yes indeed. I however felt that they're fairly similar and have similar frequency responses so i thought it was reasonable that they could be included in a thread that is primarily about the Beta LTA and perhaps by association use of large wide range drivers. the Fane isn't suited to the enclosure being discussed either. would certainly help anyone searching for the driver to find an alternative etc.
if i'm clogging up the thread with rubbish then please tell me and i'll stop.
any treatments used on either are likely going to be applicable to both however, the foam trick definitely helped once i got it right.
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its actually better in most respects than the standard bullet shape was. i got very little improvement from the conventional bullet shape and i had an hunch that the whizzer was just too big for it to work well. so i've flared it out at the end as i've seen in a few other classics of the full range world and the difference was very impressive.
i've played around with the height of the phase plug and it seems that there's a very large difference in the height that i position the plug, which i will need to further investigate for optimal positioning. i may also use the ductseal/plumbers mait trick that Dave has described in other threads to adjust the base of the plug as well as the frame, as i think there may be a resonance thing occurring there as the there's a pronounced lip between the whizzer cone and structure that attaches it to the voice coil and some peaks that don't appear to change upon EQ manipulation of the single.
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Killing the peaks will make it seem like efficiency has decreased, even thou the median efficiency is still much the same.
dave
would you recommend applying another coat? the EnABL process seems to want a couple of them. i've applied it front and back so far with a single coat about 2 parts modpodge 1 part water, so it was quite thick.
2-1 should endupbeing real runny, i'd guess when i wally thing it out it is 5-7 to 1. Be careful doing both sides -- i usually reserve that for woofers. If you do both you run the risk of producing a stiff sandwich which will increase HF peakiness.
Without the driver in hand, it is hard forme to make any specific suggestions.
After i apply 1 coat on the front of the LTA, i'll decide whether to do another.
dave
is that the waterfall(?) diagram that i see posted?
if it is, could you provide a 'how to' link and i'll give it a go. i've not got the best measuring equipment in the world, so i can only really compare the modifications to the stock driver, or whatever i did previously.
edit: Cumulative Spectral Decay?
this is an interesting idea. i obviously don't want to blow the £40-£50 on the fostex tweeter just for me to destroy. i would however like to play with the idea.
http://www.visaton.com/en/car_hifi/ht_kalotten/cp13_4.html
i could get that in the end of the phase plug, or mounted inside the pole piece. its an order of 10db/watt less efficient than the main cone but would the whizzer help to offset this as it would be almost horn mounted? £25 for a pair of them so their financial impact once ruined is less morally objectionable.
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I have not seen any measurement yet by anyone that shows this information.
A CSD shows you other stuff and is more useful than a FR, but most are fatally flawed using time and not periods as a 3rd axis (and one needs to be able to rotate them, and be able to manipulate the formatting). They also usuelly do not have sufficient resolution ... most seem to stop at about 25 dB ... a really useful one would need to done in an anechoic chamber.
dave
A CSD shows you other stuff and is more useful than a FR, but most are fatally flawed using time and not periods as a 3rd axis (and one needs to be able to rotate them, and be able to manipulate the formatting). They also usuelly do not have sufficient resolution ... most seem to stop at about 25 dB ... a really useful one would need to done in an anechoic chamber.
dave
okey dokey.
i'll give it a bodge anyway, i'm fairly sure there will be some obvious differences as these drivers aren't pretty.
I agree that a lot of CSD's are not done properly - I've seen a lot (posted on this forum and elsewhere) which don't even window out room reflections from the measurement, making the results meaningless, and then use a poor choice of scale for amplitude and/or time. (For example 10-20ms!)
However I don't think I would agree that an amplitude scale down to 40 dB is particularly beneficial or revealing in a CSD, and can in fact be the opposite particularly in a noisy measuring environment where you're just seeing ambient noise without realising it rather than driver decay...
I think theres some reason to believe that the adjacent frequency masking characteristics of the ear put a lower useful limit at about 30dB - once a resonance has decayed 30dB down its effectively gone when surrounded by other nearby content.
Not by accident 30dB is also about the figure that lossy codecs use when calculating masking effects of nearby frequencies, so for any lossy encoded material there is at most about 30dB SNR allocated within any given 1/n octave bucket. (Any signals lower than 30dB below adjacent frequencies are masked by our hearing system and we don't notice if they are missing...)
I've done quite a bit of experimenting with full range driver damping tweaks looking at both frequency response and CSD together with listening tests and for me the result is unanimous - rapid early decay of resonances is far more important than the time it takes for them to decay to very low levels.
In other words minimising the time in ms that it takes for the first 20-30dB of decay is more important than how long it takes to decay to 40dB, and you can't necessarily optimise both at once, especially if you introduce some active EQ in the equation which tends to improve the early decay rate but introduce increased residue and a slower decay at much lower levels.
For this reason I do all my CSD's with a vertical scale of either 25 or 30dB, and then optimise the damping so that any particular resonances decay below this threshold as quickly as possible. This seems to give the best correlation with what sounds the best.
Nearly always this also results in the flattest frequency response, however its not universally the case especially if the damping is helping to remove a notch rather than a peak.
As for the time axis, I generally use either 2 or 4ms. 4ms is needed to show the full decay of a driver with particularly bad resonances (FE207E *cough* *cough*) while a good driver has usually decayed below 30dB well before 2ms, in which case I'll use a 2ms scale for best resolution.
Burst decays with a time axis scaled by cycles instead of ms have their place, particularly for frequencies below about 2Khz, but for frequencies above 2Khz which is where we're usually trying to damp cone breakup I find a time axis scale works better.
I do agree that it would be nice to rotate a CSD in 3D space to get a better view of it, I'd love ARTA to add such a feature
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the waterfall plot thing was indeed useless. the program i was using used sweeps which i've discovered are also utterly useless as i can't eliminate the room resonances etc interfering with the plots. i can isolate as best i can pink noise but the drivers are just so loud and big they still best my efforts. pink noise however doesn't express room resonances as badly.
i took some on and off axis measurements for the stock and modded Fane. the modified driver has a 2nd coat of mod podge applied to the front surface of the whizzer, and around the outer perimeter of the cone including the suspension.
the phase plug seems to be the culprit for the drop in SPL at the 6000hz mark, i shall have to play with things to see if i can't level that out.
i took some on and off axis measurements for the stock and modded Fane. the modified driver has a 2nd coat of mod podge applied to the front surface of the whizzer, and around the outer perimeter of the cone including the suspension.
the phase plug seems to be the culprit for the drop in SPL at the 6000hz mark, i shall have to play with things to see if i can't level that out.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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forgot the FR showing differences between mod podges. worth hitting it with another coat?
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fane sings eva.mpeg - YouTube
made a recording of the thing playing. from that recording, is the massive frequency dive in the 1000-1500hz range audible? i was looking at some other threads and the beta12lta doesn't have anything like that and it is not even partially represented in the official Fane docs.
is this just poor design and a large frequency hole at the crossover between the woofer and the whizzer? or is this some kind of resonance? can it be filtered out somehow?
made a recording of the thing playing. from that recording, is the massive frequency dive in the 1000-1500hz range audible? i was looking at some other threads and the beta12lta doesn't have anything like that and it is not even partially represented in the official Fane docs.
is this just poor design and a large frequency hole at the crossover between the woofer and the whizzer? or is this some kind of resonance? can it be filtered out somehow?
added 3rd coating of mod podge, more to back of whizzer and i deliberately let it gather in the very base of the interface between the main cone and the whizzer.
initially i thought 'oh crêpe! i've ruined it', however after stuffing the foam behind the whizzer again the dive at 6k has lessened however i've incresed the peak at 1500hz
lost some brightness to the driver but its a tad easier to listen to.
initially i thought 'oh crêpe! i've ruined it', however after stuffing the foam behind the whizzer again the dive at 6k has lessened however i've incresed the peak at 1500hz
lost some brightness to the driver but its a tad easier to listen to.
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i dampened the basket with some plumbers-mait/duct seal/horrible sticky crap that gets everywhere.
i think it sounds better but the graphs don't really show what i think is a beneficial change? those graphs are aligned to zero, so it shows the SPL is lowered, which could mean there's not as much reflecting back through the cone? so if that was true then it would explain why i think it sounds better?
i'm thinking the 3rd coat of mod podge was maybe too much. EnABL up next and then Ebay with them as i can't really see them growing on me, even with a tweeter helping them.
i think it sounds better but the graphs don't really show what i think is a beneficial change? those graphs are aligned to zero, so it shows the SPL is lowered, which could mean there's not as much reflecting back through the cone? so if that was true then it would explain why i think it sounds better?
i'm thinking the 3rd coat of mod podge was maybe too much. EnABL up next and then Ebay with them as i can't really see them growing on me, even with a tweeter helping them.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
driver is now EnABL'd, it nearly smoothed out the problem at 5-6khz i've been having, just narrowly missed with my tap test i think?
will try and fix it by changing the foam around the driver and improve the phase plug shape.
listening wise, the EnABL after 3 coats has completely transformed the driver. it used to be a bit lifeless but once the peak centred around 1600hz is taken down with a little EQ they become really quite fun to listen to. its not perfect by any means but the feeling of realism and depth a driver of this size gives is impressive.
will try and fix it by changing the foam around the driver and improve the phase plug shape.
listening wise, the EnABL after 3 coats has completely transformed the driver. it used to be a bit lifeless but once the peak centred around 1600hz is taken down with a little EQ they become really quite fun to listen to. its not perfect by any means but the feeling of realism and depth a driver of this size gives is impressive.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
certainly.
its looks almost as bad as my choice of EnABL colours. the peak at 1500hz is really annoying and is what makes this impossible for me to ever use for listening to music. might be ok for the tv/cinema set up.
the driver Fs hasn't changed at all despite all the bodging i've done.
An externally hosted image should be here but it was not working when we last tested it.
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'corrected' my little EnABL mishap by completing the single track rings. i need to now get CSD tests to work in order to see if these changes are beneficial or just a load of distortion building up the responses.
An externally hosted image should be here but it was not working when we last tested it.
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got that CSD stuff to work. seems like i've improved the top end but the bottom end probably got worse?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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