Sorry Scott I don't have that data. I simmed in win isd using manufactures parameters. Sealed in these boxes I had (approx 17litres gross) the Q is a little low at just under 0.6.
Shelves down the HF in theory, but it depends on how you apply it. For e.g., you can't take a given low pass & then shunt the primary inductor with a resistor while also maintaining the same transfer function -the shelving filter needs to be designed in.
Oh, narry a problem. I think most tend to do the same, and the results typically still end up quite good. T/S spec. tends to vary with voltage drive level, and SB units often (not always, depends on the unit) show a bit more of that than some, which is why I was interested if you had any data. I have DATS v3 here for pair-matching, general testing, and very good it is too, but I tend to be a bit careful accepting its Q values with SB units (I stress the caveat there).
I got the new XOs in yesterday. Wow what a change
...for the better. No measurements I'm afraid. Thay 5k rise i had I guess is gone as the bass is much more prominent. Using the 4r7 pad on the tweeter at the moment. I may try the 3r3 for a little brighter presentation but I'll give them some more hours first.
My winisd sim gave me a Q of somewhere around 0.6..maybe just under. Reading Michael Chua's article on speaker Q, he says that 0.5 is the best, but that not all drivers can manage that...if I understand correctly.
What parameters of a driver will not enable a Q of 0.5?
My Q seems to arise from a slightly oversized box. If I wanted to raise the Q to maybe have a little more LF should I remove some stuffing. ? My limited knowledge recalls that adding stuffing to a sealed speaker mimics added volume?
I need to add some underlay/foam to the walls but at present I am very happy with them.
I also have some 0.01uf PP caps. I understand that these sorts of caps are used as bypasses on larger vakue caps. Should I try them on all the caps in my XO or just particular ones? I realsise this may give subjective results but I wondered if there was a rule of thumb where to add these bypasses.
Thanks for reading
...for the better. No measurements I'm afraid. Thay 5k rise i had I guess is gone as the bass is much more prominent. Using the 4r7 pad on the tweeter at the moment. I may try the 3r3 for a little brighter presentation but I'll give them some more hours first.
My winisd sim gave me a Q of somewhere around 0.6..maybe just under. Reading Michael Chua's article on speaker Q, he says that 0.5 is the best, but that not all drivers can manage that...if I understand correctly.
What parameters of a driver will not enable a Q of 0.5?
My Q seems to arise from a slightly oversized box. If I wanted to raise the Q to maybe have a little more LF should I remove some stuffing. ? My limited knowledge recalls that adding stuffing to a sealed speaker mimics added volume?
I need to add some underlay/foam to the walls but at present I am very happy with them.
I also have some 0.01uf PP caps. I understand that these sorts of caps are used as bypasses on larger vakue caps. Should I try them on all the caps in my XO or just particular ones? I realsise this may give subjective results but I wondered if there was a rule of thumb where to add these bypasses.
Thanks for reading
Didn't realise you had a thread running about these!
Thanks for the kind words earlier in the thread. It's always great to meet fellow DIYers, and I'm glad you've found the work to be useful.
The crossover I put together should do pretty well. I tried to balance parts count vs suppressing the breakup range on the woofer and found 2nd order seemed to do okay. A notch across the driver would attenuate things further, though, if there's still some harshness.
As you've noted, the resistor feeding the HF circuit can be changed to alter the HF balance. IIRC it maintains phase tracking through a good range of values, so feel free to play. 4R7 should be flat (or close), but feel free to get it how you like it.
I'm off out now, but will respond more fully later.
All the best,
Chris
PS - Scott, no T/S I'm afraid. The LF response is pretty much as expected, though - too rolled off for outdoor use, but indoors with cabin gain will probably do quite well.
Thanks for the kind words earlier in the thread. It's always great to meet fellow DIYers, and I'm glad you've found the work to be useful.
The crossover I put together should do pretty well. I tried to balance parts count vs suppressing the breakup range on the woofer and found 2nd order seemed to do okay. A notch across the driver would attenuate things further, though, if there's still some harshness.
As you've noted, the resistor feeding the HF circuit can be changed to alter the HF balance. IIRC it maintains phase tracking through a good range of values, so feel free to play. 4R7 should be flat (or close), but feel free to get it how you like it.
I'm off out now, but will respond more fully later.
All the best,
Chris
PS - Scott, no T/S I'm afraid. The LF response is pretty much as expected, though - too rolled off for outdoor use, but indoors with cabin gain will probably do quite well.
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Here come the extra thoughts:
- BSC is likely not needed. Near-ish wall placement will probably reinforce <200Hz just fine, plus cabin gain etc to prop up the low end. An inductor and resistor in parallel at the speaker input would shelve the mid-high range down if you wanted that sort of sound. NB - the inductor size determines the low shelf frequency, and the resistor the attenuation.
Changing the tweeter resistor has the same effect, but only above the crossover frequency.
- Stuffing makes small differences to the LF shape in sealed boxes. A few percent change in cabinet volume. By contrast, the room makes a huge difference to the LF response. IMO, the place where stuffing is important is the >200Hz range, where standing waves ought to be attenuated.
- With regards to Q-factors. Q increases with a smaller box, and decreases with a larger box. Qtc (total Q of the cabinet) can only ever be above Qts (total Q of the speaker). Infinite baffle situations (where the cabinet is very very large, 10x Vas) have Qtc = Qts, since the cabinet is so large as to have no effect on the speaker's resonance or damping.
Chris
PS - For home HiFi, I've been favouring sealed boxes lately. They can dig nice and low with a bit of help from the room (my room in particular is very helpful, and I actually have to attenuate the LF), but maximum SPL does suffer (compared to ported etc) since the cabinet really is doing nothing to reinforce the LF output.
- BSC is likely not needed. Near-ish wall placement will probably reinforce <200Hz just fine, plus cabin gain etc to prop up the low end. An inductor and resistor in parallel at the speaker input would shelve the mid-high range down if you wanted that sort of sound. NB - the inductor size determines the low shelf frequency, and the resistor the attenuation.
Changing the tweeter resistor has the same effect, but only above the crossover frequency.
- Stuffing makes small differences to the LF shape in sealed boxes. A few percent change in cabinet volume. By contrast, the room makes a huge difference to the LF response. IMO, the place where stuffing is important is the >200Hz range, where standing waves ought to be attenuated.
- With regards to Q-factors. Q increases with a smaller box, and decreases with a larger box. Qtc (total Q of the cabinet) can only ever be above Qts (total Q of the speaker). Infinite baffle situations (where the cabinet is very very large, 10x Vas) have Qtc = Qts, since the cabinet is so large as to have no effect on the speaker's resonance or damping.
Chris
PS - For home HiFi, I've been favouring sealed boxes lately. They can dig nice and low with a bit of help from the room (my room in particular is very helpful, and I actually have to attenuate the LF), but maximum SPL does suffer (compared to ported etc) since the cabinet really is doing nothing to reinforce the LF output.
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Thanks for the input Chris...interesting stuff.
No i don't think they need any BSC.
Listened to them quite a while last night. We would normally have the AVR on and that means the subwoofer is in action but last night was just stereo fronts.
Sky Q> optical > modded Cambridge Audio dacmagic> Salas DCG3 > TPA3255 power amp
It was the first time I thought I can listen to this and not really miss the SW.
I did resim the box volume whilst looking at the effects of the Q and LF response and actually where they are now..atleast simulated in winisd is about as good as I can expect....giving the lowest f10 at 38Hz. Q is 0.59 and Fsc is 62Hz on the sim.
The placement in room is really not ideal but this is nothing I can resolve unfortunately. My biggest issue is the imbalance in that the L channel is about 2 feet closer than the R channel. I didnt think it was so much but having measured i was quite surprised....so obviously the L channel seems at a higher level. I use the balance control in the AVR but I don't have thay function with the 'hifi' setup.
As you can see the speakers are really pushed into corners. Not ideal but it is what I have to work with
No i don't think they need any BSC.
Listened to them quite a while last night. We would normally have the AVR on and that means the subwoofer is in action but last night was just stereo fronts.
Sky Q> optical > modded Cambridge Audio dacmagic> Salas DCG3 > TPA3255 power amp
It was the first time I thought I can listen to this and not really miss the SW.
I did resim the box volume whilst looking at the effects of the Q and LF response and actually where they are now..atleast simulated in winisd is about as good as I can expect....giving the lowest f10 at 38Hz. Q is 0.59 and Fsc is 62Hz on the sim.
The placement in room is really not ideal but this is nothing I can resolve unfortunately. My biggest issue is the imbalance in that the L channel is about 2 feet closer than the R channel. I didnt think it was so much but having measured i was quite surprised....so obviously the L channel seems at a higher level. I use the balance control in the AVR but I don't have thay function with the 'hifi' setup.
As you can see the speakers are really pushed into corners. Not ideal but it is what I have to work with
Attachments
A little update on my speakers....objective opinions.
So having spent a couple more months with the soeakers I am getting a better picture of their strengths and weaknesses.
The biggest issue I seem to have pinpointed is their apparent lack of air/ spaciousness/ life/ drive.....especially at lower levels. They can be quite unimpressive and underwhelming. If they are cranked up then they sound great. Maybe still lacking a bit of depth to the sound stage.
My best example is this situatuon; music playing in sync in 2 rooms at casual levels via 2 Google chromecast audios. One in the kitchen, simple system with a Chinese es9038 dac, tda8932 amp into cheap Cambridge Audio retail bookshelves.....speakers sat up high on top of the kitchen wall units. Sounds really good for what it is with lovely 'air.' Music is in the room...not coming from the speakers.
Walk through to the living room playing the same synced music through main hifi system and it is a stark difference and not for the better. Music is recessed and 'in the speakers' . The B&W small BR bookshelves i had before as my reference gave a better impression on first acquaintance.
I tried a couple changes. Reversed tweeter polarity....didnt make a massive difference to my ears.
I also added a small value bypass cap in the HF circuit. I can remember where now....I read something on here about it and raising the HF from 10k a little. Hasn't helped a great deal.
I was considering trying and 'ambience ' tweeter firing back and up on the rear of the speaker. Filtered in fairly high. Or even thought about a 5" mid on the back.
Does anyone have any input on what I could look to? Maybe it is the speaker placement in the room, in which case I am out of luck! The small B&Wilkins lived in the same place but quite a lot smaller box.....and rear ported. Maybe the rear reflections from the port helped, making me think a rear driver might help. Or was it the added breathing room from the B&W small box, they did image/ stage well.
So having spent a couple more months with the soeakers I am getting a better picture of their strengths and weaknesses.
The biggest issue I seem to have pinpointed is their apparent lack of air/ spaciousness/ life/ drive.....especially at lower levels. They can be quite unimpressive and underwhelming. If they are cranked up then they sound great. Maybe still lacking a bit of depth to the sound stage.
My best example is this situatuon; music playing in sync in 2 rooms at casual levels via 2 Google chromecast audios. One in the kitchen, simple system with a Chinese es9038 dac, tda8932 amp into cheap Cambridge Audio retail bookshelves.....speakers sat up high on top of the kitchen wall units. Sounds really good for what it is with lovely 'air.' Music is in the room...not coming from the speakers.
Walk through to the living room playing the same synced music through main hifi system and it is a stark difference and not for the better. Music is recessed and 'in the speakers' . The B&W small BR bookshelves i had before as my reference gave a better impression on first acquaintance.
I tried a couple changes. Reversed tweeter polarity....didnt make a massive difference to my ears.
I also added a small value bypass cap in the HF circuit. I can remember where now....I read something on here about it and raising the HF from 10k a little. Hasn't helped a great deal.
I was considering trying and 'ambience ' tweeter firing back and up on the rear of the speaker. Filtered in fairly high. Or even thought about a 5" mid on the back.
Does anyone have any input on what I could look to? Maybe it is the speaker placement in the room, in which case I am out of luck! The small B&Wilkins lived in the same place but quite a lot smaller box.....and rear ported. Maybe the rear reflections from the port helped, making me think a rear driver might help. Or was it the added breathing room from the B&W small box, they did image/ stage well.
Having the sound "right" at higher levels suggests that you might like a little extra harmonic distortion, which leads to a brighter overall tonal balance. Altering the HF resistor (or bypassing it with a 1-2uF cap) will change the tonal balance directly, and would be the first thing I'd try. You could even short the resistor entirely, but I'd expect that to be overly bright.
The "stuck to the speakers" bit might be to do with baffle edge diffraction. In that case, I'd recommend adding more felt to the baffle if you can fit it in.
For what it's worth, there's also some psychoacoustic stuff that kicks in: at lower levels, everything sounds "dead" and "lifeless". Adding another 6-10dB often brings things to life in a very dramatic way.
Chris
The "stuck to the speakers" bit might be to do with baffle edge diffraction. In that case, I'd recommend adding more felt to the baffle if you can fit it in.
For what it's worth, there's also some psychoacoustic stuff that kicks in: at lower levels, everything sounds "dead" and "lifeless". Adding another 6-10dB often brings things to life in a very dramatic way.
Chris
Thanks Chris....hope you are well.
I shall double check but I think the modification I made was adding the bypass across the tweeter R. I think I added 1uf but again shall check. Maybe I can play with this value.
On the baffle...I could always lose the aluminium trim and see if that changes things....even add a roundover on the edges and forego the grilles/WAF. And this has just spiked a curiosity in my brian.....grilles.....I haven't tried them for any length of time with them removed.
Don't get me wrong the speakers are great and I enjoy them a lot.
Appreciate your comments and I shall do some more trials.
I shall double check but I think the modification I made was adding the bypass across the tweeter R. I think I added 1uf but again shall check. Maybe I can play with this value.
On the baffle...I could always lose the aluminium trim and see if that changes things....even add a roundover on the edges and forego the grilles/WAF. And this has just spiked a curiosity in my brian.....grilles.....I haven't tried them for any length of time with them removed.
Don't get me wrong the speakers are great and I enjoy them a lot.
Appreciate your comments and I shall do some more trials.
The 1uF cap will allow more of the very top end "air", while a larger value will extend that lower into the treble range.
The resistor will raise/lower everything above the crossover point, around 2kHz IIRC.
So you've got some options about the frequency range which you could bring up in level.
In hindsight, it would've been worthwhile to measure the response curves with the grilles in place. Don't forgo WAF just yet, but if the grilles are a typical 1/4" MDF frame with fabric, you've got space to add more felt without impinging on the outer look.
It could well be that the grille fabric is killing off some of the high treble, so playing with the bypass cap is where I'd start first.
Chris
PS - Glad you're still enjoying them. It's nice to hear when someone enjoys the work you've done.
The resistor will raise/lower everything above the crossover point, around 2kHz IIRC.
So you've got some options about the frequency range which you could bring up in level.
In hindsight, it would've been worthwhile to measure the response curves with the grilles in place. Don't forgo WAF just yet, but if the grilles are a typical 1/4" MDF frame with fabric, you've got space to add more felt without impinging on the outer look.
It could well be that the grille fabric is killing off some of the high treble, so playing with the bypass cap is where I'd start first.
Chris
PS - Glad you're still enjoying them. It's nice to hear when someone enjoys the work you've done.
Definitely a 1uf i added into the HF circuit. XSIM shows it just adding the slightest lift above 10k. Maybe I try a slightly larger value.
I tried adding an 'ambience' tweeter into XSIM. Just picking a cheap Dayton Audio job as the frd and zma are readily available....just out of interest. I added the 60 off axis files although they would be more like 180. It does lower the overall system impedance to 3 ohms ish above 10k. Is that too low.? I realise there isn't much power in that frequency range.
Just sat down to listen to them sans grilles.!
Yes indeed very much enjoying them and the knowledge I have gained is also invaluable. You can give yourself a firm pat on the back! Trouble is now i want to build more speakers.!
I tried adding an 'ambience' tweeter into XSIM. Just picking a cheap Dayton Audio job as the frd and zma are readily available....just out of interest. I added the 60 off axis files although they would be more like 180. It does lower the overall system impedance to 3 ohms ish above 10k. Is that too low.? I realise there isn't much power in that frequency range.
Just sat down to listen to them sans grilles.!
Yes indeed very much enjoying them and the knowledge I have gained is also invaluable. You can give yourself a firm pat on the back! Trouble is now i want to build more speakers.!
Hello Jim,
May I please ask you if the measurments showed are in room or in the garden.
It's about bafle step, I see you have non compensation, do you remember the -f3 in your home with the speakers near the wall I assume ?
I'm glad to see that a second order low pass on the SB17 was enough for the upper breaks-up as I plan something neear with the ceramic version but with a lower cutt-off (around 700 hz :compact 3 ways).
May I please ask you if the measurments showed are in room or in the garden.
It's about bafle step, I see you have non compensation, do you remember the -f3 in your home with the speakers near the wall I assume ?
I'm glad to see that a second order low pass on the SB17 was enough for the upper breaks-up as I plan something neear with the ceramic version but with a lower cutt-off (around 700 hz :compact 3 ways).
Hi. Measurements were done outside. Approx 1200mm off the grass at a guess.
No BSC in these speakers as I listen with them close to back walls and near side walls I have good room gain.
Very impressed with the SB17s. 700Hz and you'll be well in. The 5k break up on these seems to he well controlled with the cross over that Chris designed. Admittedly we haven't measured them since.
No BSC in these speakers as I listen with them close to back walls and near side walls I have good room gain.
Very impressed with the SB17s. 700Hz and you'll be well in. The 5k break up on these seems to he well controlled with the cross over that Chris designed. Admittedly we haven't measured them since.
Well, caps add in value as you put more in parallel. Grab a couple of 0.47uF per side, connect them at one end and then twist the wires together at the other to make the connection. Easy to add one at a time, switch out, etc.
3ohm at 10kHz will be fine.
Glad you're enjoying them.
What're your thoughts with the grilles removed?
All the best,
Chris
I'm thinking that the 'acoustically transparent' grille material is filtering down the HF a bit. Definitely a bit brighter with them off. Perhaps not a surprise.!
Didn't transform them but interesting nonetheless. Pity they look a bit of a pig without them! I may redo the baffle and make it 'pretty ' so as to get away grilleless and then I can recess drivers properly and roundover the edges. ( I have a router circle jig now so can do decent rebates.)
I guess my XO doesn't take into account CTC spacing? So I am not bound by the spacing they are at now?
Didn't transform them but interesting nonetheless. Pity they look a bit of a pig without them! I may redo the baffle and make it 'pretty ' so as to get away grilleless and then I can recess drivers properly and roundover the edges. ( I have a router circle jig now so can do decent rebates.)
I guess my XO doesn't take into account CTC spacing? So I am not bound by the spacing they are at now?
A long time later and I plugged these back into the system ....now with a class a 30w NP design amp. NOW they sound really good! Maybe a system synergy thing but all my previous doubts about them seem to have vanished. Maybe they want some current up them, but they are quite sensitive. Maybe the low impedance (4r woofer/6r tweeter) .?!
Anyways I thought now they deserve a new outlook and the classic recessed Leak aluminium trim wouldn't be doing the diffraction any good. So I built some new baffles and incorporated a port that I had dabbled with. I was avoiding BR but it did help a little without becoming a 1 note job.
I padded over the new MDF baffle with some poly lining. That helped recess the drivers into the material. Ironically th main fabric is ab acoustic grille cloth but as you can see I don't use that element of it!
I'm not fond of the port flare. Spent hours making that out of some timber I felled and it was sat in the fire pile. Didn't come out how I imagined.
Anyways I thought now they deserve a new outlook and the classic recessed Leak aluminium trim wouldn't be doing the diffraction any good. So I built some new baffles and incorporated a port that I had dabbled with. I was avoiding BR but it did help a little without becoming a 1 note job.
I padded over the new MDF baffle with some poly lining. That helped recess the drivers into the material. Ironically th main fabric is ab acoustic grille cloth but as you can see I don't use that element of it!
I'm not fond of the port flare. Spent hours making that out of some timber I felled and it was sat in the fire pile. Didn't come out how I imagined.
