Infra sonic subwoofer design

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#41
#44
Oh that's the 14KW clone amp with the 120V 15A line cord.

The original Lab Gruppen 14000 manual's power specs section consist of technobabbleand it runs on 230V/16A which is 3680VA. It's really no better, so save the $ and get the Chinese one.

The spec says/means the Po is limited by the mains breaker. It is certainly limited by the power cord melting anyway. It's just another 1000-1500W household amp. If it were a 14KW amp it would need 230VAC @120A. The cord would be just a little bigger.

Is RMS continuous power still used for rating amplifiers?

I'm sorry but I was disappointed with this. Oh well looks too good to be true then it is.
 

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#45
I'm not an amp guy so I don't have much to say about this from a technical standpoint. I haven't read the whole thread that I linked to but a lot of the heavy hitters in that forum are very impressed with that amp and I would be very surprised if they hadn't tested it thoroughly to verify the specs. Users are recommending no less than a dedicated 30 amp circuit. Regardless, I'm sure it puts out more than 1500 watts. IIRC people are saying it easily beats 4 EP4000 amps and those do 2400 wrms each, so I'm told.

Here's a few shots of the power cord. Apparently it now comes with a larger cord than it used to but I don't know what gauge wire is in there. The second and third pics compare the new cord to the old one.

183856


183857


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From here : Lab Gruppen FP14000 clone amplifiers
 
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#46
I do believe it's a good amp design or people wouldn't be buying it or paying so much for the genuine model.

No claim here that the amps can't do the 14K in short bursts, for music purposes.

Don't like the way that short duration peaks of output power are presented in the literature as "continuous".

It's just words but they mean things.

To me, the word 'continuous' means a solid RMS power level sustained indefinitely. I sort of live in the industrial world where certain words are used very strictly.

So I was annoyed, seeing the word "continuous" used in a way I considered inappropriate.

Anyway, where is the OP? I still want to read his requirements and/or comments on the solutions offered. The SI woofer said 450W, the amp in discussion would drive them to ruin.

I downloaded some speaker box software and manually entered that huge SI Ht 18 woofer. Had to edit in into a file manually, because the in-program editor kept blowing up. That thing is not so smooth in Win 7. no complaints though, it produced good curves. I should start a topic just for my woofer situation and leave this topic.

Have you or anyone ever experienced his 10hz requirement bodily? I should try headphones and an oscillator+DC amp but it's probably not the same.
Maybe this Sunday I could ask the organist after church if he has the 16Hz on the pedal. There's a mix of tube and SS amps. huge speakers, but low-ish power like 100W for bass, very efficient.
 
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#47
An interesting "classic" 10" Carbon fibre/Paper cone driver (probably there are more), that does 10Hz in a 200L enclosure with less than 30W (25.0 W/6.7 Ohms@15.5 Hz) (29.8 W/5.6 Ohms@318.8 Hz). (This is) If everything is right?! It must have also excellent dynamics close to ~90dB sensitivity. Obvious don't take it at max. SPL/power/Xmax under 15Hz to 10Hz because elongation (16.5mm@12.94 V)=>Xmech(12mm) at infra-sound 10Hz. 😀
Scanspeak Classic 25W/8565-00, 10" Woofer
http://www.scan-speak.dk/datasheet/pdf/25w-8565-00.pdf
 
#48
opcom said:
... I should start a topic just for my woofer situation and leave this topic.

Have you or anyone ever experienced his 10hz requirement bodily? I should try headphones and an oscillator+DC amp but it's probably not the same.
Maybe this Sunday I could ask the organist after church if he has the 16Hz on the pedal. There's a mix of tube and SS amps. huge speakers, but low-ish power like 100W for bass, very efficient.
Click to expand...
Did you use the software I linked on post #27?! It's free and might give you a good simulation of your room acoustics.
What drivers/speakers are you using? 😕
 
#50
tittualex said:
Thank you all, for all your comments... I will be using the sub in a room with dimn. (18'x10'x10'). rotary sub woofer is way too costly and i cant make much alterations to my room for fixing the rotary sub.

Alex
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Hi Alex,

Why not first test your 🙂eek: oddly dimensioned 😀) Room Infra Performance by using an inexpensive Woofer:

Example:

http://www.diyaudio.com/forums/subw...oupled-infra-bass-speaker-31.html#post2879125

See the Picture:

FYI: Used Software (Use Google Translate for the thread!):

http://www.faktiskt.se/modules.php?name=Forums&file=viewtopic&t=53868

b 🙂
 

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#51
PPSL IB

just a guy said:
Like I said, I've seen pics of 3 rotary subs used in a home theater no larger than yours. I can't find the pics right now but they are out there somewhere. Let me repeat - the number of subs required (rotary or conventional) has a lot to do with the room (construction, leakage and size), the desired spl and the available budget.

Just because you are happy with one in your room doesn't mean much to anyone else. You haven't listed any specs, room details or anything else, all you've stated is a completely subjective judgement that doesn't mean anything to anyone except you.



Again, let me repeat - There's no doubt that the rotary sub is impressive but it could easily be beat by conventional drivers (in multiples) given the same budget and size limitations.

I'm not sure what colorations you think conventional subs are subject to that rotary subs are immune from, but physics says they can both do the same job just fine and with low distortion. In fact, the conventional drivers won't have any fan noise to filter out (and no matter what you do you'll never completely eliminate the fan noise).

Saying that your rotary sub only uses 200 watts is not really true either. The 200 watts is only for pitching the blades, and that's not what creates the acoustic power. The fan itself creates the acoustic output and it uses a 1/3 hp motor IIRC, which runs full speed ALL THE TIME, not just when needed like conventional drivers. So if you add up all the power the rotary sub uses it will actually be more than conventional drivers would use.t

Besides, $1200 for a 200 watt amp? You can get 14000 watts rms these days for well under $1000 shipped to your door, all fees and taxes included.

Even so, it doesn't take all that much power to get a bunch of conventional drivers to hit xmax at 3 hz, I don't think you'd need anywhere near 10000 watts to beat your rotary sub with conventional drivers. I haven't run the numbers but I'm confident that I could beat your rotary sub by quite a bit (in terms of max spl, distortion and ambient noise) with conventional drivers with a fraction of budget and using no more space than you currently use. There was a time (even just a few years ago) when conventional drivers were quite expensive. But prices are falling exponentially and will continue to fall as time goes by. The rotary sub can't compete any more unless it's dramatically cheaper than it used to be.

AFAIK this is the current value leader in LF conventional drivers, and next year there will be something even cheaper.
Stereo Integrity | HT Subwoofers - 18 inch driver
Stereo Integrity | Order Online - price list

10 of those drivers and a 14000 watt amp are less than $3000 total. For the $15000 you paid you could get more than 50 of those drivers and at least 5 of the 14000 rms amps. You do the math.
Click to expand...

Certainly look up PPSL IB designs with the 18" subs linked above. And look into powering them with a Crest prosound amp channel for each 4 ohm woofer (two used CA 9s). A little EQ and sawdust and your operating at under $1500. I run 4 AE IB15 woofer two per channel PPSL IB with a Crest CA12 and bass can make ones hair vibrate.
 
#53
bjorno said:
Example:

http://www.diyaudio.com/forums/subw...oupled-infra-bass-speaker-31.html#post2879125
Click to expand...

Are you suggesting that he build the Holiman infra bass sub?

It's been several years now but I seem to remember someone (wasn't it you?) that simulated that thing with Akabak and it didn't do anything below 30 hz. Then someone built and measured it and it didn't do anything below 30 hz.

I don't have time to search through the many extremely long threads about that sub but I thought the consensus was that it was a huge waste of time by today's standards and did not produce any infra bass at all.

Regarding the pic you posted, I can't blow it up to full size (probably a computer problem on my end) but it seems to just show room simulation software, the link doesn't mention the GH infra bass speaker at all. What are you trying to say with this?
 
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#54
just a guy said:
It's been several years now but I seem to remember someone (wasn't it you?) that simulated that thing with Akabak and it didn't do anything below 30 hz.
Click to expand...

It was actually really easy to find. I don't have time to read through it all now but it was you that simulated it, and it looks like whatever you simulated could hit 20 hz.

Hi,

Posting some simulations showing reflex boxes is at least as capable as the Holliman infra speaker for frequencies below the lowest modals occurring in a room.

B
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Simulations here. http://www.diyaudio.com/forums/subw...oupled-infra-bass-speaker-10.html#post1051920

Also posts 96, 97, 98 and 100 might be interesting.

I spent this weekend a lot of hours testing this Holliman phenomenon with a real setup (40L box and Peerless XLS 10”) and came to the conclusion that the high efficiency 5 to 25 Hz bandwidth probably is only a myth for this type of infra speaker.
Click to expand...

This was back in 2006 when I didn't know anything about anything, and ironically I thought this thing was going to work and you proved it wouldn't. Now you are recommending it and I'm not.
 
#58
Inductor said:
Did you use the software I linked on post #27?! It's free and might give you a good simulation of your room acoustics.
What drivers/speakers are you using? 😕
Click to expand...

Not tried yet (whichever post # it was on), no time to do it due to work.. woofers are old 15" eminence, 20 yrs old, so.. I'll do it, but can't right now.

I did talk to the organist at church. He has a 32' stop and demonstrated it with the lowest note on the organ. He showed me a subwoofer having a long excursion 12" driver and a port, the box was about 6 cubic FT. This is somewhat irrelevant because I don't yet know the frequencies involved, not knowing the questions to ask, as in "what note is that?" duh!!. I feel better about being able to achieve what I need though.
 
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#59
I already posted that correction, read again ---(#56)--^^
Now are you in the same church as OP?
I thought you had the funny shape room from post#21.
Yes a 12" can do that, as a well chosen 10" with limited input, as I showed on post #47.
If for a pro use with power to the limit, then use the BMS 18N860/2 with max. 1500W power will play the infra-range, with a theoretical max. 127.0 dB (SPL/1m). Do you need a sub for the church too of for your home?!
If for home use the 15" SB Acoustics SB42FHC75-6 Woofer with 300 W, goes to 10Hz and a theoretical limit of 118.2 dB.
I heard that infinite element analysis type of software it's the only kind that can simulate the music rooms, I guess bjorno's is also one. But hey I'm repeating myself.
Have fun. 🙂
 
#60
weltersys said:
A manifold can have just two opposing drivers, or 3, or 4 or more.
Normally the back of the manifold is simply a wall, you suggested putting an additional driver there, just like Anicom did with a three sided manifold.

Showco did have a four driver pyramidal arrangement which worked OK around the same time period (probably the inspiration for the Futz), as would a tetrahedral arrangement with only three drivers.

The 3 (or in your suggestion) four side drivers are all pushing air, the air pressure is at maximum in the center. The rear cone is also pushing air, but is also pushing against the maximum concentration of pressure, and is subjected to more pressure than the rest of the cones.

Extreme throat pressure causes cone flex, which causes distortion, even if it does not lead to cone destruction, as it did with the rear driver in Anicom's Futz arrangement.
I have tested many horn loaded units for distortion, the distortion at a given excursion is more than the front loaded counterpart.
A quad loaded manifold gives around a 3/1 compression ratio, higher than many horn cabinets.

After tearing up the rear cones a number of times, if I recall correctly, the Anicom guys put a plate over the place where the cone was, and had no more problems running three drivers. Those JBLs were very expensive, they learned the hard way that the back cone would not hold up.

The cabinet still was a pig though, the efficiency of a large sealed cabinet could not compare to the rest of their horn loaded system.

Art
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The back driver should receive the same net pressure as the rest, at least below plenum 1/4 wave resonance.
However I would expect the pressure to be uneven with less pressure at the edges. Causing the cone to flex radially in a triangular pattern and break due to that.
Four sides would create less pressure difference I imagine.
 
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