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minaximal View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote minaximal Quote  Post ReplyReply Direct Link To This Post Posted: 01 June 2005 at 10:43pm

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



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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 02 June 2005 at 4:28am

Originally posted by minaximal 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.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timber_MG Quote  Post ReplyReply Direct Link To This Post Posted: 02 June 2005 at 4:33am
@ 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)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 02 June 2005 at 5:14am

Originally posted by Timber_MG 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

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minaximal View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote minaximal Quote  Post ReplyReply Direct Link To This Post Posted: 02 June 2005 at 9:15am

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

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timber_MG Quote  Post ReplyReply Direct Link To This Post Posted: 02 June 2005 at 4:04pm
The 1850 is noted for it's mechanical stability mind you. Fo rfun you could try popping a Craaft super lightweight 18 in there and play catch with the cone (you did mention the curved sections)
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minaximal View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote minaximal Quote  Post ReplyReply Direct Link To This Post Posted: 03 June 2005 at 9:58am

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

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Post Options Post Options   Thanks (0) Thanks(0)   Quote JD01 Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2005 at 11:11am

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.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom Umney Quote  Post ReplyReply Direct Link To This Post Posted: 04 June 2005 at 12:09pm

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

And some Fane Collosus speakers use  Polycellulose cones.

 

 

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minaximal View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote minaximal Quote  Post ReplyReply Direct Link To This Post Posted: 05 June 2005 at 9:41am

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!?

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Post Options Post Options   Thanks (0) Thanks(0)   Quote tb_mike Quote  Post ReplyReply Direct Link To This Post Posted: 06 June 2005 at 7:52pm
Originally posted by minaximal 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

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Post Options Post Options   Thanks (0) Thanks(0)   Quote _djk_ Quote  Post ReplyReply Direct Link To This Post Posted: 06 June 2005 at 10:29pm

"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
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