Directiva driver candidate discussion

[Adi777]

Well, I think the Purifi is too expensive for end customer use, companies will get them with a huge discount.

Too expensive? Look at the most expensive Scan-speak and diamond Accuton.

 

[Marc v E]

Too expensive? Look at the most expensive Scan-speak and diamond Accuton.

I get your point. However, when you look at it from top measuring speakers, like the d&d c8, they only use 100 dollar woofers vs 425 for the purify (each).

 

[Burgunder]

For a smaller speaker perhaps you could look at the Epique E150HE-44 or the Kartesian Sub120. The SB Acoustic drivers look nice too, but you'll end up with something like this very quickly http://www.troelsgravesen.dk/SBAcoustics-61-NAC.htm
Or perhaps look at a 3-way with cheaper drivers, I apologize if a 3-way is out of the question.

 

[Adi777]

I know what you mean. However, looking at it from the best measurement speakers like the d & d c8, they only use woofers for $ 100 versus the 425 for purification (each).

Now it's question. What if the Dutch & Dutch 8C makers had taken advantage of the best pickups available on the market.

 

[Marc v E]

Now it's question. What if the Dutch & Dutch 8C makers had taken advantage of the best pickups available on the market.

Good call.

I would assume that given the technical background of the d&d engineers, their pioneering in directivity of sound and their scientific approach, that their choice of drivers was based on a purely scientific evaluation. Surely the asking price would give them plenty of headroom to choose one of the best that are available.
At least, that is my reasoning.

 

[morpheusX]

Too expensive? Look at the most expensive Scan-speak and diamond Accuton.

When considering the resources and knowledge of the Directiva team, its seems a waste not to use state of the art drivers to achieve the best result possible, within a reasonable cost.

$100 vs $425 will lead to an $650 increase just for the woofers, but when weighting everything, and considering the goal to obtain a state of the art speaker, $650 seems a fair price to pay. The Directiva V1 had a boom of $1415 for a pair of speakers, which is almost a bargain considering how good they are.

We already know how small the impact of electronics is, and how important speakers are in the final result, so aiming for the best speaker we can reasonably achieve seems to me the ultimate goal.

Even if when using the "best" drivers available, within a reasonable cost, as the Purify is for $425, which is more than 4 times the price of the $100 units, without being 4x times better, it seems to me a good compromise to achieve a state of the art speaker.

Lets not forget that in this hobby, there are people who spend much more than that in power cables or cable lifters

 

[DualTriode]

If the goal of directivity and low distortion can be done at a lower cost, why aren't we?

Hello All,

Can we set the target here please? What is the Goal?

My impression is that we are looking for long stroke limited diameter woofers in limited size enclosures with low distortion.

Can we limit the search to a single 8 inch driver possibly with up to 2 equal size passive radiators?

Can we limit the enclosure volume to 45L?

Can we target THD to no higher than 50dB's below the fundamental test frequency? (This increased THD level opens things to lower cost drivers.)

Someone with someone with an idea regarding a directivity goal?

Thanks DT

 

[Rick Sykora]

Hello All,

Can we set the target here please? What is the Goal?

My impression is that we are looking for long stroke limited diameter woofers in limited size enclosures with low distortion.

Can we limit the search to a single 8 inch driver possibly with up to 2 equal size passive radiators?

Can we limit the enclosure volume to 45L?

Can we target THD to no higher than 50dB's below the fundamental test frequency? (This increased THD level opens things to lower cost drivers.)

Someone with someone with an idea regarding a directivity goal?

Thanks DT

Agree, these are important questions. However, additional context is needed. Directiva r1 is done but r2 does not yet have a bass module driver. If not one of those, would be considering requirements for a new speaker.

Once a target speaker is defined, then I assign a release number and drivers are chosen. I have updated the opening post to clarify.

 

[BDE]

Just as a further library of driver measurements, some of the mentioned ones are listed:
https://www.dibirama.altervista.org/le-prove/woofer.html
https://www.dibirama.altervista.org/le-prove/mid-woofer.html

 

[D!sco]

Just wanted to highlight the R1 design goals re: driver discussion. There’s a great model available right now, but regarding scalability, it would be nice if a version that ditched the $1000 budget and demand for the purifi woofer. There are plenty of affordable options for making a two way that fits the other criteria.

From Rick:
“Here were my goals for the speaker:

1. The speaker would be active and simple to build (for me, this meant no tools beyond a circular saw but for more optimal results is more like a table saw and router).
2. The design tools would be free but flexible enough to allow external data import/export.
3. The design would be openly shared but FOR NON-COMMERCIAL USE ONLY.
4. The cost target for the drivers and crossover would be approximately $1000 US.
5. Keep the cabinet size to around 15 liters or about .5 a cubic foot or smaller (allowing it to be reasonably shipped and Amir to test). The electronics would be external. (EDIT)
6. The design would allow for modest flexibility and scalability so others could (eventually) modify and add value. So, here is where Amir intervened with his ideas/goals...
7. The speaker should have good directivity. Note, this did force me to reconsider some of my (mainly cabinet) plans as we'll see later.
8. The speaker should use the new Purifi 6.5 woofer. As it was not in my original plans, I was hesitant due mainly to cost. However, after working on the SPK5, had them on hand and agreed to use...”

EDIT: And another option, moving very far afield of the Purifi driver would be the Peerless HDS-835025. The power handling isn't nearly as spectacular, but when you lower the standard for entry by porting for 50hz, the field really opens up to better candidates. Nothing in the 6-7" range really competes with the Purifi. At a minimum it's still the Scanspeaks and Satoris that can handle the box and that 5x8 PR, which shaves a few hundred bucks off the final. They still can't handle the power, so it doesn't seem like a worthwhile tradeoff. Might as well tune for a bass reflex design and reduce the power handling expectations a little. 80 seems to be the industry standard at that size. Again, Purifi is blowing it out the water. It takes an affordable 8" woofer to really match the purifi's specs.

 

[DualTriode]

Just as a further library of driver measurements, some of the mentioned ones are listed:
https://www.dibirama.altervista.org/le-prove/woofer.html
https://www.dibirama.altervista.org/le-prove/mid-woofer.html

Hello All,

A good driver library is good to have. The driver library should contain distortion data results.

Low distortion performance is likely more important than lower price.

Half roll distortion can negate the best efforts to maximize motor performance.

We need driver distortion test data to put pricing into perspective.

Thanks DT

 

[BelgianJoey]

My vote would go to the SB Acoustics Satori TeXtreme drivers: TW29TXN B8 tweeter and MW16TX-8 bas-mid with which I did my first DIY project.

 

[DualTriode]

My vote would go to the SB Acoustics Satori TeXtreme drivers: TW29TXN B8 tweeter and MW16TX-8 bas-mid with which I did my first DIY project.

Hello,

Looks like nice speakers.

The woofer will be beaming by 2500hZ. The tweeter will start beaming by 10khZ.

There will be no directivity transition at all.

Did you use some sort of waveguide?

Thanks DT

 

[DualTriode]

Hello All,

I started to assemble a couple of 1 cubic foot Denovo knock down enclosures with the idea of test driving a pair of the new Purifi 8 inch 8R Ultra Low Distortion drivers. I picked this test enclosure with the idea that others have access to the same enclosures on Parts Express or ebay. The enclosure comes with a cutout for a 10 inch woofer. I am cutting a round plywood circle to plug the opening, then make a new smaller cutout for the 8 inch driver.

By testing I found that the 6-1/2 inch purifi drivers in a sealed 0.55 cubic foot enclosures did not run into additional distortion from "air suspension".

In fact the the added stiffness added by the sealed enclosure is less problematic than drivers' mechanical suspension alone. The larger enclosure with the 8 inch driver will have less air compression distortion for equal levels of output.

I suppose that if you want the added bass extension of bass reflex or passive radiators then you will use longer stroke with extended coil position effects.(increased IMD into the midrange frequencies).

The 8 inch driver will start beam at lower frequencies due to being a larger diameter piston. It is likely the tweeter in a 2-way will need to cross over at a lower frequency, somewhere less than 2khZ

I am picturing a larger waveguide perhaps even a Compression Driver tweeter.

Thanks DT

 

[abdo123]

I would assume that given the technical background of the d&d engineers, their pioneering in directivity of sound and their scientific approach, that their choice of drivers was based on a purely scientific evaluation.

I think you're all misunderstanding why the purifi driver was picked.

It was all about making a reasonably sized full range 2-way with the Denuvo flat pack, a regular 6.5 inch would not have reasonable headroom at 40Hz like the Purifi OR it would not function well as a mid-range.

For the 8C the 8-inch midrange has a very sharp crossover at 100Hz. Given the same liberty, even a 4.5 inch decent generic midwoofer would function even better than the purifi directivity and linearity wise.

 

[DualTriode]

Hello All,

I started to assemble a couple of 1 cubic foot Denovo knock down enclosures with the idea of test driving a pair of the new Purifi 8 inch 8R Ultra Low Distortion drivers. I picked this test enclosure with the idea that others have access to the same enclosures on Parts Express or ebay. The enclosure comes with a cutout for a 10 inch woofer. I am cutting a round plywood circle to plug the opening, then make a new smaller cutout for the 8 inch driver.

By testing I found that the 6-1/2 inch purifi drivers in a sealed 0.55 cubic foot enclosures did not run into additional distortion from "air suspension".

In fact the the added stiffness added by the sealed enclosure is less problematic than drivers' mechanical suspension alone. The larger enclosure with the 8 inch driver will have less air compression distortion for equal levels of output.

I suppose that if you want the added bass extension of bass reflex or passive radiators then you will use longer stroke with extended coil position effects.(increased IMD into the midrange frequencies).

The 8 inch driver will start beam at lower frequencies due to being a larger diameter piston. It is likely the tweeter in a 2-way will need to cross over at a lower frequency, somewhere less than 2khZ

I am picturing a larger waveguide perhaps even a Compression Driver tweeter.

Thanks DT

Hello,

The glue is dry and the clamps are off one of the 1 cubic foot Denovo knock down enclosures and the 8 inch 8 R Purifi drivers have arrived.

Tomorrow I will fabricate an adapter flange to mount the 8.7 inch O.D. Purifi woofer on a enclosure with a cut out for a 10 inch woofer.

In a few days I should have some in sealed enclosure Q-total, Fs, Impedance, Phase, near field Frequency Response and Distortion (HD and IMD) measurements.

Just some added musings:

If you look at the common definition of X-Max, X-Max is measured at 10% distortion.
At what level of distortion would we think is reasonable to listen to this or any other driver/speaker as a bookshelf or mixing monitor?

Thanks DT

 

[jzagaja]

STX W.18.200.8.MCX_v2 was mentioned before (diysoundgroup.com can import). Mr. Trzaskowski from STX can do customized e.g. I've asked for two 6,5" that could drive 80 litres floorstander (Sopra style cabinet) and waiting (thick green line). Going to convert to cardioid in future - it's MTMWW (5FE120 mids and Sica tweeter or comp driver and STH waveguide).

 

[Rick Sykora]

STX W.18.200.8.MCX_v2 was mentioned before (diysoundgroup.com can import). Mr. Trzaskowski from STX can do customized e.g. I've asked for two 6,5" that could drive 80 litres floorstander (Sopra style cabinet) and waiting (thick green line). Going to convert to cardioid in future - it's MTMWW (5FE120 mids and Sica tweeter or comp driver and STH waveguide).

Like the customization but STX does not appear to have representation in North America. Reliable supply is a key Directiva criterion. I like some Wavecor drivers too but supply here seems hit or miss. May just be pandemic supply chain issue but not much point in having a great speaker design that few can get the parts to build.

 

[Biblob]

Why not stick to a good driver first and then give alternatives for the American market (or vice-versa)? If there are clear benefits for using a particular one, I'd say, stick with it

 

[jzagaja]

Factory tour: https://www.facebook.com/stxaudio/videos/?ref=page_internal