retro.addict - 2008-10-15 07:30
...it's a question I really want to know the answer to, so I can try to reverse the effects and make the bass 'fly out the front of my GF-9000' instead of being wasted.
Can anyone answer this, and suggest ways (other than adding foam) that I can try, which will make the bass 'fly out the front of the box' so I can hear it?
Thanks.
geoffhartwell - 2008-10-15 08:00
thats a good question RA, was thinking of doing something with my crown 5100 to try and improve the bass
^ I always thought that the Lasonic TRC-931 and Crown SZ-5100 were the same boxes rebadged. When you posted about your new Crown, I did another search on it and noticed the handles are VERY different!
geoffhartwell - 2008-10-15 08:28
i thought about making some custom boxes to fit inside (from ply) but it would make it far to heavy and the casing might split with the extra weight, so i could make them from polystyrene or some thin plastic sheeting
Polystyrene, that's an idea.
I've fitted some foam to my GF-9000 but not put it back together yet, as I'm bleaching the woofers while it's apart!
I've taken some pics which I'll be getting ready for Gluecifer in the next few days.
geoffhartwell - 2008-10-15 08:38
i'd like to see them pics to, let us know how it sounds when you done
OK Geoff, I'll post them on the forum for anyone who's considering fitting foam to one of their boomers. I put the GF-9000 back together when I'd done one side, but I don't think it made any difference to the sound. See what happens when I put it back together tonight with both sides done...
Maybe try installing a thin gasket around the speakers? Should help cut down on vibration too.
i belive that why the boxes are open in the back is to keep some air flowing for the electronics remember you have a heat sink for your amp which after awhile of playing gets a bit hot, so the air movement of the speakers keeps everything at bay..if you notice lets say a kaboom has sub and the speakers are sealed but notice it has a port for the speakers to breath and the amp is at the back exposed to the outside air, there are a few boxes that are sealed ie the pioneer sk-900,808,aiwa 880 they have passives and the amps are away from speakers at least the pioneer has an opening on the top left corner for air to flow in the aiwa does not but there are openings in the front that helps..
Good Luck R.A.!
I actually am losing a bit of faith the the foam method myself, I briefly tried it with my RISING last night, just for an experiment, and it made very little difference to the sound. But with my 777 it improved the audio a massive amount.
Perhaps theres a science equation here, with foam density versus empty space in the box versus speaker range/power?
I'm with you on the ventilation Ramon, I'm always sure that theres a decent amount of airflow still and tested my 777 intensively when I 'foamed' it.
Really need to get some Dyn-a-mat to try, but will keep my fingers crossed for a good result with R.A.'s 9000!
Rock On.
I understand what it is you want to do but I don't think that's a good idea!
You'll be turning a bass-reflex speaker design into a sealed-box configuration like the i931 - therefor possibly giving the box a "hollow bass" sound.
Still, if your experiment works, be sure to let us know!
Good point.
It happened to me to. Lots of bass comes from the back.
Seeing the older boxes, I noticed that they don't have the resonence issue, and I guees that early 70's plastic was to hard, in that way the enclosure can't vibrate and hurt bass perfomnce. It's clear that not much bass, but great definition.
My fisher PH470, wich has plenty of power, tends to vibrate at high volume. You can't put the bass control over 70%.
But the BBX is big, and plastic not too hard.
Fooaming is the way to reach the "infinite" cabinet speaker design. I think that once you have fomed the BBX, bass definition would improve dramatically. But I'm not sure if you will get more bass ... since if the BBX was well desgined the cabinet most be tuned in some way in order to improve the low freq. cut (forget about definition, but kicking) .. and foaming would prevent the tunnig effect working
One way to cheat this is with some kind of equalization or filter.
I remeber playing with the RX-C45 eq. to cancel the cabinet resonance ... It really worked for me. If you don't have an eq, you still cand add some filter in the signal path, but that shiled lots of work ...
Okay, I did it, and it's back together now. The foam hasn't improved the 9000's bass. It sounds different, but I'm not really sure how. The highs seem clearer, and the midrange seems reduced. The bass is about the same, but I have to say it has a hollow feel about it. I'm not sure which way I liked it best, with or without foam. Probably without, since it sounded more 'open'. I'm leaving the foam in there though, since I spent so much time cutting and fitting it!
Working on the 9000 gave me an excuse to clean it more, and I've had the chrome woofer trims off and cleaned the dust from behind them. It looks a even more sparkly and blingy now!
I did behind the tweeter grilles too. I'll post pics of the foaming job tomorrow.
I think you may be assuming much more acoustic designing was done than actually happened on these boomboxes. For the vast majority of 1pc boomboxes from the 70s & 80s they simply put the speakers in the plastic box. Holes were put in the back to keep the electronics ventilated.
I suppose this is a bass reflex design on it's most basic level - that is, holes in the back of a speaker enclosure so that placing it in a corner will reinforce the bass output.
Making the boombox cabinet a sealed enclosure will change the sound, but whether it improves things will depend on so may variables it's best just to try stuff & see what happens. Sealing the cabinet properly will be very difficult (all those holes for switches, etc.) & may be a bad idea for the electronics inside.
The most effective reported improvements in sound have been when drive units are replaced. Especially in the speaker boxes of 3pc boomboxes - usually when the originals are rather weedy.
Presuming you don't want to replace the speakers in your GF9000, I think the most effective way to improve it's bass output is placement. Try putting it in a corner where two solid walls meet, or inside an open fronted cabinet. You need anywhere where the sound coming out of the back will get reflected back rather than allowed to dissipate.
Amongst the worst places would be laid back on a sofa or easy chair which will soak up all of that bass.
Try both of them & see the difference for yourself.
My original experiment with the foam was just to stop some of the rattles inside my 777, but it also improved the sound a great deal much to my surprise, but my 777 is heavily cusotmised, so theres a good chance a factory original wouldn't get the same (or any!) improvements. I really agree with Isolator42 in that theres so many variables from box to box that it's not going to improve every box, but it's worth experimenting with if you don't particularly like a box's sound, you never know and it's easily removed if it's not to your satisfaction.
I'm still reasonably convinced though that a more professional form of audio dampening inside a box will generally improve it's sound, and I think the bigger and more hollow space is inside it the more the improvment will be. But that get's back to R.A.'s point that the foam muffles the sound and 'closes' the box up a noticible amount that reduces the openness of the sound. And exactly like he said it affords different ways you can enhance a box's sound. I found that my 777 lost it's hollow bass and it took on a much more warm and balanced sound that blended the speaker separation much more pleasantly to my ears.
I'm going to try doing this my JC-2000 at some stage, as she rattles like theres no tomorrow at most volumes. But I'll wait till I get some of that dyn-a-mat stuff so I can try both methods and see how great a difference there is.
Looking forward to seeing your hot pix R.A.!
Rock On.
quote:
Originally posted by isolator42:
I think you may be assuming much more acoustic designing was done than actually happened on these boomboxes. For the vast majority of 1pc boomboxes from the 70s & 80s they simply put the speakers in the plastic box. Holes were put in the back to keep the electronics ventilated.
I suppose this is a bass reflex design on it's most basic level - that is, holes in the back of a speaker enclosure so that placing it in a corner will reinforce the bass output.
Making the boombox cabinet a sealed enclosure will change the sound, but whether it improves things will depend on so may variables it's best just to try stuff & see what happens. Sealing the cabinet properly will be very difficult (all those holes for switches, etc.) & may be a bad idea for the electronics inside.
The most effective reported improvements in sound have been when drive units are replaced. Especially in the speaker boxes of 3pc boomboxes - usually when the originals are rather weedy.
Presuming you don't want to replace the speakers in your GF9000, I think the most effective way to improve it's bass output is placement. Try putting it in a corner where two solid walls meet, or inside an open fronted cabinet. You need anywhere where the sound coming out of the back will get reflected back rather than allowed to dissipate.
Amongst the worst places would be laid back on a sofa or easy chair which will soak up all of that bass.
Try both of them & see the difference for yourself.
