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Active bass module plans (for Directiva and more)

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Rick Sykora

Rick Sykora

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Like how high? With the breakup at 5 kHz, It's unlikely to form an issue. The Esoteric has it's first wiggle just pas 1 kHz already.

Expect lower than 500 Hz, so not a problem in either case. As I have often said, there are usually many right answers. In this case, already have 2 good Dayton choices (and a few others), so an RSS210 variant is simply not my priority. However, would not discourage you or anyone else from trying. :cool:
 
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Rick Sykora

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Getting back to building speakers as have no more electronics to do.

Here is the Bassbox model of dual Dayton ES180TiA drivers in the 1.1 ft3 Denovo tower with a 3 inch round port about 10 inches long....

1675009807779.png


The vented version is in blue and the closed box is the yellow trace. I will move this into VCAD but I often start with Bassbox. In this case, it had driver in its database and gives me more apparent look at pipe resonances too...

1675010261605.png


You can see potential pipe resonances for the vented box at around 550 and 1100 Hz. These are less of a concern as plan to cross much lower than 550 Hz. Will also take a look when I test the actual speaker.
 
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Rick Sykora

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Let's start with an impedance measure...

1675011722840.png


So can see we keep above 4 ohms but there are some phase swings round the second peak that may be trouble for less robust amps. the port tuning is around 34 Hz and close to the Bassbox model estimate. In case you were wondering, the port is mounted on the bottom of the speaker. This was the only location that was suitable for a longish port in this cabinet.

There are a couple of other resonances around 180 Hz and 500 Hz. Would normally be a bit more concerned about the lower one, but this cabinet has been cut and patched enough that is likely unique to it. The 500 Hz one is the pipe resonance as anticipated by the Bassbox model.
 

mcdn

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So is that an F3 at ~40Hz vented and ~70Hz sealed? What's the SPL at F3?

I'd prefer we don't worry about amp capability, it used to be a constraint but it's a solved problem now, especially relative to the speaker cost.

As for those pipe resonances, surely some well chosen light stuffing in the box or the pipe would control them? They'll be a bit controlled by the XO being lower, but there'll still be harmonics of the fundamental that need to be damped.
 

abdo123

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I rather that we don’t deal with passive radiators or ports at all.

A 12-inch driver under 100$ is enough for 106 dB of output full-range. I don’t see a situation where someone would need more than that for a bass managed system.
 
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Rick Sykora

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So is that an F3 at ~40Hz vented and ~70Hz sealed? What's the SPL at F3?

correct and have not measured yet.

I'd prefer we don't worry about amp capability, it used to be a constraint but it's a solved problem now, especially relative to the speaker cost.

agree, but just being transparent for those who might have different amplification. May be better they consider sealed ES180 or single RS225 (coming soon).

As for those pipe resonances, surely some well chosen light stuffing in the box or the pipe would control them? They'll be a bit controlled by the XO being lower, but there'll still be harmonics of the fundamental that need to be damped.

The box is already lightly stuffed, but not getting into potential remediations as yet. Agree the harmonics may be more of a concern, but is also bottom-firing port. Lots of options and more measuring to do yet. Will see what measurements reveal with a plinth in place.
 
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Rick Sykora

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I rather that we don’t deal with passive radiators or ports at all.

A 12-inch driver under 100$ is enough for 106 dB of output full-range. I don’t see a situation where someone would need more than that for a bass managed system.
As mentioned earlier, lots of options but I do not plan for for drivers larger than 8 inches. I have done dual 8 inch RS225s before and found them more than sufficient. The challenge for a larger driver is cabinet size and getting to a height to be used for the monitor speaker. Remember these are bass modules. If you want a subwoofer, plenty of other options for those.
 
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abdo123

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As mentioned earlier, lots of options but I do not plan for for drivers larger than 8 inches. I have done dual 8 inch RS22s before and found them more than sufficient. The challenge for a larger driver is cabinet size and getting to a height to be used for the monitor speaker. Remember these are bass modules. If you want a subwoofer, plenty of other options for those.

two 8 inch drivers should have the same output as a single 12 inch so no problems by me. ;)
 
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Rick Sykora

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Here is a single RS225 vented (white line) by comparison...

1675199374396.png


As you can see, it is very comparable to the 2 ES180s in the Denovo tower. As I mentioned earlier, one major difference is the cabinet height. It is only 24 inches high and so that may factor in to whether it works for whatever sits on top.
 

badspeakerdesigner

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You can always build the cabinet as tall as you need and simply control the internal volume by cutting off sections of the cabinet internally. That's what I did for my little bass modules, had to get them to sitting ear height which is kind of high.
 
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Rick Sykora

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So a view of the vented dual ES180s using VituixCAD (VCAD)...

1675608619469.png


In VCAD, the graphing is clearly better. Notably, it is easier to see when you start to get a bass hump. The Group delay is so different than Bassbox, it seems there is something more than just scaling. As mentioned earlier, can significantly reduce the 500 Hz pipe resonance by shortening the port...

1675609072347.png


Here, you see the tradeoff of reducing the port length from 10 inches to 8. You get more of a bass bump and some worsening of the group delay. For most passive designs, can see why this overall impact to the bass response may override the port resonance at 500 Hz.
 

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Wouldn't it look a bit goofy to have the 0.56 cu ft speakers on top of the 1.16 cu ft bass modules considering the 1.16 cu ft baffle is skinnier than the prior?
 
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Rick Sykora

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Wouldn't it look a bit goofy to have the 0.56 cu ft speakers on top of the 1.16 cu ft bass modules considering the 1.16 cu ft baffle is skinnier than the prior?
That bass module is for an r2 monitor on top. If you wanted something for r1, it would be a different bass module.

Plenty of room for cabinet variations and if I am not doing, still may be able to help.:cool:
 

Joe BKNY

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That bass module is for an r2 monitor on top. If you wanted something for r1, it would be a different bass module.

Plenty of room for cabinet variations and if I am not doing, still may be able to help.:cool:
Ongoing thanks Rick! And did I miss something? (apologies if so) Is there a final design for r2?
 
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Rick Sykora

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Ongoing thanks Rick! And did I miss something? (apologies if so) Is there a final design for r2?
Yes and not yet, posted to the main thread that r2 is next in my queue. My speaker test area was getting some painting and needs more than I anticipated. Hope to do some measuring this weekend.:)
 

julbo

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I think I'm ready to plunge into a Directiva r1 SubWoofer project!
Appreciate recommendations for a design targeting two subs, large room. Sensitivity not an issue, as previously mentioned class amplification D is cheap. Prefer a sealed box.
 
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DualTriode

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Hello Rick,

I think that I have this correct.

The Denovo tower is 34 inches tall, 8 inches wide plus the r2 enclosure resting on top.

Tall with long legs sounds good to me.

Have you stacked up one of these things yet?

Is it stable? It could be a little wobbly?
 
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Hov

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This is awesome, love this idea and approach!

A DIY subwoofer is definitely on my list, I'd love to add one beside the couch. I've got 2x SB1000 right now and they are surprisingly quite powerful and impactful. Butkickers are probably a better idea for feel and because I'm in a condo, but it's hard to resist more subs LOL! I know this is not quite for standalone subwoofers, but still very interested to see how this shakes out!
 

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Hi Rick, any breakthroughs on the bass module?
Still investigating the cardioid route , or settling for something more conventional?
I have a couple of old 10" Seas P25REX DD lying around I got for cheap feel like having a go at a low output ripole config just to hear what its all about, or use them like gainphile did on his open baffles, instead of the usual approach..
 
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Rick Sykora

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Hi Rick, any breakthroughs on the bass module?

not as yet…

Still investigating the cardioid route , or settling for something more conventional?

Yes, planning for selectable directivity modes with a front woofer and opposing rear woofer in sealed cabinet.

I have a couple of old 10" Seas P25REX DD lying around I got for cheap feel like having a go at a low output ripole config just to hear what its all about, or use them like gainphile did on his open baffles, instead of the usual approach..

I like idea of open baffle but need serious woofers to deal with excursion in free air. Am just planning to use some Dayton RS-225s. They are good but not open baffle capable.
 
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