Members bfglp Posted June 28, 2010 Members Share Posted June 28, 2010 i have a pair of speaker cabinets with 15" 8ohm 200watt EV's that i use for bass. im thinking about adding a pair of 10" 8ohm 100watt celestion speakers to these. should i add crossovers also? i want to only have one 1/4" input to keep it simple. Link to comment Share on other sites More sharing options...
Members Belva Posted June 28, 2010 Members Share Posted June 28, 2010 Still just using it for bass? If so I wouldn't worry about crossovers. I'd try to get some spl's on these speakers. Hypothetically, if your 15's have an spl of, say, 94db and the 10's have an spl of around 100, all you'll hear is the 10's. I don't know WTF spl stands for. But it means decibels at one meter with one watt of power put to it. So you can see that an imbalance can really phuck things up. How do I know this? Link to comment Share on other sites More sharing options...
Members WRGKMC Posted June 28, 2010 Members Share Posted June 28, 2010 Still just using it for bass? If so I wouldn't worry about crossovers. I'd try to get some spl's on these speakers. Hypothetically, if your 15's have an spl of, say, 94db and the 10's have an spl of around 100, all you'll hear is the 10's. I don't know WTF spl stands for. But it means decibels at one meter with one watt of power put to it. So you can see that an imbalance can really phuck things up. How do I know this? SPL strand for Sound Pressure Level. Its a loudness measurement in Decibels. For X amount of watts, you'll get X amount of sound pressure emmited from the speaker. It would be like saying for this battery we get so many lumna from this lamp. Wattage in both of these cases is usually misused. All wattage tells you is whats consumed in power. It doesnt tell you how efficiant something is in doing its job. As far as the speakers go. I have a pair of 10's with an 18" in my EV cabinet. Theres a Rehostat in the cab to adjust the 10's output. Since higher frequencies require less power to produce, Having an attenuator would probibly be a better solution than a crossover. In my cab, the 10's are boxed off from the woofer to prevent the air from the woofer pushing on the 10" cones. The 10" speakers could be pushed all over by the wooders making all kinds of phasing and distortions of the signal trying to pass through the 10'S so having the two boxed off from the larger speaker is a must. Another reason not to use a Passive crossovers on a bass guitar cab is because it sucks too much power and taxes the head. The way most bass players do it is to Biamp their speakers. You can have extra switched jack in the back in case you ever want to Biamp the 10's and woofer using two different amps and having the amps set for different responces. Link to comment Share on other sites More sharing options...
Members tedmich Posted June 28, 2010 Members Share Posted June 28, 2010 SPL strand for Sound Pressure Level. Its a loudness measurement in Decibels. For X amount of watts, you'll get X amount of sound pressure emmited from the speaker. It would be like saying for this battery we get so many lumna from this lamp. Wattage in both of these cases is usually misused. All wattage tells you is whats consumed in power. It doesnt tell you how efficiant something is in doing its job. As far as the speakers go. I have a pair of 10's with an 18" in my EV cabinet. Theres a Rehostat in the cab to adjust the 10's output. Since higher frequencies require less power to produce, Having an attenuator would probibly be a better solution than a crossover... Does the rheostat just add a series resistance to the smaller speakers? People are usually paranoid about doing this to amps which aren't very impedance tolerant (tubes notoriously) while some amps work fine like this. The typical home speaker "L-pad" attenuator, which is a rotary approximation of a series/parallel resistor attenuator circuit, give the amp a consistent impedance (usually 8 ohms). Fancier designs (Pi-T-H pads etc.) give stable impedance to the amp and speaker which is not needed although some say they sound better. The cheapo rotary L pads are POS that can't handle almost any real power: the 50w and 100w rated L pads are cooked with pretty small amps. There are plans on the WEB to make fan cooled "100w" units which can be used as a sort of "power brake" attenuator. Using a nice beefy DPDT or rotary switch with big L resistors at set attenuation (0-3-6db are typical) work great IME. Link to comment Share on other sites More sharing options...
Members WRGKMC Posted June 28, 2010 Members Share Posted June 28, 2010 Does the rheostat just add a series resistance to the smaller speakers? People are usually paranoid about doing this to amps which aren't very impedance tolerant (tubes notoriously) while some amps work fine like this. The typical home speaker "L-pad" attenuator, which is a rotary approximation of a series/parallel resistor attenuator circuit, give the amp a consistent impedance (usually 8 ohms). Fancier designs (Pi-T-H pads etc.) give stable impedance to the amp and speaker which is not needed although some say they sound better. The cheapo rotary L pads are POS that can't handle almost any real power: the 50w and 100w rated L pads are cooked with pretty small amps. There are plans on the WEB to make fan cooled "100w" units which can be used as a sort of "power brake" attenuator. Using a nice beefy DPDT or rotary switch with big L resistors at set attenuation (0-3-6db are typical) work great IME. Tell you the truth its been a long time since I had it open. I beleive its in series. I do run the two 10s in series 16 ohms then parallel them with the 18" 8 ohm Jbl. With the rehostat, it will vary the impediance from 6~8 ohms which is a 2 ohm change between fully on or off which isnt too much. The transistor crate head I'm using is good down to 4 ohms. Link to comment Share on other sites More sharing options...
Members bfglp Posted June 29, 2010 Author Members Share Posted June 29, 2010 good to know i will need to seperate the 10's from the 15's. im trying to keep my rig small for giging so i dont want to use two amps. the rehostat is interesting is it easy to find one? Link to comment Share on other sites More sharing options...
Members WRGKMC Posted June 29, 2010 Members Share Posted June 29, 2010 Well you can use one of these. http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-265 or one of these. http://www.parts-express.com/pe/showdetl.cfm?Partnumber=260-262 They're called L pads but they are basically rehostats/wire wound resistors. These are 100w. They would be good for a 200w amp or so if placed in parallel to another speaker and in series with the 10s. If your amp is louder they might cook. In either case, You may not even need one. On my cab, with the 10s in series, then in parallel with the woofer, the two put out 1/2 the volume which matches the woofer fine. I remember I used two 4 ohm 10s in series which equals 8 ohms, then that in parallel to the woofer is 4 ohms with the rehostat fully on. Then as I turn the volume down on the 10s it brings the impediance up to 6 ohms. Link to comment Share on other sites More sharing options...
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