Speakers for your room - it matters!

Hello Folks. I thought I’d write a short piece about choosing a speaker for your room - Room modes. I’ve always known the speaker/room is extremely important and have recently become even more aware of the importance of choosing the right speaker for your room. I realise most people know this already, but I’d like to communicate a few of my findings and experience over the years. I realise the amp/speaker interaction is extremely important too, however, this will focus more on the room.

Background:

I have recently heard the ARKE Duos in many different rooms and this has highlighted the very large effect the room has on the performance - mainly the bass and HF. This is NOT a scientific study and I realise there were many variables - it is merely an anecdotal account.

The general voice/tone/character of the speaker remained reasonably consistent between rooms. However, the perceived high frequency output varied considerably. The duos allow the adjustment of HF output by +/-2db, however, the different amounts of in-room absorption could vary the perceived HF output a lot more.

The MAIN difference across all rooms was the bass response - the low frequency extension and perceived output through the bass varied massively. The bass could be incredible in one room and particularly boomy (at certain frequencies) in another room. The boominess (or excessive bass) was always (in my experience) related to the room modes. I had realised the room modes were very important, but now I was hearing the profound effects first hand. Even these little speakers (10 litre volume) were easily exciting room modes. The worst rooms had quite a profoundly detrimental effect on the music! If your room is bad, don’t despair, there are ways to alleviate it or choose a speaker that will work better.

Room modes:

I won’t go into loads of detail as there is plenty of extremely detailed info online. In summary, the main room modes are axial, tangential and oblique. There are plenty of calculators online where you can calculate all of your main modes. I am mainly looking at the axial modes to give some basic examples. Axial are the modes associated with the Length, Width and Height of your room. The main fundamental modes are given by the formula:

Frequency = (speed of sound)/(2 x distance) = 343/(2d)

So if your room length is 4m long the main associated room mode will be 343/(2*4) = 43Hz

Every fundamental mode will have further associated harmonics. The 2nd harmonic being twice the frequency of the 1st or fundamental harmonic. The 3rd harmonic is twice the 2nd and so on. The first modes tend to be the most dominant.

You can do the same calculations for width and height too. The fundamental room modes will usually give you a boost at that frequency. It can be particularly problematic if you have a square room or a room with a length that is exactly twice the width - or any dimension an integer multiple of another.

I realise that many of you will know all this, so I won’t go into any more detail.

So, why is this useful when choosing a speaker?

It is beneficial if you can avoid exciting these modes further by choosing an inappropriate speaker. The worst cases I have heard have ALWAYS been when the port tuning coincides with one of the fundamental room modes. Oli used to have this problem with the Q500s - the port tuning coincided with the length mode and produced a particularly boomy result. My former Ekta mkIIs (port tuning around 37Hz) used to excite the length mode in my previous room also. It is generally less of an issue when your port tuning is lower than most ‘frequent’ musical notes - so generally it is slightly less problematic below 40Hz. My current music room has an axial length mode at 32Hz, which is often useful as it extends the useful bass from most speakers.

Port tuning:

From my experience the most important thing to consider is the port tuning frequency (assuming they have a vented enclosure). This has always produced big Issues in EVERY room I have encountered it in. It is not subtle and will really affect the SQ through the bass, which in turn has a detrimental effect on everything through the frequency range. How do you check? The first thing to do is to check your dominant room modes via an online calculator or quickly calculate your fundamental axial modes like this:

Length Mode Frequency = 343/(2xL) (measure in metres)

Width Mode Frequency = 343/(2xW)

Height Mode Frequency = 343/(2xH)

This is simplistic, but in most rooms the fundamental mode is most likely to coincide with a port tuning.

How do you solve it if you have the problem?

1) Change the speaker, but this isn’t always possible!

2) Try lightly stuffing the port - this will change the port tuning, but isn’t always ideal as it limits the bass extension.

3) Add a sub - I have solved this problem a few times with a sub(s). The ports can be stuffed to lift the port tuning above the dominant room mode. The sub(s) can then be tuned to fill in below. If, for example, the problem frequency is 42Hz (port tuning and room length mode) you can lift the port tuning to around 50Hz (I have done this on a friend’s speaker) and then have the sub come in under 40Hz. This would seemingly leave a suckout in the response from 40-50Hz, but the room mode usually adds a reasonable lift so actually fills it in nicely.

I realise this is only one tiny piece of the puzzle! I’m sure many people on here will disagree and I accept that. This is my experience.

Other factors in play (to name a few) are the speaker boundary interface, amp/speaker interaction and inherent frequency response of the speakers. However, I will say that the port tuning and room interaction has (in my experience) been the most dominant by far. It is definitely worth considering as many people blame it on the speaker, when in reality it is often the room/speaker interaction. For example, the ARKE duos have amazingly tight and decent bass for their size. However, in one room they simply didn’t work. The port tuning was bang on a room mode and the boom (bass lift) wasn’t great. It was fixed reasonably well with a light stuffing of the port, but was still wasn’t ideal.   In the other 6 rooms the ARKE Duos sounded fantastic. BTW: it wasn’t an amp issue, as the amp was consistent in the problem room and my own (not a problem) room.

I realise this is likely to provoke some debate, and others will have different experiences.  This is ONLY my anecdotal experience.  I'd be very interested to hear any other views/experiences.