass fullrange, ~6db bass boost, -2.5db treble cut and dynamic loudness filter)

DSP settings:



DSP: you can see in the top window that dipole EQ happens below about 300 Hz down to the crossover point of 160 Hz. Below that there is some EQ for room modes, but not shown is a PEQ notch filter around 40 Hz for a dominant peak.

That took all of 5 minutes, then I sat back and had a listen. Wow. I expected to hear the mid having just a little coloration, but nothing stood out. There was no sense that anything was asking for improvement, even though there is obviously a lot that I could easily improve. Drivers, cables, enclosures, crossover and EQ settings ... virtually everything could be better. Yet it's easily good enough to just sit back and be immersed in music. In fact, that's what I like best about open baffle. It's very engaging, drawing you into the music. The sound stage seems to extend so much further beyond the speakers. My only complaint is that I'm not satisfied with what it's doing with voices on movies. Image focus is stretched and I get the feeling vocal clarity is lacking.

Open baffle made easy

Here is a simple path to open baffle bliss. You could put this together in a weekend and see if open baffle is for you.

1. First start with either a full range driver or a conventional passive 2 way with a tweeter and mid.

The full range driver can appeal with it's simplicity, although finding the right driver with the right trade offs can be challenging. You want one with a reasonably flat response, top end extension, reasonable xmax and good efficiency.

Some of the Mark Audio drivers at Darcher Audio are worth considering. As shown above.

You might also consider CSS:



Want something exotic? Try this - Tang Band's take on an efficient fullranger. To get an efficient fullranger means a larger cone that now requires a whizzer cone to keep the top end extension. This one is 95 db efficient! It also has a nice flat response and decent xmax. The only issue is that the response slopes up so without EQ it will sound a little forward. If you follow my suggestion that follows and run an active crossover then that is easily fixed. Here it is:


You could also substitute a passive 2 way here, with many designs available on the internet. In keeping with the easy approach, go with an existing design. Check out the usual suspects like Zaph Audio, Tony Gee's Humble Home Made hifi and Troels Gravesen. I'm being lazy here and not hotlinking these, but simply Google them and you'll be there in 5 seconds.

2. Make the baffle about 400mm wide with 100mm folded back wings

That's a decent compromise of extension and modest size.

The dipole roll off can be estimated by adding a first order high pass at fequal to the response in a sealed box.

fequal = 58/D where D is half the baffle width plus the wing depth (in this case 0.3m)

fequal = 193 Hz

A typical 6.5" midbass with an fs of 40 Hz will be -3db @ 80 Hz when sealed.

3. Add a woofer - 12" or 15"

You have a wide baffle, why not use it?

4. Add a digital active xo like DCX or MiniDSP and cross around 300 - 400 Hz so there is no dipole rolloff to compensate for

And there you have a simple open baffle speaker - time to listen to music!

Want to see something like this I've put together? Here is a version I put together out of scraps:

Quick 'n dirty OB >

Check out the options for active crossovers. Behringer DCX is a popular choice, but MiniDSP is a new low cost simple solution that is purpose-designed for diyers. Read more about active options >

The red or blue pill?

Morpheus on the Matrix offered Neo a choice between the red and blue pill. He could choose between blissful ignorance or facing the stark naked truth. The consequences aren't so great, but in audio we face the same choice and I notice that many prefer the blue pill. In case you are wondering, that's the one where the truth eludes you. Let me put the question another way. In an industry where many would take your money without offering anything substantial, are you a sitting duck?

If you enjoy the seduction that goes on before an expensive cable purchase, you probably should stop reading now.

I'm about to suggest what you might begin to see after you take the red pill. The effect won't be as quick as in the Matrix. Taking the red pill is an educational journey. You might do a blind comparison of a low cost amp vs a high end unit. You might start reading white papers. You might get into some theory.

Have you swallowed the blue pill?

Let's do a quick test. Do you believe:

• the only way to evaluate a component is by audition
• blind tests have no value at all
• objective measurements aren't valid
• the human is the ultimate measurement tool
• the ear can hear things that can't be measured
• everything in the signal chain makes a significant audible difference

If you answered yes emphatically to more than one of the above, you have taken the blue pill!

So what will happen if you take the red pill? I have some suggestions. I don't claim to have the final and definitive answers to everything, but I'd like to gently suggest what I consider some sensible opinions that should hold up quite well to scrutiny.

CDs and Recordings
CDs are as good as they need to be. In a reasonably high end system, even one moderately priced, the recording will often be the weak link. It's not because engineers are incompetent, it's because they cater to the majority who aren't audiophiles.

Vinyl
Notorious for fund suckage. Often called the "dark side" for good reason - you don't want to see how much you are spending! Everything in a turntable becomes critical and you need to spend serious money.

Speaker cable and interconnects
They do make a difference, but there is no magic here. The differences can all be accounted for - if you can hear it then it's measurable and science can explain it. Better to admit that you don't understand, than claim no one does. In a system without unusual quirks, the differences between well designed cable are difficult if not impossible to pick. Those on the blue pill will disagree emphatically during their sighted comparisons, but things get interesting when they don't know what they are hearing.

Sources, DACS, preamps
With the exclusion of components which deliberately add a sound of their own, these items even at a low price are generally as good as they need to be. Differences here are subtle.

Amplifiers
The task of an amplifier is to supply a clean unclipped signal into the load the speakers present with low distortion. An amplifier that often clips is inadequate for the system. Any modern well designed amplifier that can meet these requirements is likely to work well. The advantages in spending more once this has been achieved are small.

Speakers
Here is the real challenge. You can cut corners everywhere but here. 90% of the result is decided here. They are the most difficult part to get right and should be the most expensive part by far.

The room
There is a close relationship between the speakers and the room. Try to improve it as much as you can. Together they are a system.

Bass
The hardest aspect of room acoustics. It needs serious attention, often including things like multiple bass sources, acoustic treatment and EQ. You can buy great midrange, but great bass must be tuned to the room. It's the one area where you can't avoid measuring. If you don't have a measurement mic and a mic preamp to hook it up to your PC, you need to buy one now. No excuses!

Conclusion

While this may offend some audiophiles, my intent isn't to offend or aggravate anyone. Instead I want to offer some suggestions to those who want value for money. There are many who would separate you from your money while promising things they can't deliver. Audio is one of the few areas where some will spend 10x as much as they need to without any real improvement. The bizarre truth is that when the mind expects a change, it will often find one, even if the same track is played twice without any change but the mind simply finding something different to focus on. Some have discovered this by accident or even by setting up a trick comparison.

"Did you notice the difference?"
"Definitely. The first time the sound stage was compressed, the midrange veiled! Those cables were terrible!"
"Really, that's interesting, I didn't change anything!"

Speaker cables

If there is one diy project you want to try, it's cables. It's a fairly quick and easy project, you save a great deal and you get the exact length you need.

Here I'm assembling a resource on speaker cables. It's currently a work in progress.

Do speaker cables make a difference?

Absolutely. It's very hard to make sound without them!

Firstly, let's keep things in perspective. In an entry level system, cheap figure of 8 cables for a few dollars per metre are adequate. The cables will never be the weak link. In a higher end system, it's worth getting a bit more serious, but even there I'm not suggesting to spend thousands.

Snake oil free zone

Differences in speaker cables are subtle and they are based on measurable differences. There are some with vested interests that want you to believe that differences can't be measured or quantified. That way they can convince you that their cable is better, even though it doesn't measure better. Others quietly consider themselves part of the audiophile elite - those with golden ears who are above science. They are a cut above the rest of us!

Things that matter

The main properties of a cable are L, R and C - inductance, resistance and capacitance. Capacitance is generally of little consequence to sound quality. We can compromise most in this area. Resistance - we'd prefer to keep it as low as possible, as it will result in losses. Thicker cables tend to have lower resistance, but bigger isn't necessarily better. Longer cables tend to need to be thicker. Inductance - we'd prefer to keep this also as low as possible.

Cables and Safety

Certain cables can't be used with certain amplifiers. High end cables tend to reduce resistance and inductance, but have higher capacitance. This is a problem for Naim and Linn amplifiers that eschew load stabilisation networks. Some caution is needed. If in doubt you should check the manual of your amplifier and check with your retailer.

A low cost high performance DIY solution

Credit for this goes to Trevor (aka Zaphod Beeblebrox at the StereoNET forum). High power coax RG213/U makes a very good low cost speaker cable. Apparently it is better than most pricey boutique speaker cables. The exceptions are expensive and offer a very small improvement.

Why is it so good? It's designed for high frequency use with low loss. That means very low inductance. The cost is around $4/m for small amounts.

How to use it

One coax will do for a passive speaker. The centre conductor carries + and the shield -. You will need to strip back the insulation and solder in lead out wires at each end - one to the centre, the other to the shield. Heatshrink tubing will neaten up the cable.

Why one sub isn't enough

You might think a single sub is one too many or that multiple subs is for the doof doof crowd. Be prepared to have your view challenged as I explain why three subs is about right for both music and home theatre systems.

* article coming soon *

Multi sub posts:

Why two subs isn't enough - Part 1
Why two subs isn't enough - Part 2
Multisub measurements

Site Contents

DIY projects
DSE power amp mod
TL speakers
Rythmik servo subs
Fixing TDL speakers
Budget speakers uncovered

5 DIY subs

Tutorials
& How to articles

How to ...
Use WinISD
Design ports that won't chuff
Solder spades
Set up your sub

Feature Articles

Why one sub isn't enough ...

Bass bliss
A basic guide on how to get there

DIY speakers
DIY speakers the easy way - Part 1

Active crossovers
Options for DIY enthusiasts

Hot Topics
Does fast bass exist?
Blind testing - why is it such a hot topic?

Measurement
& Simulation
Subwoofer in-room response
(It isn't pretty)

Opinions

Majoring on minor issues in audio
Can't afford it?

Quiz
Can you pass the bass test?
A quiz on bass

Subwoofers

You could be forgiven for thinking I'm a subwoofer nut!

Mandatory reading:

Multi subs - part 1
Multi subs - part 2
Multisub measurements
How to set up your sub

Considering building some of your own?

DIY Rythmik Servo subwoofers
5 DIY subs
Subwoofer bracing primer

Exploding a bass myth
Bass horns
High end bandpass?
Bandpass subs - part 2

Bandpass subs - part 2

In part one I introduced bandpass subs as a viable option, especially where placement near the listening position is desired. For home theater systems I suggest considering a 6th order bandpass, which is essentially a vented subwoofer for the extension with a tuned acoustic filtering chamber to control the top end extension.

* to be continued *