(@planet10) Dave,
A lot of subject in your posts,
The driver selection is the biggest issue in this design. It is a two way and find a good balance is hard. I think it is harder to design than a three way OB.
The MAOP 5 worth every penny, and if you compare it to a Scandinavian 1" tweeter the price is not so high. The sound of the MAOP is very neutral and realistic.
I have other open baffle and I replace the tweeter by the ALPAIR 5.3 just to test, the treble is as good. And I don't make any optimization. I like a lot cone tweeter because I find them more realistic than 1" cone tweeter.
There is a physical reason 28cm² against 7cm², but dome tweeter has the advantage of a better dispersion, less beaming in the high frequency. In a dipole application the cone tweeter is a dipole, the dispersion is "better" and a tweeter is a monopole, a rear fire tweeter could make the job.
The second point is the crossover frequency, I want to keep as good as possible the tweeter side of the mid-tweeter, i cut the higher as possible the mid tweeter.
It is a deliberated choice to keep the drivers with the same 4 octaves of coverage. Not try to go low with the woofer. 50Hz is low enough for an OB. A 15" can go up 800Hz.
I keep the crossover point between 500-800Hz, the mid tweeter has also the same 4 octave coverage.
This point of operating frequency is also applicable to a conventional speaker. Some manufacturer like PURIFI try to overcome these rule, low bass and good mid-treble but in such price ?
The woofer selection is based on my experience, I built several OB in the past and yes an alpha 15 in a OB bug me a little because you look the magnitude is flat but you should look the phase.
In a closed box you have Bessel, Butteworth, Tchebychev alignment in the bass. Why don't take it into account in Open baffle ? S. Linkwitz (RIP) treats well the subject. In its active equalization he uses Bessel response, the best linear phase Qt=0.5.
In my world I try to keep QT < 0.8 in order to have a phase as linear as possible, no peak in the group delay. I think an Eminence beta 15 should be a better choice for phase response.
Second thing I like light cone with big woofer. I found the woofer has more definition, it could be a false assertion. This is the reason I hesitate to use a 15ob350, I'll test it in the future.
Third point yes an OB is sensitive to size for the sensitivity, dispersion, and crossover point when use passive components. I have a big constraint no baffle larger than 15" in my room, look like a WAF constraint. It resolves a lot of issue. Note for the crossover if it looks normal the mid-tweeter, for the bass you have a big compensation to apply to linearized the response of the woofer, like a big baffle step.
An other point is the drivers I use are made in China, a reason for the lower price if compare to Eminence woofer series ?
@mayhem13 Thank you ! Yes i like the result and my wife who have a discreet listening, not as attentive as mine, likes the sound, where you hear voices, you have the feeling the people are talking front of you.
A lot of subject in your posts,
The driver selection is the biggest issue in this design. It is a two way and find a good balance is hard. I think it is harder to design than a three way OB.
The MAOP 5 worth every penny, and if you compare it to a Scandinavian 1" tweeter the price is not so high. The sound of the MAOP is very neutral and realistic.
I have other open baffle and I replace the tweeter by the ALPAIR 5.3 just to test, the treble is as good. And I don't make any optimization. I like a lot cone tweeter because I find them more realistic than 1" cone tweeter.
There is a physical reason 28cm² against 7cm², but dome tweeter has the advantage of a better dispersion, less beaming in the high frequency. In a dipole application the cone tweeter is a dipole, the dispersion is "better" and a tweeter is a monopole, a rear fire tweeter could make the job.
The second point is the crossover frequency, I want to keep as good as possible the tweeter side of the mid-tweeter, i cut the higher as possible the mid tweeter.
It is a deliberated choice to keep the drivers with the same 4 octaves of coverage. Not try to go low with the woofer. 50Hz is low enough for an OB. A 15" can go up 800Hz.
I keep the crossover point between 500-800Hz, the mid tweeter has also the same 4 octave coverage.
This point of operating frequency is also applicable to a conventional speaker. Some manufacturer like PURIFI try to overcome these rule, low bass and good mid-treble but in such price ?
The woofer selection is based on my experience, I built several OB in the past and yes an alpha 15 in a OB bug me a little because you look the magnitude is flat but you should look the phase.
In a closed box you have Bessel, Butteworth, Tchebychev alignment in the bass. Why don't take it into account in Open baffle ? S. Linkwitz (RIP) treats well the subject. In its active equalization he uses Bessel response, the best linear phase Qt=0.5.
In my world I try to keep QT < 0.8 in order to have a phase as linear as possible, no peak in the group delay. I think an Eminence beta 15 should be a better choice for phase response.
Second thing I like light cone with big woofer. I found the woofer has more definition, it could be a false assertion. This is the reason I hesitate to use a 15ob350, I'll test it in the future.
Third point yes an OB is sensitive to size for the sensitivity, dispersion, and crossover point when use passive components. I have a big constraint no baffle larger than 15" in my room, look like a WAF constraint. It resolves a lot of issue. Note for the crossover if it looks normal the mid-tweeter, for the bass you have a big compensation to apply to linearized the response of the woofer, like a big baffle step.
An other point is the drivers I use are made in China, a reason for the lower price if compare to Eminence woofer series ?
@mayhem13 Thank you ! Yes i like the result and my wife who have a discreet listening, not as attentive as mine, likes the sound, where you hear voices, you have the feeling the people are talking front of you.
Hi,
On my ex-Open Baffle speakes, I used Eminence Beta 15 (and a Visaton B200). Tried many passive crossovers, but was happy with none of them. The bass was alwayas "too light".
Until I went to biamping and EQ. I pretty much applied the crossover and an EQ from Nelson Pass "Slot loaded OB", 80 Hz low pass, 2nd order, and 160 Hz pass (2nd order). EQ bump aplied on the woofer and some some slight EQ on the fullrange. Only then I was really satisfied. (Until I got to move and dismantle the whole thing).
In summary: I don't think that Eminence Beta 15 can work well in passive OB.
I also heard Alphas, they subjectively give more bass, but again, I did not like them (Beta 15 with EQ sounds better).
But, with different drivers (High QTS woofer and a small, less efficient fullrange, like Manzanitas) things may work out differently.
Jerome, any chance that you can record a youtube video of your Open Baffles? That may give as a faint glimpse of how they sound.
On my ex-Open Baffle speakes, I used Eminence Beta 15 (and a Visaton B200). Tried many passive crossovers, but was happy with none of them. The bass was alwayas "too light".
Until I went to biamping and EQ. I pretty much applied the crossover and an EQ from Nelson Pass "Slot loaded OB", 80 Hz low pass, 2nd order, and 160 Hz pass (2nd order). EQ bump aplied on the woofer and some some slight EQ on the fullrange. Only then I was really satisfied. (Until I got to move and dismantle the whole thing).
In summary: I don't think that Eminence Beta 15 can work well in passive OB.
I also heard Alphas, they subjectively give more bass, but again, I did not like them (Beta 15 with EQ sounds better).
But, with different drivers (High QTS woofer and a small, less efficient fullrange, like Manzanitas) things may work out differently.
Jerome, any chance that you can record a youtube video of your Open Baffles? That may give as a faint glimpse of how they sound.
Attachments
Hi,
Thanks Vix for the exchange about the Eminence Beta 15
I notice you must have a very good amplifier when you drive passive open baffle. I drive them with a Primare SPA23 Class D High end AV amplifier. Plenty of power.
I know very well the SLS315 and SLS263 They work well, low distortion but I found the SLS315 miss a little articulation in the bass, a personal taste.
I have the material, but not sure how to do a good sound record.
Thanks Vix for the exchange about the Eminence Beta 15
I notice you must have a very good amplifier when you drive passive open baffle. I drive them with a Primare SPA23 Class D High end AV amplifier. Plenty of power.
I know very well the SLS315 and SLS263 They work well, low distortion but I found the SLS315 miss a little articulation in the bass, a personal taste.
I have the material, but not sure how to do a good sound record.