DTQWT speakers vs. (Mini) Statements ???

[miyami]

Hello forum,

does anybody have experience with the DTQWT quarter wave tube transmission line design from Troels Gravesen? How do the different versions affect the overall sound experience? And how does the mid and high range compare to a speaker like the Mini Statements (or full Statements) from Jim Holtz and Curt Campbell?

Thanks,

Miyami

[JonMarsh]

Are you referring to the full DTQWT MkII system, with the auxiliary bass cabinet, and with which tweeter version? I have not constructed the full system, but I have experimented with the very same Jantzen waveguides and several of the tweeters. If you build this with the original Audax tweeter, you MUST (IMO) do the modifications to the driver Troels describes to reduce some of the resonances. My recommendation though would be to use the Seas T35C002- much nicer characteristics with much better damping- just look at the CSD plots! The Seas can cross a bit lower, which helps with the Seas mid woofer.

now, by Troel's own acknowledgement, his high frequency measurements are rolled off a bit, due to his microphone choice, but regardless, these are 35 mm tweeters and are not noted for having a super extended top end, certainly not a ribbon like sound. OTOH, with the waveguide, they will have good performance up to 18 kHz or so including well off axis, something most standard tweeters, including ribbons, don't do so well. So, you might be surprised at a more positive impression of HF performance than the graphs will lead you to expect at first blush...

The total TQWT system is quite sensitive, (plays loud for a few watts), so if you're using vacuum tubes or some other lower power amplifier, that may make their large size worthwhile, especially if you have a large room to fill.

OTOH, if you have more normal amplification or need something more compact, I'd be inclined to recommend considering something like either a NatalieP built into a tower with the extended low frequency tuning (much, much less expensive and easier to build) or the Modual MT XE/Mkii with waveguide and a sub. Would take a lot less space, probably be easier to place and setup. Mini Statements are well liked also- more complex to build, but quite popular. You need to plan on having a certain amount of space free behind them, according to Jim and Kurt, to accommodate the rear radiation from the midrange tunnels.

[miyami]

Hello Jon,
yes, I was referring to the full DTQWT (MkII), and here is the rational, that I should have explained better:
I want to built a floor standing speaker with an emphasize on clear sound (well, that's probably everybody's goal....) that can give me a full sound stage. I originally looked at Zaph's ZRT2.5, since the Scanspeek woofers are supposed to be the best mid-bass woofers out there, promising very low distortion levels. But when I listened to a Zaph ZRT 2, I wasn't so sure anymore if that would be the right choice. There might have been something wrong with the speaker, but I wasn't convinced at all with the performance. After reading a lot of good reviews I was contemplating Jim Holtz's Statements, but the better half insisted that they are too big. Next in line were the mini statements, which have a more reasonable size, or some floor standing adaption of the finalists from Jim. The problem with these is that they need to be located 18'' in front of a wall, which makes placing them difficult.
I then came across the DTQWT, and thought that they might be actually a good alternative for very clear un-distorted sound in the mid to high range. Size is about the same as the Mini-Statements only deeper (19.7'' compared to 13.75''). Now the question is how do they compare? I have not heard anything about the Jenzen JA8008, and how it compares to speakers like the Tang Band W4-1337SA or the Vifa NE149W-07.
As you said, I noticed that Troels frequency measurements seem to bend down beyond 10kHz, and below 40Hz, and am not sure what to make out of it.
What is your experience with this setup?

And yes, I was thinking of the SEAS T35C002 option and will power them with a NAD C350 60 wpc solid state amplifier in a 14'x20' room.
(I have to admit, I have been attracted by an internal horn design since a long time, but am certainly open to other suggestions.... )

[Jim Holtz]

I'll chime in here with a thought. The Finalists built in a floor stander will give you strong performance to the low 30's with extremely clear and natural midrange and pristine highs. They also are designed to allow near wall placement by flipping a switch and plugging the mid tunnel. That gives you the option to pull them out a bit when you want to listen to music and recreate the original soundstage. They are very flexible. They have been my music reference for the last few months and I consider them the updated replacement for both the Mini Statements and Monitors.

HTH

Jim

[JonMarsh]

Hello Jon,
yes, I was referring to the full DTQWT (MkII), and here is the rational, that I should have explained better:
I want to built a floor standing speaker with an emphasize on clear sound (well, that's probably everybody's goal....) that can give me a full sound stage. I originally looked at Zaph's ZRT2.5, since the Scanspeek woofers are supposed to be the best mid-bass woofers out there, promising very low distortion levels. But when I listened to a Zaph ZRT 2, I wasn't so sure anymore if that would be the right choice. There might have been something wrong with the speaker, but I wasn't convinced at all with the performance. After reading a lot of good reviews I was contemplating Jim Holtz's Statements, but the better half insisted that they are too big. Next in line were the mini statements, which have a more reasonable size, or some floor standing adaption of the finalists from Jim. The problem with these is that they need to be located 18'' in front of a wall, which makes placing them difficult.
I then came across the DTQWT, and thought that they might be actually a good alternative for very clear un-distorted sound in the mid to high range. Size is about the same as the Mini-Statements only deeper (19.7'' compared to 13.75''). Now the question is how do they compare? I have not heard anything about the Jenzen JA8008, and how it compares to speakers like the Tang Band W4-1337SA or the Vifa NE149W-07.
As you said, I noticed that Troels frequency measurements seem to bend down beyond 10kHz, and below 40Hz, and am not sure what to make out of it.
What is your experience with this setup?

And yes, I was thinking of the SEAS T35C002 option and will power them with a NAD C350 60 wpc solid state amplifier in a 14'x20' room.
(I have to admit, I have been attracted by an internal horn design since a long time, but am certainly open to other suggestions.... )

First thing- with regards to the full DTQWT, even with the two Eminence 10" woofers in the secondary cabinet, the output level capability is increased, but not so much the frequency extension- this can be basically determined by looking at the impedance curve minima, as this system behaves much like a ported cabinet, and the roll off point is at the minima or higher.



From examination you can see this is around 37-38Hz, so a roll off starting at 40 Hz is about right, as regards what to expect.

Now, there's also the matter of room placement, which exists for LF performance for all speakers not built in flush to a boundary- here Troels measures (realistically) quite a variety of performance.



This reference thread highlights the math behind the boundary reflection issues, for the primary boundaries (floor, rear wall, side wall) and highlights why they should be spaced on golden mean ratios.

https://www.htguide.com/forum/showthread.php?10872-Guestimating-room-gain&p=138262#post138262

A very good pragmatic resource for setup hints is found on the Cardas Cable web site, with their guide to speaker placement for different size and shapes of room. Ignore at your own peril!


As a practical example, for my own Isiris speaker in GF's family room, two different placements, one that makes her happy, one that makes me happy! :W






Less than optimum speaker placement is one of the most common issues with not getting the sound you deserve from a system...

[miyami]

So is the trouble with the DTQWT design, that the tweeter waveguide cannot support the higher SPLs above 11kHz, and the QWT is not tuned for frequencies below 40Hz - leading to a reduced interval of flat frequency response? Troels emphasizes that the main advantages of such a design is the low distortion and high efficiency, but it apparently comes at a price.
Are there any similar designs out there that do not have these issues?

Jim: Thanks for the suggestion, I am more and more considering the Finalists. The only problem I have with these is that they would be relatively large when built as a floor standing speaker with lots of unused volume. That makes me think of two questions: Is there an advantage sound-wise of building the woofer its own enclosure - basically extending the volume into the bottom part and closing off the upper cabinet (I think I have seen people doing that)? I know that the front baffle dimensions are pretty much fixed, can the speaker depth be varied? I read somewhere (I believe it was Curt saying this) that a 10% margin is ok, but could this be changed by choosing a different tube diameter, or is the length fixed by a tuning frequency?

[Jim Holtz]

Jim: Thanks for the suggestion, I am more and more considering the Finalists. The only problem I have with these is that they would be relatively large when built as a floor standing speaker with lots of unused volume. That makes me think of two questions: Is there an advantage sound-wise of building the woofer its own enclosure - basically extending the volume into the bottom part and closing off the upper cabinet (I think I have seen people doing that)? I know that the front baffle dimensions are pretty much fixed, can the speaker depth be varied? I read somewhere (I believe it was Curt saying this) that a 10% margin is ok, but could this be changed by choosing a different tube diameter, or is the length fixed by a tuning frequency?

The size will be the same whether they're built as a floor stander or sitting on stands. The tweeter still needs to be at ear level which is usual 39 - 40" for most adults in modern day furniture. The only difference is, the space below the speaker is enclosed with a floor stander.

To answer your questions;

Is there an advantage sound-wise of building the woofer its own enclosure - basically extending the volume into the bottom part and closing off the upper cabinet (I think I have seen people doing that)?

No, the sound quality will be the same.

I know that the front baffle dimensions are pretty much fixed, can the speaker depth be varied? I read somewhere (I believe it was Curt saying this) that a 10% margin is ok, but could this be changed by choosing a different tube diameter, or is the length fixed by a tuning frequency?

10% is correct. That would apply to width and depth. The tunnel length and diameter should not be changed.

The Finalists were designed to have the performance and sound quality of large full range speakers in a monitor size cabinet that was flexible enough to allow normal or very close wall positioning. Like any other DIY design you can change it but it will probably no longer sound as designed.

Jim

[Paul K.]

To miyami and Jim,
Earlier this month I modeled a folded ML-TL for the RS225-8 for a one-off Finalist for another person. Basically the lower part of the cabinet below the midrange tunnel was extended internally to ~31", and a solid divider was placed below the tunnel to create a separate, isolated chamber for the woofer. This ML-TL has a line length of ~62". The external height of the now floor-standing cabinet ended up at 44.5" with the tweeter's center 36.25" above the floor. The original cabinet depth and width were maintained as was everything for the midrange and tweeter. The modeled anechoic f3 I achieved was 31-32 Hz. Don't know when this will be built, though.
Paul

[Jim Holtz]

To miyami and Jim,
Earlier this month I modeled a folded ML-TL for the RS225-8 for a one-off Finalist for another person. Basically the lower part of the cabinet below the midrange tunnel was extended internally to ~31", and a solid divider was placed below the tunnel to create a separate, isolated chamber for the woofer. This ML-TL has a line length of ~62". The external height of the now floor-standing cabinet ended up at 44.5" with the tweeter's center 36.25" above the floor. The original cabinet depth and width were maintained as was everything for the midrange and tweeter. The modeled anechoic f3 I achieved was 31-32 Hz. Don't know when this will be built, though.
Paul

Hi Paul,

Thanks for jumping in. Converting the Finalists to a TL would be a good reason to convert to a floor standing speaker. However, the tweeter would be a bit low for most people with out raising the cabinet another 3".

Since I've got your attention. :W TL's make a lot of sense to me for a two way but I don't see a real advantage in a 3-way design since there's a dedicated mid range driver. What am I not understanding about TL designs?

Jim

[Paul K.]

Hi back, Jim,
The average height of people's ears when sitting is often quoted as 36". Many of my personal builds have the tweeter's center pretty much at 36" and they sound fine to me. I can't imagine if a person's ears ended up an inch or two lower or higher than a tweeter's center that the speaker system would now be unlistenable or even significantly different? I should also say that if a tweeter's center in any of my builds ends up in the 35" to 38" range above the floor, I'm perfectly happy.

I understand your comment about using a TL for the woofer in a 3-way since it's true that the TL stuffing really helps the midrange quality in a 2-way. I'm not about to state there's something magical about TL bass, but the way I implement and shape the system bass response always ends up with bass that's very articulate and as deep as I want it to be (although an f3 below the low- to mid-30s is overkill).

At the last Iowa DIY event you overslept and arrived after my speakers, the Amarosos, had been played. Those 3-ways also use the RS225-8 and also in a folded ML-TL very similar to that I designed for the one-off Finalists, differing in performance with a higher f3 around 34 Hz. If you had heard them maybe your question would have been answered?
Paul

Hi Paul,

Thanks for jumping in. Converting the Finalists to a TL would be a good reason to convert to a floor standing speaker. However, the tweeter would be a bit low for most people with out raising the cabinet another 3".

Since I've got your attention. :W TL's make a lot of sense to me for a two way but I don't see a real advantage in a 3-way design since there's a dedicated mid range driver. What am I not understanding about TL designs?

Jim

[miyami]

This sounds interesting. I am not an expert in speaker design at all, and especially not in TL design, but isn't a TL basically an equivalent to a vented system with the goal of making the air/driver coupling more efficient (i.e. by reducing the impedance peak at a drivers resonance and thus making it more efficient in the surrounding frequency range), with the additional benefit of significantly damping the back reflection wave and thus reducing distortion?
So even if distortion reduction is not the main goal in the lower frequencies, the TL would still increase the flat response range significantly. If that's correct, a vented system would be just easier to built.
As I said, I am only a layman in these things, so I might be totally wrong with this....

But it does sound very attracting. Would you be willing to share your design?

[Paul K.]

TLs are inherently 4th-order systems just like vented designs. Depending on the driver and the TL design/implementation, the roll-off below f3 is not necessarily 4th-order, however, and is often 3rd-order or a bit slower. If one wants to, a line can be filled with fiber to the point that there's only one impedance peak, very similar to a sealed box response, but then there's little, if any bass support/contribution from the line's terminus or mass-loading port. The overall shape of the system's bass response can be customized to suit the designer's preference. There's a basic shape I always shoot for and when coupled with 3 to 3.5 dB of BSC, the result is articulate bass that's never boomy or muddy in my home, where the speakers are close to the wall, or at DIY venues when the speakers are well away from walls. Their bass response sounds pretty much the same IOW, not much influenced by the acoustical environments.

As to sharing the one-off Finalist design, I'd first have to ask the person I did it for. He may not want to share at all, or he may want to wait until after he built it, or he might say, sure, go ahead.
Paul

This sounds interesting. I am not an expert in speaker design at all, and especially not in TL design, but isn't a TL basically an equivalent to a vented system with the goal of making the air/driver coupling more efficient (i.e. by reducing the impedance peak at a drivers resonance and thus making it more efficient in the surrounding frequency range), with the additional benefit of significantly damping the back reflection wave and thus reducing distortion?
So even if distortion reduction is not the main goal in the lower frequencies, the TL would still increase the flat response range significantly. If that's correct, a vented system would be just easier to built.
As I said, I am only a layman in these things, so I might be totally wrong with this....

But it does sound very attracting. Would you be willing to share your design?

[Paul K.]

Floor-stander Finalists ML-TL version

miyami,
The person for which I designed this ML-TL version told me he was okay with me sharing the design. He had intended to be well into his own build of it by now, but storms damaged his house and he's in the middle of effecting repairs.

I've attached a drawing for the lower part of the cabinet housing the folded, ML-TL. Starting with Jim's original cabinet, you simply replace the window brace below the midrange tunnel with a solid divider, and below that you add 31.25" of height for the woofer's compartment. The original cabinet depth and width is maintained as are the locations of all three drivers on the baffle relative to the baffle's top and sides. Using 3/4"-thick panels all around, except for the baffle, makes the external height of the cabinet be 44.5". Previously I said this places the tweeter's center at 36.25" above the floor--that was incorrect. The tweeter's center will be 41.625" above the floor. That may be a bit too high but it's more in line with Jim's preference and it will definitely be better for the guy I designed this for with his HT setup. [When I calculated the tweeter height I got in a hurry and mistakenly used the center location dimension for the midrange driver ops:] If you're really interested in this for a personal build and would prefer the tweeter to be lower, I can easily re-design the woofer compartment a couple or so inches shorter. This will not negatively impact the resulting ML-TL to any audible extent.

Going on, now that I've embarrassed myself, the folded line is created by the vertical center divider, and the line has a constant cross-section along its 63.25" length that's 9.5"W x 6.375"D. The mass-loading port is on the rear panel with its center 10.25" above the internal bottom. The non-flared port has a 3" diameter and 4.25" length. All of the first half of the line is filled with polyester fiber at a uniform density of 0.75 lb/ft3, requiring a total of ~14 ounces of fiber. With dotted lines I've shown locations for 4 suggested window braces.

The second attachment shows the predicted system bass response (red line) for a 2.83-volt input and measured at 1 meter in an essentially anechoic environment. As you can see f3 is 31-32 Hz.

If you have any questions or would like to see a different model with a shorter cabinet that places the tweeter height lower, I'm game.
Paul

[miyami]

Hello Paul,
thanks for the design. This looks very intriguing, and might push me over the edge to finally built the Finalist...
To better understand your design, I would like to ask a couple questions:
What is the advantage of having both ends of the line at the bottom compared to a flipped design with both ends at the top?
Is the exact driver placement critical?
Could the narrow distance between the internal port opening and the divider be of some concern?
Is it possible to use a flared port?

And a general design question for this setup: Could the top portion of the Finalist be flipped, positioning the tweeter between the mid and the bass? This would give the opportunity to use some of the volume behind the tweeter for the TL to reduce cabinet height? I realize though that this places the tweeter even lower than Jim recommends, so this would be a theoretical question...

[Paul K.]

I configured the folded ML-TL so that all three of the drivers could be placed in the exact same locations on the baffle relative to the top of the baffle and not muck up the crossover design or the sound. Once that was decided, I then modeled several different folded line versions within the allocated space to see what worked best overall and wasn't overly complicated, then settled on what you see. The line is optimized for the woofer's location as is the port's location. The port's clearance is acceptable. The rule of thumb is to have a least one port diameter clearance from any internal panels. As I've shown it, the internal end of the port is 2.875" from the line divider and that's plenty close enough to 3" in my book. I used a 3"-diameter port in order to keep the peak air velocity in it acceptably low when driving the woofer with enough power for it to reach an excursion of Xmax+15%, meaning there would be no need to use a flared port IMO. A 3"-diameter flared port will have to be longer in order for the system tuning frequency to be the same, and that would make it too long for adequate clearance from the line divider, unless you put a bend in the port.

If you flipped the tweeter and midrange locations so the volume behind the tweeter could be also part of the TL cavity, the crossover as designed for the Finalists would no longer be optimum, necessitating a re-design.
Paul

Hello Paul,
thanks for the design. This looks very intriguing, and might push me over the edge to finally built the Finalist...
To better understand your design, I would like to ask a couple questions:
What is the advantage of having both ends of the line at the bottom compared to a flipped design with both ends at the top?
Is the exact driver placement critical?
Could the narrow distance between the internal port opening and the divider be of some concern?
Is it possible to use a flared port?

And a general design question for this setup: Could the top portion of the Finalist be flipped, positioning the tweeter between the mid and the bass? This would give the opportunity to use some of the volume behind the tweeter for the TL to reduce cabinet height? I realize though that this places the tweeter even lower than Jim recommends, so this would be a theoretical question...

[miyami]

I was wandering around for other TL designs and found your winning Amarosos and canTiLenas. How would you expect the TL-Finalists to perform compared to them?
I wish there was something like the MWAF in Southern California so I could listen to all these great designs.......

[Paul K.]

Unfortunately I've not heard the Finalists in any version and I'm probably not entirely objective. I have no doubt the Finalists as designed sound very good. Since the TL-Finalists would use the same woofer as in the Amarosos and their TL designs would almost be identical, I would expect their bass responses would also sound very similar, subject to possible differences in how much BSC is used in their crossovers and room placements. As good as the RS225 is, the Scan woofer in the canTiLenas is better, primarily in its ability to play louder due to a larger excursion capability. Of course the Scan ought to be better since it costs ~5 times more!
Paul

I was wandering around for other TL designs and found your winning Amarosos and canTiLenas. How would you expect the TL-Finalists to perform compared to them?
I wish there was something like the MWAF in Southern California so I could listen to all these great designs.......

[miyami]

Are the construction plans for the canTiLenas available somewhere ?

[Paul K.]

Sort of. I've attached a dimensioned cabinet drawing and can provide other information and photos. If you're interested in pursuing this further, please email me directly via the link on my profile page.

Are the construction plans for the canTiLenas available somewhere ?

[miyami]

Thank you Paul.

So I'm down to these two designs, the TL-Finalist, which should be a really fun project, and very interesting to see what the TL does with the very good design, or the canTiLenas, which of course reign in a different level if not already because of their price.

A quick consultation with the better half showed of course a strong preference for the smaller cabinet, but I am curious how the mid-range of the two designs would compare before making a decision. Of course we can discuss this in a theoretic way, but it would probably make sense to listen to them if possible.
So, did anybody in the LA area built either the Finialists from Jim Holtz or the canTiLenas from Paul and is willing to give a demonstration?

Paul, do you know of somebody who built your speakers over here?
I should probably ask this in a new thread to reach more people with this question....

[Paul K.]

Although a few people over the years have considered building the canTiLenas and communicated with me on them, I don't really know if anyone ever has. They are a bit expensive which makes them unsuitable for many budgets.
Paul

Thank you Paul.

So I'm down to these two designs, the TL-Finalist, which should be a really fun project, and very interesting to see what the TL does with the very good design, or the canTiLenas, which of course reign in a different level if not already because of their price.

A quick consultation with the better half showed of course a strong preference for the smaller cabinet, but I am curious how the mid-range of the two designs would compare before making a decision. Of course we can discuss this in a theoretic way, but it would probably make sense to listen to them if possible.
So, did anybody in the LA area built either the Finialists from Jim Holtz or the canTiLenas from Paul and is willing to give a demonstration?

Paul, do you know of somebody who built your speakers over here?
I should probably ask this in a new thread to reach more people with this question....

[miyami]

Is the round top of the canTiLenas part of the TL design, or could it be squared? With maybe two 45 degree corner plates?

[Paul K.]

You can definitely use 45-degree angled corners as you suggest or you could simply square the corners off. There will be minimally measurable effects on the TL design and crossover design, and neither will have any audible effects.
Paul

Is the round top of the canTiLenas part of the TL design, or could it be squared? With maybe two 45 degree corner plates?

[AlexanderTD]

Hello, i built DTQWT and been tuning/modifying it for over a year now to explore various options.
A lot can be said about DTQWT, but i think the most important things are these:
1) Their bass extension should not be underestimated. It easily goes to 35hz flat, with lowest frequencies i am able to "feel" are around 23-25hz.
Also there are ways to manipulate bass by tuning both horns as well as mass-loading the port to adjust bass to anyone's liking.
The bass itself is very fast and articulate and is closer to huge closed box than any bass-reflex.
2) High frequencies are excelent and very fast. Faster than many traditional tweeters on standard baffle. Highs are extended enough to go over my hearing limit (18khz)
3) Integration of drivers is excelent if you get it tuned right (see below) is as close to fillrage driver sound as i ever heard without it's typical limitations

I'll be making a page about it with review and various small problems solved during construction and tuning and post url later

Here's what i measures in room at 1,5m, more heavily suffed front horn, T35 variant, modified audax, Eminence bass drivers: (sligh measurement mic problem at highs)