And then came the CornScaltec...

[chops]

"Now to let the 902 run all the way out, all I have to do is take the

500uH inductor out of the chain, but what do I do about the CT125?

I

thought I read somewhere that either Dean or Al said that you can't

just remove the tweeter because the network will sense a change in

resistance from the tweeter not being there and squew the crossover

freq of the other drivers, or something like that.

Did I read

that right? If so, wouldn't I have to add a resistor of some value to

put across the tweeter output terminals on the networks?"

Hmm... Nothing yet on this?

I was also thinking, are the new 902s still made in either 8 or 16 ohms? If so, I could just get a pair of the 16 ohm versions and use them in my existing networks, right? I just still have to find out about the effects of removing the tweeter from the network.

[IB Slammin]

"Now to let the 902 run all the way out, all I have to do is take the 500uH inductor out of the chain, but what do I do about the CT125?

I thought I read somewhere that either Dean or Al said that you can't just remove the tweeter because the network will sense a change in resistance from the tweeter not being there and squew the crossover freq of the other drivers, or something like that.

Did I read that right? If so, wouldn't I have to add a resistor of some value to put across the tweeter output terminals on the networks?"

Hmm... Nothing yet on this?

I was also thinking, are the new 902s still made in either 8 or 16 ohms? If so, I could just get a pair of the 16 ohm versions and use them in my existing networks, right? I just still have to find out about the effects of removing the tweeter from the network.

If you buy from GPA, you will have your choice of 8ohm or 16ohm.

Terry

[Guest " "]

this gets messy depending on the crossover you have.

best bet is to get a good 2 way crossover.

you can mod your 3way, but there are a lot of issues and the values may not be the same as the parts you have.

most 2 ways are crossed over at higher frequencies than 400 hz in order to provide the right tonal balance. rarely below 1000, often a 2000 - 2500.

in a 3 way, depending on if it is a 2nd order or third order, the parts to by pass or pull are different depending on where you connect the 2 way tweeter.

if you decide to use the tweeter run...the shunt inductor in the tweeter circut would have to change, the capacitor in the tweeter circut would have to change, the in line and shunt parts in the mid range circut would have to be disconnected.

if you go with connecting the mid range and killing the tweeter run. all the tweeter circut componets wouldhave to be dis connected, in the midrange circut you willhave to remove the band pass filter, and any shunt capacitors , the vlaues of the inline capacitor would have to change.

it is messy to convert a three way to a two way...best bet is to put together a nes set of 2 ways.

[chops]

Okay, I need some ideas and/or info...

I am getting ready to buy a pair of Altec 902s from GPA in a couple of days, if not sooner! And depending on the price, I may end up getting a third one as well for the center channel.

Anyway....

My plan is that I would like to get these up and running ASAP. Since the K-55Vs are 16 ohm, I'm thinking I should just go ahead and buy the 16 ohm 902s, slap them into the CS II networks and let them fly as is for now. And in the meantime, I can do a little more research on building a nice little 2-way network to switch over to.

Now my questions are:

1) Couldn't I just disconnect the 500uH inductor from the squawker along with the 4uF cap of the tweeter and have a make-shift 2-way crossover?

2) If I were to do the above mentioned "mod", would that keep the crossover points in spec for the K-33 and 902 at around 400Hz for both and allow the 902 to run all the way out?

3) Or should I just leave the network as is and use the 902 as a pure midrange just like the K-55V is right now, then just switch over to the 2-way network once I get it built?

So whatch' think gang?

[Guest " "]

Okay, I need some ideas and/or info...

I am getting ready to buy a pair of Altec 902s from GPA in a couple of days, if not sooner! And depending on the price, I may end up getting a third one as well for the center channel.

Anyway....

My plan is that I would like to get these up and running ASAP. Since the K-55Vs are 16 ohm, I'm thinking I should just go ahead and buy the 16 ohm 902s, slap them into the CS II networks and let them fly as is for now. And in the meantime, I can do a little more research on building a nice little 2-way network to switch over to.

Now my questions are:

1) Couldn't I just disconnect the 500uH inductor from the squawker along with the 4uF cap of the tweeter and have a make-shift 2-way crossover?

2) If I were to do the above mentioned "mod", would that keep the crossover points in spec for the K-33 and 902 at around 400Hz for both and allow the 902 to run all the way out?

3) Or should I just leave the network as is and use the 902 as a pure midrange just like the K-55V is right now, then just switch over to the 2-way network once I get it built?

So whatch' think gang?

I was looking thru my altec library to see if I could send you a schmatic of an OEM Altec crossover network as a starting point...did not find any...but noticed while the driver can be used as low as 500hz, it is typically used in a 2way at 900hz.

I think the 900hz cut off has more to do with balancing out what octaves are covered by the horn loaded woofer and what octaves are covered by the HF horn.

I like the idea of keeping your present xovers and using the drivers in a 3-way config, and later move to a 2 way. this gives you a fall back plan. keep in mind that the driver is used in two way systems that usally have horn loaded woofers.....your cornscalas do not have horn loaded woofers.

looks like you are heading towards a voice of the theather design.

[D-MAN]

Hey, Chops!

I've found that once you get the performance capabilities to a certain point, it takes a broader selection of music to get an effective handle on the changes, that is, it takes a wider sample to get an effective "average". It may mean that your previously highly regarded choices go out the window to a degree.

Also when changing out mid/high freq units and horns, the difference in dispersion angles and various sensitivity changes with frequency will have a drastic effect on the listening space, requiring a new assessment of room treatments and placements, etc.

So the advice to take it slow and spend more time listening when making mods of this type is very good. There is some truth in the saying that it takes a bit of time for the ears to adjust to a new sound - I also recommend that you have some other experienced listeners to hear them too, they will not hear it exactly the same as you will, too. It is good to get a couple of second opinions from others to balance your opinion against. This is all subjective, but your ears are completely subjective anyway. Generally, if you think it might sound a little bright in certain areas, see if others pick that up too, etc.

I find that I eventually developed a set of cds to cover the whole gambit of sounds, from vocals with sibilance, to large-stage orchestral high volume, lotsa percussion stuff to give me an idea of the effects that mods may incur. Everyone relies on vocals to get a sense, but vocals are only about 1/2 of the spectrum.

Good work - keep it up.

Dana

[Al Klappenberger]

Chops,

I'm too blasted lazy to read through all the posts on this thread, but one thing jumps out at me from the pictures is the way you have the tweeter mounted. The only eason to mount it BEHIND the motor board is bedcause the magnet is to big to go through the hole. You have a slot. Why don't you move the tweeter so that it mounts from the front? That should improve the highs.

Al K.

[chops]

Chops,

I'm too blasted lazy to read through all the posts on this thread, but one thing jumps out at me from the pictures is the way you have the tweeter mounted. The only eason to mount it BEHIND the motor board is bedcause the magnet is to big to go through the hole. You have a slot. Why don't you move the tweeter so that it mounts from the front? That should improve the highs.

Al K.

Sorry Al. I should have been a little more clear on what I was asking. I was referring to the last post I made that started out as...

"Okay, I need some ideas and/or info...

I

am getting ready to buy a pair of Altec 902s from GPA in a couple of

days, if not sooner! And depending on the price, I may end up getting a

third one as well for the center channel."

And yes, I too have been too lazy to switch the tweeters over to front mount. Maybe I'll do that later tonight or something. We'll see. []

[chops]

Hey, Chops!

I've found that once you get the performance capabilities to a certain point, it takes a broader selection of music to get an effective handle on the changes, that is, it takes a wider sample to get an effective "average". It may mean that your previously highly regarded choices go out the window to a degree.

Also when changing out mid/high freq units and horns, the difference in dispersion angles and various sensitivity changes with frequency will have a drastic effect on the listening space, requiring a new assessment of room treatments and placements, etc.

So the advice to take it slow and spend more time listening when making mods of this type is very good. There is some truth in the saying that it takes a bit of time for the ears to adjust to a new sound - I also recommend that you have some other experienced listeners to hear them too, they will not hear it exactly the same as you will, too. It is good to get a couple of second opinions from others to balance your opinion against. This is all subjective, but your ears are completely subjective anyway. Generally, if you think it might sound a little bright in certain areas, see if others pick that up too, etc.

I find that I eventually developed a set of cds to cover the whole gambit of sounds, from vocals with sibilance, to large-stage orchestral high volume, lotsa percussion stuff to give me an idea of the effects that mods may incur. Everyone relies on vocals to get a sense, but vocals are only about 1/2 of the spectrum.

Good work - keep it up.

Dana

Dana,

I realize that it does take time to listen to and hear the changes. However, I should let you know that almost litereally every minute that I'm awake and home, the stereo is on, and I'm sitting right in front of it all the time. I put a lot of hours on my system and listening time. It's a good thing I don't have tube equipment anymore, or I'd be having to buy new tubes every couple of months! LOL

Also, I listen to a large selection of music every day; from Metalica to Mozart, Norah Jones to Jimmy Buffett, JS Bach's BWV 565 to Front Line Assembly, Kenny G to Cesar Franck. You name it, I listen to it, except for rap, r&b, reggae, country, elevator, bluegrass and a few others.

There's a lot to be said for having a laptop with wireless internet always in the music room. [8-|]

[mowntnbkr]

Do you have to have an adapter to get the k-55's on the 511's or did they mate up well? Also did you have to modify the crossovers or are Deans type B's okay?

[D-MAN]

Howdy Sam! Thinkin' of upgrading the CW's?

Dana

[cjgeraci]

"3) Or should I just leave the network as is and use the 902 as a pure midrange just like the K-55V is right now, then just switch over to the 2-way network once I get it built?"

This is the option I would go with first. Having heard commercial VOTTs and having owned two-way Altec Valencias and then converting them to three-ways (with Beymas on top), I appreciate the Altec horns even more when they are not trying to accomplish the entire upper half. Admittedly, the 902s w/511s should sound pretty good as two-ways, but I also agree that it may not be as easy as simply converting your existing network to get there. Therefore, you probably will end up with a two-way design (or going to an active two-way). Why not stop at the in-between step first and substitute the 902s as a squawker first? Then, if you are not where you want to be - continue on.

There is also another thought worth considering. You appear to be making the choice to go with 902s due to some dissatisfaction with your K-55s at certain volume levels and/or with certain songs. My guess may be that even a change to 902s may not solve that particular situation with respect to your 511s. I only say that because in my experience, K-55s can be very effective (Trachorns!), at all volumes, with a variety of sources - and in my experience, if you are running tubes on the front end. And also even nice Altec drivers can sound less than stellar under some circumstances.

Then again, I could be wrong.......

Carl.

[IB Slammin]

"3) Or should I just leave the network as is and use the 902 as a pure midrange just like the K-55V is right now, then just switch over to the 2-way network once I get it built?"

This is the option I would go with first. Having heard commercial VOTTs and having owned two-way Altec Valencias and then converting them to three-ways (with Beymas on top), I appreciate the Altec horns even more when they are not trying to accomplish the entire upper half. Admittedly, the 902s w/511s should sound pretty good as two-ways, but I also agree that it may not be as easy as simply converting your existing network to get there. Therefore, you probably will end up with a two-way design (or going to an active two-way). Why not stop at the in-between step first and substitute the 902s as a squawker first? Then, if you are not where you want to be - continue on.

Carl.

Carl, I couldn't agree more.

Terry

[mowntnbkr]

Howdy Sam! Thinkin' of upgrading the CW's?

Dana

Hey Dana,

Yeah, I am thinking about it, but first I have to get a set of vrd's and a BB extreme, both will be ordered tomorrow..............once that is done, then I am going to do the same to the cw's. SWMBO reqires them to be a little more asthetically pleasing though so I will need to design something to house them in. Somebody on this forum said something about a "slippery slope"...........I never realized just how slippery []

[Al Klappenberger]

Chops,

If I were going to use an Altec 902 on a 511 horn (actually, I would use the 811 horn) I would raise the crossover to between 500 and 800 Hz. The 902 is best when run higher. With a simple crossover you will be letting a lit of dangerous lows through to the driver. In a Cornwall type of system it will be attenuated quite a bit, so it should be safe though.

AL K.

[sfogg]

"3) Or should I just leave the network as is and use the 902 as a pure midrange just like the K-55V is right now, then just switch over to the 2-way network once I get it built?"

What crossover are you running now? If it isn't a bandpass for the squawker it isn't going to work well with the Altec since the Altec is not at all going to be rolling off at 6kHz like the K55.

One additional suggestion... if you are going to be coming up with new crossovers for the 902s don't feel compelled to keep the stock crossover points. The stock crossover points were fairly forced by the choice of squawker/tweeter... no reason to keep that with better drivers.

If you keep it a three way the 902 will go well beyond 6kHz, I'd cross it higher... in the 8-10kHz range and use the tweeter for the last octave.

Shawn

[chops]

Chops,

If I were going to use an Altec 902 on a 511 horn (actually, I would use the 811 horn) I would raise the crossover to between 500 and 800 Hz. The 902 is best when run higher. With a simple crossover you will be letting a lit of dangerous lows through to the driver. In a Cornwall type of system it will be attenuated quite a bit, so it should be safe though.

AL K.

Al,

My concern is with the 1979 K-33E at higher freqencies. How high and cleanly can it play? Should I try running both the K-33 and 902 at the Cornwall's stock 600Hz points? Is there a way I could get the squawker to cross over at say -12dB or -18dB instead of the normal -6dB?

Thanks,

Charles

[chops]

"3) Or should I just leave the network as is and use the 902 as a pure midrange just like the K-55V is right now, then just switch over to the 2-way network once I get it built?" What crossover are you running now? If it isn't a bandpass for the squawker it isn't going to work well with the Altec since the Altec is not at all going to be rolling off at 6kHz like the K55. One additional suggestion... if you are going to be coming up with new crossovers for the 902s don't feel compelled to keep the stock crossover points. The stock crossover points were fairly forced by the choice of squawker/tweeter... no reason to keep that with better drivers. If you keep it a three way the 902 will go well beyond 6kHz, I'd cross it higher... in the 8-10kHz range and use the tweeter for the last octave. Shawn

I'm using modded Type B networks, now considered Type CS II networks...

Woofer crossed over @ 437Hz via 68uF cap

Squawker crossed over @ 400Hz via 500uH inductor

Squawker crossed over @ 4500Hz via 7uF cap (4uF + 3uF)

Tweeter crossed over @ 4500Hz via 4uF cap (2uF + 2uF)

[Deang]

Woofer crossed over @ 437Hz via 68uF cap

Woofer begins rolling off at 12dB/octave at this point. It's based on 4 ohms, and conforms to a Butterworth alignment.

Squawker crossed over @ 400Hz via 500uH inductor
Squawker crossed over @ 4500Hz via 7uF cap (4uF + 3uF)

You have these backwards. The 7uF bank is your high pass. It allows everything above 400Hz to "pass" (blocks lows). Actually, 7uF is closer to 350Hz. The rate of attenuation is 6dB/octave.

The .500uH (or .50mH) is a low pass for the squawker. At 4500Hz, it begins to roll off the squawker's output. Again, the rate of attenuation is 6dB/octave.

The 7uF and .500uH together form a first order bandpass.

[chops]

Squawker crossed over @ 400Hz via 500uH inductor

Squawker crossed over @ 4500Hz via 7uF cap (4uF + 3uF)

You have these backwards.

Oh yeah... oops! [:$]

Thanks Dean. []