ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hi all,I've purchased some 5702's, replacement ABR's (well newer versions), updated capacitors and I've got to work. Damage is about £220 so far. The ABR's are newer KEF BD139's. These are lighter and perhaps slightly smaller. They are slightly different in design but fit ok with just a tiny bit of silicon required.The electrolytics all registered in spec but I'm changing them anyway. No issue with mid or treble - very, very good.The bass however I don't know, it's all there I can play a sine wave down to 35Hz but with music it lacks raw energy, like there's something missing. The finest speaker bass wise I've ever owned were Pentas and these 5702's can't match them. This I find surprising because the cabinets are so large and so heavy. I wonder if the slightly different ABR is to blame but to be honest the sound isn't much different with the ABR missing. I also noticed the internal baffling material is a complete mess without any real structure. Does anyone know if when using an ABR the space should remain clear as with a ported cabinet, or should I stuff it? It's certainly not stuffed at the moment - oddly much of the stuffing it compressed into the space to the right of the crossover board - weird!Amp is a Class D 100W custom build baed on TDA7498 - plenty of grunt - no problem there.Thoughts on the bass?Andrew
That sounds (pun intended) how I find mine, there's just something not right with the bass despite the fact the range is there. I also have mine on stands and away from the wall so I'll try that first.Did you find the baffle helped one way or the other?Regards,Andrew
Looks good Peter, obviously mine have different ABR's but the same principle and surface area I think.At least the mid range and treble is excellent - walks all over my Q Acoustic 3050 floorstanders and they are very highly rated.
The ABR is the problem, in fact if you press and hold it in to prevent movement you can hear the bass improvement. I'll knock up some wood inserts to block it off and see how it sounds.Andrew
Peters seem to be Beovox 5700 rather than 5702.
Martin
If the ABRs, also known as passive radiators, are not the same compliance and mass as the originals the low frequency response will be different. The compliance and mass are used to tune the cabinet/woofer combination, in the same way the diameter and length of a traditional port is used to tune a bass reflex speaker. You might try adding additional mass to the ABR if you think the one you replaced the original with is lighter, but by weight/mass I mean the suspended part of the ABR, not whether it's lighter or heavier due to the weight of the frame. Hard to really weigh though.
Without knowledge of how it was tuned, and instrumentation, it's hard to do this quantitatively though, so by ear would be the approach I guess. Mainly you need a frequency sweep and a way of reading the impedance of the speaker system in the bass range. A "Woofer Tester" from Parts Express is a very easy way to do this, I love mine, a truly excellent piece of speaker building/testing kit.
Jeff
I'm afraid I'm recovering from the BeoVirus.
Hi Jeff, good points.I believe the mass is the equivalent, the units were all classed as BD139 but the chassis looked to be forged than cast to save on cost (the original is a big chunk of aluminium) and rubber instead of form for the surround.
Replaced the mid-range capacitor, so it and the treble are done - outstanding mid and treble from those Celestion drivers, among the best I've ever heard - lovely!Improved bass by moving all the baffle material to cover the walls rather than the mess it was in. In parts of the cabinet (behind right of crossover being one) it was stuffed solid so that no air could move. The bass improved a bit after that, but not quite there just yet.I confirmed the B139 oval and non-oval have the same surface area and weight (the frame isn't as large is all). Listening to the bass it's evident the ABR needs a bit more weight behind it. The B&O calcs were wrong for the driver/cabinet volume. Will get a bunch of magnets, bump the weight and report back the amount for others.A.
Couldn't get used to the ABR's so they had to go. I made some templates and a 67mm hole for an adjustable bass reflex port. Even without the port the bottom end (all of it under about 200Hz) is better - more tight and controlled. I'm pretty close to having what I consider to be the perfect home speaker, nothing I've heard yet beats those Celestion's and B&O nailed the crossover. The Philips bass is a seriously good unit as well it's just a shame the cabinet/ABR values are all wrong and mess it up. Andrew
Here's my final solution. It's took a bit of time to get it sounding great, but great it sounds. In fact, it's become the finest sounding speaker I've ever heard, volume withstanding more involving than the Beolab 5 and 9. The mid-range and upper is truly bliss like nothing else I've heard and the bass is now up to modern standards. I've tested it down to 25Hz with linux alsa speaker-test!1. remove most of the sound dampening material. B&O did a cracking job bracing the cabinet and deadening waves using a small baffle around the panels so it's not required, at least not in the volume it comes in. Removing it increases the cabinet volume and increases low end volume. I left a little bit of the less dense multicoloured stuff in the bottom and a little bit here and there but the majority I took out.2. I tried porting using a 74mm hole and a large adjustable port. After much testing I found it wasn't big enough, despite being one of the biggest ports I could find. I then stuck in a 38mm hole and bingo, it was almost there. The port which I'd cut down to a nearly useless 5cm was then removed. You should be able to work out the surface area for one hole using both those diameters.All caps were replaced with audio grade polys.
Should be the same measurements for 57000/5702. Make sure you have a really good amp and source as you can hear everything with this setup.Andrew
A frequency sweep could be interesting to see.- And do put new dustcaps on.
Shouldn't be a problem, I have an oscilloscope and a mic somewhere around here.The original dustcaps are porous I take it given they dissolved? I did see a guy in Netherlands selling them but I'm pretty sure he's bought them on aliexpress and stuck the Beovox 570x label on them.A.
A few updates.I was still not quite happy with the sloppy bass, there was just something not quite right with it, so I threw the old philips drivers (tried new woofer caps, no difference) and fitted modern Celestion BL10-100X 8ohm.These are slightly more efficient necessitating a tweak to the crossover. For the 5702 this is simple, there's a single 8ohm resistor which limits both mid & upper (which are of the same sensitivity). Cut it and job done. I'd already swapped the capacitors for the mid and treble (a must do!) so the sound from them is perfect, literally perfect - what amazing drivers Celestion used to make.The Celestion BL10-100X has an equal frequency range to the philips but has less of a drop at the bottom end which resolves that mellow sound and lack of punch. The largest bass improvement came from removing nearly all of the fluff (which absorbs energy) and porting the ABR enclosure. The swap in driver tops it off.I'm finally happy. I'd pitch these updated 5702's against any speakers at any price up to 100W RMS - they are that good. Cheers, A.
snoopy:The Celestion BL10-100X has an equal frequency range to the philips but has less of a drop at the bottom end which resolves that mellow sound and lack of punch.
... but a half year later in diyaudio service @snoopy wrote:
"They also used an outstanding woofer by Philips. I can't find any details on it but I've tested it against modern Celestion woofers of the same size (10") and the Philips blows them away. It's low-hz extension is superb"
BeO is like a good wine - the older the better...
There's nothing like the original drivers.They were chosen - and often custom produced - for a reason.
I think the same and I want try it:
https://archivedforum2.beoworld.org/forums/t/40446.aspx