K-28 as K-22 replacement

[Daddy Dee]

OK. In a pair of mid-70's Heresy's I'm using K-28's as drop in replacements for the original K-22's. The sound is pleasant, with more robust bass.

Here's my question. The K22 is an 8 ohm driver and the K28 is a 4 ohm driver. I think I understand that the 4 ohm driver will play louder than the 8 ohm driver, which is why the K-33 is a 4 ohm speaker while the rest of Eminence drivers marketed to the public are 8 ohm drivers. Thus an 8 ohm driver would not be a satisfactory drop in replacement for a K-33.

In addition to the difference in output, the 4 ohm K28 would need a crossover change, right? In my very shallow understanding, the type E crossover rolls off the K22 at 700hz.

So a K-28 with an unmodified type E crossover would roll off around 400hz? correct?

i've got two questions, first have I got it right that the K28 is rolling off short 700hz? That would mean I've go a hole in my frequency coverage.

Second, what would need to be changed in the type E to make the K28 roll off a the correct frequency.

any help is sincerely appreciated.

[longdrive03]

Yo daddy dee. Sorry I missed the invite for barbeque!!

With a 4 ohm speaker you would halve the inductor value in a 6 db slope (just an inductor). Can recall the value on the xover for the woofer but cutting it in half should work with the four ohm. I think there is a network using the K-28 but not sure if it's same 700 hz xover frequency like the H's. I'll see if I can find some schematics for you.

[Islander]

I think there is a network using the K-28 but not sure if it's same 700 hz xover frequency like the H's.

The Heresy III uses the K-28-E woofer, crossing it over to the K-53-TI squawker at 850Hz.

[Daddy Dee]

Yo daddy dee. Sorry I missed the invite for barbeque!!

With a 4 ohm speaker you would halve the inductor value in a 6 db slope (just an inductor). Can recall the value on the xover for the woofer but cutting it in half should work with the four ohm. I think there is a network using the K-28 but not sure if it's same 700 hz xover frequency like the H's. I'll see if I can find some schematics for you.

Yeh. You can take a rain check.

Will give you a heads up next time we're heading over to Sim's

[Daddy Dee]

Gentlemen,

Thanks for you help here.

That is most interesting the the HIII crosses at 850hz.

Now I'm wondering if the Type E crossover actually crosses at 700hz.

[Tony Reed]

So if you use a K28 with a stock E crossover, do you have a "hole" in the frequency range? If so, how much of a "hole" are we talking about?

Thanks,

Tony

[colterphoto1]

if it'll go up to 850 it'll surely reach 700 safely.

I'd tend to plug it in and play it and see. Might be just the thing.

M

[BEC]

So if you use a K28 with a stock E crossover, do you have a "hole" in the frequency range? If so, how much of a "hole" are we talking about?

Thanks,

Tony

Tony,

I think you would have a hole in the response. I am going to guess that with a stock type E and a K-28 the crossover point would be about 400 hz. Then the midrange would come in at 700hz. That is partly based on a guess of what the impedance of the K-28 would measure in the Heresy cabinet. I haven't gotten around to measuring that yet. I have it on the list of things to do.

Bob Crites

[Daddy Dee]

if it'll go up to 850 it'll surely reach 700 safely. And if it's 4 ohms vs 8 ohms it's MORE bass.

I'd tend to plug it in and play it and see. Might be just the thing.

M

Well, the K28 does sound good in my seventies vintage Heresys and that's just drop in with no crossover changes.

What I'm wondering is whether there is merit to the idea of changing the crossover in these speaks to roll off at 850hz.

Wondering what the pros and cons would be.

I don't know what part of the music in in that range, say form 400hz to 850hz. Any sense of which driver would do better covering those frequencies? K28 or K55?.

I wonder if the type E crossover would get into any weird phase issues at 850hz. We know it works well rolling off the woofer at 700hz. Could just change the value of the inductor to do that and leave it alone.

Of course, we could do the really hard thing.... roll one off at 700 and the other at 850 and listen to see if a difference could be discerned.

[longdrive03]

Since the K-22 is an 8 ohm driver and the K-28 is a 4 ohm driver here is what I think would work in your situation. Use the K-28 and half the inductor value and double the cap value (assuming it is a 2 element 12db slope). I don't have the crossover schematic in front of me but doing this is very cheap. I can probably get the inductor and cap values of of the stock I have.

[longdrive03]

Ok, found the E schematic on the forum at

http://forums.klipsch.com/forums/p/89913/912168.aspx#912168

This shows a 2.5mh inductor only to the K-22 with a note of "11ohms"? I would think you could use a 1.25mh inductor with the 4 ohm K-28 and should get an xover point of around 700Hz so you don't have the 400-800Hz hole. I think I've got some of those 1.25 mh coils laying around.

[jerohm]

If my memory serves me, the Forte (K23-K/3mh/47uf) and the Forte II (K25-K/2.75mh/110uf) values for the low pass which both used 4 ohm drivers... the ~2.5mh is close enuff for government work.

[Trey Cannon]

Ok, found the E schematic on the forum at

http://forums.klipsch.com/forums/p/89913/912168.aspx#912168

This shows a 2.5mh inductor only to the K-22 with a note of "11ohms"? I would think you could use a 1.25mh inductor with the 4 ohm K-28 and should get an xover point of around 700Hz so you don't have the 400-800Hz hole. I think I've got some of those 1.25 mh coils laying around.

11 ohms is about the DCR of the mid.

The responce of the 28 is not the same as that of the 22 thus you may not have a hole at all. Even if you do have a hole, over 150 Hz of bandwidth, you may not even hear it. Now if there is a peek there, that could be a different story.

I don't have the TLS of either of these drivers, so I have no way to confirm anything. I do have a H3 network somewhere. If I can find it I will run a VT of it to see what the alinement is. That may help some.

I have heard the 28 droped in a H2. I thought it worked well.

[Daddy Dee]

Thanks all. This is most helpful.

[OO1]

I am doing a follow up on this thread in regards to K28 woofers in Heresy and Heresy II - Klipsch's own Trey Cannon had mentionned that the K28 also worked well in a Heresy II -

- after 2 years , can you please give us an update on how the k28 is behaving - thank you