Looking for Mid-Bass Impact

[Lancer]

I like that! - "an audio dooms day machine"

Well, it sounds to me like we need to drag a bunch of this stuff up to Rodd's house and give it all a listen.

[Mrs Lansing]

I would make the trip if I were over there..Rodd's a hell of a nice guy!

[pangea]

I'm currently using a Rane AC23 as a stand in for what will (at some point) be a customs crossover. I had a customized Heathkit xover for the low xover point. The upper xover point was a hybrid active/passive line level with a Nakamichi Black Box for the active portion. This began to malfunction a while ago so hence the Rane.

Crossovers were low LP @ 18db/oct @ 70Hz and low hp @ 6db/oct at ~90Hz. On the high xover it was 12db/oct @ 1250Hz for lp with a passive line level cap (6db/oct) hp @ 5kHz. This was to tame the lump in the response of the Radian diaphragm in the TAD 4001 driver.

I'm sure there is merit to physical time alignment and signal time alignment. I need to spend some time working on these issues. I first want to gether the right complement of drivers before I dive too deeply into that issues. Although I have not ignored it completely. The drivers and their application, I feel, will be the main factors to deal with.

With all those different slopes and with some cabs being vented and others being not vented, how do you keep track of all the phase-shifts and how do you know it isn't the x-overs that create the lump you mentioned?

BR
Roland

[johnaec]

I like that! - "an audio dooms day machine"

Now THIS looks like a JBL doomsday machine... http://cgi.ebay.com/JBL-BTX250-NEAR-...QQcmdZViewItem

John

[Roddyama]

Well, it sounds to me like we need to drag a bunch of this stuff up to Rodd's house and give it all a listen.

I would make the trip if I were over there..Rodd's a hell of a nice guy!

WOW, too nice.

[Roddyama]

With all those different slopes and with some cabs being vented and others being not vented, how do you keep track of all the phase-shifts and how do you know it isn't the x-overs that create the lump you mentioned?

BR
Roland

Actually Roland, it's not any more complex than any other 4 way system. Only the woofers are ported so the greatest phase shift is in the low cutoff region. The mid-basses are critically damped (Qt=.5) closed box so you're not going to get much less phase shift in any other system. The xover here is what used to be called (I think) "Minimum Phase" used by Dalquest and a few others back in the 70's and 80's. Basically a 18db/oct lp and a 6db/oct hp.

The bump in the response of the 4001's could be clearly heard. This was verified by Radian. The "hump" is very broad and extends the entire range of the driver from 600Hz to 15kHz with the center at about 3kHz at +12db referencing the -3db points at the ends (+15db to these points). The xover here is this cap plus a simple 12db X 12db butterworth. Again, this is far more simple than many xovers today.

Remember, you're going to get the phase shift regardless if the xover is a passive line level, full active, hybrid, or full passive hi-level. As i said before, I haven't put a lot of thought into time and phase alignment, but I have not ignored it either. Everything is in separate boxes/baffles so can be moved relative to one another easily. once I have the drivers I want, I will look more deeply into the phase issue.

P.S. Now with my older xover on the fritz, I've just put a Rane AC23 in place with has xover slopes of 24db/oct throughout. The initial listening is less then enthusiastic. I'will need to work more quickly toward my diy active xover which I'm gathering parts for now.

[Dynacoman]

The short spelling for "Audio Doomsday Machine" is BOSE.

[scott fitlin]

Rodd, do you have an original TAD diaphragm? It would be interesting to see if the original manufacturers part exhibits the same wide bump in the response!

Considering that the TAD 4001 is reknowned for its ultra superb clarity, efficiency, and flat response, I guess I would find the results from the radian diaphragm unacceptable. Of course, i also understand the TAD diaphragms are hellaciously expensive, but thats the route i`d go.

I have tried the radian replacements for my JBL 2441,s and stuck with JBL aluminum diaphragms.

[Roddyama]

Rodd, do you have an original TAD diaphragm? It would be interesting to see if the original manufacturers part exhibits the same wide bump in the response!

Considering that the TAD 4001 is reknowned for its ultra superb clarity, efficiency, and flat response, I guess I would find the results from the radian diaphragm unacceptable. Of course, i also understand the TAD diaphragms are hellaciously expensive, but thats the route i`d go.

I have tried the radian replacements for my JBL 2441,s and stuck with JBL aluminum diaphragms.

I had the original TAD diaphrams when I bought the drivers. I cannot honestly say they had a fair listen from me as the system was in a state of flux when I first installed them and until they went south during some avoidable system glitches. Needless to say, I was very upset with loosing them and literally sent them south to a TAD dealer in FLA to experiment with as the beryllium domes were still intact. He was going to put a new experimental suspension on them.

The Radians actually sound good. The hp filter cap (theoretically) makes the response +-3db from 1kHz to 15kHz. I have no complaints about the Radian replacements which will take double the power to boot and cost 1/5 the cost of the TAD's.

[scott fitlin]

I had the original TAD diaphrams when I bought the drivers. I cannot honestly say they had a fair listen from me as the system was in a state of flux when I first installed them and until they went south during some avoidable system glitches. Needless to say, I was very upset with loosing them and literally sent them south to a TAD dealer in FLA to experiment with as the beryllium domes were still intact. He was going to put a new experimental suspension on them.

The Radians actually sound good. The hp filter cap (theoretically) makes the response +-3db from 1kHz to 15kHz. I have no complaints about the Radian replacements which will take double the power to boot and cost 1/5 the cost of the TAD's.

I hear you. I would have been upset at losing the TAD phragms myself.

Still, I would have liked to hear your thoughts on the TAD phragms, hearing them properly.

[Roddyama]

I hear you. I would have been upset at losing the TAD phragms myself.

Still, I would have liked to hear your thoughts on the TAD phragms, hearing them properly.

My initial thoughts on the original TAD diaphragms was that they were very detailed but not dynamic enough, almost the point of being "laid back", but not quite. You could say, "smooth" but too smooth. Far too "polite" (Thanks for the word Earl ) for my tastes. It was very disconcerting for me as what I heard was totally unexpected having listened to the LE85's for 20 years. I was continually trying to find something I had done wrong in my setup. I believe, looking back, this may have added to the situation that ultimately caused their failure.

I don't know if you know this, but the TAD diaphragms and suspension are all one piece of beryllium. The voice coil former is bonded to the diaphragm/suspension. This is what makes them so fragile. I find it hard to believe the material used in the diaphragm because of its stiffness can be used in the suspension as well. It just goes against logic.

[scott fitlin]

Yes, the TAD diaphragms are known to be delicate, and their cost makes it a prohibitive driver to use!

Its interesting you say you thought you did something wrong during setup, becuase you liked the JBL LE85,s better!

I bought TAD 4002,s to replace my JBL 2441,s, had been told by several to get the 4001, but the cost factor and TAD recommends the 4002 these days, so I bought! I also, spent a few weeks trying to figure out waht I wasnt doing right, then trying to get a sound I liked from the 4002,s, and then putting the 2441,s back, and finally accepting the fact the I like JBL!

I have heard the 4001,s and they are good, but there is a certain sound from those JBL drivers, crisp, sweet, and yes, DYNAMIC!

[Cyclotronguy]

Hiya Rodd,

For what it's worth... my wife will not give up the TAD loaded JBL 4560's on the living room hi-fi / video system. If you can find the time to get out to California, come on up.

Cyclotronguy

[Mr. Widget]

For what it's worth... my wife will not give up the TAD loaded JBL 4560's on the living room hi-fi / video system.

A wife like that is worth a lot!


Widget

[Cyclotronguy]

Second time around was a charm. JBL 4560's were the second choice... we couldn't fit the horns she really wanted.

Cyclotronguy