3-way crossovers for Altecs

[joebelly]

Greetings all. (This is my first post)

I have to say that I am somewhat of a purest when it comes to audio. I prefer simple setups. I currently have a set of A7's that I built using red oak plywood and 16 ohm components from a pair of Valencias. They sound wonderful. I also have a pair of Infinity RS2B's that I have been using for quite a while. I switch them out for extended periods of time. On the last switch to the Altecs, I was disappointed with the high frequency response. Maybe my listening preferences are changing or my hearing is changing. It is not my front end because the highs are there with the Infinitys. The problem with the RS2Bs is that they have no mids like the A7s. So I was thinking... Either add a horn to the RS2Bs or a tweeter to the A7s. The RS2B mods are out of the question. There are to many panels to try and figure it out. I thought about using crossovers from La Scalas on the A7s but was told the would not work and not to waste my money by people in the know. The problem I for see is the 16 ohm drivers. I have yet to see a 16 ohm tweeter. How would the impedance differences blend?

So, the question is. Did Altec make any three way horn driven setups? Has anybody designed or tried crossovers to make A7s three way, even if they were not 16 ohms? If so, what tweeter was used?

Like I said, I like to keep it simple. If any body has any suggestions/criticisms, I would invite any reply. I am using a McCormack CD and pre amp and a VTL Compact 100 amp. I know that is a lot of power for the Altecs, but I need the power for the Infinitys.

Thanks,

Joe

[bowtie427ss]

Once upon a time i found myself in a very similar situation. Ultimately the cure came in a thread on this board. Altec hi frequency extension is a sublte thing, for lack of a better term, and the only flaw or problem was that i wasn't allowing myself enough time to adjust to how the altec horns and drivers make thier delivery. In the end i now realize that the altec's have an amazingly smooth and linear response at any spl.

I assume you're using genuine altec aluminum diaphragms?

I too attempted the addition of a tweeter (jbl 2405 slots) and for the most part managed to do nothing but muck things up. There is something wonderfully realistic about the A7's, and in my opinion and experience any kind of major mods to the original recipe seems to only degrade the end result.

The only mods that i've tried and kept are Solens in my networks, and the addition of hardwood stiffening ribs added to the box interior, added a 3rd brace behind the horn flares, closed off the back side of the horn flares to the box interior, and dampened the 511 cowbells, this time around with the dampening i've applied dynamat to the exterior of the horns, seems to work well.

Have you damped your horns?

That alone may improve your perceived HF response by eliminating some high midband resonances.

Are you using 804/806 driver bodies, or 802/808's?

The 802/808 will give you a couple db gain over the 804/806 without changing anything else. I've never done a side by side AB comparison, but am considering just that for a rainy weekend project.

If the space between my ears comes up with anything else, i'll post.

[gamalot]

I am with B427 on this one and not up to speed regarding 8/16 ohm possibilities.
I like the sound from the 802/808 with tangerine plugs better then the 806s.
Others here mess around between 500, 800, 1200Hz cross points and we all have our own opinions and likes/dislikes.
Some say the 511 horn sounds better then the 811 and most agree the diaphrams are the major key.
I have two sets of 802-8Gs with tangerine phase plugs in different speakers and with different horns. To be very honest, the highs from the model 15s with bent plastic horns are nicer then from the 19s with 811Bs. Smoother might be the correct terminology so some horn dampening is on the list for a project in the near future.
I am gathering the stuff to build another pair this winter and might use the 511 horn this time to hear for myself.
All sorts of avenues for you to travel on in your search for audio nirvana and fortunately you have a good base to work with.

Gary

[joebelly]

Thanks B427 and Gary,

I have 416-z woofers and 811bs with 806As drivers. I am pretty sure I have the original diaphragms because the Valencias looked untouched and I have not done anything with them since. I do not know the crossover frequncey and would not know how to check. There are no markings or numbers on the XO. I have not dampened the horns. I think I will do this because when I increase the horn section to get a little more treble, the music starts to get blarey.

How do you specifically dampen the horns? What is Dynamat? I also failed to mention that the room they are in is very live sounding, wood floors, not much fabric, few curtains, etc. I am sure this adds to the blariness. I put down an area rug, but I do not know how much that helped. Do the 806A's hook up to the 511's?

Any way, I think the next step is to dampen the horn, so any advice would be appreciated.

Joe

[ngccglp]

Hi,

I had that feeling too when I first got the A7. I have since managed to add a 2405 to give that extra sparkle at the top without screwing things up. The trick is not to use too high a value for the cap. Many here recommends 1 uF which is too much. 0.1 to 0.2 uF will do just fine, it lets you still enjoy the authentic Altec sound and yet gives the extra extension at the top, very evident when listening to cymbals on jazz cds. If you tap the signal from the 802 terminals, be sure to reverse the polarity. That is eqivalent to a 3rd order Butterworth. Also align the voice coils vertically.

Try it and let us know your experience.

[sguttag]

Correct me if I'm wrong...the JBL 2405 follows JBL's historical polarity which is +Red will create a incoming wave instead of what the rest of the world (including Altec and even newer JBL) will do...that is +Red will create an outgoing wave.

Hence connecting the JBL out of phase with the Altec would make the most sense.

[ngccglp]

Hi Steve,

The convention for the 2405 is positive to red means compression as per most drivers. Because the N501 is a 2nd order butterworth, the 802 is connected in reverse order to the 416. But adding a cap changes the circuit to a 3rd order butterworth for the 2405, which means the connection should be in the same order as the 416 and reverse to the 802. I've done extensive listening and confirmed that this connection sounds best.

[bowtie427ss]

Dynamat is actually a trade name for a self adhesive sound deadening material. It was originally intended for use on metal panels to deaden them in car stereo installations. There are other similar products also available. You can also find some other very plausable suggestions in other threads on this board in regard to dampening the 511 and 811 horns.

You can get dynamat from parts express, my package is long gone, so i cannot tell you exactly which type i used. Maybe someone will chime in here with a specific suggestion, also their tech people are very good and i'm sure would recommend the best choice if you tell them the intended purpose.

[LICORNE]

If you want to put the high frequencies back in their place . Replace the inductors with Iron Core ones.

.................................................

[gamalot]

I always felt, when I owned Valencias, that the highs were too much in your face. You call it blairy.
When I bought my first 19s this problem was solved.
I think your Valencias are 800 Hz while the 19s went to 1200Hz and incorporated some filtering in the XO as well as both HF and MF adjustment L Pads.
I too plan to use Dynamat and will be adding a V shaped piece to both top and bottom of the horns behind the baffel. Others go to great lengths in dampening but I am not sold that this is at all necessary with horns that are securely mounted into a cabinet.
My thought is to make one change at a time and start with the least expensive and work up until you find the sound you want.

Gary