Does this look right for the ER18 box? Would it be possible to use a slot instead of a port so I can have it front firing while keeping the height of the speaker down?
I spoke more with Dennis about cabinet size for the ER18. He says the ER18 has essentially the same low end roll off characteristics as the SEAS W18. A 0.5 ft³ cabinet as you suggest will be alright, but a somewhat larger cabinet will get the most bass out of that woofer without harming performance in the midrange.
Dave Ellis, who originally designed and sold the Ellis 1801 speaker, came up with a 0.75 ft³ (21.2 liters) ported cabinet for the W18. That is the same as what Jim Salk now sells for the 1801 or HT1 bookshelf models.
I'll send you a pdf copy of the 1801 cabinet details. It used to be available at
Ellis's web page. You should be able to easily adapt that to your speaker.
External dimensions
9" wide
19" tall
14¼" deep
That assumes ¾" thick MDF construction, and two internal braces that run full length and full width.