The parts of my new Altecs

[Zilch]

From what I've always done with ported cabinets, the larger diameter the port (within reason) is better because there is less port noise. Is that a safe assumption with these?

Generally, yes, but even 3" is large enough for these, since there's a pair of them.

School me. What's an LR baffle step filter? Got a link to what I'd need to build to do that? Can you graph the response results with that filter attached?

I shouldn't have used the word "baffle," because that's not the issue here. It's a step/shelf filter comprising an inductor in parallel with a resistor, the combination in series with the driver.

The intent is to level the rising response of the woofer, if that's real. Somebody's going to have to measure to determine the actual performance of 416-8Z in that box size and tuning. A notch filter may be required instead, one more component. You give up woofer sensitivity to acieve flattened response, but there's a sense in which that sensitivity is illusory, anyway, since it is peaking in the lower midrange and not balanced with the available lowest frequencies.

See Dickason 7.70, "Contouring Filters."

 

[spartanmanor]

I'm using the 15ga Jantzen coils on the low pass, the 18ga for the high pass and the Dayton Poly caps. Here is a list of the parts.

2) 255-428 Jantzen 1.8mh 15awg air core coils @ $19.26 ea
2) 255-264 Jantzen 1.8mh 18awg air core coils @ $9.44
4) 027-421 Dayton 4uf Poly caps @ $1.85 each (need 2 per side paralleled to = 8uf)
2) 027-436 Dayton 20uf Poly caps @ $4.95 ea
2) 027-410 Dayton 1uf Poly caps @ $1.15 ea
(I'm running one of each of the above caps in parallel to = 21uf)
2) 260-625 100 watt mono L-pad 8ohm w/1" shaft @ $9.95 ea

Total all parts = $96.90. I'm ordering some other things (can of Deoxit since it's on sale) so the order is over $100 for free freight. I needed to get some caps, etc for a Magnavox tube amp that I'm going to tinker with on these speakers for awhile.

I'll update with pictures and progress when the parts start rolling in or if I'm working on something else on them.

Cool! What are you planing on using for mounting these onto?

In the meantime I have gotten both the fronts off of my Valencias and am doing the cabinet work. :thmbsp: I notice in your photos a shelf between the woofer and horn mine does not have one but there is evidence that one may have existed, any ideas?

 

[spartanmanor]

And here are the tuning calcs.

Altec called these boxes 5.7 cuft without a recessed horn.

Spartan's measurements say deduct 0.142 cuft for the recess.

Altec says deduct 0.19 + 0.023 = 0.213 cuft for the horn and driver, respectively.

The BB6P software deducts for driver displacement. I called the woofers front mounted, i.e., to the front of the baffle, and the gross internal volume 5.56 cuft.


Valencia with 816-8C woofer, red curve:

Tune to 33.23 Hz using two 4" ducts @ 5.037" long; F3 = 51.40 Hz, F10 = 31.63 Hz, or,

to 33.01 Hz using two 3" ducts @ 3.307" long; F3 = 51.81 Hz, F10 = 31.40 Hz.


Milano with 816-8Z woofer, blue curve:

Tune to 36.28 Hz using two 4" ducts @ 5.037" long; F3 = 185.5 Hz, F10 = 45.62 Hz, or,

to 36.11 Hz using two 3" ducts @ 1.926" long; F3 = 185.7 Hz, F10 = 45.62 Hz.


Notes:

1) Altec used two 4.25" ducts @ 6.25" long in 846B Valencia as measured by LHF member VTUBE6, which tune the cabinet to 35.99 Hz.

2) Vent velocities are under 10.5 m/sec with either duct diameter, well within acceptable limits.

3) All sims calculated using "Normal" fiberglass damping.

4) 416-8A/Z T/S parameters do not appear to be published anywhere; I used those measured by an Altec Forum member.

5) If that's how 416-8Z actually behaves above 100 Hz, I'd be giving up 6 dB of sensitivity there and using an LR step filter on the woofer to provide better low bass response. Stock Altecs using that driver in this size box are reputed to be "Bass shy," and this curve may illustrate the reason.

Thanks Zilch! I am planning on getting my fronts rebuilt on Thanksgiving when I can take advantage of my Fathers woodshop. :thmbsp:

 

[Zilch]

No shelf shown in the Altec Valencia 846A plans:

http://www.lansingheritage.org/images/altec/plans/1968-enclosure/page10.jpg

 

[avguytx]

Cool! What are you planing on using for mounting these onto?

In the meantime I have gotten both the fronts off of my Valencias and am doing the cabinet work. :thmbsp: I notice in your photos a shelf between the woofer and horn mine does not have one but there is evidence that one may have existed, any ideas?

I'm going to make a 6" X 6" panel (or so) out of 1/4" MDF and mount it to the back removable wall of the cabinet and space it off a 1/4" or so. I have a couple of terminal strips around here to mount on it as well to make things easier for wiring. It'll be a fun projects...parts are on the way!

I honestly can't remember if the Valencia's I had used a shelf or not but it seems like they did. I don't have any good pictures of the insides of them...just outside shots and closeups of the crossover, drivers, etc.

 

[Zilch]

Crossover building tips here:

http://www.partsexpress.com/resources.cfm

Can't say I'm real excited by the one they built on cardboard, tho... :

Earlier subject: Baffle step compensation illustrated here, near the bottom:

http://www.partsexpress.com/resources/crossover-help.cfm

Really need measurement capability to do the design stuff.... :yes:

 

[geaugafletcher]

Zilch, do you think moving the pair of Valencia drivers to a cabinet with a narrower front baffle necessitates baffle step compensation? Could that be a less-important but present cause of the Valencia's "gentle" bass response?

 

[Zilch]

Zilch, do you think moving the pair of Valencia drivers to a cabinet with a narrower front baffle necessitates baffle step compensation? Could that be a less-important but present cause of the Valencia's "gentle" bass response?

It seems to be more of an issue with the small full-range driver transmission line group; I've never seen it as a problem in the bigger cabs I normally deal with. I do see LF drivers with rising response, but that's normally managed in other ways via the LF filter, i.e., non-textbook transfer functions and Zobels.

Measuring LF response accurately is difficult, and as soon as you put the speaker in a room, some bets are off. Sometimes just setting them against a wall, like most of us typically use speakers, changes the picture substantially, with boundary reinforcement rendering certain issues moot. However, I've measured enough now to recognize certain common response anomalies, and dealing with them often improves the performance.

With respect to Valencia, I just don't know whether the response characteristics shown in the box-modeling simulations are actual or not. I'm using T/S parameters for 416-8A/Z as measured by a third party; there don't appear to be any "official" ones published anywhere. BB6P does a mathematical consistency check on the parameters as entered, and did not find any problems with these.

I've studied the Valencia HF situation over the course of nearly a year now, and my findings are well known. Somebody else is going to have to do the LF. I simply don't understand the prior work on that by others. Perhaps someone such as Gordon or Ray can translate Moldy's "That Field's Been Picked" post; it's outside my frame of reference:

http://audioheritage.org/vbulletin/showpost.php?p=163019&postcount=633

There's likely more info on the Altec Forum if anyone desires to research the subject.

Edit: Well, I DO think I understand the "... tune by damping the in-box impedance peak" part, as I have an Altec tech note describing an old vented-box tuning method used before T/S parameters in which the "optimum" tuning was chosen to be that which produced equal-height resonance peaks for both driver and port. I've never tried that, but I've certainly measured many stock alignments which do not conform.... :yes:

 

[geaugafletcher]

Thanks for the info and the link! Sounds like "GM" uses some old-fashioned terminology, makes his post somewhat impenetrable.

 

[Zilch]

He's apparently somewhat of a respected authority on this, and if an interested AKer who's also a member of the Altec forum were to invite him to do so, he might come over and tell us something about 416-8Z in Valencia-size cabinets.... :yes:

 

[similost]

I can't believe a pair of "JBL" speakers has brought this much info outta the woodwork... Damn David.. now you're making me wished I would have seen them first :

Oh well.. I'm hoping to have some BIG altecs soon

 

[spartanmanor]

I can't believe a pair of "JBL" speakers has brought this much info outta the woodwork... Damn David.. now you're making me wished I would have seen them first :

Oh well.. I'm hoping to have some BIG altecs soon

You will probably be listing to yours before I get mine back together. It does look like a fun project though. :thmbsp:

 

[similost]

Well.. we'll have to see.. I've got a line on two different pairs.. and going to probably pick up a single supposed "A7" this weekend.. hopefully something will happen before long... I'm wanting the A5's for sale on e-bay.. but MAN OH MAN are they gonna cost me if I do get them.. and probably more than just money.....

I guess our ideas of fun projects are differnet to.. I sure do love plug and play

 

[Ballylongford]

Cabinets?

Too bad you're not closer to the west coast. I know where a pair of empty 846b Valancia's could be had rather cheap.:yes: Brad

Not to hijack this thread, but I am in the San Jose CA area and am interested in the cabinets. more info?

Thanks

 

[Zilch]

A CL listing in Oregon long gone now, apparently....

 

[Zilch]

N800-8K Crossovers

Constructed per Avguytex's parts list and specs, above.

Boards are 4" x 6".

Remove 3 turns from the large inductor and 4.5 turns from the small one for 1.75 mH each.

Schematic here:

http://audiokarma.org/forums/showthread.php?p=1426438#post1426438

[Yeah, mirror-imaged.... : ]

 

[spartanmanor]

Constructed per Avguytex's parts list and specs, above.

Boards are 4" x 6".

Remove 3 turns from the large inductor and 4.5 turns from the small one for 1.75 mH each.

Schematic here:

http://audiokarma.org/forums/showthread.php?p=1426438#post1426438

[Yeah, mirror-imaged.... : ]

Very clean build! Thanks for posting.

I am now thinking of going with electronic crossovers and bi-amping. Does anyone see a problem with going this route with the current 16ohm horns and 8 ohm woofers? :scratch2:

 

[similost]

Very clean build! Thanks for posting.

I am now thinking of going with electronic crossovers and bi-amping. Does anyone see a problem with going this route with the current 16ohm horns and 8 ohm woofers? :scratch2:

I think you would probably be happier with the sound of an active cross than a passive. I really do like the way you can adjust the sound out. As far as I know you shouldn't have a problem with 16ohm on a crossover.. I had mine running with the same load on one channel for a bit.. seemed to take it just fine..

Once I can get me another cab built, I'll be tri-amping, and running a couple of 16 ohms... I just found another 803a speaker this morning.. hope I can score it.. then all I need it one horn and driver...

 

[spartanmanor]

I think you would probably be happier with the sound of an active cross than a passive. I really do like the way you can adjust the sound out. As far as I know you shouldn't have a problem with 16ohm on a crossover.. I had mine running with the same load on one channel for a bit.. seemed to take it just fine..

Once I can get me another cab built, I'll be tri-amping, and running a couple of 16 ohms... I just found another 803a speaker this morning.. hope I can score it.. then all I need it one horn and driver...

What are you using for an electronic crossover? Excellent on the 803a wtg!

 

[similost]

What are you using for an electronic crossover? Excellent on the 803a wtg!

I might get the 803.. gotta watch the price.. still a week on it ... hopefully some korean won't want it worse than me...

I've got a 2 way peavey VSX.. it's a little older, but it sure does a great job, and sounds nice... If I can get this other cab, and the speakers I need, I'll probably be offing the VSX, and getting a behringer 3way.. I'd rather bi-amp the altecs, and then add a 3rd bass amp.. I should have some nice amps to do this all with... use a crown d-150 for the horns, an EV 2600 (rebadged altec 9444) for the 803's.. then my Tapco on the subs..

of course this is all speculative on actually aquiring an 803a.. them puppies are rare..