'LGT' Construction Diary

[ShinOBIWAN]

Originally posted by pinkmouse


I suspect you'll be using that compound mitre spreadsheet we put together quite frequently.

Al

Can you post that again please? Note sure where my copy has gone

[ShinOBIWAN]

Originally posted by tinitus
[B]Hi, good to see you back in the right spirit

Impressive project, and one thing I know for sure; you will get it done

Hi again Tinitus, thanks for the nod and good to be back.

I hope you make a simple bass box test

I'll try, promise!

[richie00boy]

Just come across this thread. Looks like another great project in the making. Shame I didn't get to pay you a visit over xmas-new year. Maybe next time I'm up north I'll make it.

[ShinOBIWAN]

Thanks and your always welcome Rich if your in the area.

I really haven't made the effort myself yet either. New years resolution: jump in the car and go visit Al, Rich or Vik later this year.

[pinkmouse]

Originally posted by ShinOBIWAN
Can you post that again please? Note sure where my copy has gone

Here you go.

You know, we really ought to organise a diyAudio UK branch meeting at some point. Do you still have access to that hall Tony?

[ShinOBIWAN]

Originally posted by pinkmouse


Here you go.

You know, we really ought to organise a diyAudio UK branch meeting at some point. Do you still have access to that hall Tony?

Aha! There it is. Believe it or not I searched that thread for just that link you posted. In the end I thought I'd imagined the whole thing.

Still have access to the hall, maybe in the summer if folks can make it. I'm also happy to travel upto about 3 or 4 hours each way.

[pinkmouse]

Originally posted by ShinOBIWAN
Still have access to the hall, maybe in the summer if folks can make it. I'm also happy to travel up to about 3 or 4 hours each way.

I will start a new thread for expressions of interest, let's see if this thing has legs. We can always pin down exact location later if we have enough kit and willing victims.

edit: new thread here!

[ShinOBIWAN]

Redesign time. I've been looking at Mark K's Scanspeak 12M midrange tests and I've got to say that they're disappointing, I was hoping to cross at around 200-300hz but even at 400hz these would be struggling. I was also chanced upon a guy from the Netherlands who said he didn't rate them and said they have a particular character that's pleasing but not neutral. I've also heard this from Troels about the 18W sliced paper and I've used that one before but never really thought it was any other than a good driver.

So looking back I decided to stick with a driver that looks interesting and that's the Accuton C90-T6 midrange. This driver looks perfect to 200hz with good extended FR to well over 2 octaves past my intended upper XO point. The only problem is MTM configuration and the larger 6.5" Accutons, I'll gladly take a knock here and no its not the end of the world though but having said that maybe a 3.5way but thats not something I want to consider until really needed.
I wanted to keep the same form factor and had to juggle the design a bit to squeeze in the Accutons. The overall width of the cabinet has clearly increased by a good amount and so has the height. My goal of reasonably small size is now lost and I'm going to have to live with that too. The upshot is that the 8" Seas Excel drivers will be replaced by 12" pro-drivers (yay!) that will provide a big increase in bass performance. I was thinking along the lines of the 12" Beyma LX60 or maybe the excellent B&C 12TBX100 which I loved for its massive dynamics in the 35hz and up range.

Overall the design will benefit in that I'll be looking at atleast 93dB efficiency and more likely 95dB which would really suit 50w class A amps for the mid and treble. The overall dynamic range should be pretty fierce in comparison to the other. Its a more rounded design.

Here's the redone version. Just a bit of FYI: the drawing was completely done by hand, no fancy 3d rendering here and to think I got a G grade in Design and Technology at School, though TBH I was much more interested in other less academic activities at that time.



If size turns out to be a real issue a cut down version could be made whereby the top bass section is omitted. It could always be added later when room allows. Personally I think I'd want the big version though because the foot print is the same and vertical space is less of an issue.

[tinitus]

Hi, carefull with those new Accuton mids, I have been told that shown measurements are not from Accuton, and in reallity they measure bloddy awfull - high efficiency often has a price

[ShinOBIWAN]

Originally posted by tinitus
Hi, carefull with those new Accuton mids, I have been told that shown measurements are not from Accuton, and in reallity they measure bloddy awfull

The data I have is straight from Accuton, I couldn't find the driver on their website so emailed them and they provided a datasheet with detailed measurements. I'm not sure what other measurements your refering to but these are definitely Accuton originated.

I've also been in touch with Tony Gee who is currently using the C90-T6 mids in a project he's working on. He used the word 'amazing' which says a bit considering all the drivers and designs he's been through.
There's also the Evolution Acoustic MM3 commercial speakers that were recently introduced and use the C90-T6's. Mike Lavigne who previously used the Von Schweikert VR9 and Karma Exquisite Midi with diamond tweets said the MM3's were one of the best he's owned.

Hard to believe that the driver measures awful from the research I've done. At this point its hearsay for me because until I get a driver, test it and get it in a working loudspeaker system then its impossible to do anything else.