It is a fairly thick reasonably flexible pvc cloth that I bought 7 years ago from a camping shop at €8/meter and used for my previous project. As there was an error in the middle of the 6 meter stretch I received a second piece of 6 meter. So I still had this as leftover.
Long story short. When I tried to order it again they didn’t have this anymore. The replacement material they had was thinner and not stretchy.
My fellow builder Joost ordered other material at €49/meter with a more leather structure that also works fine and is stretchy.
But the material is used for car interiors or furniture where non uniform surfaces need to be covered.
The use of a vacuum table is very helpful when applying this
Long story short. When I tried to order it again they didn’t have this anymore. The replacement material they had was thinner and not stretchy.
My fellow builder Joost ordered other material at €49/meter with a more leather structure that also works fine and is stretchy.
But the material is used for car interiors or furniture where non uniform surfaces need to be covered.
The use of a vacuum table is very helpful when applying this
And the Tuning started, not quite that straightforward as it started with hurdles.
First the 3 way active cross-over from Electro Voice, the DC-one, didn't connect via USB, The Native Instruments Komplete Audio 6 intermittently disconnected, That all solved after reinstalling and fiddling. The Hypex was also not seen by my laptop (too many USB drivers I guess), but my wife's laptop came to the rescue. My super-duper measuring stand with extended pole didn't pass the mic signal (new mike stand) and it was fine after opening an closing the tube.
so all took longer than anticipated. One problem remained and that is the balanced to unbalanced connection from DC-one to the 4 channel NAD amplifier produces quite some noise, no hum, noise. I haven't used this DC-one since my last speaker project 7 years ago and I can't remember it was noisy. I used balanced inputs of a different multi channel amp that time.
Okay.. time to do the impedance measurements with DATS, this worked fine, quite as expected (but the tweeter impedance file does something strange in VituixCAD that I can't explain other than that the measurement was done trough the internal cabling.
So after these hurdles I started setting up the DC one and music came out. cross-over at 300Hz 4t order LR and at 2800Hz second order.
then the next strange thing happened; The company Audionet that I used a long time with a surround pre, and 7 channel massive power amp produced a very neat program called Carma. works like a charm normally, very intuitive and good repeatable measurements.
But when I sweeped the system a chirp sweep on the left channel it did not produce sound out of the left tweeter, and not out of the right woofer. I tried everything, swapped cables....nothing. the minute I put on music all is fine. The chirp starts with a special puls that I think is used to start the analysis must trigger something in the DC one.
The real measurements should be done by a more widely used and accepted program and that is ARTA. Everybody raves about it but I find it less intuitive. But I managed to get some readings and they did seem to show approximately as expected but different from the Carma readings ...... more for a next time.
Stay tuned .......
First the 3 way active cross-over from Electro Voice, the DC-one, didn't connect via USB, The Native Instruments Komplete Audio 6 intermittently disconnected, That all solved after reinstalling and fiddling. The Hypex was also not seen by my laptop (too many USB drivers I guess), but my wife's laptop came to the rescue. My super-duper measuring stand with extended pole didn't pass the mic signal (new mike stand) and it was fine after opening an closing the tube.
so all took longer than anticipated. One problem remained and that is the balanced to unbalanced connection from DC-one to the 4 channel NAD amplifier produces quite some noise, no hum, noise. I haven't used this DC-one since my last speaker project 7 years ago and I can't remember it was noisy. I used balanced inputs of a different multi channel amp that time.
Okay.. time to do the impedance measurements with DATS, this worked fine, quite as expected (but the tweeter impedance file does something strange in VituixCAD that I can't explain other than that the measurement was done trough the internal cabling.
So after these hurdles I started setting up the DC one and music came out. cross-over at 300Hz 4t order LR and at 2800Hz second order.
then the next strange thing happened; The company Audionet that I used a long time with a surround pre, and 7 channel massive power amp produced a very neat program called Carma. works like a charm normally, very intuitive and good repeatable measurements.
But when I sweeped the system a chirp sweep on the left channel it did not produce sound out of the left tweeter, and not out of the right woofer. I tried everything, swapped cables....nothing. the minute I put on music all is fine. The chirp starts with a special puls that I think is used to start the analysis must trigger something in the DC one.
The real measurements should be done by a more widely used and accepted program and that is ARTA. Everybody raves about it but I find it less intuitive. But I managed to get some readings and they did seem to show approximately as expected but different from the Carma readings ...... more for a next time.
Stay tuned .......
Update:
to remove a few quirks and fairly high noise of the DC-one I ordered a miniDSP HTx from www.miniDSP.nl and that will be the temporarily cross-over for tweaking the speaker in the next months. The unit is extremely powerful with 8 analog inputs and 8 analog outputs, HDMI, TosLink, S/PDIF and USB in. The unit will most likely end up in my office setup as a sound card as it comes with 19"rack ears. Specs are extremely good with ultra low noise and distortion.
Easy to setup X-over slopes and frequencies and 10x PEQ controls to tweak the speakers
stay tuned....
Peter
to remove a few quirks and fairly high noise of the DC-one I ordered a miniDSP HTx from www.miniDSP.nl and that will be the temporarily cross-over for tweaking the speaker in the next months. The unit is extremely powerful with 8 analog inputs and 8 analog outputs, HDMI, TosLink, S/PDIF and USB in. The unit will most likely end up in my office setup as a sound card as it comes with 19"rack ears. Specs are extremely good with ultra low noise and distortion.
Easy to setup X-over slopes and frequencies and 10x PEQ controls to tweak the speakers
stay tuned....
Peter
I think you will be impressed by the performance of the MiniDSP Flex, considering the modest cost...
At this level of performance, wouldn't it be better to take 360-degree measurements for the vituixcad simulation? Spinoramaz etc.?
I think we can do without. It doesn’t matter to me what comes out of the speaker from the back when it faces the wall. You need a really big room to get a meaningful measurement of a speaker that you spin.
I didn’t last time and the end result was stellar. In the end what the performance is in the sweet spot when listening is what counts and the tweaking based on measurements is a start but the last bits are done by ear.
I remember the last time I changed the value of an inductor in the mid section to a slightly different value (the next one in the E12 range) and it measured better but part of the magic was gone. So I went back to the earlier value.
I didn’t last time and the end result was stellar. In the end what the performance is in the sweet spot when listening is what counts and the tweaking based on measurements is a start but the last bits are done by ear.
I remember the last time I changed the value of an inductor in the mid section to a slightly different value (the next one in the E12 range) and it measured better but part of the magic was gone. So I went back to the earlier value.
An interesting update.
The MiniDSP Flex HTx is really a very nice piece of equipment.
It is low noise (inaudible) and the adjustments are giving reliable changes confirmed with measurements.
I now use the standard front end (dCS Bartok, Sim Audio Moon 740p) into the MiniDSP direct into the Hypex for LF and a 4 channel NAD C-245BEE.
And the miniDSP, and NAD will be the limiting factor in ultimate transparency it sounds already very good.
What I also want share is something really interesting wrt to port dimensions and tuning.
I always relied on the simulation of WinISD and recently VituixCAD for the port tuning.
The tuning frequency of the enclosure and LF units was came advised by VituuxCAD on 30Hz.
I like a slightly lower tuning frequency as I have an ugly resonance in the room at 32Hz.
The enclosure is nett 55 liter, with damping this should calculate to 60/65 liter.
With the port in still at its maximum length (approximately 41cm = 40cm + Flange) VituixCAD came with the following simulation:
@65 liter with a resonance frequency of 26.9 Hz the port length is 41 cm
The left impedance peak shows 16,2 Ohm at 13.6 Hz and the right one 19,3 Ohm at 57.4Hz
So I was really surprised that the initial measurement with DATS showed:
A resonance frequency of around 38/39Hz. The left peak on 19Hz and the right peak on 63Hz.
Also the resonance frequency dip in the saddle curve should be as low as possible as that tells something on the quality of the enclosure.
The latter was mentioned in a very interesting AES NL section presentation by Mark Devlaeminck about enclosures.
So two problems: the Resonance frequency is way too high, and the dip not as low as I hoped for.
But I did not secure the bass port with screws and rubber adhesive between flange and port as it felt very snug and I expected to need to change the length as Troels Gravesen mentioned that the length in practice needs to be shorter than simulated.
Still troubled by the unexpected high tuning frequency I decided to fix the port to the enclosure:
nothing special. from a port that was held in place by itself (tight fit) to screwed to the enclosure with an adhesive foam tape inbetween.
A did not expect what happened next:
The resonance frequency dropped from 38/39 Hz to around 26/27 Hz
The left peak at 14.8Hz and right at 58Hz
Way closer to the simulation with exact the length used.
And the dip in the saddle went from around 5,6 Ohm to 4,2 ohm...... als because I secured the port flange to the enclosure.
I am very surprised by this but it is a good lesson.
Hope you find this interesting.
Cheers,
Peter
The MiniDSP Flex HTx is really a very nice piece of equipment.
It is low noise (inaudible) and the adjustments are giving reliable changes confirmed with measurements.
I now use the standard front end (dCS Bartok, Sim Audio Moon 740p) into the MiniDSP direct into the Hypex for LF and a 4 channel NAD C-245BEE.
And the miniDSP, and NAD will be the limiting factor in ultimate transparency it sounds already very good.
What I also want share is something really interesting wrt to port dimensions and tuning.
I always relied on the simulation of WinISD and recently VituixCAD for the port tuning.
The tuning frequency of the enclosure and LF units was came advised by VituuxCAD on 30Hz.
I like a slightly lower tuning frequency as I have an ugly resonance in the room at 32Hz.
The enclosure is nett 55 liter, with damping this should calculate to 60/65 liter.
With the port in still at its maximum length (approximately 41cm = 40cm + Flange) VituixCAD came with the following simulation:
@65 liter with a resonance frequency of 26.9 Hz the port length is 41 cm
The left impedance peak shows 16,2 Ohm at 13.6 Hz and the right one 19,3 Ohm at 57.4Hz
So I was really surprised that the initial measurement with DATS showed:
A resonance frequency of around 38/39Hz. The left peak on 19Hz and the right peak on 63Hz.
Also the resonance frequency dip in the saddle curve should be as low as possible as that tells something on the quality of the enclosure.
The latter was mentioned in a very interesting AES NL section presentation by Mark Devlaeminck about enclosures.
So two problems: the Resonance frequency is way too high, and the dip not as low as I hoped for.
But I did not secure the bass port with screws and rubber adhesive between flange and port as it felt very snug and I expected to need to change the length as Troels Gravesen mentioned that the length in practice needs to be shorter than simulated.
Still troubled by the unexpected high tuning frequency I decided to fix the port to the enclosure:
nothing special. from a port that was held in place by itself (tight fit) to screwed to the enclosure with an adhesive foam tape inbetween.
A did not expect what happened next:
The resonance frequency dropped from 38/39 Hz to around 26/27 Hz
The left peak at 14.8Hz and right at 58Hz
Way closer to the simulation with exact the length used.
And the dip in the saddle went from around 5,6 Ohm to 4,2 ohm...... als because I secured the port flange to the enclosure.
I am very surprised by this but it is a good lesson.
Hope you find this interesting.
Cheers,
Peter
Yes, very interesting!
I could imagine there was either a small air leak that raised resonance frequency and lowered the Qb. Or the entire port was (slightly) moving.
Air tightness is even more important with ported enclosures than with sealed (sic!) ones.
Wow awesome drawings. I bet you would be a good teacher on CAD Drawnings. I love the detailing it’s awesome. Can’t wait for the finished project.
Hi Jeffrey 01. They are finished (only the filter is under construction)
See the rest of the thread, and thy look even better in real life.
See the rest of the thread, and thy look even better in real life.
I see mid and tweeter circuits, but no woofer circuit. Can we see the woofer network too, please?
Hi wolf_teeth, the LPF is done by the DSP in the Hypex.
The HPF for mid will be done by a custom build analog active filter. As the components needed for. 2,8 ohm at 150/200Hz are bulky and expensive.
It needed 150 and 300uF for a 4th order LR filter
Until that active crossover is done I will use the MiniDSP unit mentioned before.
This is the layout
Ground needs to be poured.
Opamps are discrete Sparkos, input and output transformer coupled with Lundahl. And a Didden/Jung super regulator for supply
The HPF for mid will be done by a custom build analog active filter. As the components needed for. 2,8 ohm at 150/200Hz are bulky and expensive.
It needed 150 and 300uF for a 4th order LR filter
Until that active crossover is done I will use the MiniDSP unit mentioned before.
This is the layout
Ground needs to be poured.
Opamps are discrete Sparkos, input and output transformer coupled with Lundahl. And a Didden/Jung super regulator for supply
While I have read the whole thread, it has been awhile. Thanks for the refresher, as I did not recall the woofers were separately active.
Ow, funny you mention him. I see he’s back in audio. Mark and I share a little bit of history. He’s a clever guy and thinks out of the box at important moments…
The VituixCad simulation did not bring the required result. Although it helps where to tweak but something is off. I did manage to get a frequency response after some modifications of some values. But I like to have this more in line with each other.
Again it is starting to sound really good also with the passive filter.
Again it is starting to sound really good also with the passive filter.