I kept measurement location fixed while varying distance from wall. I suppose one should set measurement distance similar to listening position typically 2.5 m? When placed closer to wall there is definitely some dipping in the bass. The output from a simple upside down "box" is rather interesting as I am surprised that it works at all. So do you have suggestion on where to put measurement?
For sure, what normally matters most is its response at the Lp and generally speaking there should be no major dip in the bass when up against a wall except due to floor bounce, which will shift up in frequency with decreasing distance to the Lp and since our hearing acuity is falling with decreasing frequency, it's generally better to shift it down as far as practical and of course little/no BSC is required when up against a wall.
Upside down box?
GM
I will do some calca at listening position. Upside down box with opening at floor with legs to let sound out. That is basically the design of one is the variants of the Rondo. The variant with a slot out the back is very different because I do not see where the long distance walls are for resonance as it is more like an open baffle.
Rondo inspired speakers - simulations
I ran some more calculations with the listening position at 3 m away with varying back distances from a wall: 48 in, 60 in, 72 in. The 72 in looks best but there are some unpleasant dips in response. This is for 4 watts input power (5.65 volts). The last plot is for the 72 in from back wall but with a 2 m listening position.
I ran some more calculations with the listening position at 3 m away with varying back distances from a wall: 48 in, 60 in, 72 in. The 72 in looks best but there are some unpleasant dips in response. This is for 4 watts input power (5.65 volts). The last plot is for the 72 in from back wall but with a 2 m listening position.
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All these designs seem to have some sort of porting on the back baffle. Locations vary, so I built the open back one to try different sizes and locations. I liked the sound with the open back better with the modern drivers, but the greencones like the ports.
Having listened to my pairs for a while, I'm guessing their graphs would look ugly, but the sound is more than pleasant.
Having listened to my pairs for a while, I'm guessing their graphs would look ugly, but the sound is more than pleasant.
Gary,
I think you are right about what the graphs would look like - I mean a simple box with a slot on the back, or a box with an open bottom on raised legs to let sound leak out. I am surprised that the predicted responses that I have above look as good as they do - and that was with some optimizing the height vs volume, leg/gap height, distance from wall, driver placement etc. The important thing is that if the produce a pleasant 'musical' quality sound. The graphs will not be able to show the inherent sound radiating from the thin walls like a double bass or a cello. That may be half the magic there. Similarly, that is one reason I like the sound from some of my thin foam core speakers. The speakers are in this case, probably coloring the sound, but it is pleasant.
I just realized that your callsign is probably short for Elmer J Fudd?
I think you are right about what the graphs would look like - I mean a simple box with a slot on the back, or a box with an open bottom on raised legs to let sound leak out. I am surprised that the predicted responses that I have above look as good as they do - and that was with some optimizing the height vs volume, leg/gap height, distance from wall, driver placement etc. The important thing is that if the produce a pleasant 'musical' quality sound. The graphs will not be able to show the inherent sound radiating from the thin walls like a double bass or a cello. That may be half the magic there. Similarly, that is one reason I like the sound from some of my thin foam core speakers. The speakers are in this case, probably coloring the sound, but it is pleasant.
I just realized that your callsign is probably short for Elmer J Fudd?
i liked them. they were interesting compared to a br. they were very dynamic. good price/performance ratio. there were other Rondo-type speakers without tweeter, I did not liked them (attached picture).
however, I don't like full range speakers, they are not my cup of tea. I auditioned the 4Pi speakers 1-2 weeks earlier (2226h/de250).
however, I don't like full range speakers, they are not my cup of tea. I auditioned the 4Pi speakers 1-2 weeks earlier (2226h/de250).
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I was thinking of something along with what was mention here with the wharfadale super 8 rs/dd. Could dope the surround first before implementing in such cabinet like the "Breeze" which mention earlier by xrk971. They look very nice indeed!
Could someone here suggest an ideal dimensions for the super 8 rs/dd? TS parameters can be found on "troelsgravesen" website.
Could someone here suggest an ideal dimensions for the super 8 rs/dd? TS parameters can be found on "troelsgravesen" website.
Rondo with Super 8
Sagamotto,
I am very pleased with how well the Super 8's perform in an open bottom Rondo style enclosure. Very simple yet the response appears to be very flat in the bass end with extension down to 50 Hz. There are resonance peaks and dips but that will make the speaker have "character" very much like a cellor or double-bass body. It will impart its own coloration to the music but that may not be bad depending on the music you play. Probably chamber music and simple vocals will sound very nice.
Here is the design I came up with in AkAbak: 12 in wide baffle x 16 in (equivalent depth) - make the nice tear drop shape cross section but preserve the cross sectional area of about 192 square inches (CSA) x 60 in tall, at the bottom provide a window brace (ring) with an equivalent CSA that is 80% of the main CSA. The driver is mounted 24 in down from the top, the speaker stands on 4 in legs to provide a gap of 4 in for the sound to radiate out. Otherwise, the box is sealed - open only at the bottom.
Here is the freq response, the impulse response, and the driver cone displacement for a 4 watt power input with listening position at 3 m away, and speaker situated well away from a wall (72 in). This design does not like to be near a wall - you will get cancellation and dips.
I think it may turn out to be a nice speaker if you are willing to give it a try.
regards,
X
Sagamotto,
I am very pleased with how well the Super 8's perform in an open bottom Rondo style enclosure. Very simple yet the response appears to be very flat in the bass end with extension down to 50 Hz. There are resonance peaks and dips but that will make the speaker have "character" very much like a cellor or double-bass body. It will impart its own coloration to the music but that may not be bad depending on the music you play. Probably chamber music and simple vocals will sound very nice.
Here is the design I came up with in AkAbak: 12 in wide baffle x 16 in (equivalent depth) - make the nice tear drop shape cross section but preserve the cross sectional area of about 192 square inches (CSA) x 60 in tall, at the bottom provide a window brace (ring) with an equivalent CSA that is 80% of the main CSA. The driver is mounted 24 in down from the top, the speaker stands on 4 in legs to provide a gap of 4 in for the sound to radiate out. Otherwise, the box is sealed - open only at the bottom.
Here is the freq response, the impulse response, and the driver cone displacement for a 4 watt power input with listening position at 3 m away, and speaker situated well away from a wall (72 in). This design does not like to be near a wall - you will get cancellation and dips.
I think it may turn out to be a nice speaker if you are willing to give it a try.
regards,
X
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Hi XRK971
Thank you for taking the time to simulate the driver for me.
Can i reduce the height and increase the width? I can only tolerate a maximum of 4ft in height including the 4" feet, but not too deep. I prefer it to be abit shallow but wide (20" max)
Instead of the tear drop shape design, would something like a half circle be okay?
Can the side/rear be made with multi layer of foam core sheet?
You have mentioned that the speakers can't be place near any wall. That would not be possible in my case cause she said I can only put them in the two corner between our sofa (approximately 12 ft apart) lol
Thanks again xrk971, I really enjoyed reading your foam core idea...
Thank you for taking the time to simulate the driver for me.
Can i reduce the height and increase the width? I can only tolerate a maximum of 4ft in height including the 4" feet, but not too deep. I prefer it to be abit shallow but wide (20" max)
Instead of the tear drop shape design, would something like a half circle be okay?
Can the side/rear be made with multi layer of foam core sheet?
You have mentioned that the speakers can't be place near any wall. That would not be possible in my case cause she said I can only put them in the two corner between our sofa (approximately 12 ft apart) lol
Thanks again xrk971, I really enjoyed reading your foam core idea...
Sagamotto,
You are welcome. I just ran some more sims with a 48 in height per your request. It can work if you constrict the opening at the bottom (almost like making it into a MLTL). I also made the baffle wide and the speaker shallow.
The design is as follows: 24 in wide baffle, 10 in equivalent depth for 244 square inch CSA, driver mounted 16 in from top, 4 in tall legs for gap at bottom, the window brace at the bottom will now be only 60% of the CSA area of the top, plus it has a wall that extends up into the speaker cabinet like a vent tube that is 8 in long. Still, it doesn't like to be near a wall. I am showing you the response far from wall (72 in) and near wall (16 in). Pretty ugly near wall - very boomy bass peak at 50 Hz. You can of course, make this out of curved foam core in the back as semicircle and the foam core will let you bend and curve easily. Use soundboard wood like thin maple or cedar on the front like a musical instrument. The plots below are freq response far from wall, impulse, and cone displacement for 4 watts, 3 m listening position, and 72 in distance from wall. Last plot is freq response placed 16 in from wall.
Seeing your situation and requirements, may I suggest you just go with a traditional MLTL design with a front firing port? It may work out much better for you. You can still have the cool semicircle design with flat front and curved back. I can come up with a design for a true MLTL if you like.
You are welcome. I just ran some more sims with a 48 in height per your request. It can work if you constrict the opening at the bottom (almost like making it into a MLTL). I also made the baffle wide and the speaker shallow.
The design is as follows: 24 in wide baffle, 10 in equivalent depth for 244 square inch CSA, driver mounted 16 in from top, 4 in tall legs for gap at bottom, the window brace at the bottom will now be only 60% of the CSA area of the top, plus it has a wall that extends up into the speaker cabinet like a vent tube that is 8 in long. Still, it doesn't like to be near a wall. I am showing you the response far from wall (72 in) and near wall (16 in). Pretty ugly near wall - very boomy bass peak at 50 Hz. You can of course, make this out of curved foam core in the back as semicircle and the foam core will let you bend and curve easily. Use soundboard wood like thin maple or cedar on the front like a musical instrument. The plots below are freq response far from wall, impulse, and cone displacement for 4 watts, 3 m listening position, and 72 in distance from wall. Last plot is freq response placed 16 in from wall.
Seeing your situation and requirements, may I suggest you just go with a traditional MLTL design with a front firing port? It may work out much better for you. You can still have the cool semicircle design with flat front and curved back. I can come up with a design for a true MLTL if you like.
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Thanks again xrk971
Judging from FR, some EQing could further smooth out the peak abit. But that peak near 50hz at near wall placement isn't very impressive even though it can be tone down with a simple EQ network, again that's adding more parts in the signal which isn't my first choice. Better I go with a true mltl design ? Could you help please?
Would it be possible to design a vertical slot port instead of horizontal?
Judging from FR, some EQing could further smooth out the peak abit. But that peak near 50hz at near wall placement isn't very impressive even though it can be tone down with a simple EQ network, again that's adding more parts in the signal which isn't my first choice. Better I go with a true mltl design ? Could you help please?
Would it be possible to design a vertical slot port instead of horizontal?
Sagamotto,
I think GM offered you a very nice design for a MLTL in the Super 8 thread. Although you said it was too tall for your tastes at 56 in. I am not able to come up with a nice design as a MLTL that is 48 in or shorter and able to sit close to a wall. Here is what I have so far based on your request for wider baffle... 16 in wide x 12 in deep x 48 in high, driver at 17 in from top, port is 5 in dia x 2 in long located 10 in from bottom front firing.
Simulations are for 4 watts power, 3 m listening position, and speaker placed 72 in from back wall vs 24 in from back wall. Not very pretty... It will look better with sufficient stuffing/damping in upper 2/3rds of the TL.
I think GM offered you a very nice design for a MLTL in the Super 8 thread. Although you said it was too tall for your tastes at 56 in. I am not able to come up with a nice design as a MLTL that is 48 in or shorter and able to sit close to a wall. Here is what I have so far based on your request for wider baffle... 16 in wide x 12 in deep x 48 in high, driver at 17 in from top, port is 5 in dia x 2 in long located 10 in from bottom front firing.
Simulations are for 4 watts power, 3 m listening position, and speaker placed 72 in from back wall vs 24 in from back wall. Not very pretty... It will look better with sufficient stuffing/damping in upper 2/3rds of the TL.
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