3rd speaker Project - Econowave inspired active floorstanding

[Janus77]

My sister has kindly agreed to let me build their family a set of speakers for their living room.  They're currently using a pair of Actimate mini's i'd bought her a decade ago or more, which sound fantastic however they are a little small for the room.

Build will be an Econowave inspired design.

 

I've ordered:

2 x Visaton W 300 12" woofers (180w)

2 x SBA Bianco 44CD-K compression drivers (50w)

2 x Dayton H6512 JBL clone 12" waveguides

2 x P Audio PC-35 bolt to screw on 1 inch horn adapter

 

Amp i have another of the JAB5 sure/wondom amps with a DSP chip and dacs, i'll bridge this 2.0 for 2 x 200w into the woofers.  I'd like to feed the compression drivers a normalized 50w as that's their rating.  If i look at the woofer being 91db  and compression driver 110, i need to dumb the CD down about 17% to match the woofer output, so call that 40 watts required.  I doubt they'll ever push these enough to use close to that, Sure/Wondom have a 2 x 30w amp which should be plenty, however it doesn't have dsp so i'm unsure if i can program in a crossover using this.  The alternative would be to cascade another JAB5 as it would give the connectivity, but it seems total overkill to have 400w in an amp and only ever hope to use about 60w of it.  They have a 4 x 30w amp, but it's not compatible to use with the JAB5.  Will keep thinking. 

Another option is they have a 6 x 100w amp with no DSP, so i could use that and build the crossove pasive, which is something i'd like to learn anyway, but that amp doesn't have bluetooth and i'm not sure of the dac built in either..

 

Not sure when lockdown will end and i can access the workshop again, will start planning anyway.  Thinking front ported, not sure if i go with a slot port at the bottom, or dual tube ports, hoping to tune it down to 30hz.

 

Fun fun.

Edited August 2, 2021 by Janus77

[anandpkumar]

Sounds like an inspiring build - good luck with this mate. Are you planning to house the active (amplifier) section inside or outside the speaker box?

[Maz4bz]

Why not go with the matching SBA waveguide?

 

It looks real smooth on axis with that CD - would love to see someone pull the trigger on these and measure the off axis polars for the combo. 

 

Edited August 2, 2021 by Maz4bz

[Janus77]

Maz, I haven't seen the SBA waveguide, do you have a link?

 

Anandpkuam, Planning to have the amp housed in the box.

[Maz4bz]

SB Audience :: HORN H225

 

 

 

 

 

Here's your CD with the H250, silky smooth! Just choose your polar option....

 

Edited August 2, 2021 by Maz4bz

[Janus77]

I know it’s probably not everyone’s consideration, but I like that the Dayton waveguide is the same width as the woofer.   Also I’ve pulled the trigger for good or bad, so we’ll see how it goes with the adapter and if the response is rubbish I might have to revise the design

[Janus77]

I’ll have the driver and waveguide way before I can start the build so plenty of time for measurements.  

[Maz4bz]

The Econowave/JBL PT/Dayton H6512 is a fine choice.

 

See attached JBL tech note for further info...

JBL PT Waveguide tech note V1, No 13.pdf

Edited August 2, 2021 by Maz4bz

[RoHo]

21 hours ago, Janus77 said:

My sister has kindly agreed to let me build their family a set of speakers for their living room.  They're currently using a pair of Actimate mini's i'd bought her a decade ago or more, which sound fantastic however they are a little small for the room.

Build will be an Econowave inspired design.

 

I've ordered:

2 x Visaton W 300 12" woofers (180w)

2 x SBA Bianco 44CD-K compression drivers (50w)

2 x Dayton H6512 JBL clone 12" waveguides

2 x P Audio PC-35 bolt to screw on 1 inch horn adapter

 

Amp i have another of the JAB5 sure/wondom amps with a DSP chip and dacs, i'll bridge this 2.0 for 2 x 200w into the woofers.  I'd like to feed the compression drivers a normalized 50w as that's their rating.  If i look at the woofer being 91db  and compression driver 110, i need to dumb the CD down about 17% to match the woofer output, so call that 40 watts required.  I doubt they'll ever push these enough to use close to that, Sure/Wondom have a 2 x 30w amp which should be plenty, however it doesn't have dsp so i'm unsure if i can program in a crossover using this.  The alternative would be to cascade another JAB5 as it would give the connectivity, but it seems total overkill to have 400w in an amp and only ever hope to use about 60w of it.  They have a 4 x 30w amp, but it's not compatible to use with the JAB5.  Will keep thinking. 

Another option is they have a 6 x 100w amp with no DSP, so i could use that and build the crossove pasive, which is something i'd like to learn anyway, but that amp doesn't have bluetooth and i'm not sure of the dac built in either..

 

Not sure when lockdown will end and i can access the workshop again, will start planning anyway.  Thinking front ported, not sure if i go with a slot port at the bottom, or dual tube ports, hoping to tune it down to 30hz.

 

Fun fun.

Really looking forward to following this project.

Don't worry too much about the power ratings and amp power.  You will be turning the volume down well before you reach "damage level" power.  50W into a compression driver in a domestic setting would blast your eardrums out.  Having the DSP on-board is much more important IMO.

[Janus77]

Thanks.  I've got a lot to learn, luckily there are members like Mazb4z willing to help out and point me in the right direction.  Otherwise, "step aside doctor, i'll deliver this baby" will take over and who knows where i end up

 

Learning to take accurate measurements will be a big part of this project. 

I'm thinking a 100L enclosure is about as big as i can go, which is similar in size to say the JBL L100 classics. 

Modelling has this ported enclosure at an F3 of 40hz, and -8db at 30hz, tuned to 32hz. 

Happy to be schooled, it's all a learning process

 

I have some 24mm birch ply i can use for the front baffles, was thinking of using MDF for the rest, however the workshop i use don't allow cutting of MDF, so i might have to go with the more expensive ply option all around.  I think 16-18mm will do the trick for this build though, with bracing. 

 

Was tempted to mount the waveguides/compression drivers naked above the woofer box, however i lose the area around the driver if i build it in, which would make the entire construction larger when i compensate for the volume loss, gave up on that idea.  Naked horns are a cool look!

[RoHo]

I agree about the look of a horn on top of a box.  Whichever way you go keep the waveguide as close to the woofer as practical.

[davewantsmoore]

23 hours ago, Janus77 said:

If i look at the woofer being 91db  and compression driver 110, i need to dumb the CD down about 17% to match the woofer output, so call that 40 watts required.

No.   You need to drop it by 19dB, which is not at all 17%.

 

-19dB works out to be ~0.012 x ... ie. minus 88%

 

Said another way..... For every 1dB to the woofer, you need 0.012dB to the tweeter.

 

If you put 200w into the woofer.... then for the same SPL you will need 2.8 watts (call it 3, heh) for the tweeter.

 

23 hours ago, Janus77 said:

I doubt they'll ever push these enough to use close to that

Yep.... 200w in the woofer is >115dB   (assuming it doesn't run out of excursion... which you should check in your design).

[Janus77]

Thanks Dave, so the 30w amp will be more than enough for the tweeter.

that's a huge difference in SPL/power between the 2 drivers.  Makes sense i guess as one has a lot of mechanical movement and some heat, the other does not (do compression drivers get hot?)

[davewantsmoore]

1 hour ago, Janus77 said:

Modelling has this ported enclosure at an F3 of 40hz, and -8db at 30hz, tuned to 32hz. 

Happy to be schooled, it's all a learning process

That sounds round about ok .... let's just assume it is for now.

 

The next step is to see what amount of power that it will take to put the woofer to its excursion limit in that cabinet..... it's probabaly a lot less than 200.     Double that power (cos you don't want to go near the rated limits of these Sure amps) ... and then use that as the basis for your selection.

 

Then when you design the DSP, you can figure it out (gain, etc.) so that when they put in "maximum possible signal" .... they get out "maximum safe speaker sound"

 

 

1 hour ago, Janus77 said:

I have some 24mm birch ply i can use for the front baffles, was thinking of using MDF for the rest, however the workshop i use don't allow cutting of MDF, so i might have to go with the more expensive ply option all around.  I think 16-18mm will do the trick for this build though, with bracing. 

Well designed bracing is mostly more important, than the cabinet thickness.

 

1 hour ago, Janus77 said:

Was tempted to mount the waveguides/compression drivers naked above the woofer box, however i lose the area around the driver if i build it in, which would make the entire construction larger when i compensate for the volume loss, gave up on that idea.  Naked horns are a cool look!

I'd put the horn inside the box.

[davewantsmoore]

3 minutes ago, Janus77 said:

that's a huge difference in SPL/power between the 2 drivers. 

 

Yep.  dB are very big.... so 91 and 110 are worlds apart.

 

Every +3dB = double

[BuzzzFuzzz]

1 hour ago, Janus77 said:

was thinking of using MDF for the rest, however the workshop i use don't allow cutting of MDF

G'day mate.

You really have been bitten by the bug.

 

I'm curious as to why they won't allow MDF cutting in the shop?

 

I know it's not safe to breathe the dust / glue...  Is that the reason?

 

Cheers.

Ant.

[Janus77]

22 minutes ago, BuzzzFuzzz said:

G'day mate.

You really have been bitten by the bug.

 

I'm curious as to why they won't allow MDF cutting in the shop?

 

I know it's not safe to breathe the dust / glue...  Is that the reason?

 

Cheers.

Ant.

 

Yes that's the reason, they don't want the dust floating around..

[Maz4bz]

56 minutes ago, davewantsmoore said:

 

Every +3dB = double

 

Its not a linear result across all frequencies but simplistically from the image below we see:

• 6dB is double the sound pressure level (dB SPL); and
• 10dB is required to perceive a doubling of loudness.

 

 

 

 

From UNSW:  To get a perceived doubling of loudness, you need an increase of 10 phons. 10 dB corresponds to 10 phons....

 

"How much louder is loudspeaker driven (in its linear range) by a 100 W amplifier than by a 10 W amplifier?

The powers differ by a factor of ten, which, as we saw above, is 10 dB. All else equal here means that the frequency responses are equal and that the same input signal is used, etc. So the frequency dependence should be the same. 10 dB corresponds to 10 phons. To get a perceived doubling of loudness, you need an increase of 10 phons. So the speaker driven by the 100 W amplifier is twice as loud as when driven by the 10 W, assuming you stay in the linear range and don't distort or destroy the speaker. (The 100 W amplifier produces twice as many sones as does the 10 W.)"

 

 

Edited August 3, 2021 by Maz4bz

[davewantsmoore]

30 minutes ago, Maz4bz said:

loudness

 

(Sorry, at the risk of going off the deep-end for a thread like this.....)

 

What you posted is correct....  for pressure, where 6dB = double .... but for power (which is what we were discussing) 3dB = double. 

 

 

There are two types of dB .... power quanties, and root-power quantities (sometimes called "field quantities" ) .... and they differ by a factor of 2.   You can read here:  https://en.wikipedia.org/wiki/Power,_root-power,_and_field_quantities

 

 

I was talking about how to compare driver SPL / power ratings.

 

For example, the driver which requires 1 watt to make 91dB ..... needs 2w (double 1w) to make 94dB (+3dB)  ... a4w (double 2w) to make 97dB (+3dB) .... etc. ...   and that is the calculation which is relevant to the error Hugh made.   For power quanties, +3dB = double.   3dB more power than 100 watts is 200 watts.

 

 

What you've posted is for field quantities, like sound pressure, where 6dB = double (different by a factor of 2). 

 

57 minutes ago, Maz4bz said:

Its not a linear result across all frequencies

 

Yes.   Using perceived loudness type metrics ...... It's typically about +10dB (SPL) to "sound like it's twice as loud" .... but as you say it isn't the same at every frequency (See: Fletcher Munson).

 

 

 

... and this is why there are endless threads with confused people, wrong answers, and arguments about 3dB vs 6dB (compounded by dB per watt, vs dB per 2.83 volts) ..... and why I posted this, so anyone who arrives here, gets the "answer", and not...  "what the?!?! ... why nobody agrees on this stuff"   

[Hifiplus]

5 hours ago, Janus77 said:

I'm thinking a 100L enclosure is about as big as i can go, which is similar in size to say the JBL L100 classics

I think the L100 is probably more like 60 / 70 litres - 100 litre box is going to be huge.

Use ply all round, Bunnings have nice Red Oak finish which you could use for the sides /top/bottom and then just use cheaper for back / front (to save cost).

Just for fun, checkout acoustic pinboard (also at Bunnings), comes is a range of colours and would look great inset in the baffle.
https://www.bunnings.com.au/products/building-hardware/timber/timber-boards/specialty-board/pin-board

[Janus77]

4 hours ago, Hifiplus said:

I think the L100 is probably more like 60 / 70 litres - 100 litre box is going to be huge.

Use ply all round, Bunnings have nice Red Oak finish which you could use for the sides /top/bottom and then just use cheaper for back / front (to save cost).

Just for fun, checkout acoustic pinboard (also at Bunnings), comes is a range of colours and would look great inset in the baffle.
https://www.bunnings.com.au/products/building-hardware/timber/timber-boards/specialty-board/pin-board

I had a look at the dimensions of the L100’s. 64 x 39 x 37.  92 external.   Probably 86-87 internal taking into account “stuff”. 
 

yeah 100 is big, though not nearly as big as my speakers (180l+/-).  Figured 100 was smallish.. hah.  

[Janus77]

SBA compression drivers and horns are in my hot little hands.

Had no idea how heavy compression drivers are!  They're well built, much more finely crafted than they appear on the website pictures.

will put some pics up later.

[Janus77]

[Janus77]

Adapter plates should arrive tomorrow.  Once i have them, i'll get some measurements done.

[davewantsmoore]

On 03/08/2021 at 12:49 PM, Janus77 said:

do compression drivers get hot?

No.

 

Unless you dump high power into it constantly (this one reckons it would take 100 watts) ..... but unless you stand a looong way back that sort of SPL would hospitalise someone.

 

Your average power will be a small number or milliwatts.  A wristwatch would probably get hotter