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[Ivan Beaver]

All sub will exhibt a "power alley" effect.  This is due to the omni direction of those freq and the combining effect going on.  Try this to tame it down a bit.  Turn down 1 side 3-6db.  Only the people directly in front of one side may notice anything.  This will tame it quite a bit and give a much smoother lowend response overall the listening area.

Ivan Beaver

[Too Tall (Curtis H. List)]

Timmahh wrote on Sat, 02 April 2005 12:03

snip- I have Smaart on my laptop, but not sure if my mic input is stereo or not, dont think it is but. so my question here is what are you peeps useing to go from xlr for the RTA mic, to your laptops.  i ve looked at the m audio and the VX pcmcia card, but was wondering if there is anything else out there i should consider using befor making my final purchase. the Digigram VX card looks pretty nice.  i also see creative labs have made a pcmcia soundblaster card with a spdif and rca connections, anyone use this, it s price range is good at 130.00 or 80 for the usb breakout style box with a few extra connections. Snip-

Your on board sound chip needs to pass several tests.
First you need a stereo input.
If your laptop only has a "mic" input you need that to be true stereo. If it also has a "line" input you can ignore the mic input. It is unlikely you will use a mic that would work properly into it and many laptop mic preamps are garbage.

To tests for true stereo for either the mic or line input all you have to do is record a wav file and make sure you are only feeding one channel. Then play it back and see if the sound shows up on one or both channels or only the one you had the microphone hooked up to. Do the test for all inputs.

Next you need to be able to shut off any monitor signal at the output since this will cause a feedback loop.

To do this feed a signal into the input and record it to a wav file and while you are recording listen to the output. There should be nothing there. If there is you need to go into the windows mixer and choose "playback" under properties, then look for something that can shut off the monitor signal to the output. The wav output still has to stay on and turned up. If there is a master volume out that has to stay turned up. Everything else needs to be muted or turned down all the way.

Is your on board sound chip good enough for what you are doing?
If you bring it down to Bridgeport I can hook up a ESI U24 usb soundcard and compare it to the on board chip. I did that with the chip on my Thinkpad and it was very close to both my U24 and my Echo Gina pro card in my desktop tower. If drops off on the low end and I believe it has little more noise overall. For EQing a PA I would not hesitate to use it.

That said you can buy usb sound cards for cheap. I stay with usb soundcards because I don't like to tie up the pcmcia input. You can stack lots of usb on a hub.

In any case odds are you will have to use an external because the chip will not be Stereo full duplex.

You need to look at the mic you will buy, the mic preamp it needs and the external (or internal if you use it) soundcard all at the same time.

If you only spend $30.00 on a Behringer ECM8000 measurement mic it is foolish to spend the money for an expensive USBpre soundcard. You could buy a cheap USB card (if you need it) and a stand alone mic preamp for just over $100.

I'm including a zip file showing the comparison test I did comparing my Echo Gina 2x8 PCI sound card with the crystal fusion chip in my laptop and a iMIC that works with both Macintosh and PC (It is VERY cheap).

[John Roberts {JR}]

Ivan Beaver wrote on Sun, 10 April 2005 09:36

All sub will exhibt a "power alley" effect.  This is due to the omni direction of those freq and the combining effect going on.  Try this to tame it down a bit.  Turn down 1 side 3-6db.  Only the people directly in front of one side may notice anything.  This will tame it quite a bit and give a much smoother lowend response overall the listening area. Ivan Beaver

I don't have specific experience in this so I will phrase this as a question... Wouldn't that just skew "where" the power alley occurs? Unless you turn the second sub down so far it is not a significant sound source it seems it will have the capability to interfere.

What do you think about putting multiple subs together so their summation can be constructive?

JR

[Ivan Beaver]

Not so that I have noticed-the wave lengths are so large. I have gotten nothing but positive results.  By the time you get a small distance away, it starts making larger and larger changes in distance to notice anything. Think of it as using a single sub on 1 side to try to fill the room.  It will because it is generally omni.  However on the far side the level will be a little lower, due to the distance away from the "main" sub.  The one on the other side then acts as "fill" to overcome this loss of level.  Since the main sub is generating a decent level the extra sub just needs a lower level.  The problem does not go away, BUT is greatly minimized to the point of it-most of the time- not being a noticable problem.

In regards to the coupling.  That is always the best idea-espically for cabinets like the labs that really need it to achieve max low freq response.  The problem then begins where to put it.  If it is in the center of the stage, the seats in the middle suffer from an unbalancing of the mains/sub level ratio.  In the install world I like (if possible) to fly the subs.  This takes away the distance/level issue-however you no longer have the coupling to the floor to help.  It is all a series of compromises.  In the install world, even coverage is more important than punch factor.  Just make sure you have enough subs to do the job.

Ivan Beaver

[Timmahh]

Curtis, it only has a mic input, and according to the manufacturer it is only mono.  so it looks like pcmcia or usb. i ve been looking into the preusb from MAudio, as well as the Digigram VX440. both nice units. I see that Creative has also made a pcmcia soundblaster card but has no xlr availabilities, so i ll prolly stick with the preUSB or the Digigram card.

As far as mic, i ll be useing the DBX RTA mic. i bought one when i picked up the 260. so i ll want to stay near the top end for audio interface.

it has a realtek onboard so it is only so so.

I know Ken and I have been wanting to bring down the 4 v3s we have and stack them next to Al's and see what if any differances there really is. but now its getting to be the busy season, so hopefully we can itch out a few hrs one day to compare.
talk l8r.

[Too Tall (Curtis H. List)]

Timmahh wrote on Sun, 10 April 2005 16:39

Curtis, it only has a mic input, and according to the manufacturer it is only mono.  so it looks like pcmcia or usb. i ve been looking into the preusb from MAudio, as well as the Digigram VX440. both nice units. I see that Creative has also made a pcmcia soundblaster card but has no xlr availabilities, so i ll prolly stick with the preUSB or the Digigram card. As far as mic, i ll be useing the DBX RTA mic. i bought one when i picked up the 260. so i ll want to stay near the top end for audio interface. it has a realtek onboard so it is only so so. I know Ken and I have been wanting to bring down the 4 v3s we have and stack them next to Al's and see what if any differences there really is. but now its getting to be the busy season, so hopefully we can itch out a few hrs one day to compare. talk l8r.

The weather has been teasing us. I thought you might bring some of the top boxes too.

Just for the fun of it I looked for a suitable mic preamp on ebay. After about 5 minutes I found this-
M-Audio Audio Buddy Dual Mic Preamp W / Phantom Power

Item number: 7314426100

I bought a DBX 2-channel off ebay for about $75 to use with my laptop.
The DBX mic isn’t bad, but is most likely not a high end mic. It could be very close to the response of a B&K or Earthworks and STILL be the limiting factor in performance when comparing a USBpre to a less expensive external soundcard.

Take a look at the The M-Audio Transit

http://www.libinst.com/ESI_AUDIOTRAK%20CARDS.htm

With the audio buddy preamp and usb soundcard you have less then $200 invested that will do anything Smaart will ask of it while the USBpre costs THREE TIMES as much.

The big advantage for your purposes with the USBpre is that you have only one box to haul around instead of two. That and the fact that it is expensive gives it a high “toy factor”.


PS- Another reason I dislike PCMCIA cards is on some the cable harness attached to it stresses the card making a mechanical stress point for cable failure and torque on the card itself as opposed to a simple usb cable plugged in for a usb soundcard.