Acoustic Elegance AV12 prototype subs

Introduction

These are dual prototype subs. I intend to build an elaborate subwoofer box, but this will come later. I find they work well for both music and home theatre as long as they aren't crossed too high. Even in sealed boxes their output is well beyond what I normally get the chance to use. I'd need to move into another space before I could use anything close to their SPL potential.

Design Goals

The room: 3.9 x 4.9m with a 2.9m ceiling (12' 15' x 9')
Plasterboard construction, particleboard floor - no room gain but a room mode peak @ 35 Hz
Goals: 105 dB down to close to 20 Hz
Use: Both music and home theatre. I listen to a range of music, actually a little of everything. I find the challenge is getting acoustic double bass to sound right. I often use jazz music as a reference.

Design Decisions

Regarding the box design I haven't yet decided on a final design.
I consider getting a flat response in-room to be critical to accuracy. I use Behringer Ultracurve DEQ2496 for both my subs and mains. This ensures there is no boom. I intend to add Ultradrive DCX in the near future. I'm currently using a kit for the filters, which includes a rumble filter and 2nd order high pass which I have set around 40 Hz.
The RTA function of Ultracurve gives an idea of in-room response, and shows the sealed prototype boxes have an in-room response down to ~23 Hz with no boost added.

Details

Net box volume: 70L / 2.5 cu ft(L/cu ft)
Materials used: MDF/particleboard
Box dimensions: 320W x 900H x 320D
Amplifier: Behringer Europower EP2500 AU $630
Driver: AE speakers AV12, purchased for $US 120 each in a pre-order; actual cost $AUD 320 each

Shipping took a long time since I had it shipped surface mail to get the best price possible. I consider it a better buy than local alternatives, such as the Shiva which went for $AU 300 at the time.

Evaluation: how does it sound?

Initial impressions were less than favourable! Most likely this was due to knowing very little at the time about integration, room modes, and the need to "break in" a driver. The suspension was very stiff initially. After some breaking in, I noticed an improvement.

I have run this sub as high as 80 Hz and I have found the top end of these drivers to be poor. I consider this sub to be equivalent in sound quality to the 15" Tempest and 12" Shiva (this applies to the new range available around the end of 2005/early 2006).

Like most subwoofer drivers, the response is useable only to about 40 or 50 Hz for applications where accuracy is crucial such as acoustic double bass. For home theatre only, an 80 Hz crossover point may be acceptable. My transmission line speakers are far more articulate in the 40 - 80 Hz range

Comments on power

The AV12 has a lot of displacement for the money you pay. It's hard to beat in this area. I consider it an economical way to get some brute force and move some serious air. However, it requires more power to make use of that excursion than a number of other drivers with a smaller xmax. I consider at least 500 watts to be preferable. I've used a number 450w pro amps and found that I could easily get them to clip while the driver had quite a bit more to give. My amp is a pro amp with 750w and I find it is a good match. If you want more power then you need more subs - there is a point where you end up throwing away a lot of money on ultra high power amps with no return. You could easily spend 4x the cost of the EP2500 in a failed attempt to get more output - all you will achieve is more power compression. Power compression means that doubling the power does not yield an extra 3 dB of output, but instead you may get 1 dB at best! It's quite common for high power speakers to have 3dB of power compression when fed a few hundred watts of power.

That said, it is always a good idea to have more power than you need available, as long as you can do it economically. This is a power hungry driver. It is quite sensible to have the power of the amp I use as long as you use it sensibly. This means using a rumble filter ESPECIALLY if you have a vented sub. It also means becoming familiar with the limits of your subwoofer by turning up the volume slowly, finding the most bass-heavy material you are likely to use, and getting an idea of the excursion you can expect with DVDs and with CDs.

I recommend using high power pro amps to get the kind of power you need to do justice to a driver like this, and I know of no amp that has more bang for buck than the Behringer EP2500.

Conclusion

I recommend this driver and amp combination for LFE use. While I use mine for music, I cross low. I think you will find this applies to many other popular drivers. If you want to cross higher and accuracy is important, then start looking for other drivers. Peerless XLS, TC sounds 2+ or XBL^2 drivers come to mind as candidates. If you have mains that you intend to use down to 40 Hz then these subs will perform well and are hard to beat in terms of bang for buck.