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Another Troels Gravesen's DTQWT Project Build


Sierra

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Just beautiful work, Sierra.  The two-tone look does help to break up the look of what are quite large cabinets.  Looks very classy, too.

Troels' TQWT is on the short list for my next speaker up-grade.  I take it you would recommend them?  :D

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Just beautiful work, Sierra.  The two-tone look does help to break up the look of what are quite large cabinets.  Looks very

classy, too.

Troels' TQWT is on the short list for my next speaker up-grade.  I take it you would recommend them?  :D

 

 

Thanks RoHo!

 

That was my thoughts too in going with the contasting timber colors as the cabinets are rather large.

When I originaly decided on building these speakers buzz lightyear kindly invited me over to have a listen to his DTQWT's.

When I saw them in real life I thought "damn these things are huge" I didn't expect them to as big as they were.

 

Yeah ... it's a pretty safe assumption that I would recomend them :)

So you are looking at building the original TQWT?

 

 

 

 

Well done.

 

Enjoy the fruits of your efforts.

 

We will be interested in your observations

 

Dont let a year pass before you comment!

 

have fun

 

Adam

Thanks Adam ... I'm enjoying ... trust me :)

 

 

Oh if you really insist on some observations ... LOL

 

These things are a lovely sounding speaker...

They image very well and throw a wide and deep sound stage.

Musically they are very engaging with great detail in the midrange and the highs.

Vocals are very smooth with great body and the realism of the various instruments really shine through.

You find yourself listening to the music and the speakers just tend to disapear.

Bass is detailed, taught and powerful and not boomy or over emphasised ... though limited to 40hz by design.

 

Remember they are a high efficiancy (95db) speaker designed specifically to be driven by low output SET type valve amps.

If you are after gut wrenching ground shaking 20hz or lower Bass then you would need to add a sub.

 

 

 

Well done- Sierra, quality craftsmanship!  :thumb:

And the more you put in - the sweeter it sounds

Cheers, Clive.

 

 

Cheers Clive.

 

DIY just gives so much satisfaction ... during the build, having it all take shape ... and when it's all finished you get to enjoy the fruits of your labour.

 

Hmmm ... they do sound very sweet :)

 

Plus "bang for buck" just can't be beaten with DIY!

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Excellent work, Sierra. My speakers are still only some raw drivers and WinISD plots - Checking up on these finished products makes me want mine even more...

 

Thanks BV

 

You might have to re-adjust the priority of your speakers in relation to all your other projects and move them up the ladder :)

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Very attractive end result, Sierra, Congratulations!

 

The feet complement all the other aspects of your design, including colour and feeling of solidness. I take it you are using the 70mm ones?

 

With regard to the "limited to 40hz by design" in Post #204, I'd be interested to know what you hear from Track 12 of the Zimerman/Ravel Left Hand Piano Concerto CD. The contra bassoon starts at 10", and at 28" goes down to a bottom C, which according to my chart is 32.7 Hz. I would expect room gain, and/or slow roll-off, to give you a reasonable reproduction. I know mine are a bit different from yours, but I've found using a sub doesn't help, and the bass is a lot better in reality than the theory would suggest. I'm currently looking forward to the arrival of "Omnimic v2", so I can get a more tangible understanding.

 

The brass spikes turned out smaller than I imagined from the photos: just right for your carpet. Looks like you could safely 'walk' the speakers around on them without damage (to anything).

 

You might need to unscrew the JA8008s occasionally to check the baffles for the "Onatopp effect". (Xenia Onatopp was the Bond girl who so memorably crushed Pierce Brosnan between her thighs in 'Goldeneye').

 

So I take it your "final instalment" can be taken loosely, and this project will keep us engaged a bit longer? What would we all do without it now? Let us know how it goes when you move the old ones (don't ruin yourself moving those Brontosaurus-BBQ-plate stands) and put the DTQWTs in their final exhibition space.

Edited by BioBrian
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Very attractive end result, Sierra, Congratulations!

 

The feet complement all the other aspects of your design, including colour and feeling of solidness. I take it you are using the 70mm ones?

 

With regard to the "limited to 40hz by design" in Post #204, I'd be interested to know what you hear from Track 12 of the Zimerman/Ravel Left Hand Piano Concerto CD. The contra bassoon starts at 10", and at 28" goes down to a bottom C, which according to my chart is 32.7 Hz. I would expect room gain, and/or slow roll-off, to give you a reasonable reproduction. I know mine are a bit different from yours, but I've found using a sub doesn't help, and the bass is a lot better in reality than the theory would suggest. I'm currently looking forward to the arrival of "Omnimic v2", so I can get a more tangible understanding.

 

The brass spikes turned out smaller than I imagined from the photos: just right for your carpet. Looks like you could safely 'walk' the speakers around on them without damage (to anything).

 

You might need to unscrew the JA8008s occasionally to check the baffles for the "Onatopp effect". (Xenia Onatopp was the Bond girl who so memorably crushed Pierce Brosnan between her thighs in 'Goldeneye').

 

So I take it your "final instalment" can be taken loosely, and this project will keep us engaged a bit longer? What would we all do without it now? Let us know how it goes when you move the old ones (don't ruin yourself moving those Brontosaurus-BBQ-plate stands) and put the DTQWTs in their final exhibition space.

 

Cheers Brian  :thumb:

 

The feet and the mounting plate assembly are what gave me the biggest headaches during this build.

I wasn't a big fan of the feet that Troel's used on his prototype and as you well know I had a number of different ideas floating around before finally settling on this configuration.

I'm using the 45mm versions and I doubt I will even try the 70mm ones.

Firstly ... I think asthetically the 70mm ones would look "out of proportion" like it was on stilts ...and secondly it would elevate the cabinets too much as I would like to keep the centre line of the tweeter close to eye level when seated in the listening position.

 

As far as how low they actually play (40hz or lower) I really havent had a chance find out. When I get the opportunity to listen to the Zimerman/Ravel Piano Concerto CD I'll pay carefull attention to that contra bassoon and let you know how it plays.

I'll be curious myself to find out how low they actually play (obviously not as low as yours) ... it's just getting the opportunity to spend a few afternoons on weekends listening that is proving difficult.

 

The brass spikes would be smaller than you imagined ... because they are a lot smaller (shorter) than the ones that I had originally looked at and posted pictures of in previous pages.

Again the smaller spikes were to try and keep the cabinet overall height low ... they are just long enough to pierce the carpet and sit on the concrete slab and still give a few millimeters clearance between the top of the carpet and the base.

I don't think I'll be "walking" the speakers around on the spikes ... it's easy to remove the spikes (lay the cabinet down and unscrew them) and then "slide" the speaker to the desired position before replacing the spikes again.

 

As you know there are plenty of "tweaks" for these things ... and I do want to try some of those "ridiculously expensive" caps in the crossovers at some point ... so "final installment" could well be taken loosely :P

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  • 2 weeks later...

Speaking of Tweaks, I've just finished Tweak II, with the felt discs to cut too much mid emanating from the Eminences at the back.

 

post-135890-0-19538400-1375928669_thumb.

 

12 mm Baltic Birch, 12 mm slits, on 25 mm centres. Spacers 22 mm long, from 25 mm pine dowel. 12 mm felt, glued with PVA.

 

It's certainly helped reduce reflection from the wall behind, so it's a success, at least in my smallish room. Need a lot more listening time. I've done listening tests with the front speakers disconnected, which is a bit surreal; the difference with and without Tweak II is big, and with the front drivers connected again, they seem to express themselves with more clarity.

 

I've also done the "not-upgrade" of the crossovers, according to the "T35 option". Same Audax tweeters for now, but still running in the components. Now have a sad pile of bits looking for a new job, but I did notice that the Cyclop crossover can use the coils. You might notice the green (Cyclop) M15CH002 test cab in the background: I hope this can help sort my "Vifa kit problem".

 

With the flute problem I've mentioned, I took the offending CDs to a friend's and played them through 2 different valve amps and 2 very different pairs of speakers. Great news is that they showed the same distortion on his system, so the DTQWTs are not guilty!! I feel like I can enjoy them even more now - great relief.

 

It's interesting that after having just listened a whole Ravel movement with just the damped woofers, and then the same with front drivers connected again, that the bass is actually enhanced and much more solid, with the front woofer driving the shared inner horn. It's such a clever design.

 

Cheers all.

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Hey Brian,

Nice work with the rear damping ... great job of routering the slots ... how long did it take you to make those panels?

How close to a back wall or to a corner of the room are the speakers normally placed?

And the difference is really noticable eh ... more than just a subtle change then?

Geez ... you've really gone to town with the tweaks ... doing the crossover mod as well ... :)

Have you got any initial thoughts on the modified crossover point ... has it made much of a difference or too early to tell?

Did you do both tweaks at the same time or was the damping done some time prior to the crossover mod?

Be interesting to get your thoughts on the change ... and if you will go the whole way and replace the TW034 with the T35.

Good news that you finaly confirmed the flute problem was not the speakers ... I know it was driving you nuts thinking it could be the speakers.

Now you can get back to just enjoying your music :)

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Thanks, Sierra. I think Troels was right when he said this way of doing it looks good, better than a frame and grille cloth.

 

But at what price?? It took 11 hours, over 9 days, including a lot of filling, sanding, and painting. I know they're only on the back, but that's beside the point, isn't it? Routing isn't a perfect art yet for me. I made a special jig to clamp on the plywood panels: this set the beginning and end of each cut, and gave a straight edge to run along, but that at best only reduced the variables! Baltic Birch, cross grain... "Now when I get to this end, which way does the router want to jump?" 52 slots. 52 slots. 52 slots. One slip and it's start again. Stressful.

 

I haven't had time for extended listening tests yet, but my speakers have to be fairly close to the front wall (300-400 mm), and are rather boxed in, especially on one side. So the felt pads are an improvement. The big difference I spoke of was when the front drivers were disconnected, and I could play a track with, and without, the grilles. I'm really looking forward to a bigger room, and also to try them in a relatively open space, like a hall, or Valentin's house on Troels' website. Then it might be appropriate to remove the grilles.

 

You were spot on when you asked about doing 2 tweaks together. I had just soldered up the crossover changes the day before, so had that to listen for as well, so the experiences of both were a little lost.

 

Yes, I have decided to go the whole hog, and the SEAS T35 tweeters are being ordered. Troels says the 2 tweeters are "too similar", but popular conception is that new is better: the Audax can't be good because they were designed before yesterday! They actually have much better HF (and LF!) response than the 19 mm Vifa ones in my other project, so that's where they're headed. The real difference in the "T35 option" is a lower point of crossover: from 3000 to 2100 Hz, from what I can gather. This takes away a bit of hard work for the 8" JA8008, which is already doing service unhindered right down to the bottom end. Both these options are, I suppose, what keeps these speakers in the audiophile arena, rather than party or PA speakers. The OBL-11 open baffle version cuts the low bass to the JA8008, and keeps the tweeter crossover point high, so it can be fed a fair bit more power without damage.

 

I tried the 1 Ohm series resistor (here we go again) for the tweeter, and it was very bright, so now it's being tried on 1.5 Ohm. I didn't want to make too much mess un-sticking glue, so left the old resistors on the crossover board - now there are 5 choices! I might end up with the 1.8 Ohm, which Troels leaves out in the T35 option, skipping straight to 2.2. The new tweeters might call for something else again. It's going to be a bit heart-in-mouth drilling and tapping 4 mm holes, only 5 mm deep, in the wave-guides.

Edited by BioBrian
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  • 1 month later...

OK Sierra, here we go. I was tempted to say "not until you reply to the question in post #207", but you might have been not listening to your speakers  ;), so I'll be patient.

 

My last post, #213, dealt with only half of Troels' T35 option, where I kept the Audax tweeter, but changed the crossover to the new configuration. This brought the crossover frequency from 3000 down to 2100 Hz. In actual sound terms, this is only half an octave lower - an augmented 4th for the musicians out there - in the piano's top octave, it's about F# down to C. So not a big deal, but it's obviously a fairer sharing of work between the 8" JA8008 and the 34mm tweeter. With the attenuation resistor, I started at 1 Ohm; 1.5 Ohm was heaps better, and settled on 1.8 Ohm. Very happy.

 

This period was all a bit clouded by my developing sensitivity to flutes, which seem to make themselves particularly ugly in the 600-1000 Hz area, but this has been further settled by hearing more live orchestral concerts, where they sound equally offensive! It's become a form of therapy for me, learning to forgive those who know not what they do (to me).

 

The new SEAS T35s went in on Aug 24, so I've had a reasonable time to listen. My first impressions were that it all seemed really thin, but of course all new drivers do that, and I'd also started with the lowest attenuation resistor, giving the highest tweeter priority. These SEAS tweeters are 2 dB more sensitive than the Audax ones (95 versus 93 dB), but the new crossover has a 1 Ohm resistor after the 2nd Order part, which might take care of that (only an uninformed guess there). So the upshot is that I'd settled again on 1.8 Ohms, as this gave me back some of the fruitiness I'd enjoyed from the original set-up.

 

Just to make this a bit more useful though, tonight I tried the 2.2 Ohm option, but quickly decided that it dulled the treble too much, made the bass too woofy, and made me panic about getting upper-frequency hearing loss! So we're back on 1.8 Ohms, same as what I'd settled on for both the original, and the half-baked change.

 

I have to honestly say that I can't be accurate in saying whether this T35 option is much of an improvement. It's SO hard to remember all the different aspects of sounds! The original 'fruity' sound is quite delicious, and the new one is maybe more accurate-sounding(?), but not really $600-700 worth, I just can't tell. Let's just say that I won't be bothered changing back. I'd also recommend not bothering to order the 1.0, 1.5, and 2.7 Ohm resistors. 1.8 or 2.2, or something in between, should make anybody happy.

 

Another thing I was obliged to test tonight was the tweeter phase. One of the T35s had no red dot! I just used the position of the model-number-sticker as a guide, and it seems it was the lucky guess. I've put the speakers together and stuck my head between, and tried music, and various sine-wave signals, and am convinced that if the phase was wrong, I'd know about it.

 

Oh yeah - the hole tapping thing. As you'd imagine, routing new (pre-drilled) wave-guides, with the big speaker holes already there, would be next to impossible, so short of making new baffles, I decided fitting the T35 to the old wave-guides WAS going to work. Luckily they are thick enough to do a test-hole or 2 in the back, so I did this, and it worked. You need a 4 mm x 0.7 mm 'bottoming' tap, and in the soft plastic I found a 3 mm pilot hole was fine. It needs a good, constant pressure, and of course with such a fine thread, any deviation from the vertical is fatal. As Troels says, you can only drill 5 mm before shooting out the other side.The face-plate the T35 comes with is metal, and the bolts only project about 2.7 mm into it, so screwing into the plastic needs to be done with great delicacy.

 

My worst fear was damaging the dome while doing all this, so after a bit of Googling, I decided to try a couple of dobs of 5-minute epoxy to locate the tweeters centrally on the wave-guides, and give my stress levels a break. The next day they were firm enough to move around, although a bit of surplus glue peeled off quite easily. Luckily the glue holds to this day, and would even help stop resonance that might have otherwise occurred. (I noticed that when I took the Audax drivers off the wave-guides, where the screws had gone in, they had expanded the plastic to the point of separating the driver from the wave-guide, so I'd advise countersinking the holes a little to avoid this!)

 

So there you go. Is that enough detail? :)  You'll never know until you try it, but don't get too excited. I am led to believe there's someone else in Oz who's doing the T35 thing, so maybe we'll get lucky with another opinion soon.

 

Enjoy your music!

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Hi Brian ... That's a hugely detailed reply Thanks heaps!

 

I did try your test on #207 ... but it seemed to be a strange kind of note ... I dont really know what a contra basson should sound like so have nothing to compare to.

 

I might run some test tones from 50hz down to 30hz and see how the response goes with those.

 

I really have to thank you for taking the chance and doing this mod ... not only for me but for other DTQWT owners/constructors as well.

As Troels puts it ... the sound is different ... weather it is better or not is up to the individual to decide.

 

Now after hearing your opinion on the mod I am less in a hurry to try it myself as I really like how they sound now.

That's not to say that I won't ever try the mod ... but it will be a little bit further down the track for me now.

 

My next priority is to sort out my phono stage and then do some turntable mods ... once I have those things sorted and I can enjoy my vinyl again then I might revisit the DTQWT.

 

But for now ... as you so rightly put it ... I'm enjoying my music!

 

As I hope you are enjoying yours too!

 

 

 

 

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Hi Sierra & Brian,

Any opinion on which tweeter to go for with a new build?
It doesn't sound like there's much difference between the two, though the T35 using a slightly simpler crossover and the predrilled waveguide might be easier? . . . or not?

Congratulations on the builds, by the way.
Very impressive.

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Thanks, Dustin, all encouragement gratefully received!

 

I'd have to say that the T35 Option would be the one to go for. Some comments:

 

It'll always bug you if you don't...

 

The pre-drilled wave-guide thing you mentioned would make life A LOT easier. (I'd even try to find some 4 mm bolts about 2 mm longer than the originals, even if you have to cut down longer ones).

 

The crossover for the T35 might cost a bit more, with the pre-drilling, bigger coils, and the bigger (12 uF) caps. Not sure about the tweeter costs. Jantzen don't hand out individual prices, in my experience.

 

On paper the T35 looks better to me: a nicer curve. I found it hard to find an Audax datasheet, but the Madisound site had one. It shows a peak about 15 kHz, which could actually be good for those of us with a mature-age natural roll-off in that region! The impedance curve fooled me for a while, because the scaling is very different in each graph. They are almost identical, between 5 and 16 Ohms, except that the T35's peak is at about 600 Hz, to the Audax's 800. Well below significant though, I would think. But the Audax does have a dip around 2.1 kHz, the crossover frequency, and a corresponding ripple in the impedance there too. Note that Troels thought it necessary to do a very difficult modification to the Audax tweeters for this lower crossover point. Sorry, you probably know all that!

 

If you later wanted to try the Audax version, there'll probably be a fair few bits available 2nd hand, is my guess.

 

I think, either way, the main problem is that it's a bit hard to improve on perfection, but I might be a bit biased :love .

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[...]

 

It'll always bug you if you don't...

 

[...]

 

 

Good point . . . I think you have it in one!

Mature age is right for me too, so I probably wouldn't hear any difference anyway.

No, I wasn't aware of the difficult modification for the Audax tweeters, but I'm rather a noob in all of this. I'm really placing my trust in a well respected guy like Troels.

Many thanks for your thoughts.

I really should get the kit from Jantzen before the exchange rate falls through the floor!

Cheers. :)

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  • 3 weeks later...


How did you go Dustin ... have you bought that kit from Jantzen yet?

 

Hi Sierra,

Nah . . haven't bought the Jantzen kit yet.

The timetable for me will be a little extended as I've got a house move on the books and all that goes with that.

I have bought the woofers though . . . shsssssh . . ;)

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  • 2 weeks later...

OK Sierra, here we go. I was tempted to say "not until you reply to the question in post #207", but you might have been not listening to your speakers  ;), so I'll be patient.

 

My last post, #213, dealt with only half of Troels' T35 option, where I kept the Audax tweeter, but changed the crossover to the new configuration. This brought the crossover frequency from 3000 down to 2100 Hz. In actual sound terms, this is only half an octave lower - an augmented 4th for the musicians out there - in the piano's top octave, it's about F# down to C. So not a big deal, but it's obviously a fairer sharing of work between the 8" JA8008 and the 34mm tweeter. With the attenuation resistor, I started at 1 Ohm; 1.5 Ohm was heaps better, and settled on 1.8 Ohm. Very happy.

 

This period was all a bit clouded by my developing sensitivity to flutes, which seem to make themselves particularly ugly in the 600-1000 Hz area, but this has been further settled by hearing more live orchestral concerts, where they sound equally offensive! It's become a form of therapy for me, learning to forgive those who know not what they do (to me).

 

The new SEAS T35s went in on Aug 24, so I've had a reasonable time to listen. My first impressions were that it all seemed really thin, but of course all new drivers do that, and I'd also started with the lowest attenuation resistor, giving the highest tweeter priority. These SEAS tweeters are 2 dB more sensitive than the Audax ones (95 versus 93 dB), but the new crossover has a 1 Ohm resistor after the 2nd Order part, which might take care of that (only an uninformed guess there). So the upshot is that I'd settled again on 1.8 Ohms, as this gave me back some of the fruitiness I'd enjoyed from the original set-up.

 

Just to make this a bit more useful though, tonight I tried the 2.2 Ohm option, but quickly decided that it dulled the treble too much, made the bass too woofy, and made me panic about getting upper-frequency hearing loss! So we're back on 1.8 Ohms, same as what I'd settled on for both the original, and the half-baked change.

 

I have to honestly say that I can't be accurate in saying whether this T35 option is much of an improvement. It's SO hard to remember all the different aspects of sounds! The original 'fruity' sound is quite delicious, and the new one is maybe more accurate-sounding(?), but not really $600-700 worth, I just can't tell. Let's just say that I won't be bothered changing back. I'd also recommend not bothering to order the 1.0, 1.5, and 2.7 Ohm resistors. 1.8 or 2.2, or something in between, should make anybody happy.

 

Another thing I was obliged to test tonight was the tweeter phase. One of the T35s had no red dot! I just used the position of the model-number-sticker as a guide, and it seems it was the lucky guess. I've put the speakers together and stuck my head between, and tried music, and various sine-wave signals, and am convinced that if the phase was wrong, I'd know about it.

 

Oh yeah - the hole tapping thing. As you'd imagine, routing new (pre-drilled) wave-guides, with the big speaker holes already there, would be next to impossible, so short of making new baffles, I decided fitting the T35 to the old wave-guides WAS going to work. Luckily they are thick enough to do a test-hole or 2 in the back, so I did this, and it worked. You need a 4 mm x 0.7 mm 'bottoming' tap, and in the soft plastic I found a 3 mm pilot hole was fine. It needs a good, constant pressure, and of course with such a fine thread, any deviation from the vertical is fatal. As Troels says, you can only drill 5 mm before shooting out the other side.The face-plate the T35 comes with is metal, and the bolts only project about 2.7 mm into it, so screwing into the plastic needs to be done with great delicacy.

 

My worst fear was damaging the dome while doing all this, so after a bit of Googling, I decided to try a couple of dobs of 5-minute epoxy to locate the tweeters centrally on the wave-guides, and give my stress levels a break. The next day they were firm enough to move around, although a bit of surplus glue peeled off quite easily. Luckily the glue holds to this day, and would even help stop resonance that might have otherwise occurred. (I noticed that when I took the Audax drivers off the wave-guides, where the screws had gone in, they had expanded the plastic to the point of separating the driver from the wave-guide, so I'd advise countersinking the holes a little to avoid this!)

 

So there you go. Is that enough detail? :)  You'll never know until you try it, but don't get too excited. I am led to believe there's someone else in Oz who's doing the T35 thing, so maybe we'll get lucky with another opinion soon.

 

Enjoy your music!

Hi to all.

 

This is my first post on Your site and i'd like say halo from Poland :)

I've build  DTQWT a year ago , and now just chanded crossover to option t35 , and i must say i dont like it . I fell  like i lost someting , vocals are weak and thin , and speaker now sound ordynary  , small . Lucky i did not buy T35  . I think i will go back to option MKII

post-140135-0-73328600-1385326890_thumb.

Edited by kocurmarcin
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Welcome to Stereonet kocurmarcin,

 

Nice job with your DTQWT ... they look great.

 

Seems like changing the crossover without changing the tweeter is not a good combination.
You could take a chance and try the Seas tweeter ... you've come this far ... you may as well go all the way ... you might like the complete option 35 version.  :)

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Well , i changed crossover it doesnt  cost that much , and gave me taste what the sound would be like , now i dont fell like spending another 400 euro for tweeters. I think there wont be any significant improvement from it .  Troels say :

The T35 does not sound anything different from the TW034 dome; in that respect they're too alike-

It has to be said the TW034 can be used un-modified with the same T35 crossover with a minor dip around 2 kHz but it's no big deal - if audible at all.

 

So if i liked T35 crossover I would go for Seas tweeter , for now i stay a while with crossover only and one day is will go back to  MKII  .

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