Likwitz Transform and Xmax / Xlim

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Well, I can certainly say I have learned a lot in the past 24 hours or so. I corrected the mistakes I made with my earlier sims of the PD184C01 but I am not getting good results with a closed cabinet.

I could use two 15" drivers but this means less cone area. From my understanding more cone area results in more natural bass and that is what I am after. I arrived at an 18" sub as this seems to be the largest size driver that can be fitted into an enclosure of a reasonable size. I know there is much debate about the directionality of bass but perhaps I will one day build a 2nd 18" sub :D.

Anyway, I did some sims of the Dayton Audio UM18-22 'Ultimax' - yes that sounds manly!! I must have it :p. These sims are looking very good. Not sure if I'm applying the correct EQ filters though as I am not familiar with all the effects of these.
 

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Neither matter much . . . the graphs which tell all are SPL and Cone Excursion.

Sorry, but read my post again. You can EQ a tiny box to have the same SPL and cone excursion (remember there's a direct relation between the two) as a very large sealed box. The only difference will be the power requirement. Dropping 10kW into a 10L box isn't sensible. The "Apparent Power" tab tells you what is.

Chris
 
Anyway, I did some sims of the Dayton Audio UM18-22 'Ultimax' - yes that sounds manly!! I must have it :p.

Yeah, now you're talking Jasp! This driver will make a much better sub. Now let's ditch that wimpy plate amp and at least power your rig with one of these: Behringer: iNUKE NU3000

You will need more headroom with 10dB of LT boost and plate amps like that for the most part are a waste of time. There's no need for high passing to protect the driver either, just learn the limits of your system and if you need more output, add drivers and power.

Also, I wouldn't build your LT circuit until you build your sub and verify it's close mic response. WinISD is great but you never really know what you're going to get until you slap one together.
 
I could use two 15" drivers but this means less cone area. From my understanding more cone area results in more natural bass and that is what I am after.


2 15's will offer more displacement potential than 1 18". That means you will have more headroom for peak SPL with less distortion. The whole more cone area = more natural bass is ridiculously not true. Because you are using a sealed enclosure with an LT, you can put the drivers in a smaller than ideal box, dial a suitable curve into the LT to counter the sharper knee in the response curve and throw more power at the sub.
 
Generally speaking, more cone area = less excursion for a given frequency, SPL, etc. Bigger cone areas are also usually more efficient given an adequately sized box. So you're using less power and less excursion than a smaller driver. If the two drivers are of comparable design, the bigger driver ought to have lower distortion. A 6" driver doing 90dB at 30Hz with 1% distortion (and a given distortion profile) will sound exactly the same as a 21" driver doing 90dB at 30Hz with 1% distortion and the same distortion profile.

Chris
 
How do we reconcile these opposing views?

I could use two 15" drivers but this means less cone area. From my understanding more cone area results in more natural bass and that is what I am after.

^^^ This is what I was responding to. The issue was two 15" drivers vs. one 18" driver. Let us assume they both have the same xmax -22.5mm and that we have ample amplification to power both systems.

First, the (comparable driver) 15's Sd is 856cm^2 and the 18's Sd is 1178.41cm^2. So 2 of the 15's equals a cone area of 1712cm^2 which is considerably more than a single 18.

Figuring that both the 15's and the 18 have the same xmax that gives a total for the single 18 of 5.3 liters of displacement and 2-15's have 7.7 liters of displacement. The 2 15's will not need to throw as far as the single 18 so they will stay more linear and therefor have less distortion for the same SPL. The 2-15's will also be more capable of producing higher SPL especially at lower frequencies where higher displacement is required.

As for the "more natural bass" comment, you can't assume that a larger piston diameter automatically accounts for less distortion. If you have an 18" driver with 8mm xmax, and compare it with a driver like this: HST12 12″ Subwoofer | Stereo Integrity
with an xmax of 38mm...

...at 20Hz, the 18" has a peak SPL capability of 96.6dB and the 12" has a peak SPL of 102dB. So in this case the 12" driver will most likely stay more linear for the given frequency at 97dB and therefor produces less distortion than the 18" which is at it's mechanical limits at the same SPL.

I tend to shy away from describing what a sub system will do with sentences like more natural bass because it doesn't really mean anything specifically. Sorry Jasper, I don't mean to get down on you and I'm certainly not trying to start a fight here, just sayin' that it's beneficial for understanding to stick to the data.
 
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^^^
I tend to shy away from describing what a sub system will do with sentences like more natural bass because it doesn't really mean anything specifically. Sorry Jasper, I don't mean to get down on you and I'm certainly not trying to start a fight here, just sayin' that it's beneficial for understanding to stick to the data.

No, worries. I know that audio if full of all kinds of myths so for me it is more a matter of cutting through those and finding out how to build something that will actually function as desired. All of this is really helping me along. I have been doing some sims of two smaller drivers in one box and those look interesting.
 
Originally Posted by shredhead View Post
................ The whole more cone area = more natural bass is ridiculously not true. .............
Originally Posted by chris661 View Post
............. If the two drivers are of comparable design, the bigger driver ought to have lower distortion. ...............
How do we reconcile these opposing views?

^^^ This is what I was responding to. The issue was two 15" drivers vs. one 18" driver. Let us assume they both have the same xmax -22.5mm and that we have ample amplification to power both systems.

First, the (comparable driver) 15's Sd is 856cm^2 and the 18's Sd is 1178.41cm^2. So 2 of the 15's equals a cone area of 1712cm^2 which is considerably more than a single 18.

Figuring that both the 15's and the 18 have the same xmax that gives a total for the single 18 of 5.3 liters of displacement and 2-15's have 7.7 liters of displacement. The 2 15's will not need to throw as far as the single 18 so they will stay more linear and therefor have less distortion for the same SPL. The 2-15's will also be more capable of producing higher SPL especially at lower frequencies where higher displacement is required.

As for the "more natural bass" comment, you can't assume that a larger piston diameter automatically accounts for less distortion. If you have an 18" driver with 8mm xmax, and compare it with a driver like this: HST12 12″ Subwoofer | Stereo Integrity
with an xmax of 38mm...

...at 20Hz, the 18" has a peak SPL capability of 96.6dB and the 12" has a peak SPL of 102dB. So in this case the 12" driver will most likely stay more linear for the given frequency at 97dB and therefor produces less distortion than the 18" which is at it's mechanical limits at the same SPL.

I tend to shy away from describing what a sub system will do with sentences like more natural bass because it doesn't really mean anything specifically. Sorry Jasper, I don't mean to get down on you and I'm certainly not trying to start a fight here, just sayin' that it's beneficial for understanding to stick to the data.
your well reasoned explanation is welcome. I will not try to refute it.

But your statement
The whole more cone area = more natural bass is ridiculously not true.
as shown by the argument in your later post is quite simply untrue.
 
I said "your well reasoned explanation is welcome"

I did not say "it is simply untrue".

It is your earlier statement saying "The whole more cone area = more natural bass is ridiculously not true." that I am claiming is untrue.
Your following argument proves to me that the earlier blanket statement can only be untrue.
 
As for the "more natural bass" comment, you can't assume that a larger piston diameter automatically accounts for less distortion. If you have an 18" driver with 8mm xmax, and compare it with a driver like this: HST12 12″ Subwoofer | Stereo Integrity
with an xmax of 38mm...

As I said in my post, this isn't a fair comparison:

Generally speaking, more cone area = less excursion for a given frequency, SPL, etc. Bigger cone areas are also usually more efficient given an adequately sized box. So you're using less power and less excursion than a smaller driver. If the two drivers are of comparable design, the bigger driver ought to have lower distortion.

The two drivers you're comparing are not of comparable design, as you've shown.

Lets compare some drivers that are of similar design. They're based around the same motor, and therefore have similar excursion characteristics and power handling.

http://www.beyma.com/getpdf.php?pid=18P1200Nd/N
and
http://www.beyma.com/getpdf.php?pid=15P1200Nd/N

If you give both of them adequate cabinet volume and aim for the same low cutoff, the bigger driver will have more swept volume available, and will be more efficient.
For a given SPL, then, it'll need less power and less excursion than the smaller driver. Unless they've performed miracles, this should mean the bigger driver will have less distortion.

Chris
 
I get it Chris, I'm just showing Jasper a case where it isn't true to teach him because you didn't specifically tell him why it would have to be drivers with similar motors and suspensions. I still disagree with describing it as more natural sounding, there are bass players out there who push tube amps until they are soaked in distortion and they describe it as more natural sounding.

Jasper just a heads up, the plate amp that you were initially considering will not be able to drive the ultimax to xmax.
 
Jasper just a heads up, the plate amp that you were initially considering will not be able to drive the ultimax to xmax.

Yes, I've realized that. ATM I have completely changed direction - I'm thinking of using a 12" driver now. I saw this project using a 10" sub and PR yesterday and quite like the idea. I could try something like this with a 12" driver as a 10" seems a bit small. I did some sims with a PR and they look good in terms of box size, power requirements, and cost. I'm now thinking of a Peerless XXLS 830845 with a PR in a 60L box.
 
I get it Chris, I'm just showing Jasper a case where it isn't true to teach him because you didn't specifically tell him why it would have to be drivers with similar motors and suspensions. I still disagree with describing it as more natural sounding, there are bass players out there who push tube amps until they are soaked in distortion and they describe it as more natural sounding.

Fair enough, just wanted to make sure everything's clear - the internet forums aren't the best way of communicating.

"Natural sounding" is very subjective, though, so I think we can leave that one ;)

Chris
 
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