Another Troels Gravesen's DTQWT Project Build

[BioBrian]

Hi Sierra,

Thanks for your praise of my remedial "draught"ing skills. As you said, pics can save a lot of words and mental Houdiniisms.

I think I'll still stand by the suggestion in the first sketch, as a follow-up from your Stainless Steel tube idea. It would look simple, strong, and elegant, and do away with the need for a metal frame thing, which I reckon would tempt vibration unless really thick. The solid bar would have to be pretty thick to avoid the anorexic look, but after seeing your last speaker stands, we'd better believe you when you say "solid"! With tube you could always fill them with lead! I have it all planned out in my head: use a vertical drill and small bit to go through the plinth, place plinth on upside-down speaker and drill through. Then use spade bit to do about 3mm into bottom of speaker, then top of plinth (small diam holes will ensure perfect alignment), cut 4 bits of tube, then drill holes bigger to fit 3" or so screw. Eg: I've just done some work in a cherry netting project here where a 35mm spade bit makes the right hole for the old 1" galv pipe. So easy in my head, so that's just more verbiage to the sketch to fill in a bit more cyberspace... Sorry to perturb, but it'll be all too late in a few days, or weeks...

And you asked about my project. Well I realized I didn't have any good pics, so the following looks a bit contrived, but shows where I'm up to. The back view will look the same as yours: they really aren't that different. The incomplete baffles are waiting for edges to be added: in one piece with 7 sides, or 2 pieces with at least a couple of square sides each. The 3" x 3" Celery Top pole is being auditioned for the job. The bend you see is not a lens artifact: it's real! I spent some painful hours today cutting out 4 pieces which in theory should be able to do the job, with no knots or major cracks; just a couple of borer holes, which could be filled, so at least they're not black. The timber is about 25 years old, and very fine-grained, so I wonder about reclaiming some more of it. Trouble is, it's holding up the house...

Oh and the pot plant is my obscure sense of humour at work: it's Thyme.

I had to spend some of the best energy of the day planting beetroots, beans, and lettuces. Far more important I suppose.

[Sierra]

Hey Bio_Brian ...

Don't worry I havent discounted your idea of coupling the plinth to the cabinet ... it's a definate option for sure.

I know exactly what you mean with using the spade bits making a small "recess" for the supports ... a nice idea too.

You're right ... when I say solid bar I don't mean 10 or 12mm like you get at Bunnings ... I mean proper bar stock ... 25 ~ 30mm thick

Does this mean you will be going this way for yours?

I don't think the spiked frame idea will have any problems with vibration ... if you remember Troels even mentions the low vibration levels ... as per his comments quoted here ...

"The DTQWT horn works quite different compared to a bass reflex enclosure and we do not need excessive panel thickness and I wish you could all experience how the e.g. side panels feel when I play bass even at thunderous levels. You won't feel much."

Your cabinets are looking great and progressing really well.

The baffle edges might be tedious work in getting the angles right.

Have you thought about how you are going to finish the exterior of your cabinets?

No word on my cabinets yet ... I imagine the finish might take a couple of weeks of curing time ... maybe I'll hear this week

[Sierra]

A slight update ...

I had a progress picture sms'd to me today.

The cabinets are comming along nicely with still more coats to be applied.

The lacquer has brought out the deep color of the Jarrah and is contrasting really nicely with the Tasmanian Oak

[BioBrian]

Looks fantastic, Sierra! Can't be long now??

I can't believe it, but my feet took about 3 days. I found some Epoxy spray that doesn't need primer, which I think is excellent: used it on a treatment table once. For the feet I used 50mm RHS, though when fitted they look much smaller. And black shoes with a wedding dress?? Not ecstatic, but maybe they'll be complimented by the black of the drivers, when fitted. One back foot on each cab is adjustable. I found some 1" fine-thread nuts, which are now welded inside the feet, and cut the bolts to have rounded ends (compromise for carpet, wood, and concrete floors), and flats ground so I can adjust with a 19mm spanner. Some pics:

You asked about the finish: I've decided to use water-based satin clear stuff from our local eco-paints place, TasPaints. It dries as you brush it on: can be sanded 20 mins later (in warm weather), and re-coated. There's a Sealer, then following coats are an Aliphatic (long-chain molecule) water-based polyurethane, which allows, in theory, the 3-4 coats to finish in one day. However, with this rotten weather lately, with low temps and floaty rain, it all takes a lot longer. I did the insides yesterday, as far up as I could reach, just to slow down reabsorption of moisture/swelling, and hope to finish the sanding today, and at least get the outsides sealed. I might need to patch up knocks later, so this system works well for me.

Internal wiring: I've been put off the supplied silver-coated copper, after such earnest debate and very disparaging remarks from some, so have ordered instead some 12 AWG OFC from HomeTheatreButler.com. This comany have responded incredibly quickly, posting 2 orders within hours, and at very reasonable prices. I didn't really want to spend $199 on (external) speaker cable, but this is 8 AWG, and I'm sure 50m will get used some time soon. $4/m can't be argued with. A local shop raving about $25/m decided me.

Not sure how I'll cope with real life after all this... Looking forward to your next good news.

[Sierra]

Thanks Brian ... I'm really happy with how the cabinets are looking.

The guy doing the finishing has a lot of work on at the moment so I'm not sure if they will get done before Christmas.

Nice work on your cabinet feet ... they look good and are nice and solid ... no problems taking the weight there.

Did you think fabricating something like that would be a quick job? ... LOL

It always takes longer than you think when you are trying to do a quality job on something that you have never made before.

Clever idea just having one foot that is adjustable ... it's all that's needed.

How is the finishing going?

Have you started on the external coats?

At this rate you'll have yours finished soon

Interesting comments about about the internal wiring ... I was having the same thoughts about using the supplied stuff too.

[BioBrian]

Just an update to tie up my loose ends - mine are up and running.

The finish is not perfect - very frustrating using clear. When able, I could open the rolladoor and use natural light, but still needed something bright on the floor, so every brushstroke could be seen in its reflection; too much sun, or wind, meant the door had to come down.

I just can't bring myself to keep putting on layers, then cut back for a perfect polish, as it looks OK from all but a foot away. The birch/myrtle/celerytop worked well, especially the birch, with some of its grain having lovely silvery reflections.

The final weight of my DTQWT-12 is 80kg each: 39 at the top edge, and 41 at the bottom, presumably due to the crossovers. Good thing I went for HD footwear...

Now just waiting for the Anderson connectors to burn-in!

[Sierra]

Looking great Brian

Damn they are a big, imposing speaker when you see them finally built.

Shame you're not 100% happy with the finish ... is it something that will bug you or can you live with it?

Now the big question ... first impressions ... how do they sound?

I know it's too early for a critical listen ... you'll need a 100 ~ 200 hours on them first

[Sierra]

A little update ...

I had the binding post mounting plates engraved ... I think it just finishes it off nicely I think

No more news from the polishers about the cabinets ... so looks like it will be next year before I get them back.

In the mean time I'll work on the crossovers over the Christmas break.

[BioBrian]

I really like that: very pro, and not overstated. The font, especially on the bottom part, is just right. What do you call it, and who do you go to for that kind of work? Obviously not done by hand. Will look great with the gold.

Yesterday, I tried to post an answer to your Q about sound results, but it wouldn't post. Maybe nothing works after you've made a 'copy', and it wouldn't accept me 'pasting' it back in. Will have to try some other time.

I think it's terrible you've been left in the lurch like this! Hopefully he'll have a nice xmas surprise for you...

[SteveLuck]

Thats a very neat final touch - can i aks how much you where charged for that?

I'd love to do something similar for my Carfrae horns after all the effort put in so far.

Cheers

Steve

[Sierra]

I really like that: very pro, and not overstated. The font, especially on the bottom part, is just right. What do you call it, and who do you go to for that kind of work? Obviously not done by hand. Will look great with the gold.

Yesterday, I tried to post an answer to your Q about sound results, but it wouldn't post. Maybe nothing works after you've made a 'copy', and it wouldn't accept me 'pasting' it back in. Will have to try some other time.

I think it's terrible you've been left in the lurch like this! Hopefully he'll have a nice xmas surprise for you...

Thanks Brian

The font is the same for both top and bottom ... the top is done in what they call "outline".

I had a company called "Industrial Engravers Australia" in Dandenong do the work and it was done via laser etching.

I don't remember the name of the font ... they had a font book that was nearly an inch thick ... there were thousands upon thousands of fonts available and I had to quickly choose one ... I know it started with the letter M and it had a wierd name ... and it's not a font found in MS Office.

Strange that you had problems "pasting" text into a post. I often write something out in MS Word then copy and paste into here ...

Did you try the "universal fix" reboot your PC/Laptop and try again?

Well I did have some great Christmas news this afternoon ... my cabinet maker SMS'd me this afternoon telling me he was picking up my cabinets from the polishers this afternoon ... so I'm off to Ballarat in the morning to pick them up from him

Thats a very neat final touch - can i aks how much you where charged for that?

I'd love to do something similar for my Carfrae horns after all the effort put in so far.

Cheers

Steve

Hey Steve ... love the workmanship on your horns ... they look sensational.

The engraving was fairly cheap ... cost me $49.50

[Sierra]

A little update ...

I picked up the cabinets from my cabinet maker friend yesterday ... Huge thanks to you Brian for an awesome job ... they have turned out even better than I had imagined.

This is the Jarrah base that I had made up as well to give me some additional options on how to achieve the 40mm horn vent height.

Still undecided if I will use it or not.

Well ... I couldn't help myself.

I did a Lebowski and bought myself a pair of Usher S520's in piano black from Trevor Lees last month.

For the price these things have been going for lately and the rave reviews they have been getting I just couldn't resist and had to grab a pair

Looks like I've got a little bit more work to do though ... I did a trial fit of the wave guide and the midrange driver ... and they no longer fit.

We obviously made the cutouts too precise as they were a snug fit when we made them many weeks ago.

The timber has shrunk along the horizontal axis by 1mm compared to the vertical which is still the correct dimension.

So I'll have to do some delicate sanding work to get them to fit again.

I also trial fitted the 10" drivers on the rear baffle and they still fitted fine.

Murphys Law at work ... the rear drivers that are not on display are fine ... and the fronts that will be the focus of attention I have to rework ...

Doh!

[cangaceiro99]

Looks like I've got a little bit more work to do though ... I did a trial fit of the wave guide and the midrange driver ... and they no longer fit.

We obviously made the cutouts too precise as they were a snug fit when we made them many weeks ago.

The timber has shrunk along the horizontal axis by 1mm compared to the vertical which is still the correct dimension.

So I'll have to do some delicate sanding work to get them to fit again.

I also trial fitted the 10" drivers on the rear baffle and they still fitted fine.

Murphys Law at work ... the rear drivers that are not on display are fine ... and the fronts that will be the focus of attention I have to rework ...

Doh!

Similar thing happened to me. I've had some baltic birch ply CNC'd for DTQWT and all cuts and rebates are perfect except for the front drivers. I haven't tried fitting drivers yet, but the splintering is pretty bad, whereas for the rear rebate holes, no splintering at all. I might try flipping the boards around and redo the rebate holes on the non-rebated side.

Sierra & Biobrian, both your speaker cabinets look amazing by the way.

[SteveLuck]

Wow the wood looks stunning and the plinth works well too. Great piece of furniture that most people would be more than happy to have in their house.

Re the hole fit i guess you'll have to knock up something you can bolt in to hold a router circle jig and re route the edge very carefully. With all the laquer on it it should be OK for a light trim fingers crossed you'll just get a bit of light fuzz on the edges that can be cleaned up and touched up. One of those jobs that will take a while to set up carefully and seconds to do. - I contemplating whether to do the same on my Lowthers to counter sink them. I'd have to route 5 circles for each speaker a center andfour more for the tabs.

Happy Xmas you'll enjoy the fruits of your labour pretty soon. - I look forward to a report on how they sound.

[Sierra]

Similar thing happened to me. I've had some baltic birch ply CNC'd for DTQWT and all cuts and rebates are perfect except for the front drivers. I haven't tried fitting drivers yet, but the splintering is pretty bad, whereas for the rear rebate holes, no splintering at all. I might try flipping the boards around and redo the rebate holes on the non-rebated side.

Sierra & Biobrian, both your speaker cabinets look amazing by the way.

Thanks for the kind words cangaceiro99

Sounds like there are a few of us building these at the moment.

I've heard that baltic birch can be a bit difficult to work with due to the splintering.

Typical though ... the front baffle that you want to come out perfect is the one that gives problems ...

I would probably be scrapping the front baffle and redoing it ... flipping it over and rebating from the other side will mean you have a reduction in thickness and you may run into other problems with bolting/screwing and a general lack of rigidity.

Wow the wood looks stunning and the plinth works well too. Great piece of furniture that most people would be more than happy to have in their house.

Re the hole fit i guess you'll have to knock up something you can bolt in to hold a router circle jig and re route the edge very carefully. With all the laquer on it it should be OK for a light trim fingers crossed you'll just get a bit of light fuzz on the edges that can be cleaned up and touched up. One of those jobs that will take a while to set up carefully and seconds to do. - I contemplating whether to do the same on my Lowthers to counter sink them. I'd have to route 5 circles for each speaker a center andfour more for the tabs.

Happy Xmas you'll enjoy the fruits of your labour pretty soon. - I look forward to a report on how they sound. itself

Thats exactly what I was after Steve ... a nice piece of furniture

Problem is that I don't have a router so I cant re-do the holes.

What I'm thinking of is doing some delicate sanding work with a little dremmel cylindical sanding tool connected to my cordless drill.

If the drill doesnt have the speed to do the job I might have to buy myself a dremmel.

As you mention ... the lacquer on the edges is what I'm scared of damaging or splintering ... was thinking of using some light adhesive masking tape around the edge to to protect the the lacquer while I sand.

A bit more work to do before I have music playing ... but we are getting closer.

Enjoy your fruits of your labour

[BioBrian]

Very relieved that you got them back Sierra!

I had a similar problem: all were a pretty snug fit before painting, and I was really pleased, but after...

I worry about the dremel idea. I struggled to find something of almost the same diameter, so I could hold sandpaper around and not make uneven gouges. Maybe 120 to 150 grit would be appropriate. Have you noticed that almost all round objects like jars and cans have either a round edge or a lip? Eventually found a plumbing fitting about the size of sewer pipe, with a nice sharp edge, and spent a a lot of care placing it on the bed of the routed rebate to keep the vertical wall square. So lots of holding sandpaper around the 'pipe', working side to side. I had to cut off the edge of the paper a dozen or so times, but didn't actually get back to bare wood before they fitted: it was just the paint. Not as painful as I'd thought, and so nice to have it snug, unlike some in the past. It might not be as bad as you think!

Your colours look even more stunning now, and the plinths balance it well. Hope you get some great enjoyment with the final phase.

cangaceiro99: thanks for your complement. I routed all panel edges to avoid the B Birch splintering problem, except one little shortcut with a circular saw on the rear baffle tops: damn! Couldn't afford to lose any more length, so it stays imperfect... Also I used epoxy glue throughout, which makes all faults darker, but at least it feels like all gaps are filled.

[Sierra]

Hey B-Brian ...

Well I've learned one thing ... if there is ever a next time of building speakers ... driver holes and rebates will have clearance around them.

I like your suggestion of a large diameter object to wrap the sand paper around ... I have a piece of spouting down pipe that I can use.

That in combination with the dremmel should to the job ... but it will be slow and painstaking ... I cant afford to rush this and make a mistake ...

Yes the rich color of the Jarrah has really come out with the laquering

So ... don't keep us in suspense ... how do yours sound?

[BioBrian]

Yes, I've noticed others going a bit quiet when they've finished. It's a very different world, stepping out of the obsession and exhaustion of the build, to quiet sitting, going through all the 'old fave' test CDs.

Initially, the sound was pretty hard and plastic, like pushing through layers of varnish and glue. Within 20 minutes the mids and tweeters had kind of melted a bit, and were showing much more warmth. After a few days of occasional heavy duty work, like the Notre Dame organ on SACD etc, the woofers are not showing much sign of loosening: they are a very stiff speaker, with a 250W rating, and it still confuses me about how they can match the sensitivity of the front drivers. I suppose if they did move a lot, they'd blow out the front woofer, as they connect to the same air space.

Using TDK's demo CD 'slow frequency sweep', there is slightly disappointing low bass (as yet), too much mid-bass, and a few minor lumps/shouty bits further up. But having tried this over a week or two now, some of the resonances change, odd ones turning out to be bits and pieces in the workshop! Opening the Rolladoor behind changes that mid-bass thing a lot too.

With music, they are a dream come true. Really complex, loud scores, like the end of Prokofiev's 5th Symphony, are incredibly clear and detailed, and speaking as an ex-violinist used to sitting in orchestras, the clarity is so much better than any other speaker I've heard. With the organ music the low bass is truly startling, and all bass seems completely without the resonance/muddiness I'm used to hearing with Bass Reflex cabs.

One really obvious point is that these speakers require a lower volume setting on the amplifier. My Cyrus 8 DAC usually sits on -27dB for serious listening; with these I get the same pain level, with a much bigger soundscape, in a much bigger space, at -30dB.

The dispersion is heaps better too: walking around, and even outside the room, they sound well balanced. Sound stage? It's very obvious where each instrument is sitting in the recording hall.

Listening to a grand piano (recent Pollini/Chopin/DGG recording) is just beautiful: there's something about the solidness of the speakers matching the solidness of a piano, and it's like there's something in the varnish that matches the sound of real instruments, too. Possibly just an impression, but they say it's the varnish that really helps make a Stradivarius sound so special.

I'm currently playing with Troels' tweak of hanging felt over the rear woofers, to cut the mid-bass a bit, but with initial listening, it sounds like the front ones are being muffled as well. So hard to be objective, so I keep having to turn all lights off, with every new placement.

Other stuff will have to wait, I think, as I fiddle more. I tilted them up 40mm at the front the other day (mainly to direct the front drivers at my head), and the bass seems clearer again, not being echoed back into the horn so much. Don't tell me I have to rebuild the feet please!

With the finish, I am OK. The minor faults are just for me to know about; they still look great. It feels like a privilege to have worked with such beautiful timbers.

So overall, and after a couple of weeks now, the thing I enjoy most is the clarity, and their ability to present huge complex scores, in detail, without effort. Being able to hear so much more in my recordings is not just a cliché: it's a powerful experience.

PS: Would anybody know of a good CD, or routine, for burning in woofers? I can't find the recommended Eminence procedure that I read somewhere on a forum...

[Sierra]

Thanks Brian ... a great description of how the sound is evolving ... I've been dying to hear what your thoughts were.

It sure is a change moving from build mode into listen mode and the expectation of how it will all sound ... I've gone through this a few times with my

car audio interests.

Your experence seems to follow the general trend ... they sound pretty ordinary upon initial fire up until things start to loosen up and then the magic

happens when all the drivers are properly run in.

Are you listening to them in your garage?? Not the an environment condusive to good SQ

Where will their permanent location be?

The Eminence drivers will require a long run in period as they are very stiff when new.

I would give them at least 200 hours before doing any critical listening and tuning.

The "tweaks" you are doing or planning on doing now may not even be nessassary once the drivers are properly broken in.

I would suggest that trying to do any tuning now with them still being so green will just confuse the issue later down the track.

Keep your steps simple ... run them in ... locate them in your final location and position ... then start your critical listening and tuning if needed

from there.

It's really exciting to hear your comments on how good they are at resolving detail in complex musical passages and how the bass response is "startling"

on organ music at such an early stage of their life.

Cant wait to hear all this for myself in the near future

As far as the burning in procedure for the Eminence woofers ... just use them normally.

They don't need to be cranked to withing a mm of their x-max to run them in.

The process I will be using is to run them every day at low listening levels ... well low enough so that is doesn't annoy the wife ... LOL

So I'll turn the system on when I get home from work and turn it off when I go to bed that night ... that will give me 6 to 7 hours running each day.

I'll just run the radio from the Tuner most of the time ... switching perhaps to a CD that has a bit of bass from time to time (Black Eyed Peas or

similar) and then turn the system up a bit when ever I find myself home alone

Perhaps you could adopt something similar ... if you have tone controls you could boost up the bass a little bit just to get the woofers moving a touch

more.

I really don't have anything classical in my collection so looking to remedy that.

Any suggestions for CD's (or vinyl) of piano recordings which has lots of dynamics in them? ... and perhaps some pipe organ stuff with deep bass notes?

And since you are an ex violinist perhaps you can recomend some some well recorded violin material too

I have a 30th Anniversary Sampler CD from Reference Recordings which has Franz Liszt: Prelude on B-A-C-H by Felix Hell on a pipe organ which has some seriously low bass extension as it makes the 8" driver on my Audax's break out in cone flap ... cant wait to hear how the DTQWT's deal with this once run in

So glad that you are happy with your build and the finish you achieved ... they look really good!

Looking forward to further updates from you as you get more hours on them ... for now ... Enjoy!!

[peacewise]

Cool thread and build, thanks for the read.

[Sierra]

Thanks for the kind words peacewise

[Sierra]

Another little update.

Since discovering that the midrange driver and waveguide no longer fitted into the cutouts of the front baffle I've had to do some delicate rework to make them fit.

The next question was how to do that without damaging the finish.

First up was to put some low tack masking tape around the edge so that should I accidentally slip I wouldn't damage the finish and secondly it wouldhopefully protect the surface of the laquer from chipping etc while sanding away at the edge.

I used 80 grit emery cloth followed by 180 grit cut into a little strip and then wrapped around a 3" PVC downpipe end I had laying around in the garage.

Thanks BioBrian for sugesting this type of sanding method ... it was really the only way of doing it I think.

Slow painstaking sanding process ... not fun at all ...

Finally the midrange driver fits as it was supposed to.

I've temporarily taken over the lounge room and turned it into my work area ... I'm trying to be very carefull with the finish so I don't scratch or

dent it ... so carpet covered with a soft blanket makes an ideal surface to work on.

Another bonus of taking over the lounge room is I get to listen to good quality tunes while I work ... and break in my new Usher S520's

There is quite a bit to sand before the wave guide fits again.

Masking tape around the wave guide.

Sanding, sanding and more sanding ...

Finally the wave guide fits again ... along with the midrange.

Masking tape removed and all dusted down.

Finaly everything fitted as it originally did ... and no scratches ... woo-hoo!!!

The only casualties are sore fingers and sore knees after doing both cabinets

*Note to self* ... Next time make driver cut outs at least 1mm bigger in diameter than the drivers!

Till the next update ... Thanks for looking.

[cheekyboy]

*Note to self* ... Next time make driver cut outs at least 1mm bigger in diameter than the drivers!

Hi Alan,

I've been following your build and it looks great, mate. They must be close to a listen now?

With your hole cutouts, it always pays to make a trial fit with the router and jig in some scrap material, before you make the final cutout in the actual baffle.

Cheers,

Keith

Edited January 1, 2013 by cheekyboy

[Sierra]

Thanks for the kind words Keith

Still a little bit more work to do till we have music ... but it's getting closer ...

Thing is we did trial the routing on some scrap ... and were really happy with how good a fit we made it at the time.

Unfortunately we didn't even consider the thickness of the finish on the cutouts or the timber movement of the front baffle pulling the hole cutouts out of round.

Guess that's what happens when you are a speaker building nube ... Live and Learn

[cheekyboy]

That's a good point, Alan, as I've had the same experience with Jarrah continuing to move. Have you considered that movement may not have finished yet? Could be wise not to drill your holes for fixing till you're ready to fit the drivers?

Cheers,

Keith