Agony of tuning and tweakin'

:D I´ve found out that testing a room for its acoustic properties are more complicated than man could expect. But I will try to do it as visible as my previous threads has been????? Here is the link to where the hard work that was done by muscles, now's time to tweak the room!!! This thread are from scratch, but not long only 6 pages from start to end......ongoing acoustic tweakin´ I recommend you to read through, and also my post for ceiling panels; http://www.johnlsayers.com/phpBB2/viewtopic.php?t=7839 and my construction thread; http://www.johnlsayers.com/phpBB2/viewtopic.php?t=7182 We will have the first (very first practise) today, let me come back with my first impression and hopefully some values or trends. Cheers 8) 8) Kaj

Hi, Had a music session in the new rehearsal room, and it sounded so much better than previous room we used to have. The only thing I found out as a direct problem, was that electric bass on low open E string was filling the room more than desired. We moved the Bass speaker towards the big Bass trap and it improved a lot, but still not as tight as I would like it to be. We have not moved the bass amp around to more locations yet, but we will try it in four different corners and compare where the low E firming up, I knew that there was one of the modes at 70 Hz that would give problem but did not target on those in the Helmholtz absorbers as it is too low to be practically efficient. I took a few two mic recordings with my omni dynamic Zennheiser mics placed them 2/3rds down the length of the room and could be very happy to hear the balanced and detailed sound and the smooth treble from HH and Cymbals. My guitar (Variax through POD XT live and to PA) Bass through amp all recorded only through the stereo pairs, and it sounded like a lot of presence compared to earlier tests in previous rehearsal rooms. I changed my omni to Condencer mics phantom powered small capsule cardiod and placed them closer to the PA speakers angled towards Bass amp and drum kit, second recording session gave a more crisp presence of the drum kit, still >2m from the drum kit, so I can be confident that I can use the omni for adding ambience to the drums. Finally, did I hook up a Omni Condenser small capsule in the middle of the room and a cardiod condensor 1m from a PA speaker L+R room+speaker and compared the response, and it was fairly aligned. But I noticed the hump at 70Hz area, and thats my first tweak trouble and 141 Hz as well. I can move speaker/mic 1/4 of wave length and see if it is related to standing wave or bad resonance from PA speaker. My next move are to record a new test CD with the identified standing waves and non critical frequencies as reference, our PA is not so straight in frequency responce as I would like, but I will be able (I hope) to use the PA for a A+B comparisation at close up recordings of test signals, and at different distances to create the references of how much the room colour the sound. I want to digest my first impression and hopefully, get some questions and/or comments on what I have done so far. I will try to get a curve for each mic I use in comming test, but today was more a ear test, and it passed except for 70,141 Hz. And I will take pictures of Mic positioning and curves from that take. but today was it more fun just to play. Questions? Any thing I should go fore as priority? Cheers

Hi, I have tested the room for RT 60 and are happy :D , and as I mentioned in previous thread that I could hear a room mode :evil: around 70 Hz and it was confirmed, actually 68 to 96 Hz having a hump, unfortunately has the Peavey PA speakers also a hump in 60-80 Hz :twisted: when I measured it on close distance 25cm see pic and curve below. I believe that the low frequencies in the RT60 will drop if I make a third basstrap. I am not completed with my testing at all, I've just got a fingerprint of the room. I discussed with my mates yesterday and we decided to make a third basstrap at the entrance, and we will put more OC 705 type on top of the ceiling panels and start to measure again. This might take some time as I will soon be off for work! But I will try to get some more tests done before I have to go. I have some pics and curves, that I took yesterday. Cheers

Kai, are you using a flat frq response measure mic?

Ro, You can see the response curve for the microphone below. So I know what the mic is expected to coulor. I have only tested a few spots so far, but hopefully will I have a chans to get some of my friends to help with moving speakers, microphone and adding insulation and be quiet. Cheers

Okay, so did you see the little bumb at 70/80Hz? (well, actually it's a 2oct wide dip at 200Hz) hmm... You might wanna check for a measure mic, the Behringer ECM800. (http://www.behringer.com/ECM8000/index.cfm?lang=ENG) It'll be around 70 euros. It does the job properly.

Thanks RO for the tip, will go and buy one myself, coffe money 8) .

(well, actually it's a 2oct wide dip at 200Hz) hmm...

Not sure of what you aiming at, the curves do not indicate above 150hz, except the RT60. And I will test in more locations. One problem I have are the PA speaker (Peavey) they give a hump at 80hz, my plans are to take snapshots with 1/4 wave length for 70-90hz. And I will look for the hole at 200Hz :roll: Maybe I have to bring down another set of speakers for the measurment of the room only. Any good method on how I can measure my PA speaker with a minimum of room colourisation in my room, (not anechoic room)? Cheers

Kaj wrote:

Any good method on how I can measure my PA speaker with a minimum of room colourisation in my room, (not anechoic room)?

An open air test should do fine I think

Thanks Msikio, I thought about it as well, might be the best practise to do. Just the snag to find a space where we are that are quiet enough for a outdoor test, today also -10 degrees C, not very pleasant to test in that condition. I will wait abit more to see if there are any better way to get a test done of the PA speaker. If not, than I have to dress up for frost! 8) Cheers

Kaj wrote:

Thanks Msikio, I thought about it as well, might be the best practise to do. Just the snag to find a space where we are that are quiet enough for a outdoor test, today also -10 degrees C, not very pleasant to test in that condition. I will wait abit more to see if there are any better way to get a test done of the PA speaker. If not, than I have to dress up for frost! 8) Cheers

Acoustics is like wall painting, a summer activity ;)

Msikio, Agree about your philosophic conclusion 8) Just darn to long to summer :wink: I have ordered the Behringer ECM8000 today, will get it in three days so just to wait for that and I have thought a bit about speakers, I am just in the phase of buying a new house, and I will build a small home studio, a place to mix recordings in. So I might go to my local dealer and start to try different monitors that suit a flat response/transparent sound fingerprint. In that case will I have a few to test before I´ll find the right one. Anyone having an good advice on a studio monitor with known frequency response, that would fit the test of a 55m2 live room? Cross my fingers that my local dealer can provide for test only! Cheers