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Well I've finally finished my Elliptracs built up from a kit supplied by Dave. Took a lot of work, but I'm pretty pleased with the result.......................I've wanted these to mate with some of the GPA 399 drivers that are basically a pancake version of the original Altec 288/290 series...........for those of you not familiar, a pancake version is basically a shorter version of the original, which I'm told means that it is not as comfortable down in the lower regions...........GPA product is made from the original tooling & dies used to make the vintage Altec Lansing gear.................................I'm running these through an ALK uni & there is definitely no issue with the 400Hz crossover point. They also have a 390 version which they claim will go to 300Hz, but I wanted the 399, as it produces a slightly crisper sound than the 390. .........these babies are nearly 8" in diameter & weigh nearly 10kgs...........................so , to cut to the chase.......................first the Elliptracs.......................compared to the ALK Martinelli Trachorn that I was using, I would say that they are different, rather than better..................having said that, I prefer the sound of these to the Trachorn.............much less directional......the sound doesn't come from the speakers anymore & produces a very wide soundfield..........................................& the GPA's.............................compared to the K55's (dual phase plug type) mated to the Trachorns................well there's really no comparison. Everything is better....the detail......the contrasts between instruments....the timbre of the instruments.........the ability to pick out individual instruments. They have a dimension that the 1" drivers just cannot produce, no matter their quality. They have a much fuller sound & an effortlessness that has to be heard. ...............................for the first time in a long time, I find myself listening to the music & not to the equipment & that's probably the highest compliment I can give them. .............................the final step is to upgrade the croosovers to ALK AP12-500's, not because they need to be crossed higher, but because they will improve the performance in the upper bass & lower midrange.

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Thanks.

So....sounds like I should just stick with the standard inductors that Al has used in this design............................15 #sledgehammer for the 2.7 & Solen #12 for the 2.4. What is the 1db step autoformer & is it superior to the 3619 that I already have?.................thanks from a novice in crossover design for your help......looks like you've saved me around $800 in inductor costs....................Found the 1db step autoformer on Bob's site....the 3636. So how is this superior to the 3619 apart from the finer gradation of control?

djk, I'm building an ALK AP12-500, so my question is really whether to upgrade the parts quality by using better quality inductors & caps? This will be used in a set of custom LS with Crites C1526 woofers & GPA 399 mids. Surely if I do this it can only improve the sound quality?? I've heard such rave reviews about the North Creek Audio inductors that I'm finding them hard to go past. Thanks for the technical explanation, but sorry, this doesn't make much sense to me, as a lay person with limited technical expertise.

I'm building a 500Hz crossover & confused as to which inductors to use. I need a 2.4 & a 2.7 in this design. Research so far says that they should be the lowest resistance for the best bass performance. I looked at the North Creek Audio, but their 12# resistance is 0.27 & 0.30. I'm looking at Solen 10 gauge which have a resistance of 0.17 & 0.18. I've also heard good reports about the copper foil coils, but notice that their resistance is considerably higher. Any advice as to the best type for the best bass performance. Thanks, John

Yes, that's one way to do it......or you can add the additional volume underneath the horn cabinet, just by removing the bottom access plate.......this makes the mod completely reversible & requires no modifications to the original cabinet.

Here's a plan of the LS so you can see how it works..........this is the view from the top......the speaker sits in the chamber (dog-house) & fires to the rear & then out the sides. La Scala Plans 1.pdf La Scala Plans 1.pdf La Scala Plans 1.pdf La Scala Plans 1.pdf

Thanks Dean....will leave well enough alone.

Is it possible to replace the 3619 autotransformer in the ALK universal with a series of fixed resistors?................Is this a worthwhile project to do to improve the sound quality?...............How would they be connected into the crossover layout? [*-)]............Thanks, John

QUOTE: 'I found the spec's and that is not the way I want to go. If the driver is not rated to go well below 400Hz I ain't going there. If I take this dive it will be as near no comprimise as possible or I just am not going to do it. I hope you have great luck with it. I just only want to do this once. I already went the partial way with the ALK trachorn. I want my upgrade to not have me double guessing it later. " END QUOTE:.........................................My thoughts exactly.......but this driver is the new version of the Altec 288. GPA manufactures it from the original die & tooling that Altec used....................................There are plenty of people who successfully use the 288 crossed at 400Hz & this is one of the most highly regarded drivers around. Don't be fooled by all the talk of 2 inch throats & being able to go down to below 400Hz & remember that specs aren't the whole story.............. Not really recommended for high power PA usage at 400Hz, but for home use, this will not be a problem. If you're worried about it, use the AP12-500 & the AP15-6K crossovers, which is what I'm going to upgrade to down the track...........you won't find a better mid range unit.......not cheap (my pair will be the best part of $1000 landed here in Oz), but definitely worth it.

I'm just about to. I should have the Elliptracs finished in about 2 weeks & I'll be mating this with some GPA 399 drivers. This runs through Al's uni's & the top end is JBL 2404H. I'll post some pics when it's done.

I thought the 2404's were better than anything else I had tried........standard Klipsch K77, APT drivers, Beyma's & also better than the JBL slot......much smoother & cleaner than the slot, but with great extension. It should be crossed over around 10K to get the best performance.

I had the same set up for a while & thought that the mids sounded better without the rubber washer. I'm still using the 2404's & they sound great.

Beautiful work!........look forward to your full description of the build.

Very impressive..............what network were you using before this as the basis for comparison? I'm doing a build of the AP12-500 & the Ap15-6K to replace my uni's. I wasn't sure if the ES type were for me, in regards to the steep slope, so have gone for a middle of the road version with the AP series......very interested to hear your subjective comments on the performance of the ES.

I have a set of GPA 390's that I'm about to mate with Dave's Elliptracs ..................the mounting bolts should be identical to your 290's.....................the adaptor system is a great way to combine the 1.4" drivers with a reasonable size horn & the adaptor system doesn't interfere in any way with the performance of the horn.

Yes, that's exactly what I'm after........Really appreciate you finding this..............Cheers, John

Maybe I didn't explain correctly. Yes, I will drill holes in the mounting board, route all the wires underneath & connect all the components direct to each other. The problem arises when you get to the terminal block for the connections of all the crossover wires & the outputs to each of the drivers, ie; to the bass, mid & treble. So, instead of the terminal block I was thinking brass threaded rod with nuts top & bottom. Sort of like a home made version of a binding post. Marvel.....I saw Greg's crossovers......that's where I got the idea.

Need some advice on terminals to use for my latest crossover build. I want to run all the connecting wires underneath the board, leaving the components on top of the board. I thought of using binding posts for all the connecting points, but it becomes very expensive, as I will have 10 connection points. Then I thought to use brass threaded rod.........I can just put a nut & washer on the bottom & on the top I could put a washer with a brass domed nut to give a better finished look. What is the opinion of the conductivity of brass for these connections? I know copper would be better, but I have found that impossible to source. I would normally use a terminal block from Mouser (538-38780-0110) which is zinc chromate plated screw terminals in a thermoplastic housing. Any thoughts appreciated, John

This should be some help........http://forums.klipsch.com/forums/t/119082.aspx

Yes, point taken, but the principle remains the same - "garbage in - garbage out". So the source remains the most important component & there on down the chain, until you get to the speakers.............................Your speakers can't reproduce a signal that doesn't get to them.................................my proviso is that I agree with Tom Mobley & be prepared to open your wallet!

So Linn must have been barking up the wrong tree all those years ago when they revolutionized the hi-fi world with the Sondek?

You know what they say......."Garbage In - Garbage Out"