I have a pair of QLN Splitfield Signature speakers and I absolutely love them, unfortunately one of the tweeters died the other day and needs to be replaced.
The tweeter that is in them is the Scanspeak D2905/9000 which isn't made any more, it has an impedance of 4 ohms and a sensitivity of 90dB. I guess the obvious thing to do would be to replace the tweeters with the Scanspeak D2905/9500 tweeters (6 ohm, 90dB), but I'm wondering if I can do better and if so whether the advantage over the D2905/9500 would be really noticable. I'm limited to an overall diameter of 104mm. I'm tempted by the look of the response on the Scanspeak 2904/730001's, but guess I'd need to attenuate them a little using an L-Pad since the sensitivity is up at 94dB. So I'm kind of thinking using a resistance of 6.84 ohms for the series resistor and 1.476 for the parallel resistor (or as close as I can get to those values).
Anyway, I guess my question is, do you think the 2904/730001 with an L-Pad would greatly out perform the D2905/9500? Are there any other tweeters that I should consider?
Any help would be much appreciated.
Kind regards,
Andrew
The tweeter that is in them is the Scanspeak D2905/9000 which isn't made any more, it has an impedance of 4 ohms and a sensitivity of 90dB. I guess the obvious thing to do would be to replace the tweeters with the Scanspeak D2905/9500 tweeters (6 ohm, 90dB), but I'm wondering if I can do better and if so whether the advantage over the D2905/9500 would be really noticable. I'm limited to an overall diameter of 104mm. I'm tempted by the look of the response on the Scanspeak 2904/730001's, but guess I'd need to attenuate them a little using an L-Pad since the sensitivity is up at 94dB. So I'm kind of thinking using a resistance of 6.84 ohms for the series resistor and 1.476 for the parallel resistor (or as close as I can get to those values).
Anyway, I guess my question is, do you think the 2904/730001 with an L-Pad would greatly out perform the D2905/9500? Are there any other tweeters that I should consider?
Any help would be much appreciated.
Kind regards,
Andrew
Hi,
Fried voicecoils are pretty terminal but often broken
tweeter connections can be fixed, find the fault.
rgds, sreten.
Fried voicecoils are pretty terminal but often broken
tweeter connections can be fixed, find the fault.
rgds, sreten.
Proper design is much more important than just using better tweeter. With the Revelator, you need to redesign everything, which you wont. So the D2905/9500 seems to be a better option and you may use an L-Pad of 0.22R|10R if no L-pad was used before.
First find the fault. If the tweeter is not fixable then:
1) contact Scan-Speak and ask for a quotation
2) try to find a used D2905/9000
3) as a last resort try finding a suitable replacement unit - looking at FR and impedance profile a D2905/9300 is better than the 9500
Ralf
The D2905/9000 is really a 6 Ohm driver and not 4
1) contact Scan-Speak and ask for a quotation
2) try to find a used D2905/9000
3) as a last resort try finding a suitable replacement unit - looking at FR and impedance profile a D2905/9300 is better than the 9500
Ralf
The D2905/9000 is really a 6 Ohm driver and not 4
Thanks for all your responses I really appreciate your input. 🙂 I'm going to go away and consider everything that each of you have written. As a little more information though...
I was going to check for the fault last night, but I couldn't find my multi-meter... it wasn't where I usually keep it. I thought about it this morning on the way to work though and I think I know where I put it.
Anyway, assuming that the coil has gone (though I have my doubts since I've not played it at even a moderately high volume for a while), then I guess I'd like to upgrade the tweeters rather than finding a replacement 2905/9000. My reason is that although I love the sound that the QLN's produce, there is a slightly laid back aspect that I'd like to remove without adding any fatigue or harshness - perhaps the slightly laid back sound is partly a timing issue, but the 9000 does roll off a little early, so I'm hoping it's just the latter.
I'm certainly not afraid to redesign the cross-over (with help from people on this forum). Although I don't have any experience with audio cross-overs I have a background in designing, building and testing electronic instruments and on many occasions have made use high pass filters, low pass filters and band pass filters all of various orders in my designs depending on requirements, and I understand notch filters. So in some ways, I find the thought of redesigning a cross-over an exciting prospect and I'd definitely appreciate any help and advice that any of you are willing to offer. I should probably mention, that I have always liked the idea of designing and building my own speakers, but have never done it.
Anyway, if the tweeter has gone, then I'd rather make a proper upgrade, so I don't especially feel limited to getting tweeters where I don't need to modify the cross-over much - I just want even better sound, even if a little saving up is required 🙂
In the mean-time, I'll get my meter out and find the fault and also find out the model of the mid/bass unit. I might even open up the existing cross-over and map out the existing design.
Finally, if it turns out to be a break or bad connection, then after repairing the QLN's, I'd like to have a go at either upgrading them anyway, or designing my own speakers - though the latter might be a longer term project.
Thanks once again to all of you. As soon as I've found or confirmed the fault I'll let you know - it might be a few days from now though unless I get an unexpectedly clear evening.
I was going to check for the fault last night, but I couldn't find my multi-meter... it wasn't where I usually keep it. I thought about it this morning on the way to work though and I think I know where I put it.
Anyway, assuming that the coil has gone (though I have my doubts since I've not played it at even a moderately high volume for a while), then I guess I'd like to upgrade the tweeters rather than finding a replacement 2905/9000. My reason is that although I love the sound that the QLN's produce, there is a slightly laid back aspect that I'd like to remove without adding any fatigue or harshness - perhaps the slightly laid back sound is partly a timing issue, but the 9000 does roll off a little early, so I'm hoping it's just the latter.
I'm certainly not afraid to redesign the cross-over (with help from people on this forum). Although I don't have any experience with audio cross-overs I have a background in designing, building and testing electronic instruments and on many occasions have made use high pass filters, low pass filters and band pass filters all of various orders in my designs depending on requirements, and I understand notch filters. So in some ways, I find the thought of redesigning a cross-over an exciting prospect and I'd definitely appreciate any help and advice that any of you are willing to offer. I should probably mention, that I have always liked the idea of designing and building my own speakers, but have never done it.
Anyway, if the tweeter has gone, then I'd rather make a proper upgrade, so I don't especially feel limited to getting tweeters where I don't need to modify the cross-over much - I just want even better sound, even if a little saving up is required 🙂
In the mean-time, I'll get my meter out and find the fault and also find out the model of the mid/bass unit. I might even open up the existing cross-over and map out the existing design.
Finally, if it turns out to be a break or bad connection, then after repairing the QLN's, I'd like to have a go at either upgrading them anyway, or designing my own speakers - though the latter might be a longer term project.
Thanks once again to all of you. As soon as I've found or confirmed the fault I'll let you know - it might be a few days from now though unless I get an unexpectedly clear evening.
"Upgrading" a speaker is not much easier than designing one from scratch, the method and tools needed are exactly the same. As Jay said, proper design is much more important than just using a better driver. The chance that your first upgrade/design ends up better than the speaker you love is roughly zero.
Ralf
If you want to use the D2904/710003, you also need to do some woodworking as the flange is much thicker than the D2905/9000 one
Ralf
If you want to use the D2904/710003, you also need to do some woodworking as the flange is much thicker than the D2905/9000 one
If you're an experienced filter designer, all you need really is some measuring equipment to do FR and impedance plots. Such stuff is cheap these days (one Revelator tweeter will likely set you back more) but pretty reliable.
That will bring the fun into your challenge and also bring you more knowledge on speaker design.
That will bring the fun into your challenge and also bring you more knowledge on speaker design.
Thanks Ralf,
Based on what you've said, I think if the coil has gone, I'll replace both tweeters with either the 9300 or the 9500.
In your previous post with respect to a better match to the 9000, you mentioned that "looking at FR and impedance profile a D2905/9300 is better than the 9500". I've taken a look and I agree that both curves seem to be a better match. However, it was my understanding that the impedance profile only really affects load on the amplifier, am I correct, or is there more to it than that? The reason why I ask is that I was hoping to get rid of the early treble roll-off that I currently have with the 9000 and it looks like the 9500 might be better on that front, even though it doesn't look quite so like the 9000 in FR profile.
My concern with the 9500 is the shape of the FR in the crossover frequency region (there is a slight, but wide hump that is not there on the 9000 or 9300). Once I've analysed the crossover and figured out the actual crossover frequency and the order of the filters I guess I'll have a better idea of whether or not the hump/shape the FR near the crossover frequency is really a problem - if it is I guess I could always apply a mild notch filter if it is a problem... or as you suggest I could just make life simpler and get the 9300 instead.
Based on what you've said, I think if the coil has gone, I'll replace both tweeters with either the 9300 or the 9500.
In your previous post with respect to a better match to the 9000, you mentioned that "looking at FR and impedance profile a D2905/9300 is better than the 9500". I've taken a look and I agree that both curves seem to be a better match. However, it was my understanding that the impedance profile only really affects load on the amplifier, am I correct, or is there more to it than that? The reason why I ask is that I was hoping to get rid of the early treble roll-off that I currently have with the 9000 and it looks like the 9500 might be better on that front, even though it doesn't look quite so like the 9000 in FR profile.
My concern with the 9500 is the shape of the FR in the crossover frequency region (there is a slight, but wide hump that is not there on the 9000 or 9300). Once I've analysed the crossover and figured out the actual crossover frequency and the order of the filters I guess I'll have a better idea of whether or not the hump/shape the FR near the crossover frequency is really a problem - if it is I guess I could always apply a mild notch filter if it is a problem... or as you suggest I could just make life simpler and get the 9300 instead.
Yeah I should really look into that. The problem that I have is that I don't have any experience designing audio cross-overs and the experience that I referred to in my previous post was actually mainly academic learning and some research about 15 years ago - I was on a very hands on BSc Honours degree course called "Instrumentation with Applied Physics" and really enjoyed the electronics design aspect. That was before I did my Physics PhD and then oddly took a very different road into Software Engineering.Anyway, although I would say I have experience, I wouldn't exactly call myself an experienced filter designer, more someone who understands them after having to study many aspects of them and has designed and tested a bunch of instruments that worked as expected that utilised filters of varying type and order. The thing is, the things I did back then tended to be higher impedance, low current designs - I'm not use to having to worry about impedance curves (although I'm still not sure what role they play in crossover design aside from load issues/calculations for the amplification).
In short, I'm fully aware that I can learn an awful lot from people on this forum.🙂 At the same time, I enjoy electronics (even though I don't get the opportunity to play much which such things these days) and look forward to the idea of designing my own speakers one day. 🙂 I guess if I can pick up a signal generator, a good microphone and an oscilloscope off ebay I could probably measure a fair amount. 🙂
Anyway, at the moment, the optimistic part of me says "go wild" whereas the more sensible part of me says that I should walk before I can run. I think I should repair the QLN's with as least modification as necessary. I guess that means either following Ralf's suggestion of the 9300, or Jay's suggestion of the 9500 with an L-Pad... if the crossover has an L-Pad already, then I'll recalculate the L-Pad. Once I've done that, then I think I'll look in to designing my own speakers. 🙂
It dictates how the crossover works.
The FR of a driver in a cab is a combination of the natural FR of that driver, and the diffraction + baffle step effects. Both diffraction and baffle step depend on the baffle dimensions and on the placement of the driver on the baffle. This "modified" FR will then be worked by the crossover, but changing impedance will also change the way the crossover works. So for a tweeter a replacement driver should have very similar FR and impedance function - for a woofer it is worse as it should also have similar Fs, Vas and Qts.
Once you trace the crossover, it should be relatively easy to simulate the effect on a 9300 and 9500.
Ralf
Thanks again Ralf. It looks like I have a lot to learn.
On another note, I've failed to find my multi-meter so I can't check for continuity in the cables or resistance over the driver - I have a feeling I leant it to someone. I guess I'll need to get a new multi-meter.
Anyway when I get the opportunity I'll map out the cross-over and also find out the mid-bass unit model number and will report back.
Thanks once again,
Andrew
On another note, I've failed to find my multi-meter so I can't check for continuity in the cables or resistance over the driver - I have a feeling I leant it to someone. I guess I'll need to get a new multi-meter.
Anyway when I get the opportunity I'll map out the cross-over and also find out the mid-bass unit model number and will report back.
Thanks once again,
Andrew
So, I've ordered a new multimeter and while I'm waiting for it to arrive, I thought I'd install SweepGen and see if I could figure out a rough crossover frequency by ear... I knew it was going to be highly inaccurate, but my theory was that because I have an external crossover I can easily disconnect the mid/bass driver from the speaker where the tweeter works and that would mean that I would have one speaker where just a tweeter was working and one speaker where just the mid/bass was working.
My theory was that assuming both the high-pass and low-pass filters are of the same order then the crossover frequency would be roughly mid-way between the vanishing point on the upper bound of the mid/bass unit and the vanishing point on the lower bound on the tweeter - I know this isn't entirely accurate since the real slopes are a combination of the filter and FR of the driver, but I was only going for an approximation.
So, the left speaker is the one with just the mid/bass and the right tweeter is the speaker with just the tweeter connected. I set the volume to a lowish level.
I then ran SweepGen on just the left speaker the tone disappeared when it reached about 8.5KHz. At the same volume, the vanishing point on the tweeter was far lower than I thought it would be - 700Hz. That means that the crossover might be around 4600Hz. it seems to me as if the crossover is using first order filters because the drop off seems really slow (the mid starts to drop off at about 3kHz). Of course, this is a pointless post since I really need to take the crossover apart to figure out the real crossover frequency.
I guess the thing is though, the test was at a low volume which means the tweeter vanishing point is really probably a bit lower than 700Hz and this concerns me. Isn't 700Hz a little low for a tweeter?
My theory was that assuming both the high-pass and low-pass filters are of the same order then the crossover frequency would be roughly mid-way between the vanishing point on the upper bound of the mid/bass unit and the vanishing point on the lower bound on the tweeter - I know this isn't entirely accurate since the real slopes are a combination of the filter and FR of the driver, but I was only going for an approximation.
So, the left speaker is the one with just the mid/bass and the right tweeter is the speaker with just the tweeter connected. I set the volume to a lowish level.
I then ran SweepGen on just the left speaker the tone disappeared when it reached about 8.5KHz. At the same volume, the vanishing point on the tweeter was far lower than I thought it would be - 700Hz. That means that the crossover might be around 4600Hz. it seems to me as if the crossover is using first order filters because the drop off seems really slow (the mid starts to drop off at about 3kHz). Of course, this is a pointless post since I really need to take the crossover apart to figure out the real crossover frequency.
I guess the thing is though, the test was at a low volume which means the tweeter vanishing point is really probably a bit lower than 700Hz and this concerns me. Isn't 700Hz a little low for a tweeter?
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You could try this business for a replacement kit for your D2905-9000 tweeter Replacement kit D2905-9000 3950 7390105 Replacement kit D2905-9000 Replacement dome with voicecoil kit for the Scan-Speak D2
Arthur.
Arthur.
Ok, so my multimeter arrived I did some fault finding, and there is an infinite resistance over the terminals on the tweeter, so I guess the voice coil has gone. I have mapped out the crossover as far as I can (I don't have the right equipment to find out the inductor values).
So, the drivers are as follows:
tweeter: Scanspeak D2905/9000
mid/bass: Scanspeak 18W/8545K
Here is a diagram of the crossover
and a picture
I know I could go for a replacement voice coil as linked by Arthur, but I would like to get an upgrade if possible. Anyway, based on the above diagram, am I still best going for the replacement coil for the D2905/9000, the D2905/9300 or will the D2905/9500 be potentially better with a little tweaking to the crossover? As I say, I'd like to get rid of the laid back part of the sound, which I believe is due to the early roll-off of the D2905/9000, but I'm new to this, so you'll know far better than I do.
Kind regards,
Andrew
So, the drivers are as follows:
tweeter: Scanspeak D2905/9000
mid/bass: Scanspeak 18W/8545K
Here is a diagram of the crossover
and a picture
I know I could go for a replacement voice coil as linked by Arthur, but I would like to get an upgrade if possible. Anyway, based on the above diagram, am I still best going for the replacement coil for the D2905/9000, the D2905/9300 or will the D2905/9500 be potentially better with a little tweaking to the crossover? As I say, I'd like to get rid of the laid back part of the sound, which I believe is due to the early roll-off of the D2905/9000, but I'm new to this, so you'll know far better than I do.
Kind regards,
Andrew
Hi,
Check the open tweeter for a broken lead.
The x/o as drawn must be wrong, 0.2R short in the treble.
rgds, sreten.
Check the open tweeter for a broken lead.
The x/o as drawn must be wrong, 0.2R short in the treble.
rgds, sreten.
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You are right, my apologies, my new multimeter was messing around a bit when I was trying to measure that resistor (it was fine for all the other components), as it turns out that 0.2 ohm resistor is actually 15 ohms.
I wasn't sure how to get the tweeter open, it didn't seem obvious to me, but I expect there are youtube vid's online that I can check. 🙂 Anyway, if I get it apart and the coil is at fault, what do you think about my options?
Hi,
Treble can be tweaked with R and C across the
2.2R. Your best bet is the original drivers IMO.
rgds, sreten.
Treble can be tweaked with R and C across the
2.2R. Your best bet is the original drivers IMO.
rgds, sreten.
Andrew, I concur that a new voicecoil is best here. 36 Euros is hardly a steep price.
I'll tell you that your crossover looks like a LR2 negative polarity time aligned 12dB/octave design with Fs 800Hz LCR correction on the tweeter. I show what I would expect below. The electrical response should give you a clue to what the crossover does to the tweeter response.
Very hard to adapt that to a new tweeter unless you really know what you are doing. A little tonal adjustment might be easy enough, but really D2905 is D2905 IMO. Yours seems to be non-ferrofluid, so no great issues in repair.
As ever, the answer lies in stating the problem clearly. 🙂
I'll tell you that your crossover looks like a LR2 negative polarity time aligned 12dB/octave design with Fs 800Hz LCR correction on the tweeter. I show what I would expect below. The electrical response should give you a clue to what the crossover does to the tweeter response.
Very hard to adapt that to a new tweeter unless you really know what you are doing. A little tonal adjustment might be easy enough, but really D2905 is D2905 IMO. Yours seems to be non-ferrofluid, so no great issues in repair.
As ever, the answer lies in stating the problem clearly. 🙂
