604C Thiele Parameters and Cabinets

[ejfud]

My rebuilt 604C's are on there way back from GP with a full rebuild. Now it's time for cabinets.

As much as I'd like to hear them in the Stonehenge V cabinets, They will be just to big for my listening room. 4-5 cubic feet would be much more doable. My room reinforces bass so I'd like to tune them higher as well.

I found some info from a post back in '04 about the Altec Technical Letter No. 281 which states

"All 604 models are well behaved, even when mounted in rather small enclosures. The most efficient enclosure for any 604 is 6.5 cubic feet, tuned to 40 Hz. Here are a few tuning suggestions:
3.0 cu. ft. tuned to 50Hz -- 2 ducts; 3" dia. x 3.6" long,
4.0 cu. ft. tuned to 45Hz -- 2 ducts; 3" dia. x 3" long,
5.0 cu. ft. tuned to 40Hz -- 2 ducts; 3" dia. x 3" long,
6.5 cu. ft. tuned to 40Hz -- 2 ducts; 3" dia. x 1.4" long"

Do these seem realistic?

With no way to measure my drivers, would the parameters now that they have been reconed, be close to the parameters for the 604E?

Any help would be appreciated.

Gary

[electrovice1]

Hi Gary

Our paths have crossed before on another forum.

Have you considered (or should that be konsidered) a Karlson cabinet. The 604C was one of the drivers often used in the cabinet. I just found a Karlson with a 604C at an estate sale. The cabinet seems almost small when it is placed next to my not quite completed Stonehenge V clones. I have enjoyed listening to the Karlson/604C combo.

John

[GM]

FYI, for a given Vb you either tune a cab lower to blend into a room or the more common way is to reduce Vb for a given Fb.

They are all valid alignments, though whether any suits your room, personal preferences is impossible to say plus if driven with a high output impedance amp it would change their response due to effectively increasing Qts.

Don't have a clue about specs, you'll have to ask Bill if he uses the same kit for all 604s and how it may affect its specs in different motor/frame combos.

Bottom line, with no specs, I recommend building the biggest cab you can tolerate and experiment with different tunings in-room with the HF disconnected to find the most tonally balanced (flattest) sound, then set the HF's level to match and if the highs sound too rolled off, adding a by-pass cap around the attenuator will help, though a pain to do unless you either mount the XOs externally or in their own sealed compartment so that you don't have to worry about air leaks. That, or drive the HF with a high output impedance SET amp with a variable DF (bass boost) control.

GM

[martyh45]

Hi, all you need is one of these to measure the woofers.WT3
The one hundred dollar investment is small compared to the sweat and money that goes into building a good pair of cabinets.

If you can measure them and enter the parameters into a freeware program like winIsd pro you can see some of the tradeoffs involved in going with a smaller cabinet tuned high. One thing to do is look at the cone excursion at lower frequencies in whichever alignment you choose keeping in mind that pushing underhung motors beyond x-max makes for rapidly rising distortion.

[ejfud]

Thanks for the replies.

GM, that's what I thought I may have to do. Thanks for reassuring me.

I'm a Mac user, so WT3 is not an option unfortunately. Sounds like a great idea though.