BillFitzmaurice.info

Hi folks

I started a thread elsewhere on Bill's forum to determine the best sub(s) for my application. That decision has been made...and I'm now embarking on the THT LP model.

http://billfitzmaurice.info/forum/viewt ... =5&t=17585

The application is to augment my two-channel audio set up, comprising lovely 2A3 Push Pull valve amp from Australian amp guru, Earle Weston. See his site here.

http://www.westonacoustics.com/

I'm running a puny DVD player as transport to a mid-spec DAC (DIYEDEN). Silver cables throughout, including the co-ax.

Speakers are built by me, using the two-way Bob Crites 'Cornscala' design...which is a hybrid of the Klipsch Cornwall and La Scala models. The driver is Faital Pro 1.4 inch, running from approx 600Hz all the way up. The bass is handles by Crites' tweaked Eminence 15 inch woofers, which do a good job of running into the high 30's.

http://www.critesspeakers.com/cornscala-style-d.html

So, I want to bolster the bass, from mid 20's to around 50Hz.

The THT seems like the perfect vehicle to do this.

I've chosen the low profile version as this will be wall mounted, then covered with a large decorative veneered ply panel, which will be opened at the bottom to accommodate the horn mouth.

See pics of my listening position...plus a drawing of the layout.

Here is my amp and the 'Klipsch' Cornscala two-way speakers.

I have the horn mounted outside of the cabinet to test the height. I'm working through some different horns to try...and will probably go with a wood turned horn, 500Hz (approx 45cm diameter mouth).

The speakers cabs have been heavily braced, and sit on spikes, on a concrete pad, which is also spiked to the slab of the house.

Bought some very sturdy 18mm 'form' ply today from the local hardware. Seven layer ply, void free....very heavy.

Marking up the drawing was tricky, as the ply had a shiny dark coating.

I'm opting to build this by pre drilling holes to secure each panel.

My measurements are 72 inches long x 18 inches wide x 19 inches deep. The smaller cabinet will be aided by how I mount it to the wall, and build the large wood panel over it....loading up the corner/mouth.

Amp bought.

O-Audio 300 watt BASH.

http://www.oaudio.com/300W_SUBAMP.html

Nominated driver is the 12-inch SP Acoustics.

http://www.sbacoustics.com/index.php/do ... /view/319/

19Hz Fs, with 90dB efficiency.

I sincerely hope you removed that shiny layer before trying to glue it...

Atilsley wrote:Bought some very sturdy 18mm 'form' ply today from the local hardware. Seven layer ply, void free....very heavy.

Marking up the drawing was tricky, as the ply had a shiny dark coating.

I'm opting to build this by pre drilling holes to secure each panel.

My measurements are 72 inches long x 18 inches wide x 19 inches deep. The smaller cabinet will be aided by how I mount it to the wall, and build the large wood panel over it....loading up the corner/mouth.

Why on earth did you buy this ply? The plans call for 5-7 layer regular 12mm ply which is perfect when well braced.. PL wont bond properly to the coating on this ply so you'll probably have a hell of a time with leaks or even gluing it together.. You need to use epoxy to glue a coating like that, but thats almost impossible to get leakfree.

In my opinion, go back to square one, buy the recommended ply and start over if you want a good result. Also - why make the cab so much heavier than it needs to be?

+1

'thanks'

The ply was priced favorably....and I've built many horns before...tannoy, altec, lowther, tapped subs and more. I've alway found the extra weight/thickness helps. However, I'm not taking anything away from bill's excellent design. The weight doesn't bother me as this build is a one-off install only.

I will assess the adhesion....but at this stage, it's drying well.

Do you have a comment re the amp, eg RCA input vs speaker...?

Kind regards

Michael Ewald Hansen wrote: Why on earth did you buy this ply? The plans call for 5-7 layer regular 12mm ply which is perfect when well braced.. PL wont bond properly to the coating on this ply

+1,000,000
Form plywood phenolic surface film is very resistant to the effects of concrete ingredients and moisture penetration. PL relies on penetrating the wood and moisture for proper adhesion.

Rule #1: Follow the Plans
Rule #2: Never Break Rule #1

If I can confidently confirm/test the adhesion/expansion, am I back on track?

Real deal PL bond will break out the ply on a rightangle butt joint.

Atilsley wrote:If I can confidently confirm/test the adhesion/expansion, am I back on track?

No you are way off track. See Bill's post:

Bill Fitzmaurice wrote:Rule #1: Follow the Plans
Rule #2: Never Break Rule #1

I'm surpirsed a few smilies aren't thrown my way...!

Atilsley wrote:I'm surpirsed a few smilies aren't thrown my way...!

When the suggested building material is mentioned on page 1 line 6, people tend to be less indulgent

In all seriousness - be glad that you got a wake-up call now.. It would have sucked to be finished with the cab and have a million leaks and a less than robust cab.. Go buy Arauco/Radiata Pine or something similar with atleast 5 plies - its great and won't disappoint you... Neither will the design