rumble issues - see old thread update

Tom,

If the pumping varies with volume, surely room mode interactions must be a prime suspect. My guess is that tweaking the eff. mass of the arm/cartridge may vary but will not eliminate it.

A concrete floor may dampen but it does not isolate, unless the concrete hasn't fully set and can slop around a bit. ;-) Owners of very substantial rigs on high mass stands, SRA platforms and solid concrete floors have still heard substantial improvements from adding true isolation with something like a Minus K. Not saying that would necessarily help with woofer pumping, just noting that concrete is not an isolator.

thanks guys

I'd hate to have to go to a another speaker, my friend has ported Salk's smaller

Dan_Ed - my Bat is on loan to a friend more than a few states away

Moscode 401 HR - I don't think it's clipping anymore but analog related

yes Doug volume is a culprit - increase it and more and slight warps in records.

never noticed this before, but I'm sure if things are not quite right even at lower volumes - the lower freq vail is affecting the sound.

45 rpm 180 gram blu note recordings sound fabulous
so maybe that has an effect

Room modes could be contributing. It does sound very resolving and no real flaws on cd, perhaps it sets up tone arm resonance issues. I'll try my Rives freq test and SPL if I can find them

ported speaker issue -
possibly - I'd hate to have to go to a another speaker, my friend has ported Salk's (a smaller model) and they pump all the time - he has a wood floor, not as well isolated and his speakers are close in to the back wall

diagnosis round II

Richard came over with his 'higher tech' scope

we found a little isolation issue caused by the light hollower SRA platform under the turntable - we replaced that with a 3 cm granite slab which isolated the table much more efficiently

the scope showed resonance problems in both channels around the 4-7 htz range - which Richard said were caused by a low mass arm being mated with an overly compliant cartridge. I told him that the ZYX and Triplaner often matched with great results - as many of you can attest to

we tried additional shims, counterweight options and also more and less weight to no avail
I typically run 1.75 g

he felt the high compliance of the cartridge and tonearm
combined with the highly resolving low end of the Dodd pre and Moscode amp were allowing the tonearm/cartridge resonance issues to be reproduced by the speakers

we checked the speaker baffle output and it wasn't sufficient to cause an issue

next step - Richard will bring a lower compliance cartridge to test out and see how it mates with the arm resonance wise

I'll call the various manufactures to get their input

any suggestions from others here on the arm / cartridge synergy would be very helpful

thanks

Tom

hit up an excellent website calculating resonance

http://www.gcaudio.com/resources/howtos/tonearmcartridge.html

I did a little research and calculations using the formula stated


check out the ZYX Universe site


http://www.sorasound.com/products/zyx/zyx-universe/

that's a pic with a triplaner from their beloved US dealer Mehran

ZYX universe specs

http://www.hifi.com.sg/products/cartridge/zyx/universe.htm

Universe specs

compliance
horizontal 15 x 10 -6 cm/dyne
vertical 12 x 10 -6 cm/dyne

I have the SB (0.24mv) version


Triplaner specs

http://www.triplanar.com/tonearm.html

11 grams

resonance freq = 1000/6.28 *suare root (M*C))

for vertical 12 compliance = 13.86 hz

for horizontal 15 compliance = 12.40 hz

these are both in the ideal range stated in the gc audio article

high enough to be out of the record warp subsonic stage but low enough to be out of the musical relm (well, most music these days)

so what gives?

perhaps dampening trough needed?