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In Reply to: RE: Any experiences with different caps in the Prometheus posted by driguy on August 30, 2008 at 19:45:48
I hear you on backing off the crossover point and actually have had them around 10:30 for some time with great results.
I actually had another pair of Cary's with about $1200 worth of parts mods including the Mundorfs SIO and yes they were somewhat better but the density issue was still there. Actually the stock Cary's match up better than all other amps I have used (well, except for driver grip which 845's in push pull were with but the mids were annoying on the Prometheus). Don't get me wrong as I have been very happy with the Prometheus the last two years I have owned them but as you know with this hobby one is always trying to improve on sound.
Tony I do wonder if the Atlas helps with image density. Also would be interested if you feel there are any negatives with the introduction of a second full ranger (aside from requiring more space around the speaker) as it gets further away from the advantages of the whole point source sound realizing that with separate tweeters and bass it is not really a single point source speaker to begin with.
Follow Ups:
If you are even thinking of going to the Atlas setup it is a no brainer. Most people have a problem because they have time and money invested in a single driver baffle. The Atlas setup (IMO) will give you the following: Better dynamics, less distortion, and yes, a larger, denser presentation of the music. Depending on your room size, the original 12" driver subs should be sufficient. The only downside is the cost of the driver and reworking the baffles. Also, your amp must be able to run a 16 ohm load. Most can without a problem but you will get less power due to the impedance mismatch (assuming no 16 ohm taps). I use an Emission Labs 300b XLS to get some of the power back. I just set my cathode current to 107mA using an adjustable resistor. Oh, BTW, if you are using a mesh plate 300b that is giving you a lusher presentation than a solid plate at the expense of detail, accuracy, openness, and even soundstage. Depends on what you are really looking for.
Regards
Tony
Tony I'm using newer Western 300bs.
It sounds like adding a second driver might do it for me. I'm also thinking of buying a Tone Tubby hemp alnico driver to see how it compares in open baffle.
The 16 ohm is not possible but maybe they could be wired differently. I have tried 16 ohm with other amps and it gave me too much treble and not enough meat.
Your amp can probably take the 16 ohm speakers without a problem. The only other option is to wire in parallel which will give you a 4 ohm speaker. My amps did not like that at all but YMMV. You will get less output but the bass will actually be a little tighter in most cases (at 16 ohms into an 8 ohm tap).
Those tubes are pretty nice from what I have read and heard but they will take quite a bit more cathode current than a mesh plate and will probably sound a bit better when driven harder that is assuming that you are still running at about 68mA or so. If your amp is self biasing their website notes that you can run up to 100mA safely. Elsewhere on AA you can get ideas as to the sound with increased current.
If you get the Tone Tubbies I would get the treated ones and the 16 ohm units as you can parallel those to get a nice 8 ohm speaker. You may have to lower the crossover point a bit in case the TT's don't go quite as high in their response. The tweeters can go much lower than 10kHZ. Go to Audiocircle.com and tap into the open baffle forum if you haven't already.
Best of luck.
Tony
Thanks for the tips.
I've spent a lot of time playing with a room analyzer, my subwoofer placement and settings. My experience may not apply to your room but here's what I found:
I used to have the crossover at 10:30 or 11:00 (on the previous plate amps, not the current SAM2s). The analysis mic and software showed that I had a hole at the integration point between subs and main baffles. It's easier to setup the subs this way because you can whack up the bass level to get great deep bass but I was missing upper-bass as a consequence. I now have the crossover at about 2:00 and the level much lower. This excites room modes far less and lets me hear whole bass lines that I'd been missing, timing is better too as my troublesome room modes are pretty much fixed. The graphs I have for the bass response are really quite good now.
I'm also trying digital eq on just the bass feed on my now optimized subs, this really is the icing on the cake.
I have a behringer EQ (collecting dust) that I tried separately on the bass but I think it was messing up the sound somehow. I think I should buy the mic for it and do my own room analysis.
I found that turning up the crossover point did ruin the imaging somewhat as Robert has written about but I'll try your low volume method tonight and see how it sounds.
The XTZ mic & analysis software allows me to much more accurately understand the bass response than the Behringer does. It think it's vital to have a good sub setup before using the Behringer. Also Behringer recommend not using the RTA below 100Hz because it's not accurate (for some rooms), I'm guessing this is due to room modes and because they only use a single mic position.
I found that when the subs are setup to not have a hole at the sub to main baffle integration point, setting the sub level becomes incredibly sensitive. 1mm either way kills or floods the bass.
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