Condensed Consolidated Statements of Operations - USD ($)	3 Months Ended
	Oct. 31, 2021	Oct. 31, 2020
Income Statement [Abstract]
Net sales	$ 116,759,000	$ 135,218,000
Cost of sales	75,024,000	85,010,000
Gross profit	41,735,000	50,208,000
Expenses:
Selling, general and administrative	28,242,000	27,540,000
Research and development	12,497,000	11,635,000
Amortization of intangibles	5,349,000	5,566,000
Proxy solicitation costs	2,162,000	0
Acquisition plan expenses	0	91,183,000
Total operating expenses	48,250,000	135,924,000
Operating loss	(6,515,000)	(85,716,000)
Other expenses (income):
Interest expense	1,607,000	2,297,000
Interest (income) and other	219,000	66,000
Change in fair value of convertible preferred stock purchase option liability	(304,000)	0
Loss before benefit from income taxes	(8,037,000)	(88,079,000)
Benefit from income taxes	(2,053,000)	(2,239,000)
Net loss	(5,984,000)	(85,840,000)
Convertible preferred stock issuance costs	(4,007,000)	0
Establishment of initial convertible preferred stock purchase option liability	(1,005,000)	0
Dividend on convertible preferred stock	(235,000)	0
Net loss attributable to common stockholders	$ (11,231,000)	$ (85,840,000)
Net loss per common share (See Note 6):
Basic (in dollars per share)	$ (0.43)	$ (3.39)
Diluted (in dollars per share)	$ (0.43)	$ (3.39)
Weighted average number of common shares outstanding - basic (in shares)	26,426,000	25,305,000
Weighted average number of common and common equivalent shares outstanding - diluted (in shares)	26,426,000	25,305,000