Altec 604-8K vs. Great Plains vs. Iconic Crossovers?

[Seadweller]

There is a pair of "new" Altec 604-8K duplex speakers on eBay, along with "new" 604-8K X-overs that look like will sell in the $1.6K range for the set.

I've got cabinet drawings in the works, and construction will start soon, therefore I need to start thinking about getting the drivers and X-overs. I've been leaning towards the Great Plains drivers and X-overs, which run about $1.5K for the set. The Icnonic "supercrossovers" have been recommended, but I'm not going to pay $700 for the X-overs, and $1.3K for the drivers, as I'll have $2K in this thing without the cabinets!

What is your opinion about the original Altec 604-8K driver vs. the current Great Plains iteration, and more important, how good is the 604-8K X-over? Would I be better off with an original set of Altec drivers and X-overs, or is the Great Plains iteration (with their X-over) a better route to take????

Thanks!

[Seadweller]

By the way, I'm assuming neither the Great Plains or Iconic X-overs have the frequency adjustments that the original Altec X-over's offer, but I'm not sure if this is a benefit or not......

[selmerdave]

Well if it's a close call I'll put in a vote for supporting the business that's around today doing good work. I know what you mean about the investment, especially when you consider the price of crossovers, but you don't have to go all the way with the crossovers. If you can DIY reasonably I'm sure Jeff Markwart's design could be done without major investment and all reports are that the results are outstanding. Down the line if you decided to go all out you could then fork out the money for a top-shelf Great Plains or Iconic crossover.

Dave

[Seadweller]

Thanks Dave.......

I checked with Jeff directly, and he was kind enough to respond that he does not have a design that will work with the current Great Plains iteration of the driver. Unfortunate, because I have read nothing but raves about his design.

[Todd W. White]

The Great Plains 604-8H-II has a proprietary crossover designed by Jerry Hubbard, former head of Acoustic Research at Altec Lansing. It uses fixed resistors, rather than the L-pads which have a bad habit of getting dirty and/or burning, depending on how hard they're pushed.

The speaker sounds MUCH better, to my ears, than the later version of the "K" (and that's using the "K" crossover), and WOW does it sound even better with Jerry's crossover! If you don't know when the K's were made, you could be getting the ones that don't sound as good...I'd vote for getting new ones from Bill.

The GPA crossover meets Jerry's spec's precisely, as does the one made by Iconic. The difference is in the type of components used, the one you choose to buy would be a matter of personal preference.

[jmarkwart]

Seadweller,

I agree with both Dave and Todd ? if they are at or near the same price, I?d go with the GPA duplex versus an older 8K of unknown performance. I?ve measured the early variety of the ferrite magnet 604, (604-16X), and a pair of the current GPA offering, and can attest that the performance of the GPA units surpassed the early ferrite 604s in all respects.

As far as crossovers are concerned, I will make a recommendation for the DIY crowd if the current Iconic and GPA filters are a bit dear at this time. Based on my measurements of the GPA unit, a second order Butterworth centered at 1500Hz with a 30% spread of crossover frequencies makes an excellent sounding filter. Combine this basic filter with the MidFreq EQ circuit from my simplified 604-8H network, reverse the compression driver acoustic polarity and enjoy. For the High Pass use C1 = 6.33uf, L1 = 1mH; for Low Pass use L2 = 2.7mH, C2 = 7uf. The first DIY builder of this circuit reported outstanding results.

Jeff

[smallpond]

I am the first user of Jeff Markwart's crossover circuit for the new Great Plains Audio 604 8H-II that Jeff mentions above. In my MLTLs it sounds absolutely superb.
I know that there are varying opinions on what is the best crossover frequency for this driver and would love to hear them since 1500hz seems to work so well in this network in my system. Now that I have had the opportunity to find the best overall settings for the mid and high frequency L-pads on this network, I am wondering if there might be a sonic benefit to replacing the L-pads with fixed resistors?

At any rate... Jeff Markwart's crossover circuit is very highly recommended.

Jay Fisher

[GM]

Originally posted by smallpond:
I am wondering if there might be a sonic benefit to replacing the L-pads with fixed resistors?

<font size="2" face="Verdana, Helvetica, sans-serif">Short of using large, high current rheostats, long term, pots will deteriorate due to arcing. Remember, ~99% of all electrical problems are connection related, whether it be moving contacts, wire terminations, etc.. I have 'repaired' many speakers by swapping out L-pads with fixed resistors that most folks would have either replaced the driver(s) or trashed them.

[jmarkwart]

Thanks Jay,

The design is centered at 1500Hz, but then spread 30% to accomplish phase correction. This makes the actual crossover points (-3dB) 1154Hz for the woofer and 1950Hz for the compression driver. This spread of Butterworth -3dB points away from 1500Hz also leaves reasonably flat SPL magnitude throughout the crossover region.

Fixed resistors in place of your current L-pad values makes sense if you don't find youself needing to adjust them.

Jeff

[Davidg]

Hi everyone, I have a pair of GPA 604-8H-II's in a pair of cabs very similar to Billforts design and am running the GPA crossover and so far they are amazing! I have never heard anything like these speakers at any price, everytime I fire them up I am blown away at the clarity and detail, have you ever had Pink Floyd or Jewell live in your front room! how about Ride of the Valkyrie performed right there in the flesh!! Ha I've had them all in my little 16 x 20 front room!! LOL!

I am very interested in building Jeff's crossover design and was wondering if anyone has had the opportunity to listen to any of these designs side by side for comparrison and what are the differences like?