How do crossovers work?

[dtr20]

I have a bunch of ideas that I want to try with building my own speakers. I have a pair of h700s from 1969. I was thinking about doing something like a tangent 400 which uses heresy ii parts with a lot more bass. My question is, do I need to change the crossover? The heresy cuts out at 50hz. Is that because of the cabinet or the crossover? Will the bigger/ported cabinet dig deeper in bass with the stock crossover? 

Edited August 1, 2016 by dtr20

[Coytee]

I don't know much about crossovers other than their intended purpose so discount what I say appropriately.

 

Why not get an active crossover?  This way you can tinker until you get it right without trying various recipe's and having someone OCD saying that you need a better cap or something in there.

 

Of course, they might poo-poo actives.... but it will allow you to adjust as you want on the fly.

 

 

[dtr20]

44 minutes ago, Coytee said:

I don't know much about crossovers other than their intended purpose so discount what I say appropriately.

 

Why not get an active crossover?  This way you can tinker until you get it right without trying various recipe's and having someone OCD saying that you need a better cap or something in there.

 

Of course, they might poo-poo actives.... but it will allow you to adjust as you want on the fly.

 

 

I don't know anything about active crossovers. I feel like that is an entirely different rabbit hole to venture down and could get dangerous.

[Ski Bum]

Low end extension is all the drivers and cabs.  The networks would only cut higher frequencies from the woofs.  

 

Do the Tangent cabs normally come equipped with the same woofer as the ones you'll be using?  (Too lazy to look myself)  Woof's t/s specs dictate cab parameters.  If they're in fact not the same drivers, you may want to model this to see if it's worth pursuing.  

[WMcD]

In the typical bass unit, Iike the H, the part of the crossover circuit driving the woofer lets everything below 700 through and then rolls off freqs above that.  It is a low pass filter.  It "works" because the components are in series electrically with the woofer and above 700 Hz starts working like an open switch, gradually, as freq increases.  The filter does not affect freqs below 700 Hz.  It I not causing deep bass roll off.

 

The design of any box is what can enhance bass to a limited extent at low freqs.

 

WMcD

[dtr20]

2 minutes ago, Ski Bum said:

Low end extension is all the drivers and cabs.  The networks would only cut higher frequencies from the woofs.  

 

Do the Tangent cabs normally come equipped with the same woofer as the ones you'll be using?  (Too lazy to look myself)  Woof's t/s specs dictate cab parameters.  If they're in fact not the same drivers, you may want to model this to see if it's worth pursuing.  

The tangent 400 uses heresy II drivers/crossovers.  I have h700s (heresy I, essentially).  I do not know how to "model" this,  I don't even know what that means.  Does it have something to do with software?

[Skelt]

I wanted to put a Heresy 3 conversion into my T-400s but ended up in another direction. Now they are more like a KLF30 variation.

[Ski Bum]

17 minutes ago, dtr20 said:

The tangent 400 uses heresy II drivers/crossovers.  I have h700s (heresy I, essentially).  I do not know how to "model" this,  I don't even know what that means.  Does it have something to do with software?

Ok, you're just fine with that (Klipsch has already done the modeling for you when they developed the product).  Modeling simply means calculating the low end response based on driver t/s parameters and the specifics of the cab, and yes, there are programs for that.

[derrickdj1]

A larger cabinet will have some lower extension at the cost of a few db higher up in the passband.  Most of the time it will not change the sound dramatically with the lost of a few db. higher up or the lower extension.  The question is what is the intended application.  If this is mostly for music, you may not needed it unless listening to some classical music with things like the pipe organ.

 

Active XO are really fairly easy to learn.  Something like an I Nuke DSP amp or a Mini DSP let's you pick the XO and appropriate slop at the touch of a finger and be done.

[dtr20]

I want to make something like a tangent 400 cabinet. I'm planning on trying the ports on the rear panel at first for trial. I was also thinking about putting a rear passive radiator instead of ports to see how that sounds.

[Skelt]

I went down that road a few years back. If you are set on using the H700 horn then why not build a Forte 1 instead of a T-400?  They have similar cabinet size and the xos are not too different. IMO a Heresy II xo sounds better than a Forte xo in a Forte cab. You can still play with porting and have a ported Forte. (did that one too)

 

 

 

 

[dtr20]

Does anyone have plans to the tangent 400 or the forte cabinets? 

[Marvel]

A friend of mine has Tangent 400s. I had, and lost, all the dimensions, but could get them again for you.

 

Bruce

[dtr20]

Cool, thanks

[JohnA]

On 8/1/2016 at 7:53 PM, dtr20 said:

The tangent 400 uses heresy II drivers/crossovers.  I have h700s (heresy I, essentially).  I do not know how to "model" this,  I don't even know what that means.  Does it have something to do with software?

 

Your job will be much easier using a program like Bass Box.

http://www.ht-audio.com/pages/BassBoxPro.html

Part Express

 

The crossover does not normally affect the low bass of a home speaker.  That is determined by the woofer and the box size.  Still, the woofer has limits and may not be able to go deeper in a larger cabinet, or may have ripples in the response curve in an oversized cabinet.  That is the case for the Heresy I. 

 

Many woofers can pick up an extra 1/2 octave of low bass in a larger, ported cabinet, but you must protect the woofer from over excursion (filters, less power).  An alternative I like is a passive radiator.  It works like a port, but limits woofer over excursion.  It adds complication to the design/model, too. 

 

To your original question, crossovers add resistance (Impedance, technically) as frequency changes above or below their design point.  For a woofer the low-pass filter adds increasing resistance as frequencies rise, choking off the woofer's output at higher and higher frequencies.  A high-pass filter for a tweeter works in the other direction choking off lower frequencies and protecting the relatively fragile tweeter from bass notes. 

 

If you use all the same drivers in a larger box, you will not likely have to change the crossover.  However, you may want to if the driver are placed much higher above the floor and you get cancellation from floor reflections. 

 

Reading for a rainy day: http://www.classicspeakerpages.net/library/allison/allison_one_series/allison_one_series_brochure_2/allison_one_series_brochure/