I am doing some fine adjustments to a three way conversion to an Optimus 10 1.7cf box that originally had an 8" driver, 10" passive, and the world's worst excuse of a tweeter. Doing well with the best cheapo stuff, GRS PF10-8 woofer, Goldwood GM85/8 midrange, and Goldwood GT510 silk dome.
I had some major baffle resonance problems in the low vocal and especially bongos. It's down to a minor one now. I had to make an 8" to 4" adapter because the midrange goes where the 8" driver was. Since it is hard plywood and it's size, it causes what I call bongo baffle.
Is there some way to carve out the rear of the adapter plate and maybe fill it with some putty like stuff the cure the bonk sound it resonates at ? Any tips for the pattern ? It is a luan plywood ring, 8" outside diameter and a 4" center hole.
I'm guessing offsetting the center hole could have reduced resonance.
Thanx for any advice.
I had some major baffle resonance problems in the low vocal and especially bongos. It's down to a minor one now. I had to make an 8" to 4" adapter because the midrange goes where the 8" driver was. Since it is hard plywood and it's size, it causes what I call bongo baffle.
Is there some way to carve out the rear of the adapter plate and maybe fill it with some putty like stuff the cure the bonk sound it resonates at ? Any tips for the pattern ? It is a luan plywood ring, 8" outside diameter and a 4" center hole.
I'm guessing offsetting the center hole could have reduced resonance.
Thanx for any advice.
Deadening the adapter plate can be achieved with bitumen sheet (sound dampening material used in car audio) or non-drying clay/putty material.
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However doing so may make the speaker sound dull / overdamped.
My gut feeling tells me you would be better off with a solid internal brace supporting the baffle adapter piece.
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However doing so may make the speaker sound dull / overdamped.
My gut feeling tells me you would be better off with a solid internal brace supporting the baffle adapter piece.
Good wrk zmyrna. From the beginning I thought it needed a horizontal brace across the middle of the cabinet. If I could connect my body to my brain, I would lay the speaker baffle side up, get some beach sand, then run my sweep generator through it as I sprinkle the sand on it. That as you may know makes Chladni patterns, these show the vibration modes of the cabinet.
Putting the horizontal brace across at the middle removed most all of the coffee can notes, the right one, done, is nearly clean across the spectrum, and the left, not done yet still has the obvious coffee can sounding peaks. It was sickening to me but I got a real treat in solving the problem.
You may like this, Vibrations of a circular membrane - Wikipedia, the free encyclopedia
And there are lots of videos on Youtube showing Chladni patterns in action. Worthwhile.
Thanks for the response.
Putting the horizontal brace across at the middle removed most all of the coffee can notes, the right one, done, is nearly clean across the spectrum, and the left, not done yet still has the obvious coffee can sounding peaks. It was sickening to me but I got a real treat in solving the problem.
You may like this, Vibrations of a circular membrane - Wikipedia, the free encyclopedia
And there are lots of videos on Youtube showing Chladni patterns in action. Worthwhile.
Thanks for the response.
The thing that got me was how the waves travel bounce back and get ya where ya least expect it. This GM85/8 did not give me such problems in a different cabinet.
From my studies, midrange can be very sassy, they make relatively low amplitude waves, but they are in a hearing band that most of the fundamental sounds are in, and it doesn't take much wave amplitude to get loud radiation.
These are made by a similarly stiff driver that is extremely tricky to simply tune out. I think I may try a magnet brace that prevents the whole mid driver assembly from possibly being the culprit by vibrating back and forth on the motor axis.
Probably another reason commercial speaker mfgrs avoid three way's. The two way's bass driver eats up most of the baffle space and doesn't leave much open area to resonate.
I'm down to only a few pulsed honks now. Maybe even the cheapo stamped woofer frame with no anti-resonance stamping architecture.
Nice looking speaker danny, I wish I could afford such a project.
From my studies, midrange can be very sassy, they make relatively low amplitude waves, but they are in a hearing band that most of the fundamental sounds are in, and it doesn't take much wave amplitude to get loud radiation.
These are made by a similarly stiff driver that is extremely tricky to simply tune out. I think I may try a magnet brace that prevents the whole mid driver assembly from possibly being the culprit by vibrating back and forth on the motor axis.
Probably another reason commercial speaker mfgrs avoid three way's. The two way's bass driver eats up most of the baffle space and doesn't leave much open area to resonate.
I'm down to only a few pulsed honks now. Maybe even the cheapo stamped woofer frame with no anti-resonance stamping architecture.
Nice looking speaker danny, I wish I could afford such a project.
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Thanks.
For damping of the mid cabinet I used Twaron Angel Hair, about 5 gram/liter,
it's very effective, much better than sheep wool.
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I'll consider a build like that, the idea of separate resonators has tempted me for years. I always seem to build things as cubes. That RefSpeaker design , in addition to acoustical function, discourages stacking anything on top that might fall and puncture a driver.
It will be much easier to take a separate cavity and modify it.
It will be much easier to take a separate cavity and modify it.
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There are some CD's I have that really test a speaker's quality. Mostly female lead singers in clean mastered and mixed productions.
The Best of Sade # EK85287. Her voice carries a strong midrange and can bring on some nasty resonances on a bad build. The percussion is a good test for transient response. And the deep bass can really trash a sloppy woofer. There are lots of nice clean cymbal taps to test for that. Thanks to her and her band, I have tweeked for some really natural sounding cymbals and chimes.
Nora Jones can really thrash a midrange driver, and about the worst is Linda Ronstadt on Phillip Glass's 1000 Airplanes CD. I think she can break a glass, her Therimen-Like vocals were really torturing the woofer, mid, and tweeter.
Now I almost make it all through the above mentioned.
The Best of Sade # EK85287. Her voice carries a strong midrange and can bring on some nasty resonances on a bad build. The percussion is a good test for transient response. And the deep bass can really trash a sloppy woofer. There are lots of nice clean cymbal taps to test for that. Thanks to her and her band, I have tweeked for some really natural sounding cymbals and chimes.
Nora Jones can really thrash a midrange driver, and about the worst is Linda Ronstadt on Phillip Glass's 1000 Airplanes CD. I think she can break a glass, her Therimen-Like vocals were really torturing the woofer, mid, and tweeter.
Now I almost make it all through the above mentioned.
Going with separate cabinets for the woofers and mid/highs is very effective to suppress resonances.
Also the mid/high cabinets rest on soft rubber feet to decouple from the woofers.
If I play loud bass I feel the woofer cabinets vibrating but the mid/highs are dead.
To get the same effect in a one box speaker you need panels of 40-60mm thickness and plenty of bracing, that's very very heavy.
If the footprint of the cabinet is large and heavy enough then they want fall that easy, my mid cabs have a footprint of 33x40cm and weigh about 20kg: it takes some effort to move them
Another option would be the use of anti vibration rubber isolator bolts between the cabinets.
Also the mid/high cabinets rest on soft rubber feet to decouple from the woofers.
If I play loud bass I feel the woofer cabinets vibrating but the mid/highs are dead.
To get the same effect in a one box speaker you need panels of 40-60mm thickness and plenty of bracing, that's very very heavy.
If the footprint of the cabinet is large and heavy enough then they want fall that easy, my mid cabs have a footprint of 33x40cm and weigh about 20kg: it takes some effort to move them
Another option would be the use of anti vibration rubber isolator bolts between the cabinets.
Some recordings are somewhat out of balance to begin with. Sometimes these will need a well balanced speaker not to exacerbate them but on the other hand they don't make a good reference for changing the speaker.
Sometimes the better reference is a good clean recording so you can tune until they sound natural and as you get it right, other recordings will begin to fall into line. Don't use a recording of the kind which sounds good on just about any system though. Clean vocals are good.
Sometimes the better reference is a good clean recording so you can tune until they sound natural and as you get it right, other recordings will begin to fall into line. Don't use a recording of the kind which sounds good on just about any system though. Clean vocals are good.
What I meant by falling, danny, is leaving things like scissors on top of a big flat box. They might vibrate off and stick in a driver, or some object could. The Starfighters discourage usage as a shelf.
I finally got the cabinet vibs as controlled as reasonable expected, but the closed back GM85/8 still had some resonances and timbre that mainly showed up at high volume. So I cut the GM85/8 midranges to open back style. And then mounted a salsa bowl to the back of the midrange. I did stuff some no itch fiberglass, a light fluffy cap on top of a thin but dense shell pack.
Did the trick, now it is acceptable on resonance, but I do notice a slight bit of distortion, as would be expected with such a cheap $10 midrange.
The bowl : Good Cook Large Salsa Bowl, Red: Kitchen & Dining : Walmart.com
I finally got the cabinet vibs as controlled as reasonable expected, but the closed back GM85/8 still had some resonances and timbre that mainly showed up at high volume. So I cut the GM85/8 midranges to open back style. And then mounted a salsa bowl to the back of the midrange. I did stuff some no itch fiberglass, a light fluffy cap on top of a thin but dense shell pack.
Did the trick, now it is acceptable on resonance, but I do notice a slight bit of distortion, as would be expected with such a cheap $10 midrange.
The bowl : Good Cook Large Salsa Bowl, Red: Kitchen & Dining : Walmart.com
Ok, did some listening and it was worth the effort. I will probably not use a sealed back mid driver again. It had a sort of pleasant muted sound but had seriously objectionable resonant spots. Take Sade's Smooth Operator. Wen she sang the words smooth operator, it trashed the closed back. Gets through it like silk now.
So I cut the drivers open on three sides, installed a thick plastic bowel packed as above with no-itch fiberglass. The bowel is a bit larger than 1/2 of a large coconut. Speaking of that, I'll bet a coconut shell would make a nice midrange chamber.
I would not pack a vented cabinet with ANY type of fiberglass.
So I cut the drivers open on three sides, installed a thick plastic bowel packed as above with no-itch fiberglass. The bowel is a bit larger than 1/2 of a large coconut. Speaking of that, I'll bet a coconut shell would make a nice midrange chamber.
I would not pack a vented cabinet with ANY type of fiberglass.
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