'Perceive' Contruction Diary

[ShinOBIWAN]

Originally posted by george a
Hi Sinobiwan

Nice Works.
If your body filler and Mdf are like we have hear in Oz, be careful about difeerent expansion rates for both at joins or filled screw holes etc.

We usually find the mdf shrinks compared to the filler and becomes quite visible even after spraying.....
Cheers


ps: should you consider a groove or "control joint" where the two materials are meeting in the same plane...

Oh yes, I'm sure they are quiet the same.

I've grown acustom to MDF's penchant for joint expansion and tend to use workarounds to hide or minimise the problem. Chamfered edges is one way to get rid of the ugly expansion since the joint is on the edge of the angle.
Another is large amounts of filler on layerer or translam constructions such as the front baffle. Its looks ugly when you have bare MDF but save you a considerable headache later on.

The absolute best way to avoid all problems though is to wrap the cabinets in a cheap veneer and then spray and finish onto this.

Still not decided on a veneered finish or just a spray job.

[ShinOBIWAN]

Originally posted by ScottG



definitly parallel.. voltage amp + 2 drivers in parallel = +6 db; voltage amp + 2 drivers in series = 0 db increase (..+3 db for doubling driver, -3 db for series connection = 0).

btw, its look'in reeeeel good.

Thanks Scott,

I'll go with parallel, my only concern was if the P101 would be happy with a 4 ohm load? By all accounts the Exicon mosfets look robust and current supply isn't a problem, so I can't see why not.

[ShinOBIWAN]

Couldn't resist connecting everything up into the virtually complete cabinet and having a go.

I wish I hadn't, somewhat disappointing performance for the outlay. I'm very picky and not easily impressed but here's my gripes:

Bass is poor, ill-defined and slow. Integration between the mid and bass is terrible, these sound like some £1000 Mission's in this regard, just not upto the task of hi-fidelity reproduction.

I suspect the reason for the frankly rubbish bass performance is the poor mid-bass integration.

All I've done is a basic level match of the drivers, no phase correction, no baffle step and no EQ/notch filters.

On the plus side the midrange and treble performance is out of this world. I'd highly doubt you could significantly better it for less than silly money.

I'm loathed to throw more money on drivers but did think of the AT range of 8" drivers. I'll work hard to better what I have in front of me now and hope that the design as whole comes together.

Really I need to run some extensive SW tests and then post the results here but I'm a strapped for time at the moment. If anyone has any thoughts please chime in.

Cheers all

[ShinOBIWAN]

Originally posted by ShinOBIWAN
...these sound like some £1000 Mission's in this regard, just not upto the task of hi-fidelity reproduction.

LOL

I actually meant £100 and not £1000!

Also crossover points are 3.1Khz & 350hz.

[jleaman]

LOOKS SO NICE!!! Super work. Keep it up.

[ShinOBIWAN]

Originally posted by jleaman
LOOKS SO NICE!!! Super work. Keep it up.

Thanks, your own speakers look great too. Love curved cabinets!

I'm kinda hesitant to post this here as I'll probably get laughed off the board but the reason for the poor bass integration could have been the fact that when I did the wiring on the bass drivers, I'd inadvertantly wired them both out of phase with regards to the mid and treble.

Sounds much, nay, infinitely better. Now very tight, well defined and the mid/bass integration is seemless.

I now ask myself, if I can't do a simple job such as wiring the drivers in phase, how on earth did the electronics I built work first time?!? Doesn't exactly instill confidence

Much reviewing and tweaking ahead methinks. I'm a little too excited to post subjectively about the sound at the moment, so I'll restrain myself and say they sound good for now.

[m0cea]

A quick run through with true RTA should show up some of the problems.

Also you won't get the best until you have the pair running.

[ShinOBIWAN]

Originally posted by m0cea
A quick run through with true RTA should show up some of the problems.

Also you won't get the best until you have the pair running.

No mic at the moment, so RTA is out. Though this won't do and I'll be sorting one very shortly.

All I've gone on so far is an SW Walin jig 2, measuring driver parameters and such.

I also agree that one speaker doesn't cut it for serious testing but it does give me an idea of the tonal quality.

[David Gatti]

That's funny - I did a similar thing. Wired one of my mids out of phase the first time, and things just didn't gel. Now I battery test all my woofers & mids after they're mounted.

[m0cea]

I could nip along in the morning with the kit if you like?
I'd be interested in seeing the project in the flesh.