Just moving it with my fingers most of the cone easily pushes out beyond the front mount but just to the front mount it measures around 22mm. I don't think I have another way of testing it without building a box. It does push back far though - maybe 3 or 4mm is this a more realistic movement?
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I have just read Stephen Buntings article on line arrays which included this graph showing the listening distance at which line arrays change from near field to far field sources, i.e. 3dB per doubling of distance to 6dB, compared to the length of the array and frequency.
A 1m long array is effectively far field at 1 m for all frequencies below 1Khz! It appears that there is not much benefit in a small line array except for increasing efficiency.
Tim.
A 1m long array is effectively far field at 1 m for all frequencies below 1Khz! It appears that there is not much benefit in a small line array except for increasing efficiency.
Tim.
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I heard some OB PA speakers ouside, and the SQ was great.
Max output is another issue for some, but apparently not here - ie just background levels
But maybe cross the 8 inchers much lower than you thought, due to beaming. SL crosses 8 inchers in OBs at about 1400 - 1500 Hz
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Why such limit? What about attic and basement? 😉
I did many experiments with line arrays, and can swear that even 1 meter high array of 12 mm drivers result in properties of line arrays. I use such an array as a tweeter in center channel. Right and left channels consist of 8 each 4.5" fullrangers, and 16 of Foster speakers for Dell notebooks as tweeters. Still, very low distortion due to greatly minimized excursions for needed SPL level, still wide "sweet area" instead of "sweet spot", and almost unnoticeable difference between standing and sitting listening (well, you can note it in dynamics, while sitting down, or standing up).
to flatten the bass, at the expense of sensitivity, how is the best choice of values of a series resistor estimated?
"Confession for asking": to to try my own OBs, temporarily passive with a reasonable power tube amp, in a small room
1 ohm in series?
though I believe that this is NOT ideal because it reduces sensitivity AND transient response
"Confession for asking": to to try my own OBs, temporarily passive with a reasonable power tube amp, in a small room
1 ohm in series?
though I believe that this is NOT ideal because it reduces sensitivity AND transient response
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Hi,
For the last time I will repeat OB's for outside use are a waste of time,
especially considering low driving power and that is fed by batteries.
The extra bass driver is an excuse for even more conjecture.
I'm not going there, its just more nonsense.
Given the application, I've described what to do.
rgds, sreten.
For the last time I will repeat OB's for outside use are a waste of time,
especially considering low driving power and that is fed by batteries.
The extra bass driver is an excuse for even more conjecture.
I'm not going there, its just more nonsense.
Given the application, I've described what to do.
rgds, sreten.
sreten
I think we understand your POV, we just don't all agree.
I'd do as one suggested, and put two a side in boxes
I think we understand your POV, we just don't all agree.
I'd do as one suggested, and put two a side in boxes
Floor & ceiling act as acoustic mirrors, tripling the effective height of the arrary
dave
A valve amp will have a reasonably high output impedance (usually a few ohms), that act as a series resistor anyway.
All I can say is this:
As you add series resistance, Qes increases. Qts (being calculated as 1/(1/Qe + 1/Qm) ) increases towards Qms.
Following this, adding series resistors will raise Qts, giving some bass output on an open baffle, with no eq required, as the Eminence Alpha 15A does (Qts=1.2).
Yes, a series resistor will lose a little sensitivity. But it will negate the need for eq. Pick your poison (or build a variable output impedance amplifier).
Chris
Hi,
Sorry if I sounded somewhat shirty, but the actual application is being ignored.
Is OB possible for a PA system ? Of course it is. How do you do that well ?
That is another matter. Here the drivers and amplification IMO do not suit.
For long battery life you want maximum efficiency. For outdoors you want
the maximum bass efficiency and bass SPL limits of the drivers to be used.
I guess you could stick the big driver in a vented box and use it as a sub.
You could then have the 4x8" arrays in tall OB's, minimum I'd say 2ft wide.
Probably the best amplification to run off a 12V battery is a 4 channel
car amplifier - one that bridges two channels for bass, the other two
left and right - and also has built in active crossovers and levels.
(You can exploit the active c/o's to remove the baffle hump, i.e.
use a somewhat higher high pass frequency than the low pass.)
For the above the lower the power the better, as it will be more efficient
running near its maximum limits than a higher powered amplifier cruising.
rgds, sreten.
I now have an H-frame subwoofer! I made it from a piece of left-over beach work top. Don't look too close as my joinery skills are far from perfect. The excess white wood glue is an attempt to seal the gaps = it will dry clear.
The H-frame is based on Martin King's design. I shortened it slightly to tune the resonance and FPeak to around 310Hz. The cavity cross-section is 40.5 cm x 40.5 cm. The overall depth is 31.5cm giving an actual cavity depth of 14.25cm and effective depth (at low frequencies) of around 28cm. With a 12dB/octave low-pass filter set at 145Hz, the effective crossover frequency should be a little over 400 Hz. The sub will have its own amp and PSU.
The idea in raising the top reach of the sub-woofer is to allow smaller open-baffle satellites. I believe these should have an effective diameter to match the H-frame, i.e. 56cm. Using the same fpeak bump to move the effective crossover frequency down, I believe the actual high-pass filter needs to be set around 580 Hz.
Tim.
The H-frame is based on Martin King's design. I shortened it slightly to tune the resonance and FPeak to around 310Hz. The cavity cross-section is 40.5 cm x 40.5 cm. The overall depth is 31.5cm giving an actual cavity depth of 14.25cm and effective depth (at low frequencies) of around 28cm. With a 12dB/octave low-pass filter set at 145Hz, the effective crossover frequency should be a little over 400 Hz. The sub will have its own amp and PSU.
The idea in raising the top reach of the sub-woofer is to allow smaller open-baffle satellites. I believe these should have an effective diameter to match the H-frame, i.e. 56cm. Using the same fpeak bump to move the effective crossover frequency down, I believe the actual high-pass filter needs to be set around 580 Hz.
Tim.
Attachments
Well, thanks for asking. It went fine and the sound system was considered a marvel by those technically or sonically inclined. I have the system in my office now hooked up to my Mac.
The experience gave me the confidence to cut two 6" holes in my living room wall and install flush-mounted full-range drivers powered by a 'Class-D' amp for a truly purist experience!
I get the impression you don't believe me. I put them near but not in the corners to emphasise the bass (boundary effect x 2) above other frequencies. Being old and because treble does enjoy the baffle boost, this is boosted at the amp instead. So not perfectly pure but a superb sounding system for around £30!
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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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Nameless Chinese imports from yourspares.co.uk described as "Black 204 mm 15 W Full Range Round Speaker (8 Ohm) - L032". They are also on eBay with similar descriptions. I have just realised that makes them 8" not 6". It is not just the hearing that is going 🙂
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Tim,
I hope the neighbours didn't find any chicken bones in their garden like the last time you did a BBQ in Cambridge....😀
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