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speaker driver matching

The Captain

The Captain

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Hi, following from my ebay muppetry of paying top dollar for minstrels with one sick driver (now firmly established :rolleyes:) I see two numbers and 'minstrel' written in marker-pen on rear '37' and '11.75' (other ok driver is 37 and 11.95).

Can anyone shed any light on these, or know (specifically if I get lucky with a spare driver) if I need to "match" or something with these no's in mind?

cheers Capt
 
I'm gonna bump this! ^^ I wonder if the '37' could refer to a batch no, the '11.75' could that be ohms from one driver terminal to other/ across voicecoil?

on another note: I want to try swapping the 3uf 'lytic capacitor in the x-over (the only cap) to make certain this is not cause of the distortion I'm getting in the bass driver (only in its high registers). 3uf lytics seem rare: can I try a 3u3 supersound for this test ok?

thanks for any thoughts- capt
 
3u3 should be fine, at least for a quick check. The tolerance most 'lytics is more like 20%, so 3.3 is still inside the possible range of the original part.

If it fixes it, get 2.7uf and 0.33uF or 2.2uF and 0.82uF, as these are standard values. You might as well pop cheap and cheerful film caps of some sort in once you source a replacement woofer.

You can test your interpretation of the 11.75 number with a DVM on the Ohms scale. Just remember to connect the probes together, and subtract that as, the test leads will be a fraction of an Ohm. I am surprised if the voice coil resistance is so high, unless the Minstrel is 16Ohm nominal speaker?
 
thanks PD- I'd just spoken to Phonography (amazingly helpful) before posting #2 re a spare driver (no can do) but he said, maybe, a leaky cap could be the prob so I may as well check.

Summat in me noggin tells me the bass unit is being given HF stuff its not meant to go up to, & spits it out as raspy distortion: but that could well be baloney..

Is it safe, in your estimation, to assume the (only) inductor can be ruled out as cause? or how does one test an inductor is ok?
 
Inductor unlikely to fail. If it fails it will look charred and black.

If inductor has reasonably low resistance (say less than 1Ohm) it is OK.

If the crossover has one inductor, and one cap, then almost certainly, cap is in path to tweeter, and inductor in path to woofer. There might also be some level setting resistors in and around tweeter circuit.
 
Yes one cap, one inductor, unless there's an r/c behind the tweeter far top of cab I can't see..

so I therefore assume that rules out the cap as having any bearing on the bass unit prob/ not much point redoing it?
 
Quick test - just disconnect the cap at one end . Tweeter should go silent. Now listen to woofer.

Of course cap may have a problem as well, but cross that bridge when you come to it.
 
great help PD that makes perfect sense.

Last Q if I may: in your opinion, should another minstrel driver drop-in ok? ie maybe I'm worrying unneccessarily about '37's and '11.95's, and as long as its an exact same type unit- I should be ok shouldn't I?
 
I would hope so.

My understanding is that when most manufacturers make a batch of speakers, they sort the drivers into pairs that are as similar as possible, often just on the basis of DC resistance - they have to choose somehow, and this is a really fast measurement. But generally, most drivers made to the same basic design should be interchangeable.

You might not get quite such perfect stereo imaging as with the matched item, but in reality, unit to unit variations are at the 1dB level (or less) for many drivers - see the measurements on the Zaph audio site for examples. A quick tweak of the balance control should sort that out, if you even notice it.
 
just the info I need- many thanks PD. I have redone a heybrook HB1 driver before, without a 2nd thought & that was spot-on.. so fingers crossed, if I get lucky with one, it should drop-in. cheers capt.
 
Was it easy to get the driver out without trashing the foam stuff that surrounds the tweeter? I may be tempted to open mine up if it doesn't do too much damage.
 
yes if you're careful: its a very strong adhesive, so v gently dig under the bit over the driver and peel back a tad, prize driver out- but it'll still stick to driver rim so could tear if v unlucky. It'll reform enough so will barely show/ not at all once all put back. Its not very interesting inside tho: I'd be tempted only if need be.
 
well.. yes.. ideally the tweeter needs to come out to get at the x-over as its almost right behind it with tight wadding too, so tweeter foam redo to complete job properly.. so.. an arse.

I got 7.2 Ohms across the driver voicecoil (so '11.75' obviously bugger all to do with ohms!)
 
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