Dunlavy SC4 Speakers

This is all off the top of my head and time may have compromised my memory on all these particulars, but I seem to remember Dunlavy changing drivers (woofers?) and tweaking the cross-overs accordingly, on the SCIVs at one point. The SCIVAs are a different and better speaker altogether, and no the SCIVs can't be upgraded to SCIVAs. I'm not sure, but I don't think the "Signature" nomenclature really means anything.

Unsound. Is there any way to tell what woofers I have without taking one out? Are there any visual things to tell the two woofers apart?

Every model made by Dunlavy that carries the "SC" in it's name is "Signature". That's what the S stands for!
Dunlavy changed a few drivers on various models over the years but the only one significant enough, according to him, to warrant a different designation was the SC-IVa.
There was a change in the woofers of the IV before the SC-IVa came out, but it was hardly worth note. Of course, you will find many people who disagree with me regarding any performance changes but you'd be wise to take it with a pound of salt.
Bottom line..... All Dunlavy speakers are world class. Worrying about which "version" of a model you have is a waste of time.

It started with the original Dunlavy IV, then towards the end of that run John made improvements to this speaker. He did not make any designation changes, but simply referred to it as the Dunlavy IV improved version. Shortly after this, he made additional changes that could not revert back to the original SCIV and therefore named it the SCIVA.

It has been such a long time, my memory fades....I cannot remember if all three versions say Signature on them or not. Mine are the SCIV improved and does says Signature on them.

I'm sorry that I cannot remember more specifics on all of the three versions. What I can say is that any of the three are fantastic speakers. You seriously can not go wrong with any of them.

I'm not an authority on DAL models, but I did follow their progress because of owning Duntechs and my respect for John.

I thought all the DAL numbered (Roman style) models were preceded by SC. I don't remember that he produced a special line of Signature models.

The change from SC-IV to SC-IVa was the most significant upgrade. It was in response to a Stereophile review of the SC-IV which was favorable except for bass extension. That was likely the only time anyone criticized one of John's designs for lack of bass. The SC-IVa apparently did produce a more extended bass range.