I am using a tube main amp connected to the OB. There is no active filter to this and will play full range to the OB. There can be some overlap of frequency from 40Hz to 100Hz and how much of a cancellation this will cause will be interesting to note.
Planning a TL sub
- Thread starter Hari Iyer
- Start date
elangoas
Well-Known Member
If you can design the subwoofer with high level inputs & outputs (speaker level inputs & outputs) and use the crossover on the sub, then you would have control over bass management..
Unfortunately my plate amp does not have a speaker input. But I think one can be made by putting a series resistance of high value around 47k to the RCA input and feed speaker levels. Again my guess.
Why is this so? Adding a BSC sucks the dynamics from the speaker and sound lifeless to my ears.
In a typical monopole speaker (the regular 2ways and 3ways) as the mid or woofer turns omni near baffle frequency it starts radiating into full space, below this frequency the woofer on-axis falls. An attempt is made to correct it by BSC compensation. Well, it does get the on axis frequency response right but at the expense of a screwed up frequency response off axis. The balance of on axis and off axis sound is often described by the term 'constant power response'. With regular speakers either you can get a flat frequency response on axis or off axis but never both.
A design which is not BSC compensated has a flat power response but falling mids.
An BSC compensated design has an non-flat power response but flat mids.
Choose your flaw, speaker design is all about making the right compromises.
OB/dipole by its very nature is a constant directivity design, its on axis and off axis is same. When equalisation is applied to OB/dipole its on axis AS WELL AS off axis follows, so, BSC is not needed but EQ is.
Many think that OB/Dipole sounds good due to being boxless or being free from resonance etc.
However, its the constant directivity and constant power response that makes the OB/dipole sound good.
I also feel that the reason people have a preference to vintage big drivers is not because they were any better but because they were often big in size and so could hold narrow directivity to a much lower frequency. A constant narrow directivity to a lower frequency gives it the same clarity and legibility as OB/dipole. There are many roads to Rome.
A design which is not BSC compensated has a flat power response but falling mids.
An BSC compensated design has an non-flat power response but flat mids.
Choose your flaw, speaker design is all about making the right compromises.
OB/dipole by its very nature is a constant directivity design, its on axis and off axis is same. When equalisation is applied to OB/dipole its on axis AS WELL AS off axis follows, so, BSC is not needed but EQ is.
Many think that OB/Dipole sounds good due to being boxless or being free from resonance etc.
However, its the constant directivity and constant power response that makes the OB/dipole sound good.
I also feel that the reason people have a preference to vintage big drivers is not because they were any better but because they were often big in size and so could hold narrow directivity to a much lower frequency. A constant narrow directivity to a lower frequency gives it the same clarity and legibility as OB/dipole. There are many roads to Rome.
Thanks diyaudio for the explanation.
As you can see from my OB speaker SPL response, constant directivity is maintained from 100 Hz upwards. Also this speaker is minimum phase type where the SPL phase is almost zero degree from 200 Hz till 10 KHz. Due to the constant directivity and dipole response, the presence of this speaker is unmatched. But due to this presence the low end suffers a bit as they get masked by the mids and highs. I am trying to address this problem by using a subwoofer below say 50 Hz. This will to some extend address the LF loss due to masking effect.
As you can see from my OB speaker SPL response, constant directivity is maintained from 100 Hz upwards. Also this speaker is minimum phase type where the SPL phase is almost zero degree from 200 Hz till 10 KHz. Due to the constant directivity and dipole response, the presence of this speaker is unmatched. But due to this presence the low end suffers a bit as they get masked by the mids and highs. I am trying to address this problem by using a subwoofer below say 50 Hz. This will to some extend address the LF loss due to masking effect.
Thanks yogibear for your opinion.
In continuation with my subwoofer plan, i discovered something new today. I added a 2200uF, 25V Keltron Electrolytic capacitor in series to the OB speaker + terminal. I know now that many of you will bomb me with what the heck is that and how dare you do that to the OB speaker etc. etc.
I did this for three reason - a. this prevents any DC component (if any) to enter the speaker and protect them
b. works as a high pass filter for my speaker above 19Hz. So this avoids any record rumbles to the speakers.
c. this prevents massive cone vibration below 30Hz and makes the upper bass (above 80Hz) very clean and also the mids and highs sound very uncompressed and pleasing now.
Since the subwoofer is going to supplement the bottom octave this configuration works well with my OB setup and is for the keeps. I have not yet completed my extensive listening with this and my expectations are quite good. I listened to one hour with this and am very much pleased with the outcome. So i have now added a 8uF and 0.47uF polyproplene capacitor in parallel to the Electrolytic capacitor. I have yet to complete the listening with this configuration.
In the meanwhile i got curious about why this sounds so good than my earlier OB connected directly to the amplifier and did some simulation using xsim with the frd & zma files generated from the TS parameters. I found that when the OB is directly connected, the xsim shows an underdamped response around 40Hz and the roll-off is quite steep. With the capacitor connected, the OB now gets critically damped and roll-off is very well controlled. Also the SPL phase changes happens at around 19Hz and keeps all the spurious LF out of the speakers.
Below are the simulated images,
OB Directly connected to amplifier terminals:
OB connected with 2200uF capacitor to amplifier terminals:
The ckt:
In continuation with my subwoofer plan, i discovered something new today. I added a 2200uF, 25V Keltron Electrolytic capacitor in series to the OB speaker + terminal. I know now that many of you will bomb me with what the heck is that and how dare you do that to the OB speaker etc. etc.
I did this for three reason - a. this prevents any DC component (if any) to enter the speaker and protect them
b. works as a high pass filter for my speaker above 19Hz. So this avoids any record rumbles to the speakers.
c. this prevents massive cone vibration below 30Hz and makes the upper bass (above 80Hz) very clean and also the mids and highs sound very uncompressed and pleasing now.
Since the subwoofer is going to supplement the bottom octave this configuration works well with my OB setup and is for the keeps. I have not yet completed my extensive listening with this and my expectations are quite good. I listened to one hour with this and am very much pleased with the outcome. So i have now added a 8uF and 0.47uF polyproplene capacitor in parallel to the Electrolytic capacitor. I have yet to complete the listening with this configuration.
In the meanwhile i got curious about why this sounds so good than my earlier OB connected directly to the amplifier and did some simulation using xsim with the frd & zma files generated from the TS parameters. I found that when the OB is directly connected, the xsim shows an underdamped response around 40Hz and the roll-off is quite steep. With the capacitor connected, the OB now gets critically damped and roll-off is very well controlled. Also the SPL phase changes happens at around 19Hz and keeps all the spurious LF out of the speakers.
Below are the simulated images,
OB Directly connected to amplifier terminals:
OB connected with 2200uF capacitor to amplifier terminals:
The ckt:
Last edited:
arunkvivek
Well-Known Member
The portal says 'Continuously variable active crossover filter control '. BTW, Rethm has long stopped using lowthers (I think they stopped it -3 years back). They have indegeniously developed speakers.
Thanks arunvivek for updating. Is active filter also for the full range speaker or only for the subwoofer?
arunkvivek
Well-Known Member
I don't know the nitigrities but here's what I see on 6moons: "Raw specs. The free-air efficiency of the widebander is 98dB/w/m. As loaded into a 2.4m long rear horn, this increases to 101dB. The response of this driver without the active sub is 50Hz to 18kHz. With sub the speaker extends down to 18Hz. The low-pass filter is continuously variable between 75Hz and 150Hz via an 18dB/octave 3rd-order passive network. The bass system's front horn is 1.1m long. Its thrice-paralleled isobaric** woofers sit in-line one behind the other firing from the end of their folded horn out into the down-facing reflectors. The built-in amp driving them is a 270-watt into 2Ω Mosfet affair. Overall dimensions of the Saadhana are 108 x 70 x 30cm HxDxW. Weight is 55kg/ea." This is for the older version of Saadhanas. I think they are powered by Hypex amps now.
Thanks for the details. I think the FR driver runs direct without any series capacitor and the sub uses an active filtered amplifier.
Yogibear, Again you are repeating the same for my subwoofer too. Since today i had the luxury of time, i did an extensive OB simulation with the 10" Dayton woofer and the results are encouraging. Check out the images. Subwoofer is mounted on a OB frame and i have added the room gain to both the subwoofer and the full range as that will be realistic.
The space required is not much and should fit in my cramped space, though i dont have much space behind the woofer. This can anyway be tried as damages are minimum cost wise.
Will settle down with a H- frame OB design. Will have some challenges with the baffle width due to cramped space near my main door. Have to discover if there is any other space in my room where they can go.
We tried an interesting experiment with an Altec604 driver in an Altec 620 (9.0 Cu.ft) box. Left the rear panel open, so the rear wave from the driver fires into the mouth of a 5' tall Altec 816 horn. The horn originally had two 416 drivers in a OB configuration. These drivers were removed so the openings were...OPEN.
Some of the back wave escapes via the two openings (on the 816 horn) but some gets amplified by the horn and returns via the small gap between the box and horn. It sounds crazy. Very balanced low end - the best way I can describe this.
Some of the back wave escapes via the two openings (on the 816 horn) but some gets amplified by the horn and returns via the small gap between the box and horn. It sounds crazy. Very balanced low end - the best way I can describe this.
In continuation with my OB saga, I felt that the OB FR had dipole behaviour only from 40 Hz to probably around 4 kHz. This is because the frequency above 4 KHz become directional and back radiation from the FR also reduces.
To extend the dipole pattern from 4 KHz to 20KHz, I am planning to experiment with my Abuja Piezoelectric Horn which I had purchased 2 years ago and was lying without much use. I shall cross this Piezoelectric around 10 to 12 KHz. So 5 KHz shall be just 6dB down which is ok. Shall also level match with my FR.
THIS will fire at the front wall behind the OB FR speaker and shall provide more diffused sound to the stage. I shall try and voice this by ear so that HF does not sound too compressed.
To extend the dipole pattern from 4 KHz to 20KHz, I am planning to experiment with my Abuja Piezoelectric Horn which I had purchased 2 years ago and was lying without much use. I shall cross this Piezoelectric around 10 to 12 KHz. So 5 KHz shall be just 6dB down which is ok. Shall also level match with my FR.
THIS will fire at the front wall behind the OB FR speaker and shall provide more diffused sound to the stage. I shall try and voice this by ear so that HF does not sound too compressed.
Yogibear, yesterday I did a quick crude version of putting the piezoelectric tweeters facing to the ceiling. I initially used 1 uF and finally settled for 0.22 uF. Even with this the gain was a bit high
So added a 47 ohm resistance parallel to the tweeters. Now they sound balanced and does not overpower the FR driver.
Actually I liked what I heard, there was a extra air in the music and they were not compressed. The midbass was quite smooth and the upper harmonics above 10 KHz had body. They were not rounded though but was not screechy either. I may have to listen more and probably rope in someone else to listen and voice this to my liking.
I think with the subwoofer, this should sound perfect.
So added a 47 ohm resistance parallel to the tweeters. Now they sound balanced and does not overpower the FR driver.
Actually I liked what I heard, there was a extra air in the music and they were not compressed. The midbass was quite smooth and the upper harmonics above 10 KHz had body. They were not rounded though but was not screechy either. I may have to listen more and probably rope in someone else to listen and voice this to my liking.
I think with the subwoofer, this should sound perfect.
Yesterday I was discussing with my elder brother about subwoofer placement and his direct to the point reply was - go the " Bose" way of placement. He went on to elaborate that psychology plays a huge role in audio gears and the moment someone even looks at a subwoofer they automatically feels more bass ( even if the subwoofer is turned off). Further he added that if you can find one such location, hide the subwoofer from sight and let the psychoacoustics play it's role.
What are FMs thought on this?.
What are FMs thought on this?.
elangoas
Well-Known Member
If you can place it according to your room dimensions, then there are more chances that you will hear more of the sub than the resonance..
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