How do I make a LP at 80hz

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
I'm about to go full range after years listening to celestion dittons, mainly the 44's and 442's. I have opted for a pair of Mark Audio 10.3's, and whilst they are sure to sound wonderful I suspect I'm going to miss the visceral experience of bass that comes from 12" paper cones.

So I figure ill keep a set of the bass woofers and use them is a sub design, there are lots of plans and enclosure calculators online.

What I am not so sure about is how to build a passive crossover. I'm aiming at around 70/80hz.

Anyone out there help me with the spec I would need for the inductor and cap? I don't even know what order of crossover is best suited for the task, is there any need to go more complex than first order?

Many thanks in advance - LB
 
Remember your FR are already starting to rolling off at your target 80Hz so your first order will probably be getting a summed 12db,...and a second might get you 18db summed. The power handling of your FR should go up as Xmax won't factor in anymore.

__________________________________________________Rick............
 
Thanks Richard - I have made an error in the post I fear, comes from waking up at the same time as my two year old son :( I wanted to cut the high frequencies from the 12" cones and use them as a sub, though your right, running them as a two way would increase the potential volume.

I built a pass f5 which does around 25w per Chanel, the FR are rated at 30w nominal and have an arrester, so I should be on safe ground with volume levels.

What I don't know is, how to construct the passive crossover to eliminate the frequencies above 80hz from the woofers.

Is it quite simple?
 
Crossovers do have 'slopes' and 'orders'. A passive crossover at 80 Hz means huge coils.
Huge ( in value) means lots of copper so added resistance and loss of efficiency.
A proper filter for a sub means that it has to cut firmly all the frequencies out of the working band, so a 4th order. It depends also on the drivers used of course.
you can try 10 mH--200uF--7.5 mH--100 uF
 
Hi lorienblack,

Whether you go active or passive you need to have a starting point that looks at all the interactions of your system (filter/driver/enclosure) for both, the sub and the main speakers.

To get you started I recommend that you get familiar with a loudspeaker simulator program such as Hornresp: Hornresp .

Regards,
 
Given the slopes achievable, there isn't such a thing as a passive 80 Hz crossover since lots of sound will over for octaves above and below, as mentioned earlier.

I buy my amps at the second-hand store and they are an order of magnitude cleaner than my ESL speakers. Amps are cheap. Invest in speakers.

But if you crossover actively and 24 dB/8ave as high as 140 Hz all you need is a single woofer. And so you can make one real great one instead of two so-so ones.

(Whenever I offer that "140" figure it is always hotly disputed by theoreticians and the Golden Eared who tried it once but supported by folks who have lived with it.)

Ben
 
Last edited:
Higher order crossovers introduce minor ringing and phase (basically time) delay. Refer to a freshman level EE textbook to see more about this.
Do correct me, but I have the impression that the dramatic ringing you "hear" in theory isn't audible in ordinary music listening. Likewise people seem unable to be disturbed by phase issues of the sort you refer to.

These factors are however, very important to people selling equipment that overcomes such challenges.

Whether you agree with that sentiment or not, perhaps you agree that there are factors vastly more audible that need to be attended to in priority. For example, the monstrous aberrations arising from forcing pass-band drivers to play needlessly large bands.

Having been a faculty member in an engineering department, it's easy to smile about your quip about "freshman-level" textbook knowledge.... except to ask if you passed your freshman year?

Ben
 
Last edited:
The ringind in not in the time domain, but in the frequency domain. Yes, I know about cone breakup limiting the frequency range, but 12dB/octave and a narrower band per driver is easier to design for.

I studied physics for six years, learning electronics mostly by myself, and I worked in the electric/electronics industry for over 20 tears. Since you were exposed to electrical engineering curriculum, I now can assume you know all these factors.

It is an interesting project I'll be watchiing. Another servo-woofer project ended with the commercialization of the LW Erath speaker system. It had very good bass and generally sounded pretty good.
 
I bought a BK 500w sub plate and will build a sub around that, so the LF is well and truley taken care of. still would be nice to cut out the LF on the full ranges,below 100hz, just to have the option of rattling the windows once in a while.

I have some three way crossovers nocking about, is it possible to combine the properties of the mid frequency and high frequency to drive a single speaker?
 
A person with your aptitude for learning physics and electronics should have no trouble now learning something about acoustics or even.... psycho-acoustics. Many of us at DIYaudio loudspeaker forums consider Toole's great book to be ESSENTIAL knowledge.

Ben

I did a lot of work on active acoustic absorption using an array of active transducers we invented for absorbing acoustic energy. I know a little about psychoacoustics, since that project and others involved noise abatement. I will try to get a copy of the loudspeaker book you referenced. I've been greatly interested in audio since the late 1950s. Just so you know.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.