Help with high pass filter in Bass Guitar Cab

[bassman3000]

Hello,
I'm a newbie here and did try the search but came up empty so if you must flame me be gentle!

I've built a vented 1x15, 4.2 cubic ft Bass Guitar Cabinet for which I'm using an eminence basslite C2515 speaker. In a vented enclosure eminence recommends a 35hz high pass filter to prevent overexcursion. I've been an avionics electronics tech for 10 years but audio is new ground for me. I'm somewhat familiar with passive crossover construction but need some help with cap & inductor values and frequency rejection.

What cap/inductor values do I need for a 35hz steep high pass filter to put inline with the speaker?

Is there any good online info regarding passive filter construction? My searches don't turn up any good info and leave me scratching my head.

Thanks ahead of time. :D

[tajanes]

Re: Help with high pass filter in Bass Guitar Cab

http://82.95.237.142/mhsoft/spk_calc.asp

[Hackomatic]

Re: Help with high pass filter in Bass Guitar Cab

Hello,
I'm a newbie here and did try the search but came up empty so if you must flame me be gentle!

I've built a vented 1x15, 4.2 cubic ft Bass Guitar Cabinet for which I'm using an eminence basslite C2515 speaker. In a vented enclosure eminence recommends a 35hz high pass filter to prevent overexcursion. I've been an avionics electronics tech for 10 years but audio is new ground for me. I'm somewhat familiar with passive crossover construction but need some help with cap & inductor values and frequency rejection.

What cap/inductor values do I need for a 35hz steep high pass filter to put inline with the speaker?

Is there any good online info regarding passive filter construction? My searches don't turn up any good info and leave me scratching my head.

Thanks ahead of time. :D

First, never apologize for asking a legitimate question!

Second, you're gonna find that trying to build a high level filter at that frequency is quite challenging . . because of the inductance value needed. You'd have to series 3 of the biggest coils to get in range. Then, a pretty hefty capacitor to boot.

Is active filtering an option?

[AJ]

Re: Help with high pass filter in Bass Guitar Cab

A passive filter at that low frequency will be very expensive, and not work well. A better route would be to use an active crossover, or no filter. Low E on a four string bass has a fundamental of 41hz. Not very stressing for a 15" at normal levels. Low B (five string) has a fundamental of 29hz IIRC, more stressful, but on common setups the low frequencies are reduced in level on purpose to prevent boom and to get higher spl.

Basically, don't worry about it.

[billfitzmaurice]

Re: Help with high pass filter in Bass Guitar Cab

What cap/inductor values do I need for a 35hz steep high pass filter to put inline with the speaker?

None. That recommendation applies to active filtering in a PA system. Eminence should be more specific.

[bassman3000]

Re: Help with high pass filter in Bass Guitar Cab

Thanks for the replys. Aj I'm taking your advice and not using one at all. I'm also building the amp(dual KT88 old Sunn design) so I know that 29hz isn't a threat and it will roll of about 4K on the high end. If the speaker over extends I'll have learned a lesson but I'm gonna go with no filter.

Thanks again all I've saved the link for future reference.

[AJ]

Re: Help with high pass filter in Bass Guitar Cab

The output transformer in that tube amp will limit any low frequencies enough anyway. You won't have a problem.

[jeff_free69]

Re: Help with high pass filter in Bass Guitar Cab

I've seen that spec in ALL the eminence spec sheets and I think its just a CYA tactic and frankly ridiculous. I've never seen a hi-pass filter on a bass guitar speaker - your low E string is about 45 Hz , so you needn't worry

Besides as others have pointed out, its not practical to get inductors and caps for that low a frequency.

BTW looks like a nice speaker - I'm considering it for a live system for bass & keys, but i may have to go with 2 smaller woofers for stereo - I can't lug (2) 4.2 cuft cabs ! i have no experience with neo-lite pro speakers yet - let us know how it sounds..

[jdclark]

Re: Help with high pass filter in Bass Guitar Cab

Seems to me that a filter is the wrong way to solve possible over excursion...
I wouldnt want to limit the output frequency unless you dont care about hearing sound you may produce under 35hz...

Do they make something similar to a zenner diode in concept with high enough power handeling to put in-line between the amp and speaker?