Pure Audio Project has a nice OB design. I remember seeing something like MA10 mated with Eminence Alpha 15.
yes, i know them, but those prices are way to much. I can build that way cheaper, even if i hire someone to do it better than i can...
Dave of P10 when making a fullrange with helper woofer ( FAst) often uses series connection crossovers . Pano in his " Simple, fast Ob..." thread underlines the first needs of the project/Ob concept.
So I guess a big inductor for a start and some 10-100 uF caps 🙄
I don't know how a 12 dB/oct high pass with a big inductor after the cap
( about 90uF/10 mH ) may damage the signal ( phase after transduction ...reactance at rising impedance)
or whether a simple 6 dB/oct serialized, like two 47/100 uF caps in series would perform decently 😕
Perhaps you can start with a 12mH inductor for the woofer and a 220uF cap for the fullrange driver?
I've built a prototype using CHR70 and an Aurasound 6 1/2" woofer using similar values ages ago. Take care of the 6dB/octave rolloff with the inductor, there's little you can do about the 18dB/octave below Fs of the woofer; the cap is there just to protect the driver from overexcursion, you'll be fine without it if you don't turn it all the way up (others may disagree though)
cheapest xover is linelevel with plugs that have 2nd order xovers built in
from Harrison Labs, Co. You need 2 amps, but those are cheap to come by.
from Harrison Labs, Co. You need 2 amps, but those are cheap to come by.
Note that the Harrison Labs devices are non-optimized PLLXO, it is cheaper & one can make a more optimized version from scratch.
TLS.org | Passive Line-Level Crossover
When using this kind of limited XO one must take care to design the speaker for their use. We use them quite often, but usually 1st order.
dave
i don't think prefab filters will do the job like it should. I will build my own passive speaker level filters. I did that before for closed boxes (pa boxes i build for someone), and altough i'm not a specialist i and my "client" were happy with the result. Just do the math and buy good components and it surely will be better.
But i'm still studying the case. Don't expect the build before the new year. I'm still rather new to this DIY thing and like to study the subject till i'm rather sure what i'm doing.
As far as i understand, i need to make sure to count the natural slope of the drivers, and make the woofer section double as efficient (+10dB) as the fullrange ob. I'm now thinking by using the alpair 10p till +/- 100Hz or a bit higher and add a H frame subwoofer that can at least go till an fs of 30hz. The Alpha 15A won't go that low, but other drivers may do it. Any suggestions (with a reasonable price)?
But i'm still studying the case. Don't expect the build before the new year. I'm still rather new to this DIY thing and like to study the subject till i'm rather sure what i'm doing.
As far as i understand, i need to make sure to count the natural slope of the drivers, and make the woofer section double as efficient (+10dB) as the fullrange ob. I'm now thinking by using the alpair 10p till +/- 100Hz or a bit higher and add a H frame subwoofer that can at least go till an fs of 30hz. The Alpha 15A won't go that low, but other drivers may do it. Any suggestions (with a reasonable price)?
The 10p will not make 100 hz on an OB. I dont think it will do 200 either.
Read MJ Kings treatise on OB. Read it several times.
the goldwood 1858 might be the woofer for you.
I think the harrison lab filters are fine and very convenient, but like Planet 10 says,
they must be chosen carefully based on the impedances of the amps used. Harrsisn Labs (NO connection to them) has a chart to use. but as you say,if you know how to make them I am sure you could use better components.
Read MJ Kings treatise on OB. Read it several times.
the goldwood 1858 might be the woofer for you.
I think the harrison lab filters are fine and very convenient, but like Planet 10 says,
they must be chosen carefully based on the impedances of the amps used. Harrsisn Labs (NO connection to them) has a chart to use. but as you say,if you know how to make them I am sure you could use better components.
i've red it several times, and if the baffle is big enough, it should do it i understand. the freq plot free air on the Markaudio spec sheet says the driver start to drop just above 100hz if i can view right.
When i do a sim in Thorsten Loesch Open Baffle Spreadsheet i got even beter results.
I nowhere read that the bass is less than the driver if the baffle is big enough. And that is what i want to do, build a huge baffle.
What do i see wrong?
(edit: better printscreen)
When i do a sim in Thorsten Loesch Open Baffle Spreadsheet i got even beter results.
I nowhere read that the bass is less than the driver if the baffle is big enough. And that is what i want to do, build a huge baffle.
What do i see wrong?
(edit: better printscreen)
Attachments
Last edited:
True.At diyFEST one year we assembled a 17' wide baffle (1,1m tall), and with a pair of Korean made OB 6.5" drivers gotsome amazing bass.
dave
I didnt realize you were going to use 40 x 40" baffles. On something that big
150 hz. seems possible.
150 hz. seems possible.
Of course you realize that the lower you cross over the less protection for the fullranger. I fully agree that the best quality sound is with a low crossover, but if you are looking for quantity..............................
Like said before, i don't need a very loud set, i have very sensitive ears and mostly stay arround 85dB. In my actual case that means my Marantz PM5004 is max only 25% open (25% of 45watt) and my speakers are Alpair 10M used fullrange without sub in a ported box and they get hardly get stressed at all. I can get deep bass out of it with no distortion, with this fragile speakers.
After moving my living room will be double size, but i will pair the alpair 10p drivers in a OB with a subwoofer (ob or ported, still not decided), so the load will be divided and maybe i start using more amp power devided over the fullrange and the woofer. As my amp is only 45 wat and the 10P can handle 30 and the woofer much more, this should not be an issue i think. But i know those Alpairs are fragile for overload... My actual boxes may end up in my kitchen as kitchen speakers on the same amp (a vs b connectors) and then i can retire my old beaten up tannoy reveal monitor speakers...
After moving my living room will be double size, but i will pair the alpair 10p drivers in a OB with a subwoofer (ob or ported, still not decided), so the load will be divided and maybe i start using more amp power devided over the fullrange and the woofer. As my amp is only 45 wat and the 10P can handle 30 and the woofer much more, this should not be an issue i think. But i know those Alpairs are fragile for overload... My actual boxes may end up in my kitchen as kitchen speakers on the same amp (a vs b connectors) and then i can retire my old beaten up tannoy reveal monitor speakers...
Phisical dimensions are important, I don't use cables longer than 2 m.
Same can be said about crossover between a sub and a satellite or whatever mid-wf/treble combo
the size of the inductor and capacitor needed for correct crossovering, i.e. -6dB at crossover point to correctly sum flat, brings some counterfeits such phase change and others...that's why it's easier to use two amplifiers and electronic crossover at line level.
A woofer "cut" at 300 Hz or more is more easy to filter, as the midrange thereafter. It's about phisical dimensions of the components and the values associated
Then there's the room that houses all these parts
when thinking about OB you should think of having another room behind the speaker
that should act as a "sound extinguisher". Always, it's better to place the OB at 1,5 m or more from the walls
when thinking about OB you should think of having another room behind the speaker
that should act as a "sound extinguisher". Always, it's better to place the OB at 1,5 m or more from the walls
You can't judge the amount of power from the volume control setting as it is a logarithmic control, 25 w would be painfully loud.
dave
- Status
- Not open for further replies.