Mike's MTM - Initial Listen!

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Remember, this is an MTM bass reflex of about 40 litres using Seas ER18RNX woofers and 27TDFC tweeters, with bass tuning and crossover details worked out by simulation and with a lot of great help here, especially from Jay. The simulations took account of the high output impedance of my 300B SET valve amp.

Yesterday I finished the boxes and put the drivers into one of them and fired it up. Didn't know what to expect from this unique speaker. I knew it would sound, at best, 'not run in', and more likely it would need tweaking (as per Jay's advice on his web site) to get a good sound. If it was good enough to be listenable while running in, that's the best I hoped for.

OK, as the builder I am biased.
My first impressions of a new bit of DIY kit can miss out the odd problem (so I listened again today before posting).
I am poor at comparing hifi components in A/B testing (I know why and will explain if anyone is interested).
I am poor at 'standard' hifi auditioning tests (I have friends who are good at this) .... I tend to listen to music!
I've only had one speaker working so can't comment on imaging etc.
I reserve the right to change my opinion later in the cold light of day ....

Even with all this ..... the speaker is sounding good and showing a lot of promise. First off, it sounded like a half run in speaker, a touch rough. But the frequency balance seemed pretty good - nothing was standing out as wrong about it. The first CD on was Ruthie Henshall, Pilgrim; well recorded and she has a voice.
Anyway, though not perfect, she was *singing* and to me, that's very good news on a new speaker.
Then (while I worked on the second speaker), on went Mozart wind music which sounded good.

I was running one old and one new speaker and comparing using the dual mono volume controls. The overriding impression was just how alike the two sounded. But the new ones were sounding better. More clarity. Bass was good, seemed as deep and tuneful as the bass of the TLs, but had more 'snap' to it. Anyway, whatever the reason, the bass seemed better.

When the 3rd CD went on, things had improved. It was a folk CD by Mike Tickell (Kathryn's father), and I just though 'this sounds good' (I'd never played it before), and stopped all analyzing and simply listened for pleasure. Very, very good male vocals, sounded excellent.

By then I'd found out what I needed to know, which was what to do with the speakers. Choice of chopping them up for firewood and selling the drivers; leaving them unfinished, going back to the drawing board for a drastic rethink; leaving them unfinished while running them in out in the garage and trying to tweak them to get them listenable; or finishing them right away so as to get them properly installed in the house, run them in just as they are and then do some careful tweaking. Needless to say it's the last opion. So I didn't put the drivers in the second speaker.

This morning I wanted a 'sanity check'; was it all self delusion? Also I fancied trying some more music.
On went Hollie Smith, Light from a Distant Shore. Great CD, go buy it! This has some attack and drama, and yes it was there, sounded fine, bass good - not slow or wooly, it sounded good (and I've heard some *bad* BR bass in my time). Her vocals sounded fine.
Then Kathryn Williams, Old Low Light. This has a lot of plucked string bass and that sounded fine.
After a couple of tracks of those, on went Arianna Savall, Bella Terra; lovely voice, sung in Spanish (I think) with harp accompaniment. Well I did compare the two speakers, preferred the new one and simply sat back and listened for pure pleasure; magic!
Then, Nicola Hitchcock, A Bowl of Chalk; I'd say folkish gentle rock/pop, attractive breathy voice. This did sound nice, overall better than the old speakers (more clarity, better bass), but a touch of something may have been missing from the voice. This may give me a clue as to what frequency range to try to tweak up later; or more likely, whatever might be missing may simply appear by magic after running in - I've had that happen in a big way 3 times with DIY valve gear.

While I might end up tweaking the bass by port tuning, I simply cannot hear anything *wrong* with the bass, and that's a good result.
I will try many tweaks to the crossover - they are on breadboards with key components connected by terminal strips, so tweaking is easy. I expect to get a modest but useful improvement, but even if I don't ..... I think this crossover, designed specifically for my amp, may already be better than a perfect one optimised for transistors, if you see what I mean.
I know there's more to come, but it's highly listenable already!

So I'll be busy veneering for a week or two; more news later. Attached (I hope) is a photo of the old and new speakers; the new one looks larger as it's nearer the camera.

Thanks for the great help!
Crossover Details

On the woofers: 1.4mH and 25 uF, with a sort of zobel of 18 ohms and 22uF - this seemed to bring bsc in OK in the simulation. I'll play with that later.

On the tweeter: 3.3 ohm series R; 10uF and 0.4mH. I will play with the cap value and series R later.
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