DTQWT-12

[NorthBear]

Richdoo,

Thank you for your opinion and your deductible, while you describe your speakers


In the Meantime, you may attach pictures using the link "Additional Options..."Is
Do you recommanded to Troels GRAVENSEN? (Councils from him)

Read the following post: http://www.troelsgravesen.dk/download/TJL3W_Ingvar.pdf

''Following your advice on how to lower the level of the midband (1 ohm before the mid crossover and 47 ohm across its terminals) I must say the sonic result fulfills all my expectations. The treble, mid and bass are now wonderfully smooth integrated. The bass is clean and fast, articulate and deep. Overall, the sound is transparent and convincing. Ben Webster's tenor sax has never sounded warmer and more full-bodied to me from a pair of loudspeakers and I have never heard any loudspeaker reproduction of classical music more sweet and seductive. So thank you for inspiring me to build these wonderfully sounding speakers.
Kind Regards
Ingvar Bergman/Stockholm''

@+
NorthBear

[richidoo]

I have emailed with Troels about my speakers and he has posted a link to this thread from his website. His advice is very helpful. He provides excellent support to the builders of his kits.

Today I will finally be able to fix the posts and the tweeter.  I decided to order the Eichmann speaker posts as they will allow me to use my bananas and they have no metal threads, but I might change my mind.

[NorthBear]

Richidoo,

Have you seen my speakers on page 11?
Can you tell me the link where Troels advise you, please?

Best regards,
NorthBear

[richidoo]

Northbear, I'm sorry I did not see your speaker picture. Thanks for bumping it!  I like the color! Grape Ape


It looks like low distortion SEAS drivers in large volume with reflex alignment, and no separate bass drivers. More midrange accuracy, better audiophile tricks, bass down to ~40Hz. I think my bass goes down to about 30Hz and it is loud and punchy. I still have to measure it, but I know that the speaker cable connections will affect the bass volume (and clarity) so it must wait until I get that fixed.

Troels advised me by 4 emails. I will post them here.

[richidoo]

Email response from Troels dated 7/22/11. His comments are in BOLD

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

Hi Troels
I have the DTQWT-12s finished. They play low and powerfully, as promised. The tone of the mid/tweeter is awesome, and everything I hoped for. Open and alive, tone is full and satisfying, yet sharp on brass and violins where needed. Gorgeous and exciting sound. I am using the largest 2.7R tweeter resistor. Solo violins never sounded better!  Congratulations on a great design. There is not quite enough tweeter for the showoff audiophile recordings like 2L, Chesky, Reference, but for real music it is perfect. I might install a switch to choose the tweeter settings for showing off.
I'm pleased to read your comments. Yes, sadly we need tone controls on our pre-amps. Many recordings can be improved by +/- half a decibel of treble or bass level.
Lennart (Sweden) brought his amps here a couple of months ago and the tone controls were used extensively, in particular at low listening levels where bass needs a 1-2 dB boost on most recordings.

Mine have only 15 hours of playing so far, and have improved a lot from new. But more time is needed for the drivers and filters to burn in.  But I am hearing some resonance that is not changing and I am not sure whether it is break-in, acoustic damping or panel resonance. I have loosely packed acoustistuff line damping from the bottom of the rear bass horn up to the bottom edge of the bottom woofer, and the the front midrange horn is stuffed similarly, plus a small wads on the sides of the midrange up to height equal to the top edge of mid driver. I went light on the damping fluff because in previous projects I used too much and killed the life. Fortunately, this design allows adjustment after construction.

My question is about tone. I am getting a warm thick congested tonality from upper bass through the midrange, I would guess through the 100-800Hz range. I played the midrange/tweeter only with no woofers powered and still heard the excessive warmth to a lesser degree.  It seems like the very bottom two octaves up to 80Hz are pretty clear, but hard to tell for sure because I'm not sure what horn loaded bass should sound like, other than "good."  The distortion is worse with higher 90dB volume levels. At normal soft levels 80dB the resonance is not too bad, but midrange and upper bass tonality is still pretty colored.
Well, this is really hard to comment on without hearing and in particular measuring panels resonances.
You damping work sounds good and appears what I would do.

The cabinet is constructed of decent quality 18mm hardwood plywood, and front baffle is 2 layers 36mm. The mid section of the front baffle is made of strips of plywood turned on edge and laminated together for extra stiffness. Internal bracing matches your drawing. The entire inside of the speaker is lined with heavy (4kg/ m^2) rubberized bitumen. 10mm felt is applied over the bitumen in locations recommended in DTQWT.

Building saga and pictures unfolded here: http://www.audionervosa.com/index.php?topic=3070.msg
Looks impressive and I suggest trying this: If you have two large panels of e.g. 20-22 mm, add these to the sides and fasten with (lot of) clamps to hear if anything happens to the sound.
Next, the rear panel may not be the most rigid seen. 2 x 18 mm might have done well here. Hard to try out things here to hear if things may improve from thicker panels.
I would have used the same for rear as for front carrying two heavy 12" drivers.

Any suggestions how to improve the tonal clarity? I can thicken the exterior and/or add more stuffing, but I'm not sure which one to attack first.
Try out side panels first.
I'm hoping you are familiar with this problem from tuning DTQWT. Maybe the guy from Italy can reveal his stuffing or bracing secrets if he made it play cleanly. I know he used laminated baltic birch which is much stiffer. So if he had no resonance problem then I know I need to stiffen the panels. Can you send him my email address?
I'll forward you mail to Ferraioli.
best regards
Troels

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

In retrospect, my questions were written to Troels soon after completing the construction. The drivers have continued to burn in since then, until just a few weeks ago, improving all the time, especially bass clarity. I have also changed the stuffing about a dozen times since then, which has cured almost all of the ringing problems. Also, the speaker posts that come with the kit do not fit my JPS jumpers, so the jumpers were connected poorly, which really affected the sound in a negative way. That will be fully fixed with single Eichmann speaker posts per speaker and internal wiring to both crossovers, no jumpers. I will never biwire this speaker. Jantzen sent dual posts for free because I requested satin nickel finish but they were out of stock. I only wanted satin nickel because my wife ordered satin nickel hardware with our new house, and I wanted to give her a sarcastic nod. She could care less the color of the speaker posts. But then I made the mistake of using both pairs per speaker instead of just soldering the crossovers together for best connection. These speakers are intended to glorify SET tube amps, so the idea of putting SS amp on the bass and SET on the treble is heresy, and never works anyway, on any speaker it's tried. Vertical biamping should be the same amps, imo.

I am not yet ready to give final review of the sound, so you DTQWT12 prowlers don't read too deeply into my passing comments about sound quality during the tweaking process. They are written only to share with my AN friends "the thrill of victory and agony of defeat" through the process.

This is DIY, and I am an amateur builder. It is not to be expected that the speaker which even the designer never built or heard for himself just pops together into perfect tuning on the first try. Good commercial speakers take years to perfect, but there is no daily blog to scare away potential customers during the agony of defeats!

When I feel that I have squeezed all that I can from this design I will have another listening party and get more feedback. Then more changes, hopefully small and then I'll be close to the end. Unless I decide to build another sturdier and better damped cabinet for them.

Eventually I will write a review and summarize my experiences and the specific thiings I learned to help future builders. But they will not want it to sound just like mine, so they will still need to tweak their own.
Rich

[richidoo]

Email 2: Troels just writing to say he could not find Ferarrioli's email address, and to have a fun time at the upcoming meet.

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

Email 3:
Hi again,

Looking at the photos, I wondered if the 8008 is completely sealed off towards the center horn?

 

As can be seen on drawing, there is a piece of MDF panel sealing off the hole for the magnet.
If not completely sealed, the 8008 will not load the front horn properly and you may just glue two pieces of MDF to the front internal panel and the bracing.
There must be some distance from the magnet hole to the additional sealing panel in order to allow proper ventilation from the voice coil and dust cap cavity, preferably 10-15 mm and there should be some damping material behind the magnet too.
I guess I have to specify this more clearly.

best regards
Troels


I replied that the picture was of unglued parts layout. The hole is sealed with 1/8" masonite damped with 1/8" bitumen and a brace.  The hole was not stuffed with fluff though, so I added that.  It might have been a part of the changes that improved the sound since then. But I did not compare before and after I damped the mid driver vent.

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

Email 4: Troels just acknowledging my reply that the hole is sealed.

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

Tuning the horns is the main chore after building, and is the make or break factor in the sound. IMO, the cabinets are sufficiently braced and damped for this speaker's role, music listening with low power amps at moderate levels. But I don't hear any noticeable cabinet resonance even at high volumes that I can hear are pushing the midrange out of its comfort range - really loud. As for the rear panel, The rear drivers have aluminum frames screwed to the rear panel and grounded mechanically to the immovable perpendicular sidewalls. With that, there is NO significant mechanical vibration of the rear panel possible due to driver vibration. Further, the rear drivers are braced immediately below, between and immediately above the woofers. Acoustic pressure movement is possible in the bottom half of the horn below the 10" tall brace, but these drivers hardly move, that part of the horn is well stuffed, and the horn is expanding exhaust type so pressure wave energy mostly moves toward the exit so pressure fluctuations are really not an issue on the rear panel. Higher frequency resonance is damped with bitumen on all interior surfaces of the rear horn.

[NorthBear]

Richidoo,

I have not read everything carefully, but it seems  councils's Troels are similar to those of John  MAUER:
http://www.jeanmaurer.ch/Produits/Jm-technologie/techno-e-boitiers.htm
I'll read carefully and I contact you.

Give me your adress e-mail and I'll give you adresses of FERRAIOLI Pantaleone:   

@+
NorthBear  (Thanks for "my photo" !)

[richidoo]

Please invite Ferraioli to our little space here, and he can join us if he is still interested in the DTWT-12. Do you know if he still uses it? As far as I know he is the only other builder, but I could be wrong. I think it must sound great with his 50W Mastersound 845 amps.

Thanks
Rich

[NorthBear]

Richidoo,

Ok, I'll contact him.
Neodym Eminence DELTALITE®-II 2512
Usable Frequency Range  48Hz-4kHz
http://www.toutlehautparleur.com/deltalite/eminence-deltalite-ii-2512-p-3178.html

SEAS W21EX001
RECOMMENDED FREQUENCY RANGE 30-3000 Hz
VAS 63.8 Litres
http://www.toutlehautparleur.com/woofers/seas-w21ex001-e0004-p-3072.html

[NorthBear]

Dynaudio Esotar T300D (See doc attached)
Nominal Impedance (Znom): 8 Ohm
Voice coil diameter (dc): 28mm
DC Resistance (Re): 5.2 Ohm
Voice coil height (hc): 2.8mm
Voice Coil Inductance (Le): 0.07 mH
Voice coil layers (nc): 2
Resonance Frequency (fs): 750 Hz
Magnetic gap height  (hg):
2.5mm
Mechanical Q Factor (Qms): 0.33
Linear excursion: 0.3mm (peak to peak)
Electrical Q Factor (Qes): 0.5 Max.
Excursion: 3.2mm (peak to peak)
Total Q Factor (Qts): 0.2
Magnet weight (wm): 0.7 kg
Mechanical Resistance (Rms): kg/s Power Handling
Moving Mass (incld. air load,Mms):0.45 g
Nominal long term IEC: 130W (crossover dependent)
Suspension Compliance (Cms): - mm/N Transient (10ms): 1000W
Effective Dome Diameter (d): 31.3 mm Mechanical Properties
Effective Piston Area (Sd): 7.7 cm squared
Net Weight: 1.6 kg
Equivalent Volume (Vas): - l Overall dimension: 140.1 mm diameter x 66mm
Force Factor (Bl): 4.6 Tm
Recommended Frequency Range: 2000 – 30000 Hz
Overal Dimension: diameter: 140 x 66
90 dB sensivity  2.83V 20 - 200 watts continuous power handling.

http://www.gattiweb.com/dynaudio.html

[NorthBear]

Richidoo,

I've to send an e-mail to Leo (DTQWT-12)
Probably he join us !

Now I'll go to bed!
NorthBear

[richidoo]

Thanks Northbear. Good night

Why did you post the specs of your drivers in the DQTWT-12 thread? 

[richidoo]

I spent about 3 hours tonite with my hand jammed down into the bass horns to remove the 8 Dayton chinese crap speaker posts. When I installed them I did measure the distance to the closest woofer hole to make sure that my arm was long enough in case I had to access them, but didn't think it would be this quick! The bitumen has sand on the surface so it did a number on my hands.

Then I soldered the upper drivers' crossover input to the input of the bass crossover in parallel. Then I used a Radio Shack dual speaker post to connect the crossover input bare wires to the cables. So it is a much better connection now, no screw threads in the signal path, no washer tabs, no jumpers.

While I was in there I found the nuts holding the washer tab ring lugs not as tight as they were when I installed them. They can't take much torque or the thread strip, on either the shaft or the nut, I did both during install. I don't think they are even brass, they seem like whiter color base metal under the gold. These posts are definitely not good enough for a Jantzen kit when every other part is so great.

I also increased the tweeter resistor by another 1/2 ohm, to 3.7 now. It is better,  but it can still take even more pad. I will use two of the included Jantzen resistors 1.8 + 2.2 in series to bump it up to 4 ohms. It's funny, when you have too much treble, the detail becomes annoying and you block it out. As the treble level comes down into balance, you can relax and listen deeper and the detail seems to improve. A shoutyness around the crossover frequency also seems to be lessened by bigger pad, but still a little more to go there too.

I found some errant fluff in the bottom of one bass horn, I guess I didn't sort it carefully enough last time I was in there.

With all that, plus lasering the tweeters to perfect distance within 1/16" I sat down to listen to my audiophile test tracks playlist. I was pretty impressed with the overall improvement. It sounds much more audiophile-ish now. Bass is clearer. Midrange is much more intense and dense than before. That plus the eased off tweeters is bringing out a bit of an exciting musical personality. Hopefully more of that will emerge.

Imaging is improved a little. I think it will improve more when I round the sharp cabinet edges near the tweeter.

At very high volume there is still some high Q resonant midrange frequencies in the main center horn, 400-800, so that needs to be fixed. And there is still a bit of low mid resonance too, in certain places. So I hope I can improve those further. But at normal levels it is not a problem.

Overall a successful mission.

[NorthBear]

Richidoo,

Why did you post the specs of your drivers in the DQTWT-12 thread?
It looks like low distortion SEAS drivers in large volume with reflex alignment, and no separate bass drivers. More midrange accuracy, better audiophile tricks, bass down to ~40Hz.
I think my bass goes down to about 30Hz and it is loud and punchy.
I go down to 33 Hz with SEAS and I cut the DYNAUDIO to 2000Hz!
You tell me how much you go down with DTQWT.

As for the benefit of the mass, look at the SONUS FABER 3 / 4 on the following page:
http://www.magazine-audio.com/2011/munich-high-end-audio-2011-part-2/
They including 304 kilograms and cost ... 14 000 euros!

[NorthBear]

Richidoo,

Have you seen the speaker or ELIPSON or ETHER?
They were plaster ...
See the following document to understand the advantage of this material:
http://ww2.ac-poitiers.fr/techno/IMG/pdf/Sequence_4_synthese_Materiaux.pdf