I just finished Martins origanal OB paper. Looks like these woofs are not the best for OB....However, I do have a number of active crossovers laying about that I think I will use. I can also borrow an EQ from a friend, so that will help.
Now, what I could not find is how to size an "H" from from 2 woofers per side. Any suggestions? I have way too many projects going, but this one I don't have to spend money on and right now that is great. Cheers.
Now, what I could not find is how to size an "H" from from 2 woofers per side. Any suggestions? I have way too many projects going, but this one I don't have to spend money on and right now that is great. Cheers.
OK, Cerwin Vaga just emailed me to say they sent the wrong driver data. Here is the right data. With an Fs of only 52, plus a 88db SPL, this does not look like it would work very well at all. Maybe I am wrong. What do you think?
Brand Cerwin-Vega
Model S-10
Description Cast frame, paper cone and foam surround
Range / type Sub
Typical use Car
Recomended enclosure
Series
Manufacturer Cerwin-Vega
Order nr
Production status Discontinued
Nom. diamerer [inch] 10
Vas [Liters] 19.8
Qts 0.6525
Qes 0.714
Qms 7.571
Fs [Hz] 52
Sensitivity [dB] 88
Max Power [W] 150
xmax [mm] 4
Moving mass [g] 72.13
Disp area [m2] 0.033
Re [ohm] 3
Z [ohm]
L [mH] 0.001
Bl [Tm] 9.951
Brand Cerwin-Vega
Model S-10
Description Cast frame, paper cone and foam surround
Range / type Sub
Typical use Car
Recomended enclosure
Series
Manufacturer Cerwin-Vega
Order nr
Production status Discontinued
Nom. diamerer [inch] 10
Vas [Liters] 19.8
Qts 0.6525
Qes 0.714
Qms 7.571
Fs [Hz] 52
Sensitivity [dB] 88
Max Power [W] 150
xmax [mm] 4
Moving mass [g] 72.13
Disp area [m2] 0.033
Re [ohm] 3
Z [ohm]
L [mH] 0.001
Bl [Tm] 9.951
If your going active, you don't need to worry about qts at all. Similarly with Fs - 52Hz is a little high, but that doesn't matter as much, because you aren't going to be able to run them that low anyways. 88dB SPL seems fine to me.
I'd mostly be concerned about the 4mm Xmax - you have fairly limited volume displacement. 2 per side should be adequate for decent SPL to 60Hz, which actually is probably great for a quick project.
WRT the H-frame dimensions, MJK has a spreadsheet for exact calculations. I have it, but not available to me now. But you can easily just estimate them - basically, the bigger the better, particularly in the plane of the drivers. IE, you get more SPL for going wider and taller rather than deeper. But as a first guess, 14" by 14" by 20" would probably work nicely.
I'd mostly be concerned about the 4mm Xmax - you have fairly limited volume displacement. 2 per side should be adequate for decent SPL to 60Hz, which actually is probably great for a quick project.
WRT the H-frame dimensions, MJK has a spreadsheet for exact calculations. I have it, but not available to me now. But you can easily just estimate them - basically, the bigger the better, particularly in the plane of the drivers. IE, you get more SPL for going wider and taller rather than deeper. But as a first guess, 14" by 14" by 20" would probably work nicely.
Thanks Cuibono. That sounds simple enough. When I build the H frame, should there be a divider board between the two woofs? and to H frames have a top as well as sides? I am not going after high SPL for this system. It will be in my living room to read the paper by. I have subs that can augment below 60hz as well. Cheers.
Why do you say that qts only matters if you are going passive on the woofer? I'm still trying to learn about others' OBs...
Presumably because if you go active, you can more easily EQ the bass response you want from the woofers....you can electronically boost the bass response, assuming you don't run out of xmax first. Of course, you can do that with a passive xover, too - think KEFs Qube, and some McIntosh speakers.
So maybe I'm lost, too.... MJK's actively crossed over systems still used high Qts woofers.
I'm just getting my OB system running. I've mentioned elsewhere, but I'm using a pair of 15's from Jack Hidley (scroll down to the "Jensen" 15"). They are only $60, efficient, have a decent Xmax, and are very easy on the eyes for such a cheap woofer. Do keep in mind they are 6 ohms. The Qts is pretty low, but that is less of a problem than the sims led me to believe. Right now I've got a 18" baffle with 10" wings (a U). I'm using the miniDSP for a crossover (only on the woofers, line level passive on top, the system is biamped). I thought I'd have to do a bunch of shelving, but a simple second order setting at 100hz is getting me essentially flat response from my acoustic crossover point of 150ish down to the 40's! Much easier than I anticipated. I'm using Room EQ Wizard from Home Theater Shack for measurements. I suppose the woofer is effectively 88-90db efficient used this way. I've got a whopping 7 watts into them right now. I am very happy with them for my setup. I suspect they'd really shine with more power, given their excursion advantage over the cheap PA woofers. I haven't seen a better OB woofer for the price.
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
Paul
Wild Burro Audio Labs - DIY Full Range Speakers
I would say that this depends on what you're building with. Do you really "NEED" the shelf? Maybe not, but if you plan on it and incorporate it into the build, it will definitely help making the H-Frame more structurally rigid. Less flex is a good thing.
I think if you get the H-Frame right, you shouldn't need a subwoofer for a natural, balanced sound. Your S-10's may have an Fs of 52Hz, but by going with an H-Frame you can utilize quarter-wave design and get lower than that. Remember: The low E-string on a bass is 41.2Hz. If you're not doing home theatre, then you should be able to accomplish everything you need.
A lot of people have criticized open baffle bass as weak, but I think their ears are conditioned to what they hear on the radio in their cars. Radio stations tend to run some pretty serious EQ curves, with the bass pumped up, that is actually not natural (my local Public Radio station even does this). Go to an orchestra concert and you will hear that what is natural is balanced bass- never overbearing.
Hi gvimhoof,all
If the H-Frames fails performance-wise, after building the proposed quite large sized quarter wave design, there is of course a possibility to revert to other types. See the picture:This suggestion would really pass the E-string bass without x-max strain while covering the mid-bass and half of the upper-bass to about 120 Hz.
Two CV-S10 in a H-Frame with 10 dB marginal is only reaching 92 dB SPL-max at 42 Hz, corresponding to a low 60 dB phone loudness level (bedroom level?
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OK, well. A friend of mine acctually has the CV 10.8 woofers at his house and I just found out that he is in Europe for a week. So, I am still moving forward with this cheap OB project but using a pair of Technics 4500a cabs with the woofer that came with them. I've was going to use the 4500a in my garage but it can wait until Joe gets back. Should be interesting. Here are pix of the 4500. The no longer have the tweeters so that is not an issue. I will just make a small baffle board for the mids and tweets I am planning on using. Cheers.
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Wow, thanks Bjorno. This looks very doable. My friend who is traveling has the woofers so I will not be able to get to this for a nother week or so, but dang, thanks for the help. I'll be posting pix as I go.
OK, a couple questions.
The way the H frame is laid out on the page, it is 21" wide and 11" tall, can I reverse that without issues? So flip it up so it is 21" tall???
Also, not knowing the program you used, is it for two woofers or just one?
Thanks again for your help.
OK, a couple questions.
The way the H frame is laid out on the page, it is 21" wide and 11" tall, can I reverse that without issues? So flip it up so it is 21" tall???
Also, not knowing the program you used, is it for two woofers or just one?
Thanks again for your help.
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Yes you can reverse with almost no performance differences, see the picture.
The program can be found here:
Quarter Wavelength Loudspeaker Design
The H-Frame simulation uses 2 drivers as seen in the T/S data.
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Hey Bjorno, I got all tangled up at work and am just now getting back to this project. When I am looking at your last post about the plots, it shows that the front goes down low with a little bump in it and the back terminous goes low and is flat, but the whole system peaks at around 150hz and rolls over below that. Is that the total bass responce will look like (sound like)? My midrange drivers go down to 70hz or so, so I am confused if the bass box will do anything for the whole system. Forgive my ignorance. Cheers.
You can raise Qts easily. Use resistor or inductor with thin wire
Calculate new Qts with Series Resistor
You can also lower fs if you cut some triangles out of the spider.
The midrange will have a hard job hitting 70 hz in OB. My suggestion is too use the CVs as low midrange at use dubwoofers below 100 hz. Midrange might be usable from 300 or 400 hz.
Calculate new Qts with Series Resistor
You can also lower fs if you cut some triangles out of the spider.
The midrange will have a hard job hitting 70 hz in OB. My suggestion is too use the CVs as low midrange at use dubwoofers below 100 hz. Midrange might be usable from 300 or 400 hz.