Diaphragms replacement and the sensitivity variousness.

[HiFiPlayer]

I have some drivers want to replace to be match DCR.

A.) a pair of 808-8A planning to replace with matched aluminum 16 ohms coils.

B.) a pair of 291-16A (symbiotic) planning to replace with matched aluminum 16 ohms coils.

C.) a pair of 288B (original but mismatch DCR) also planning to replace with matched aluminum 16 ohms coils too.

The expected questions of below:-

1.) Does GPA always selling matched pair of coils?

2.) If I replace aluminum to instead symbiotic, for example, my 291-16A (symbiotic 16 ohms) replaced with GPA?s aluminum 16 ohms. Who knows that how many db would be increases or decrease? Or .. just to guess by myself with no spec.

3.) Similarly question, my 808-8A (symbiotic 8 ohms) to replaced with GPA?s aluminum 16 ohms. Are those equal to the 802D? Other hand, can it extend the frequency response from 20kHz became to 22kHz? The sensitivity will be increases or decrease.

Does anyone or VOTT/Hi-End enthusiasts have similar experienced can share?

Thanks for look and reply.

HiFiPlayer

[joyspring]

To answer your questions:

1. I'm sure the quality control at GPA is
fine. Unit-to-unit variance is usually
small - it's lot-to-lot variance that I'd
be concerned with... (see below)

2 and 3. It may be safe to assume that the
magnetic structure and voice coil gap
geometry may be identical in a series
(i.e. - 288, 290, 291) but then there's
the question of sensitivity.

If you can ascertain whether the voice
coil gap length and magnetic flux density
are identical within the series, then
it is reasonable to expect (as an example)
288 performance from a 291 fitted with an
all aluminium diaphragm.

Also remember:

Without a response curve (particularly a
plane wave measurement, which is the only
way to isolate the driver), you cannot
really make a judgement; specification
quotes from a tear sheet are not very
meaningful.




Here's some advice (assuming L/R stereophonic pairs):

1. Always replace diaphragms in pairs.

2. Always recone in pairs.

3. When having service performed, always have
the magnetic structure inspected for
shift or other damage.

4. Always have the voice coil gaps cleaned.

5. For Alnico drivers, always have the magnets
recharged. Particularly for Alnico cone
LF drivers, it only takes one `needle
drop' to kill mid-band sensitivity in one
or both drivers in a stereophonic pair.

Many shops only replace diaphragms or cones but cannot recharge magnets. Always inquire before using any particular service facility.

BobR

[Steve Burger]

I would not rule out pascalite as an alternative to the symbiotik diaphragms.

[HiFiPlayer]

BobR

Thanks for your clearly explanation. I have got your picture.

I think that the GPA?s manufacture diaphragms would more reliable than other non-geniuses. Cause I very sicken of Ti diaphragms that since from ?80 (The speaker?s model of 250Ti, diaphragms with a diamond pattern). Those HF sound makes me feel that my ears so pain.

[HiFiPlayer]

Steve

I agreed your idea is good. But we have no other choice in this era. Cause many original parts were discontinued, so the better choice is to find a quality one to instead if you have a pair of mismatch coils or those need to replace.

I believe that you will have similarly encounter in the future.