TAD 1201M + SA 8535 - My Ooogly Box Xperiment

So, for a long time I have wanted to replicated the test set up that I put together 15+ years ago. At the time I had SA8535 ribbon drivers and had gotten a pair of TAD 1102 on approval from TAD. Had to send them back to TAD because I didn't want to fork over the $$ they cost. But they were incredibly dynamic drivers.

Fast forward to today, and I had acquired a pair of TAD 1201M, not exactly the same driver, but both use the PG, polymer graphite cones, and both are apparently out of production, and certainly not being sold in North America, and if they were, they would be incredibly pricey.

I slammed the TADs into my test mule MDF 12" box and dropped the 1201 in on top of some Moretite (tm) window putty and shot some screws in with my trusty LiO powered Harbor Freight screwdriver/gun. Checked polarity and wired, before screwing in...

The SA ribbon was dropped on top with the (not-so-great) "waveguide" in place. A suitable first order cap was applied to the SA along with appropriate padding resistors to match the senstitivities.

Fired it up with my Quadripole subwoofers, and magique!!

As expected, very clean, clear and nice, super dynamic too.
Compared very favorably with my horns + 15" midbass.

Excellent first pass.

_-_-bear
 

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Well in truth this is still not a design without its share of issues.

One of the big ones, as with all mid/tweeter combinations is the distance between the acoustic centers (vertically) and the way that effects the response as one moves up and down across the center of that axis, of course WRT the xover frequency...

Also this is a very non-optimum box for this driver, too large and ported... but ok for a first pass... :D

_-_-bear
 
a pair of TAD 1102 (...) and I had acquired a pair of TAD 1201M, not exactly the same driver, but both use the PG, polymer graphite cones
Hi Bear

I don't think the cones are identical.
I have TM1201H here, and also had TL1101H a while ago (which cone is very similar to the TL1102), and the cones are really different.
The TM1201H uses a polymer graphite cone with a "metal" feel to the touch, whereas the TL series uses a more conventional paper pulp cone (mixed with various other materials).

What crossover frequency and topology are you using?
 
Afaik there were two versions of the 11XX one was the "low frequency" version the other the midrange version. My recollection is of the midrange version, and the one I had did have the PG cone. It would have been impossible to mistake that, and the odd mounting size.

But, now I have to search and see if I can find an old copy of the brochure for the 1101 or 1102...


As of now there is nothing special in the xover, it's just a rough test set up. Not even rolling off the TAD at all, running the SA in on a first order... just to get an idea of what it might do when properly merged... obviously there is overlap like this...
 
Ok:

1102:

The cone is constructed of an aged natural pulp material which is both lightweight and durable. It is laminated with special film which is applied with a unique controlling paint.

1101h:

highly rigid pulp cone reinforced with Kevlar fibers.
The loudspeaker diaphragm is laminated with macromolecular film, and its surface specially treated to make it water-repellent and to prevent cone break-up from degrading sound quality.
 
Oh that... I understand based on the VAS that the optimum box volume is scary small... but I'll have to look into that more. Since I'm not planning on running these at outdoor concert volumes it may not matter that much what the volume works out to be.

Also, probably I'd go with sealed.
But my mind thought, well, why not get weird and do something like a small TQWT thing with it, since the operational frequencies will be relatively high, and squeeze out some extra "richness" in the upper bass?

That box you see was tuned to test some LF drivers... so it's tuned below 40Hz as far as the port, iirc... this doesn't sound half bad alone, of course not the bass I'd like, but not scrubbed free like many midrange drivers might be.

My larger concern is to get a wide enough baffle to support the lower mids/upper bass without introducing too much ripple. Then if the Vb turns out to be as small as it appears it will be, that makes for a tricky bit of design work, but not impossible. Looks like some sort of "wing" bit may be in order...

then comes the question of what to do with the tweeter.

I'm not thrilled with the waveguide. It does add some boost around the F3 point for the drivers, above 1500Hz. Without the waveguide they are rather flat. However the waveguide is handy for setback to align the acoustic centers of the 1201 and the 8535.

So in my mind I am considering trying a simpler cylindrical section over the "manta-ray" style stepped conic waveguide they are using. I could then build that to the depth required for optimal setback.

At that point it could be in a two piece enclosure that is flush between the two sections thus adding to the baffle area of the 1201...

See? It's a simple two way design. Nothing to it, nothing to think about at all.

I think this will end up being bi-amped.

_-_-bear

PS. if you remember back that far, dunno if you saw it, but my Focal system had 7V513 mids and the SA 8535 free standing on top... so they work ok freestanding.
 

Scott L

Member
Paid Member
2008-12-27 12:32 pm
Knoxville, TN
Spooky

Oh that... I understand based on the VAS that the optimum box volume is scary small... but I'll have to look into that more. Since I'm not planning on running these at outdoor concert volumes it may not matter that much what the volume works out to be.

Also, probably I'd go with sealed.
But my mind thought, well, why not get weird and do something like a small TQWT thing with it, since the operational frequencies will be relatively high, and squeeze out some extra "richness" in the upper bass?

That box you see was tuned to test some LF drivers... so it's tuned below 40Hz as far as the port, iirc... this doesn't sound half bad alone, of course not the bass I'd like, but not scrubbed free like many midrange drivers might be.

My larger concern is to get a wide enough baffle to support the lower mids/upper bass without introducing too much ripple. Then if the Vb turns out to be as small as it appears it will be, that makes for a tricky bit of design work, but not impossible. Looks like some sort of "wing" bit may be in order...

then comes the question of what to do with the tweeter.

I'm not thrilled with the waveguide. It does add some boost around the F3 point for the drivers, above 1500Hz. Without the waveguide they are rather flat. However the waveguide is handy for setback to align the acoustic centers of the 1201 and the 8535.

So in my mind I am considering trying a simpler cylindrical section over the "manta-ray" style stepped conic waveguide they are using. I could then build that to the depth required for optimal setback.

At that point it could be in a two piece enclosure that is flush between the two sections thus adding to the baffle area of the 1201...

See? It's a simple two way design. Nothing to it, nothing to think about at all.

I think this will end up being bi-amped.

_-_-bear

PS. if you remember back that far, dunno if you saw it, but my Focal system had 7V513 mids and the SA 8535 free standing on top... so they work ok freestanding.

Hi Bear,
Well, I guess I'm 15 years behind :)
I threw my 1201's in a utility box as well: 1.5 cubic feet, but I stuffed the port (not visable, on rear of enclosure). It's a real nice combo, but I keep on hearing systems with a tad bit more clarity in the mid/upper mid-range. I know, I know, you have told me on more than one occasion to lower my crossover point down from 3.5k to 1.2k (IIRC?) The never ending experimenter in me decided to try adding an Audax 4" aerogel to the mix. It sure did add the clarity I wanted, but at the expense of losing the time coherency of just the 1201/8535 combo. I'm going to take them back out and lower the x-over point. The TAD is a fine driver, but indeed limited to the range it does well (200-3.5K) but then again, maybe not even that high(?)
For a Night Club sure, home use... I'm not so sure.

best regards from Dixie,

Scott L
 

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I think you want to look at your signal chain and amplification.

The SA8535 is going to be like an open window to the rest of your system imo... the advantage of biamping is that you can eliminate the resistive padding on the 8535. IF ur not padding it, then it's a bit hot compared to the 1201. Also with the waveguide you have a bump up before the low freq rolloff, so it's a good idea to compensate for that.

One way to do that is with a series inductor since the rise looks much like a 6db/oct slope out to ~7kHz. So, the key would be to measure it, and size the inductor just right to achieve the closest to flat response possible. Another option to do that is with a slightly too large inductor paralleled with a suitably chosen resistor... that may not work properly for this, but it may turn out to be a better compromise. (gotta check and measure)

Without the waveguide it is flattest.

The other question is the slope ur using, that changes the way that the two drivers merge, and where the idea placement is for the tweeter, front to back, WRT the 1201.

I'd think the aerogel is not going to keep up with these two drivers nor is it needed as there is ample overlap between the 1201 and the 8535.

I suspect what you are hearing is the extra energy from the overlap + the rise in the 8535 and wavguide. That would give you some confusion in the middle of the mids. That and possibly not being time aligned.

Have you measured the TAD in ur system??

And what is ur xover?

Consider biamping... :D
 
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Scott L

Member
Paid Member
2008-12-27 12:32 pm
Knoxville, TN
I think you want to look at your signal chain and amplification.

The SA8535 is going to be like an open window to the rest of your system imo... the advantage of biamping is that you can eliminate the resistive padding on the 8535. IF ur not padding it, then it's a bit hot compared to the 1201. Also with the waveguide you have a bump up before the low freq rolloff, so it's a good idea to compensate for that.

One way to do that is with a series inductor since the rise looks much like a 6db/oct slope out to ~7kHz. So, the key would be to measure it, and size the inductor just right to achieve the closest to flat response possible. Another option to do that is with a slightly too large inductor paralleled with a suitably chosen resistor... that may not work properly for this, but it may turn out to be a better compromise. (gotta check and measure)

Without the waveguide it is flattest.

The other question is the slope ur using, that changes the way that the two drivers merge, and where the idea placement is for the tweeter, front to back, WRT the 1201.

I'd think the aerogel is not going to keep up with these two drivers nor is it needed as there is ample overlap between the 1201 and the 8535.

I suspect what you are hearing is the extra energy from the overlap + the rise in the 8535 and wavguide. That would give you some confusion in the middle of the mids. That and possibly not being time aligned.

Have you measured the TAD in ur system??

And what is ur xover?

Consider biamping... :D

The TAD/SA is part of a 4 way system. All active crossovers; Marchand 48 db/oct slopes main, and Audio Control 24/db/oct bass/ mid-bass.
Right now: 60/250/3.5K.
Pre-amp is a custom built tubed line stage. Mid-bass amps right now are HK Citation 12's. Mid-range amps are Levinson ML-2's, highs are also a custom triode tube amp.

For fun, I started measuring the TAD's once. Pretty well flat except for a rise at around 500 Hz. The sound quality is superb, by only small gripe (or quibble)
is that, to me, that 60 gram cone can't keep up at the upper end range of where I am using them. My EV HR9040/DH 1506 combination sounded much better. The thing with that set up was, I couldn't get lower than 500Hz, and my midbass does not like to go much above 250, and that's stretching it.
** In the next few weeks, I am going to build a different mid-bass, and possibly load the 1201's in a different enclosure. Oh, by the way, I have a
2.2 uF REL-CAP in series with the ribbons to compensate for the rise as it decends downwards. I had never thought about removing the waveguides as I always liked the directivity they provide. Perhaps I should re-think that possibility.
Bear, as always, good communicating with you. Besides us, I only know of one more SA 8535 user. The new trend is the Beyma TPL-150. I've never heard one, but the concept is the same.
 
Well I wrote a longish reply, but then my "token expired", whatever that is, and the reply went into internet outerspace where it orbits the planet glog for the next several hundred thousand years...

My thought is that you are having an issue with the area where the two drivers meet +/- and octave or so.

I'd suggest you measure. You may have matched the levels at the xover ok, but that may or may not be in a flat response situation. If the 1201 is rising then gets cut at 48db/oct and you splice in the SA, you may or may not have what you think ur getting overall.

The other thought is that 3kHz is too high. I'd go down to ~2khz +/-. Maybe even a little lower... maybe.

The tube amplification sounds good to me. The ML-2 was known to be a smooth amp, whooo...

That ought to sound very good. Even a rather average mic will tell you a whole lot about what is going on *between* the two drivers in the midrange and low highs. So no need for a measurement mic to get in the park, and pretty close.

Did I say that you may or may not be physically aligned front - back for the tweeter WRT the midrange?

Impulse response shows that quickly - especially if you can see the pulse in near realtime. The old IMP would do that trick nicely. Not sure about the newer toys.

etc...

_-_-

Gee, I said "series inductor" earlier - not getting enough sleep at all. NOT a series inductor! Series cap is correct.
oops. Sized properly.
 
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