This is to kick off and share my speculation and design doodles for a scaled down Isiris- let's call it an Isiris Mini. A few folks have queried me about this possibility, so I'll lead off with what I think might be useful goals, and also an initial design pass on the basic LF configuration, which at this point is depending from the updates to the Isiris that are underway.
First off I think I have to address the idea of what and why... as well as a bit of the how.
Let's start from the fundamentals, in this case, the fundament or bass cabinet. Lest anyone not be aware, I have a bit of a soft spot for the Dayton RSSXXXHF series drivers. They rather successfully straddle the divide between woofers and subwoofers, and do so at a remarkably reasonable cost.
So first off we'll look at two possible alignments, which can be done in the same cabinet, and in fact, implemented as a "you make the call" depending on your setup and preferences.
The givens here are two RSS265HF-8 connected in parallel, which gives us a 2pi sensitivity of about 90dB for 2.83VRMS, in a 90L enclosure.
Here I'm showing the output level for 20W per driver.
There's still a fair amount of headroom for higher SPL at low frequencies, and if one uses a Cardas style placement with optimized boundary boost, the F3 at 38Hz can be substantially improved on, with basically flat response at the listening position down to 30Hz.
Excursion relative to Xmax is well controlled, an at 100 dB output you'll remain in a fairly linear part of the Xmax curve.
The predicted impedance curve looks acceptable for well designed amplifiers to cope with.
One might term this something of a purist approach...
First off I think I have to address the idea of what and why... as well as a bit of the how.
- The original Isiris was somewhat beyond the pale for most folks, understandably, with a BOM of around $10K, and certainly some complex building requirements. Mine was build manually, Mike's part pieces were cut with CNC.
- I've had a TA6 crossover update for this in the wings since 2014, but for a variety of reasons (including the Wavecor Ardent development) no time to address it or complete. By in the wings, I mean the parts were all bought and in storage.
- Interest from another builder in Singapore has resulted in me "re-opening" the case files on this sooner than I planned... so be it. But it's still a very expensive project. Not for the faint of heart or impecunious of budget.
- There has been a LOT of progress on the performance of drivers at more modest price points- witness the Tympany DA25, for example, or the SB26CDC-C004.
- So, somewhat from just an "artistic" viewpoint, I've been pondering how much of the Isiris experience might be brought to a roughly 3/4 scale project, with perhaps a 1/3 scale budget? Not a small challenge, but possibly a worthwhile one.
- Key driver concerns are polar response, CSD response, and distortion. With a 3/4 scale effort, I expect the system sensitivity to drop somewhat, reducing the expectations for the midrange and tweeter to more manageable driver choices.
- Construction may still be a challenge, but if I can do it with a standard table saw and a good dual bevel sliding miter saw, many others probably can, too. I'm a wires and sparks guy, not an expert wood worker. I am patient and careful though.
Let's start from the fundamentals, in this case, the fundament or bass cabinet. Lest anyone not be aware, I have a bit of a soft spot for the Dayton RSSXXXHF series drivers. They rather successfully straddle the divide between woofers and subwoofers, and do so at a remarkably reasonable cost.
So first off we'll look at two possible alignments, which can be done in the same cabinet, and in fact, implemented as a "you make the call" depending on your setup and preferences.
The givens here are two RSS265HF-8 connected in parallel, which gives us a 2pi sensitivity of about 90dB for 2.83VRMS, in a 90L enclosure.
Here I'm showing the output level for 20W per driver.
There's still a fair amount of headroom for higher SPL at low frequencies, and if one uses a Cardas style placement with optimized boundary boost, the F3 at 38Hz can be substantially improved on, with basically flat response at the listening position down to 30Hz.
Excursion relative to Xmax is well controlled, an at 100 dB output you'll remain in a fairly linear part of the Xmax curve.
The predicted impedance curve looks acceptable for well designed amplifiers to cope with.
One might term this something of a purist approach...
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