I am trying to repair a set of broken floor standing speakers for someone on a very limited budget. The amp is 35 watts per channel with 8 ohm output impedance. i am lookng for suitable crossovers ( for cheap) Most of the cheap crossovers on Amazon insted of specifying an exact impedance give numbers like 4-8 ohms or 4- 10 ohms. I have seen crosssovers with jumper leads for selecting 4 or 8 ohms but these particular crossovers do not have jumpers.
What does a specification saying 4-8 0hm impedance mean in practice?
What does a specification saying 4-8 0hm impedance mean in practice?
Hmmm...broken in what sense? Are you sure drivers are still ok? When you overload speakers with power, you can burn tweeters. If your amp presents dc, it can kill the woofer.
Its hard to kill mp cap in the crossover, its typically specified for hundreds of volts.
Unless you find out exactly what is broken, buying generic crossover makes no sense. Well, it does not make sense at all to put generic crossover to unknow floorstanding speaker.
Its hard to kill mp cap in the crossover, its typically specified for hundreds of volts.
Unless you find out exactly what is broken, buying generic crossover makes no sense. Well, it does not make sense at all to put generic crossover to unknow floorstanding speaker.
These are 30 year old Purdey( 75 X 15 X 22cm) floor standing two way speakers. I have no way of testing anything other than a multimeter. They are so old I plan on replacing the tweeters, woofers and crossovers. The current woofers are 5" 40 watts. They are blown. The owner does not want to throw out the enclosures and simply buy new speakers which is what I, and many others, have advised.
So two new woofers, two tweeters and two crossovers needed. I have selected cheap reasonable looking 8 ohm woofers and tweeters that can handle the 35 watts from the amp. I need crossovers around the 3khz range.
Reasonable stereo sound is the aim here. It's clear i think that audiophile satisfaction is not the goal.
So two new woofers, two tweeters and two crossovers needed. I have selected cheap reasonable looking 8 ohm woofers and tweeters that can handle the 35 watts from the amp. I need crossovers around the 3khz range.
Reasonable stereo sound is the aim here. It's clear i think that audiophile satisfaction is not the goal.
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If these are the speakers to which you refer, they're 'Revolver Purdey" with an unspecified 5.5" mid and a 3/4" Vifa tweeter.
If you haven't already bought the drivers, although it looks like you have, I'd go for something like the Peerless 830656 which can be surface mounted and a newer Vifa BC25TG, DX20, BC25SC55 or similar tweeter. There are at least two projects for the Peerless which use a similar sized cabinet to the Purdeys.
There are several well documented and freely available DIY designs for a Peerless/Vifa or a similar configuration which will work heaps better than anything pre-made and be cheaper, too. For example, one design for the BC25SC55 only uses four parts. I can provide links if you're interested.
Depending where you live, Dayton drivers might be available and many of those, such as the DC130A, DS135 and DSA135 can be surface mounted. Several documented projects use those, too.
I'm suggesting surface mount as it will mean less mucking about with the cabinet.
Honestly, anything pre-made just won't work properly, let alone provide 'reasonable sound'. It will make noise but that's about it. Additionally, most tweeters are 4 or 6 ohms, 8 ohm tweeters are fairly rare as far as I can make out; so that's another reason a pre-made XO won't work.
If you have purchased the drivers, what have you got, please?
Geoff
If you haven't already bought the drivers, although it looks like you have, I'd go for something like the Peerless 830656 which can be surface mounted and a newer Vifa BC25TG, DX20, BC25SC55 or similar tweeter. There are at least two projects for the Peerless which use a similar sized cabinet to the Purdeys.
There are several well documented and freely available DIY designs for a Peerless/Vifa or a similar configuration which will work heaps better than anything pre-made and be cheaper, too. For example, one design for the BC25SC55 only uses four parts. I can provide links if you're interested.
Depending where you live, Dayton drivers might be available and many of those, such as the DC130A, DS135 and DSA135 can be surface mounted. Several documented projects use those, too.
I'm suggesting surface mount as it will mean less mucking about with the cabinet.
Honestly, anything pre-made just won't work properly, let alone provide 'reasonable sound'. It will make noise but that's about it. Additionally, most tweeters are 4 or 6 ohms, 8 ohm tweeters are fairly rare as far as I can make out; so that's another reason a pre-made XO won't work.
If you have purchased the drivers, what have you got, please?
Geoff
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As usual pictures of the speakers in question as well as pix of the drivers/tweeters and the existing crossover will help.
I'm pretty sure that the woofer and tweeter are both Vifa; the C13MG and the D-19.Spec's available at nedlabs
I'm pretty sure that the woofer and tweeter are both Vifa; the C13MG and the D-19.Spec's available at nedlabs
Well spotted, I think you're right. Neither of those drivers are cheap, unfortunately; a UK firm has the tweeters for 26 pounds; a well known mail order site, for A$70 each. Ouch. The D19s are specified as 8 ohms.
However, Digikey has one which looks almost the same for A$29:
https://www.digikey.com.au/en/products/detail/peerless-by-tymphany/D19TD05-08/6557405
I couldn't find the exact C13s but a very similar Vifa C13 was going for US$60 each.
Specs:
Armed with the specs, and assuming the OP hasn't purchased the drivers, people may be able to suggest alternatives.
Geoff
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Geoff, thank you for your detailed reply. The purdeys do look like that. I have not purchased anything yet. I shall try to source the drivers you recommend. I would be very grateful if you would post details for making my own crossovers. I have a technical background and can manage circuit building quite well. My greatest difficulty is sourcing components here in Ireland.
Once again thankk you for taking the time and effort to answer. The person involved is diabled, legally blind, so the sound system is important.
Best Regards.
Geoff,
I followed the link and tried to order the tympany D19's (to ascerain the shipping cost) but the site only seems to allow ordering within Australia. I will email them.
Regards
Sorry for the fragmented responses. I have sourced the Peerless 830656 drivers and the BC25TG15-04's (soundimports) and the budget will stretch to these, particularly as I will now (apparently) be building the crossovers (1khz?) myself. Thank you so much for that.
I have a question about the tweeters. They are only 4 ohm impedance, is this a problem given that the amp (NAD 304) has 8 ohm output impedance?
If you could post a recommended crossover diagram (and possible components supplier ) I should be able to proceed.
This has been so helpful. I spent a few days floundering looking at various drivers, really unsure about what would work. Being able to get almost identical replacements is so much more reassuring.
Best Regards
The 4 ohm tweeters should not be an issue; any modern amp will be fine; I don't know the NAD by they make good stuff. My 25 year old Yamaha '8 ohm' receiver drives our MTMs, no problem in five years. Impedance is nominal in any case and varies with frequency.
Firstly, it's worth stressing that your project will necessarily not sound the same as the original speakers, which were designed around those drivers and their crossover. However, given that the original drivers are now either not available or above your budget, we want to try and help you as much as possible.
The cut outs in your friend's speakers are different sizes to what's in the speakers now: you'll need to slightly enlarge the woofer hole (diameter is 117mm v 109 for your woofer). The D19 tweeter has a larger hole than the BC25 so you'll need to do something about that, but no big deal. Just make sure you can flush mount them.
Cabinet volume should be OK; the 830656 has be used in bookshelf and tower designs. According to Win ISD software, the tower should give a bit lower bass extension but not play as loud as a bookshelf.
The Purdeys (the designer must have owned a shotgun?) were of course designed for the C13 woofer, so anything else in that volume will be a compromise of course. Cabinet width should be OK.
How are you going to mount the crossovers? If you can't remove any panels from the speakers, you can mount them on the back of the cabinet.
As for the crossover, Ralf Giralfino of this Forum kindly posted his design for a bookshelf design using those drivers; I've made them and they sound very good. The crossover point is about 2600 Hz.
However, and importantly, the Purdeys are small towers and not bookshelves, and have a different driver layout on the baffle, e.g the tweeter is on the bottom.
It would be polite to send Ralf a PM (use the email link at the top of this page) to see if he has any comments. His crossover is designed for a bookshelf, smaller volume than your boxes, and with the tweeter on top.
Alternatively, I've attached a crossover for the same drivers which I based on a German DIY tower design, but tweaked to allow for the BC25TG tweeter. However, it was only simmed as I don't have measuring equipment. The tweeter is connected with reverse polarity.
Hopefully, another Forum member with much more expertise than I will have some ideas on your project too.
Geoff
Firstly, it's worth stressing that your project will necessarily not sound the same as the original speakers, which were designed around those drivers and their crossover. However, given that the original drivers are now either not available or above your budget, we want to try and help you as much as possible.
The cut outs in your friend's speakers are different sizes to what's in the speakers now: you'll need to slightly enlarge the woofer hole (diameter is 117mm v 109 for your woofer). The D19 tweeter has a larger hole than the BC25 so you'll need to do something about that, but no big deal. Just make sure you can flush mount them.
Cabinet volume should be OK; the 830656 has be used in bookshelf and tower designs. According to Win ISD software, the tower should give a bit lower bass extension but not play as loud as a bookshelf.
The Purdeys (the designer must have owned a shotgun?) were of course designed for the C13 woofer, so anything else in that volume will be a compromise of course. Cabinet width should be OK.
How are you going to mount the crossovers? If you can't remove any panels from the speakers, you can mount them on the back of the cabinet.
As for the crossover, Ralf Giralfino of this Forum kindly posted his design for a bookshelf design using those drivers; I've made them and they sound very good. The crossover point is about 2600 Hz.
However, and importantly, the Purdeys are small towers and not bookshelves, and have a different driver layout on the baffle, e.g the tweeter is on the bottom.
It would be polite to send Ralf a PM (use the email link at the top of this page) to see if he has any comments. His crossover is designed for a bookshelf, smaller volume than your boxes, and with the tweeter on top.
Alternatively, I've attached a crossover for the same drivers which I based on a German DIY tower design, but tweaked to allow for the BC25TG tweeter. However, it was only simmed as I don't have measuring equipment. The tweeter is connected with reverse polarity.
Hopefully, another Forum member with much more expertise than I will have some ideas on your project too.
Geoff
Attachments
I'd still like to see pictures of the actual components and the blown drivers, sometimes it isn't a burnt out voice coil but something repairable, like a broken tinsel wire, I've resoldered or patched those a couple of times
Absolutely: many things can be fixed with a simple repair:
a friend was told her car needed a new engine because it was blowing smoke from the block: fixed with a $10 new PCV valve;
our CD player seemed to have croaked, fixed by taking the lid off and squirting some electronics lube spray on the tray;
bung tweeter fixed by re-connecting the negative lead as it had fallen off.
Geoff
Unfortunately, someone else had a go at repairing this before me. They just threw in a random car speaker that they had lying around (and threw away the woofer). The car speaker worked for a short while and then that speaker stopped working altogether. I assume the crossover was blown somehow. This is why I want to replace everything. I also want both speakers to be matched (even if my configuration is sub optimal). I am truly grateful for everyone's help here. Thank you for your concern and input. Any advice is appreciated.
Regards
Once again, thank you for going to the trouble of writing such a detailed response. Woodwork is more my forte these days, ( I would happily build new enclosures for this project if the recipient was't so insistent on keeping the current ones) so I don't expect any great difficulties in that direction.
I think I will go with the diagram you provided ( my computer cannot open the .dxo format of the other). I just have to source the components. I have found a supplier that caters to this market in Ireland. I plan on ordering resistors rated at 5 watts and capacitors rated for 50 volts or more.
I'll let you all know how I get on. Thanks again.
Best Regards