ICTA update

[johnk]

Provided Link: ICTA (http://www.musicanddesign.com/icta.html)


I've added a section on the midrange/tweeter crossosver. This completes the basic design concept. Now to start building.

<A HREF="http://www.musicanddesign.com/icta.html">http://www.musicanddesign.com/icta.html</A>

[djarchow]

> I've added a section on the midrange/tweeter
> crossosver. This completes the basic design
> concept. Now to start building.

> <A HREF="http://www.musicanddesign.com/icta.html">http://www.musicanddesign.com/icta.html</A>

John,

This looks good. Glad to see some progress. I like that you managed to get a third order rolloff on the mid, this should increase the selection of suitable drivers vs the 1st order rolloff required for the filler driver approach.

What was your reason for going with a lower range of 1.5 kHz for the XO frequency. Even with the third order slopes, this will still stress tweeters with a lot of excursion like the Millennium. Seems like moving the XO point up to 2.5 kHz would stress the tweeter less as well as open up the selection of suitable tweeters a bit.

Have you come up with a new spreadsheet for calculating the target slopes like you did you with the filler driver approach?

Finally, I assume that you will need to do some offsetting of drivers to match your phase targets. Will you be going the route of the TP 3 way with an angled baffle to get the offsets or will you use a stepped baffle this time?

Kind regards,

Dennis

[johnk]

> John,

> This looks good. Glad to see some progress.
> I like that you managed to get a third order
> rolloff on the mid, this should increase the
> selection of suitable drivers vs the 1st
> order rolloff required for the filler driver
> approach.

> What was your reason for going with a lower
> range of 1.5 kHz for the XO frequency. Even
> with the third order slopes, this will still
> stress tweeters with a lot of excursion like
> the Millennium. Seems like moving the XO
> point up to 2.5 kHz would stress the tweeter
> less as well as open up the selection of
> suitable tweeters a bit.

> Have you come up with a new spreadsheet for
> calculating the target slopes like you did
> you with the filler driver approach?

> Finally, I assume that you will need to do
> some offsetting of drivers to match your
> phase targets. Will you be going the route
> of the TP 3 way with an angled baffle to get
> the offsets or will you use a stepped baffle
> this time?

> Kind regards,

> Dennis

The mid/twe x-o point is still undecided. It will be somewhere between 1.5 and 2k. I'm using the 8554 for the mids so 2k might be a little bit of a push. Tweeter is still undecided.

[johnk]

> John,

> Have you come up with a new spreadsheet for
> calculating the target slopes like you did
> you with the filler driver approach?

> Finally, I assume that you will need to do
> some offsetting of drivers to match your
> phase targets. Will you be going the route
> of the TP 3 way with an angled baffle to get
> the offsets or will you use a stepped baffle
> this time?

> Kind regards,

> Dennis
Forgot a couple of questions.

1) No I won't be coming up with spread sheet. The reason being that the additional Bessel LP applied to the mid is specifically dependent on the midrange driver used. The final LP target for the mid is a combination of the 1st order Lp part from the subtractive part plus the Bessel LP set to match the driver natural roll off +/_ a little. Thus the Bessel LP part could be any order and/or corner frequency but at least 1/2 to an octave above the x-o point. I could write a spread sheet but it's not that hard to do with any existing CAD code.

2) Well, offset will be required. We'll see if I go with an angled baffle or something else. But the system will be all analog, definitely active between woofer and mid. There may be a passive x-o between mid and tweeter, but I may go active there as well. Depends on the tweeter. I have a couple of different ideas there.

[djarchow]

But the system will be all analog,
> definitely active between woofer and mid.
> There may be a passive x-o between mid and
> tweeter, but I may go active there as well.
> Depends on the tweeter. I have a couple of
> different ideas there.

John,

Thanks. I guess I had missed the part on your write-up on this being fully active. I knew that the subtractive delay approach usually implied active but somehow when I read "analog filters" my brain translated that into "passive filters. Could you do this as fully passive?

You really need to release a complete TP design which can be done with passive XOs and moderately priced drivers so that more DIYers can experience transient accuracy.

Good luck with the project. Looking forward to more updates. It is always nice to see someone doing something other than another LR4 two way.

Regards,

Dennis

[johnk]

> But the system will be all analog,

> John,

> Thanks. I guess I had missed the part on
> your write-up on this being fully active. I
> knew that the subtractive delay approach
> usually implied active but somehow when I
> read "analog filters" my brain
> translated that into "passive filters.
> Could you do this as fully passive?

> You really need to release a complete TP
> design which can be done with passive XOs
> and moderately priced drivers so that more
> DIYers can experience transient accuracy.

> Good luck with the project. Looking forward
> to more updates. It is always nice to see
> someone doing something other than another
> LR4 two way.

> Regards,

> Dennis

The simple answer is that all the filters in the proposed ICTA are minimum phase and could be implimented passively. The tweeter delay come after the filter as opposed to before it (as in a subtracted-delayed development). However, it makes more sense to impliment the woofer/mid x-o actively. The mid/twe x-o is looking like it can be done either way. But in any case, it's all analog with the exception of the tweeter offset, which coule be replaced by a pure time delay (digital0 in an all active, hybrid, analog/digital system.

[ajinfla]

Fully active? Digital?! My god John, you have succumbed to the Dark Side.

cheers

AJ

[johnk]

> Fully active? Digital?! My god John, you
> have succumbed to the Dark Side.

> cheers

> AJ

Not just yet. :-) I'll use digital in the development stage but the goal is still an analog, active/passive hybrid. I'll only resort to fully active if absolutely necessary.

[JRT]

> I've added a section on the midrange/tweeter
> crossosver. This completes the basic design
> concept. Now to start building.

> <A HREF="http://www.musicanddesign.com/icta.html">http://www.musicanddesign.com/icta.html</A>

Thanks for posting that. I am looking forward to reading the updates, and hopefully someday hearing the results.

[JRT]

Provided Link: ICTA (http://www.musicanddesign.com/icta.html)


I've added a section on the midrange/tweeter crossosver. This completes the basic design concept. Now to start building.

<A HREF="http://www.musicanddesign.com/icta.html">http://www.musicanddesign.com/icta.html</A>

JPK's webpages of ICTA info (designing for impule correct, transient accurate response) has been pulled?

:(



.

[dlr]

JPK's webpages of ICTA info (designing for impule correct, transient accurate response) has been pulled?
His main page has the line for it at the top of his Discussions list, but it's not a link, either. Looks like John just needs to do an update.

Here's hoping that we'll have at two of John's systems at DIY NE this year, the NOTE (again) and the ICTA.

dlr

[JRT]

His main page has the line for it at the top of his Discussions list, but it's not a link, either. Looks like John just needs to do an update.

Here's hoping that we'll have at two of John's systems at DIY NE this year, the NOTE (again) and the ICTA.

dlr

http://techtalk.parts-express.com/images/icons/icon14.gif

I too would like to hear those.




.

[johnk...]

His main page has the line for it at the top of his Discussions list, but it's not a link, either. Looks like John just needs to do an update.

Here's hoping that we'll have at two of John's systems at DIY NE this year, the NOTE (again) and the ICTA.

dlr

I retired the IctA concept. With the UE there is little point in pursing it. The UE can make any speaker ICTA. The only advantage of the ICTA concept was that it was done with minimum phase filters.

Oh, and just for completeness, I finished testing the miniDSP with the NaO Note. Works great. Dead quiet, very dynamic. I don't know what all the fuss is a bout loosing bits because of the required eq. I understand the argument but it doesn't seem to hold up. Maybe those opamps in the active circuits are worse that the loss of a few bits with a dsp x-o. ;) I will definitely be offering the Note with miniDSP setting as an alternative to the active analog crossover.

And the Note seems to be gaining popularity. There are systems being build in Sweden, Denmark, the UK, the USA, Australia and Indonesia. When are one of you PE guys going to take a shot?

[dlr]

I retired the IctA concept. With the UE there is little point in pursing it. The UE can make any speaker ICTA. The only advantage of the ICTA concept was that it was done with minimum phase filters.
Ah, I hadn't noticed the date of the original post and thread. Had me wondering why you'd have mentioned it again. Guess you hadn't.


Oh, and just for completeness, I finished testing the miniDSP with the NaO Note. Works great. Dead quiet, very dynamic. I don't know what all the fuss is a bout loosing bits because of the required eq. I understand the argument but it doesn't seem to hold up. Maybe those opamps in the active circuits are worse that the loss of a few bits with a dsp x-o. ;) I will definitely be offering the Note with miniDSP setting as an alternative to the active analog crossover.
We'll all be looking forward to DIY NE this year. I'm looking forward to a side-by-side with my quasi-dipole. This year I'm going to try to get more listening time. :) I hope to have a second one built during the summer that will be a full dipole. That likely won't be using any currently available drivers, however, except for the tweeter. The UE makes it so much easier.

dlr

[johnk...]

Ah, I hadn't noticed the date of the original post and thread. Had me wondering why you'd have mentioned it again. Guess you hadn't.


We'll all be looking forward to DIY NE this year. I'm looking forward to a side-by-side with my quasi-dipole. This year I'm going to try to get more listening time. :) I hope to have a second one built during the summer that will be a full dipole. That likely won't be using any currently available drivers, however, except for the tweeter. The UE makes it so much easier.

dlr

I'm working on something that will be minidsp based (or UE based). It willl be my least expensive doiple design but will have a performance level in the same league as the NaO II and Note.

[dlr]

I'm working on something that will be minidsp based (or UE based). It willl be my least expensive doiple design but will have a performance level in the same league as the NaO II and Note.
So you're going to have the Note and the new one at DIY NE, right???? :D

Other than playing around with some woofers and midwoofers because I have so many on the shelf and to match something to the several M/T box setups I have, I can't see ever building a box again. Except possibly a subwoofer box.

dlr