Seas 3-way - this or that?

[Norcad]

Looking forward to see the results from your project.

Regards
Johan

So do I

 

[Norcad]

OK, here comes another simulation of L26.
This time I tried Unibox v.4.07, an interesting Excel workbook from Kristan Ougaard. You should try this!
I really like the plots from this program. Beacuse it shows so much information at one time, and still its very easy to see.
You get Total FR, Driver FR, Port FR, Leak FR, Port res, and Driver xmax in the same plot! Very good!

It is a couple of things of interest here:
Vb 73L, Fb 22,5Hz

Bassbox Unibox
F-3dB 29Hz 28Hz
F-6dB 26Hz 23Hz
Min port diam 72mm 81mm
Port L (Ø75mm) 300mm 299mm
CD > 7mm (100w) 27-48Hz 26-56Hz
Max CD 8,5mm@35Hz 11,3mm@35Hz
Vent Air Velocity 16m/s@15Hz 30m/s@15Hz

As you can see, the Cone Displacement still worries me!

 

[Norcad]

I also tried WinISD, and get similar result regarded to Freq resp and BR. This program says nothing about cone displacement.

Vb73L, Fb 22,5

F-3dB 29,5Hz
F-6dB 24Hz
Port L 297mm

 

[kyselym]

Hi again

I got home and made few simulations for you. They are made in LSPcad pro 5.25 and based on Seas datasheet TS params and tunig is done in corespondence to my experience.

First of all I would like to tell you that you worry too much about speaker behaviour at 100w input. in reality your speakers will be barely driven so hard..at least not for long time- just in peaks. you shoud take care more about 10-30w input this is normal loud to realy loud listening at home.

here are simulations for L26 in 75liters with 34%fill (I use isover as well even it is not very effective at those frequences but it takes care of eventual midrange; I also roll that isover on port tube to damp it's own resonances a bit) simulations are made for precision sound 3" flare(75mm) at full legth=45cm http://www.madisound.com/catalog/pr...d=711&osCsid=d4b84c2ea5b91fa5fe3a92bb49b2fafd As your port will be down fireing you will need probably shorten length of port (can simulate by adjusting flare radius param) - same situation as if port is close to floor.

1W input:
-no subsonic: http://phoenix.inf.upol.cz/~kyselym/norcad/L26-1W-noSUBsonic.png
-LR 15Hz subsonic n=4: http://phoenix.inf.upol.cz/~kyselym/norcad/L26-1W-SUBsonic15Hz.png

31W input
-no subsonic: http://phoenix.inf.upol.cz/~kyselym/norcad/L26-31W-noSUBsonic.png
-LR 15Hz subsonic n=4: http://phoenix.inf.upol.cz/~kyselym/norcad/L26-31W-SUBsonic15Hz.png

100W input
-no subsonic: http://phoenix.inf.upol.cz/~kyselym/norcad/L26-100W-noSUBsonic.png
-LR 15Hz subsonic n=4: http://phoenix.inf.upol.cz/~kyselym/norcad/L26-100W-SUBsonic15Hz.png

As you can see L26 doesn't reaches it's Xdamage. Yes it overcomes Xmax(lin) at 100w input power

ps. as I described before you should do fine tuning in the end by shortening port length step by step (step = 1-2cm in this case)

 

[Norcad]

Thank you!
Very interesting indeed.
I know that the speakers hardly ever will have 100w of power over a period of time.
But I want to know that if its have the headroom, in powerfull transients when listening at 95-100dB, and even more likely in party modus, when the brain is'nt there

Of course I have a few questions again

I have never used 34% fill in a bassreflex before, and as you say, most of the filling material doesnt work any good in low frequencies. So that must mean that the simulation will be al little wrong?
Res freq are 20,4Hz, and gives a pipe length of 45cm? Thats +50% when compared to Bassbox, Unibox and WinISD ???
Flare radius 50cm, what is the meaning of that? Not the flare of the pipe? Is it the baffelwith or what?

 

[kyselym]

I don't know how it is implemented in LSP cad but if you try to play with this param it has very small effect. (fill)

any simulation is a little wrong...some are more, some are less

don't care about that it is just simulation but in LSP cad it is more realistic because it counts with some nonlinearities... unibox and winisd are very simple simulation programs...

flare radius tells us how much is flare of pipe rounded. this rounding has effect on it's length. (I don't know excat definition of this param; done by experience; also incresing-simulates less space around outside flare of port; decreasing-othervice)

when I design I make longest port I expect and measure in arta system impedance(this shows tunig peak) so you know how you tuned in reality. then you have to listen and try to shorten if sound is not ok.

 

[Norcad]

Some more comments;
That you have reduced the Fb from 22.5 to 20.5, do actually increase the pipe length more than I expected. So that isnt so bad as I thought.
But when you ad more fill (assuming that it actually works at low frequencies) the pipe length should be reduced!?
I do know that bassports/pipes have nonlinearity, starting at rather low air speed. And I dont think Bassbox calculates this.

When I simulate your design in Bassbox, it becomes more similar.
Vb73-75, Fb22,5-20,5 fill 10%-35% and flared portends.
Bassbox then get a portlength of 40cm, but this is with a smaller flare radius and smaller max diameter.
The max cone displacement is 17,2mm (p-p)
But the Frequency response has a more linear roll off in LspCad at 100w (because of port nonlinearity). At 1w they are similar.

All in all I think they give very similar and accurate results.

I wonder if I should make a 75L box for testing.........
A little extra work, but better than making two finished cabinets, and find out that something isnt good enough..........

 

[Norcad]

I'm still wondering about CA26 vs L26, so while listening to some heavy bass music today, I was wondering how this CA26/BR/testbox-combo measured.
I measured nearfield both the CA26 & the port with Speaker Workshop, and then combined them. The box is 54L and the port is Ø7,6 x L 22,5 cm.
I looked at my simulation in Bassbox, but it was difficult to compare. So I simulated it in UniBox, and imported the Fr-file into SW.
The result was rather interesting I think!

Look at the attached file;
CA26=red, port=blue, combined=black, and Unibox-sim=green

FUN!

 

[Dave Bullet]

I measured nearfield both the CA26 & the port with Speaker Workshop, and then combined them

I don't think you can combine (that is sum) the port and nearfield response - since you have unknown relative phase between the two measurements (ie. it's like measuring a tweeter, then turning the box 180 and measuring the woofer response - then combining those two measurements to get the system response).

Even though - a pretty interesting measure!

I think in answer to your question (CA26 vs. L26), I would decide on:
a) maximum dB (peak) you want to achieve in your listening room
b) relative sensitivity to the CA18 drivers and how easy / seamless a xo integration would be
c) whether you want to rely on a subwoofer or whether you want the 3-way to be sufficient for music listening

Dave.

 

[Norcad]

I don't think you can combine (that is sum) the port and nearfield response - since you have unknown relative phase between the two measurements (ie. it's like measuring a tweeter, then turning the box 180 and measuring the woofer response - then combining those two measurements to get the system response).

Even though - a pretty interesting measure!

I think in answer to your question (CA26 vs. L26), I would decide on:
a) maximum dB (peak) you want to achieve in your listening room
b) relative sensitivity to the CA18 drivers and how easy / seamless a xo integration would be
c) whether you want to rely on a subwoofer or whether you want the 3-way to be sufficient for music listening

Dave. [/QUOTE

Since I measure it indoors, there is no other way to do it. And if you look at other measurements from DIY subs, this is often the way its done. Of course there can be phase problems that is hidden, but most simulation doesnt take this into account either.
So for the purpose of checking a simulation against the finished box, its OK.
What you get in sweet spot is a different story!

a) More is better, so long we talk about a rel. flat response.
b) Baffle step is one thing here, and I'm wondering if the CA26 has a sound that suites CA18 better, beacause they both are paper.
c) My hope is that I can play music without the sub(s). If not the 10" bass and 3-way is a waste.

When listening to the CA26, I'm not 100% satisfied with the lowest bass. On the other hand, there isnt so much music that goes so deep. With the L26 this would be better, but with a few other minus instead;
1. The enclosure must be bigger.
2. The port must longer (& bigger)
2. The sensitivity is lower
3. Maybe it will have a "metal" sound in the upper bass/mid bass?

I have to say though, that I like metalcone bass drivers. Just touching them and feel that they behave like a piston, instead of a sheet of paper is a good thing

 

[tinitus]

I think that Qts values are a bit high fore BR on both woofers, and Fs a bit high on CA26, and that L26 peak is really nasty but I expect both to need notches
And from what I can see on factory graphs, you will only get 85db bass on L26
Dont like the bump on CA26 impedanse


My choise would have been CA26RE4X in 65liter BR netto, port ø10x25cm

 

[Norcad]

I think that Qts values are a bit high fore BR on both woofers, and Fs a bit high on CA26, and that L26 peak is really nasty but I expect both to need notches
And from what I can see on factory graphs, you will only get 85db bass on L26
Dont like the bump on CA26 impedanse


My choise would have been CA26RE4X in 65liter BR netto, port ø10x25cm

Qts: Agree but no problem
Fs: Agree
Notches, with a xo of 250Hz thats no need.
85db is not true, you get nearly 88 IRL

If you simulate your ex of 26RE4X, and compare it to my 26RFX/54L, where is the difference?
Well you get +2dB from 35-40Hz, and a bit steeper roll off.
You also have 20w less power handling, and 6mm less xmaxp-p!
That meens that with 40w, you already exceed linear xmax in the 40-50Hz region. The 26RFX will handle 3 times that power before reaching xmax.

Conclusion? I do not agree with you

CA26RE4X=red
CA26RFX=blue
L26=yellow

 

[Norcad]

Well with my luck of simulating in Unibox in mind, here comes a plot for compering:

Dark blue: CA26RFX, Vb58L, Fb33Hz, 100w
Black: CA26RE4X, Vb65L, Fb33Hz, 80w
Pink: L26RFX/P, Vb70L, Fb21Hz, 120w

All three is loaded with max long term power.

 

[Norcad]

OK, I feel I have to make up my mind, so I can continue with other problems & questions in this 3v-design.
Because of the lower sensitivity, and the need of a bigger enclosure, the L26 is not the right choice (I think).

I stick with Unibox, and its shows me that with 50w, the CA18RNX in a 5L closed box gives me 104,6dB.
The Ca26RFX in a 60L vented box gives 107,7dB.
Thats 3dB of BSC, before any adjustment of the amps gain.
Close enough I think..............

So the setup looks like this:
Tweet: 27TDFC
Mid: Singel CA18RNX in a 5L closed box
Bass: CA26RFX in a 60L vented box

The complete speaker enclosures dimensions will be:
H: 100 cm
W: 52,5 cm, radius 10cm.
D: 22 cm

The next questions is:
How high/low on the baffle should I place the bass, and why?
Where should I place the port(s) and why?

 

[Dave Bullet]

How high/low on the baffle should I place the bass, and why?

Unfortunately, The Edge and BDS don't include room effects.

Jay Butterman's unofficial speaker workshop manual included a spreadsheet to try and simulate this - haven't tried.

Vance Dickason in LDC mentioned a guideline about driver placement in regards to nearest boundary - can't remember details.

I'm also wondering - even though I am using the L26 - the need should be identical since XO points and driver geometry are very similar.

For me - closer to the floor is better from the enclosure viewpoint, since I want a narrow baffle for better imaging from the L15, and I am sloping the cabinet (left to right).

David.

 

[Norcad]

Thank you Dave!
When reading your answer, where you mention Edge and BDS without room effect simulation, I remembered that I do have room acoustic simulator found on the internet.

When simulating my room, the differense between 20 and 50cm from floor and to the center of the driver, the only changes is in the 100-200hz area. Mostly minor, but when 50cm it gives an dip of -13dB@135Hz.
If this simulation is correct, closer to the floor is better, also reg to freq resp.

 

[Dave Bullet]

Hi Norcad,

My prototype design has the L26 close to the floor. I figure I'll get more even reinforcement (aka similar to ground plane) and less peaks / dips - since a "gap" between the driver and floor will cause cancellation at repeated intervals of distance for a given frequency.

Here's an example of an 8" woofer approx 60cm from the floor. Notice the dip centered around 100Hz - very similar to your simulations. There is a peak around 60Hz - which may not bode well for my L26 as the LP to the midrange causes a high Q peak around 60Hz.... may need more work.

David.

 

[Dave Bullet]

HI Norcad,

How is your project going? Did you settle on the CA26?

Cheers,
David.

 

[Norcad]

Well it goes rather well. The enclosures are (nearly) finished, they just need some painting. I have worked many hours with the xo and dampening of the midrange enclosures, to get rid of some ringing, and a peak in the 700hz area.
I have used the CA26, in a BR of 65L.
It goes lower and handle more power than I expected, so Iam rather pleased. But they are lacking a bit in the midbass, its not the "slam" that I hoped for.

The speakers sound overall very good now, and I just started to test some tweaks and adjustments on the bassenclosure, mostly damping and different pipelength. The Fb ended at 28hz, so I will try to shorten the port and test then.
I will also try the L26 one day to see how thats work, even though the enclosure are a little to small I think.

 

[Dave Bullet]

Hi Norcad,

Thanks for the update. It would be good if you could post pictures, xo schematic and xo points and any measurements so far.

Thanks,
David.