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Will be renting a van next week to pick-up a pair of 4520. Current owner has 8 of them. He keeps 4 to himself and I get a pair. One pair up for grab, Eaulive...
They are empty and dirt cheap. Only catch is that they were painted white as they got rented for a movie that pictured the early 1980s disco era. Movie is called "Funkytown". I will load the 4520s with the 2225h I already have.
They can be seen here.
Attachment 50355
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I' going there at 5.... damn clock is so slow.....
Argh, delays, traffic, rush hour, guy still at work.
Going there later.
I made some quick calculations.
The 4530 had a 7ft scoop - meaning 43Hz resonance at 1/4 wave
The 4520 is 12ft scoop - meaning 25Hz at 1/4 wave. And a mouth that is more than twice as big.
25Hz resonance would be a waste with drivers such as a 2225h which has Fs 40Hz and dies at 30Hz. I am not looking for sound pressure as the 4520s will be in my basement. I have four good 2225h currently in use and four 2225h baskets. Thinking reconing the 2225h baskets as 2235h with Fs 20Hz. It could be interesting. The 2245h I already have will be in a separate sub "to fill holes".
Hmm... Or maybe not. If indeed the 4530 is tuned to 25Hz and that the 2235 has a lower Fs, I will end up with excursion problems, pretty early. Damn.
The 4520 is useable down to 30Hz, below this the woofer is unloaded and will get damaged, unless you keep it at low levels. Of course, with this kind of hardware "low" is relative :D
I know that these are the "official" values for the horn length, but I could not verify them. Get some construction plans and check Yourself.Quote:
Originally Posted by Lee in Montreal
The frequency response plotted in the 4520 brochure seems realistic to me. The 2225 seems to be a good driver for these horns. The 2235 would be killed in a minute.
Where are You going to place them? How big is the room?
Ruediger
Here they are...
Attachment 50388
Quote:
Originally Posted by Eaulive
Ah, ah. Eaulive did it too. :D
In fact we are sharing the four remaining 4520s. I will pick mine up next week.
$200 a pair including speaker clamps is a good price... And they are now famous after showing up in a disco movie. :eek:
They will do the job until I build some modified versions with twin 18" drivers. Not Waldorf yet but taller than stock.
Official JBL litterature claims a 13ft path for the 4520 vs 7ft for the 4530.
http://www.jblpro.com/pub/obsolete/l...nclosures2.pdf
I have a hard time understanding how it could be close to twice as long however I measure it. But Eaulive did gave measures of the respective mouths in a previous thread. 5650cm2 vs 3078cm2 and I think this is where the huge difference in tuning frequency comes from. The larger the mouth, the lower the resonance.
Mouth size and path length. Looking at Bertha's (simple W bins) with the Levan extension, it seems it makes sense. But don't worry. I have no intention to install Berthas in my basemement unless I want to end my couple. :D But damn wouldn't it be great to load them with two 2242... That sure would piss off all neighboors within a block.
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Si I met Eaulive this afternoon while he was picking his set of 4520s. I have put my name on a set for myself. Eaulive went thru a dozen of K130 2220A and 2205A to test them. I will be going back to pick up my bins next week after I clear my garage (there's a racecar on jackstand in there). I will perhaps be selling my 4530s to Eaulive's friend. Therefore the number of enclosures will not be changing in my listening room as I am replacing a pair of 4530s for a pair of 4520s. I'm safe, my GF can't say a thing... ;)
Lee
Nice to meet you this afternoon Lee.Quote:
Originally Posted by Lee in Montreal
Yes, the speakers I tested didn't convince me so much. There was six 2205A, one K130, one K140, one 2231A and seven 2220A if I remember well, all reconed as 2225 except one 2205A that was having the original cone.
I tested the six 2205A with a pink noise and only two were matched in sound, all the others were sounding different... I won't be buying any of them :eek:
I just checked Lee, the 2231A seems to be the ancester on the 2234/5, a HIFI driver, rolled surround, same magnet and coil as a 2225 but heavier cone (almost as heavy as the 2235)
Currently looking at ways to position the 4520s in my listening room. I was thinking laying them flat on their side, drivers on the outside, and mouths together (bottom to bottom), in order to double mouth perimeter from 32.75" x 26.75" = 10ft to 20ft in twin configuration.
So by doubling the mouth perimeter, by how many Hertz can a lower the cut-off? My understanding is that 20ft perimeter is 28Hz at 1/2 wavelength.
The pair of 4520s that I used for the Church installation had 2226 in them.Quote:
Originally Posted by Eaulive
The low bass was effortless, but I put most of my budget into speakers so I ended up using a PL700 to drive them. I figured I would upgrade the amp later but never felt the need to do so.
Soon after the system was setup in the Church we did a kids program based on the Indiana Jones theme. There was an earthquake scene in the program and the sound track had an earthquake sound for about 30 seconds. Little did anyone realize what was about to happen. The kids had been practicing to a boom box and had been instructed to just jump around when they heard the quake sound.
On performance day I added 15db of boost at 80hz from the mixer channel and opened up the channel to full gain,,, and the whole room shook!!!!;) The kids didn't have to jump around as the stage was shaking, the people were shaking in the pews.:bouncy:
Everyone loved it, so I got to keep my job.:blink:
You're assuming the wrong "physics". Get Yourself either "Acoustics" from Beranek or "Acoustical Engineering" from Olson. A book which gives You an idea of how horns work, and that without mathematics (!), is "Hi-Fi Loudspeakers and Enclosures" from Cohen.Quote:
Originally Posted by Lee in Montreal
Ruediger
Well, please explain, because PA guys do just that to lower the "reach" of their bass bins. ;)Quote:
Originally Posted by Ruediger
Not to mention that any exercise in horn design goes thru the mouth perimeter to define cut-off frequency.