Here is what the email said:

Save 10% on your entire on-line purchase!

BLACKFRIDAY3

Valid ONLY from midnight on 11/28/19 to midnight on 11/29/19
Offer applies to online purchases only.
To use the code, just type it into the coupon box of the shopping cart and hit re-calculate to see it applied to your total. NOTE: The code will only work during the specified 24 hour period. The clock is set by Eastern Standard Time Zone.

This is a one day only sale. Regrettably, since we have such a long waiting list for amplifiers it is impossible for us to apply this coupon to existing orders. If you have an item on order that we haven't pulled parts for yet, you can cancel it and place a new order on Black Friday with the coupon at the expense of losing your spot in line.

Also, of note - this is the second year we have had a 10% off everything sale on Black Friday. Last year we sold 81 amplifiers and or pairs of speakers during that 24 hour period. Our average build sheet ranges between 50 and 100 orders at any given time, with a 9 to12 week average wait. Last year our list was at about 80 prior to the sale. The next day it was at 160. That means that the people who used the coupon first thing in the morning had close to a 12 week wait, while people who used the coupon last thing that evening had a 22 week wait. All orders are entered by the date and time of day the order was placed.