Whats Optimum when replacing 802D diaphragms with GPAs?????

[GM]

There seems to be a consensus that compression joints are better that soldered (the jury is still out for me)....... You can use these .........

It wouldn't be if you could see the UL/CSA tests. The differences aren't trivial. Even in high current, voltage bus bar systems, any cable connections are crimped [cold welded] to appropriately large surface area connectors before being bolted, properly torqued, then silver soldered [like used on high pressure systems] around the entire joint to keep the joint secure/vapor free over the decades of outdoor abuse.

Unfortunately, there's not much available at the sizes we're dealing with here except with fairly expensive, specialized crimping tools, lugs. For sure, the ones in your link much too large, wrong type.

GM

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How to get two GPA diaphragms to sound the same in my room ??

Is ANYONE replacing em in carefully / visually - chosen pairs, as was suggested I should do.

Well, the drivers must have closely matching magnetic fields, wiring, connectors, clean gaps and of course electrically, mechanically matching diaphragms, so pretty obvious just swapping one diaphragm is not going to be a perfectly matched pair unless it's from the same batch and little time is on the other original.

Unless one pays a premium, I'd be surprised if GPA verifies anything beyond checking its Dcr before shipment, so doubt anyone [them or buyers] is going through their inventory to 'carefully / visually - chosen pairs' on every order.

Over time, alum. work hardens [gets brittle], but doubt with your low power would audibly change them [for most folks anyway] even if driven continuously for 36 mos., so without being there to measure a few things and actually hear any differences, I can only recommend sending both drivers back to GPA for another restoration.

GM

[LowOhms]

Hi all,

GM said

" I can only recommend sending both drivers back to GPA for another restoration.

GM "


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Thanks,

I tend to concur with you.

Both 802 bodies will fit in a USPS Medium Flat Rate box, bolted to 1/2 inch plywood, so its only about $13.60 each way.

I will ASK Bill H in advance, IF GPA could be paid extra, for their time, to go over these as GOOD as GPA can, and try to get a time / labor price IF he is willing to do this, and quote it to me up-front.

He may accommodate this, as a not-too-often-made request.

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Next ..... folks,....... two additional "speaker newbie " questions :


(Q1) Will the 8 Ohm diaphragms have a better transient response, than 16 Ohm ones, due to less wire on the device ?? Should I order them instaed of 16 Ohms. ( 515B bottom driver ).


(Q2 ) Would I just have to change the L/C values on my 16 Ohm 12 DB DIY Butterworth VOTT crossovers, to accommodate the 8 Ohm 802Ds, IF I change to them??

( Amps are 3 Watt monaural 2A3 SETs, DC coupled. )


Well, thanks to any and all who TRY to help. Most appreciated.


These VOTTs, and a new DC monaural 2A3 amp circuit ( ' DIY building ), is where I intend to stay ............. in audio listening.


Low Ohms, ..... Jeff Medwin

[mah]

Are the diaphragms available in a 16 ohm version? Store - Great Plains Audio

Only 8 ohms stated in the brochure.


I just noticed an authentic vintage Altec touch - the smudged part number.

I wonder if Bill will make the 23744 Lites?

[GM]

Thanks,

(Q1) Will the 8 Ohm diaphragms have a better transient response, than 16 Ohm ones, due to less wire on the device ?? Should I order them instaed of 16 Ohms. ( 515B bottom driver ).


(Q2 ) Would I just have to change the L/C values on my 16 Ohm 12 DB DIY Butterworth VOTT crossovers, to accommodate the 8 Ohm 802Ds, IF I change to them??

( Amps are 3 Watt monaural 2A3 SETs, DC coupled. )

You're welcome!

Ask Bill since I don't know what Altec did, but normally an 8 ohm will have fewer turns of bigger wire to keep moving mass [Mms] the same.

Your 2A3 is designed for 16 ohms, so assume it's not designed for the higher current required.

Right, just double the hi-pass [C] and reduce [L] by half.

GM

[Elitopus1]

Both 802 bodies will fit in a USPS Medium Flat Rate box, bolted to 1/2 inch plywood, so its only about $13.60 each way.

This is good info. I forgot they made this "bigger" medium flat rate box. Is there room for a good amount of padding on top of the drivers?

[horndawg]

Hi all,




(Q1) Will the 8 Ohm diaphragms have a better transient response, than 16 Ohm ones, due to less wire on the device ?? Should I order them instaed of 16 Ohms. ( 515B bottom driver ).


(Q2 ) Would I just have to change the L/C values on my 16 Ohm 12 DB DIY Butterworth VOTT crossovers, to accommodate the 8 Ohm 802Ds, IF I change to them??

In going from 16 to 8 Ohm drivers you'll need to double the capacitor values and halve the inductor values. Additionally, as a rule of thumb (not always the case) and while all things being equal, transformer performance should be a bit better through the 16 Ohm tap - at least in theory.

[LowOhms]

This is good info. I forgot they made this "bigger" medium flat rate box. Is there room for a good amount of padding on top of the drivers?

Enough padding ??? "I" think so. I use "blueboard" insulation from Lowes, but one could also cut to size cardboard boxes, and re-use that, for just some labor cost.

I've done it twice, no problems E1.

But, as I THINK more about it, after rebuild and GPA re-magnetization, TO BE SAFE, one may want to use the USPS box ONLY as an INSIDE box, ( in a double-box pack job ) so as to further minimize chances for shipping shocks to the rebuilt drivers' magnet structures.


Jeff

[mah]

8ohm vs 16ohm 802 transient response.

Force on the voice coil F = number wire turns in the coil N x current i. F=Ni.

For the same power, as you increase the current and the coil wire-thickness(reducing resistance from 16ohms to 8ohms) the number of coils and the wire length will decrease in the same proportion. Thus the volume of wire remains the same and, accordingly, the coil mass is the same.

The transient driving force is therefore the same. F=Ma. F and M unchanged means cone acceleration,
a, is unchanged.

[LowOhms]

8ohm vs 16ohm 802 transient response.

Force on the voice coil F = number wire turns in the coil N x current i. F=Ni.

For the same power, as you increase the current and the coil wire-thickness(reducing resistance from 16ohms to 8ohms) the number of coils and the wire length will decrease in the same proportion. Thus the volume of wire remains the same and, accordingly, the coil mass is the same.

The transient driving force is therefore the same. F=Ma. F and M unchanged means cone acceleration,
a, is unchanged.

Lovely mah, But I seem to remember you also "proving" that speaker wire size makes no audible difference also, months ago !!

Pretty funny similarity, eh.... for me to remind you, and others, of !! Peace,

I am NOT trying to pick a fight, so roll with it PLEASE.

I will figure out what to do. What may prove to be one thing in theory, does not mean it is so in the real world, UNLESS the theory was ALL encompassing, which "I" think, it seldom is.

Dick Sequerra ( sp ) once was interviewed and discussed how VERY few EEs knew how to make good sounding audio equipment, I THINK it was amps, BECAUSE of their training. I will TRY to find that interview and post it, my office mate brought it to my attention, a few days ago, and says he will LOOK for the interview. It was written after Saul Marantz died, I think the Absolute Sound did the interview. Stay tuned.

Regards and THANKS for the post, "proof", ' loved it !!! I think we understand each other better by now. I wish you no ill-will !! Can you laugh at yourself ???,..... I can ( and do ) laugh at me !!

Jeff Medwin.....Low Ohms



mah,

BTW, what do you think of 440 VDC potentially sitting on the Finals, the plate ( Ea) of Wojo's Chinese BEZ "2A3" amp, when the 2A3 is in self-bias ??? No one, but me, has brought that up to check-for. It is typically 295 to 300 VDC Ea, assuming 250 VDC P-K and 45 or 50 VDC of self-bias.

[mah]

Jeff, you are on the wrong forum. What nonsense!