Although... on reflection, perhaps before I settle on a compromise I should look for a way of getting all that i wanted - so that I never look back and regret it later. So I'm going to look more into:
# The SS Discovery 15M - looks like it may have all that I wanted and very reasonably priced, but seems too new to have much feedback on it.
# Using 2x ss10F drivers would seem an ideal and almost certain way of getting everything I wanted, 'except' that I suspect lobing would then introduce its own compromise.
# The Revelator 15M - expensive but i guess if I'm considering 2x10Fs its £comparable. 'If' it also compares audibly with the 10F then not having to double it up would be helpful.
Cheers
Kev
# The SS Discovery 15M - looks like it may have all that I wanted and very reasonably priced, but seems too new to have much feedback on it.
# Using 2x ss10F drivers would seem an ideal and almost certain way of getting everything I wanted, 'except' that I suspect lobing would then introduce its own compromise.
# The Revelator 15M - expensive but i guess if I'm considering 2x10Fs its £comparable. 'If' it also compares audibly with the 10F then not having to double it up would be helpful.
Cheers
Kev
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How does a driver of the same 100mm size and (much) lower xmax produce more SPL? I think you may need to check your sums.
It is likely to be hard to size a midrange without knowing the capabilities of your tweeter. It is not usually wise in a 3 way for the midrange to be hitting the SPL limits first. A midrange is not usually required to move much and will normally have been designed with this in mind.
If dispersion control is important then use a tweeter with a waveguide and crossover closer to 2kHz to a 5" mid. This is what most pro-monitors do that significantly weight smooth dispersion (e.g. see JBL LSR6332 measurements on spec sheet).
with less Xmax and all else being equal you have a more effective driver
besides, a pure midrange doesn't really need much Xmax
but you need to be absolute certain it will be used for midrange only
it will not work if you are tempted to try lower xo point
but you can consider every bit of not used Xmax to be wasted energy
For a given frequency and the same sized speakers SPL is proportional to displacement. The smaller the displacement, the lower the SPL and so the speaker with the much smaller xmax cannot be louder. I don't know what mistake the OP has made but he may be comparing SPL at different frequencies.
yeah, ok, you are right
0.25mm or 0.75mm at 500hz makes substantial difference in SPL
but I guess someone know the accurate numbers
anyway, a more effective driver reaches the SPL target with less power input, and distortion still ought to be less ... theoreticly
ofcourse its more complicated
0.25mm or 0.75mm at 500hz makes substantial difference in SPL
but I guess someone know the accurate numbers
anyway, a more effective driver reaches the SPL target with less power input, and distortion still ought to be less ... theoreticly
ofcourse its more complicated
Possibly I have made a mistake as I am comparing the same frequency range (>300Hz), I'm certainly no expert.. I'd very much appreciate people looking over my logic if you suspect an error:
The 10F has (far) more excursion than some dedicated mids. But as I understand it from the basic simulations in WinISD, achieving all that excursion for the mid-range frequencies in a sealed enclosure of 0.7Qtc would require something like 400W, yet the driver is rated to 15W (30w peak). So I'm concluding that rather than Xmax, I should be looking to electrical/thermal capabilities as the limiting factor in this case, especially since it is rated relatively modestly and its not the most sensitive in the world either.
Importantly, I 'think' that this thermal/electrical cap on the 10F is likely to be somewhat below my chosen max SPL of 105dB@1m (before any sort of clipping, electrical or physical). BUT its very possible that I have not judged the relative power correctly...
Presumably this depends on the crest factor of the music and the driver's short term abilities. My max SPL of 105dB would require short term peaks up to around 55-60w at the 10F's sensitivity, which is 4x it's continuous power rating or 2x what I believe is its long term peak rating (if thats not a contradiction in terms). That latter in particular makes me nervous..
Which could be fine if (a) the windings etc can routinely take all the peak current and force without degradation and (b) the crests are large enough relative to the average music power to make the average heating effect small. My problem is that I'm not certain of these things so it makes me nervous to design with those assumptions; I'd feel safer using a driver with at least a long-term peak rating that was within spec.
Cheers
Kev
Edit: by comparison the audax 'would' hit X-max before its thermal limits, but if what I've said above isn't rubbish, this would be reached at considerably higher SPL than the 10F's thermal limit.
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Are you simulating a midrange in a box in WinISD without a high pass filter? If so, try applying a typical 4th order high pass filter at 300-400Hz to your 2 midranges and having another look (I think WinISD can do this). SPL is proportional to cone velocity. It requires more displacement and more power at lower frequencies than high frequencies for the same SPL.
Yes, I'm already using a high pass filter - 300Hz, 4th order. Without it Xmax most definitely would be a problem for the audax mid range; it has an Fs of around 250Hz so in practice I'd probably cross over higher, but I simulated at 300Hz to compare like-for-like.
Give me a while and I'll post some simulations to explain better what I mean; I seem to have deleted my HM100 driver profile somehow.
Cheers
Kev
Give me a while and I'll post some simulations to explain better what I mean; I seem to have deleted my HM100 driver profile somehow.
Cheers
Kev
Okay here they are:
First the SPL chart - both the same, 105dB@1m
Second the Excursion - The Audax HM100 is about half its X-max but still plenty in hand, the F10 is of course only about 1/7th of its Xmax - so very easily okay. Both with 300Hz 4th order high pass.
Third the power; the sensitive Audax is using 15watts out of a nominal 40w it can handle, so not at all troubled, but the F10 is using about 55W whilst it can nominally handle 15W, so a number of times beyond its rating, or nearly twice over even its peak rating.
Finally the Max SPL. Note the Audax is reaching 109dB, whilst the F10 is reaching only around 99dB or so - the former is hitting its X-max, but the latter is hitting its max power far sooner (and in fact below my 105dB aspirations).
Okay so I could push the F10 beyond its power rating for transients, whereas I can't for the audax without exceeding linear travel. But the F10 would need an equivalent of 10 times its nominal power rating just to reach the same SPL as the Audax can reach fully within spec. Which is why I'm thinking that in practice the audax can reach higher SPLs even with a smaller Xmax.
Cheers
Kev
First the SPL chart - both the same, 105dB@1m
Second the Excursion - The Audax HM100 is about half its X-max but still plenty in hand, the F10 is of course only about 1/7th of its Xmax - so very easily okay. Both with 300Hz 4th order high pass.
Third the power; the sensitive Audax is using 15watts out of a nominal 40w it can handle, so not at all troubled, but the F10 is using about 55W whilst it can nominally handle 15W, so a number of times beyond its rating, or nearly twice over even its peak rating.
Finally the Max SPL. Note the Audax is reaching 109dB, whilst the F10 is reaching only around 99dB or so - the former is hitting its X-max, but the latter is hitting its max power far sooner (and in fact below my 105dB aspirations).
Okay so I could push the F10 beyond its power rating for transients, whereas I can't for the audax without exceeding linear travel. But the F10 would need an equivalent of 10 times its nominal power rating just to reach the same SPL as the Audax can reach fully within spec. Which is why I'm thinking that in practice the audax can reach higher SPLs even with a smaller Xmax.
Cheers
Kev
Attachments
I have put the two Scan-Speak drivers into WinISD and things look fairly sensible. One 5.5" driver is equivalent to two 4" drivers. Crossed at 300Hz both give an output over your target of 105dB with 0.5mm excursion at the rated power. 300 Hz is lower than typical for a 4" but you are crossing to what looks like a subwoofer. What might push you towards a 4" rather than a 5" is the performance of the yet to be specified tweeter.
Thanks - so maybe I'm actually correct then, in thinking that Xmax is not a concern with these drivers at my SPL.
The 105dB@1m is roughly aimed at approaching the THX reference volume for main speakers - 85dB +20dB head room. I measured that I'd actually need 3dB more to reach the same SPL at my listening position, but I also figured that I can deduct 3dB 'per driver' assuming I shared the power handling about equally between bass and mid, which I understand would be at around 300Hz or so. Does this seem reasonable?
Cheers
kev
OK.
The Audax is a lot bigger (the Sd parameter). If the cones are the same size they must produce the same SPL with the same displacement.
The Audax is more efficient (the SPL parameter).
If you wish to use a small inefficient hi-fi midrange then use 2 to increase both the area and the power handling. This is fairly common for DIY hi-fi designs.
Thanks very much for taking the time to do that - am I right in understanding that you have needed two 10F drivers to reach the 105dB within their power rating?
Cheers
kev
Thanks for the other post too Andy. I think we are actually in agreement, its just that earlier you seemed to be saying that the audax with its lower xmax wouldn't be up to the same SPL as the smaller 10F with its much larger Xmax; perhaps I misunderstood what/where you thought my mistake was?
Cheers
Kev
Cheers
Kev
For the low 300 Hz crossover I needed two. If you want to crossover this low the tweeter will have to make strong case for a 4".
Thanks, thats in line with what I thought too, so its reassuring.
The tweeter hasn't been selected yet so I could certainly go larger for the mid and with a lower X-O to the tweeter to maintain dispersion. Or as you say, cross over higher to a small mid; that likely bass driver may be a 10" but supposedly its good to 1khz - I'm not sure I want to go that far TBH, but 500hz should be okay.
Cheers
Kev
Ah, I thought I'd given a serious answer, but from this I'm guessing you think I'm going way overboard? My intention is to make a Hi-Fi speaker that I'll not find under-powered on those occasions when I get the place to myself, and that will hold its head up for movies, but I certainly don't intend to make a party or PA speaker so thanks for stopping me if thats where I'm headed..
I measured my current system and at my listening position 85dB seems about right for a good loud session, it also seems to coincide with fairly safe long term listening limits and the THX recommendations for their reference volume - which apparently music studios are also starting to adopt, too. So it seemed a reasonable target to aim for.
However, the THX recommendation also states a further 20dB headroom; another thread suggested this could be treated as peak (before clipping) rather than sustained SPL, but even then its still quite high at 105dB. My SPL meter isn't capable of registering brief peaks so I've only got their word for it that 20dB headroom is necessary, but it does need quite a lot of power (albeit briefly) unless the drivers are reasonably sensitive...
So its all 'supposed' to be fairly logically worked out... but is it wrong or misguided?
Cheers
Kev
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Or perhaps a studio monitor? The K&H 0 400 someone mentioned in another thread has a 10" woofer in a ported 42 litre cabinet which is reasonably similar to the OPs proposal. The measurements on the RHS show roughly 115dB output at a 1% level of distortion. The OPs target of 105dB looks quite reasonable and "hi-fi".
The target is an average listening level of 85dB not 105dB. The 105dB comes from a wish to handle peaks cleanly.
PS I think I am going to have stop doing several things at once and answer posts straight away.
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