custom sub with heresy woofers

[abruzzi]

I have a couple of spare woofers that apparently came out of a Heresy II, and I was thinking it would be fun to make a subwoofer out of one or both of them. (my left/right channel speakers are also Heresy IIs.) I've never tried anything like this, and would love any pointers or starting points you might have in terms of enclosure, direction, using both drivers or only one, etc.

One specific question I had was wether I need to build a low-pass filter onto it, or if the LFE output on amps is already filtered?

thanks,

Geof

[Al Klappenberger]

Geof,

I did something similar. I put a K24 driver (of the Heresy II) into a ported box and paired it with a K55V and Beyma CP09 tweeter high end to make a set of speakers for my den / home theater. I found that it extended solidly down to 30 Hz. I would need to be driven by a mono amp and is rather large. It's the bottom half of the speaker in the picture.

Al K.

[MechMan]

While I'm sure you could build a cabinet to get that woofer to go down low...I doubt it would be a good candidate for a subwoofer. I think you would need more excursion.

[Al Klappenberger]

MechMan,

That speaker sure rattles my listening room! I suppose it would depend on what you want the sub to do though. If you already have a K24 sitting around, what have you got to loose?

Al K.

[Tom Mobley]

I think it depends on whether your sub is for music or for sound effects in movies. What works for one isn't necssarily the best for the other.

I've learned a lot about listening to bass since my son got a double bass. He had a 1/2 size, but the new full size is much better. Technically it's a 3/4 size, but real full size hardly exist, I guess. Open E string is 41 Hz, Khorns, Bells, LS and Corns don't seem to have any trouble going there. His electronic tuner seems to think it's going there OK. Calls it E1. Heresy doesn't want to go down there. I wonder why all these guys say LS cut off at 50 or 60? I realize it's a property of the horn design but IMO none of them struggle reproducing the lowest note my sons' bass plays. Corns do sound different from the horn loaded versions down there but it's not bad different, just different.

[Al Klappenberger]

Tom,

I agree totally! I have an LF-10 sub on my main system. It will go down to 20 Hz. On music I just don't need it. The Belles handle everything needed. All it seems to add is the thumping of dancers feet around the stage on live recordings of ballet music, for example. I suppose I should move the thing up to the den where I watch TV. but I would have to get the lead out of my butt to do that! I really don't have a good place to put it up there anyhow.

Al k.

[abruzzi]

My thoughts are to focus on LFE for home theater. Obviously 5.1/7.1 has a discrete LFE channel. If I focus it on sub for music, then I have to get signal out of the stereo signal. Maybe amps out there already do that, but if not, it becomes a more complicated electrical job. If it woks well for LFE, then I might noodle with the other usage.

And as some one else mentioned, I'm mostly doing this because I have the driver at zero cost to me. Is excursion the in/out displacement of the driver? What is the spec on the heresy woofer for that? Otherwise a 12" cone should be enough for a decent sub, and two 12" cones should be more than enough.

Geof

[Frzninvt]

The K24 only has an Xmax of like 4mm and it won't make a very effective subwoofer. You need to move air to make bass unless you can horn load it to keep the cone movement to a minimum. An isobaric enclosure might work but you would have to calculate the internal volume using the T/S parameters.

Best bet is to sell them and pick up a couple of Vifa 10" woofers P25W00 which are about $80ea and build an isobaric (clam shell/push pull) enclosure for them. They will extend easily to like 15Hz and the cabinet will only need to be around 1.5 - 1.75 cu ft total.

Al's K24 work's great in a larger ported enclosure but it is being used as a woofer and not a subwoofer. 30Hz is incredible performance for that woofer.

[Al Klappenberger]

Guys,

For whatever it worth, here's the measured performance of the woofer. It was done using the "close mike" technique. The markup job and comments were added by my late friend Mr "P" (Max Potter). The actual efficiency (sensitivity) is roughly 90 dB SLP at 1 meter.

The black trace is the woofer driver. The red one is with the mike right at the port. The summation was drawn by Max.

Al k.

[michael hurd]

A Heresy woofer isn't even remotely close to being useable for anything called a subwoofer, unless you are using it for a computer and it's literally 2 feet in front of you.

IMO, to get down cleanly to at least 20 hz at a decent SPL, you need a lot of cone area and excursion.

If your source ( CD etc ) has 20 db transients and you REQUIRE 90 db SPL at the listening position ( not enough for me ) you need the capability for 110 db + output at the listening position to be able to faithfully reproduce the signal. This is also assuming that nothing in the signal chain is rolling off, or otherwise compressing the signal from your AV Receiver etc to your power amp.