Returning to this after some time seeking feedback/assistance on a design based around the ND91.
The goal is to derive as much performance as possible within the limits of a small enclosure (0.5l) while placing no constraints whatsoever on amplifiers or other components. The design is a 2-way now employing a small 3/4" Vifa. Bi-amping has been utilised to date and x-overs are digital and external (currently via a minidsp system).
This effort began quite some time ago and numerous other drivers have been experimented with along the way, always, however, in a same size 0.5l enclosure. The overarching goal is to extract maximal performance despite the constraint of its predetermined size, and do so by any means, regardless of practicality and cost.
To that end, after a period of experimentation with passive radiators and exploration of aperiodic systems, the ND91 used on its own seemed to provide the best result. The 4 ohm version of the driver has been used to date, pairing well with the 4 ohm Vifa tweeter. However, as it is a bi-amped system with digital x-over, accommodating for an 8 ohm's lower SPL in the system would not be an issue if the 8 ohm can offer any performance benefit. Modeling in Bassbox software is providing this picture of response.
http://zweck.weebly.com/about.html
It appears the 8 ohm (red plot) extends somewhat lower than the 4 ohm (yellow plot) but will of course require more amplifier power and/or additional attenuation of the HF driver. I'm curious what do others here think?
A chip-based 2-channel amp has been used for testing. After reviewing posts and info on systems with drivers having significant impedance variation between them, it seems that this can be done if adjusted for in the x-over. Just to be certain, can others here also confirm whether it is essentially 'safe' to drive an 8 ohm ND91 from one side of a 2 ch amp while the other side handles the 4 ohm HF driver? Vifa does not provide an 8 ohm version of these 3/4" HF units.
I've yet to acquire the 8 ohm variant of the ND91 to test, waiting to proceed based upon the responses here. Thank you.
Appreciatively,
Luca
The goal is to derive as much performance as possible within the limits of a small enclosure (0.5l) while placing no constraints whatsoever on amplifiers or other components. The design is a 2-way now employing a small 3/4" Vifa. Bi-amping has been utilised to date and x-overs are digital and external (currently via a minidsp system).
This effort began quite some time ago and numerous other drivers have been experimented with along the way, always, however, in a same size 0.5l enclosure. The overarching goal is to extract maximal performance despite the constraint of its predetermined size, and do so by any means, regardless of practicality and cost.
To that end, after a period of experimentation with passive radiators and exploration of aperiodic systems, the ND91 used on its own seemed to provide the best result. The 4 ohm version of the driver has been used to date, pairing well with the 4 ohm Vifa tweeter. However, as it is a bi-amped system with digital x-over, accommodating for an 8 ohm's lower SPL in the system would not be an issue if the 8 ohm can offer any performance benefit. Modeling in Bassbox software is providing this picture of response.
An externally hosted image should be here but it was not working when we last tested it.
http://zweck.weebly.com/about.html
It appears the 8 ohm (red plot) extends somewhat lower than the 4 ohm (yellow plot) but will of course require more amplifier power and/or additional attenuation of the HF driver. I'm curious what do others here think?
A chip-based 2-channel amp has been used for testing. After reviewing posts and info on systems with drivers having significant impedance variation between them, it seems that this can be done if adjusted for in the x-over. Just to be certain, can others here also confirm whether it is essentially 'safe' to drive an 8 ohm ND91 from one side of a 2 ch amp while the other side handles the 4 ohm HF driver? Vifa does not provide an 8 ohm version of these 3/4" HF units.
I've yet to acquire the 8 ohm variant of the ND91 to test, waiting to proceed based upon the responses here. Thank you.
Appreciatively,
Luca
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Luca,
If you are using the same enclosures (0.5L) there's no benefit of using either of the drivers. They have the same baseline with the 4 Ohms having more 3dB(+/-). The 8 ohms providing more bass extension in adequate (>0.9L) sealed speaker having more space to breathe.😀
DAYTON ND91-4, VB = 0.5 L @70H-73.4dB (85.4-12)
DAYTON ND91-8, VB = 0.9 L @70H-73.4dB (81.9-8.5).
Attachments
The enclosure size is a fixed parameter. These are intended for use in 2.1 system, or on their own in a near field desktop manner. The design brief, essentially, is to obtain the best performance possible in that given size constraint, without restrictions on cost or complexity.
Were you able to look at the link above which models the driver in the 0.5l enclosure? There's a significant increase in response in the 100 to 200Hz range, despite the size, or at least according to the software, and if the driver parameters are correctly given. Here's the link to the response curve in Bassbox again, with the T/S parameters below: About - Zweck
I'm certainly aware that enlargement of the enclosure would have such an expected result. This project, however, is not about producing a more ideal enclosure. It's of course appropriate to enlarge the enclosure under other circumstances, but the focus, the challenge, here is different.
Were you able to look at the link above which models the driver in the 0.5l enclosure? There's a significant increase in response in the 100 to 200Hz range, despite the size, or at least according to the software, and if the driver parameters are correctly given. Here's the link to the response curve in Bassbox again, with the T/S parameters below: About - Zweck
I'm certainly aware that enlargement of the enclosure would have such an expected result. This project, however, is not about producing a more ideal enclosure. It's of course appropriate to enlarge the enclosure under other circumstances, but the focus, the challenge, here is different.
With digital equalization you could improve the frequency response somewhat (either vented or sealed), but you lose out in maximum volume of course. How loud are you playing these?
Linkwitz Transform
Also, why not have one amp power the two tweeters, and one amp power the two woofers? That way you can adjust the levels by adjusting the volume on the amps instead of (in addition to?) using the MiniDSP.
Linkwitz Transform
Also, why not have one amp power the two tweeters, and one amp power the two woofers? That way you can adjust the levels by adjusting the volume on the amps instead of (in addition to?) using the MiniDSP.
You can leave the back of the box open OR make a lot of holes ( for having total hole area= Sd ). Cover the holes with fabric.
Yes, it adds some damping around Fs. Keep the internall stuffed as usual ( cotton wadding ?! )
Yes, it adds some damping around Fs. Keep the internall stuffed as usual ( cotton wadding ?! )
The volumes are moderate and a vented design of any kind has thusfar not shown itself to be preferable.
An amplifier will likely be custom designed and built based on the prototyping done here.
In the 0.5l enclosure, which is a fixed parameter that I won't be altering, Bassbox modeling actually shows a significant increase in response in the 100 to 200Hz range for the 8 ohm (red) over the 4 ohm (yellow). Please see it here:
About - Zweck
This is surprising, to me at least, and generated interest in obtaining the 8 ohm version to try a practical test, if there's something not amiss in the modeling.
So much trial an error has gone into this very small setup over a long period of time, and it's really now about extracting a few more drops of performance out of them, but the impression they make seems impressive. The small Vifa tweeter (4 ohm) used, which is powered separately takes up slack in overall detail that the 3.5" driver, already working so hard, cannot cover. The finest I'm aware of in this very small size category, but obviously with considerable expense on all the elements involved and some aspects of the enclosure that I've not detailed here.
So what do you and others think - is there enough cause to switch over, or at least try, the 8 ohm based on all the above?
An amplifier will likely be custom designed and built based on the prototyping done here.
In the 0.5l enclosure, which is a fixed parameter that I won't be altering, Bassbox modeling actually shows a significant increase in response in the 100 to 200Hz range for the 8 ohm (red) over the 4 ohm (yellow). Please see it here:
About - Zweck
This is surprising, to me at least, and generated interest in obtaining the 8 ohm version to try a practical test, if there's something not amiss in the modeling.
So much trial an error has gone into this very small setup over a long period of time, and it's really now about extracting a few more drops of performance out of them, but the impression they make seems impressive. The small Vifa tweeter (4 ohm) used, which is powered separately takes up slack in overall detail that the 3.5" driver, already working so hard, cannot cover. The finest I'm aware of in this very small size category, but obviously with considerable expense on all the elements involved and some aspects of the enclosure that I've not detailed here.
So what do you and others think - is there enough cause to switch over, or at least try, the 8 ohm based on all the above?
Hi,
With a digital x/o you can choose any bass alignment you like.
Easy to set the 4 ohm the same as the 8 ohm, or anything else.
rgds, sreten.
With a digital x/o you can choose any bass alignment you like.
Easy to set the 4 ohm the same as the 8 ohm, or anything else.
rgds, sreten.
😕
Answer in my previous (#2) post. e.g.:
DAYTON ND91-4, 85.4dB
DAYTON ND91-8, 81.9dB
Inductor, I'm not quite following - are you pointing to the ND91-8 producing a lower SPL and viewing that as a disadvantage, even though I can compensate with additional power as there are no constraints on what can be used in terms of an amplifier? The enclosure size will not change - a larger one will not comply with the design brief, so we're doing all that's possible to extract any gains in performance in that small enclosure, without limitations in terms of cost or practicality.
The simulation in the link I posted depicts a +3db increase for the 8 ohm over the 4 ohm in the 100-200Hz range with the hump peaking around 175Hz. I'm asking whether others see that as a performance increase of any value. If so, the 8 ohm will be given a try.
The simulation in the link I posted depicts a +3db increase for the 8 ohm over the 4 ohm in the 100-200Hz range with the hump peaking around 175Hz. I'm asking whether others see that as a performance increase of any value. If so, the 8 ohm will be given a try.
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