Hi,

I have a filter cut-off option on the Europower amp I use to power my JBL 118 subs. I can switch my cut-off between 30 and 50 Hz and the frequency response is 55 Hz to 300 Hz. I have been using the 50 Hz cut-off but was wandering if there was anything sonically to be gained from using the 30 Hz cut-off or would I just be wasting power amplifying something that people do not hear or feel.

Thanks

Paul

I have my cut off set to 25hz 30hz is more common 50hz is too high IMO

Thanks Mark, I will give it a go over the weekend

I am playing at a dinner dance in The Royal Hollaway college Egham and a 21st on Saturday so they will like a bit a bass I am sure

If the frequency response of the speakers is 55-300Hz, I don't see any point in sending anything lower than 50Hz through the amp.

Me too!???!!

Do you own some very good subs? Or very large boxes tuned low?

If the answer to both of those is no, then you'll be wasting power on frequencies that the box can't play at a level you'll hear over the frequencies it plays well, and also risk damage by overexcursion of the drivers as they'll be unloaded at those frequencies

Spot on once again from Norty;

I use a cut off of about 20Hz, simply to remove any seriously harmful content which may cause excessive driver excursion, as mine have little or no loading at these very low frequencies. My cabinets are tuned low and can produce significant output at 35Hz, not that you find that very often in normal music, although it can make sound effects really come to life.

For higher tuned cabinets there really is no point in going below about 45Hz as most are several dB down at this point.

EDIT: To just mention that just because a speaker is advertised with a frequency response of 30Hz to 18Khz, that doesn't mean that it can actually work at those low frequencies. These silly specifications are very misleading as they often don't tell you how much quieter the speaker will be (efficiency) at these frequencies, as compared to the normal output - it is often very poor indeed.

Simple rule of thumb would be to [i]not[/i[ shove signals into a speaker for which it is not designed, as damage could result even below maximum thermal rating. Don't expect to get earth-shaking rumbles from a plastic cabinet with a 15" driver - it just isn't going to happen, and trying to 'EQ' things up simply risks damaging the speaker.

Horses for courses.

Just to add to that, any decent speaker manufacturer with nothing to lose/hide will advertise their frequency responses at certain points, typically f3 and f6 (the frequency at which the output is 3db and 6db down respectively from the average). Many companies that advertise 40hz to 20khz don't tell you that the ends of that curve are -20db down on the average and thus inaudible.

Also, don't take frequency response as an indication of where you should set the crossover point. Whilst a speaker might produce flat output up to 250hz it may start to suffer bad ripple and time domain issues at 150hz which will make it sound horrible.

Things to check for are whether this is achieved with a specific controller (some subs are useless without the factory controller/settings) or with EQ applied. The least correction the better in my book.

Agree with almost everything said so far.

Surprised the bins only go down to 55Hz?

Most good 18" bins and some 15" will go down well below 55Hz.

Don't forget that a basic active crossover at 55hz will start lowering the frequency well above that point.

35 Hz is a good setting for most Subs, that is if you are not sure what the Sub is designed to take

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One other comment, the setting is not written in stone.

At venues when you are using lower power, then you will get a warmer sound if your speakers and settings are lower. It will be like a loudness control.

For higher power requirements then use a higher setting and save damaging speakers!

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edit: added comment:

Just found this on JBL website:

those bins are well down at 38Kz almost 10Db which if I remember is 1/2 for 3 Db, 1/4 for 6 and 1/8 of teh power for 9Db. So below 55Hz they are really doing very lttle.

Frequency Range (-10 dB): 38 Hz - 300 Hz
Frequency Response (±3 dB): 55 Hz - 300 Hz