New sub design? Constricted Transflex, simple build (series tuned 6th order)

[freddi]

hi X - I should have some Pyle pym1298 laying around - what might they do in such an arrangement? they were built by Eminence and advertised a 95oz magnet. Probably not "sub duty" but two in parallel should have some kick.

* Power handling: 600 watts RMS/1200 watts peak * Voice coil diameter: 3" * Nominal impedance: 8 ohms * DC resistance: 5.28 ohms * Frequency range: 40-4,000 Hz * Fs: 46.9 Hz * SPL: 97.8 dB 1W/1m * Vas: 4.02 cu. ft. * Qms: 5.69 * Qes: .29 * Qts: .28 * Xmax: 3.2 mm. List price: $149.00.

 

[GM]

These measured? Otherwise, here's an Eminence production sample: PYLE AUDIO PYM1298 OWNER'S MANUAL Pdf Download.

GM

 

[freddi]

hey GM Big thanks! - no - those were just something spat out on the web - - that data sheet looks representative and pym1298 was pretty much the same as Kappa12a. Nice response curve - funny how the rear sticker says 95oz magnet when it appears to be same as Kappa's 80oz. Then again, Eminence's new 42oz B102 slug looks the same from the outside as the old 59oz slug so there must be a hole diameter difference in that case. pym1298/Kappa12a are real nice woofers. I'll dig out a pym1298 in a few days and give it a WT3 run. I've used 1298 in a little Karlson 12 with a K-tube on top - preferred that combo to my 10 cubic foot bulk Peavey FH1 with 511/KV55 + APT150 - the horn system was of course somewhat louder but the little Karlson more articulate and punchier - and that was with a distributed slit vent K12 which would distort like hell on sine at fb - but drums, etc. aren't like sine.

 

[Matthew Morgan J]

Versatile marketing!

I dig XRK's four-pointed star shaped symmetrical aperture ... That could work on a Karlflex too , hmmm

Could extend the bottom point of the aperture forming a Christ's cross shape making those cabinets highly marketable to churches...... and gothic dance clubs ... haha

Turn that same bass cabinet upside down and sell them to metalheads and metal /deathmetal venues!

BRILLIANT !!! (Brilliant! get it? thats a star pun , hehe)

 

[Matthew Morgan J]

hi X - I should have some Pyle pym1298 laying around - what might they do in such an arrangement? they were built by Eminence and advertised a 95oz magnet. Probably not "sub duty" but two in parallel should have some kick.

* Power handling: 600 watts RMS/1200 watts peak * Voice coil diameter: 3" * Nominal impedance: 8 ohms * DC resistance: 5.28 ohms * Frequency range: 40-4,000 Hz * Fs: 46.9 Hz * SPL: 97.8 dB 1W/1m * Vas: 4.02 cu. ft. * Qms: 5.69 * Qes: .29 * Qts: .28 * Xmax: 3.2 mm. List price: $149.00.

Freddi ,
That is very interesting! I never knew that the "Sound Around" guys in New York had ever sourced anything from Eminence ("Sound Around" owns of a long list of different budget brands including Pyle, Lanzar, Pyramid, Brand-X , Legacy ) ........
Sourcing more of their drivers from Eminence would probably help those brands build a better reputation, over time, a long time .....

 

[freddi]

some internal reflective paint and disco lights inside and that cross would fly!

 

[Matthew Morgan J]

some internal reflective paint and disco lights inside and that cross would fly!

LOL !
Every cool and hip modern church should have a herd of these!

Those Eminence/Pyle drivers look like they would work well in one of these 6th order designs ... A little more xmax would be nice of course but other than that they look good

What were these Pyles selling for when they were available?

I think multiples of these simple little 60L to 90L Karlflex (and similar) 6th order cabs loaded with highly affordable drivers is the way to go .... The decibels really begin to add up when you have multiples and the cost/output/bandwidth value really makes a lot of sense ....... I am preparing some graphs and cost comparisons to post on here to explain what i am talking about ...... With the right drivers these boxes can definitely be very competitive with other alignments ...

Speaking of Sound Around products they make a Lanzar MAX ST series that got plenty of great reviews from users , and they have the right "small box" specs according to what is published + gobs of xmax ..... The Max12-ST and Max8-ST might be good low cost alternatives as subs, but i would want to buy one to verify the T/S parameters with my DATS ...

 

[freddi]

seems like pym1298 were around $70-78 in the day - the cheap shipping box just had a ring of cardboard instead of what Eminence had started using. I want to know how to do the disco lights so they're self-contained, and won't burn out - just be as good in gradations as Robbie The Robot's mouth would suffice. 1298 would probably have to be a "hit" box driver as there's just not enough xmax even with a pair to go deep.

 

[chips and palsa]

C&P,

You are welcome - it was fun to get some akabak going again and it confirmed my suspicion that the XKi really controls cone motion well. This sub is not excursion limited but rather power thermal limited and velocity vent compression limited. I have not worked out box dimensions but probably 5 cu ft external volume with wood thickness and vent volume (assuming 0.5in for vent walls).

I could believe how quick it came together! I need to learn AkAbak...

The only issue (and I hate to say this) is that my lab12 cab is approx. 100L external (22x18x16) so 60L internal, I should have been more specific =(

Is it even worth looking into an XKi that size for these drivers? MMJ's Karflex seems great now that we can potentially get this port velocity down! What did you mention about reaching 30m/s but it being manageable since it was behind the aperture?

Thanks for the help guys!


Sent from my iPhone using Tapatalk

 

[xrk971]

The code is right there for you to try. I posted a script for the XKi earlier and this one just required an extra driver and extra vent. So two more lines of code copied and pasted. Changed the TS params and set the volume and vent dimensions. That was it.

When the vent is behind the front baffle - any sound resulting from chuffing is really diminished and not as noticeable as a direct vent to the outside. The thing you have to deal with is turbulence which may cause port compression (meaning flow is less than you think). As long as you keep port velocity well under speed of sound by 1/10 the speed of sound or Mach 0.1, port compression should not be a problem. Mach 0.1 is 43m/s.

 

[Matthew Morgan J]

Yep ! Thats right ....
I would also like to add that when the constriction is not at the end of the path (but rather mid-path) there is a much reduced likelihood of any kind of port compression and chuffing since according to theory the velocity is much reduced in the middle of the path (as opposed to the very end of the path) at FB ...

This strategy applies or can apply to most of the designs we have been discussing including the Karlflex , XKi , Karlsonator , this double Alpine box that XRK just presented to us etc and so on .................

In other words air particle velocity should not be as much of an issue just as long as we have designs that employ a significant length with increased area or expansion placed after the constricted portion of the path with the end of said section feeding the mouth/terminus/aperture ...

 

[GM]

Yeah, when one studies up on flared vent design, the goal is either only a flare or two flares coupled together with no straight tube connecting them, so the pioneers viewed a baffle thickness vent as a very short tube with a rapidly expanding flare. It doesn't work this way of course, but WRT vent 'chuffing' it works well enough as long as it's CSA is at least 1/4Sd and < a ~1:1.273 aspect ratio, so chuffing isn't as issue with typically large K-slots. In theory, they shouldn't be >Sd for bass only apps.

GM

 

[xrk971]

C&P,
I managed to dig out my ancient laptop that has Akabak on it. So I managed to sim your case of using two SWS-10D4 drivers in a 100 liter or smaller box with 35Hz (f3) and maximal SPL output.

The design I came up with is similar to an XKi but with dual vents to reduce air particle velocity near resonance. Make the box 13in wide internally and make the rear chamber 60 liters and the front 30 liters. The vents are 13in wide x 1.5in tall x 28in long (qnty 2 vents). The drivers are angled a bit to prevent parallel-parallel interference. The output aperture is equivalent to a 13in diam round hole.

Here is the predicted max SPL at 12mm displacement (I did not want to go to actual xmax levels to keep it linear and to have head room) at 90v RMS. It is a 125dB design with -3dB point at 35Hz:

Here is predicted cone displacement with a 30Hz -24dB/oct BW high pass filter to avoid over excursion:

Here is the particle velocity in the vents and output aperture - it hits 30m/s in the vents but this is shaded behind the Karlson aperture so I don't think it is a problem:

Here is the electrical power input - about 1.5kW:

Here is the code:

| 6th order band pass sub for dual Alpine SWS 10D4
| xrk971, Feb 13, 2015

System 'XKi'

Def_Driver 'SWS-10D4' 
Sd=479cm2 
Qms=8.65 
Qes=0.49 
fs=35Hz 
Vas=25L  
Le=4.84mH  
Re=7.0ohm | Wire DVC in series for 7ohms, then parallel drivers for 4ohm nominal

Filter    'High Pass' fo=32.5Hz  vo=1.0  {b4=1;  a4=1;  a3=2.613126;  a2=3.414214;  a1=2.613126;  a0=1;  }  | 4th order BW HPF

Driver Def='SWS-10D4' 'Driver 1' Node=1=0=300=400  | connect driver here node 1=amp, 0=GND, 300=front cone face, 400=rear cone face

Driver Def='SWS-10D4' 'Driver 2' Node=1=0=300=400  | connect driver here node 1=amp, 0=GND, 300=front cone face, 400=rear cone face

Enclosure  'Back Chamber'  Node=400  Vb=60.0L  Qb/fo=0.707  Lb=12in  | Chamber 1 node 400

Duct    'Vent 1a'  Node=400=300    wD=13.0in hD=1.5in Len=28.0in  | Vent 1a between chamber 1 and 2

Duct    'Vent 1b'  Node=400=300    wD=13.0in hD=1.5in Len=28.0in  | Vent 1b between chamber 1 and 2

Enclosure  'Front Chamber'  Node=300  Vb=30.0L  Qb/fo=0.707  Lb=8in  | Chamber 2 node 300

Duct 'Vent 2'  Node=300=501  dD=13.0in  Len=0.75in  | Vent from chamber 2 to outside (same CSA as K-aperture)

Radiator 'Duct Rad1' Def='Vent 2' Node=501 Label=20  | Radiator element on vent 2

I am going to build a small prototype using a pair of Tang Band W5-876SE's. Should be able to get an fb of 45Hz and keep very compact with an impressive higher SPL capability that you would not expect from a pair of 5in drivers.

 

[Matthew Morgan J]

I am going to build a small prototype using a pair of Tang Band W5-876SE's. Should be able to get an fb of 45Hz and keep very compact with an impressive higher SPL capability that you would not expect from a pair of 5in drivers.

Should be a potent miniature bass box!
I would imagine that it would model very closely to a traditional helmholtz based series tuned 6th order alignment ..

 

[Matthew Morgan J]

Yeah, when one studies up on flared vent design, the goal is either only a flare or two flares coupled together with no straight tube connecting them, so the pioneers viewed a baffle thickness vent as a very short tube with a rapidly expanding flare. It doesn't work this way of course, but WRT vent 'chuffing' it works well enough as long as it's CSA is at least 1/4Sd and < a ~1:1.273 aspect ratio, so chuffing isn't as issue with typically large K-slots. In theory, they shouldn't be >Sd for bass only apps.

GM

This is good guidance & background GM , thank you .... So when experimenting with different Apertures for bass only apps the exit's CSA can be between 1/4 to x1 the driver's SD, is that correct?

 

[GM]

You're welcome! Correct, just depends on the front chamber volume/effective compression ratio the driver can safely handle at rated power.

GM

 

[xrk971]

Should be a potent miniature bass box!
I would imagine that it would model very closely to a traditional helmholtz based series tuned 6th order alignment ..

I think it is a 6th order series tuned alignment. The difference being the Karlson "star" aperture and shallowness of the front chamber will give it a wide bandwidth compared to a traditional 6th order bandpass. I am hoping to get above 300hz on the top end.

 

[Matthew Morgan J]

Been pondering this possibility for a while now ....

I think it is a 6th order series tuned alignment. The difference being the Karlson "star" aperture and shallowness of the front chamber will give it a wide bandwidth compared to a traditional 6th order bandpass. I am hoping to get above 300hz on the top end.

XRK,
You have a talent for modeling 6th order boxes in Akabak, and you also have the code for DCRs right?, so out of curiousity have you ever tried integrating the DCR feature into a 6th order box in sim?
I think i may have an idea for a DC-Karlflex , I will post a concept sketch when i finish scribbling one up that looks easy enough to build .... If the DC feature works properly then it could be a way to squeeze out some more SPL and efficiency from drivers that lack linear cone travel like the Dayton Pa310 or Freddy's Pyle/Eminence , or an Eminence Definimax 12 or any number of other drivers with humble XMAX ratings but otherwise good parameters. ...

 

[GM]

As in 8th order K15?

GM

 

[Matthew Morgan J]

As in 8th order K15?

GM

I have looked at the K15 before ,
Is it considered 8th order because of the shelf that splits the front chamber?