112 replies to this topic

[MikeSeddon]

Good one guys!

I am quite jealous of the meetup and glad that so many people rated the DTQWT's so highly.

I am also a Melbournian but am overseas at the moment. Maybe I will be able to make it to some of these events in the future (or maybe when my next speakers are finished).

Cheers,
Mike

[buzz lightyear]

Hi all
I am glad to hear that every one enjoyed the day and it was great to catch with a few of the SNA members, no problems Joe the DTQWT's can handle it . We finished listening to the DTQWT's at one o'clock in the morning (poor neighbours ). Thanks to Dave for the help with the cooking.

[Dustin]

Pat has been doing some tweaking since my last visit which I believe mainly entailed the adding and subtracting of packing material in the TL pipe, but I'm sure Pat can elaborate on that. The differences for me were subtle yet evident in a tighter and better controlled bass response, which seems to have improved on an already excellent mid range.

Gentlemen,

If one were to build a pair of these DTQWT's would it be 'usual' to play around with the damping . . or is it more a case of just experimenting?

I also notice Troels has added a tweak for the DTQWT and he appears to be pleased with the results.
Thoughts?

Partly damping rear radiation of the bass drivers does have an impact on sound, which - in particular the midrange - becomes a little dryer and appear to be more focused from the JA8008 driver. It's not a major tweak, but my panels are going to stay.

Tweak #2
Damping rear radiation from the Eminence bass drivers

http://www.troelsgra...TQWT_tweaks.htm


Cheers,
Gavin

[houdinifangs]

I was lucky enough to hear these beautiful speakers with a few others last weekend. Wow! An amazing job Pat I was simply stunned. These speakers showed real finesse and some solid grunt too. Enjoyed all the "proper" music but hearing Down again was a real highlight as well. Simply incredible how much these speakers could make with only 8w. Thanks Pat you were an extremely generous host with some wonderful kit.

[Paul Spencer]

They are here:
http://redspade-audi...oels-dtqwt.html



They were a treat and Pat was a great host! Very enjoyable way to spend a Friday evening.

Were these driven with just an 8w amp?!

[Nigel]

Can someone please explain what these type of speakers do ?
I presume there is more than the tweeter and mid/bass driver? perhaps the rear wave (back loaded) or something or another driver in the box ?
The name DTQWT seems to imply a calculation to achieve something ??
I see the tweeter placed v. close to the mid which is good, but I suspect there is more ...????

[houdinifangs]

Two more drivers at the back. This is from the Troels site:


Follow Paul's link above for more details and pics of Pat's speakers

Edited by houdinifangs, 17 April 2012 - 10:30 PM.

[jaspert]

I've just had an "I'm an idiot" moment. Only just realised it was yesterday Was looking forward to this one, apologies to Pat; somehow I still thought it was about a few weeks away. Note to self, check the diary! I think you guys had more fun than me yesterday.

Paul,
Your post from last August gave me a chuckle now. I had the same "I'm an idiot" moment when I got the evening mixed up. Strange to find no cars outside and couldn't reach Pat on the phone, frantiically rechecked the PM and found the reason... duh! Sorry Pat.

Edited by jaspert, 17 April 2012 - 11:07 PM.

[Paul Spencer]

I was wondering what happened to you Jasper! You missed a good night.

Nigel,

I believe it means double tapered quarter wave tube. It has an 8" high sensitivity mid and a quick look at the box suggests 1/4 wave horn loading to about 40 Hz. The midwoofer on the front and the dual 10" Eminence Deltalite drivers on the back each have a tapered line terminating in the downfiring mouth. I believe it's around 95 db in sensitivity. Close mounting of tweeter and mid is probably related to minimising c-c distance considering an 8" mid and waveguide on the tweeter.

[gainphile]

Amazing design and superb execution indeed. How low do these beast go??

Was the characteristic 15khz dip of waveguide-loaded dome tweeters evident during listening?



Would be interesting if comparison could be made with XT25 as its phase plug completely eliminate this.

[Nigel]

Thanks Paul, Houdinifangs, Gain,
but I still don't see why this design is desirable and unfortunately Gain's graph stops at 300Hz.
Rear firing bass, with a downward port ? what does that do ?
Still trying to understand what is so special about 1/4 wave....

[gainphile]

Most appealing for me, although I had not heard them (and would love to!) is the willingness to address directivity using waveguides. Then the sensitivity factor.

I have only once heard horn loading (Cain Cain) and that was ok for 8" driver. Will form an opinion if hearing these one day and when Paul's monsters are done !

Rear firing does not really matter when you have the space. At lower frequencies these operates as omni-directional.

[houdinifangs]

Thanks Paul, Houdinifangs, Gain,
but I still don't see why this design is desirable and unfortunately Gain's graph stops at 300Hz.
Rear firing bass, with a downward port ? what does that do ?
Still trying to understand what is so special about 1/4 wave....

Nigel I'm not technical and can only comment on how impressed I am with the implementation of a design that goes over my head. However, what I can say without hesitation is that was is most desirable is that it works - really well

[Paul Spencer]

Nigel, you could actually read about it!
http://www.troelsgra...A8008_DTQWT.htm

Here is the box:



It's not quite as conventional as it looks!

The midwoofer and woofers all share a common 1/4 wave horn, where the mouth points down at the floor. That should tune it to around 40 Hz.

What is the appeal of this design? Firstly, you have a waveguide to get the tweeter to more closely match the dispersion of a larger mid, and help it cross a bit lower and possibly also have a simpler crossover. All those things combine to allowing you to get a smooth dispersion avoiding sudden changes at the crossover. It also means we have a dome tweeter in a high sensitivity design, 95 db. Now let's add the horn and we have a couple of ~94 db woofers combining to 97 db. So now we have a passive 3 way speaker that can be driven by just about any amp, except perhaps one with a very low damping factor because below tuning the horn won't control excursion at all. Looking at the mid you could tell there was no rumble filter.

This is an ideal speaker for many valve enthusiasts. The dispersion is wider than an Ewave so it's not the speaker for those who have an overly bright room without WAF approval to treat.

[DanFi]

Is there anyone who has herd this speaker and any other of troels designs? I have the CNO2.5 and am interested in building the DTQWT for my dad.

[hochopeper]

Check the link in post #95 up the page a bit

[Sierra]

You've done a great job with your build buzz lightyear ... they look great and obviously sound sensational going by the response of all that have heard yours.

I'm about to embark on the same journey as you building my own DTQWT.
Parts kit arrived from Jantzen Audio last week ... and yesterday I placed an order for the Deltalite bass drivers ... fun times ahead

[buzz lightyear]

Make sure you post some pics of your project you will be very pleased with the DTQWT, where in Vic do you live Sierra?

[Sierra]

I think I'm going to be more than pleased with the DTQWT
I originally started looking for something second hand ... but it had to be of reasoanable efficiency to suit my valve amp... then I thought I'll also have a look at was around in DIY.
I hadn't visited Troel's website in a number of years so was pleasently surprised by all the new design's he had available since the last time I had visited.
As soon as I saw the "High Efficiency" DTQWT I was hooked ... the more I read about them on his website the more I wanted them ... being designed to be driven by valve amplification they were just what I was after.
Then I was reading through the various user builds of the DTQWT one of the links lead me to your thread
After reading your thread and the great comments on how yours sounded I had an even bigger smile on my face as it confirmed I made a good choice.

Yes I'll start a build thread as things start to progress.

I'm over in the eastern suburbs ... Knoxfield area ... you?

[buzz lightyear]

Looking forward to Reading your thread on the DTQWT's , I live in Hoppers Crossing area.

[atilsley]

Congrats...nice build.

I read with interest recently this speaker now the personal fave of none other than mr Nelson Pass.

[buzz lightyear]

Thanks atilsley that's positive comment from Nelson Pass.

[atty]

What an interesting build! Definable a speaker i would love to build one day..