Trace Elliot SM400

Amp Head

The centre of my Bass Rig is my Trace Elliot SM400 Head. It is rated at 400w RMS @ 4 Ohms and has the optional Black light (UV).

It has a 7 band EQ (with an EQ level rotary and on/off switch) and 2 pre shapes. Another nice feature is the EQ balance rotary. This allows me to shelve the whole pre amp to either a bass or treble bias.

I love this amp - glassy smooth accurate tones with lots of punch and headroom.

Over the last 10 years of Bass playing I have used lots of cabs from various makes and to be honest, I haven't been particularly impressed with any of them. Most are expensive, too large, heavy and very often just don't sound nice. I also have noticed that a lot of manufactures stuff large PA speakers into a box and call it a bass enclosure…yeah right.

So I decided to try a DIY route. The first enclosure I built was centred around a 15" Eminence Kappa driver. It's a great unit but needs a very big enclosure, it has a Vas of 150-300 litres (depending which set of stats I read!). On hind sight I wish that I had used the LF version which is optimised for a 105litre box, but I was obsessed and I saw that the effieciency was less (like a few db's gonna hurt?) and I went for the standard version instead. On hind site I wish I'd used the 15" Kappa LF. When I designed the cab, after I bought the driver, I realised my mistake and I wasn't going to use a box the same size as me. So I put it in a 95litre sealed enclosure instead, which is about half the size it really needs to be...duhhh, more about that later.

 

I didn't want to use the woofer to produce the upper mid range so I chose to use a separate mid range driver with a cross over point of about 2kHz. The crossover was an off the shelf item from Eminence. A 400w beastie and it was the only one that I could find which could handle the power and also had my required crossover point, in this case 1,6Khz (close enough).

Monacor 2.5" Soft Dome Mid-Range

I chose a midrange unit from Monacor, it was an easy choice really, soft dome units give a nice smooth sound and this particular unit comes in it's own sealed basket (so none of the woofer standing waves should effect it) and is rated at 70w RMS which should be enough. This driver gives a very nice even tone - no crappy Piezo shrills here! I also built a separate Piezo bright box which is for use with effects. The Monacor mid range unit cuts off about 10 Kz, which is perfect for the Bass because it cuts out all unwanted hiss. Bass doesn't really generate much over 8 Khz anyway.

I used "Speaker box Lite 1.0 to simulate the enclosure which is shareware and I really recommend it, even though I didn't use it properly!

 

Cab 1 Construction

The Driver is a very efficient unit so it doesn't need a lot of driving to be loud (a 15" Eminence Kappa, 103db/w/m and is 8 Ohms, 400w RMS). The down side to this enclosure is it has a +6db boom around 90-150Hz, which take out using my 7 band graphic EQ on my Trace Elliot head. It's because the driver is in a box which is too small. I have yet to see a 15" enclosure which is in a correct sized box. Nearly all that I have tried are in tiny unsuitable enclosures which just heap on the 100Hz boom. I guess it's what we call the 15" sound. I don't particularly like it because at stage sound levels, the tone gets very mushy and dominating. I suspect that "great 15 warm tone" which we read about is in fact caused by this very reason and isn't a 15" tone at all, but just frequency curve distortion caused by the driver being in too small a box. Let's face it most 15" drivers require big big boxes, how many combo's or cabs have you seen which are 2m high?

I built the enclosure using 15m/m chipboard which is a lot lighter than MDF and is nearly as good. I used simple butt joints at the corners which I glued, screwed and sealed with "No-Nails". I rounded over the external edges with a ½" router bit and covered the outside with some green flock material which I purchased from Adam Hall (they supply Trace Elliot, Ashdown, Marshall, Ampeg, Bag End etc). I fitted 4 big rubber feet to the botom, top and sides and I fitted two straps on the top. I then fitted a flush metal handle on each side. I found some nice chrome corner protectors (just like Trace Elliot!) and I fitted a pair of locking jacks on the back panel. One jack is a typical Neutrick Locking 1/4" socket, the other is a cool XLR and 1/4" combi jack. I used good quality OFC cable to hook up the drivers which I took from a top quality guitar lead! I also fitted a nice big black 16" speaker grill to the front which is useful when my kids are about who just love to poke in the dust covers.

I also sloped the rear of the box so that it would fit in the back of my car, one of the finer things about the DIY route is that I can tailor the cab so that it fits in my car. I just hope I don't change my car!

Costs

I built this cab in September 1998 so the prices have probably gone up. All prices inclued all UK VAT and any postage charges.

1x Eminence Kappa 15" £ 57.50

1x Monacor 2" Soft Dome mid range £12.75

Eminence 400w 1K6 2 way crossover £22.85

Green Tolex covering 3m £24.50

Corners, Grill, Rubber Feet, Handles,Conectors and Internal Wire £60ish

Chipboard, Screws, Glue, No-Nails and Wadding £32

Total Costs: £209.60 (not bad for a 400w RMS cab)