TLAH PRO (mongrel) build.

[slavedave]

Hi BFM'ers,
At last I have got around to starting to build a single TLAH Pro to use at our worship services on a Sunday morning. Inspired by all the previous builders on here I thought I would have a go at one to replace our existing Bose L1 clone and a T18 sub which has served us well for the last number of years.
I am using these drivers:
Peerless 8 inch woofers SK0204 8 ohm from Willys Hifi on Ebay.co.uk
and these piezos:
PULSE - PLS00305 - TWEETER, PIEZO HORN, 110X110MM from CPCFarnell

It all came down to budget in the end - I just couldn't source the listed drivers for the right amount of money so I recognise the compromises made in this selection (sorry Bill!). Thankfully the woofers have a track record thanks to chenry78 - see his build here c/w video.

Using 15mm Baltic Birch for the carcass. I am hoping to mount them on a low-rider stand using a tophat in the base - but I think that this may end up being folly - we shall see. I also hope to make a front screen for it using speaker cloth attached to a frame. This will be attached to the baffle using small but strong neo magnets inset into the baffle and frame.
The speaker will be set up and taken down each week since we rent a gymnasium for our services, so I am also going to have to fashion together some sort of protector cloth case for it to be stored away in. Any ideas for padded material to use?
Links to photos are here (and I will add to them as and when I get time to work on the build). Please feel free to analyse them and comment on where I have gone wrong - ot would be good to get feedback before I start mounting drivers and baffles etc.
http://s1221.photobucket.com/user/slave ... pro%20-BFM

Learnings so far :
1. Practicing routing with my make shift template was essential - I could have made costly mistakes on the baffle if I hadn't tried test cuts on scrap plywood before.
2. Even though I got the piezos for less than 50p a pop, cutting them down with a hacksaw took a relatively long time. My arms are letting me know they have been used!
3. Standard plumbers pvc cement is brilliant (but nasty) stuff. Mixed with the swarf from piezo cutting makes an amazing glueing substrate.
4. There was a fair difference in "tone" from the piezos when testing them (I didn't phase test them or run a sweep). I hooked them up to an amp and played white noise through them and tried to get 8 that had a similar frequency pitch. Several I tested had noticeably different tone about them. However, when all wired up and played through the same amp - they were LOUD so hopefully I have done something correct.
5. Duratex is amazing! I have used it on a T18, a rack box, some home audio speakers and now this cabinet. A small 5 litre pot has gone a long way.


Will update this thread as and when I get the chance.

[slavedave]

Fitted the top hat to the base plate with heavy duty screws and PL - then topped it off when dry with silicone caulk to make sure it doesn't leak (slightly off-set from centre to accomodate the extra weight of the woofer line - no science involved finding the centre of gravity etc. Just eyeballed it and biased the mounting toward the front baffle a bit).
Mounted the woofer line with screws onto a thin, black silicone bead to ensure airtight-ness.
Also screwed down the piezo array into it's slot - here was a problem. I pre-drilled screw holes but on one side of the array I had not left enough wood for a good purchase for two of the four screws on that side. This has meant that much of what holds this side of the array in place is purely silicone and I am not sure it is sufficient. I will remove the baffle and try to get some sort of clamping nut arrangement to clamp the array to the wood internally with machine screws. It is noticeable that the array rattles a bit a high volume levels.
Wired as per the plans, with the tweeter line wired via the crossover.
Screwed the baffle on. I noticed the relative flimsiness / flex of the baffle when loaded with all the drivers. I wouldn't want to move it too far without adequate support along it's length in this state. Once on the cabinet all was fine though. Screwed down the countersunk fixings to compress the weather seal.
Mounted the array on an old drum throne base - needs a little of tweaking to make it rock solid (it wobbles on the mount a degree or two). Otherwise, it is good to go.

Connected her up and ran some tracks through it using a small monobloc amp and my phone and... it makes sound!!! Huzzah!
In my small side room it goes plenty loud feeding it less than 100W. Then plugged in a drum machine and let it run at good volume for an hour - maybe helps break in the drivers? Don't know.
Then plugged my e-drum kit into it and had a blat with that for a while. Finally, I got my eldest daughter to mess around on the kit using synthesized bass sounds and kicks etc to check cab. Definite leak around one of the piezo joins to fix. Also, it became immediately apparent that the piezo array was rattling and the baffle was flexing considerably on deep bass kicks/tones. Checking the sketch-up plans highlighted a glaring omission on my part - bracing for the woofer line! Eek! Will add those as soon as I get some time on it.

Ordered speaker cloth (pricey) for the front, and a couple of corner mounted rubber wheels to go on the base for easier transporting each week (this thing is awkward to move around). Should be hear in a week.

I will try to get it out in the garden for a bit more of a play at the weekend if I can to see how it sounds. If I can get video I will, and if I can work out how to - I will download some RTA software and have a go at some analysis with my laptop, roland interface and my behringer reference mic too.

[biggerrigger]

Congrats on your build. Spend a little time measuring and EQ'ing and watch it come to life and put out some real sweet sound.

[slavedave]

Thanks biggerrigger.
It took a while to dial in the bose l1 clone with the DRPA but eventually we had respectable results. I will set this up next to it with a crude eq setting off the desk (bypassing the driverack altogether) to see how it compares. My aim with this build was to simplify our set up a little - I hope the TLAH will need less processing and, hopefully, I can dispense with the sub too (I cross at 100hz at the moment!) for most activities. With our Bose L1 clone we could not dispense with the sub if we wanted any music played through it that contained any bass material, but it is very good clarity for spoken word on it's own.
I hope not to have to use the driverack with the TLAH at all, dispensing with one stage in the audio chain. Then I will look to source a powered mixer to replace our mixer + amp set up, thus minimising the whole thing another step. Long term plan is to have a system that more people can be comfortable with running to free me up for some of my other responsibilities each week.
We will see how it goes.
Thanks again.

[slavedave]

Not much of an update but I did get the frame for the speaker cloth prepared yesterday. Rather than cutting / routing my spare bit of plywood from the original sheet into lengths to then mitre and join together, I decided (since the spare bit was exactly the same dimensions as the baffle) to rout it all in one piece. I rounded over the outside edges to help with aesthetics when the cloth arrives, then routed approx 12mm inside the piece to give me a perfectly sized outer frame (this was not as easy as I thought and the thickmess of the frame is far from uniform all the way around due to my lack of consistent routing skills). I then hand-sawed some thin strips to make strengthening and stiffening battens and PL'd them in place before Duratexing the lot. It is very lightweight so I shall wait to see what it is like when I come to staple / glue the cloth onto it. I will get a picture uploaded into the photobucket site at some point today.
At this stage, I am moving away from the idea of using nei magnets to mount the frame to the baffle - I think I will use some of my 3M "super" velcro instead. Any opinions on this approach?

[slavedave]

The new speaker had it's "pilot" run out this morning. I set up both systems (the existing one and the new TLAH Pro) next to each other in the pre-service prep time. The old system was prepared as per normal and I then sent an aux feed from the desk to a small monobloc amp ( approx 80-100 wpc at 8ohm) to power the TLAH. Ran the TLAH first and set up a rough mix using the auxes for each musician/vocalist - it took a bit of eq-ing at first to get something that I liked. The musicians were happy so I thought, blow it, let's go with it for the main event, so I dismantled the old system and then ran the mix from the main outs to the monobloc amp instead. Was able to get a decent mix fairly easily. One thing we all noticed was the "breadth / depth" of the sound with the new system - we could hear frequencies that were missing in the L1/T18 combo, which I assume were mid-bass frequencies. Acoustic guitar was quite difficult to dial in. Piano was great. Bodhran sounded really good. Vocals had loads of low end though, even when I backed off everything per channel. I then realised the monobloc had the "loudness" switch still engaged Once off, everything sounded so much better balanced. Considering we were not running a sub with it I was very happy with initial performance.
Next week I may run it through the Driverack and do some EQ-ing but overall it was a good first impression. Feedback from the congregation was "It is big!", "Cool", "Sounds great", "Too Loud" etc.
One thing that I was very aware of was that I was able to "place" the sound source much more easily than with our L1 clone - i.e. I could definitely identify that the speech and music was coming from the TLAH. With the L1 clone this was never apparent - the sound just seemed to be a magnification of the instruments and vocals.
I am sure we need to run it for a few weeks to see how to get the best out of it. I will keep you all updated as I make progress. But as I said above, first impressions are very favourable.

[biggerrigger]

Good job Dave! Sound like all went pretty well for its baptism by fire. You will find that your sound will change for the better when you get some more time on those drivers. They will loosen up and sound smoother possibly requiring another tweaking session on the EQ to get it dialed in. Make sure you post a review with pics when you get it all sorted.