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In Reply to: RE: wideband shouting/beaming? posted by protos on September 13, 2007 at 08:49:07
Hi,
measurements doesn`t show a rising graph in the described frequency band. After 150 hours there should be no tonal imbalance with the widebands. When the assembling is correct, the placement of the baffles is fully parallel and there is some space to the rear- and side- walls the shouting/beaming is not caused by the speakers. Please give me detailed informations about room, placement, electronic components and cables, probably with this input we can go a step ahead!
Regards
Robert Bastani
Follow Ups:
OK.I guess then it may be the temporary baffles.They are a 1m by 50 cm by 50mm polysterene sheet.4x 1 meter 20mm thick square wood pieces are placed about 30 cm apart lengthwise (2 in front 2 in back)just so they can tighten the widband to the baffle using cable ties going thru the polysterene sheet.It is not of course the stiffest baffle but it can be done in one afternoon with almost no power tools.A good solution while waiting for the wood baffles to come in when you get itchy fingers.
The electronics are Aikido diy preamp, 300b diy amp or Mauro Penasas My evo diy amp,dddac 1543mk2 ,teac vrds 25x transport, cabling is diy mainly monofilament copper wound crosswise on teflon or other material.
Nothing there to suggest a peak at 600-800hz.I did try moving about the room to see if this effect diminished and there was some difference.I moved the speakers parallel instead toed in and this helped a little.Distance is about 2.5m and there is about 1m from side and 2m from back walls.
Hi,
best you wait for your wooden baffles, the material you used for your interims- baffles is not good, these baffles cause an early falling graph. The sound will change a lot with the right baffles, please keep us in touch! The placement and electronics seem fine (although i don`t know your pre- amp).
Regards
Robert Bastani
On another matter.What is the impedance of the prometheus?It is not mentioned on the site.One review quotes 16 ohm 100db another just mentions the impedance of the tweeter 16 ohm and wideband 8 ohm.I am measuring around less than 4 ohms on my MM which should be about right.The tweeter measures 9.5 ohms separately and the wideband with the 12 ohm resistor about 4.2 ohms.I had the impression the prometheus were 8 ohm impedance.
Hi,
the nominal impedance of Prometheus is 8 Ohms. The widebands measure a minimum of about 6 Ohms, the Gemini tweeters are nominal 16 Ohms, the impedance- minimum is about 12 Ohms. Please send me a pic of the wiring of your baffles that i can have a look if it is wired ok..
Regards
Robert Bastani
I think everything is wired ok.The 12ohm is parallel ,wired to + and - of the wideband then the tweeter is also parallel to the wideband with the difference that the cap is in series to the + tweeter terminal.Mathematically speaking 8 ohms paralleled with 12 ohms is 4.8 ohms and this paralleled with 16 ohms is around 3.7 ohms.Correct?Or I am doing the calculations wrong?
Hi,
from your description the wiring seems to be ok.
The impedance of speakers is always impedance vs. frequeny, the curve is rising and falling - measuring the connectors of the drivers without signal shows the minimum impedance only.
The drivers doesn`t work in parallel, they are separated by the crossover. In the crossover- region the impedance of the widebands is relatively high and the series caps of the tweeters rise the impedance for the tweeters to lower frequencies. The paralleled resistors flatten the impedance- curve to offer tube- amps optimized conditions.
Regards
Robert Bastani
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