I dunno,....How about three of the Selenium 18" right next to the floor?
One facing forward and one in a side panel on each side, swept back 45 degrees. Then it's still "only" about 3 feet wide.. lower Fs and lots of swept area and "X" for eq. The panels could get less wide as they go up to keep from "enclosing" the midrange(s) .
One facing forward and one in a side panel on each side, swept back 45 degrees. Then it's still "only" about 3 feet wide.. lower Fs and lots of swept area and "X" for eq. The panels could get less wide as they go up to keep from "enclosing" the midrange(s) .
Hi
WOW – I always had a feeling that there is something else going on even at the reproduction of a single frequency.
Great to know its real.
To me 0,68% at 50 Hz isn't that low – an inexpensive and well documented Peerless SLS 12" can do 15mm of excursion within its "linear" range for example.
JohnK, many sounds reproduced are recorded through microphones. Without going too deep into maths could you please compare what's going on there in rather qualitative terms regarding Doppler and "self modulation" .
Are there cancellation effects to some extent when superimposing the mic and speaker distortion assuming an ideal full range driver for reproduction ?
Greetings
Michael
john k... said:
WOW – I always had a feeling that there is something else going on even at the reproduction of a single frequency.
Great to know its real.
To me 0,68% at 50 Hz isn't that low – an inexpensive and well documented Peerless SLS 12" can do 15mm of excursion within its "linear" range for example.
john k... said:
JohnK, many sounds reproduced are recorded through microphones. Without going too deep into maths could you please compare what's going on there in rather qualitative terms regarding Doppler and "self modulation" .
Are there cancellation effects to some extent when superimposing the mic and speaker distortion assuming an ideal full range driver for reproduction ?
Greetings
Michael
I'm posting a plot of doppler generated IM distortion vs frequency ratio for a driver reproducing two discrete tones, Flow and Fhigh.
The way to use this plot is to assume what you like for Flow. Then the plots is based on the excursion at Flow being equal to 50/Flow. So 50 Hz goes to 1 cm excursion (+/- 1cm), and 20 Hz would go to +/- 2.5 cm excursion. Then the plot shows the magnitude of the first order IM side bands Fhigh + or - Flow, vs. frequency ratio. So, for example, a driver radiating a 20 Hz tone with 2.5 cm excursion produces the same IM at 100 Hz (Frequency ratio = 5) as a driver radiating a 50 Hz tone with 1 cm excursion does at 250 Hz. IM rises very fast at first but then increases linearly with log frequency ratio. Above Frequency ratio of 2 or 3, IM increases/decreases by +6dB/-6dB each time the excursion is doubled/halved. Note that the IM is only dependent on the excursion at Flow and the ration of the tones.
I don’t have much knowledge on mikes but off the top of my head I would not expect Doppler generated IM distortion to be a problem because I can't imagine that the diaphragm of any mic moves very much at all. Best consult a mic expert. But measurement mikes certainly must introduce significantly less distortion then what they are measuring so I can’t imagine mikes posing any problems if correctly chosen for the application.
An externally hosted image should be here but it was not working when we last tested it.
The way to use this plot is to assume what you like for Flow. Then the plots is based on the excursion at Flow being equal to 50/Flow. So 50 Hz goes to 1 cm excursion (+/- 1cm), and 20 Hz would go to +/- 2.5 cm excursion. Then the plot shows the magnitude of the first order IM side bands Fhigh + or - Flow, vs. frequency ratio. So, for example, a driver radiating a 20 Hz tone with 2.5 cm excursion produces the same IM at 100 Hz (Frequency ratio = 5) as a driver radiating a 50 Hz tone with 1 cm excursion does at 250 Hz. IM rises very fast at first but then increases linearly with log frequency ratio. Above Frequency ratio of 2 or 3, IM increases/decreases by +6dB/-6dB each time the excursion is doubled/halved. Note that the IM is only dependent on the excursion at Flow and the ration of the tones.
I don’t have much knowledge on mikes but off the top of my head I would not expect Doppler generated IM distortion to be a problem because I can't imagine that the diaphragm of any mic moves very much at all. Best consult a mic expert. But measurement mikes certainly must introduce significantly less distortion then what they are measuring so I can’t imagine mikes posing any problems if correctly chosen for the application.
http://jantzen-audio.com/download/PD_JA8008_Oct07_v1-f.pdf
http://jantzen-audio.com/download/ja8008-tw034-kit/JA8008_TW034_article_v2_ja_web.pdf
Interesting JAntzen drivers. BUT about 94-95 dB efficient so maybe efficient enough using a pair?
They were mentioned here:
http://www.diyaudio.com/forums/showthread.php?postid=1377692#post1377692
http://jantzen-audio.com/download/ja8008-tw034-kit/JA8008_TW034_article_v2_ja_web.pdf
Interesting JAntzen drivers. BUT about 94-95 dB efficient so maybe efficient enough using a pair?
They were mentioned here:
http://www.diyaudio.com/forums/showthread.php?postid=1377692#post1377692
Magnetar said:
Nope. See
http://www.linkwitzlab.com/woofer3.htm
Even at 1" peak to peak (that is 25mm!) at 30Hz, Peerless is less than 10% 2nd and 3rd harmonic. At 12.5mm (close to your 90dB in OB) and at 50Hz it will be quite a bit better. Two of these in push-pull (mostly cancel even order harmonics) have been tested independently as 0.7% THD at 40Hz @ 91dB (less than 0.1% of "nonmusical" 3rd harmonic).
Quite 'HIFI', I'd say.
As anyone who heard Orion bass can tell you
Bratislav said:
Nope. See
http://www.linkwitzlab.com/woofer3.htm
Even at 1" peak to peak (that is 25mm!) at 30Hz, Peerless is less than 10% 2nd and 3rd harmonic. At 12.5mm (close to your 90dB in OB) and at 50Hz it will be quite a bit better. Two of these in push-pull (mostly cancel even order harmonics) have been tested independently as 0.7% THD at 40Hz @ 91dB.
Quite 'HIFI', I'd say.
As anyone who heard Orion bass can tell you
I eat my words - VERY impressive!
Hi
Adam, sorry can't remember brand nor type and have made no pics.
Have built some PA but never as OB - so no "real life experience" to recommend .
Greetings
Michael
AdamFelix said:
Very interresting, do you know where can i find more information about OB bassrigs?
What kind of tens or twelves would you recommend for such application?
Sorry for the ot.
best regards
Adam
Adam, sorry can't remember brand nor type and have made no pics.
Have built some PA but never as OB - so no "real life experience" to recommend .
Greetings
Michael
Variac said:
Thanks, Variac - food for thought there. By rolling off the side pairs around 100 Hz or lower, the standing-wave effects would be mitigated - especially if the volume is filled with recycled cotton, making it into a quasi-cardioid.
Made a phone call (405-789-0221) to Great Plains Audio, following up on the calls I made last week. I didn't want to spend much time on the phone last week, since Oklahoma City was still digging out from the Midwest ice storm and much of the city was without power - the person I spoke to had no power at home and their Internet connection at the office was down. So I kept it short.
This week, things seemed recovered in OK City, and there was time to ask about the status (and prices) of the current production Altec/GPA drivers:
515 Alnico. Price is $480, and these are special-order items. Delivery times are in months, not weeks, but they are in current production.
515 Ceramic. Price is $300 and in stock now.
416 Alnico. Price is $360 and availability is somewhat better than the 515 Alnico. I wasn't sure if these were in stock or not.
416 Ceramic. Price is $280 and in stock.
414 Ceramic (12" driver). Price is $260 and in stock.
390 (Altec 290) Phenolic-diaphragm compression driver for 300 Hz ~ 7 kHz applications. Price is $340 and in stock.
As for upper-bass and lower-midrange sonics, the nod seems to go to the 515 series, although the 416 and 414 are highly regarded. The cone of the 604 Duplex (which Great Plains is also making) is apparently most similar to the 416 (not the 515). I was asking about the differences between the 515 and 416 - I guess the 515 is designed for horn-loading theatre use, and has a lighter cone and more powerful magnet assembly than the 416, which appears to be designed for studio-monitor and home audio applications.
As for the OB system, still planning on a single 12 or 15" driver for high-quality use up to the 400 ~ 640 Hz crossover of the midrange, with an array of lower-quality drivers that are rolled in below the baffle peak.
The OB simulations are interesting, but they are only accurate for an OB used outdoors (a true free-field environment). In a room in a house, the results are different, with a lot more - and lot bumpier - bass response, due to floor, side wall, and rear wall reflections, and the standing waves of the listening room.
When I last visited Gary Pimm, he showed the in-room measurements of his OB subwoofer system (which correlated pretty well with what I heard). What surprised me was discovering the real dimensions of interest were the dimensions of the entire house, and not the dimensions of the living room. The size of the house (and not the room) set the effective LF cutoff - bass below 60 Hz seems to easily go right through interior doors, and can go through wood-framed exterior walls and single-glazed windows to some degree as well.
European-style brick, stone, and concrete construction is more rigid and certainly has different LF response. Similarly, a hifi system in a basement is in a more rigid enclosure with less loss through flexible walls and windows.
This is why equalization below 300 Hz is a good idea - wavelengths are long enough that the direct-arrival wave and room sound can no longer be distinguished from each other, and the mid to low bass region is strongly influenced by whether the listening room opens on to other rooms, and what kind of building materials are used for exterior walls and windows.
At some frequencies, the floor, side walls, and rear wall reflect, and at other frequencies, they become transparent and transmit energy into other rooms and into the outdoors. This real-world behaviour is different than a simulator, which typically assumes infinitely rigid reflecting boundaries.
If the listening room is built into an airtight solid-rock cave, that would be an accurate assumption. For rooms built with windows, doors, and wood-framed walls that open on to other rooms and the outdoors, the simulation loses accuracy at low frequencies, depending on the building materials and the relationship to other rooms and the outdoors. The most notorious example are suspended ceilings with built-in flourescent lights - these only reflect at high frequencies, and the lows go right into a plenum shared with all the other rooms that share the plenum space.
VW
Hi ... Yes, is on topic. Best subwoofer picture I've seen was a Bug with a woofer mounted to a board on the passenger side window opening.
He tuned the bass by rolling up and down the drivers side window. Was a huge chuckle at the time, but it stuck with me. Not sure the same principle cannot be done with a reasonable sized room and multiple speakers that would indeed require a huge ported box. And no, I don't mean IB speakers. Just thinking inside the box. I'll do a little UniBox to see how far off I am. I'm sure you guys with a whole lot more acoustical knowledge will tell me, too.
Zene
Hi ... Yes, is on topic. Best subwoofer picture I've seen was a Bug with a woofer mounted to a board on the passenger side window opening.
He tuned the bass by rolling up and down the drivers side window. Was a huge chuckle at the time, but it stuck with me. Not sure the same principle cannot be done with a reasonable sized room and multiple speakers that would indeed require a huge ported box. And no, I don't mean IB speakers. Just thinking inside the box. I'll do a little UniBox to see how far off I am. I'm sure you guys with a whole lot more acoustical knowledge will tell me, too.
Zene
That was Bill Woods...
Zene the horn (and picture) that you are referring to was designed by Bill Woods who was chief horn designer for Yorkville Sound and who now runs Acoustic Horn. Here is the link to Bill's site and the picture that you mentioned.
http://www.acoustichorn.com/
Zene the horn (and picture) that you are referring to was designed by Bill Woods who was chief horn designer for Yorkville Sound and who now runs Acoustic Horn. Here is the link to Bill's site and the picture that you mentioned.
http://www.acoustichorn.com/
Someone please check my math here.
10” Warrior
-------------------
Fs=65 Hz
Vas=0.555
Qes=0.915
Qts=0.867
Xmax=0.25”
SD=63.61
Eff=0.45%
$49
I am immediately suspect of the specs, as SD would indicate a 9" diameter cone. They are probably including the surround. Typical 10" is more 50-55 sq in (330-350cm2)
Xmax is most likely p-p. (6.35mm), so 3.2mm one way
http://www.partsexpress.com/pdf/290-403s.pdf
Best case scenario
Swept volume of 5 as used by Magnetar (63.61 x 5x .25)= 79.51 in3
More realistic case is 8" diameter cone, (55 x 5x .125) = 34.38 in3
A pair of XLS12 = 72.25 in3 displacement (466cm2 x 2 x 12.5mm 1 way)
Not far from the overly optimistic figure, but double the more realistic figure.
That is before distortion is measured.
Put them on the same size baffle...
cheers,
AJ
10” Warrior
-------------------
Fs=65 Hz
Vas=0.555
Qes=0.915
Qts=0.867
Xmax=0.25”
SD=63.61
Eff=0.45%
$49
I am immediately suspect of the specs, as SD would indicate a 9" diameter cone. They are probably including the surround. Typical 10" is more 50-55 sq in (330-350cm2)
Xmax is most likely p-p. (6.35mm), so 3.2mm one way
http://www.partsexpress.com/pdf/290-403s.pdf
Best case scenario
Swept volume of 5 as used by Magnetar (63.61 x 5x .25)= 79.51 in3
More realistic case is 8" diameter cone, (55 x 5x .125) = 34.38 in3
A pair of XLS12 = 72.25 in3 displacement (466cm2 x 2 x 12.5mm 1 way)
Not far from the overly optimistic figure, but double the more realistic figure.
That is before distortion is measured.
Put them on the same size baffle...
cheers,
AJ