Hi all,
I have been working on an iPod docking boombox and need some help with the sound.. (I know some of you are anti-MP3, but well, it works for me..) The amplifier is a pair of Gainclone LM3875TFs that sound very good when connected to external speakers. The internal speakers just don't sound "right" with it.
I believe my problem drives from the drivers that I have which are less than ideal. They are Polk ex502a car speakers that I had laying around. 5.25" 4 ohm.
EX502a Car Audio Speaker from Polk Audio
I can't seem to find any of the box specifications for them, but that is most likely because they are designed for free air. The current enclosure has a 353.5 cu in volume per speaker and is sealed.
My options are to look for a decent 5.25" 8 ohm driver that will work with this size sealed enclosure (or smaller), or I can port it out the back. I would prefer something that can be easily found in the US and not too expensive as my wife is grumbling at what I have spent on it already..
I have included a picture so you can see the work involved so far. It is Birch/Mahogany construction.
Thanks in advance!!
I have been working on an iPod docking boombox and need some help with the sound.. (I know some of you are anti-MP3, but well, it works for me..) The amplifier is a pair of Gainclone LM3875TFs that sound very good when connected to external speakers. The internal speakers just don't sound "right" with it.
I believe my problem drives from the drivers that I have which are less than ideal. They are Polk ex502a car speakers that I had laying around. 5.25" 4 ohm.
EX502a Car Audio Speaker from Polk Audio
I can't seem to find any of the box specifications for them, but that is most likely because they are designed for free air. The current enclosure has a 353.5 cu in volume per speaker and is sealed.
My options are to look for a decent 5.25" 8 ohm driver that will work with this size sealed enclosure (or smaller), or I can port it out the back. I would prefer something that can be easily found in the US and not too expensive as my wife is grumbling at what I have spent on it already..
I have included a picture so you can see the work involved so far. It is Birch/Mahogany construction.
Thanks in advance!!
Attachments
I looked at the PDF 'manual' and didn't see any T/S parameters. Without that info, there is no way to guess what sort of ported box (if any) they might work in. And you are right in thinking that they are designed for IB use. I would expect that they have very little LF output in small, closed boxes.
My first move would be to try them in boxes w/o any back--cardboard would do for a trial run. If they sound better that way, then just cut off the backs of your existing boxes. You probably won't get much below 100 Hz, but they might sound better than you have now.
Good Luck,
Jim
My first move would be to try them in boxes w/o any back--cardboard would do for a trial run. If they sound better that way, then just cut off the backs of your existing boxes. You probably won't get much below 100 Hz, but they might sound better than you have now.
Good Luck,
Jim
I'd say find something that isn't designed for car use, with a low Qts.
Nice looking dock though.
Nice looking dock though.
Hmm.. I did make the backs removable in case those didn't work out so well, I suppose I could try taking them off. You are right the low end is very lacking and Polk has absolutely nothing for specs other than power handling and 4 ohm.
I looked at the Radio Shack one and I'm not sure I could make it fit without making a mess of the enclosures. Any ideas for 5.25"?
I looked at the Radio Shack one and I'm not sure I could make it fit without making a mess of the enclosures. Any ideas for 5.25"?
As an experiment, drill a series of 3/8" holes into the entire back of the speaker... then right up against this put at least an inch of medium to high dendity open cel foan or a chunk of 3 1/2" recycled cotton insulation. This makes the box aperiodic. Tune as required.
Might not be perfect, but enuff of an improvement to help.
dave
Might not be perfect, but enuff of an improvement to help.
dave
Sorry I havent posted results on this.. life has been pretty busy..
I tried the holes, and while it sounds slightly better, its still not what I want. The drivers seem to distort or sound fluttery with any lower frequencies, even at low volume. That leads me to believe that either they just stink or the amplifier is really having fits with a 4 ohm load. The same amplifier connected to a pair of old 10" Hyle speakers I have in the basement sounds very good to me, and although I don't expect the same volume or quality out of the smaller set I know it could be a lot better.
Having said that, I would like to find an inexpensive set of 8 ohm 5.25" full range or coaxial drivers to replace them with. If I need to port the box for this, it is an option as long as I can figure out the correct diameter/length of port.
I tried the holes, and while it sounds slightly better, its still not what I want. The drivers seem to distort or sound fluttery with any lower frequencies, even at low volume. That leads me to believe that either they just stink or the amplifier is really having fits with a 4 ohm load. The same amplifier connected to a pair of old 10" Hyle speakers I have in the basement sounds very good to me, and although I don't expect the same volume or quality out of the smaller set I know it could be a lot better.
Having said that, I would like to find an inexpensive set of 8 ohm 5.25" full range or coaxial drivers to replace them with. If I need to port the box for this, it is an option as long as I can figure out the correct diameter/length of port.
Visaton does things which will fit the bill.
Oops - just checked. They're 5", without the other 0.25". Would it be possible to make an adaptor to expand your driver choice?
Chris
Oops - just checked. They're 5", without the other 0.25". Would it be possible to make an adaptor to expand your driver choice?
Chris
Bah.. I wrote a reply but it didn't post for some reason..
A 5" might be ok, just larger than 5.25" wouldn't work so well. I need to be able to get it in the US, and not be too expensive.. 8 ohm as well..
Thanks again!!
A 5" might be ok, just larger than 5.25" wouldn't work so well. I need to be able to get it in the US, and not be too expensive.. 8 ohm as well..
Thanks again!!
Might want to have a look here.
http://www.diyaudio.com/forums/full-range/161967-looking-small-simpled-sealed-option.html
http://www.diyaudio.com/forums/full-range/161967-looking-small-simpled-sealed-option.html
You can always make a little suprabaffle (6" diameter circle that mounts to the current mounting holes and has the appropriate cutout for the new driver). You could put in a 4" TB, I think the Bamboo should be okay.
My first suggestion would be that 5-1/4 Vifa/Audax coax that parts express sells. Your box is still a little small for these, but perhaps now that its aperiodic it may work. These are 4 ohm though.
Good Luck,
Josh
My first suggestion would be that 5-1/4 Vifa/Audax coax that parts express sells. Your box is still a little small for these, but perhaps now that its aperiodic it may work. These are 4 ohm though.
Good Luck,
Josh
This looks decent, but I don't know where I could get it in the US..
Skytronic > 5.25" 100W Dual Cone Full Range Speaker 8 Ohm ONLY 6.56
Other than that, I think some 4" Tang Bands and make a ring to fit them in there. Either one I would probably make new backs for them to make it sealed again...
Skytronic > 5.25" 100W Dual Cone Full Range Speaker 8 Ohm ONLY 6.56
Other than that, I think some 4" Tang Bands and make a ring to fit them in there. Either one I would probably make new backs for them to make it sealed again...
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