605 TIME DELAY CROSSOVER

For the DIY here is a Time Delay Crossover that delays the LF signal about 0.4 ms.
[IMG]http://i130.photobucket.com/albums/p260/dlp4341/ESu4DH-1.jpg[/IMG
[IMG]http://i130.photobucket.com/albums/p260/dlp4341/IMG_0493.jpg[/IMG
Any intrest?
Don

If anyone can help on how to make the IMG s come up please post.
Don

If anyone can help on how to make the IMG s come up please post

Hello Donald, do you mean this?

http://i130.photobucket.com/albums/p...1/ESu4DH-1.jpg

http://i130.photobucket.com/albums/p...1/IMG_0493.jpg

That was a lot of work. wow. I will study it.

Would this crossover work for the 604C also?

ArtJ: Thankyou on the IMGs

Dylanl: This could work on a 604C, if the impedences and time delay are the same. Or the circuit values would need changing.

RE Testing: I used a dual trace scope and a raised cosine pulse. The triggering was on one chl monitoring the power amp out. An electret mic 12" on axis picked up the acoustic output, driving LF , HF, or Both; to look at the time delay and FFT for Freq Resp. Actually my Mac & software supplied all the testing.
I'll try to post some curves
Don

Maybe as a quick note to get the ball rolling,
Has this circuit been field verified with a dual trace scope?
My experiences in the past is that the proximity of components
and their tolerances have a profound effect on the actual outcome,
especially involving phase shift.


http://www.hostboard.com/forums/

I am interested in your findings. I need to build a crossover for the 604 and Jeff Markwats design is very costly.

Dylanl:
Using Parts Express, this design cost estimate would be $ 150. I think Jeff's would be less.
Don

Don,

Congrats on your 605 Time Delay Crossover! As you undoubtedly know, it's an interesting
challenge to take on 604/605 crossover phase shift issues.

I too designed an all-pass delay type of 604 filter, but ultimately decided not to add the
extra parts required for the LP as long as I could get a similar phase result at crossover
with f3 spreading of second order high/low pass networks.

I'm naturally curious though - How does it sound and compare to the stock crossover?

Jeff

Jeff:
Do you have 605's? Or do you get to Chicago?
I would also like to test a stock 604E to get a design for it. Sound? It does sound different than an N1600. It looses some of the horn sound. To really evaluate the sound you need to hear a pair to get the localization too.
Don

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

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

While you've got the calculator out http://www.hostboard.com/forums/ , 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!

Which 604 are you using with the GPA crossover?

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.

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...

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!

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?

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...

"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.

I'm very wet behind the ears when it comes to speaker design, so of course I didn't model the system myself....I guess it would be nice to have some measurements taken in my room!!!

The enclosures are based on the specifications that Jay Fisher kindly provided me...I bought the drivers and crossovers brand spanking new from Great Plains Audio...My pre-amp does not have tone controls, so everything is set flat by default, and the Great Plains crossovers I bought along with the drivers do not have L-Pads...

I wish I knew at what frequencies this anomaly was occuring, but I don't have the tools to make these measurements, and I wouldn't know how to use them if I did! http://www.hostboard.com/forums/

As I mentioned, I don't believe I'm the only one that has experienced this phenonema, and many have reported better results using different crossovers, many of which have indicated that this excessive midrange energy was tamed with a different crossover design (the Markwart crossover for example)....

I don't know if upgrading the standard Great Plains crossover to higher quality components would tame this midrange energy or not, and honestly, I don't know what components Great Plains used to begin with....I was so excited to get the cabinets home that I didn't give the crossovers a second look before I installed them....

Any advice would be graciously accepted!!! http://www.hostboard.com/forums/

Seadweller
Did you note the time delay on your response?
Nov 23, 2006 to Nov 28 2007; a year!
The math : all my work was on factory ( GPA re built ) spec: 8 to 16 Ohm LF . I think that means 12 , and is close too the DCR I have measured.
The BESSEL low pass filter?s time delay , is very sensitive to load impedances.
Hence the Zobel network flattens the LF to 13 Ohms. The delay time offsets the mechanical spacing of the two drivers. To change either or both of these changes all the low pass parts.
I do have a design for a stock 604E that is 8-16 Ohm and with a Alnico magnet ; but no 604E to try it on.
Both waitinonthebuss and I have 605As.
Don

Seadweller,

I think most comments about improvements to the stock crossovers are in reference to the N1500A's from years ago. I don't recall reading many negative comments about the GPA crossovers, which I'm pretty sure are a significant improvement on the N1500A. I'm not sure what the issue you are describing would be though, and I can't say I've experienced it either with my current active setup or my prior passive setup using simple 2nd order networks with a fixed 4-db pad.

Dave

As I said, Jerry Hubbard did the design on the GPA crossover, and I've listened to the combination in the Stonehenge V (9 cubic ft tuned) enclosure and not heard what you're describing.

Questions:

1. Are your electronics tube type, transistor, or other?

2. What source material are you using (CD, LP, cassette, R2R, etc.)?

3. What size box volume does your box have, and what frequency is it tuned to?

Turntable/preamp sans RIAA EQ?

I'm using a SS amplifier with a hybrid tube/SS preamplifier, with CD as the primary source....

I calculate the boxes at around 10.5 cubic feet, but what they are tuned to, I have no idea...I simply used the dimensions provided to me, along with the port size/location and length, distance from the floor, etc.

Observations:

1. Some of what you're hearing could be distortion from the solid state (ie, transistor) amplifier and/or the SS side of the preamp, as we all know that SS electronics produces more odd-order harmonic distortion than does properly designed and operating tube stuff.

2. Some of what you're hearing is probably caused by improper box size, and/or tuning.

3. Distance of the 604's from the floor could have a bearing too.

4. Standing waves and unwanted reflections, in addition to the reverberant field, all of these could be combining to negate the bass response, thus making them sound like their midrange heavy.

5. Distance of the cabinet to the walls can have positive or negative effects, too. If you had a TEF analyzer, you could see what is going on and know for sure.

6. I also think hearing is different for each person, and some people have LF hearing loss due to damage from various sources of noise (note: rock music is included as a source of noise in my book :-) ).

I have played the same speakers in various environments, both small (demo rooms, small listening rooms) and large (our church auditorium), and found the perform well in all environments, but your room may be interfering with their performance. I know that there is a famous recording studio in NYC that has them and LOVES them, and they're a pretty picky group.

My ears tell me that "real", aka live, recordings - not ones that have been "sweetened" sound really really nice on these speakers, as do recording made on older (pre-K) 604's and UREI's (with OEM'd 604's) in them. Other recordings, where the mixdown is eq'd to compensate for the crummy speakers, don't fare so well..

That said, my guess is the box has something to do with the overall problem you're experiencing - what is the vent shape & size? These dimensions, plus knowing the location of the 604 from the floor, will help us figure out what's going on (maybe). It would also be good to know what wattage your amp is, and your room dimensions and speaker locations (or did you already mention that - I'll look again and see).

Thanks for taking the time to diagnose my problem!!!

Regarding your specific questions, the vent size is 6" round, in the center of the bottom of the cabinet...The cabinet is approximately 10" from the floor...The cabinet is meant to be an MLTL configuration...

The driver is around 34" from the floor, and the speakers are on the short wall of a 12x16 room..I have them placed about 2' in from the side walls, and 2' from the back wall...

The amplifier (200/wpc) is greatly oversized for this system, as my previous speakers were hideously inefficient, however it does operate in class A up to 20/wpc..

The excessive energy I'm referring to seems to be in the range of voices, so from 300HZ to 3500HZ maybe?

I was under the impression that those cabinets were meant to be placed against a wall for low end reinforcement. The Six Moons write up of a similar box and driver indicated that the speaker was very well balanced and even a little laid back.

How deep is the vent? I'm guessing it's a ducted port, right?

You may not have it tuned properly - one of the math geniuses here will have probably already have the duct area figured out by the time I can get my HP 41CV Programmable Calculator (yes, I still have it, and sometimes use it. Along with my thermal printed and card reader - at one time many of we Altec Engineering Sound Contractors had to have them.) and figure it out...it will be interesting to find out.

Also - I thought MLTL cabinets are usually designed to have some pretty hefty amounts of acoustic damping material (aka fiberglas). It may be that you're sucking the LF right out of the 604's and are left with mostly midrange and up.

The crossover really crosses around 1,500 to 1,800, as I recall. I can't see the LF cone getting annoyingly harsh, and the rolloff is such that you're really not getting into the horn by itself.

I think it's the box and/or box placement.

I read that article numerous times, and I'm not sure if they used the Great Plains crossover or not...There was an L-Pad in their crossover, and mine does not have one, but I don't know if it's the same general circuit or not...

Despite having read the article many times, I missed this comment, which perfectly explains my situation:

"Pretty early on, we added another two ohms of resistance to the three ohms just ahead of the high-frequency output on the crossover board to address the shoutiness originally experienced. This knocks the tweeter down by about 2dB and helps a little but does not completely eliminate the shoutiness."

"Shoutiness" is a perfect term to describe what I'm experiencing....The excessive midrange output I've been trying to describe actually pushes vocals (and other music in that particular range) so far forward, and with such intensity, that it overwhelms the rest of the spectrum...As a result, it masks detail and smears complex passages...

I'm assuming this must be a driver/crossover characteristic, and not a cabinet/electronics/room acoustics issue then...If so, I would imagine it could be addressed with crossover modifiations/changes?

Hi Todd,

I used Owens Corning (704 I believe) fiberglass acoustic insulation on the inside of the cabinet...My bass response is actually excellent, and reproduction of instruments at the other end of the spectrum (triangles for example) is spooky! I've never heard a speaker system reproduce things with such detail...

I can't imagine the woofer "beaming," and I would bet that the "shoutiness" I referred to in my other post is definitely coming from the horn...

Forgive my ignorance, but the cabinet and/or tuning would not impact the response of the horn, would it?

No, the cabinet tuning won't affect the horn, really, but it WILL affect the actual type and amount of LF you get out of the system, thus affecting the perception of midrange performance.

The "shoutiness" could be ascribed to the crossover, but I doubt it - Jerry Hubbard is a stickler for natural sound reproduction, and the crossovers I've listened to on the 604-8H-II sound great.

The article's author built his own crossovers.

My guess is still with the box - a combination of things, probably: box tuning, box damping, height of speaker from off the floor, and box location with relation to the walls of the room.

Incidentally, as an old acoustician, I have to ask -

What kind of wall, floor, and ceiling materials do you have???

It's a very "bright" room; wood floors, plaster walls, and no fabric wall coverings...Interesting thing is, I've listened in the near field as well, and the characteristic still remains...

I'll experiment with placement this evening, to see if things balance out, but I've had placement issues with very finicky speakers in the past, and I have yet to identify placement as the culprit when dealing with excessive midrange energy.

Given the nature of the energy, and my estimation of the frequency at which this is occuring, I'm confident it's within the range of the horn...The problem is, the systems response at the extremes is magnificent, and I'm afraid that bringing the bass and treble up to match the midrange will result in too heavy a bass response, and too much treble energy....

Maybe I can talk someone into renting me a pair of Markwart crossovers to see if that does the trick, before investing in the parts! http://www.hostboard.com/forums/

You could disconnect the HF drivers and see if the characteristic goes away, that would confirm whether or not that is what you are hearing.

Dave

OK I will give in and write about 604s.
If you check the resistance of your drivers and woofers , they may be different.
I like the suggestion , take them outside. We did some testing in a box buried with the baffle board flush to the ground and the speaker pointed up. EV did testing on their flat roof...great low end curves.
Don

Howdy,

Wow, taking these outside would be tough, because they're HUGE!

Anyway, the sound insulation is on the back, top, and one side of the cabinet, per the design parameters....I believe the CSA is around 426, but I'm on the road and don't have access to the exact data....The internal dimensions are in the neighborhood of 24" wide by 18" deep by 42.5" high....I know the height measurement is accurate, because it was very specific...These are all internal dimensions....

I'll try disconnecting the horn to see if the midrange energy is tamed....The only thing wrong with that idea, is that I didn't think of it myself... http://www.hostboard.com/forums/

Thanks!

You can move them pretty easily - two-wheeler some blankets, muscles, and some common sense, and you're done.

If the offending sound is IDENTICAL in both speakers, then it's something common to both. THese could be:

1. Crossover design.
2. Crossover components (failure, mismatch, or wrong values - they could be labeled wrong: it has been known to happen).
3. Room acoustics.
4. Box design/tuning/damping.

Is the box a standard rectangle, or does it have internal stuff going on. Seems like I remember the MLTL cabinets have different stuff going on inside, much like the tuned labrynth boxes we used to build in the old days...

Todd,

Apart from bracing MLTL cabinets are just empty boxes like BR. My understanding is that the action comes from the location of the driver and the size of the port (although it uses different principles than does BR - AFAIK). Seadweller has some pictures of his cabinets during construction in the other thead.

http://www.hostboard.com/cgi-bin/ult.../f/3729/t/3187

Dave

Thanks so much everyone! My apologies for hi******* this thread, as it wasn't my intention...

I'll do some experimenting this weekend, and report back......

Have a great weekend!!