from the soundcheck thread..

yep, its my own "little" beastie, 3.4m "supercurved" smooth constant expansion 26hz fc hyperbolic horn, loaded with pd1850, taken best part of a year learning about horns and reading the wise words of other whilst loitering round places like this.. and then the cutting... let alone design n learning autocad etc

anyway yep we like our noise, but it was tested at points, as much as could be done with a bridged peavey cs1000

i did wonder if anyone here would have noticed hehe

i'm sure theres a few that may b interested, trying to get construcion photos sorted on a website.. maybe start next week

al

it looked a bit different to say the least. is it possible to stack them?

well, they have a large mouth (only built one so far tho) and i designed them to work in pairs side by side or for a bit of serius bass with four; on their sides, two on bottom two on top. having said that one seemed really good with a bit of eq in 2pi, so should be absolutely fine in 0.5pi due to boundary reinforcement and cabin gain.

oh and it took 3-4 of us to move them cos i hadnt had time to put handles on yet.. hopefully tonight, when theres enugh of us at home to lift it back up the stairs from the van

the only problems with a stack of four on their side would be u cant sit in the middle, which was very nice indeed. (30hz massage at 130+db 18mm from your back, lying down in one) and everything needs strapping down, or they might walk away..

have you got any pictures? it looked like the horn path was cut from one peice of wood - it's difficult to explain.

was it folded in the normal way? or more of a curved horn (like a trombone)?

here is a cad screenshot. the red line is disecting the outer center of the rear chamber.. the horn profile and this rear chamber section are cut from one sheet of ply per side.

" border="0" />

or http://img205.echo.cx/img205/1898/terrahorn7ie.png - http://img205.echo.cx/img205/1898/terrahorn7ie.png

its not teknically folded as such,  you can see its curved around the 2 corners, i havnt read any research,  but as far as i can imagine sound waves can propagate with less friction/turbulance or eddys round a smoothed corner rather than the bp effect of right angled corners in most folded horns.. dont forget standing waves and back reflections too, reducing efficiency.. which isnt taken into account in horn response... this may even lead to the possibility of a much higher crossover point if so desired, because it more resembles a "warped" straight horn. i havnt as yet tried it above 90hz.

got loadsa photos, but theyre all on my gf computer.. half in sequence of construction. still waiting for slide film of the horns escapades at the teknival to come back..

@ timber, yep i'm sure your right talking wavelengths, but have you ever tried tugging a ratchet strap round a 180 degree panel, then around a smoothed curve.. i can imagine pushing air being the same: less friction and turbulance and reflections.

anyway it is kind of less practical but looks the  bollox, and is less "compromised" 

@mike i'll get some photos sorted soon

yes, i dont know much about the kf940 but i think it has 9ft pathlength and claims something like -3db at 22hz, meaning the driver is surely running below horn fc, i dont know what methods they employed to get this but i imagine a very high compression ratio in the throat chamber..

apples and oranges are tired> more like eels and wasps comparrisons (pet favourite)

what i'm asking is, is pushing 9 feet of air (then the rest in the audience space) with 2x12" drivers or 11ft of air and the rest with one 18" really as important as all the other factors, like compression ratio, pathlength, fc and driver parameters...let alone i dont intend to push out 22hz eq'd to -3db with one horn? 

but i hope its ok, and yes you could be right, better keep an ear on it

 al

minaximal wrote: that i'm asking is, is pushing 9 feet of air (then the rest in the audience space) with 2x12" drivers or 11ft of air and the rest with one 18" really as important as all the other factors, like compression ratio, pathlength, fc and driver parameters...let alone i dont intend to push out 22hz eq'd to -3db with one horn?  but i hope its ok, and yes you could be right, better keep an ear on it  al

Wait and see I guess!I think its a function of the acoustical impedence now applied to the driver - combination of compression ratio and horn itself. Maybe a low compression ratio will help...

 If you HPF correctly, and use the right amount of power nothing untoward should happen.

Timber_MG wrote: @ tb_mike. THe concerns JD01 raises are not with over-excursion, but I think one should just give it a go (it is a PD1850 after all)

I know,I want to take it out of the equation and see if the cone will survive if well implemented but with an unknown horn load

well, i tested it for about 24hours non stop(apart from genny's running dry every 5 hoursish) at just below clip with a bridged cs1000.. so 1100w is clip, and other people here have suggested 1200w nominal idealy 2000w for headroom with a pd 1850. (was it julz powered 3.5k into one for fun once with no probs)

the compression ratio is highish at 2.5, but shouldnt be too bad i hope, i used angled flares on either side of the baffle like roborg, for more direct/smoother/reduced throat entrance.

i'm unsure as to how the acoustical impedance will be affecting the system, and the electrical impedance has its worst dip to 6ohms (bearing in mind this is one cab in 2pi so 2 cabs should be smoother)

fc is at 26hz and displacement at 34hz should be around 10.3mm 1 horn 2pi, (1850= 11.25 xmax the overstated way) this is where i set my hpf l-r 24db, but i would like to experiment a little lower... idealy with another cab at least.

and it all seemed fine!..so far

mate sat inside enjoying the bass; not very good photo, its obviously from behind the stack, still waitibg on other photos.

With reasonable power the speaker won't 'disrupt' but it will get a soft cone with time if the load is too high. The thing about that is that an 11' horn just has to have a high loading, otherwise there is no sense in having such a long horn (IMO). That is the result of the horn transformation. The radiation resistance must be pretty high.

One thing about the old CS line from Peavey: They all have slight highpass of 3dB per Oct (dunno how this is possible but it is the truth). That means they are 3dB down at 50Hz vs. 100Hz. That stops around 100Hz. I noticed it many times in AB comparisons, where other amps had noticeably more output around 40-50Hz, but the CS just pushed harder around 100Hz (all amps same output power).

In addition to that a CS1000 bridged isn't a really good amp for driving horns. I learned that while trying to drive four CV T36. Each had its own bridged CS1000, so around 1000W per cab. But it just didn't perform that well. Nowadays I use a LAB Gruppen fP6400 set to 1680W per channel at 4 ohms for all four (so 840W per cab) and it works much much better. It's a difference that is very noticeable with the plain ears.

Soft cone eh?????? Use a non paper cone then.

How about Beyma 18P1000 then???? SPECIALLY TREATED CONE WILL NOT TEAR IN A FOLDED HORN CABINET & CAN WITHSTAND SEVERE OUTDOOR CONDITIONS  And EV  EVX-180B uses a ribbed kelvar fibre cone.

http://www.usspeaker.com/homepage.htm - http://www.usspeaker.com/homepage.htm

And some Fane Collosus speakers use  Polycellulose cones.

that beyma seems interesting, but its mostly hype. it may not "fold" in a horn loaded cab but it would bottom out first due to its lowish bl and highish qts. its not very suited to long horns, because it wants a low compression rate and large rear volume to go down low and then becomes less compliant and will exceed its emax.. which is the same roughly as the pd1850, but thats more compliant.

i guess its a bit of a trick to have a high bl and lowish mmd with a very stiff cone, and then suspension must come into check also.

@jJD01

thats quite interesting about the cs amps, would that be a way to get around having a lowish damping factor of around 200 in bridge mode. or do you think damping is just a red herring.

the only reason we use it is for lack of £££. 

i intend to run some sine tests today, maybe i'll check voltage at different frequencys then to see if the affects of this are noticed in frequency specific power output!?

minaximal wrote: that beyma seems interesting, but its mostly hype. it may not "fold" in a horn loaded cab but it would bottom out first due to its lowish bl and highish qts. its not very suited to long horns, because it wants a low compression rate and large rear volume to go down low and then becomes less compliant and will exceed its emax.. which is the same roughly as the pd1850, but thats more compliant. i guess its a bit of a trick to have a high bl and lowish mmd with a very stiff cone, and then suspension must come into check also. @jJD01 thats quite interesting about the cs amps, would that be a way to get around having a lowish damping factor of around 200 in bridge mode. or do you think damping is just a red herring. the only reason we use it is for lack of £££.  i intend to run some sine tests today, maybe i'll check voltage at different frequencys then to see if the affects of this are noticed in frequency specific power output!?

Red herring. Any resistance present in the speaker cable will ruin manufacturers Dfactors of ten hundred billion ,down to 50 or so.

Some run negative output impedence to cancel Voice coil Re,while some 'synthesise the inverse of the loudspeaker properties' to achive,um something -some sorta non reactive load,duno how practical.

People are hearing differences between amps,I dont know how,Havent experienced it myself not enuf amps around.

Mike.e

"Red herring. Any resistance present in the speaker cable will ruin manufacturers Dfactors of ten hundred billion ,down to 50 or so."

Crown Delta Omega 2000 has feedback sense leads to go directly to the drivers to negate speaker wire resistance.

_djk_ wrote: "Red herring. Any resistance present in the speaker cable will ruin manufacturers Dfactors of ten hundred billion ,down to 50 or so." Crown Delta Omega 2000 has feedback sense leads to go directly to the drivers to negate speaker wire resistance.

Thats all good and nice sounding,but what are the practical results?

Saw a circuit in Electronics Australia suggesting how to do this.

the delta omega amp was also introduced in 1982, it doesnt look like they still bother employing the technology any more...?

i ran some tests on my horn for the last two days, and it seems that the (very old) cs1000 amp does start to drop its voltage;

 at ^45hz-30hz;  to 50v (300w) (@30hz) 8r bridged a bit after the hpf kicks in whilst still keeping nearly as close to clip with same sensitivity as at ^45~100hz where it is around 90v (1000w) maybe an extra -2db~3db on top of filter!? (L-R 24db at 28hz)

the amp was fairly constant maybe even picked up a bit after it dropped and stayed 40v at 26hz.  this wasnt the most scientific of tests, my laptop soundcard and sigjenny/cheap multimeter, may have introduced drops in gain, but pretty sure its mostly the amp, (or maybe inductance) is this a problem of other amps also.. cheaper components maybe? 

back to the horn though,

1/4watt! at 26hz makes the whole building shake, but 40v  at 26hz as stated above was the most the amp could throw at it also with the hpf set. and that was intense! everything started falling off the walls and shelves, and horn started vibrating around the room..(its 110kg at the mo')

strangely the only panel ressonances were from my house walls and some screw holes i made just after the throat whilst glueing the layers together,which i had forgotten to fill, which made the horn whistle, until i worked out where it was coming from i was a bit worried after that with only the two sheets of 4mm ply layerd up so far the panels seem fine.

need to rta it really (see if i can get the mic today).. surely if other amps drop voltage at lower frequencys rta's may not be that much to compare..

hopefully get photos today..

People are hearing differences between amps,I dont know how,Havent experienced it myself not enuf amps around

Most obvious difference would be the headroom of the amp. Most cheaper amps are made that way that they begin to distort long before you see the leds indicate clipping. With my own cheaper amps I can hear the distortion at +/- -6dB

Higher quality amps begin to distort much later, sometimes even already after it's clipping. Of course this will affect the sound and thus create a difference.

Wkr

Please tell me that this ain`t someone in your "terrahorn"?!!!

http://www.imageshack.us">

They`re gonna need that stretcher ......?

.p.

phildekked wrote: Please tell me that this ain`t someone in your "terrahorn"?!!!   http://www.imageshack.us/"> They`re gonna need that stretcher ......? .p.

hehe, that photo's great, yer i tried crawling in also at a quiet point and then some jungle bassline came on and scared the sh*t outa me, felt like it blew me back out, becaues of the sound pressure. tom jones spent most of his time in there though gaurding it for us.

i have been away for a bit, and photos are still on gf's mac, i'll see what i can do.

i found out a few days after doing some tests that a niegbour four houses down on the other side of the road was freaking out because his whole house was rattling and rumbling, and he was running around between each room trying to find out what was háppeníng.. so it work quite well

bahaah thats the stuff!!

Even though 140dB of 32hz in your flat isnt that practical,I still crave it its ridiculous. My mind keeps reminding me 'build the jbl 2226 horn'