605 TIME DELAY CROSSOVER

[jmarkwart]

Don,

No, I don't have access to any 605s since testing a friends pair a couple of years ago. I don't expect to get to Chicago anytime soon.

I do have a pair of 604-16Xs without crossovers though. They have ferite mags with less voice coil separation than 605s and should only require about .2ms of woofer delay.

I would like to hear your 605 circuit someday.

Jeff

[donaldpatten]

Jeff;
You have a open invitation to stop by any time.
If you are intrested in testing and building low pass time delay sections to test with your high end, I would do the math?
Don

[Seadweller]

While you've got the calculator out , could this crossover be tweaked to work with the current Great Plains / Iconic iteration of the 604?

I'm using the Great Plains standard crossover, and while it's purported to be an improved version of the original, my system has a significant amount of midrange energy, most noticable in the voice range. As such, there's a very forward character to the system that washes out detail, wreaks havoc on the spacial presentation, and smears the music on complex passages.

I just put together the parts list for Jeff's crossover, but I might take a peek at this one too....

Thanks!

[Todd W. White]

Which 604 are you using with the GPA crossover?

[dr.joe]

While we're on the topic of crossovers for the 604, what about the final iteration (c. 1998) of the Altec 604-8K?

I've read on (I think) Audio Asylum that these were made with a LF magnet different from the earlier 604-8K that emphasizes the midrange and makes it seem as if the driver has insufficient bass response.

Is this simply "unfixable" or can modifying the stock crossover or building a new one restore a proper balance between mids and lows?

If so, are there any schematics or formulas available to accomplish this?

(I ask because I've got a pair.)

Regards,

Joel.

[Seadweller]

Hi Todd,

I'm using the Great Plains 604 drivers, along with the standard crossovers I bought with the drivers....Great Plains shot me over a couple of schematics, and I didn't realize they evidently also offer a version with L-Pads....I'm not sure if that would cure the excessive midrange energy or not...

[Todd W. White]

The later series of 604-8K's used the EV DH-1 magnet, thus giving it much more midrange than the earlier models. The perception was it didn't have enough bass, which wasn't true - it had the same bass, but too much midrange.

The current GPA 604-8H-II fixes that - Jerry Hubbard redesigned the motor structure to compensate for the larger magnet. The result was a much smoother response with a balanced midrange, and the perception that it had improved bass over the older models.

I have personally tested the new version in hours and hours and hours of critical listening tests of high-quality (many of them live) recordings of various styles of music and have never heard the 604-8H-II's have "too much midrange". In fact, when you measure the frequency response of this speaker using the GPA crossover, also designed by Jerry Hubbard, the TEF analysis is stunningly smooth.

Possibilities:

1. Inferior recordings - 604's make people hate their favorite recordings because they paint the audio picture "warts and all". Unless they were mixed properly and without "coloration" (i.e., messing with the final eq to compensate for the crummy monitors the studio mixer was having to listen to), you may be hearing how really awful the recording itself is, but are blaming the speakers. Happens all the time...

2. Something could be wrong with your electronics. Sure is possible, even these days.

3. Incorrect box size and/or tuning. This can have the same effect the larger magnet had on the "K" series.

4. You're prejudiced. Yours ears have become so accustomed to bad sound that, once you hear ACCURATE reproduction, your mind says "That's wrong - there's too much of ..... there!", when, in reality, you're hearing what's REALLY THERE for the first time, and your mind hasn't adjusted to good sound. Hence, it thinks good sound is bad sound. Believe it or not, this happens more often than people will either realize or admit - lots of people's ears are so prejudiced towards bad sound that they actually think it's GOOD. Why do you think people keep buying EAW and Soundspheres?

I once had an acoustical consultant tell me, after I had explained why the Altec HF drivers don't exhibit the upper harmonic distortions that turn the letter "S" into "sssthhh", that he preferred the distorted audio to the non-distorted reporduction offered by the ALtec 288/299 drivers!

[Seadweller]

Thanks for the input Todd......

Certainly, I can't rule out bad recordings, but I can safely rule out electronics issues.....I'm pretty sure I've got the right box tuning, as I used a fairly well tested design, however I'm sure part of it is getting used to a more accurate representation of the music.....

I've used various types of program material, some recordings which I know are good, and some which I know are bad, to make sure I have a good cross section for reference purposes....On all material, the strong midrange energy is present...

I may have to experiment with placement and room acoustinc, but there is definitely an overwhelming presence in the midrange....I've read where many other folks have experienced the same phenomena, which caused me to research alternatives....

I love the way the system brings voices forward, and the detail is astonishing, but I still feel there is too much midrange energy, which dismantles the soundstange, masks detail in the treble region, and smears complex passages....

I will say this however; this is one remarkable driver, and I'm convinced once it's dialed in, the system will rival the best available anywhere, at just about any cost....

Do you feel some value changes in the current crossover might address this issue?

[Todd W. White]

What size boxes did you use, and what tuning frequency/method did you use?

Room acoustics sure can do all kinds of things - pity you don't have a TEF: you could find out what the room is doing to the sound.

Did you buy them directly from Bill/GPA?

Are you running your tone settings flat?

Variable L-pads are nice, but they DO fail...

[waitinonthebus]

"How does it sound compared to the stock XO?"

I've replaced caps in the stock and did a comparison and was quite impressed with the improvements. I had not mastered the testing apparatus, being a novice, so I don't have in-room measurements that you can sink your teeth into but I can tell you what I heard.

Articulation was greatly improved, HF was less rolled off, and instruments came outside of the box. The stock XO imaged well but the soundstage was contained within the perimeter of the speakers, mostly. Articulation was the biggie; applause before was a big sshhhshhshhshhshs after it sounded like hands clapping together.

Big fan here.