Oh no. I did it. JBL 4520 related

[Lee in Montreal]

That is equation 14 from the Keele paper. It is about front loaded horns, not about rear loaded ones, or am I missing something?

Ruediger

I will check further. From memory it was for rear loaded horn, but I might be wrong. Being wrong is part of the explorative process

[Ruediger]

What You need is equation 24 in the Keele paper. The back chamber in the Keele paper is for reactance annulling - You don't have that. The front cavity in the Keele paper is Your back chamber.

Fhc = 2 * Qts * Fs * Vas / Vfc

Vfc = 2 * Qts * Fs * Vas / Fhc

For the 2225H and 150 Hz this yields 25 liters. Sounds okay.

Make a plot of the phase of sound from horn mouth and from front of diaphragm. then determine cutoff frequency, and thus chamber volume.

ruediger

[Lee in Montreal]

THanks very much. BTW I will use two 2240h. The 2225h barely reach 30Hz while the 2240 have Fs 30Hz.

[Ruediger]

THanks very much. BTW I will use two 2240h. The 2225h barely reach 30Hz while the 2240 have Fs 30Hz.

Driver resonance frequency is almost irrelevant. You should really have a look at the books I recommended in the past. The Keele paper tells You the Flc for a non-short horn. What You build is a short horn with resonances.

ruediger

[Ruediger]

Found an old article in two parts. Part 1 contains the plots which I meant.

See page 2 in part 1. The exponential horn and the hyperbolic horn have no useful radiation resistance at "cutoff". Above cutoff the hyperbolic horn has a high resistance, and the exponential horn has a low resistance.

See page 4 in part 1. The locations of the resonance peaks are determined by horn length. The magnitude of the peaks is determined by horn mouth area.

ruediger

[Lee in Montreal]

Thanks. That's some long reading for the weekend.

Lee

[Eaulive]

Yeah, I will let you guys design it, if it sounds good I'll build it

[Lee in Montreal]

Found a nice calculator to shape the horn's progression.

It does exponential and hyperbolic. The 4520 is exponential while the Waldorf is hyperbolic, which is a strange decision as, according to some reading, hyperbolic horns are rone to distorsion.

http://fullrangedriver.com/singledriver/exphypcalc.html

[Eaulive]

Look at this: http://www.flickr.com/photos/blowin/...448104/detail/

Looks like modified 4530s, with an 18" driver

[Lee in Montreal]

Look at this: http://www.flickr.com/photos/blowin/...448104/detail/

Looks like modified 4530s, with an 18" driver

...And a small mouth.

To make a modified 4520 go lower, one needs a longer horn and bigger mouth. For the mouth, there's no substitute to two side-side drivers like a 4520, but even taller. I am still working on it

Thanks for the link.

[Eaulive]

Give us some news, how do you like them?
How about those "wrong" 2225Hs?

[Lee in Montreal]

Here's a little follow-up to the 4520 thread. My fetish is with Yamaha power amps, especially the late 1970s P2200 serie, and mid 1980s PC2002 serie. 230wpc workhorse that were used to crank dancefloors as well as monitoring studios.

I already have 5 of them and while browsing Kijiji late at night, I found a decent set of PC2002 (230wpc) and PC1002 (100wpc) for the price of one core. Both came from an ice rink and were never rack mounted. I spent $200cad for the pair and 1 hour of my day dedusting them and removing stains from 30 years of exposure to nicotine. The only mark is remaining glue from the original installer sticker.

I have now two identical PC2002 and each one will power each 2225h in the 4520. I will use the PC1002 to power my pair of 2441.

[Eaulive]

Nice catch.

BTW, I will be ready for your yammies soon. I'm moving this weekend and my workshop will be up and running next week.


240W?
that's not enough for the 2225, I give them 450W out of two Crown XS700

I Like vintage speakers but recent amplifiers. Better technology, more silent, stable, powerful, light, small.
And they don't burn and take your valuable drivers with them. However I have to admit the XS series is one of the worst ever made by Crown. I have 6 of them, they were replaced by Crown in 2006 free of charge for the newer XTi series when those XS started to actup at a customer install in Punta-Cana.
They didn't even bother to claim them back.

I fixed them so they work, but they're not the most reliable thing, I wouldn't sell them to my ennemy

[reVintage]

This is what to expect in 1,0*Pi with a chamber volume of 80dm3.

[Lee in Montreal]

240W?
that's not enough for the 2225, I give them 450W out of two Crown XS700

Back in the days,the 4520s were powered by 150wpc Crown D300
I don't play them at a high volume anyway, and if I need more juice, the amps can be bridged to 700w. Basically all I'd need is to find another pair of PC2002s...