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Another Troels Gravesen's DTQWT Project Build

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37 minutes ago, BioBrian said:

An upskirt squint would dispel any thought of similarity with a bass reflex design - if we are indeed talking about the DTQWT. I'd half-cheekily say that it has more in common with a waveguide.

Disagree completely.   (Yes, we are talking about the same thing)..... perhaps we have a terminology different (?!)

 

1. "waveguide"....

Does not allow the rear radiation of the driver to escape anywhere

Constrains the front radiation of the driver

 

2.   "bass reflex"

The front radiation of the driver is allowed free

The rear radiation of the driver goes into a chamber, which has a hole in it .... the pressure escapes through this hole.

 

 

DTQWT is not #1 .... and is is #2.

 

What is the difference between "bass reflex", and a "rear loaded horn"....   Only the where you define the line between "the box", and "the port".    DTQWT is just a "small box, with an enormous port".

 

Like I said... .it's does't matter.    ;):D 

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Pictures are much more effective....  :)

 

The point being that a QWT is a variation of a BR ....   as is everything which encloses the back of the driver, and lets it out eventually....

 

 

You could say that that the arrangement behind the driver in a QWT is a "waveguide" .... sure, it's a structure which is guiding the rear radiation of the driver.... but then the "port" in a "BR" is equally a "waveguide"....   and neither of these things fit the typical definition of "waveguide" which is as drawn below.

 

 

301830244_IMG_1460(1).thumb.jpg.63b55824390ec8d393ea2b1e97562bfb.jpg

Edited by davewantsmoore

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(I did look it up) I see BR as having a vent designed to modify the behaviour of enclosed air, specifically WRT the resonance frequency of the driver. The DTQWT doesn't attempt that, hence my surprise.

 

The rear of the DTQWT drivers could be seen as radiating into the external environment, almost as much as the front radiation. The opening of this box is very large; I wouldn't consider that it is a controlling pressure regulator like a BR vent. It is, but to nothing like that degree.

 

Glad you got where I was heading with the waveguide thing - to complete the idea, I was referring to how the waveguide, and the horn/tube, both give an acoustical boost to the lower frequencies, directionality notwithstanding. (That's legal-speak for "don't even bother trying, this sentence will never make sense).

 

I think "DTQWT" describes these speakers most meaningfully - they are rather unique, well worth the several years it takes for "DTQWT" to roll off the tongue reliably in conversation. It's so easy to type, though!

 

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3 hours ago, BioBrian said:

The DTQWT doesn't attempt that

Sure it does....  ;)

 

Don't worry, even TG says "it's very different to a BR".  Heh.  (shakeshead).  Maybe I'll bang on about this more another time.

 

 

These are all just "vented boxes" .... where the shape of the box, and the shape of the vent are different sizes/shapes.     Sure, the QWT is better than many   :)

 

 

Here's another example.   They call this a 'horn'.   Is it really?!   ?B) 

 

tapped-horn.png?w=525

 

Edited by davewantsmoore

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I must agree, 3-dimensional horns should be the only ones to deserve the name 'horn'. Our mate Linc can certainly hold his head high.

Image resultImage result

 

French Horn                                                                                                                     Cor Anglais  (English Horn with a French name)

 

Edited by BioBrian
Too much fresh air

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Only a few hours have passed since my last post and I am outdated again ..... do you go very fast or does the time difference affect me exclusively? ( jet lang ? ) :emot-bang:
I have to deduce then:

Brian has built a new project but changing controllers and crossover networks but with the same boxes of the previous project. I read the last post of the link of his great work (that is to put desire, man!), I think there is no other.

I also deduce that the bass sector of its construction is not a horn ..... I see an open baflfe, and I swear I'm sober ..... correct please, maybe I need an urgent consultation with the eye doctor or with the neurologist ...

Generalizing a lot, I believe that a small waveguide is just a small horn ..... on a tweeter as they use DTQWT helps and much to the dispersion of the treble on all axes and in turn increases the SPL.
At low frequencies, it's another story.
If you have had the opportunity to listen to the great American classic bass cabinets, you will find the three great brands that made history.
JBL, who occasionally used horns for their projects and I think it would be hard to find an example on the web.
Electro voice, which I use horns and believe me, were two very different sounds. Dry and fast JBL, deep EV and with tremendous sound stage. Like Altec, they were preferred by musicians in their outdoor shows.
VOTT is too well known and famous for me to open my mouth here about him.
I have read that the reason for this difference is that the horns,,  when the larger they are, the more faveceren the coupling (acoustic impedance) between the cone of the speaker and the air. They have other problems, purists say, but the sensation of presence they offer is not achieved by the boxes or closed or with ports.
I think Dave's drawing is overlooking this typical horn phenomenon.
There were four days of rain here, I will go out to the garden to take some sun, we are in Autumn and it makes a summer temperature, heat and humidity ... my bones need to eliminate the accumulated internal humidity ......:angry:
 

Edited by arpavieja78

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6 hours ago, arpavieja78 said:

I have read that the reason for this difference is that the horns,,  when the larger they are, the more faveceren the coupling (acoustic impedance) between the cone of the speaker and the air.

 

Yes, result is some combination of higher SPL and increased directivity.

 

Quote

I think Dave's drawing is overlooking this typical horn phenomenon.

Not "overlooking it" .... Just not focussing on it too much ;)

 

6 hours ago, arpavieja78 said:

VOTT is too well known and famous for me to open my mouth here about him.

Nice example.   This is not a very horn loaded bass.

 

The horn (in the A7 cabinet for example) only works above ~200Hz ...... otherwise, it is a BR box.   People say, oh the "horn loaded bass is awesome".... but there is none  ;) 

 

 

Don't get me wrong, this is all just fun "semantics" ..... and "what's in a name?".    The point is the for speakers where the rear radiation is enclosed in a space and the pressure eventually makes it out to join with the front radiation .... are all really the same type of box.    Of course, they come in all different shapes and sizes (like everything) with different performance.    The way to fundamentally understand them (and how to model them, etc.), is to realise they are all variations of the same thing  (as much as the "marketing department" will struggle against that).

Edited by davewantsmoore

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14 hours ago, davewantsmoore said:

 

Don't get me wrong, this is all just fun "semantics" ..... 

 

Of course, we are doing a bit of relaxation, and I assume that I have a slightly light mouth .......;)  I have been looking for and found examples of classic JBL horns, Paragon, Hartsfield, among them. But I was referring to the PA line ...

 

 

 

We had a terrible time here, and this picture came out in a diary.

And I remembered a professor (far away in time) who explained that this photo is actually a giant capacitor of Mother Nature. Do not ever forget, good examples to support the theory help a lot, but the enthusiasm with which they are transmitted is an important part too, nothing more boring than a purely mathematical teacher .....

The atmosphere is positive, the earth the negative. The air is dielectric, but it is loaded with moisture, and when this humidity exceeds a limit, a leak occurs, the electrons of different charges are joined and boooommmmmmmmmmmm, fall a few hundred thousand volts that we call lightning. I'm still fascinated......:o

Tormenta en Buenos Aires 30-04-18.jpg

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On 29/04/2018 at 7:40 PM, BioBrian said:

 

"For that reason, I think that the best of the worlds is enjoyed by those who can hear something like that, in the open air. Do not worry about phases or reverberations, like the sound of thunder, everything that comes out of there, will dissipate in a native way"

 

Brian

 

Thanks Brian ! :D

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15 hours ago, davewantsmoore said:

 

 

The horn (in the A7 cabinet for example) only works above ~200Hz ...... otherwise, it is a BR box.   People say, oh the "horn loaded bass is awesome".... but there is none  ;) 

 

 

 

I once listened to the Altec Nineteen, the specs say 30 hertz, but less how many DB? Anyway, they impressed ...

The team was:

Teac TN400
SME with Shure V-15 Type III
Mc Intosh MA6100
Altec Lansing Nineteen
Direct cut vinyl, Carmen de Bizet, that was exciting!
I do not remember the director, but surely it was not Stokowsky!

-----------------------------------------------------------------
And when a friend who traveled to the USA asked me for advice, and I was afraid of the cost of luggage, I recommended AR-15 and a good power amplifier, a Sony of 120 Watts rms per channel ...... When we put it in operation, I had to work hard to show enthusiasm for the sound achieved .....
From there, I always say: small boxes, small sound, big boxes, big sound. There is no escape .

----------------------------------------------------

 

( See quote )

All Vott models will have better bass if we take advantage of the gain of the room......:P

Place them in a corner, or you can also exchange them for a Klipschorn ....... This improves the WAF automatically, too..... :o

 

https://greatplainsaudio.com/altec-lansing-library/altec-lansing-voice-theatre-vott/

---------------------------------------------------

Happy Labor Day to all !

 

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Greetings Gents. A while since I checked in on this thread. 

 

A quick up date--The Problem:

 

I've been living with the DTQWT-iii's for a while now, and the creeping realization finally burst into consciousness that something is wrong, something is missing, that these speakers leave me feeling disappointed every time I listen to them. I had almost made up my mind to move on to another speaker build and abandon these speakers to office background duty at work. Before making that final, I also considered bi-amping or tri-amping with an active  cross-over to replace the speaker's internal cross over, and while reading about the cross over points on Troels' website I found "it"! I discovered the problem and the solution all in one.

 

The Shameful Solution:

 

Normally, I wouldn't admit to this, but it was such an easy mistake to make, at least for me, that I wondered if some of you might have done the same thing. It's careless, it's sloppy, I admit it. And ridiculous, since I took such care in building the speaker. Anyway, here it is:  To get the tweeter and midrange in phase with each other, we have to reverse the polarity of the tweeter. Troels' cross over diagram shows this, if you look carefully, and the text states it explicitly. 

 

Five minutes with a philips screwdriver and a soldering iron, and I had a new pair of speakers entirely. No longer is there a sense of them being somewhat listless, un lively and somewhat veiled. That's made ALL the difference.

 

So . . . I hope that helps, or better yet, I hope that doesn't help anyone at all because everyone was more careful than me. 

 

Happy Troeling.

 

Brenton

Edited by Tube Nube

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Greetings Gents. A while since I checked in on this thread. 
 
A quick up date--The Problem:
 
I've been living with the DTQWT-iii's for a while now, and the creeping realization finally burst into consciousness that something is wrong, something is missing, that these speakers leave me feeling disappointed every time I listen to them. I had almost made up my mind to move on to another speaker build and abandon these speakers to office background duty at work. Before making that final, I also considered bi-amping or tri-amping with an active  cross-over to replace the speaker's internal cross over, and while reading about the cross over points on Troels' website I found "it"! I discovered the problem and the solution all in one.
 
The Shameful Solution:
 
Normally, I wouldn't admit to this, but it was such an easy mistake to make, at least for me, that I wondered if some of you might have done the same thing. It's careless, it's sloppy, I admit it. And ridiculous, since I took such care in building the speaker. Anyway, here it is:  To get the tweeter and midrange in phase with each other, we have to reverse the polarity of the tweeter. Troels' cross over diagram shows this, if you look carefully, and the text states it explicitly. 
 
Five minutes with a philips screwdriver and a soldering iron, and I had a new pair of speakers entirely. No longer is there a sense of them being somewhat listless, un lively and somewhat veiled. That's made ALL the difference.
 
So . . . I hope that helps, or better yet, I hope that doesn't help anyone at all because everyone was more careful than me. 
 
Happy Troeling.
 
Brenton
Easily done, I'll admit I have done the same in the past.

Iv always been interested in the troels dtqwt. I guy I loosely know has both these (don't know what series) and the statements ii and he says that he preference is the statements.

An interesting comparison from two great designers and their 'best shot'

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Interesting W_L that your friend prefers the Statements. I also considered the DTQWT but ended up building the Statements and was never able to compare them directly. I am about to upgrade them to Statement II.

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