Yeah, though 'ballpark' is ~34400/pi/20 = ~547.5 Hz, but the actual diameter is ~1/2 octave bigger, so 0.707x and setting on the floor another 1/2 octave = a full octave lower, so 0.5x = ~273.75 Hz where room gain normally boosts it enough to not need any BSC, just maybe a bit of EQ to 'taste'. 😉
Hi Thanks for replies.
I did realise that stuffing the ports does not alter the baffle step, I was trying to find out how much baffle step had been allowed for in the crossover design so that I could decide if I needed to reduce it due to my close to wall siting of the speakers.
I am not good on crossovers my skill is in woodwork and as I am 73 next month I am keen to get on with building the speakers and dont want to spend months learning about crossover design.
As I asked in my last post does anyone know of someone who has a crossover design service to get me going with a good design to start with.
I did realise that stuffing the ports does not alter the baffle step, I was trying to find out how much baffle step had been allowed for in the crossover design so that I could decide if I needed to reduce it due to my close to wall siting of the speakers.
I am not good on crossovers my skill is in woodwork and as I am 73 next month I am keen to get on with building the speakers and dont want to spend months learning about crossover design.
As I asked in my last post does anyone know of someone who has a crossover design service to get me going with a good design to start with.
Do you have a powerful amplifier as the designer does state in one of the posts that they can get to three ohms impedance.
At the same time running them sealed maybe a sensible initial approach but you may have to re instate the ports if the bass in not boosted enough by the wall placement, or you like to listen at higher levels
At the same time running them sealed maybe a sensible initial approach but you may have to re instate the ports if the bass in not boosted enough by the wall placement, or you like to listen at higher levels
Forget about that. This works only if you have really deep pockets.
If you want to place the speakers against the back wall, this would have been your real request. IMHO every speaker designed to be placed in free space will sound awful against the back wall. So my suggestion is to search for a speaker explicitly designed to be placed against the wall, I know there are some commercial ones.
If you want to build a speaker for a bookshelf this should be a good design:
Bookshelf-3WC
Ralf
I have a Naim amplifier which should be ok for 3 ohms.
I do have a sealed sub thats why I want to use sealed main speakers.
I dont always use the sub that's why I want reasonable bass from the mains.
Thanks for the info.
Depending on your musical taste and the fact that you do not always use the Subs suggest that this should work to me. If you come unstuck and live not to far away I could maybe take some quick measurements to see what is going on. However, Low frequency measurements, splicing and matching levels is difficult to get correct. The measurement would definitely allow us to understand midrange and tweeter levels.
Depending on your musical taste and the fact that you do not always use the Subs suggest that this should work to me. If you come unstuck and live not to far away I could maybe take some quick measurements to see what is going on. However, Low frequency measurements, splicing and matching levels is difficult to get correct. The measurement would definitely allow us to understand midrange and tweeter levels.
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You can't change a bass reflex design to a sealed one by just sealing the ports.
The cabinet needs to be resized, probably smaller
and the drivers are maybe not optimal for sealed cabinets.
You can simulate this with Basta!, WinISD, Hornresp, ...
This project have a too horisontal freequency responce and will probably be tiring to listen to, the responce usually needs to be slightly tilted down for the speaker to sound balanced.
The small coil in series with the tweeter and the low impedance of 3 ohm are also warning signs, no experienced designer choses these methods and outcomes.
I would continue to search for another project if I was you.
Speakers when placed right against the back wall typically need wider baffles than usual. I would plan for about twice the actual driver diameter at the very least, to lower the baflle step to the point where the wall is providing all the BSC you actually need. You should factor in 1 to 1.5dB of BSC, no more, if you're doing a narrower baffle.
By using a wide baffle, you'll also get the drivers closer to the wall by reducing cabinet depth. Try tapering the sides (like a trapezoid), so as to reduce edge diffraction. The wall is going to be part of your speaker, so you may as well design around it.
By using a wide baffle, you'll also get the drivers closer to the wall by reducing cabinet depth. Try tapering the sides (like a trapezoid), so as to reduce edge diffraction. The wall is going to be part of your speaker, so you may as well design around it.
Hi raymondj thanks for your kind offer but I doubt it would need a visit all the same very kind of you.
In a sealed 40 L box with a qtc of 0.7 it gives an F3 of about 50 hz which I think will be low enough especially as I have the sub. As I said I know little about xovers so assume the baffle step is not too much for very near wall placement and I should also add that they will be well away from corners.
revisorn said that they would be tiring to listen to, I assume this is because they are MTMs and quite a flat level. I dont think this will be a problem either as in the article there is a resistor that can be increased to reduce treble and I should also point out that I am suffering from HF hearing loss.
If I had the crossover redesigned I would ask for a small baffle step and a flat response.
If anyone else has any further ideas or suggestions I would be pleased to hear from them.
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It is an oversimplification to reduce wall placement to some level of compensation. Comb filtering and the like is going to be the more significant factor, making baffle design more important. This may also contribute to listening fatigue.
I did meddle with two of the drivers in a wonderful software tool called VituixCad. which suggest your own numbers as being correct with some bass extension below 100 Hz from the two drivers in sealed configuration of 42 Litres using the data for your driver in Vituix. The drivers will be hitting max excursion at around 10 watts of Low frequency below 50Hz and the prediction is near to 100dBs level in the midrange, the crossover network will probably add a few more dBs of attenuation so not to bad and quite loud.
Resistor tweaking should get you a very listenable response. How is the wood cutting going, have you had trouble sourcing drivers after Brexit, or do you have them waiting on a shelf?
Resistor tweaking should get you a very listenable response. How is the wood cutting going, have you had trouble sourcing drivers after Brexit, or do you have them waiting on a shelf?
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Thanks again for replies.
Not purchased anything yet so not sure how easy getting parts will be.
Still a bit concerned that the crossover has too much baffle step compensation but not sure how to reduce it and by how much.
Not purchased anything yet so not sure how easy getting parts will be.
Still a bit concerned that the crossover has too much baffle step compensation but not sure how to reduce it and by how much.
Taking your concern, it would seem sensible to build in such a way as to allow for a removable crossover assembly by having a removable panel as part of the design.
It is far easier to tweak a crossover when it is external mounted.
Components of interest that should allow tuning is the first bass inductor at 1mH, which you can unwind if you have too much baffle step. Remove 6" or a foot of wire at a time, scrape the new end free of the enamel enamel tin and re connect.
If you have too much mid the bottom resistor on the parallel filter of the bass units can be tweaked for flattening the response.
For tweeter level matching the first resistor 2.7 ohms can be increased to lower level somewhere between 2.7 and 6.8 ohms should get you there, if there isn't enough treble go lower than 2.7 ohms.
Once happy record you new values to let us know how the project ended up, and refit the crossover internally and screw the panel back on, listen and if happy, a job well done.
I had stuff on order before Brexit and not all of it has arrived from Europe yet. Both sides of the channel have horror stories on delays and re tape, so you may have to factor in more time and costs for delivery.
It is far easier to tweak a crossover when it is external mounted.
Components of interest that should allow tuning is the first bass inductor at 1mH, which you can unwind if you have too much baffle step. Remove 6" or a foot of wire at a time, scrape the new end free of the enamel enamel tin and re connect.
If you have too much mid the bottom resistor on the parallel filter of the bass units can be tweaked for flattening the response.
For tweeter level matching the first resistor 2.7 ohms can be increased to lower level somewhere between 2.7 and 6.8 ohms should get you there, if there isn't enough treble go lower than 2.7 ohms.
Once happy record you new values to let us know how the project ended up, and refit the crossover internally and screw the panel back on, listen and if happy, a job well done.
I had stuff on order before Brexit and not all of it has arrived from Europe yet. Both sides of the channel have horror stories on delays and re tape, so you may have to factor in more time and costs for delivery.
Hi raymondj
Thanks for your advice, I take your point and yes I will make the crossover easily accessible.
Thanks for the guidance on what to do with various problems.
Think I will go ahead lets hope I do not have too much trouble getting parts etc.
Just one final hurdle to go now which is the wife/boss final approval.
Thanks for your advice, I take your point and yes I will make the crossover easily accessible.
Thanks for the guidance on what to do with various problems.
Think I will go ahead lets hope I do not have too much trouble getting parts etc.
Just one final hurdle to go now which is the wife/boss final approval.
Hi raymondj thanks agian but just realised that there is no 1mH inductor on the bass circuit.
There are 3 inductors L2 - 0.82mH DCR 0.169ohms, L3 0.1mH - DCR 0.1ohms and L4 0.82mH - DCR 1.0 ohms.
So which one should be unwound to reduce baffle step, also does it matter that the DCR would also be reduced.
There are 3 inductors L2 - 0.82mH DCR 0.169ohms, L3 0.1mH - DCR 0.1ohms and L4 0.82mH - DCR 1.0 ohms.
So which one should be unwound to reduce baffle step, also does it matter that the DCR would also be reduced.
You are right.
There is no 1mH, i had been playing with the circuit designer in VituixCcad and left it at 1mH
As you point out 0.82mH is the published value.
To answer your question, Yes, it will make a miniscule difference, so small it will probably not be visible on the graphs.
There is no 1mH, i had been playing with the circuit designer in VituixCcad and left it at 1mH
As you point out 0.82mH is the published value.
To answer your question, Yes, it will make a miniscule difference, so small it will probably not be visible on the graphs.