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AR LST road trip....


xmas111

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What is the purpose of the Johnweather AR9 isolation bases? What I see are two solid-wood pine boards (plywood would have been more stable) with a wood cup-steel ball-wood cup isolation between the two boards. I don't see any springs or rubber grommets; only the steel ball riding in the hollow of the wood. Why? What is it doing? There would likely be the same vibrations radiating past this assemblege of wood and steel down to the floor; on top of that, there is the possibility of some extraneous noises from the platform "riding" freely on the ball bearings, but no real isolation to the floor.

http://johnsweather....speakeriso.html

Turntable isolation is a great thing for about any turntable other than the AR-XA/XB Turntable, which has excellent built-in isolation. Another problem for some turntables is that very low-frequency sound waves (transmitted through the air) can cause some turntables to vibrate sympathetically, thus causing rumble. No form of speaker isolation can prevent the actual sound waves from traveling through the room.

--Tom Tyson

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Tom,

The reasoning behind the isolation bases for the AR 9's came from a 32 page thread over at Steve Hoffman Music Forum. There's a member over there "bdiament" who's an recording engineer that came up with the idea of Steel balls in cups for speaker isolation. He certainly seems to know what he's talking about.

http://www.stevehoff...4013&highlight=

I won't it into the scientific details of the isolation bases on how and why they work because to be honest I can't say I even understand all of it. :mellow: I'm not an engineer...just a weekend hobbyist who loves this stuff. :)

I did take a shortcut in the "optimal" design of the bases by using cups and wood on top and bottom. Optimal would using the the bottom cups only and have a piece of marble between the speaker and top of the balls. I plan on someday getting the marble and replace the top platform with it.....until then this design will have to suffice.

Guess the real question is do the bases help????? Yes, it did seem tighten up the bass a little......to me anyway. Then again some people swear using million dollar interconnects or power cords make a difference too. So I guess like so many things in life it's really subjective and I won't argue if it works or not. :rolleyes:

Now, don't laugh .........but the best thing I like about the bases is when I'm vacuuming the floor....... the bases take the hit and not the AR9's! :lol:

On a side note I should have the reconing kits on Monday and hope to have the LST's back up and running by Wed. :D

John

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Thanks guys for the info.

Here's another one I'm thinking about. QSC RMX 1450 seems to have plenty of power for the buck.

Little better looking than the crowns in my opinion.

http://www.qscaudio....mps/rmx/rmx.htm

John

John,

I've been using a QSC RMX 1450 for a couple of years now to drive a pair of AR-9's. The fan on this amp runs continuously and is easily heard at low levels so you may want to consider an amp that switches the fan on when needed. I disconnected the fan in my unit and have never had a problem as most of the time I listen at low to moderate levels. There have been a couple of occasions where I have driven the 9's with very high output for ~ 30 minutes before the thermal protection kicks in (as it should).

Jeff

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The QSC RMX-series amps are excellent, high-power amps with low distortion. These are reliable, proven designs. I have a 2009 model RMX-2450, and this amp puts out around 650+ watts/ch into 4 ohms at under 0.1% distortion. It is completely stable under any load, but it does have a fan that cools the output-device heat sinks, so it might be necessary to mount the amp in a rack cabinet or in a spot that blocks the fan noise. Images are of the inside of the RMX-2450, and it can be seen that the amp is strictly professional in build quality.

--Tom Tyson

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Thanks Tom for the information on the amps.

It does look very impressive on the insides!

I'm still looking around with lot of options to ponder.

Got the reconing kits today form John at M_Sound.

The packaging of the kits is very impressive to say the least. Now I have to spend a lot of time and read his instructions before the first drop of glue/epoxy is applied.

Check out the packaging......

John

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I've mentioned this before, but I found an amplifier recently that works great with these older AR speakers about any issues -- the professional Crown XLS series. For $299, one can buy the smallest version, a new Crown XLS-1000 Class D power amp that is stable down into 2 ohms. It has fan cooling, but the fan rarely ever operates unless the amp is pushed hard. This inexpensive little 8-pound amplifier puts out an impressive 215 watts/channel into 8 ohms and about 350 watts/channel into 4 ohms and all the way up to 550 watts/channel into 2 ohms. Insofar as this is a modern professional design, it is designed to take abuse, and it can be run wide open all day long if needed. The design is very quiet and effortless into any load, and it is backed by a three-year Crown factory warranty. The most important thing is that you have the confidence that it will not self-implode one day into your valuable, hard-to-repair AR-LSTs.

After posting a question on Bel Canto class D amps with little response I was interested to see Toms recommendation for the crown xls range...so much so that I purchased the xls2500 as a replacement for an aging Adcom555.I use this to drive my 9's.Is it better...well yes and no.The bass is a little punchier and 'big' whilst the top end seems a little harsher to my ear...with a definite 'set back 'to the sound stage..the extra power...around 750 watts does appear to make the speakers run effortlessly so I guess it is a keeper until one of these days I find an amp that does everything well

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"After posting a question on Bel Canto class D amps with little response I was interested to see Toms recommendation for the crown xls range...so much so that I purchased the xls2500 as a replacement for an aging Adcom555.I use this to drive my 9's.Is it better...well yes and no.The bass is a little punchier and 'big' whilst the top end seems a little harsher to my ear...with a definite 'set back 'to the sound stage..the extra power...around 750 watts does appear to make the speakers run effortlessly so I guess it is a keeper until one of these days I find an amp that does everything well."

heland,

I, too, use the XLS Crown, and I did a A-B comparison awhile back between my old Adcom 555 (which was working fine, but growing long in the tooth) driving a pair of AR-10πs in my office system. I honestly could detect no difference whatsoever between these two amps on switching back and forth (with an old Switchcraft input switcher) on a variety of music. I balanced the output levels by using the input controls on the Crown, such that both amps were producing the same amount of output for a given input from my Adcom preamp. Granted, I did not play them at super-high output levels during the comparison, but on a variety of music, both amps sounded identical, across the band, on quick back and forth switching, which is exactly what I would expect from amplifiers producing very low distortion and flat bandwidth. No harshness from either amp; bass response equal in my experience; both amps exhibiting low noise. So why use the Crown over the Adcom? Reliability. If the Adcom failed for some reason—more likely due to the old age of components—the amplifier would be more likely to damage the AR speakers. Also, the Adcom protective circuits are not as advanced as with the newer amplifiers, and these older consumer amps are likely to run hotter than the newer designs.

Remember, the ear's memory is relatively poor after even a few minutes. However, I did not do a "double-blind" test—the definitive way to test—but only a "A-B" comparison, so my comparison was by no means definitive, only a quick comparison. I have also not done the comparison driving the AR9, but I would assume the load would not adversely affect either amp.

--Tom Tyson

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Well all is good here again!

Finished reconing the blown woofer last night and just finished installing it.

They sound as good as they did before the disaster. Absolutely wonderful sounding speakers!

John from M_Sound (who supplied the reconing kits) is a great guy. He answered my emails quickly with the few questions I had.

So if any of you guys need any speaker repair parts, surrounds, recone kit....etc. I too can now highly recommend him.

The actual reconing wasn't to bad. You just have to really take your time and pay attention to what your doing. AND DON'T RUSH IT! Let it sit for several hours after each epoxying step. I let it sit a day between each step......three days in total.

I also like the way John places the "Lead In" wires so they attach to the voice coil under the dust cap.

I still haven't decided on a amp yet.

So anyway, I'm a happy camper again! :)

John

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