Justblairs Audio and Electronic's Pages

Brendon Lee made a set of these Hammer Dynamics Super 12 loudspeakers for himself.  You may be more used to seeing loudspeakers with multiple drivers per cabinet.  There is a good reason for this.  Most speaker drivers are good at reproducing a certain part of the sound spectrum.  Generally speaking the smaller the speaker cone, the better the speaker driver is at producing high frequencies, The larger the cone, the better at low frequencies.(i.e. bass).

This is not the whole story, and indeed using multiple speaker drivers carries with it its own problems.  One such problem is matching the sound of multiple drivers to get a consistent sound (volume wise and also tone wise) across the frequency range.  Other issues arise in the electronics that filter the signal to each speaker.

Another solution then is to find a single speaker driver that is capable of reproducing the full range of audible frequencies (at least with the assistance of a cabinet).  This is the principle of a full range loudspeaker.  Brendon’s Hammer Dynamics 12 Full Range speaker does use a super tweeter to help at the very top end.  Here is what he thought of the Hammer Kit.

This article has been republished with Brendon Lees kind permission, previously being homed at Brendon’s Geocities hosted site.

The 3/4" MDF sheets were already Rimu veneered. Edges were angled cut to join nice and even.

The corners are edge mitred and routered so the back baffle board is recessed in.

Proper Tee-Nuts hammered in

The front baffle board is also routered so the woofer will fit nice and flush.

Rear binding posts where the wires are screwed on - allows for easy removal of the rear baffle board.

Speaker binding posts used. I do not like the idea of the hanging speaker wires that run straight to the amp and the exiting hole being silicone to seal - just looks too kacky.

How do they sound? Well, not every project that I've worked on has become a success. Quite frankly, the speakers don't sound that good to my ears. To give you an idea, the 12" drivers basically sound like a 12" driver playing mid-range frequencies. So vocals can sound a bit heavy ended (bass/boxy). An exaggerated comparison is to imagine Mariah Carey's voice sound a bit like Isaac Hayes (Chef from South Park).

So why did I buy the kit?

1. High efficiency (97db 1w/1m)
2. Low ZMax figure - since these speakers were designed for tube amplification, that means the speaker would have a reasonably low ZMax figure to match power amplifiers with low damping factors. My SoZ amp has very low damping figure which makes driving large size woofers more challenging.
3. To find out what real full-range speakers sound like.
   Currently in the process of breaking them in (I've been told 200+ hours @ 107db SPL) but, I honestly don't think it would make enough difference to make them for use as main speakers. They'll serve well as HT rear surround speakers for the mean time.

I've been criticized that the changes I've done in this speaker project is the core reason why the speaker doesn't sound good. Personally, the modifications I've done does not seem exotic enough to warrant such a big change in sound quality.

The height of the cabinet is slightly smaller than the dimensions outlined in the construction manual. The height had to be shorter because you can't find a perfect 4 x 8 foot sheet of MDF in New Zealand (i.e.. metric system). So what I did was made the side panels wider - thus making up for any loss in air space inside. There's nothing trivial with this speaker enclosure as it uses a ported bass reflex system.

I've been told that mounting the crossover to the front baffle board can affected the resonant sound of the enclosure. I will try in the near future but do not believe it will make a world of difference.

For internal speaker wiring, I did not use the expensive silver speaker wire recommended in the construction manual.

Simply because I can't buy it here and instead, used a mix of Cat-5e wiring and 12 awg multi-strand speaker wire.

On the positive note, the speakers do sound good with classical music. But 90% of my music I listen to is NOT classical - so I'm forced to look for another speaker project - possibly a pair of 4 Pi speakers.

My HHB CD player, SoZ amp, Balanced Line Stage pre-amp, ALL sound incredible on other speaker setups so it's not my other gear that is causing the bad sound.

UPDATE - HD Super 12 modifications are COMPLETE

New Modifications that made a WORLD of difference

From an e-mail correspondent, I purchased the Alpha Core Copper Foil inductors and the expensive 30awg silver wire from Digikey. The internal speaker wiring was done with 4 runs per side for the tweeter and 12 runs per side going to the 12" woofer.

These are Alpha Core's "Copper Foil" inductors.
0.65mH 12awg
0.30mH 14awg
0.24mH 14awg

New crossover - rewired and mounted on the rear baffle board. The crossover was originally mounted on the front baffle board but was suggested to mount them on the rear.

Comments:

Sound wise, the 1st few minute of playing I knew the sound had improved GREATLY. Could it be the copper foil inductors or the small silver wire? Either way, the modification was a world of difference in sound. No more Mariah Carey -> Barry White sounds, the crisp highs are there where they're suppose to be and the mid-bass has cleaned up to the point where you would not think clean vocals could come out of 12" woofers.