Active Crossovers

[Rudy81]

Rod: Definately give it a shot. Too bad you don't live near me, or you would be most welcome to come have a listen....althought I'm not done tweaking.

Give careful consideration to how you are going to connect the DCX to the amps so you don't fry something. I don't know how likely that is, but based on my conversation with Parasound, they emphatically suggest you don't connect the DCX to a consumer amp. I tried the Samson s-convert, and it does the job just fine, but I found it to be too noisy and sent it back.

You might give some thought to how you are going to set the four available channels up. The bass bin will create the longest delay, but when you actually go to make the changes in the DCX, you delay the mid and tweeter. The woofer stays at time of zero. So, I might suggest the bass bin in one channel and see if you can put the mid and tweeter in the other channel. ( You will have to figure out how to make that work with your passive crossover). This way, you can delay the mid and hi channel to roughly match the woofer. Then, the only thing out of time will be the tweeter and that is not much.

Otherwise, use all six channels and leave the sub out temporarily while you play with the active crossover.

Although not done, here is a shot of my gear on a new rack.

[Rudy81]

And a wide shot of the entire electronic stand.

[Rudy81]

Rod, one more thing I forgot to mention. You will most certainly find a high noise floor to become an issue until you can get amps that have adjustable sensitivity.

I was able to find very reasonbly priced gear on eBay and from other forum members. I had a few duds that were returned, like the Crown multi-channel amp and the Crown D-75. I now always look for the ability to return an item before I bid on it.

[Rudy81]

BTW, here is a question for you EEs that may be familiar with Furman products. I obtained an older Furman PS-8R power sequencer which has a three screw terminal strip on the back for a 12 volt trigger. My Integra has +12V triggers, but I can't get trigger to work properly on the Furman. It only works 'reversed' from what one would want. When the integra sends the signal, the Furman shuts off. When the Integra shuts down, the Furman comes on.

I called furman tech support and they indicated this behaviour had to do with the way the trigger was designed on the furman. He indicated it might be made to work by adding a resistor to the terminal strip, but did not want to further into the problem. Has anyone run into how to solve this?

[Rudy81]

Made some final changes tonight and think I'm very close to where I want the Khorns. I followed DrWho's advice and played with the polarity of the woofer to see if it matched the mid better at the crossover point. BINGO. After reversing the woofer polarity I got a nice flat line across the crossover area vs. a dip where the drivers meet. Nice call DrWho!

I also matched the subwoofer polarity to that of the woofers. This REW program is so nice and so flexible.

As it stands right now, I am thrilled with the sound of the Khorns. The dynamics, imaging, soundstage and precision of the instruments is better than I ever recall hearing in my room. Same drivers, different crossover. Theoretically, these pro amps should not be as good as my Parasound HALO amps, but I don't hear that difference and my HALO A23 amp is not even hooked up any more.

I still find I prefer that Butterworth setup I mentioned before vs. a straight LR 24dB slope crossover. The soundstage achieved with the calculations from the aforementioned spreadsheet is better than anything I have tried.

I can honestly say that the hassles, headaches and expense have been well worth it. I'm glad I took the journey and LOVE the way the Khorns sound. Thanks again for all the help guys. Could not have done it without your assistance. Cheers.

[DrWho]

Made some final changes tonight and think I'm very close to where I want the Khorns. I followed DrWho's advice and played with the polarity of the woofer to see if it matched the mid better at the crossover point. BINGO. After reversing the woofer polarity I got a nice flat line across the crossover area vs. a dip where the drivers meet. Nice call DrWho!

It's a bummer REW isn't a bit better in the absolute polarity department as this is quite easy to measure with different tools (although they cost quite a bit more). Just one quick question though....do you see two smaller ripples to the left and right of the dip that you were originally seeing when you invert the woofer polarity? If so, then you were probably 180 degrees out of time alignment instead of the polarity being the problem...

I'm very glad to hear that you're enjoying the system now. I truly believe that active xovers are the future of the home audio industry (it's already the staple of pro sound), but it's so frustrating when you consider just how many hoops one needs to jump through to even get things sounding halfway decent. The market is really hurting for a plug and play solution, but it would require a lot of support from all the speaker companies to provide all the necessary settings. One of the great things about the Klipsch Jubilee is that Roy has gone the extra mile to do all of the measuring and tweaking ahead of time....so it simply becomes an issue of getting the settings into the crossover correctly, and then of course dealing with all the unnecessary consumer/pro interfacing conundrums. I think what the home audio industry truly needs is a single generic file format to be provided by the speaker companies, that can be loaded into any DSP unit, and then of course there needs to be consumer level inputs/outputs so that there aren't any interfacing issues.

The thing that really kills me is that I've already designed just such a unit, but I don't have the time/money to actually turn it into a viable product. Proof of performance on the bench is only like 10% of the total work. []

[Rudy81]

DrWho, I'll put up a copy of the new readings when I get a minute. I'd like to delve a little more into the issue of 180 time alignment. Don't quite understand that vs. the polarity issue.

As far as going mainstream, It would be a tall order for manufacturers to get together and make an easy to use system for general consumption. However, a mid level market might take to it pretty quick. The dbx driverack + has the capability to handle both pro and consumer outputs with the change of a button. My hafler amps also have a switch to handle both types of inputs. So, it is starting to catch on, but not in a big way.

With the current availability of DSP chips, I would think it would be rather simple to automate the entire process using a mic input with phantom power via one of the crossover inputs, much like the DCX 2496 can do to calibrate time and EQ settings. Just that little extra step missing. For me, the fun was in learning how to do it and getting to understand the concepts.

BTW, I have noticed a sizeable dip in the tweeter measurements right around the 10kHz range. It happens no matter what IR window I use, how close or far I place the mic and is the same for the righr or left speaker. All I can think of is that the mic has some measuring aberration or my tweeter response drops off at about 10kHz and then picks up again. Very strange.

[Rudy81]

I think I found the source of the 10kHz dip. Looks like it may be part of the driver's native response. http://www.madisound.com/catalog/PDF/apt150.pdf

[DrWho]

Ya, I was meaning to get back to you on this, but I'm fairly certain that dip is inherent to the design of the APT-50 driver (I think that's the driver number...I'm going off memory here).

[Rudy81]

Yes, that is the driver number....good memory. Based on the published FR graph for the driver, there is a dip similar to what I am reading. At least I know there is nothing wrong with my gear or my mic.

[Rudy81]

New discovery tonight. Decided to try something that has been bugging me since I installed the Trachorns. I hated having to move the tweeters and mid horns to the sides of the top hat. It just isn't symetrical in my mind. I pulled the top hat apart since I was making the active setup permenent and removing the ALK's, centered the Trachorns in the top hat and placed the APT-150 horn on top of the speaker angled slightly down to compensate for the vertical displacement.

Played some Boston and found the tweeters were now sounding overboosted. I guess the top hat fabric attenuates the sound somewhat. I would guess the higher frequencies are more susceptible to being attenuated than lower ones. What a difference. I know it doesn't look as 'clean' as it does with both drivers inside the top hat, but who cares. The tweeters have 'come to life'.

This just keeps getting better.

[Rudy81]

Finally had a chance to do some final tweaking of the active filter. I worked quite a bit on the woofer to mid transition and this is the best I could do. Not too bad from what it was before. I also did some EQ work on the woofer hump, the tweeter drop at 10kHz and the transition from the woofer to the mid. Last week I also moved the mid horn to the center of the top hat and placed the tweeter on top of the speaker. Figured it can't hurt to line up all the drivers vertically and avoid the side angles created by having the tweeter and mid horns side by side. Overall, the system sounds really nice. I still can't get over the huge positive effect of having the amp totally controlling the drivers. This is particlulary noticeable in the woofers. Imaging and soundstage are better than ever. The soundstage is a great improvement, although I thought it was nice before. This has been so well worth it. My ALK universals are now unemployed and close to going on the auction block. Ok, what's next?

[Rudy81]

All this just for the Khorns....but it works amazingly well.

[Rudy81]

The new Khorn look with a naked tweeter....but it sounds sweet. I wish the crossover between the bass bin and the mid was a little 'fuller'. Unfortunately, the woofer runs out of steam just as the mid range is beginning to pickup. No real overlap in FR between these two drivers (JBL 2470 and bass bin). Now if Al can come up with a good 2" combination that will work with the Khorn...or perhaps time to build a Jub clone bass bin.....hmmmmmm.

[Pete H]

FYI, I will blame you, as well as all of the others that are involved in this thread for causing me to spend a few more thousand dollars, chasing the perfect sound. I will be ordering an active crossover, prior to going to sleep tonight, and I just wanted to say Thanks!

[Rudy81]

FYI, I will blame you, as well as all of the others that are involved in this thread for causing me to spend a few more thousand dollars, chasing the perfect sound. I will be ordering an active crossover, prior to going to sleep tonight, and I just wanted to say Thanks!

That's exactly how I feel. Although, I was able to get reasonably priced (used) amps and a great deal on a crossover from JC. I can't tell you how glad I am that I got into this. I still have a lot to learn, but it has been instructive and when not tearing my hair out....fun.

The results have made it all worthwhile. I have zero regrets on this project. I should be able to recoup some cash when I sell the ALK universals and might even sell my Parasound HALO A23....

The advantages greatly outweigh any downside. Now, if Al comes out with a new driver/horn combination, I just adjust the crossover parameter and I'm off to the races....couldn't always do that with the universal.

BTW, what crossover are you getting?

[Rudy81]

It's official. The ALK's are for sale and I'm now fully in the dark side. Thanks for letting me play and helping out. [8-|]

[DrWho]

DP

[DrWho]

Ok, what's next?

Well since you asked... [6]

I would start off by listening to some music []

If
you're looking to upgrade your speakers later on, then I would highly
recommend striving for a flat power response with a flat on-axis
response, which will put you in the realm of CD horns. You might also
considering going 2-way at the same time, so the sale of an amp might
help to make that a cheaper investment. Of course that recommendation
would include moving towards the Jubilee, but the irony there is you
wouldn't need to do your own measuring to dial it in [A]

I'm glad you think it's an improvement. For a while there I thought you were just gonna give up.

[Rudy81]

DrWho, I have been listening and I really like what I am hearing. Very different sound than the passive crossovers. I am thrilled. I thought about giving up, but that is not something I normally do. Problems just focus my intensity on how to overcome issues and move forward.

Funny you mention the Jubilee. This whole thing started because I was contemplating building some Jub clone bass bins to better be able to match the mids and cross them over higher. I then found out I would have to modify the ALK's as a minimum to be able to do that. Someday I would like to put some Jub bass bins in there and compare the sound. So, if anyone near me has a set they could loan me, drop me a note.

Thanks again for all the help. BTW, how do those curves look to you? It was the best I could achieve by messing around with the delay and/or phase function on the DCX.