Custom Heresy center channel

[tony61]

O.K., I'm wanting to build a custom center using Heresy parts and I don't have a clue. What I want to do is put a woofer on either side of horizontally mounted mid and high horns in a cabinet grade birch plywood enclosure.

I have a type E crossover, a type TH-SR3 crossover, a K-22E woofer, a K-24 woofer, two K-79K tweeters, two K-53K mid's and alot of ambition.

My questions are these: With these parts, is it possible? Which crossover do I use? What modifications do I have to do to the crossover?

The enclosure will have a brace on either side of the horns which will effectively create a seperate chamber for each woofer and the horns.

I'm going to port the enclosure in the back behind each woofer as well.

Thanks for the input.

My H/T

Yamaha HTR 5280

Mains-'86 Lascala's

Rears-'86 Heresy HBR's

Center-KG-4 of unknown origin

Subs-(2) Yamaha YST-SW160's

[JohnA]

You need 2 of the same woofers.

You also need a crossover designed to be used with the Heresy II squawker and tweeter. A Type E might be usable, but we have little hard data about the HII components in order to make recommendations.

With 2 woofers, the bass output goes up 6dB and the effective impedance goes down to half. You will have to modify the crossover woofer low-pass to account for the lower impedance and to increase the output of the squawker and tweeter. With schematics and more data we might make specific recommendations.

My brother is doing the same thing you want to do with HI components and Focal(?) woofers. It will have the proportions of the HF horn section of La Scalas.

[STL]

If the woofer was originally designed for a sealed box then porting it is a bad idea. You can't just port a speaker because you want to (and expect to get good results). The speaker specs (specifically Qes and Qms -- or it's overall Qts) define whether it will work port or sealed enclosure.

If you decide to use two woofers I would also suggest they be exactly the same driver. You could wire them in series (which will double the effective impedance) instead of parallel (which halves the impedance). Using a series wiring should better split the power between the two woofers and allow the overall output to remain closer to constant (instead of raising it 6dB). Either way, you are going to need to make a crossover change -- and that very likely will not be as cut-and-dry as building the rest of the speaker.

[tony61]

Gentlemen I really appreciate the input. Where do I go from here?

As soon as I can find one, I'll buy another woofer (either a K22 or a K24) to match.

In regards to the crossover mod's, what do you suggest? Would Klipsch be of any assistance? They have been very helpful in the past. Or, perhaps someone on this board would like to offer their assistance in a "hands on" fashion.

[j-malotky]

Tony

Look in the update section. Hwatkins just built a Heresy center with some help from Trey if memory serves me today. Used two smaller woofers instead of the 12".

Send him a message, I bet he would share his data with you.

JM

[hwatkins]

Hello Tony

I have made a modified Heresy (I) center using two Fostex smaller woofers - mine is low profile. If I had the headroom I would have done what you are doing. Regarless, the woofer-tweeter over squawker-woofer really widens the sweet spot for center information and is a quality performer for HT and music. I like it much better than the single heresy I trialed for a bit.

John Albright has it right on the Xover - the type 'E' is specific to the K77 and K55 drivers (I can't recall if there is a significant issue with the woofers) and would have to be modified to work best with the HII stuff you have. Trey Cannon with Klipsch should be able to help identify the Xover for your HII parts. Al K could give you great help if you modify the Xover - the man has it down on the electronics.

STL is also right about the series wiring. If you keep HII speakers and Xover you will probably be able to do some small in line modifications to a series wired woofer to even it out. For mine I went parallel - smaller cones needed this to get a closer match to the T/S parameters of the K22 the Xover was built to manage.

Trey Cannon can get you the T/S (Thiel/Small) measurements for the woofer you go with. With these parameters you can use a couple of free (or near free) design programs to size your box. You can also simulate the frequency response of series and parallel wiring, and venting or sealed. You are only concerned about the woofers since the horns are separately sealed devices.

In all cases you need to get an idea of what your internal volume of the box - be sure to exclude the space occuppied by braces, horns, drivers, xovers,etc. The T/S parameters are part of the basic info needed for design software. The programs are Unibox (great tool, but you need to get some education about what it does and what you can change), WINISD (which does a great job of the 'golden rule' box size calculation - you supply the internal volume and two of the dimensions -length, width, height- and it gives you the best third dimension to minimize box resonance) and Boxplot (a smaller tool that is quick and accurate). Search through google and you should be able to find these. I manually spot tested each of these programs calculations and compared them to each other to get confidence in their results.

Be careful - this speaker building can get addictive. Just started a Pi Speaker project. The next will be a wooden horn project - Darn if I ain't sick...