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AR9 - bitumen sheeting on inside of cabinet


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After 30 years of living on & off with the AR-9, I'm convinced that it's one of the most "organic" full-range systems ever designed.

By that, I mean that it transcends certain measurement techniques and loudspeaker "truisms" - and adjusting one (or more) aspects of the system according to current dogma might backfire.

The notion that an absolutely inert cabinet will be superior to one that's not so inert is pretty much accepted as unquestioned fact by audiophiles, but some of the most powerful systems ever designed & built would fail miserably at the so-called "knuckle test". The big JBLs, Altecs, and the AR-9 come immediately to mind - tremendous LF motors, housed within 3/4" plywood or PB cabinets.

Now clearly, there's a reason that these ancient systems hold an attraction for so many, and it's most likely because they weren't built to today's standards.

When properly powered, the AR-9 has spectacular LF reproduction - clean & well-defined, with a very musical presentation - it does NOT sound like an add-on subwoofer, but its extension will rival most of these.

I don't think it's unreasonable to ask if the tall cabinet's resonant characteristics are integral to the 9's resultant balanced & well-blended full-range quality - whether through engineering or plain good luck, those woofers sing in that cabinet.

That said, it might be a fun experiment, if you could easily remove the bitumen sheets. Since you've already pulled the crossover, all you'd have to do is calculate the sheets' total volume, and subtract that from the crossovers' before adding appropriate replacement volume - like a wood block?

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What I have noticed with my AR94si is that improving the caps and the tweeter has opened up the sound tremendously. A lot more detail. And now I also notice a slight boominess coming from the cabinet - right in the midrange and only at medium to high levels.

After recapping the AR9, I expect something similar. It really is a boomy cabinet...!

I have decided to apply the sheets to my upgraded AR94si. I won't bother with the AR9 until I hear some boominess. Its a one way mod. Once the sheets are applied, there's no going back. In fact it probably makes sense to apply some bracing first and then opt for the sheets.

Your response has helped me to see the correct way forward. Outboarding the XO will make such future changes very easy and that is a plus, although removing all the stuffing is not so easy. I hope that stuffing is not bad for the chest...!

Thanks, kkc.

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