Hi...
I just stumbled across this thread when i searched for DTQWT posts... Anyway, Ive recently built the DTQWT speaker... (DTQWT by Ilpo/Sweden on Troels website)...
My building pictures...
If you have any questions I'll be glad to try and answer them... I'm running my DTQWT speakers with Cambridge Azur 640a amplifier and all I can say is that they sound absolutely fantastic...
I just stumbled across this thread when i searched for DTQWT posts... Anyway, Ive recently built the DTQWT speaker... (DTQWT by Ilpo/Sweden on Troels website)...
My building pictures...
If you have any questions I'll be glad to try and answer them... I'm running my DTQWT speakers with Cambridge Azur 640a amplifier and all I can say is that they sound absolutely fantastic...
Really nice build ipppe!
I see you have a real wood front attached to an MDF enclosure. Is there any precaution one must take when doing this to prevent cracking/splitting due to expansion of the wood? I plan on doing exactly this and am concerned it might cause problems for me. Is it glued on?
Sorry if a bit off topic!
I see you have a real wood front attached to an MDF enclosure. Is there any precaution one must take when doing this to prevent cracking/splitting due to expansion of the wood? I plan on doing exactly this and am concerned it might cause problems for me. Is it glued on?
Sorry if a bit off topic!
Dr.EM said:
Yes the whole thing is glued on, but it's not a whole piece of solid wood... I dont know whats its called in english but the piece is made of several boards glewed together... If the whole thing was one solid piece of wood I think cracking and splitting would be a bigger issue...
I dont think there is any danger for expansion, but the opposit may occur, shrinking... To prevent this I chose to wax my front like any solid wood furniture would be to prevent cracking and splitting... But I dont have any guarantees that its gonna stay perfect for 10 years, only time will tell... But the doors on my "tv-bench" is made of the same material and they are pushing 5 years now without any signs of cracking or splitting...
hope I got it right... my english isnt what it used to be
Oh! I didn't know that. I thought 'laminate' means thin material stacking 'layer by layer' -- like plywood of EI type iron core of transformer....
While the baffles ipppe is using seem more like 'block board' (without the face veneer) in which those timbers are glued together 'side by side'....
While the baffles ipppe is using seem more like 'block board' (without the face veneer) in which those timbers are glued together 'side by side'....
CLS said:Oh! I didn't know that. I thought 'laminate' means thin material stacking 'layer by layer' -- like plywood of EI type iron core of transformer....
While the baffles ipppe is using seem more like 'block board' (without the face veneer) in which those timbers are glued together 'side by side'....
Yes... I also think laminate is the wrong word... As you said the timbers are glued together side by side.. I'll attach a picture so you can see what I mean
Picture
Hi neil_kaye,
I live fairly close to Troels G. and had a chance to listen to his DTQWT speakers for a few songs a few months ago. Please note that the listening session was indeed short, and that the material was unkown to me. That being said, my impression of the speakers was very positive. The DTQWT's have a very natural, yet open sound. Dynamics are fine. The bass is tight and revealing, but may not go super-low.
I myself have a large horn rig, and the DTQWT speakers seem to share many of the characteristics that I like in a good horn system, that is, easy to drive, good dynamics, a lot of presence and "they-are-here"-sense.
Troels is very knowledgable, and has put a lot of work in this design, so you can be certain that this is very carefully conducted design in every respect. If I were to get speakers of that size and in that price-range, I would definately consider these very seriously!
PS: Absolutely beautiful work Ipppe!
Best regards
Peter
I live fairly close to Troels G. and had a chance to listen to his DTQWT speakers for a few songs a few months ago. Please note that the listening session was indeed short, and that the material was unkown to me. That being said, my impression of the speakers was very positive. The DTQWT's have a very natural, yet open sound. Dynamics are fine. The bass is tight and revealing, but may not go super-low.
I myself have a large horn rig, and the DTQWT speakers seem to share many of the characteristics that I like in a good horn system, that is, easy to drive, good dynamics, a lot of presence and "they-are-here"-sense.
Troels is very knowledgable, and has put a lot of work in this design, so you can be certain that this is very carefully conducted design in every respect. If I were to get speakers of that size and in that price-range, I would definately consider these very seriously!
PS: Absolutely beautiful work Ipppe!
Best regards
Peter
I have doubts...
about the way this speaker system works. First, unless all of the drivers sharing the same volume cover the very same passband, there's got to be interference amongst them at times. Of course I'm referring to the two woofers mounted on the rear and the midwoofer on the baffle. If that front driver is nothing more than a woofer and does indeed cover the very same range as the two rear woofers, then their sharing the same volume would be no problem. Second, Troels' description of how the woofers effect each other doesn't sound quite right to me. He said, in so many words, that when the rear woofers suck in, that will cause the front (mid)woofer to also suck in. I don't think that's correct; it seems the rear woofers would suck in from the source of air that has the least resistance, the common horn down the middle of the cabinet, and not affect or affect very little, the front woofer. I'd sure appreciate someone explaining to me why/how Troels is correct and I'm mistaken, because it just doesn't make sense to me.
about the way this speaker system works. First, unless all of the drivers sharing the same volume cover the very same passband, there's got to be interference amongst them at times. Of course I'm referring to the two woofers mounted on the rear and the midwoofer on the baffle. If that front driver is nothing more than a woofer and does indeed cover the very same range as the two rear woofers, then their sharing the same volume would be no problem. Second, Troels' description of how the woofers effect each other doesn't sound quite right to me. He said, in so many words, that when the rear woofers suck in, that will cause the front (mid)woofer to also suck in. I don't think that's correct; it seems the rear woofers would suck in from the source of air that has the least resistance, the common horn down the middle of the cabinet, and not affect or affect very little, the front woofer. I'd sure appreciate someone explaining to me why/how Troels is correct and I'm mistaken, because it just doesn't make sense to me.
Okay, I misunderstood...
Troels' description a bit. When the rear woofers push back (suck in), they will indeed push down the center horn because, as I said, the pressure wants to follow the path of least resistance. This creates the suction, as Troels said, on the cone of the midwoofer on the baffle and it, too, sucks in (but involunarily, I might add). If, for example, the midwoofer was playing music in the midrange and a significant bass note came along, the rear woofers and presumably also the midwoofer would try to reproduce it because all three drivers are allowed to. But wouldn't the sucking action created by the rear woofers cause some form of distortion to the midrange frequencies the midwoofer is trying to reproduce, more so than what is caused by a single driver reproducing multiple frequencies?
Troels' description a bit. When the rear woofers push back (suck in), they will indeed push down the center horn because, as I said, the pressure wants to follow the path of least resistance. This creates the suction, as Troels said, on the cone of the midwoofer on the baffle and it, too, sucks in (but involunarily, I might add). If, for example, the midwoofer was playing music in the midrange and a significant bass note came along, the rear woofers and presumably also the midwoofer would try to reproduce it because all three drivers are allowed to. But wouldn't the sucking action created by the rear woofers cause some form of distortion to the midrange frequencies the midwoofer is trying to reproduce, more so than what is caused by a single driver reproducing multiple frequencies?
I believe Troels' explanation is incorrect or incomplete. He says:
"Air goes where pressure is low, thus when the rear bass drivers move inwards, they will push air into the large center horn and by doing so they will suck air from the front horn and pull the membrane of the front driver. "
Let us examine this scenario:
1. The rear driver cones move inwards (into the cabinet).
2. This creates a pulse (wave) of positive pressure.
3. The pulse travels up the pipe at the speed of sound.
4. The pulse reaches the junction point where the front and rear pipes meet the main pipe.
5. The pulse splits two ways: Towards the front pipe, and down the main pipe towards the mouth.
6. When the pulse reaches the front driver, it pushes the cone outwards (not sucks inwards).
The result is more complex when you consider multiple frequencies.
At some frequencies, the front and rear drivers will move in and out together. At others, they will move "separately".
In any case, the effect is not likely to be severe enough to cause upset to the midrange being reproduced by the front driver.
Remember, electrodynamic speakers do not couple well to the air. This applies in reverse too, they do not couple air movement very well to the cone, especially when the cone is being held still by the motor.
You can try this for yourself: Place a bare driver on the bench, cone facing up. Attach it to an amplifier and drive it with a low frequency tone so that the cone moves noticeably. Now place another identical driver over the first, face down so that the cones face each other and are sealed around the joint. Do not connect anything to this driver. Note that the second driver cone moves, but not as much as the first driver did alone.
Finally, short the terminals of the second driver together, or connect them to a working amplifier that has no input signal. Note that the second driver now moves much less.
The point is that the midrange from Troels' DTQWT bass / midrange front driver is going to be affected mostly by the bass being fed to its voice coil, not the bass reaching it from the rear bass drivers.
From the above experiment, you may also notice one problem - if the crossover uses a capacitor in series with the bass/midrange driver to act as a high pass filter, this will effectively disconnect the driver from the amplifier at the bass frequencies, and the bass from the rear bass drivers might move it quite a bit. But Troels' crossover has a low value resistor and inductor across the capactior, hopefully allowing enough damping of the bass/midrange to keep it from being moved excessively by the rear speakers.
In summary, I will happily accept that the design works, but the modes of operation are very complex and cannot be adequately described by Troels' short explanation. This design would need a complex model, in Akabak or other speaker design software, to examine its behaviour.
"Air goes where pressure is low, thus when the rear bass drivers move inwards, they will push air into the large center horn and by doing so they will suck air from the front horn and pull the membrane of the front driver. "
Let us examine this scenario:
1. The rear driver cones move inwards (into the cabinet).
2. This creates a pulse (wave) of positive pressure.
3. The pulse travels up the pipe at the speed of sound.
4. The pulse reaches the junction point where the front and rear pipes meet the main pipe.
5. The pulse splits two ways: Towards the front pipe, and down the main pipe towards the mouth.
6. When the pulse reaches the front driver, it pushes the cone outwards (not sucks inwards).
The result is more complex when you consider multiple frequencies.
At some frequencies, the front and rear drivers will move in and out together. At others, they will move "separately".
In any case, the effect is not likely to be severe enough to cause upset to the midrange being reproduced by the front driver.
Remember, electrodynamic speakers do not couple well to the air. This applies in reverse too, they do not couple air movement very well to the cone, especially when the cone is being held still by the motor.
You can try this for yourself: Place a bare driver on the bench, cone facing up. Attach it to an amplifier and drive it with a low frequency tone so that the cone moves noticeably. Now place another identical driver over the first, face down so that the cones face each other and are sealed around the joint. Do not connect anything to this driver. Note that the second driver cone moves, but not as much as the first driver did alone.
Finally, short the terminals of the second driver together, or connect them to a working amplifier that has no input signal. Note that the second driver now moves much less.
The point is that the midrange from Troels' DTQWT bass / midrange front driver is going to be affected mostly by the bass being fed to its voice coil, not the bass reaching it from the rear bass drivers.
From the above experiment, you may also notice one problem - if the crossover uses a capacitor in series with the bass/midrange driver to act as a high pass filter, this will effectively disconnect the driver from the amplifier at the bass frequencies, and the bass from the rear bass drivers might move it quite a bit. But Troels' crossover has a low value resistor and inductor across the capactior, hopefully allowing enough damping of the bass/midrange to keep it from being moved excessively by the rear speakers.
In summary, I will happily accept that the design works, but the modes of operation are very complex and cannot be adequately described by Troels' short explanation. This design would need a complex model, in Akabak or other speaker design software, to examine its behaviour.
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