overpower or underpower, a hypothetical..

[Mr. Foxen]

I'd love to see the schematic that shows a high pass filter in a bass amp.
It's a good idea to hi- pass at around 30hZ, so it would make sense to do it; I've just never been made aware of its' existence in a mainstream bass amp.

Plenty here:
http://www.schematicheaven.com/index_HTML.htm

An output transformer will do it for you.

 

[rpsands]

Genz benz has one. Gk has one. Markbass I am positive has one (but they might do it via compression/limiters on the low end, I can't tell).

 

[bongomania]

Yep, the Genz reps here confirmed their amps use a high-pass.

 

[rpsands]

Yep, the Genz reps here confirmed their amps use a high-pass.

They have alluded to the fact that it's a much more complicated circuit also, using eq boosts to compensate for the dip at the shelving freq. Not sure of all the details there though.

I believe that's what the Thumpinator uses too right?

I only mention that to double clarify because I know people have just applied a 30hz 24db/oct high pass and found the results not pleasing, which I can understand

 

[Richard Lindsey]

" Douchey " ??

The opposite of "touche"? Perhaps best said with pseudo-French pronunciation: "doo-SHAY".

 

[bongomania]

They have alluded to the fact that it's a much more complicated circuit also, using eq boosts to compensate for the dip at the shelving freq. ...I believe that's what the Thumpinator uses too right?

I haven't checked his circuit in detail, but the EQ profile from the Thumpinator is a ruler-flat line down to about 35 Hz, with a steep drop thereafter, so that 30 Hz is about 3dB down and below that is essentially "gone". There is no audible loss in the useful frequency range, and I've never felt the need to boost the lows.

 

[12bass]

The Eden WT-series also roll-off frequencies below ~40 Hz. AFAIK, this is common in bass amplifiers.

 

[Bob Lee (QSC)]

2. If underpowering a cabinet isn't a big deal then why do companies like EAW, Bergantino, and Clair Brothers recommend supplying 1.5 to 2 times the rated power of the speaker enclosure?

They recommend that as a maximum amp power point.

You can always use less power, if you can get the sound levels you want without any significant clipping. But it may mean you went a little overboard when you selected the loudspeaker.

 

[rpsands]

They're usually a fixed corner on most amps. Variable high pass doesn't exist on a bass amp that I'm aware of.

 

[Passinwind]

They're usually a fixed corner on most amps. Variable high pass doesn't exist on a bass amp that I'm aware of.

Acoustic Image amps do have a variable one. It gets to be a bigger and bigger hassle to make it variable as the filter order increases though, at least for analog implementations.

 

[bongomania]

Cool, I looked, still no actual HIGH PASS FILTER.
I'm not asking about an output transformer or some sort of EQ section but an actual hi- pass filter. You know, it's just like an active crossover with only the high passing through. There would be an adjustable frequency (and maybe even the slope). Maybe the terminology is confusing people?

You're missing the part that this filter will usually NOT have any controls whatsoever, and will be built into the output stage of the preamp.

 

[dubcut]

Quote : If underpowering a cabinet isn't a big deal then why do companies like EAW, Bergantino, and Clair Brothers recommend supplying 1.5 to 2 times the rated power of the speaker enclosure

Answr:
Because these companies realize that in the real world, full power is seldom reached, if ever. As I pointed out in an earlier post. Wattage rating is the power CAPABILITY of a well designed amplifier. On cheaper ones, it is simply a number that it will never reach.

A thundering 110 hz (low a) can pull as little as 1/3-1/2 full power from your amp, while a 1200+ can pull way more. And sound less loud, due to cabinet design. Unless you build a 1/4 wave cabinet...lol

 

[aborgman]

Cool, I looked, still no actual HIGH PASS FILTER.
I'm not asking about an output transformer or some sort of EQ section but an actual hi- pass filter. You know, it's just like an active crossover with only the high passing through. There would be an adjustable frequency (and maybe even the slope). Maybe the terminology is confusing people?

No, just your misuse of the terminology.

A couple resistors and capacitors slapped together on a circuit board can be a high pass filter.

A op-amp and a few resisotrs and capacitors on a circuit board can be a high pass filter.

A high pass filter can be adjustable, or completely unadjustable.

Anything that passes high frequencies and lowers the level of low frequencies - regardless of how it does it - is a high pass filter.

 

[dubcut]

Uh, no. That is not correct. All this "square top of the wave" stuff is baloney. The loudspeaker dose not care about the waveform of the signal.


Too little power cannot overheat a loudspeaker. Too much can.

However, the clipped wave being fed to your power amp causesa different voltage. So, directly, no, the speaker 'dose' not care, but after it receives a longer duration of heat from the powr amp, it 'dose' care...

As for "2 little power cannot" I am referring to situations where the power amp produces in excess of its rating due to input over-voltage. Therefore, You are ABSOLUTELY CORRECT in your assertion that too little power cannot do harm. But if the preamp is pushed to overfeed the poweramp, The boosted signal output is a boost of a waveform with higher voltage, thus, more output power. Also, this power comes with a longer heat cycle, due to the duration of the top of the wave being nearly flat. And can clearly create scenario where the amplfier gives more voltage to the load.

The situation of feeling underpowered may even force the user to do exactly what he needs not do, and crank up a bit too much, creating the excessive output.

As I said before, it would take a SLIGHTLY underpowred setup, with a relatively low amount of output regulation to create the scenario.

Somene who is a few percent uderpowered, attempting to raise a few extra db's can create the situation easily. If they have a REAL amp.

On the other end of the scope, so called Over-powering...is not overpowering, due to the many CRITICAL factors that apply to a reactive load in an enclosure. A 150 percent capability of an amplifier is just a capability.

 

[Bob Lee (QSC)]

No, the clipping actually reduces the voltage that otherwise would've been delivered to the loudspeaker. Clipping doesn't change any "duration."

 

[Mr. Foxen]

Cool, I looked, still no actual HIGH PASS FILTER.
I'm not asking about an output transformer or some sort of EQ section but an actual hi- pass filter. You know, it's just like an active crossover with only the high passing through. There would be an adjustable frequency (and maybe even the slope). Maybe the terminology is confusing people?

Firstly, as has already been said, check up the meaning of the words you are using.

Also, the Peavey Firebass, and the various incarnations (think there is a Max which is the same with different front panel and some lower powered versions) has a crossover so with a patch lead you can run it high passed, low passed or as part of a biamp system.

 

[billfitzmaurice]

Quote : If underpowering a cabinet isn't a big deal then why do companies like EAW, Bergantino, and Clair Brothers recommend supplying 1.5 to 2 times the rated power of the speaker enclosure

Because those recommendations should apply to PA systems, and only full range systems at that, where the increased power density in the harmonics that is the result of clipping can cause damage to high frequency drivers. Never woofers. That fact is where the myth of underpowering started, as the average user doesn't know the difference between high frequency and low frequency drivers and how they react quite differently to clipped waveforms. Unfortunately even some sources that should know better inexplicably don't.

 

[bongomania]

this power comes with a longer heat cycle, due to the duration of the top of the wave being nearly flat.

False. There is no "longer heat cycle"--it does not exist outside your imagination.

 

[wcriley]

Cool, I looked, still no actual HIGH PASS FILTER.
I'm not asking about an output transformer or some sort of EQ section but an actual hi- pass filter. You know, it's just like an active crossover with only the high passing through. There would be an adjustable frequency (and maybe even the slope). Maybe the terminology is confusing people?

As I wrote earlier: G-K amps have an "adjustable frequency" (although only adjustable between 2 predetermined frequencies) for their high pass filter, unless I'm misunderstanding something. I think the "Deep" switch on the MusicMan amps from the late 70s functioned the same.

AFAIK a highpass filter only requires a single capacitor and some resistance. That's how the "Bright" switch works on most guitar amps.

Edit: I just checked the schematic for the old MusicMan amps. The Deep switch bypasses a cap in line before the Master Volume, taking that part of the filter out of the equation. There are other capacitors in the circuitry that are probably also acting as filters. I need to find a G-K schematic to see how the "String" switch works.

 

[Bachatero36]

Hey Guys I wanted to ask is it ok to Use a 500 watt head *hartke lh500*with a 800 watt cab*GK MBE 410* like what im trying to say is basically would the lack of power to power a 800 watt cab sound bad as its not moving the cones for its lack of power thru the cab or would it sound good as apose to a 500 watt bass cab would there be a diffrence in sound base on RMS wattage of the 800 watt cab and a 500 watt cab? I didnt really read through this thread but if someone can give mi a answer on this i would appreciate it Thanks In Advance
JD-Bass