I checked the maths but cannot locate the error. I tried to restart the sheets and re-enter the data but it gives me the same 
The areas seem correct : the driver has 32cm² of surface, the base measures eleven times Sd, so it has to be (11*32cm²)/2.54 = 138.6 in²
The base measures 7.85*17.7 = 138.9 in² which is correct.
Which sheet is supposed to give the closest results ?
The areas seem correct : the driver has 32cm² of surface, the base measures eleven times Sd, so it has to be (11*32cm²)/2.54 = 138.6 in²
The base measures 7.85*17.7 = 138.9 in² which is correct.
Which sheet is supposed to give the closest results ?
Greets!
I just have this nifty little program open while designing, though of course it's only as accurate as your input: http://www.joshmadison.com/software/convert/
GM
I just have this nifty little program open while designing, though of course it's only as accurate as your input
: http://www.joshmadison.com/software/convert/GM
Yes my maths were wrong : I used a root where I should'nt have done it.
With the complete parameters I obtain the same responses.
To finalize the cabinet, damp high frequencies and limit internal resonances (impulse response), I will have to use 0,08 lb.ft3 of internal damping. Is it a correct value ?
GM : nice software ! I didn't test it right now but next time I need such a thing, I will download it ! I downloaded the same kind of thing from a schoolmate in my calculator and it's a nice tool
With the complete parameters I obtain the same responses.
To finalize the cabinet, damp high frequencies and limit internal resonances (impulse response), I will have to use 0,08 lb.ft3 of internal damping. Is it a correct value ?
GM : nice software ! I didn't test it right now but next time I need such a thing, I will download it ! I downloaded the same kind of thing from a schoolmate in my calculator and it's a nice tool
I realize that it is a little late making suggestions, but the last time I tried to look at your sims, I couldn't get in.
From your sims and RTA, I think that you are trying to tune WAY, WAY to low. A reasonable rule-of-thumb is to never try for F3 lower than 0.7*Fs, in this case 70-75Hz. When you have a spike at Fp, followed by a deep dip before recovery around Fs, this is a sure sign that the tuning is low. Try running a sim with F3 ~75Hz an a much smaller volume.
Yes, a stuffing density of 0.8 lb/ft^3 is too much. It is also indicative of a poor design. Once you design at a higher F3, you stuffing density will also go down.
Bob
From your sims and RTA, I think that you are trying to tune WAY, WAY to low. A reasonable rule-of-thumb is to never try for F3 lower than 0.7*Fs, in this case 70-75Hz. When you have a spike at Fp, followed by a deep dip before recovery around Fs, this is a sure sign that the tuning is low. Try running a sim with F3 ~75Hz an a much smaller volume.
Yes, a stuffing density of 0.8 lb/ft^3 is too much. It is also indicative of a poor design. Once you design at a higher F3, you stuffing density will also go down.
Bob
The amount of stuffing is not 0.8, but 0.08, arround 0.1 so. It makes 1.2kg/m3 which seems not so big for me. Applying this, the frequency response gets almost perfectly smoothed, and the spike is a little attenuated, despite it's still here as I need it.
I know the simulation ( http://youyoung21147.site.voila.fr/data_satW3_871S_port.PNG ) looks far too bad tuned, but according to my RTA measurements, it should compensate the difference observed between the simulation and the real measurements, hence the spike, as the drivers seems to have wrong announced specifications. Moreover, it should somehow resolve the problem of baffle step without any electronic component.
You can see that this simulation, despite the big spike at 68Hz, doesn't go lower than the first one I did to build my center speaker. I tried to make a very low tuning which seems to work pretty well with the Cyburgs-needle enclosure, but with a dip that doesn't go lower than the driver's typical efficiency.
The only thing I don't really like in this enclosure is the quite big internal volume. If not correctly damped, it may cause undesired resonnances from the box itself.
I will draw the plans right now, and build the enclosure to give it a try.
Thanks for all these advice !
I know the simulation ( http://youyoung21147.site.voila.fr/data_satW3_871S_port.PNG ) looks far too bad tuned, but according to my RTA measurements, it should compensate the difference observed between the simulation and the real measurements, hence the spike, as the drivers seems to have wrong announced specifications. Moreover, it should somehow resolve the problem of baffle step without any electronic component.
You can see that this simulation, despite the big spike at 68Hz, doesn't go lower than the first one I did to build my center speaker. I tried to make a very low tuning which seems to work pretty well with the Cyburgs-needle enclosure, but with a dip that doesn't go lower than the driver's typical efficiency.
The only thing I don't really like in this enclosure is the quite big internal volume. If not correctly damped, it may cause undesired resonnances from the box itself.
I will draw the plans right now, and build the enclosure to give it a try.
Thanks for all these advice !
I built a prototype based on the simulation this morning, in a folded configuration and I am using a brand new driver that needs to be broken in, its suspension is really hard !
The cabinet isn't even sealed, and there is no stuffing inside.
I didn't make any measurement right now, but I can already say that it gives a nice bass extension. Maybe linearity is a little worse but I get more bass.
I was afraid of "box noises" because of the large volume, but there is almost no box noise, mainly because the port is really large and therefore lets very much air pass without problem.
I think it's a nice enclosure but I need to make more measurements and finish the cabinet correctly.
I'm too tired right now, so, Good nite !
The cabinet isn't even sealed, and there is no stuffing inside.
I didn't make any measurement right now, but I can already say that it gives a nice bass extension. Maybe linearity is a little worse but I get more bass.
I was afraid of "box noises" because of the large volume, but there is almost no box noise, mainly because the port is really large and therefore lets very much air pass without problem.
I think it's a nice enclosure but I need to make more measurements and finish the cabinet correctly.
I'm too tired right now, so, Good nite !
I sealed the enclosure this afternoon and WOUAOUH !! it works exactly like I wanted it to work : it goes deep (70Hz -0dB) and mainly, the peak in the simulation exactly compensates baffle step diffraction, so I don't need any awful filter.
It really gives the punch that music needs !
I suppose building the second one will help increasing the bass response !
Here's a photo : http://youyoung21147.site.voila.fr/DSCF2747.JPG
Placed like on the photo, the bass extends down to 58Hz, then the awful JBL subwoofer under it does the job (only for the home theater, I prefer not to switch it on to listen to music. Grrr... How I hate bass reflex ! )
I publish the plans as soon as I have adjusted smoothly the port length, to give people the best configuration.
My RTA mesurements are not finished and I get some room resonnances so the response doesn't appear as smooth as it is, though I know linearity isn't as good as with my center speaker.
I have to try several positions and make an average, like I did for the center speaker measurements.
It really gives the punch that music needs !
I suppose building the second one will help increasing the bass response !
Here's a photo : http://youyoung21147.site.voila.fr/DSCF2747.JPG
Placed like on the photo, the bass extends down to 58Hz, then the awful JBL subwoofer under it does the job (only for the home theater, I prefer not to switch it on to listen to music. Grrr... How I hate bass reflex ! )
I publish the plans as soon as I have adjusted smoothly the port length, to give people the best configuration.
My RTA mesurements are not finished and I get some room resonnances so the response doesn't appear as smooth as it is, though I know linearity isn't as good as with my center speaker.
I have to try several positions and make an average, like I did for the center speaker measurements.
Yep, even a working design : I have built two different enclosures for my home theater.
Have a look here :
http://www.freazer.com/perso/youyoung/hcw3871s.html
Greets !
Have a look here :
http://www.freazer.com/perso/youyoung/hcw3871s.html
Greets !
Glad you like them !!
It is the best value/price speaker set I have ever heard/built.
My favorites are the big ones because they don't need BSC at all if you place them correctly.
Off course you won't play ultra-loud music on them, and they won't make the walls tumble, but they are surprizingly refined for such cheap speakers.
Little precision BTW : highs do reach 20kHz, but when I took those measurements I didn't know that I had to calibrate the sound card
It is the best value/price speaker set I have ever heard/built.
My favorites are the big ones because they don't need BSC at all if you place them correctly.
Off course you won't play ultra-loud music on them, and they won't make the walls tumble, but they are surprizingly refined for such cheap speakers.
Little precision BTW : highs do reach 20kHz, but when I took those measurements I didn't know that I had to calibrate the sound card
Just to let you know, I actually built a pair of the center version for my sister. They are now used as computer/tv/ipod speakers and they are coupled with the t-amp. They actually have good bass as long as they are in corners. In my parents house, they are the clearest sounding speakers we've ever owned. The system is really revealing showing a lot of faults in many recordings and broadcasts.
Overall greats speakers especially as a first builder.
(Notice the High Quality $10,000 HiFi Rack constructed from very expensive materials)
Overall greats speakers especially as a first builder.
(Notice the High Quality $10,000 HiFi Rack constructed from very expensive materials)
Attachments
Nice !
I'm glad someone built those speakers and is satisfied with them.
This use as desk speakers is pretty what they could be intended for : not to big and good sounding in a small place.
Mine is still working as center speaker in my home theater.
But I still prefer the big ones I've built after.
I'm still very amazed by the details and imaging of the W3871S compared to my 5*more expensive FX120. Really a nice driver !
Greets !
I'm glad someone built those speakers and is satisfied with them.
This use as desk speakers is pretty what they could be intended for : not to big and good sounding in a small place.
Mine is still working as center speaker in my home theater.
But I still prefer the big ones I've built after.
I'm still very amazed by the details and imaging of the W3871S compared to my 5*more expensive FX120. Really a nice driver !
Greets !
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