I have been asked by the manufacture to help improve the sub with the parameters listed here. The first thing I plan on doing is increase the stiffness of the surround try to drop the Fs to about 30Hz. I expect the Qts to drop in conjunction with the Fs after I have increased the cone stiffness. Can anybody give me any suggestions on what to change? They are for car audio purposes and are DVC. The measurements below are the coils wired in series.
Revc = 4.1489 ohms
Fs = 35.5216 Hz should be 29 to 31 Hz
Zmax = 35.5411 ohms
Qes = 0.8036
Qms = 6.0807 should be 8.0 to 10.0
Qts = 0.7098 should be .5
Le = 2.3762 mH (at 1 kHz)
Diam = 254.0000 mm ( 10.0000 in )
Sd =50670.7504 mm^2( 78.5398 in^2)
Vas = 51.1113 L ( 1.8050 ft^3)
BL = 12.7749 N/A
Mms = 141.6356 g
Cms = 141.7366 uM/N
Kms = 7055.3384 N/M
Rms = 5.1987 R mechanical
Efficiency = 0.2748 %
Sensitivity= 86.3901 dB @1W/1m
Sensitivity= 89.2417 dB @2.83Vrms/1m
Revc = 4.1489 ohms
Fs = 35.5216 Hz should be 29 to 31 Hz
Zmax = 35.5411 ohms
Qes = 0.8036
Qms = 6.0807 should be 8.0 to 10.0
Qts = 0.7098 should be .5
Le = 2.3762 mH (at 1 kHz)
Diam = 254.0000 mm ( 10.0000 in )
Sd =50670.7504 mm^2( 78.5398 in^2)
Vas = 51.1113 L ( 1.8050 ft^3)
BL = 12.7749 N/A
Mms = 141.6356 g
Cms = 141.7366 uM/N
Kms = 7055.3384 N/M
Rms = 5.1987 R mechanical
Efficiency = 0.2748 %
Sensitivity= 86.3901 dB @1W/1m
Sensitivity= 89.2417 dB @2.83Vrms/1m
Fs Calc
Fb = 1/(2pi*(Cms*Mms)^.5)
Calculating Fb
Fb=35(Hz)=1/(2pi*((141.736/10^6)*(141.6356/10^3))^.5)
Assuming the Cms has doubled.
Fb=25(Hz)=1/(2pi*((2*141.736/10^6)*(141.6356/10^3))^.5)
Cms = 1/Kms
Your are correct because I have halfed the Kms.
Am I correct in my thinking or am I thinking to hard?
Fb = 1/(2pi*(Cms*Mms)^.5)
Calculating Fb
Fb=35(Hz)=1/(2pi*((141.736/10^6)*(141.6356/10^3))^.5)
Assuming the Cms has doubled.
Fb=25(Hz)=1/(2pi*((2*141.736/10^6)*(141.6356/10^3))^.5)
Cms = 1/Kms
Your are correct because I have halfed the Kms.
Am I correct in my thinking or am I thinking to hard?
To lower Fs try using softer/more compliant spiders, higher Mms will also lower Fs but this reduces efficency and should be avoided if possible.
Though a softer suspension conflicts with the desired Qms, which calls for a tighter suspension to raise it, which will raise Fs, requiring you to add mass to lower Fs again (which hurts efficiency).
Your desired parameters remind me of the alpine type-X, which has a very stiff suspension, really heavy Mms (396g) and poor efficiency (81.5db, measured) good thing it can handle a lot of power
What's the intended application for the sub, SPL,street beater,SQ?, and powerhandling?
Though a softer suspension conflicts with the desired Qms, which calls for a tighter suspension to raise it, which will raise Fs, requiring you to add mass to lower Fs again (which hurts efficiency).
Your desired parameters remind me of the alpine type-X, which has a very stiff suspension, really heavy Mms (396g) and poor efficiency (81.5db, measured) good thing it can handle a lot of power
What's the intended application for the sub, SPL,street beater,SQ?, and powerhandling?
Request help
Hi, I have a friend with a pair of old speaker (coming from a destroyed Altec Lansing Voice of the theatre box A7) I want to buy the speakers, but now I'm not sure what to do with these speaker, I have two ideas, and I don't know which is better idea...
1.-reconstruct the original box (I have the schematic of the A7 VOTT) but I need to find a replace tweeter or the original one
2.- Use the speaker and create two sub-woofer box
any ideas ?
--Sorry if I put this post here, but for some reason I only receive a -please search this forum first- message every time I want to post a new message
Hi, I have a friend with a pair of old speaker (coming from a destroyed Altec Lansing Voice of the theatre box A7) I want to buy the speakers, but now I'm not sure what to do with these speaker, I have two ideas, and I don't know which is better idea...
1.-reconstruct the original box (I have the schematic of the A7 VOTT) but I need to find a replace tweeter or the original one
2.- Use the speaker and create two sub-woofer box
any ideas ?
--Sorry if I put this post here, but for some reason I only receive a -please search this forum first- message every time I want to post a new message
@ jwatts
When you increase stiffness its lower Cms and you got higher Fs.
I belive you thought lower stiffness and higher Cms (mm/N) value.
First, why you want lower Fs?
When you change Cms and Fs, most of T/S parameters change.
Qms, Qes, Qts, Vas. In the way you got same Vb (closed or bass-reflex) in both cases. Because of that, I dont see purpose for that. For these kind of basses it is not always good to get higher Cms value, because of slower stoping of the cone after the signal is gone. Its the balance.
Now, for Fs=25 Hz, you must increase Cms (lower stiffness) some more than two times. (If you dont add mass to the cone)
Cms=0.286 mm/N
Fs=25 Hz
Qms=4.28
Qes=0.566
Qts=0.500
Vas=103.13L
SPL is same.
When you increase stiffness its lower Cms and you got higher Fs.
I belive you thought lower stiffness and higher Cms (mm/N) value.
First, why you want lower Fs?
When you change Cms and Fs, most of T/S parameters change.
Qms, Qes, Qts, Vas. In the way you got same Vb (closed or bass-reflex) in both cases. Because of that, I dont see purpose for that. For these kind of basses it is not always good to get higher Cms value, because of slower stoping of the cone after the signal is gone. Its the balance.
Now, for Fs=25 Hz, you must increase Cms (lower stiffness) some more than two times. (If you dont add mass to the cone)
Cms=0.286 mm/N
Fs=25 Hz
Qms=4.28
Qes=0.566
Qts=0.500
Vas=103.13L
SPL is same.
jwatts said:
They ask you for design help, and you come here?
Forward them my simple driver design spreadsheet. I can perhaps make them a special version, just for DVC drivers. The spreadsheet can be found at:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=17936&highlight=
My reason for coming here is. There are some very sharp people on this forum. Many are serious about audio and know their stuff. Several different eyes and ears are a good way to solve problems.
I am thinking what I have measured is probably nominal relative to the rest of the industry. I have measured a sub that is basically in the same class as these and are relatively close. I would still like to see the Fs and Qts come down for box size reasons and most SQ enclosure Fb at around 25Hz.
@Notax
Where can I get some equations to determine parameters based on the drivers mechanical properties, cone size, voice coil diameter etc.
I am thinking what I have measured is probably nominal relative to the rest of the industry. I have measured a sub that is basically in the same class as these and are relatively close. I would still like to see the Fs and Qts come down for box size reasons and most SQ enclosure Fb at around 25Hz.
@Notax
Where can I get some equations to determine parameters based on the drivers mechanical properties, cone size, voice coil diameter etc.
Cant find any really complet page. I learned from some books, like "Loudspeakers Cook Book", many others, links, pages, etc.
definitions
speakerplans
Qes=2*pi*Fs*Mms*Re/(BL*BL)
Qms=2*pi*Fs*Mms/Rms
Qts=Qms*Qes/(Qms+Qts)
Fs=1/(2*pi*sqr(Cms*Mms))
Vas=Ro*Cms*C*C*Sd*Sd (Ro - air density, C - speed of sound)
For measurements:
speaker workshop
definitions
speakerplans
Qes=2*pi*Fs*Mms*Re/(BL*BL)
Qms=2*pi*Fs*Mms/Rms
Qts=Qms*Qes/(Qms+Qts)
Fs=1/(2*pi*sqr(Cms*Mms))
Vas=Ro*Cms*C*C*Sd*Sd (Ro - air density, C - speed of sound)
For measurements:
speaker workshop
Your reason for coming here is because you have no idea what you are doing. Nothing wrong with that, but I'm having trouble imagining how you got into this situation. One wonders, what's in it for you? Are we educating you so you get paid or free product? 
One (or many ) can't solve a problem without knowing what the problem is. I suggest you start by defining the problem rather than just jumping to the conclusion that you need to stiffen the surround in order to lower Fs.
How about some pictures of the woofer in question, as well as the specs. A woofer is more than just the sum of its specs, you know. Besides, I'm sure all of us will be wanting to avoid a manufacturer that consults a novice to redesign their drivers.
One (or many
) can't solve a problem without knowing what the problem is. I suggest you start by defining the problem rather than just jumping to the conclusion that you need to stiffen the surround in order to lower Fs.How about some pictures of the woofer in question, as well as the specs. A woofer is more than just the sum of its specs, you know. Besides, I'm sure all of us will be wanting to avoid a manufacturer that consults a novice to redesign their drivers.
Thanks, I hope people enjoy it. It is interesting to see how T/S specs are interrelated, the effects of changing one or more fundamental parameters, etc....
Vikash has a website that details what he did. AFAIK, it never got past the experimental stage. I really enjoyed reading it though: paper rolls, CD diaphragms and rubber suspensions, a really nice looking magnet system...on a very nicely constructed website.
http://www.vikash.info/audio/
Vikash has a website that details what he did. AFAIK, it never got past the experimental stage. I really enjoyed reading it though: paper rolls, CD diaphragms and rubber suspensions, a really nice looking magnet system...on a very nicely constructed website.
http://www.vikash.info/audio/
Cheers Ron. It was fun as I recall. It did get taken a little further with a proper aluminium former made which improved things dramatically and I was also heading towards creating a proper diaphram and suspension. The only reason I stopped (postponed I should say) is that I started playing with FEMM. That hilighted the shortcomings in my motor enough to make me stop dead in my tracks.
I'll be back.
I'll be back.
Vikash whats FEMM?
Going back to the original question you can change the Qes of a driver with a negative output resistance amplifier.
There's some good tutorial stuff on this site:
http://www.diysubwoofers.org/
look at car subwoofers there's a thing called cabin gain....
Going back to the original question you can change the Qes of a driver with a negative output resistance amplifier.
There's some good tutorial stuff on this site:
http://www.diysubwoofers.org/
look at car subwoofers there's a thing called cabin gain....
FEMM models magnetic circuits: http://femm.foster-miller.net/
http://www.vikash.info/audio/transducer_design/day08.asp
Search for 'DIY Perthenon' for the mother of all blackhole motor design threads.
http://www.vikash.info/audio/transducer_design/day08.asp
Search for 'DIY Perthenon' for the mother of all blackhole motor design threads.
Vikash said:
Ha! Too cool. Reminds me of when I tried to create my own... um... driver. I used two twenty oz magnets mounted together in opposing fields. There was about 1/2" or so separating them. Around this "gap" I wrapped a selephane-like plastic with very thin aluminum foil "lines" attached (the voice coil so to speak).
The dcr was about 1.5 Ohms and I needed a heafty amp to drive it, so I used a Bryston 4B. I was amazed that I actually got sound from it! It lasted about 5 minutes before burning up, but it was an interesting experience.
Too bad this was before digital cameras and the Internet were around...
Mark
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