Twelvebears Rock Monsters: Some fine tuning required.

[twelvebears]

As so many of you have shown so much support and interest in my mammoth speaker project, I thought I'd give you a bit of an update on progress since they arrived on Friday ahead of a full write-up in due course.

Delivery and installation went pretty smoothly, and apart from one soldering burn, one bruised knuckle, one pliers pinch and leaving one allen key in the bottom of one cabinet it wasn't a problem.

As you can imagine, since then I've been doing quite a bit of listening and they are sounding mostly awesome, notably in the following areas:

- speed
- imaging and depth of soundstage
- vivid, uncoloured mid-range
- ability to listen into complex mixes and pick out details

but as was almost inevitable for something so radically different to what I had before, there's some fine tuning to be done. Basically the treble, mid and upper bass is all good, but the lower bass needs some sorting out.

Essentially what has happened is that the damping panels, while excellent, are sufficiently dense to effectively take up a far more significant proportion of the internal volume than had been expected. This has affected the low bass response of the main driver, which in turn means that the bass port is tuned to too low a frequency.

In short, I have a bit of a hole in the lower bass response, then a dollop of rather detached VERY low bass which needs bringing up slightly to reinforce the natural roll-off of the main driver.

On some music with very little low bass, everything sounds fine, but with other material things sound a bit weird.

I just need to experiment with the final length of the bass port (current) through listening tests to get the final set-up right. The only thing that slightly complicates things is that the rear 7cm of the current 11cm port is a solid slate tube bonded to the back of the 4cm thick baffle. Fortunately John tells be that a sharp tap with a hammer should cleanly remove the tube without too many problems. I will then experiment with make-shift cardboard tubes until I get things right.

Well it was never going to be THAT easy was it....

[John]

Good luck wuth the fine tuning; gettingit right will be well worth the effort

[twelvebears]

I've had a very full and helpful reply from David Lyth at Volt, which suggests that I'll need to shorten the port from 11cm to about 8cm. He also suggests that a small amount of loose fill behind the main driver might be worth trying.

A job for the weekend I think.