On a seasonally adjusted basis, Q3 was 14% better than Q2, down 11% versus 25%.
In addition, we saw sequential improvement within the quarter, as daily Mineral Fiber sales improved from down 15% in July to down 11% in September.
Overall, sales of $247 million were down 11% a quarter versus prior year.
Volume was down 10% and Mineral Fiber AUV was slightly negative.
Adjusted EBITDA in the quarter of $92 million was down 19% from 2019.
Despite the challenges in the market, our strong cash flow performance continues, and we remain on track to deliver over $200 million in adjusted free cash flow.
Based on this continued strong cash flow generation and our confidence to continue to do so, our Board has approved a 5% increase in our regular quarterly dividend to $0.21 per share and we are restarting our share repurchase program.
The previously discussed, acquisition of Chicago-based Turf Design, the leading provider of custom felt-based ceilings and walls and then on August 24, we acquired Moz Designs.
Beginning on slide 4, for our overall third quarter results, sales of $246 million were down 11% versus prior year, a significant sequential improvement from the second quarter when year-over-year sales were down 25%.
Adjusted EBITDA fell 19% and margins contracted 370 basis points, again a substantial sequential improvement from the second quarter when year-over-year EBITDA was down 36% and margins contracted 590 basis points.
Adjusted diluted earnings per share of $1.07, fell 22% and adjusted free cash flow declined by $53 million versus the prior year.
Our cash balance at quarter-end was $139 million, and coupled with $315 million of availability on our revolver, positions us with $454 million of available liquidity, down $33 million from last quarter as we completed the Turf and Moz acquisitions during this past quarter, and down $24 million from the third quarter of 2019.
Net debt of $542 million is $4 million higher than last year as a result of our acquisitions, partially offset by cash earnings and the receipt of $19 million from the sale of our Qingpu plant in China, which was idled.
As of the quarter-end, our net debt to EBITDA ratio was 1.5 times versus 1.6 times last year as calculated under the terms of our credit agreement.
Our covenant threshold is 3.75 times, so we have considerable headroom in this measure.
Since the inception of the repurchase program, we've bought back 9.6 million shares at a cost of $596 million for an average price of $62.13.
We currently have $604 million remaining under our share repurchase program, which now expires in December of 2023.
In the quarter, sales were down 14% versus prior year, but sequentially improved from the prior quarter when year-over-year sales declined 26%.
Adjusted EBITDA was down $20 million or 21% as the volume decline fell through to the bottom line and AUV was a drag.
Moving to Architectural Specialties segment on slide 6, sales were up 1% as the acquisitions of Turf and Moz contributed almost $8 million in the quarter and offset COVID-driven organic sales decline of 12% which were sequentially better than the 22% decline we experienced in the second quarter.
Cash flow from operations was down $48 million, largely driven by volume due to COVID-19.
Also in the quarter despite lower income in Q3 2020, we actually paid $14 million more in cash taxes than in the third quarter of 2019.
In the quarter, we applied a $27 million tax refund related to the sale of our international operations.
And we received $19 million from the sale of our closed Qingpu facility in China.
We have received an additional $2 million from the sale in October and this transaction is now complete.
As you can see sales were down 12%, adjusted EBITDA is down 18%, and adjusted free cash flow is down 16%.
We now anticipate full year revenues in the range of $920 million to $935 million or down 10% to 11%.
EBITDA will be in the range of $320 million to $330 million as the sales decline drops down and is partially offset by productivity and the impact of our cost containment actions.
Actions are in place to drive $40 million to $45 million of savings in manufacturing and SG&A down slightly by $5 million from our previous outlook as we invest for future growth.
92% of architects and designers surveyed said they are having conversations with their clients on how to make their spaces healthier and safer.
And it's a universally known fact that we spend 90% of our lives indoors.
I'm very pleased to introduce a new family of products called 24/7 Defend.
Our 24/7 Defend product family already includes infusion partitions and CleanAssure disinfectable products, which are proven cleanable products.
When placed in our standard grid system, AirAssure gasketed ceiling panels form a tight seal and reduce air flow leakage into the plenum by 300% over standard ceiling panels.
These new products are just the beginning of 24/7 Defend family as we have solutions in our innovation pipeline that we will add to this family in the coming quarters.

Summary:
Adjusted diluted earnings per share of $1.07, fell 22% and adjusted free cash flow declined by $53 million versus the prior year.
We now anticipate full year revenues in the range of $920 million to $935 million or down 10% to 11%.
EBITDA will be in the range of $320 million to $330 million as the sales decline drops down and is partially offset by productivity and the impact of our cost containment actions.