JBL 2470 - are they superior to the K 55?

[Deang]

"It is a shame the K Horn bass bin does not go up a few hundred more HZ. The options for midrange driver would vastly improve."

LOL, someone famous once thought the same thing.

EQ might save the project.

[djk]

Your overlap does not indicate how they will actually sum.

If they sum in phase there will be a 6dB increase at the crossover point.

The Q of the crossover design will also affect the summed response, see the PWK LB-76 patent.

[Deang]

Brilliant, I completely forgot about that -- thanks Dennis.

[awsjr]

hi Tom......I have not tried the k55m on my 511b horns......maybe I

will this weekend as I have some threaded adapters from parts

express.....I went from the 808s to the 902s and then to the

2470s...the 2470s seem to have greater detail throughout the entire mid

range......with the 808s and 902s I used the 0 - 4 taps as they

are 8ohm drivers....with the 2470s the settings are 2 - 5......I am

also using some of AL Ks tweeter attentuators with my 2404s and the

setting is 3....don't get me wrong though because the altec drivers

were both really nice too.....the effort was minimal.....I used the

parts express aadpters as a template to drill the 3-hole pattern in the

511b's needed for the 2470's.....it took less then an hour to have them

both hooked up.....as far as cost, I paid ~$220 for the

2470's......they have the original phenolic diaphragms and eventually I

may get some aluminum ones -Al

[Al Klappenberger]

Guys,

The choice of crossover may help the transition between the Khorn woofer and
the JBL 2470 driver. Using my Universal network woofer / squawker section
would NOT be a good choice here. It's N=1. Look at the text book curves for
Butterworth filters below. Compare the losses at .8 times the cutoff
frequency between the N=1 and N=2 curves. The n=2 network lets more of the
energy get through to the driver on both sides of the crossover. This might
help the sag a bit but I'm not sure. The N=2 network sums up to 3 dB higher
than the N=1 network. This certainly will help! The N=1 and N=3 sums flat.
BTW: My ES400 extreme-slope network also sums flat. I designed a boost into
it at the crossover but it can only compensate for the losses in the large
inductors required at 400 Hz.

Al K.

[Tom Mobley]

Dean,

you have these 2470 in your hands? why not bolt them on and give a

listen? we have a report just up above that claims they're wonderful.

we know that published specs often don't reflect reality real well.

{edit} sorry, wrote this up hours earlier, never posted it.

[Deang]

"Why not bolt them on and give a listen?"

Because I don't have a network for them. I wish it were as simple as just tossing them into the mix, but I don't have what it takes to run them right.

Dennis -- my drivers are non-coincident, I think that means the most I can get at the crossover point is 3dB.

[djk]

"Dennis -- my drivers are non-coincident, I think that means the most I can get at the crossover point is 3dB. "

A very real problem. On a Cornwall type speaker, adding an all-pass delay network to the woofer really improves the sound in the midrange. Too bad we can't do that with the Klipschorn(without using a digital delay).

[Deang]

I can maybe get away with a 500/5000 even order all-pass that gives me 2.08dB of gain in the bandpass. Looks like it's 12dB/octave or bust.

[Deang]

Well, I loaded them up all nice pretty and gave them a spin. I figure a driver designed to handle 50-60 watts oughta be able to handle a bit of abuse from a low watt Tripath amp and a first order filter. There's definitely a touch of loss in the 400Hz area but it doesn't sound near as dramatic as the plot indicated it might. They sound very, very good -- so I'm going to leave them in and try a few things. I'm not getting any indications that the driver is unhappy with what I'm doing, but anyone trying these might want to be careful with their power levels.

[Al Klappenberger]

Dean,

I don't think you could do an damage to thos 2470s even if you tried to. Remember that you also have them attenuated with a transformer by about 6 dB. That means you are only putting 1/4 the power into them that is going to the woofer. The only question is the 400 Hz crossovoer reigon frequency response.

AL K.

[sunnysal]

Too bad we can't do that with the Klipschorn(without using a digital delay

And what is wrong with digital delay? I say go all the way with the k horn, triamp, delay the woofer and mid a bit and crossover all with an electronic unit. even EQ the sucker a bit. I think we are bucking the inevitable, digital is coming, get on board!

tony

[Deang]

Too bad we can't do that with the Klipschorn(without using a digital delay

And what is wrong with digital delay? I say go all the way with the k horn, triamp, delay the woofer and mid a bit and crossover all with an electronic unit. even EQ the sucker a bit. I think we are bucking the inevitable, digital is coming, get on board!

tony

Are you in the right thread Tony?

I think that woofer is already delayed about as much as we can stand, but I catch your meaning here. Roy Delgado thinks delay for the top is important, so naturally I'm curious to hear it for myself someday. The purist in me struggles with whole concept, and my wallet doesn't like it either! I think what I will do for now is simply enjoy my Klipschorns -- which are sounding might fine these days. Maybe in a few years I will have the means to buy the Jubilee bottoms, and I think that's when I'll explore active filters and time delay.

[ZAKO]

I tried the delay on the top units.... I couldnt tell the difference.. Nor could PWK.

[djk]

"And what is wrong with digital delay? I say go all the way with the k horn, triamp, delay the woofer and mid a bit and crossover all with an electronic unit. even EQ the sucker a bit. I think we are bucking the inevitable, digital is coming, get on board!"

I'm all for it, and have been advocating this for years. I own two of the EV type DSP based crossovers (Motorola 56007) that Klipsch used in their Jubillee demonstration. Unfortunately the cost $1.5K new, and you needed two! Not to mention more amps, test equipment, etc.

Also it should be mentioned that they verge on being un-listenable in stock form, cheap electrolytics and opamps in the signal part. The Berry is the same, but at a better price point (now un-available due to a parts issue).

The thrust of my remarks were: a Cornwall can fix the time delay problem in the midrange with the addition of a simple passive filter, the Klipschorn cannot.

[djk]

"I tried the delay on the top units.... I couldnt tell the difference.. Nor could PWK. "

Unfortunately I can.

Fortunately I know of the cure, and have the will to fix it.

[tigerwoodKhorns]

I am using a digital crossover (a Yamaha D2040 reccomended by Griffinator). Have not hooked it up yet.

I have read about protecting my tweeters from amplifier DC at startup (the solid state "thump" that is usually protected by the passive crossover). I want to use a large solen capacitor bypassed by a small Kimber or auricap. I need to have the cap filter at least 1.5 to 2 octaves below the actual crossover point. So not I have two questions:

1) What is the equation for determining the filtering frequency of the capacitor (8 ohm load)? (I will cross over somewhere between 3000 hz to 6000 hz - Don't know until I hook everything up).

2) Can someone give me teh breakdown of the 8 octaves that we hear (what frequency point)?

3) OK I added one. I read to use a 20 uF cap bypassed with a 1 uF cap will give me a 6 db slope at about 1000 hz. Is this sufficientlt below the 3000 hz above (1.5 to 2 octaves below - I doubt it).

Thanks,

Chris

[sfogg]

"I have read about protecting my tweeters from amplifier DC at startup

(the solid state "thump" that is usually protected by the passive

crossover). I want to use a large solen capacitor bypassed by a small

Kimber or auricap. I need to have the cap filter at least 1.5 to 2

octaves below the actual crossover point. So not I have two questions:"

If you are using the Teac's you don't really need to bother. Because of

the relay based muting in the Teac's they don't have any turn on/off DC

so no problem running it straight to the drivers.

Make sure the crossover doesn't do anything nasty at turn on/off as well.

Shawn

[tigerwoodKhorns]

I think that if I don't add the protection I will always be wondering and worrying about them. However, the tweeters are pretty rugged (JBL 2404's).

What crossover frfequency does the DC thump occurr at? (I have a fewe rather large caps lying around from my old AK networks (like 80 uf each). If these will work, all I will need is a small bypass cap (Like a 1 uf or maybe a 0.5 uf - can I use the smaller one to save money).

Chris

[sfogg]

"What crossover frfequency does the DC thump occurr at? "

It doesn't occur in the Teac's. Not all amps have it, just some do. You

don't need to worry about it with the Teac's. I'm running the same

tweeter with the Teac and there is no problem at all.

As far as frequency it occurs at DC..... 0 hz.

Shawn