Need help with 5.25" driver for sealed enclosure

MrDragon1 · 5th December 2009, 01:39 PM

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!!

Jim Shearer · 5th December 2009, 03:59 PM

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

chris661 · 5th December 2009, 08:31 PM

I'd say find something that isn't designed for car use, with a low Qts.

Nice looking dock though.

pboser · 5th December 2009, 08:50 PM

How about the old Radio Shack 1354 drivers?

MrDragon1 · 5th December 2009, 10:10 PM

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"?

planet10 · 5th December 2009, 11:48 PM

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

MrDragon1 · 20th February 2010, 04:01 PM

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.

chris661 · 20th February 2010, 04:49 PM

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

MrDragon1 · 28th February 2010, 03:14 PM

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!!

mashaffer · 28th February 2010, 05:13 PM

Might want to have a look here.

looking for a small simpled sealed option

5th December 2009, 03:59 PM	#2
Jim Shearer diyAudio Member Join Date: Jun 2007	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 __________________ A day without music is like a day without food.

5th December 2009, 08:31 PM	#3
chris661 diyAudio Member Join Date: Feb 2008 Location: Lancashire Blog Entries: 7	I'd say find something that isn't designed for car use, with a low Qts. Nice looking dock though. __________________ "Throwing parts at a failure is like throwing sponges at a rainstorm." - Enzo My setup: http://www.diyaudio.com/forums/multi...tang-band.html

5th December 2009, 11:48 PM	#6
planet10 frugal-phile(tm) diyAudio Moderator Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 4	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 __________________ community sites t-linespeakers.org, frugal-horn.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA

20th February 2010, 04:49 PM	#8
chris661 diyAudio Member Join Date: Feb 2008 Location: Lancashire Blog Entries: 7	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 __________________ "Throwing parts at a failure is like throwing sponges at a rainstorm." - Enzo My setup: http://www.diyaudio.com/forums/multi...tang-band.html

28th February 2010, 05:13 PM	#10
mashaffer diyAudio Member Join Date: Jun 2004 Location: Indiana	Might want to have a look here. looking for a small simpled sealed option __________________ mike - www.keepingsundayspecial.org


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5th December 2009, 08:50 PM	#4
pboser diyAudio Member Join Date: Jun 2004 Location: NJ, USA	How about the old Radio Shack 1354 drivers?

5th December 2009, 10:10 PM	#5
MrDragon1 diyAudio Member Join Date: Oct 2009	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"?

20th February 2010, 04:01 PM	#7
MrDragon1 diyAudio Member Join Date: Oct 2009	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.

28th February 2010, 03:14 PM	#9
MrDragon1 diyAudio Member Join Date: Oct 2009	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!!

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