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Old 21st December 2004, 07:35 PM   #21
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Quote:
Originally posted by ingvar ahlberg
I do not have enough hair on my chest to argue with Grey, but this driver goes subjectively very low in even modest cabinet size. [/B]
Talking about hair... I feel bold. After lots of experimenting I think that Grey has a valid point. Even with best speakers in sealed cabinet, they roll off in the bottom part. By the T/L specs they have low Fs - in Lambda SB12 case it is 23 Hz, but in real life, that goes up to 30 - 40 Hz. Room adds its own to help (or else). Solution to the problem is as he stated - EQ (with cappable amp); and I would add vented box; or subwoofer. I will choose EQ.

Gamma seems unusuall speaker, low extension and high sensitivity. Price is low, so it makes it certainly attractive at least just to try. This also follows Grey's second suggestion - change the speaker. I do not know what will be the sound but it will certainly help with amp. I would like to check it out but do not know where to find it. Any suggestion is appreciated.

Just to illustrate how far I went with my experimenting, here is the pict of Ampeg tube amp where I added extra capacitors. These caps are beauty of its own, and only output portion of Ampeg is used - six 6550 tubes. I strongly belive that this amp is short on capacitors, but I will agree as well that I went too far.
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Old 21st December 2004, 07:54 PM   #22
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For all suggestions and help I received from you, I feel responsible to give you something back. Today, mornig light was so great and I did a shot of fog setting in. I hope you will enjoy the view as I did.
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Old 21st December 2004, 08:44 PM   #23
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Quote:
I would like to check it out but do not know where to find it. Any suggestion is appreciated.
Well mail me and weŽll work something out, i can buy the units at the best price and as we purchase a LOT of parts from component brokers operating from the states we might find a good transportation method too
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Old 21st December 2004, 08:54 PM   #24
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Quote:
Originally posted by ingvar ahlberg

Well mail me and weŽll work something out
Just did it.
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Old 21st December 2004, 09:16 PM   #25
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I just sold my '74 SVT (silver front--a classic--but I can no longer justify the combined weight of the head and cabinet). I will agree that the capacitance in the amp is light by hi-fi standards, though it is normal for bass amps. For hi-fi use, there's no such thing as too much capacitance, although you might want to put a resistor or inductor in front of the caps to reduce the peak load on the rectifier. For bass (aka "pro") use, you have to watch out for what your cabinet can take--small power supplies are a poor mans' limiter and are purposefully designed that way in order to keep you from blowing your drivers across the room. Proceed with caution; don't say you weren't warned.
The day may yet come when there are reasonably priced drivers that are actually flat, but what we have in the here and now are essentially car woofers repackaged as home units. Hint: Check the response against a typical car sub. They've got huge Xmax, moderate efficiency, and look gnarly as hell, but are limited on the bottom. The parameters can be shifted, of course. Lower efficiency, for instance, would be acceptable to many people, and as monster class D amps increase market penetration, it's likely that we'll see exactly that. The sound quality of those amps we'll leave for another day. For the time being, think of it as an opportunity to learn more about filters--this is known to experienced DIY designers by the more formal phrase,"if life hands you a lemon, make lemonade."
Just be glad these drivers have large Xmax...you're gonna need it.

Grey
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Old 21st December 2004, 09:26 PM   #26
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I am still thinking on the amp subject..,
I did few callculations in Aleph X spread sheet, where I changed figure for AC current gain. I did two versions with 66% gain and 80% gain. As a result I got increased power toward lower impedances. There is peak current of 15 or 25 Amps.
Is this calculation correct, or is this possible at all? Would this be the right approach for difficult - low impedance speakers?
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Old 21st December 2004, 09:57 PM   #27
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Quote:
Originally posted by GRollins
you might want to put a resistor or inductor in front of the caps to reduce the peak load on the rectifier. For bass (aka "pro") use, you have to watch out for what your cabinet can take--small power supplies are a poor mans' limiter and are purposefully designed that way in order to keep you from blowing your drivers across the room. Proceed with caution; don't say you weren't warned.Grey
This was just a test to check if the bass improve with more capacitance. Dealing with this amp is dangerous from any point of view since it is very high voltage. Caps are very big and they do not fit into the case and they will need separate box. Certainly they cannot sit like in the picture. I have two of those Ampegs that I got as present/ trade from Ampeg (St.Louis Music) when I did photography for their brochure and web, so I am not using them in "normal" way combo + head. They are really nice as LF drivers, 2x300W of pure tube sound.

Quote:
Originally posted by GRollins

For the time being, think of it as an opportunity to learn more about filters--this is known to experienced DIY designers by the more formal phrase,"if life hands you a lemon, make lemonade."
Just be glad these drivers have large Xmax...you're gonna need it.
Grey
Thank you Grey for showing me the path. Interestingly I came on my own to many of the similar conclusions, but not being very confident (this is my hobby, not profession)
I always think that I am doing something wrong.
AR2
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