Introducing Directiva - An ASR open source platform speaker project

[ctrl]

I recall you said something a while ago about maybe seeing improvement above 10 kHz?

Yep, from 8-9kHz the simulation becomes unreliable. It could be that the radiation pattern above 9kHz becomes a bit more uniform than indicated in the simulation.

It can be assumed that the influence of the baffle on the frequency response decreases significantly above 8kHz until it is no longer present at very high frequencies.

If we now take real measurements of the Seas-DXT above 8kHz and compare them with the simulation, we get the following:

Normally Germans are defeatists, Rick I must have been stoned when I got your hopes up, but it really seems within the realm of possibility

 

[Rick Sykora]

I ran across some front baffle design considerations as I was looking into the DXT-Mon speaker. With @ctrl support, Directiva went through a similar path and came to very comparable conclusion. This was done behind the scenes for Directiva, but not fully shared.

As am confident others will find it interesting to see more of the design evolution, here is the Heissmann one...

https://heissmann-acoustics.de/en/kantendiffraktion-sekundaerschallquellen-treiberanordnun/

 

[MrPeabody]

Approaching the finish line, I glued the 3 inside seams for the top and placed the cabinet on it upside down. I also used the brace that will isolate the tweeter to spread the cabinet sides. Added some weights to hold it in place like so...

View attachment 117974
In a square cabinet, to get a good glue joint, would normally have glued the brace in sooner. With the angled edges, this is not an issue. Also, while the dry fit seemed ok, the brace is a bit to long now that the cabinet is tighter. As I need it in place for initial measurements, will trim and glue it next.

I am very impressed with this project and am looking forward to the result. I'm a little surprised that the brace ended up being too long. If I had built it, I'm pretty sure the brace would have ended up being too short.

 

[ctrl]

I'm pretty sure the brace would have ended up being too short.

Yep, that's a mathematical fact. This follows immediately from the probability theory:
The probability that the brace is too long or too short is 50:50 - the case that the brace fits exactly never occurs.
As Rick's brace got too long, yours would inevitably get too short - QED

 

[Rick Sykora]

Yep, that's a mathematical fact. This follows immediately from the probability theory:
The probability that the brace is too long or too short is 50:50 - the case that the brace fits exactly never occurs.
As Rick's brace got too long, yours would inevitably get too short - QED

Guess just got that überschreitet thing going again...

TBH, the brace was the last part I cut as it needed to fit precisely between the drivers. I thought it was spot on, but better to have to trim slightly.

 

[Rick Sykora]

Before I do the final gluing, contemplated the wiring and connectors. I like speakons, but the knock-in binding posts are less wiring work and airtight. The downside is how they stick out the back. Have the router bit now but, before I can do rounding, better if the front baffle is permanently in place. A 7/8" round is going to take some material from the side panels. Next time will use a thicker baffle, but not a problem for a prototype.

As I fit the front baffle, it rocks a little more than I like. This is because the panels were aligned to make nicer external joints and the corner joints are a bit off. I could just clamp and hope the glue fills in., but is any easy fix on the table saw just to trim off the excess edge.

 

[HammerSandwich]

Yep, that's a mathematical fact. This follows immediately from the probability theory...

With 50:50 odds of connecting a USB-A device on the 1st try, I get it wrong 98% of the time. And everybody I know reports similar results!

 

[Martin]

With 50:50 odds of connecting a USB-A device on the 1st try, I get it wrong 98% of the time. And everybody I know reports similar results!

Actually, I always get it right the first time, but it doesn't go in for some reason, so I flip it over and it still doesn't go in, then I look at both the socket and cable and flip it over a second time and plug it in. Every - freakin' - time.

 

[MrPeabody]

...Have the router bit now but, before I can do rounding, better if the front baffle is permanently in place. A 7/8" round is going to take some material from the side panels. Next time will use a thicker baffle, but not a problem for a prototype....

I was actually wondering about that 7/8" rounding. I was wondering if you were planning to reinforce the interior corner with long pieces of scrap wood or plywood or MDF. Even 1/2" by 1/2" will help. Also, it seems to me that you don't need to do this on the lower portion of the edges alongside the woofer, and that you can probably keep it stronger if you only do it along the sides of the tweeter. However you do it, it will be tricky with a hand router.

 

[MrPeabody]

Actually, I always get it right the first time, but it doesn't go in for some reason, so I flip it over and it still doesn't go in, then I look at both the socket and cable and flip it over a second time and plug it in. Every - freakin' - time.

That's exactly what I do. I can try it both ways several times but it never goes in until I've visually examined both the socket and the cable. I think there must be something in the spec to make it like this.

 

[thewas]

Actually, I always get it right the first time, but it doesn't go in for some reason, so I flip it over and it still doesn't go in, then I look at both the socket and cable and flip it over a second time and plug it in. Every - freakin' - time.

Not only you:

When the inventor of the USB died,

they lowered his coffin,

raised it back out,

flipped it over,

lowered it again,

raised it back out,

flipped it over again,

then lowered it down again.

Funnily this even happened to me even with my new mobile phone till I realised it has USB-C.

 

[Rick Sykora]

Along with tweeter connectors and wiring, the brace is now in. After trimming the front edges, the brace was trimmed slightly again. Would not have been able to do as easily on a rectangular cabinet...

 

[Rick Sykora]

Attached the front baffle and let the glue set overnight. After some practice with my new roundover bit on some scrap wood, gathered up the nerve and routed the front baffle. As I mentioned, my router is larger and powerful, so those with experience know the anticipation that goes when you flip the switch and the router spins up a large, sharp bit like this 7/8 inch one. Fortunately, it went well.

Always a good day when you do not end up having to redo the front baffle because you slipped up with the router!

Here is the result...

Speaking of slipping up with the router... You may notice the yellow tinge to the woofer cutout. The recess for it was not even (my fault), so used some watered down wood glue to level it. Need to clean it up and add the woofer wiring and some damping. Will get the drivers mounted and get some initial measurements later today.

 

[MrPeabody]

Attached the front baffle and let the glue set overnight. After some practice with my new roundover bit on some scrap wood, gathered up the nerve and routed the front baffle. As I mentioned, my router is larger and powerful, so those with experience know the anticipation that goes when you flip the switch and the router spins up a large, sharp bit like this 7/8 inch one. Fortunately, it went well.

Always a good day when you do not end up having to redo the front baffle because you slipped up with the router!

Here is the result...
View attachment 118520

You may notice the yellow tinge to the woofer cutout. The recess for it was not even (my fault), so used some watered down wood glue to level it. Need to clean it up and add the woofer wiring and some damping. Will get the drivers mounted and get some initial measurements later today.

Looks very nice. I did the same thing with router the recess once, which happened because I hadn't properly tightened and something and the bit crept lower as I went around the circle. I fixed it with some epoxy. After the epoxy had cured sufficiently, I routed it again, and it was probably better than the original MDF. This is going to be a good looking speaker. Except of course for the surround on the woofer.

 

[Rick Sykora]

In some earlier posts, it was suggested that we try a lower crossover to the DXT tweeter. While sims did not show enough promise to do so for the Purifi woofer, it made me wonder about another promising woofer. The design I was working on previously used the Dayton ES180Tia. It would benefit more from the lower DXT crossover point and tunes easier as a BR box than the Purifi.

The Dayton ES180Tia is also a great value at around a quarter of the Purifi woofer price. With a little coaxing, it also drops in to the same cutout. This would give Directiva a much lower cost of entry. If there is enough interest, will give it a more serious look. Let me know. Thanks!

 

[ctrl]

The Dayton ES180Tia is also a great value at around a quarter of the Purifi woofer price. With a little coaxing, it also drops in to the same cutout. This would give Directiva a much lower cost of entry. If there is enough interest, will give it a more serious look. Let me know. Thanks!

Unfortunately, I do not have any test reports from the ES180. The measurements from Voice Coil are unfortunately not performed on an IEC baffle - what is shown does not look bad.

Fit would in any case the Dayton RS-180P-8, low harmonic distortion (HD) and up to 1.7kHz virtually error-free FR (@1.8kHz small resonance).

For extremely low HD, SBAcoustics would be an option (SB17CAC35-4 or SB17NBAC35-4). But these are designed for larger volumes - that should not be a problem with active tuning.


The directivity of the tweeter in the Directiva cabinet is so even (according to the simulation) that one is very flexible with regard to the crossover frequency.
Starting at [email protected], anything is possible. This also leaves a lot of room for fine-tuning (via listening sessions).

As examples, the simulated crossover frequencies for the Directiva, once with [email protected] and [email protected] (in the middle diagram: on-axis = black, LW = green, IR = orange, SP = blue, DI = red):

 

[Rick Sykora]

Unfortunately, I do not have any test reports from the ES180. The measurements from Voice Coil are unfortunately not performed on an IEC baffle - what is shown does not look bad.

Fit would in any case the Dayton RS-180P-8, low harmonic distortion (HD) and up to 1.7kHz virtually error-free FR (@1.8kHz small resonance).

For extremely low HD, SBAcoustics would be an option (SB17CAC35-4 or SB17NBAC35-4). But these are designed for larger volumes - that should not be a problem with active tuning.


The directivity of the tweeter in the Directiva cabinet is so even (according to the simulation) that one is very flexible with regard to the crossover frequency.
Starting at [email protected], anything is possible. This also leaves a lot of room for fine-tuning (via listening sessions).

As examples, the simulated crossover frequencies for the Directiva, once with [email protected] and [email protected] (in the middle diagram: on-axis = black, LW = green, IR = orange, SP = blue, DI = red):
View attachment 118547 View attachment 118548

Thanks!

Have the Dayton RS180. It needs a bigger cutout than the Purifi.

Like the SB idea, but only one I have is the SB17NRX2 and it is with the Bagby speaker with Amir right now. A quick check shows the cutout is smaller than the Purifi. Same with the Satori ones.

 

[Zvu]

I don't like that resonance ridge at 1.3kHz

https://www.dibirama.altervista.org...io-es180ti-8-mid-woofer-7-8-ohm-200-wmax.html

 

[tktran303]

Due to the natural response profile of the PTT6.5, I could not found a suitable crossover between 1.5-2KHz, even though my tweeter could manage this.

Pros/cons/tradeoffs.

But if you are looking for a midwoofer with the same size cutout; consider all of the SEAS 18/19 series family. Eg. ER18/UR18/W18/L19/W19

Exact same frame size and even 6 screwhole positions

 

[Rick Sykora]

A slight delay as had to deal with t-nut that got dislodged about halfway through tightening the bolt. Anyone who has experienced knows just how difficult this can be particularly when the cabinet is all sealed up. However, with the passive radiator cutouts allowing access to the back of the woofer, got some vise-grips on the sucker and freed the bolt!

With the landing pad for the t-nut torn up, the new one started to lose grip, so nursed it until the bolt threaded far enough to seat it. Here is the assembled speaker waiting to be measured (after some dinner)...