Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

[davepellegrene]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

Dave,

Do you notice a difference in the clarity of the sound? That individual sounds are easier to pick out?

I noticed a lot of things that were improved upon as soon as I started listening. The two you mention are among them. Better instrument separation, more 3D imaging and much more realistic sound. Unfortunately I'm not sure why. Is it the 12" woofer, the double waveguide, the dome mid, the Audax tweeter, the light weight cabinets or the controlled directivity. Probably a mix of all of them. They are also very dynamic. Probably from the high efficiency along with the 12" woofer.

During my listening to individual drivers I found I was crossing the TB 75 to low with the 11x6 guide. When I would turn up the volume I would hear, hard to explain, but kind of like a megaphone effect. It was an uncomfortable sound. Just raising the the crossover 100 dbs, going stepper on the crossover slope and filling back in with the Deltalite removed it.

The issue I was having between the Deltalite and the TB75 seems to be a phase issue. I don't quite under stand what was going on but I was getting cancelation above the crossover point. Lowering the slopes on the Deltalite did not get ride of it and raising it would boost above this point before it would the cancellation. The odd thing was PCD was not showing this. It was showing a 3 db boost in that area. When I flipped the polarity the cancellation disappeared. When I flip the polarity in PCD I get a reverse null. I'm now running with all three drivers the same polarity. I originally had the tweeter and mid flipped. I still need to laminate the cabinet so when I open it up I'll check to make sure I didn't switch the polarity on the drivers. Even if I had it should still have matched the FR in PCD just opposite.

Originally I had the tweeter/ mid crossover at 2.2 kHz and had it as low as 1.8 and the Audax sounded good at hi volume at either spot. It just ended up at 2 kHz.

I have the speakers toed in just in front of my listening position and I can lean left or right as far as I can, without falling out of my chair, and the image stays stable. Not quite as pin point but pretty descent. The thing I like the most from these speakers is the dynamics. the 12" Deltalite seams much smoother then the 8" B&C that I've worked with. Hard to explain other then it just seems to be a little softer sounding which I like since I'm use to hi fi woofers. The Deltalite plays pretty low but adding a sub makes a big difference. I've been running my Dayton RSS265HF in a 1 sq. ft. Box with a 250 watt dayton plate amp and it seems to be keeping up just fine.

I have a total 10 parts in the crossover. Two on the woofer, four on the tweeter and four on the mid. I'm running just a one ohm resister before the crossover on the mid and just a 3 ohm resister parallel across the tweeter. I've not tested how loud they will go yet but so far I haven't needed to.

Dave

[davepellegrene]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

Dave, awesome design work. Will you be entering any of the upcoming DIY
events. Also on the torch down roofing material,why the small width on the strips? I have
a similiar product used for flashing that has a PSA, do you think this would give the same
end result as you are getting with your procedure?

I plan to take these to InDIYana. I wasn't sure if they would be ready but it looks pretty good now. I may go to Dayton with them but I need to see if it interferes with my waterski tournaments this year.

I only used a small strip on these because I wanted solid contact between the two 1/4" layers so the wall would form a solid structure. I figured if the thin panel would resonate between the bracing the strip would help. It is melted into the wood really well. I think the bond is the most important. I was also trying to keep the weight down. These cabinets are 15"x15"x27" with 1" walls and 2-1/4" thick baffles and weigh in at 50lbs with drivers. I was concerned with the larger woofer with this style of construction but even at high volume there is very little vibration in them. I'm sure it helps not playing much below 60 Hz.

The product you mention that is used for flashing would work as a viscoelastic layer but it would need to be sandwiched tight with a good bond. I don't think it has enough adhesion on its own. It's designed more for nail penetration and will seal around it to stop water from getting through.

Dave

[Squidspeak]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

I plan to take these to InDIYana. I wasn't sure if they would be ready but it looks pretty good now. I may go to Dayton with them but I need to see if it interferes with my waterski tournaments this year.

I only used a small strip on these because I wanted solid contact between the two 1/4" layers so the wall would form a solid structure. I figured if the thin panel would resonate between the bracing the strip would help. It is melted into the wood really well. I think the bond is the most important. I was also trying to keep the weight down. These cabinets are 15"x15"x27" with 1" walls and 2-1/4" thick baffles and weigh in at 50lbs with drivers. I was concerned with the larger woofer with this style of construction but even at high volume there is very little vibration in them. I'm sure it helps not playing much below 60 Hz.

The product you mention that is used for flashing would work as a viscoelastic layer but it would need to be sandwiched tight with a good bond. I don't think it has enough adhesion on its own. It's designed more for nail penetration and will seal around it to stop water from getting through.

Dave

Dave thanks for the info,When I asked about the "thin strip" I was refering to
the width of the torch down roofing. Why not fill the full space was my thought.
Thanks Mike

[davepellegrene]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

Dave thanks for the info,When I asked about the "thin strip" I was refering to
the width of the torch down roofing. Why not fill the full space was my thought.
Thanks Mike

With the space only being 5/8" deep I wanted to allow as much room as possible for the ridged fiberglass and also keeping weight down. I don't think it matters all that much either way.
Dave

[Pallas]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

I finally took a me day and worked on the crossovers and have them pretty well dialed in.
Crossovers at 750 and 2 kHz.

0-90 Horizontal 1 meter on axis with tweeter 5ms gating 1/48 octave smoothing

That's an actual measurement and not a model?

Wow. Just completely outstanding. Hats off, Dave.

Also, are you using those four pieces of wood behind the woofer to clamp it down to the baffle instead of screwing it in directly?

[Pete Schumacher]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

That is impressive Dave. Very smooth response with such a spartan XO!

I have to think that pushing the TB a little higher up might just take care of the distortion bump at 1500Hz, and maybe reduce that small flare in the response at that point. Even so, the amount of distortion at 97dB is still only hovering around 1%, not too shabby!

[davepellegrene]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

That's an actual measurement and not a model?

Wow. Just completely outstanding. Hats off, Dave.

Also, are you using those four pieces of wood behind the woofer to clamp it down to the baffle instead of screwing it in directly?

Those are actual measurements and yes those are blocks made to clamp the woofer in. I clamped them in because the woofers are set into the baffle with only a 1/4" lip left on the front side. I did this to keep the acoustic centers as close as possible.

Dave

[davepellegrene]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

That is impressive Dave. Very smooth response with such a spartan XO!

I have to think that pushing the TB a little higher up might just take care of the distortion bump at 1500Hz, and maybe reduce that small flare in the response at that point. Even so, the amount of distortion at 97dB is still only hovering around 1%, not too shabby!

I'll experiment with it. I did have them crossed at 2.2kHz and I really don't hear a difference. I took those distortion measurements just before posting so did not know the THD and second order had that rise. I hadn't tied the hump at 1.5 kHz to the distortion. That will be interesting to see if moving the crossover up will fix that.

Thanks

Dave

[TN Allen]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

Dave,

It's great you're working with midrange guides, these have great potential, and may even be more important than tweeter guides. I have been told that one reason the Bose Wave radio/CD player(which, as I understand it uses waveguides) sells so well is that older people with compromised hearing can clearly hear the music. The combination of a mid and tweeter waveguide focuses the sound more effectively, or perhaps more realistically, reduces room effect and cross talk din that diminishes clarity. But what you're doing will likely enhance music listening for anyone.

You might consider some quick experiments with inexpensive drivers in 2 way systems that will work with a single capacitor on the tweeter, and a small woofer/midrange that rolls off naturally, or only requires a single coil. The results might be striking. Inexpensive drivers might sound remarkable in double waveguides.

No doubt you'll develop some new ways to test, and/or interpret the data you generate. Waveguides challenge conventional speaker baffle and cabinet design and building wisdom, and suggest looking beyond the rectangular box; very few natural sound systems come in flat and rectangular configurations.

It's great that you are pushing the envelope, and thinking outside the box, as is said of people who think beyond the conventional; good luck, it looks like you're on the cusp of some interesting discoveries and profitable business opportunities.

tna

[Pete Schumacher]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

I'll experiment with it. I did have them crossed at 2.2kHz and I really don't hear a difference. I took those distortion measurements just before posting so did not know the THD and second order had that rise. I hadn't tied the hump at 1.5 kHz to the distortion. That will be interesting to see if moving the crossover up will fix that.

Thanks

Dave

The rise in distortion points to the tweeter to me. In your original plot of the TB mid at the beginning of the thread, the mid has the very low distortion that it is known for. The hump in response at 1500Hz also points to the tweeter to me. Pushing the crossover a little higher will probably produce a better directivity match between mid and tweeter. I'd not go any higher than 2500Hz though.

[davepellegrene]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

Dave,

It's great you're working with midrange guides, these have great potential, and may even be more important than tweeter guides. I have been told that one reason the Bose Wave radio/CD player(which, as I understand it uses waveguides) sells so well is that older people with compromised hearing can clearly hear the music. The combination of a mid and tweeter waveguide focuses the sound more effectively, or perhaps more realistically, reduces room effect and cross talk din that diminishes clarity. But what you're doing will likely enhance music listening for anyone.

You might consider some quick experiments with inexpensive drivers in 2 way systems that will work with a single capacitor on the tweeter, and a small woofer/midrange that rolls off naturally, or only requires a single coil. The results might be striking. Inexpensive drivers might sound remarkable in double waveguides.

No doubt you'll develop some new ways to test, and/or interpret the data you generate. Waveguides challenge conventional speaker baffle and cabinet design and building wisdom, and suggest looking beyond the rectangular box; very few natural sound systems come in flat and rectangular configurations.

It's great that you are pushing the envelope, and thinking outside the box, as is said of people who think beyond the conventional; good luck, it looks like you're on the cusp of some interesting discoveries and profitable business opportunities.

tna

There are so many directions that I can take the waveguides. It's hard to decide which way to go. Time for testing has been so limited. I have two tweeters that were sent to me almost a month ago for testing that I have not been able to get to yet and I still have the 8" two way with the AST2560 to get to. Anyway, I've got someone interested in a smaller version of the combo guide, with the TB75, that can be crossed to an 8" woofer so I plan to get that worked on soon. I may eventually do some testing with a cone mid in a combo guide soon. I should be able to fit it to my existing one. At the moment I don't have a three inch available and am not sure what to even look for at this time.


Dave

[davepellegrene]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

The rise in distortion points to the tweeter to me. In your original plot of the TB mid at the beginning of the thread, the mid has the very low distortion that it is known for. The hump in response at 1500Hz also points to the tweeter to me. Pushing the crossover a little higher will probably produce a better directivity match between mid and tweeter. I'd not go any higher than 2500Hz though.

I did some modeling yesterday that moved the crossover point up to 2500 Hz. Changing the coil on the low pass seems to have reduced the hump at 1.5 kHz.

I went back and looked at some distortion plots on the Audax.
Distortion is pretty good until about 95 dbs.
This is in the 11x6 guide and it shows pretty much what we are looking at above. So I think your spot on.



Dave

[Greggo]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

Looking good Dave. Still a big fan of this project, and an even bigger fan of the potential derivative work if that is still on the calendar. Do you think the TB75 could go lower with a steeper slope and still provide very clean high SPL? Just wondering if the 750 Hz was as low as you wanted to take it or just a point that matched up well with sims against the DeltaLite? I am tempted to fly out to MWAF if you end up going because I really want to hear these things. My big dreams are still holding out for a 12x8 AST2560, a 12x8 slightly squared up for the TB75, and then I am currently thinking a pair of Beyma BR60v2 for the bottom end. All digital active of course, so that is why I am curious as to how low the TB75 is willing to go in that waveguide before you get the artificial sound you were describing...and I wonder if moving to a slightly bigger 12x8 with the corners squared up a little bit would allow for a bit more down low or if it would essentially behave the exact same way.

[Cornell77]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

Dave, the zero to ninety degree polar for this design looks exceptional!



It looks as straight as a bullet. I can see why the speaker would have a broad sweet spot. I hope that I get a chance to listen to them when I come to pick up my sub.

Nice work as always!

Steve

[winslow]

Re: Deltalite II 2512- TB75 1558-AudaxTW25A8 Combo Waveguide

I don't know if I've said it on this thread yet, but that is pure badarseness.

Dave your measurements and data is clearly in the big big boy league with this speaker.