C/E/X PA Flat to 30 (FT30) PA TH Awesomeness

This thread is a continuation of woody1's thread (flat to 40Hz) which can be found here: http://www.diyaudio.com/forums/subwoofers/170749-15-tapped-horn-rcf.html

Epa, Xoc1 and others have been contributing their time and effort in attempt to help me reach my goal: Flat to 30Hz with as much clean output as possible - XTRA points for breaking physics and keeping it small. Heh.

We have found 15" drivers are limited by xmax far before maximum power is reached.

Here's where we left off:

Post 73 (Epa) @ 2.83V
30Hz = 95.28 dB
40Hz = 98.58 dB
3.3 dB difference

cres2.jpg




Post 98 (Xoc1) @ 2.83V
30Hz = 96.17 dB
40Hz = 100.74dB
4.57 dB difference, so step from 30 to 40 Hz is 1.27 dB more...

197479d1290430180-15-tapped-horn-rcf-bms18n850v2-6-fold-th-1.jpg

197480d1290430180-15-tapped-horn-rcf-bms18n850v2-6-fold-th-2.jpg




My REAL 6 Fold mod (I meant to post) @ 2.83V
30Hz = 98.29
40Hz = 98.48
0.19 dB difference, so step from 30 to 40Hz is 4.38 dB less AND 2.12 dB more output at 30Hz

18N850v2REAL6foldmod690WInputParameters.jpg

18N850v2REAL6foldmod690WSPLResponse.jpg

18N850v2REAL6foldmod690WDiaphragmDisplacement.jpg

18N850v2REAL6foldmod690WSchematicDiagram.jpg


What's your take on this version?


Post 98 is more efficient at both frequencies as would be expected as it is bigger. External is 600 litres compared to 397 for post 73.
Biggest misgiving I have about the post 73 design is the small S3 dimension.
At 1236 this is about the same size as SD. You can see how tight the mouth is positioned to the rear of the driver. This would require care and adjustment to make it work due to the driver seriously restricting the mouth. I suppose an access panel would be needed to actually get the driver in the box!:eek:

restriction is not to bad because of the neodinium magnet.
ff%20iets.jpg

i designed the post 73 th for the use in a cardroid sub aray.
this is why its symetric.
i like xco1 model 2,its a easier bild but for me a little to big.

i wil work this weekend on it to give you al the details;)
meanwile here are some designs,most of them are posted here.to make your choice more diffecult:p
kies.jpg

Must they (post 73) be used in a cardioid sub array? Will I/we loose any performance if they're not?


yes the idea was to make the front parts removeble :)
(Referring to post 73)

ok lets make it 15mm.i think 18 is a bit over the top.
horizontal there are only small spaces ,and vertical wil do some bracing in the middle.
front wil be removeble in one piece.
it might be a good idee to send you the dwg,dxf file when im finnished.
then you can make a 1 on 1 print on A0 paper(it fits)in the copy store.
cost about 4 euro here on this side of the pond:)

justin ,we need to make a new topic,because this has no longer anything to do with woodys design ,:nownow:

Welcome :)


Any others: feel free to post your design if you believe it betters any of these and fits the goal posted above. Many thanks!

Justin
 
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Note: I will be crossing over at 80 or 100Hz, so designs need only be flat up to that point.

Note: I would rather the low end freq response drop off after 30Hz than drop off after 40Hz. A lot of material played has 25-30Hz focus.

So far, I'm debating between Xoc1's modded 6 fold (Xoc1.m) also referred to as 'post 98', my 2nd modded 6 fold (Xoc1.cm) and epa's small (392L) symetrical fold (epa.sm) also referred to as 'post 73'. The following table will show each of these designs maximum output (all xmax limited) and coincidentally use the same driver (BMS 18N850v2). The mathematical xmax of 16mm one-way, is used for these calculations:

Box
Freq ______30_____ 35_____ 40_____ 55_____ 65_____ 80_____ Hz

Xoc1.cm: _126.5___ 127___ 126.5__ 126.5___ 127____ 127_____ dB
Xoc1.m: __125.8___ 129.2__ 130.1__ 130.1___ 130____ 130
eps.sm: __124.7___ 127.2__ 127.7__ 127.6___ 127.6___ 127.8

Below is a .txt file if you would like to update this info for your own use or to add and re-post for further comparisons.
 

Attachments

  • DIY Sub Comparisons.txt
    262 bytes · Views: 240

Xoc1

Member
2008-11-08 8:25 pm
Devon UK
aprox same volume /same output,but easyer bild , actualy 400 ltrs (not 440)
oops:eek:
Been out and about this weekend
Saw Leftfield in concert
18 off TSW218 turbosound bass cabs so 36 x 18" 104dB/W hornloaded drivers and Turbosound Aspect point source PA very nice.:D:D
As it is not possible to break the laws of physics a choice has to be made. Basically size can be traded against efficiency.
Crescendo you will need to make a choice, based on what you are prepared to carry and what amplification you have available.
The bandwith of the cab is 30 to at least 100hz I would be wary about introducing a dip in the response above 100hz especially if the real cab response does not match the sim exactly.
My personal choice would be for efficiency, its easier to turn the bass down rather than up!
 
no ,its just easy'er to use in csa stacks if they are symetrical.

Got it

Xoc1.m moddel is 601 ltrs,minus the cutoff bit at the bottem where you can nicely fit 2 casters for easy transport.
i can't find the drawing of the Xoc1.cm ?

There are only hornresp jpegs - the 3rd on this page (1st is your small TH aka epa.sm, then Xoc1's modded TH aka Xoc1.m, and finally my modded TH aka Xoc1.cm

aprox same volume /same output,but easyer bild , actualy 400 ltrs (not 440)

woody.jpg

Lookin this one over now - looks nice. I'd definitely appreciate a simpler build and easy transportability. I'll be lookin over these closely.

oops:eek:
Been out and about this weekend
Saw Leftfield in concert
18 off TSW218 turbosound bass cabs so 36 x 18" 104dB/W hornloaded drivers and Turbosound Aspect point source PA very nice.:D:D
As it is not possible to break the laws of physics a choice has to be made. Basically size can be traded against efficiency.
Crescendo you will need to make a choice, based on what you are prepared to carry and what amplification you have available.
The bandwith of the cab is 30 to at least 100hz I would be wary about introducing a dip in the response above 100hz especially if the real cab response does not match the sim exactly.
My personal choice would be for efficiency, its easier to turn the bass down rather than up!

Oh nice! Those Turbosound TSW-218s are monsters! I heard 8 inside a warehouse - SPL levels were ridiculously high. I loved it :cloud9:

I was half joking about breaking physics. Epa's small design plays about as loud as the one I modded, but the one I modded has 2.3 more dB at 30Hz. That's what I was referring to as breaking physics - his was smaller and AS loud, for the most part. I know I won't get em ALL ;)

Again, I want the focus to be 30Hz and flat from there. That's where I would need to turn it up, so like you said, start with something that's loud at 30Hz to begin with.

Xoc1, you are excellent at bringing more efficiency to designs - props to you! I'm wondering if you or epa could bring more efficiency (from 30Hz) to the Xoc1.cm hornresp design I posted above :scratch2:

These will be used for mobile apps, so wheels/casters are sought after.
Power? I'm sure a QSC PLX3402 will fit the bill nicely and can be found online for nice prices. I've got an RMX2450 atm - so, I'll be able to do shows with that in the meantime.

Once again, many thanks,
Justin
 
does it need to go flat to 30 with 1 speaker ,2 or more per side?
this makes a big difference.
i woulden't be wise to give up spl for something you dont need.
i agree with 30 hz f3(i like the real lows 2:D) ,when you use 2 or more it wil be flat until 30 .

also would you post a bit of music (low notes).you want 2 reproduce.
i like 2 examen that.
in woody,s topic i posted a sample of a real low c synt. that was 32 hz centre freq.
 

Xoc1

Member
2008-11-08 8:25 pm
Devon UK
I suppose that the overall limitation would be what size events you are trying to cater for. Four of the large cabinets in a row would be impressive if your prepared to transport that volume of speakers. There might be a problem with bass steeriing if 4 cabs are lined up. J Bell has commented on using delays on the outer speakers with 4 of his big TH cabs to widen the soundfield.
http://www.diyaudio.com/forums/subwoofers/170550-help-needed-choosing-design-live-sound-2.html
Problems arise when the upper freqency wavelengths are smaller than the width of the cabinets. Without processing mid bass beaming is the result!
Are you planning on using a DSP such as a DCX2496 or a Driverack?
 
Right now, I feel the only thing limiting me to do larger shows is lack of sound. I currently do shows for a few hundred people and they all want their clothing and nose hairs to vibrate.

SUVs and trucks I have used are typically ~48" wide and fit 2 Titan 48s side by side (24" wide/ea).

Yes, I currently use the DR260
 
I suppose that the overall limitation would be what size events you are trying to cater for. Four of the large cabinets in a row would be impressive if your prepared to transport that volume of speakers. There might be a problem with bass steeriing if 4 cabs are lined up. J Bell has commented on using delays on the outer speakers with 4 of his big TH cabs to widen the soundfield.
http://www.diyaudio.com/forums/subwoofers/170550-help-needed-choosing-design-live-sound-2.html
Problems arise when the upper freqency wavelengths are smaller than the width of the cabinets. Without processing mid bass beaming is the result!
Are you planning on using a DSP such as a DCX2496 or a Driverack?
this can be dealth with by using an inverted arc.
justin is going to cross @ 100 hz max(3.4mtr wave length) therefore ,4 or less shouldn't be a problem imo.
 
Thanks for running those scans. As we can see, 30Hz reproduction would be valuable in my case.

Also, I further see the value in high efficiency designs, even if a single cab doesn't grab the low end - your Xoc1.m sample above proves it's flat to 30Hz w/4 cabs :yummy:

What program are you using to scan the files?
 
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