BillFitzmaurice.info

Hi!

Does anyone happen to know if an Eminence PSD2002 driver work in a DR280 cab?

Here's the driver spec sheet:

https://eminence.com/products/psd2002_8#specifications

Notable specs:

Resonance 0.54 kHz
Recommended Crossover 1.2 kHz / 12 dBkHz
Overall Diameter 5.25"
Overall Depth 2.2"
Weight 4.7 lbs


From the DR280 plans:

"A 2kHz crossover diffraction compression horn driver option uses two Eminence ASD-1001 HF drivers (or the equivalent, with maximum resonance 1.3kHz). Screw-on drivers use a 1-3/8” female screw-on to bolt-on adapter to attach them to the horn. If a lower crossover is desired the Eminence F151M-8 driver or equivalent, with maximum resonance 1000Hz, is recommended. The F151M-8 is a bolt on driver, so no screw on adapter is required. If you substitute a different driver the maximum allowable driver diameter is four inches, maximum depth 2½ inches."


The reason I ask is because the PSD2002 has a lower crossover than both the ASD-1001 and the F151M-8. The PSD2002 spec sheet says 1.2 kHz / 12 dBkHz. Maybe with the third order of the DR280 cab, the crossover could be as low as 800 Hz? Maybe even lower?

Also, the F151M-8 drivers are not available right now unless you only need a few of them. And, the PSD2002 is reasonably priced.

From where I'm sitting, this is yet another classic tale of The Good, The Bad, and the Sketchup.


The Good:

The PSD2002 has a resonance of 0.54 kHz. That is less than 1000 Hz. Good there.

The PSD2002 is available in a bolt on version. No screw to bolt adapter needed. Not that it's a requirement, but it's always nice to save room in tight spaces. Good there.

The PSD2002 is 2.2" deep. That is less than 2.5". Good there.

While we're on the subject of adapters and depth clearances, it seems like a question worth asking is this - Does the 2.5" depth maximum in the plans take into account the adapter? In other words, can a driver be screw on (and need the adapter), and also be up to 2.5" deep? On the flip side, since it doesn't need an adapter, can a bolt on driver have some extra depth to it, and be more than 2.5" deep?


The Bad:

The PSD2002 has a diameter of 5.25". That is more than the 4" allowed in the plans. No bueno.

The PSD2002 weighs 4.7 lbs. That is almost twice as much as the 2.5 lbs for the F151M-8. Yikes!


That said, it seems like a clear and obvious NO for the PSD2002.

But, then I had a look at the Sketchup file, and I started playing around with the ruler tool...


The Sketchup:

I'm not sure which driver is modeled in the Sketchup file. It seems like it might be the NSD2005. Anyway, the driver modeled in the file measures 4" in diameter, and 1.75" deep. That depth measurement is for the body of the driver, so it doesn't include the white wire terminals. Those might stick out another 1/4" or so. But since they wouldn't hit anything anyway, I'm ignoring them.

I measured a conservative 1 and 11/32" gap all the way around that driver. I say conservative because I looked for the smallest clearance between the upper edge of the compression driver and the lower edge of the woofer frame. To actually measure it, I used parallel imaginary lines to extend these surfaces, and found the perpendicular distance between those lines. I hope that makes sense.

There also seems to be plenty of space between the diagonal woofer frame struts and the compression driver, so I don't think there would be anything to worry about there. I didn't actually measure it, only eyeballed it.



In theory, 1 and 11/32" clearance all the way around the driver in the model should let a guy squeak a PSD2002 in there, yes? (The PSD2002 would only take up 5/8" of that 1 and 11/32" clearance, leaving 23/32".)

If yes, then the next thing would be to reinforce the wooden driver mount to handle all the extra weight. Use thicker plywood for the circular mount piece, more triangular bracing pieces between the mount and the module, etc. Maybe we'd even need to reinforce the horn sides and reflectors? Or use thicker plywood there as well? I don't know.

The bottom line is, if there if enough clearance, and enough extra bracing, the PSD2002 just might work, right?

Or, at the very least, the PSD2002 might be worth testing in the real world? Not just in Sketchup?

Unless there is another factor(s) that I'm missing?

Thoughts?

Levi wrote: ↑Sun Apr 28, 2024 2:10 pm Unless there is another factor(s) that I'm missing?

The HF horn won't go below 1.2kHz.

Got it! Thanks, Bill!

Just out of curiosity...

Does that mean it will not horn load below 1.2 kHz, even though the driver could go below 1.2 kHz?

Also, the old DR280 plans offered the option of going to down to 1 kHz with the BMS 4552HD driver. I noticed there are minor differences in the measurements from old to new plans. An 1/8" here, 1/16" there, and maybe 1 or 2 degrees in places. Are these new lengths and angles what account for the change from 1 kHz in the old to 1.2 kHz in the new? If yes, and assuming the PSD2002 fits, is it somehow possible to get back down to 1 kHz using the old plans?

Errrr... sorry. I see the "usable frequency range" on the spec sheet says 1200 Hz. That's what you're referring to, yes?

Also, I guess I'm confused. Well, obviously I'm confused.

The spec sheet says the usable frequency range is 1200Hz-20kHz.

But then there's the chart. From what I can tell, it shows ample output below 1200 Hz.

Huh?

From the Eminence website:

Usable frequency range

This is the frequency range for which Eminence feels the transducer will prove useful. Manufacturers use different techniques for determining Usable Frequency Range. Most methods are recognized as acceptable in the industry, but can arrive at different results. Technically, many loudspeakers are used to produce frequencies in ranges where they would theoretically be of little use. As frequencies increase, the off-axis coverage of a transducer decreases relative to its diameter. At a certain point, the coverage becomes beamy or narrow like the beam of a flashlight. If you've ever stood in front of a guitar amplifier or speaker cabinet, then moved slightly to one side or the other and noticed a different sound, you have experienced this phenomenon and are now aware of why it occurs. Clearly, most two-way enclosures ignore the theory and still perform quite well. The same is true for many guitar amplifiers, but it is useful to know at what point you can expect a compromise in coverage.


So, even though there is output below 1200 Hz, it could be beamy.

But aren't the DR280s two-way enclosures?

So, it might still sound good below 1200 Hz, but there would be increasing compromises in coverage? And the compromises would become increasingly noticeable the further down you go? Beamier and beamier on the way down... But as long as you're in the beam, the sound quality is still good?

Oh man, now I'm really down a rabbit hole!

I'm trying to learn by comparing with another approved setup, using the ASD1001 drivers.

The latest DR280 plans say a 2 kHz crossover is okay for 2 x ASD1001 drivers. Each ASD1001 by itself is rated for 2500 Hz with 18 dB/oct slope (18, not 12!). And the spec sheet says the Usable Frequency Range is 2500Hz-20kHz...

So, is it because there are 2 drivers in the cab that the crossover drops from 2500 Hz to 2000 Hz?

And is using the drivers below their usable frequency range okay because there are two of them? Or because at higher frequencies the beaming effect isn't as pronounced or something?

Help! I'm totally and completely cross-eyed at this point.

Is this CD available to you guys in the US
https://www.sbaudience.com/index.php/pr ... co-44cd-k/
This one is really heavy, it has the nod, though l haven't had the chance to test one yet.

Levi wrote: ↑Sun Apr 28, 2024 4:50 pm ..Beamier and beamier on the way down...

On the way up mate.

I think it's the physical dimensions of the HF horn in the DR280 which determines the bandwidth it can reproduce, you could drop a number of CDs in it and have the same limits.
It must be rough when you guys are having trouble procuring drivers..

Keryn O'Shea wrote: ↑Mon Apr 29, 2024 2:22 am
It must be rough when you guys are having trouble procuring drivers..

Eminence had a problem with the F151 - too many failures in the last batch, so they stopped bringing 'em in and are researching the problem.

I'll give 'em credit for pulling 'em off the shelf instead of shipping a bad product......and it's a production problem, not a design problem, best I understand.

Hopefully, they'll be back soon.

Thanks, Keryn!

Looks like I fell off the cliff when I went down the usable frequency path. Doh!

I should have stayed on the horn loading cutoff path.

My guess is that once the NSD2005s were discontinued, Bill had to adapt. They had a crossover of 1.5kHz@12dB/oct. So that could probably go down to a 1kHz crossover in the third order DR280. That's also why he had the BMS 4552HD in the old plans - its crossover was 1kHz. So, since the 1kHz options were no longer readily available, he changed the physical dimensions of the HF horn just a bit in the DR280 to match the newer and more readily available F151M-8, which has 1.8kHz@12dB/oct, for a 1.2kHz@18dB/oct crossover in the new plans. Voila! Problem solved!

In theory, though, if we went with the HF horn dimensions in the old plans, we could get back down to the 1 kHz. I'll have to look a little closer at the differences between the old and new to see if that compression horn module is interchangeable between the two. Or, worst case we just go off the old plans entirely.

Bill, is there any chance you can confirm this hypothesis?

If the hypothesis is correct, that the main reason for the changes in the plans was driver availability, then that leads me to the big question that will determine which fork in the road we take...

Assuming sound quality is the first priority...

Is a 1kHz crossover noticeably better than 1.2kHz for a larger outdoor system of DR280s paired with T60s playing mostly recorded EDM? Certainly it must be audible versus a 2.0kHz crossover, yes? What do you guys think?

And don't worry, thanks to Bruce we have a backup plan of ASD1001s! We are just thinking on how to get the fastest race car we can before our plywood arrives and we commit to cutting.

Levi wrote: ↑Mon Apr 29, 2024 10:13 am Is a 1kHz crossover noticeably better than 1.2kHz for a larger outdoor system of DR280s paired with T60s playing mostly recorded EDM?

If it was I'd have done whatever was required to cross at 1kHz.
Rule #1: Follow the plans.
Rule #2: Follow the plans.
Rule #3: Never break rules #1 or #2.

There are many drivers that have the required specs. This is one of them: https://www.parts-express.com/LaVoce-DN ... quantity=1

Levi wrote: ↑Mon Apr 29, 2024 10:13 am ..don't worry, thanks to Bruce we have a backup plan of ASD1001s!

Nice work Bruce
I'm sure you've a lot running through your mind atm about this venture mate, sometimes we can complicate things for ourselves when we're stressed.. we're all lucky the technical side has been worked out for us, next time you're cross eyed just breathe and trust in the plans mate