sumsound said:
Whoah - you're ignoring a couple of huge points here.
The Diyma has a flat BL curve. Dan Wiggins has shown time & time again that a flat BL curve increases efficiency at high power. This is a BIG DEAL, because the Lab 12 may have only 50% of it's BL at high excursion. As you can see from the Dumax curves, the Diyma 12 has close to 100% BL all the way to XMAX.
As if that weren't reason enough to try a Diyma, the Diyma is cheaper. On top of that, even Tom Danley and Mark Seaton discussed using an XBL woofer for the lab sub. They discussed this on audioasylum AND the prosound forums.
Please keep this in mind before dismissing the Diyma.
sumsound said:
4fun said:
Why would I?
The Lab12 has a conventional motor; therefore BL will be down to a fraction at xmax. The Diyma has a flat BL curve; therefore it will have lower distortion and consistent response at high excursion. Period.
That simple fact is one of the biggest reasons that high excursion drivers often sound so crappy - you really need to flatten the BL curve. Otherwise you're going to have a tremendous amount of distortion at high excursion, AND you're frequency response will vary with excursion.
I don't want this to turn into a discussion about BL curves though; Dan Wiggins has practically written the book on that one.
If you would like to discuss the merits of a flat BL curve, let's open a new thread. It's safe to say that the Diyma's flat BL curve is "a good thing."
:: PB ::
Hello all,
Interesting topic this is going to be. Modeling a tapped horn with akabak is definitely the way to go. In the past i also were getting close simulationresults when modeling Cowan`s Tapped Horn.
A useful option in akabak is to use label (very simpel). Give your front- and backside a label. This way you could plot the soundpressure (and a lot more) of each side seperate. If you do this you wil see that Akabak is putting its soundpressure`s together related with the phase/distance (as expected).
What Akabak doesn`t show how a configuration like the tapped horn has a impact on the cone excursion.
A check what can be done is putting 2 seperate drivers on a horn with a fixed distance seperated from eachother. Put each backside of the driver in a closed box or grounded to zero (your choice).
Now simulate the cone excursion of the driver towards the mount on two different ways;
1.) with the driver at the mount driven only
2.) with the driver at the mount driven and the one at the beginning with reverse phase (180degr.)
Check the cone excursion, does it make a difference?
About a other question:
I think the motor of a driver on a tapped horn is on the outside because;
1.) it provides (theoretical) cooling to the motor
2.) if you want maximum output with a given input, you must place as much as the driver allowed (related to BL, Mass and stifness of the cone) a certain compression ratio (and a resistive load like a horn can present). A big compression ratio normally means you don`t have enough room for the motor.
Cheers,
Marcel
Interesting topic this is going to be. Modeling a tapped horn with akabak is definitely the way to go. In the past i also were getting close simulationresults when modeling Cowan`s Tapped Horn.
A useful option in akabak is to use label (very simpel). Give your front- and backside a label. This way you could plot the soundpressure (and a lot more) of each side seperate. If you do this you wil see that Akabak is putting its soundpressure`s together related with the phase/distance (as expected).
What Akabak doesn`t show how a configuration like the tapped horn has a impact on the cone excursion.
A check what can be done is putting 2 seperate drivers on a horn with a fixed distance seperated from eachother. Put each backside of the driver in a closed box or grounded to zero (your choice).
Now simulate the cone excursion of the driver towards the mount on two different ways;
1.) with the driver at the mount driven only
2.) with the driver at the mount driven and the one at the beginning with reverse phase (180degr.)
Check the cone excursion, does it make a difference?
About a other question:
I think the motor of a driver on a tapped horn is on the outside because;
1.) it provides (theoretical) cooling to the motor
2.) if you want maximum output with a given input, you must place as much as the driver allowed (related to BL, Mass and stifness of the cone) a certain compression ratio (and a resistive load like a horn can present). A big compression ratio normally means you don`t have enough room for the motor.
Cheers,
Marcel
Without the klippel measurements of the LAB 12 I can't comment on the linearity of the BL in regards to Xcursion. So any argument in that department is hearsay at the moment.
As far as I understand it a good Xmax rating is the linear response region of the coil in the gap. I'm sure some companys are more conservative with their ratings than others.
I have done some Quad lab 12 sealed subs, and not heard any percievable distortion from pushing them down into the Teens, I have heard amps clip through them which is sort of a -pocking- sound.
It is to my understanding and experience that many of the Xtra high excursion drivers generate other unwanted mechanical suspension, pole and coil venting noise.
If to much distortion from suspension and BL non-linearity occours, doing a push pull configuration can help pnumaticaly reduce some of that distortion.
It also looks like a well tuned vented encloure could not be acomplished with that driver.
I have done some push pull vented boxes for the lab 12's and they are stupid clean, I use them for a bass bi amped bass rig often. It is imposible to make the Growl, like most of the dirrect radiator bass rigs I've played through. Its a very subtle smooth sound.
I know around the edge of Xmax distortion is going up, but its not very bad at all with the labs.
I'm not sure what your experience with them is but distortion has never been a problem both in swept measures subjective listening.
I'm willing to take the Pepsi Chalange with the Labs Vs Diyma sealed sub anyday.
Reduced Distortion in my opinion is good, better and best. I have seen some audiophile sites rate subs with higher harmonic distortion better than louder lower subs with less because the thought the ones with more distortion sounded fuller. I guess thats where the term musical comes in.
For my system criteria I had a maximum attainable SPL/Power bandwidth requirement in the smallest possible enclosure. They Diymas wouldn't make it there even with twice the power.
Anyhow thats my rant, without the missling BL excursion curve, and side by side listening tests and measures we can't really make any conclusions.
Antone-
As far as I understand it a good Xmax rating is the linear response region of the coil in the gap. I'm sure some companys are more conservative with their ratings than others.
I have done some Quad lab 12 sealed subs, and not heard any percievable distortion from pushing them down into the Teens, I have heard amps clip through them which is sort of a -pocking- sound.
It is to my understanding and experience that many of the Xtra high excursion drivers generate other unwanted mechanical suspension, pole and coil venting noise.
If to much distortion from suspension and BL non-linearity occours, doing a push pull configuration can help pnumaticaly reduce some of that distortion.
It also looks like a well tuned vented encloure could not be acomplished with that driver.
I have done some push pull vented boxes for the lab 12's and they are stupid clean, I use them for a bass bi amped bass rig often. It is imposible to make the Growl, like most of the dirrect radiator bass rigs I've played through. Its a very subtle smooth sound.
I know around the edge of Xmax distortion is going up, but its not very bad at all with the labs.
I'm not sure what your experience with them is but distortion has never been a problem both in swept measures subjective listening.
I'm willing to take the Pepsi Chalange with the Labs Vs Diyma sealed sub anyday.
Reduced Distortion in my opinion is good, better and best. I have seen some audiophile sites rate subs with higher harmonic distortion better than louder lower subs with less because the thought the ones with more distortion sounded fuller. I guess thats where the term musical comes in.
For my system criteria I had a maximum attainable SPL/Power bandwidth requirement in the smallest possible enclosure. They Diymas wouldn't make it there even with twice the power.
Anyhow thats my rant, without the missling BL excursion curve, and side by side listening tests and measures we can't really make any conclusions.
Antone-
4fun said:
Can anyone find Dumax on the Lab12? I'd like to see them too.
However, we can get close, no doubt. Mark Seaton has stated online that the Adire Audio Shiva was a bit of an inspiration for the Lab12. The Shiva Dumax results are tough to find, but here they are:
http://www.adireaudio.com/Files/ShivaDUMAX.jpg
The pic above shows that BL is down to 50% at 10mm of xmax. This loss of BL will increase distortion, and change the response of the woofer at higher excursion. In fact, even the T/S parameters change! This is A BAD THING. I wouldn't be surprised if this is the reason that Adire has focused on XBL designs.
Here's a thread where I discuss the motor design of the Diyma with it's inventor:
http://diymobileaudio.com/forum/showthread.php?t=7660&highlight=dumax
Klippel measurements of the Diyma 12 are here (note it's impressively flat.)
http://www.diymobileaudio.com/shop/...id=32&osCsid=0ee687dd4b0db28a5be5b2a97b7c00d0
Hi ,
I'm still trying to get my head round horn design , but I'm very keen to make some sawdust and build a tapped horn regardless . This driver keeps the budget low and with MDF at £12 per 8x4 sheet an overall cheap project
http://www.bkelec.com/HiFi/Drive_Units/BSB/bsbl12-100.htm
...would this be suitable for the Cowan 30Hz design ? The xmax is not quoted but I won't be using at ridiculous sound levels . Would it be worth a try ?
cheers
316a
I'm still trying to get my head round horn design , but I'm very keen to make some sawdust and build a tapped horn regardless . This driver keeps the budget low and with MDF at £12 per 8x4 sheet an overall cheap project
http://www.bkelec.com/HiFi/Drive_Units/BSB/bsbl12-100.htm
...would this be suitable for the Cowan 30Hz design ? The xmax is not quoted but I won't be using at ridiculous sound levels . Would it be worth a try ?
cheers
316a
(that woofer looks to have very little usable xmax-?)
back to modeling, would anyone here like to make some generic/labled node Akabak diagams based upon William Cowan's 30Hz horn and simplified waveguide entry? (-could be as -is and then with driver offset?)
--that would help those who wish to evaluate various drivers (including me haha)
It was suggested to me that a simple model may suffice as with the following script:
| William Cowan 60 Hz tapped horn.
Def_Driver 'Dr1'
| Eighteen Sound 10W400.
Sd=350cm2
fs=70Hz
Qes=0.44
Qms=3.99
Vas=31L
Re=5.1ohm
Le=1.2mH
ExpoLe=.734
System 'S1'
Driver Def='Dr1' Node=1=0=3=4
Waveguide 'W1' Node=2=3 STh=275cm2 SMo=306.7cm2 Len=13cm Conical
Waveguide 'W2' Node=3=4 STh=306.7cm2 SMo=713.5cm2 Len=128.5cm Conical
Horn 'H1' Node=4 STh=713.5cm2 SMo=770cm2 Len=14.5cm Conical
***************
GRAPH
http://img234.imageshack.us/img234/9523/60th18soundwq3.gif
back to modeling, would anyone here like to make some generic/labled node Akabak diagams based upon William Cowan's 30Hz horn and simplified waveguide entry? (-could be as -is and then with driver offset?)
--that would help those who wish to evaluate various drivers (including me haha)
It was suggested to me that a simple model may suffice as with the following script:
| William Cowan 60 Hz tapped horn.
Def_Driver 'Dr1'
| Eighteen Sound 10W400.
Sd=350cm2
fs=70Hz
Qes=0.44
Qms=3.99
Vas=31L
Re=5.1ohm
Le=1.2mH
ExpoLe=.734
System 'S1'
Driver Def='Dr1' Node=1=0=3=4
Waveguide 'W1' Node=2=3 STh=275cm2 SMo=306.7cm2 Len=13cm Conical
Waveguide 'W2' Node=3=4 STh=306.7cm2 SMo=713.5cm2 Len=128.5cm Conical
Horn 'H1' Node=4 STh=713.5cm2 SMo=770cm2 Len=14.5cm Conical
***************
GRAPH
http://img234.imageshack.us/img234/9523/60th18soundwq3.gif
G'day Freddi
Those numbers are available in the tapped horn section of my homepage. The 30Hz horn actually works better with several different drivers. The XXLS 830847 for example is a better performing driver than the XLS 830500 in this tapped horn. Try a few and see how you go.
Cheers
William Cowan
Those numbers are available in the tapped horn section of my homepage. The 30Hz horn actually works better with several different drivers. The XXLS 830847 for example is a better performing driver than the XLS 830500 in this tapped horn. Try a few and see how you go.
Cheers
William Cowan
G'day 316a
Now that simple AkAbak scripts are available, I no longer recommend the use of Hornresponse to model Tapped Horns. The script that Freddi showed above was actually written by David McBean who wrote Hornresponse. I'm led to believe there is a possibility that Hornresponse may do tapped horns in a later version.
Cheers
William Cowan
Now that simple AkAbak scripts are available, I no longer recommend the use of Hornresponse to model Tapped Horns. The script that Freddi showed above was actually written by David McBean who wrote Hornresponse. I'm led to believe there is a possibility that Hornresponse may do tapped horns in a later version.
Cheers
William Cowan