Can you post the Madisound filter and LEAP results It would also be interesting to see the woofers low freq response and cabinet tuning target.
This is all I got from madisound - see attachments.
I think the polarity of the woofer is actually wrong on my xo.
There is no target port frequency stated anywhere in the drawings.
Theoretical port dimensions are W10.5" x H0.5" x D7" (rectangular).
If haven't had time this weekend to experiment with my speakers, but will do as soon as.
Infinia so you recommend building a new, bigger enclosure? Can I make it as big as I want? Is there something to watch out for? (e.g. frequency timing etc..)?
Doubling the volume would certainly be possible in terms of WAF (she doesn't mind floorstanding spks). I will certainly have a play with unibox 🙂
I think the polarity of the woofer is actually wrong on my xo.
There is no target port frequency stated anywhere in the drawings.
Theoretical port dimensions are W10.5" x H0.5" x D7" (rectangular).
If haven't had time this weekend to experiment with my speakers, but will do as soon as.
Infinia so you recommend building a new, bigger enclosure? Can I make it as big as I want? Is there something to watch out for? (e.g. frequency timing etc..)?
Doubling the volume would certainly be possible in terms of WAF (she doesn't mind floorstanding spks). I will certainly have a play with unibox 🙂
Hi
1) We determined the crossover polarity is correct from LTspice, as per your drawing, which was derived from the actual build, so I'm not sure why this is an issue at this time? I'm sure you can sort it out tho.
2&4) I just wanted to see what the design that you currently have is targeted for, so you can trouble shoot if there is a problem. Try to get a baseline before you make any decisions on which way to proceed.
3) Model the enclosure and driver with what you actually built, incl length corrections to vents ie slots using bottom surface. (DL the excel spreadsheet 'Unibox' if you have MS office.
You could try reversing one speakers polarity to check for bass cancellation (boxes face to face to test) . Any results from re-adjusting for room placement?
I have asked madisound what is the target port frequency.
Also attached is the box simulation using the actual dimensions.
As you can see, I didn't use any external components (I ignored the bsc).
Moreover the target port freq seems to be 36Hz (I tried different values until got the port length i.e. 7inch).
The frequency plot looks ok.
Is perhaps 36Hz too low, making the bass too boomy?
Finally I tried doubling the enclosure volume from 35lt to 70lt. I am not sure what the plots are telling me.
Also attached is the box simulation using the actual dimensions.
As you can see, I didn't use any external components (I ignored the bsc).
Moreover the target port freq seems to be 36Hz (I tried different values until got the port length i.e. 7inch).
The frequency plot looks ok.
Is perhaps 36Hz too low, making the bass too boomy?
Finally I tried doubling the enclosure volume from 35lt to 70lt. I am not sure what the plots are telling me.
Attachments
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Yea I guess that's the process since not knowing the tuning targets,
I have converted the slot to tubular dimensions with corrections ie Vent diameter 4.7cm and Lv of 20.6 cm from earlier in this thread. you got something else? keep playing with this program (It's a learning curve)
Note > see vented tab at bottom for more charts! 🙂
I'll see about trying it here as well.
OK this is what I found
This is not a ported design. It's more of a leaky box to tame any LF impedance peaks,,, so response is close to a closed box F-3dB ~ 70-75 Hz. Explains things here, unless I screwed up on port area calc/conv.
My recommendation is to convert to a ported design. Vbox=35l Fb=36Hz
Keep length of vent of 7" and open up the front area to be equal to a 7cm diameter. (10.5"x1 1/8" )Should have lots more bass and not booming type as some ported designs. You may loose some SPLs tho> max power for low distortion at rated Xmax is around 25Watts, so use power amp of 50-60 Watts for 3dB overhead.
This is not a ported design. It's more of a leaky box to tame any LF impedance peaks,,, so response is close to a closed box F-3dB ~ 70-75 Hz. Explains things here, unless I screwed up on port area calc/conv.
My recommendation is to convert to a ported design. Vbox=35l Fb=36Hz
Keep length of vent of 7" and open up the front area to be equal to a 7cm diameter. (10.5"x1 1/8" )Should have lots more bass and not booming type as some ported designs. You may loose some SPLs tho> max power for low distortion at rated Xmax is around 25Watts, so use power amp of 50-60 Watts for 3dB overhead.
Attachments
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Thank for the help infinia.
Interesting.
Madisound came back to me with the target tuning freq. which is 41Hz. ~ so we are not miles off.
Interestingly enough they are also recommending a ROUND vent with 3" dia and 8" long.
your suggestions infinia seem to match that
so seems like a new box with a round port will remedy the situation
should i put the port on the front or the back of the cabinet? from height of the bottom of the speaker?
finally should i stuff it heavily or just cover the walls? i guess i can experiment with that
cheers
Interesting.
Madisound came back to me with the target tuning freq. which is 41Hz. ~ so we are not miles off.
Interestingly enough they are also recommending a ROUND vent with 3" dia and 8" long.
your suggestions infinia seem to match that
so seems like a new box with a round port will remedy the situation
should i put the port on the front or the back of the cabinet? from height of the bottom of the speaker?
finally should i stuff it heavily or just cover the walls? i guess i can experiment with that
cheers
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Yup, same port tuning but mine is slightly lower tuning (don't like boomy bass) and I was staying with a bottom slot design. Your pick >If the front baffle is not removable then it's probably easist to modify to the tube on the rear, but I tend to go for front ports.
Change the crossover for the other problem, after retuning perhaps.
Strange Madisound didn't say they screwed up on the original tuning? Or some sort of explanation would be nice. FWIW Their crossover is designed for lowest parts count it seems.
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It's an budget kit so i didn't expect miracles but an extra cap and inductors wouldn't be the end of the world.
No I am rebuilding the speakers anyway as I am not happy with the finish anyway.
As I will be rebuilding them, is it worth making any other changes?
No I am rebuilding the speakers anyway as I am not happy with the finish anyway.
As I will be rebuilding them, is it worth making any other changes?
2k isn't a bad crossover point here, but usually you either use much smaller mid-bass drivers that can physically fit closer to the tweeter, or you use a tweeter with a lower crossover point, or both.
The ideal MTM would probably be a tweeter whose half wave length at low crossover point is equal to the distance between the center of the dome and the center of the woofers.
In this case, the half wavelength at 2k is 3.36", which would barely be reaching the woofer's flange.
The ideal MTM would probably be a tweeter whose half wave length at low crossover point is equal to the distance between the center of the dome and the center of the woofers.
In this case, the half wavelength at 2k is 3.36", which would barely be reaching the woofer's flange.
Rather than just starting in on a new design I would try various experiments and proceed in incremental stages like 1) various port tuning 2) crossover mods and even 3) paint/finishes on the old box. I'm sure you will hear a BIG differences with the changes we spoke about. After that If you really want more, then you might consider another woofer for a 2.5 way ie MMT rather than MTM. Other than that you could start from scratch again and not have a chance for excellent learning experience ie if you move in smaller deliberate steps.
Hi Tech
Actually I am not going to rebuild them as MTM but 2-way.
I know the title is for MTM design but I have decided not to go that way as it may not or emphasize the problem.
Cheers
Actually I am not going to rebuild them as MTM but 2-way.
I know the title is for MTM design but I have decided not to go that way as it may not or emphasize the problem.
Cheers
Hi all
I have done some experiments with the old boxes this weekend. For testing I listened to ministry of sound cd which contains a lot of low frequencies 😉 and I familiar with most of the tracks.
1) Moved the speakers so that they fire lengthwise at the room and also almost stuck their back very close to the wall. This did make an improvement on the bass. The low frequencies had definitely more body but I could still hear the annoying paper colouration. I kept the speakers in that position and then decided to play with polarity.
2) I added some terminal blocks on the woofer and tweeter to experiment with polarity. I reversed polarity on the woofer only, then tweeter only, then both tweeter and woofer.
Swapping polarity on the woofer was definitely the wrong thing to do. The bass body disappeared only with the very low frequencies coming out of the speaker and the vocals sounded strange, a bit off time. By changing tweeter polarity I didnt hear any substantial difference.
3) I put polarity back to original and did my final test. Removed some stuffing material from the speaker and I filled the rect. vent with stuffing and blocked the slot with a piece of wood. I used the input cap opening at the back as my new vent. Okay here comes the embarrassing bit.
I used a big nescafe box as my new vent! oh yeah! It's about 4,5" deep and has a dia of 3,5". I removed the bottom with a can opener... This gives a tunining freq of about 53Hz in unibox. There is a bit of a step as the input cap is a bit smaller but never mind. I secured it with some gopher tape trying to close any gaps and run the input cables through the "vent", hooked it up and prepared for an audition.
Not bad at all! The low freq have even more body now. That is very strange as i was expecting less bass. As for the paper colouration, it's improved. I wouldn't say it's completely gone but it's less notable now. The speaker has a different character now it sounds more airy- less harsh. Not bad at all for a nescafe box, eh.
What I want to try next is a smaller and longer vent and a new crossover.
I am planning to get some PVC from B&Q 2" and 3" to play with. As for the crossover I am not sure whether I should make a completely new one or salvage the old parts.
The problem is the old parts are well stuck on the board. I am afraid that I will damage them if I force them out. On the other hand a completely new xo would be expensive, and what if i don't like the new xo?
I have done some experiments with the old boxes this weekend. For testing I listened to ministry of sound cd which contains a lot of low frequencies 😉 and I familiar with most of the tracks.
1) Moved the speakers so that they fire lengthwise at the room and also almost stuck their back very close to the wall. This did make an improvement on the bass. The low frequencies had definitely more body but I could still hear the annoying paper colouration. I kept the speakers in that position and then decided to play with polarity.
2) I added some terminal blocks on the woofer and tweeter to experiment with polarity. I reversed polarity on the woofer only, then tweeter only, then both tweeter and woofer.
Swapping polarity on the woofer was definitely the wrong thing to do. The bass body disappeared only with the very low frequencies coming out of the speaker and the vocals sounded strange, a bit off time. By changing tweeter polarity I didnt hear any substantial difference.
3) I put polarity back to original and did my final test. Removed some stuffing material from the speaker and I filled the rect. vent with stuffing and blocked the slot with a piece of wood. I used the input cap opening at the back as my new vent. Okay here comes the embarrassing bit.
I used a big nescafe box as my new vent! oh yeah! It's about 4,5" deep and has a dia of 3,5". I removed the bottom with a can opener... This gives a tunining freq of about 53Hz in unibox. There is a bit of a step as the input cap is a bit smaller but never mind. I secured it with some gopher tape trying to close any gaps and run the input cables through the "vent", hooked it up and prepared for an audition.
Not bad at all! The low freq have even more body now. That is very strange as i was expecting less bass. As for the paper colouration, it's improved. I wouldn't say it's completely gone but it's less notable now. The speaker has a different character now it sounds more airy- less harsh. Not bad at all for a nescafe box, eh.
What I want to try next is a smaller and longer vent and a new crossover.
I am planning to get some PVC from B&Q 2" and 3" to play with. As for the crossover I am not sure whether I should make a completely new one or salvage the old parts.
The problem is the old parts are well stuck on the board. I am afraid that I will damage them if I force them out. On the other hand a completely new xo would be expensive, and what if i don't like the new xo?
Right
I have taken some xo components off the pcb. Resistors and caps seem ok but the inductor decided to stay there as I broke the plastic reel off. I have some 18awg enamel wire so perhaps i could wind my own inductors. Lalena.com has an inductor calculator
So... I have no xover at the moment. I think I will just go for that 2000Hz xo.
Cheers
I have taken some xo components off the pcb. Resistors and caps seem ok but the inductor decided to stay there as I broke the plastic reel off. I have some 18awg enamel wire so perhaps i could wind my own inductors. Lalena.com has an inductor calculator
So... I have no xover at the moment. I think I will just go for that 2000Hz xo.
Cheers
Update: I have decided to go ahead and rebuild my speakers with 2" round vent (3" sound too large) and 2nd order crossover at 2khz.
How do I add BSC?
How do I add BSC?
Per thread #42, the Madisound schematic shows that the 2 ohm resistor is not in parallel with the .45mh inductor to the woofer.
Am I correct in this observation?
bc
Am I correct in this observation?
bc
That is correct.
The madisound design is a series crossover.
However the crossover has those in parallel.
Maybe it was a simple madisound construction mistake which was causing all the trouble. Too late though i am already in the process of rebuilding them...
I will update when have made some progress
The madisound design is a series crossover.
However the crossover has those in parallel.
Maybe it was a simple madisound construction mistake which was causing all the trouble. Too late though i am already in the process of rebuilding them...
I will update when have made some progress
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