Define Subwoofer?

[Randy Bassinga]

With enough power and displacement a small cabinet can go low and loud, but it won't be efficient.

From all the way back in the early 90s, JLAudio drivers listed efficiency numbers in the low to mid 80s while the competition were rating theirs in the mid to high 90dBs. JL were begging for understanding in their publications regarding this and trying to explain that their lower sensitivity drivers would actually make for louder low bass in small boxes in cars. Today, those higher sensitivity drivers are almost extinct in car audio and regarded as old school, and we got most of the boot space back

Loudness is relative too. The ZR12.4D has dismal results for output for my intended semi pro use. This doesn't mean it doesn't have a decent output. The sims do show that this driver goes lower than most in a box smaller than most. Actually, I can't think of another 12" that will produce so much low bass with 20L only. It's going to be tricky fitting dual PR and this driver in the surface area that can be obtained from 20L! But that's the kind of crafting challenge that keeps this bwoy feeling alive

 

[Randy Bassinga]

this doesn’t look like a very good candidate for a vented enclosure? (Qes is super high, weak motor, etc) Find another driver maybe?

While trying to learn the data entry for HR, I came across this

I wonder if this has implications for WinISD too. Since the sim for the ZR12.3D has the coils in parallel as per past advice on settings regarding dedicated amp per coil, should the WinISD driver parameter for Qes be half too? The implications are the same for Le and Bl too? @weltersys @GM @WhiteDragon

 

[Randy Bassinga]

The ZR12.4D response from earlier in the thread

And with Qes/2

That ran a rolling pin over the response. Could this correction be needed with WinISD too?

 

[TNT]

"sub" = below..
"woofer" = bass.... say at highest 60 Hz... no one would claim that a speaker doing only down to 70 Hz would have any real bass/woofer...

so "below" "60Hz"... would be a sub woofer... I would say below 50Hz is a sub woofer... and even if it only reached 43Hz it would still be a sub...

;-)

//

 

[Randy Bassinga]

With a 52.8 EBP, the driver should be used in a Sealed or BP4 enclosure.

Hey man, what is this contraption called? I have been trying to digest this since yesterday. I take it that the HR sim is this box? 128dB is awesome, but I dont understand how you applied 12kw to a 1kw driver?

I am trying to learn HR right now to see if I can draw something like that too for the 10" driver

 

[BP1Fanatic]

Stepped Tapped Horn or
stepped tapped quarter wave pipe/tube.

I kept applying watts at 8 ohm (series DVC) until the 31.5mm xmax.

Probably need to do the Qes/2 correction. Usually, manufacturers provide T/S parameters based on how the coils are wired. I know Kicker does series T/S parameters with their DVC's.

 

[Booger weldz]

Hey man, what is this contraption called? I have been trying to digest this since yesterday. I take it that the HR sim is this box? 128dB is awesome, but I dont understand how you applied 12kw to a 1kw driver?

I am trying to learn HR right now to see if I can draw something like that too for the 10" driver

View attachment 1326632

is a ‘port’ that small not going to compress or create a very overdamped Fb If used as a ‘TL’ ?

 

[Booger weldz]

Taking inspiration from @BP1Fanatic (who is always a good source for interesting ideas)

an offset driver entry qw pipe works well, but every time ive created a REAL(wood) 'tapped pipe out of it(driver in the exit as shown) the 'backpressure' felt in the pipe misaligns the driver position with the resonance its normally cancelling out(not exciting) at about 1/3 from the closed end.... meeow

 

[GM]

In theory the offset s/b at its eFhm = ~34400/8/eFhm = its acoustical 1/4 WL spacing, so when loading a driver with a eFhm that puts the driver near/at or partially outside it must have a terminus extension for best results.

e = accounting for any added series resistance

 

[Randy Bassinga]

Stepped Tapped Horn or
stepped tapped quarter wave pipe/tube.

I kept applying watts at 8 ohm (series DVC) until the 31.5mm xmax.

Probably need to do the Qes/2 correction. Usually, manufacturers provide T/S parameters based on how the coils are wired. I know Kicker does series T/S parameters with their DVC's.

Thanks, will try to run some sims

Heard back from DS18 tech support case

 

[Randy Bassinga]

While trying to learn the data entry for HR, I came across this

View attachment 1326575

I wonder if this has implications for WinISD too. Since the sim for the ZR12.3D has the coils in parallel as per past advice on settings regarding dedicated amp per coil, should the WinISD driver parameter for Qes be half too? The implications are the same for Le and Bl too? @weltersys @GM @WhiteDragon

Again the reply from DS18

So HR input is sorted. The help file has instructions to config this

But WinISD feels pretty vague. I take it that in the parameter's dialogue, the switch for the coil connection is the key?

Leave that default parallel and then enter coil qty as two and then populate the rest by halving each value eg Re as half of the single coil and so on. This should then correctly update when the switch is flicked to series and back. Qes correction should done too? What about Qts, leave this for WinISD to calculate so it can flip correctly?

Let's work out the best way to populate the fields, which should be entered first and which are best left to WinISD to calculate?

 

[GM]

According to this, 10.10.15 was the last time I used WinISD Pro version and with generally fading memory recall nothing in detail and may not apply to your version.

As for summing, paralleling drivers I had a long gone Excel WS to do it and don't remember anything without researching that I don't have time for anytime soon AFAIK. All I have left is Ron E's DVC chart (attached) which I now see at a glance answer's at least some of your Qs.

 

[Randy Bassinga]

I might be onto a breakthrough with WinISD data entry for DVC. I followed the HR procedure for entering a DVC in parallel and first setup the electro side of the 10" unobtanium first

Left switch in parallel
Set voice coils as 2
Re=Re1/.2
Bl=Bl1
Le=Le1/2
Qes=Qes1/2
Znon correction
Then Cms, Mms, Qms, Vas, Xmax

WinISD calculated the Fs spot on and calculated 89dB as sensitivity. That's 3dB more than the listed 86dB that tech support confirmed as being for one coil only

Then I flipped the switch to parallel. Left Qes as Qes1/2. Corrected Znom again to 8 and Le to Le1x2. Bl and Qts had auto updated correctly

Seems consistent, what do you guys think? This could mean that the sims so far are all invalid, including the Cub Sandwich project. Maybe that extra 3dB of native sensitivy with both coils and the halving of the Qes would make the project response predictions viable again

 

[Randy Bassinga]

Let's run the mule again. The red trace is the corrected one. That's a big difference in output and response

The mule kicked 112dB over the band! That's 27dB headroom over THX base 85dB and exceeds THX reference headroom by 7dB. Not bad out of a 22L working volume. This now shows the potential to build into a tiny but potent true subwoofer. Hmmmm looking forward to running a fresh sim on the ZR6.4D armed with corrected specs. I wonder if the baby mule can kick too? @weltersys Art, the robot head may work now 😀

 

[Randy Bassinga]

All I have left is Ron E's DVC chart (attached) which I now see at a glance answer's at least some of your Qs

How incredible was that, I had just made up some wild assumptions based on instructions for HR and plugged in what I thought would be 'corrected' numbers, and returned to the thread to see your attachment. That pretty much confirms @1 coil specs need adjusting for WinISD parameters input

There is still a problem though. WinISD returns incorrect values for Bl but correct values for Vas if the Bl value is input from the datasheet, then it returns incorrect Vas. The Qes is set as Qes=Qes/2 while all this is happening. David also found this case while trying to help figure out data entry for HR, that there is an anomaly with the listed Bl

What is the weaker number? the 10.9 in the spec or the calculated 14.9? Letting WinISD calculate Bl and Vas also returns 89dB as the sensitivity

I need to understand Bl a bit better

 

[GM]

Higher is stronger

T/S Explained

T/S Equations and how each one affects the others

 

[BP1Fanatic]

I always let HR calculate Bl, Cms, Rms, and Mmd.

 

[Randy Bassinga]

Sounds good. I think I will do this for both software

 

[Randy Bassinga]

I'll build a new reference set for compact and high domestic acceptability BR/PR true subwoofers and a new set of virtual models. Let WinISD calculate Bl and sensitivity. Created another tech support case with DS18 detailing the Qes/Bl anomaly and requested details on the measuring conditions/coil connection. I'll update the sims if more info becomes apparent

Cabinet gross max 80L, ranked by output for size
F3 target 30Hz, F10 20Hz, ranked by extension for size
SPL target, equal or better than THX over the working band, ranked by headroom over THX reference for size

Next I'll set tuning higher in the 33-43Hz range. Targeting a very compact and transport and storage friendly Dub/EDub oriented subwoofer using BR/PR systems with WinISD and a scooper using HR

Drivers that can output higher SPL for max 30L driver working volume will be ranked higher

Starting with the bird in hand, the ZR12.4D, let's push it to a low extension config and a high output config in BR/PR. This is the native response with Vb=Vas and Fb=Fs. Amp is 1kw per voice coil. No Eq but there is a 20Hz highpass

Ok, after all the corrections and letting WinISD workout the Bl and Sensitivity, this mule is kicking low and hard. 115dB is 10dB above THX reference. I won’t bother tuning this lower or with a port. This driver is destined for just enough box to wear dual opposed PRs if it is to be a true sub. With only 22L driver working volume, any low reaching port system becomes a two step TL

Can she be pushed for high output? Is there another that will beat if for 33-43Hz tune out of 30L driver working volume?

Tuning raised to 43Hz in the same 22L

Would I be correctly looking at output for 4x drivers if I increase box to 88L? Trying to predict Twin x Twin in stereo array

I'll derive a 22L PR system reference subwoofer design from this driver being the bird in hand. Let's run a higher sensitivity but not as low reaching driver next to see what it will do as a subwoofer but mainly as a dub woofer

 

[GM]

I always let HR calculate Bl, Cms, Rms, and Mmd.

Something to consider is that the pioneers designed using these, so anytime I find such discrepancies I recalculate T/S to find any acoustically significant differences.