I found them! and they are reasonably massive!
1-11-075-1 Is printed on the backplate
And the other has a label:
Our Model No 048529
Sample 115-8245 23lbs
Imp. 11.7ohms at 100hz.
Date 2000.6.27
FOSTER
I have a note I taped on the frame of one at some time or another saying:
"1.5cuft sealed". I put it on there but don't remember if it was at the time we got them or much later.....
I do want to use them sealed. And i do remember you telling me what size box to use.
If that seems "about right" then it's probably "right" ! It just seemed a tad big to me so wondering if that's for one or both.
Thanks
1-11-075-1 Is printed on the backplate
And the other has a label:
Our Model No 048529
Sample 115-8245 23lbs
Imp. 11.7ohms at 100hz.
Date 2000.6.27
FOSTER
I have a note I taped on the frame of one at some time or another saying:
"1.5cuft sealed". I put it on there but don't remember if it was at the time we got them or much later.....
I do want to use them sealed. And i do remember you telling me what size box to use.
If that seems "about right" then it's probably "right" ! It just seemed a tad big to me so wondering if that's for one or both.
Thanks
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Mark,
Parameters for the woofers are attached.
If you put each driver in a 65l (2.3cu ft) box and tune to 33.7Hz with a port, the system will be -3dB at 25Hz.
In the NHT system they were designed for, they were used in a sealed box and had eq applied to them to extend the response. If you want to do that. let me know.
Parameters for the woofers are attached.
If you put each driver in a 65l (2.3cu ft) box and tune to 33.7Hz with a port, the system will be -3dB at 25Hz.
In the NHT system they were designed for, they were used in a sealed box and had eq applied to them to extend the response. If you want to do that. let me know.
Attachments
Thank you for the help. Were they the drivers in that NHT 10” sub that they sold tons of? Or were they for a specific speaker? Just curious. If you have more info about the sealed configuration and eq on hand I’m interested, but I probably won’t get to them for a year so no rush...
Glad you’re still around here! Burning Amp is probably only online this year. But we are interested in getting lots of presentations recorded if you're interested.
That year you at NHT donated all that stuff was epic!
Mark
Glad you’re still around here! Burning Amp is probably only online this year. But we are interested in getting lots of presentations recorded if you're interested.
That year you at NHT donated all that stuff was epic!
Mark
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Mark,
These woofers were used in the Sub2. Two 10" woofers in a sealed box with a 500W Sunfire plate amplifier. The manual for that subwoofer is at the link below. The cabinet walls were 0.81" thick.
https://www.nhthifi.com/downloads/3124-sub-two
The eq would have been a shelf filter with a high pass at around 20Hz. I don't have curves for the eq circuit that was used. You can plug the driver parameters into any box modeling software and add a Linkwitz transform to it, to get response down to 20Hz fairly easily.
These woofers were used in the Sub2. Two 10" woofers in a sealed box with a 500W Sunfire plate amplifier. The manual for that subwoofer is at the link below. The cabinet walls were 0.81" thick.
https://www.nhthifi.com/downloads/3124-sub-two
The eq would have been a shelf filter with a high pass at around 20Hz. I don't have curves for the eq circuit that was used. You can plug the driver parameters into any box modeling software and add a Linkwitz transform to it, to get response down to 20Hz fairly easily.
I'm hoping this is the right place to post questions because this is the only thread about the m60s I could find that was at least somewhat active.
So I picked up a pair of NHT m60s today for $20. Yes TWENTY DOLLARS!!! The owner said he received them from a friend who lost the XdA amp after moving several times. I guess I might misplace the brains of a $3000 system if I were moving frequently too...
Anyway, I've been doing a lot of research on these speakers and the XdA amps are very hard to find, still very expensive, and at risk of dying at any moment given their age. So it seems like a MiniDSP 2x4 (IIR crossovers only) or HD2x4 (FIR + IIR) would be decent approach to powering these lovely speakers.
MiniDSP has a few good application notes (sort of like blogs) with tutorials on how to use rePhase to create an FIR filter. I happen to have just purchased a UMIK-1 so I would just need the MiniDSP itself to get started.
I've never done any crossover design myself but I do have a masters in mechanical engineering from over a decade ago (has not been used since changing careers in 2010). I'm hoping someone here can provide any tips or suggestions on how to get these speakers working without an XdA and without breaking the bank! Is MiniDSP a good approach? Thanks in advance!
Also, MiniDSP recommends putting a capacitor in series with the tweeter before connecting it to protect it from low frequency data. Anyone know if that recommendation is valid for the m60?
So I picked up a pair of NHT m60s today for $20. Yes TWENTY DOLLARS!!! The owner said he received them from a friend who lost the XdA amp after moving several times. I guess I might misplace the brains of a $3000 system if I were moving frequently too...
Anyway, I've been doing a lot of research on these speakers and the XdA amps are very hard to find, still very expensive, and at risk of dying at any moment given their age. So it seems like a MiniDSP 2x4 (IIR crossovers only) or HD2x4 (FIR + IIR) would be decent approach to powering these lovely speakers.
MiniDSP has a few good application notes (sort of like blogs) with tutorials on how to use rePhase to create an FIR filter. I happen to have just purchased a UMIK-1 so I would just need the MiniDSP itself to get started.
I've never done any crossover design myself but I do have a masters in mechanical engineering from over a decade ago (has not been used since changing careers in 2010). I'm hoping someone here can provide any tips or suggestions on how to get these speakers working without an XdA and without breaking the bank! Is MiniDSP a good approach? Thanks in advance!
Also, MiniDSP recommends putting a capacitor in series with the tweeter before connecting it to protect it from low frequency data. Anyone know if that recommendation is valid for the m60?
They lost an XdA? That's mind blowingly stupid.
You want the crossover frequency to be at 2.3kHz, for the best power response. You will need to add in some shelving EQ to flatten out the woofers response down to whatever cutoff frequency you choose.
The only reason to put a capacitor in series with the tweeter is if the power amplifier you use, has some sort of DC when it turns on/off or the DSP you are using is junk and puts out any low frequencies that it shouldn't. If you do install a capacitor, make sure that it is nonpolarized, really large and nonelectrolytic. Something like 100uF.
Pretty obviously terminal A goes to -W, B goes to +W, C goes to -T, and D goes to +T.
You want the crossover frequency to be at 2.3kHz, for the best power response. You will need to add in some shelving EQ to flatten out the woofers response down to whatever cutoff frequency you choose.
The only reason to put a capacitor in series with the tweeter is if the power amplifier you use, has some sort of DC when it turns on/off or the DSP you are using is junk and puts out any low frequencies that it shouldn't. If you do install a capacitor, make sure that it is nonpolarized, really large and nonelectrolytic. Something like 100uF.
Pretty obviously terminal A goes to -W, B goes to +W, C goes to -T, and D goes to +T.
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Thank you for the quick response Jack! Cross over, capacitor, and terminal tips much appreciated.
Do you foresee a significant benefit to using a FIR vs IIR crossover? The miniDSP HD2x4 (FIR + IIR) is $200 vs $100 for the 2x4 (IIR only). Based on the audiogon thread linked below, it seems the XdA used FIR filters to minimize phase shift issues but some posters suggested the difference compared to a passive crossover was not significant. Just wanted to check before I drop the extra cash on the HD2x4.
The system I have in mind is:
Source > SPDIF/analog > MiniDSP HD2x4 use FIR crossover & PEQ to split into 4 channels > RCA cable > AVR with 6-ch in, use AVR's crossover to split LF to sub > Sub & M60s
Also for anyone else looking to do this here's a helpful thread from audiosciencereview of some folks trying to use various DSPs to run the XdS: https://www.audiosciencereview.com/...nd-other-digital-active-speaker-systems.7731/
And another audiogon thread with folks discussing the XdA. One poster suggesting a passive (which has the same phase issues as IIR I think) crossover sounding about as good as an FIR crossover:
https://forum.audiogon.com/discussions/is-the-nht-xd-system-worth-buying-today
And a link to the MiniDSP rephase application note for creating FIR filters: https://www.minidsp.com/applications/advanced-tools/rephase-fir-tool
Do you foresee a significant benefit to using a FIR vs IIR crossover? The miniDSP HD2x4 (FIR + IIR) is $200 vs $100 for the 2x4 (IIR only). Based on the audiogon thread linked below, it seems the XdA used FIR filters to minimize phase shift issues but some posters suggested the difference compared to a passive crossover was not significant. Just wanted to check before I drop the extra cash on the HD2x4.
The system I have in mind is:
Source > SPDIF/analog > MiniDSP HD2x4 use FIR crossover & PEQ to split into 4 channels > RCA cable > AVR with 6-ch in, use AVR's crossover to split LF to sub > Sub & M60s
Also for anyone else looking to do this here's a helpful thread from audiosciencereview of some folks trying to use various DSPs to run the XdS: https://www.audiosciencereview.com/...nd-other-digital-active-speaker-systems.7731/
And another audiogon thread with folks discussing the XdA. One poster suggesting a passive (which has the same phase issues as IIR I think) crossover sounding about as good as an FIR crossover:
https://forum.audiogon.com/discussions/is-the-nht-xd-system-worth-buying-today
And a link to the MiniDSP rephase application note for creating FIR filters: https://www.minidsp.com/applications/advanced-tools/rephase-fir-tool
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Since the chain of possession is kinda vague, possibly these were some of the speakers that Jack blew out years ago without the XdA.
I’m still in contact with a guy that got a pair of the NHT towers with crossovers hanging off the back, that we raffled off at Burning Amp. He still uses them and loves them! They do sound great!
I’m still in contact with a guy that got a pair of the NHT towers with crossovers hanging off the back, that we raffled off at Burning Amp. He still uses them and loves them! They do sound great!
The link below goes over the main differences between FIR and IIR filters.
https://www.minidsp.com/applications/dsp-basics/fir-vs-iir-filtering
The main advantage of FIR filters is that with them, it is POSSIBLE to make the entire system have a constant group delay (zero nonlinear phase shift). The vast majority of audio research shows that zero versus reasonable amounts of nonlinear phase shift are not differentiable in listening tests. I'm sure that you will have no problem finding any number of people you want, who will disagree with 75 years of research on this.
The critical thing to realize here is that phase shift between different outputs of the system, on the same channel, (LW and LM for instance) can be extremely audible because it can generate destructive interference in the frequency domain. If you use IIR filters and they are programmed correctly, this should never be a problem, however to program them properly, the software MUST have some type of ability to provide delay adjustments on the different outputs. This is solely needed to adjust for the zero delay plane distance of each driver relative to the listening position. Between the woofer and tweeter for instance, you will only need a total adjustment of about 0.5msec maximum (6").
If the FIR filters have enough taps and there is enough memory available, it can equalize the phase response down to a very low frequency. The downside to this is that the total group delay through the system is going to be longer. If your audio has a total delay of 2msec, that won't be any problem with video, where it would cause a 0.1 frame delay. If you wanted to equalize the phase response down to 50Hz, that could cause a several frame delay.
If you have 6 amplifier channels available, I would use a DSP unit with at least 2 inputs and 6 outputs. That way both crossover regions can be handled in the digital domain. That is a massive advantage as it allows one to get the subwoofer and woofer audio outputs exactly in phase at the crossover frequency. The way that almost all modern receivers are implemented, if you use their internal crossover functions, there is no chance of getting the subwoofer to woofer region correct. In your receiver you then set the L and R channels as full range and send any LFE information to them. That is the ONLY way to get decent performance out of the Dolby legacy bass (mis)management system.
The single most important thing here is that you learn how to take accurate acoustic measurements. If you don't do that, you will be sending junk data to the software to generate the filters. As they say, garbage in, garbage out.
https://www.minidsp.com/applications/dsp-basics/fir-vs-iir-filtering
The main advantage of FIR filters is that with them, it is POSSIBLE to make the entire system have a constant group delay (zero nonlinear phase shift). The vast majority of audio research shows that zero versus reasonable amounts of nonlinear phase shift are not differentiable in listening tests. I'm sure that you will have no problem finding any number of people you want, who will disagree with 75 years of research on this.
The critical thing to realize here is that phase shift between different outputs of the system, on the same channel, (LW and LM for instance) can be extremely audible because it can generate destructive interference in the frequency domain. If you use IIR filters and they are programmed correctly, this should never be a problem, however to program them properly, the software MUST have some type of ability to provide delay adjustments on the different outputs. This is solely needed to adjust for the zero delay plane distance of each driver relative to the listening position. Between the woofer and tweeter for instance, you will only need a total adjustment of about 0.5msec maximum (6").
If the FIR filters have enough taps and there is enough memory available, it can equalize the phase response down to a very low frequency. The downside to this is that the total group delay through the system is going to be longer. If your audio has a total delay of 2msec, that won't be any problem with video, where it would cause a 0.1 frame delay. If you wanted to equalize the phase response down to 50Hz, that could cause a several frame delay.
If you have 6 amplifier channels available, I would use a DSP unit with at least 2 inputs and 6 outputs. That way both crossover regions can be handled in the digital domain. That is a massive advantage as it allows one to get the subwoofer and woofer audio outputs exactly in phase at the crossover frequency. The way that almost all modern receivers are implemented, if you use their internal crossover functions, there is no chance of getting the subwoofer to woofer region correct. In your receiver you then set the L and R channels as full range and send any LFE information to them. That is the ONLY way to get decent performance out of the Dolby legacy bass (mis)management system.
The single most important thing here is that you learn how to take accurate acoustic measurements. If you don't do that, you will be sending junk data to the software to generate the filters. As they say, garbage in, garbage out.
Yes totally possible too. The speakers came with one of the original boxes so they don't seem stolen. The seller said he had hooked them up to an AVR to test them - hopefully he didn't damage the tweeter!
I thought Burning Amp was a typo for Burning Man but I see it's a real event! Love the name and will check it out when it's back in person!!
Thanks for link Jack - I had found it as well (and read it twice!) but you added key missing information: whether nonlinear phase shift is audible!
I was planning to get the 2x4 minidsps which are quite a bit more affordable than the lowest version with six outputs (the car audio designed 6x8). My sub has a continuous phase adjustment from 0 to -180 degrees [see photo below]. Wouldn't the technique outlined in the link below mitigate the phase misalignment at the crossover? The process is to run an RTA and manually adjust the sub phase until I see the crossover frequency (say 80hz) reaches its max value.
"Take another RTA measurement, but this time slowly change the phase control on your sub whilst watching the RTA bar corresponding to the crossover frequency you have chosen."
Source: http://www.acousticfrontiers.com/20...subwoofer-crossover-frequency-slope-and-html/
A couple of comments about your plan.
The variable phase control on your subwoofer is probably an analog control. Given that, it doesn't actually work very well, especially if the crossover frequency is moved away from 80Hz. A digital filter is going to function vastly more accurately by comparison. This will make summation through the crossover region better.
The technique quoted above about using an RTA and adjusting the phase control until there is the most output possible at the crossover frequency, is total waste of time and should never be used. The only proper technique is to take a 100% unsmoothed acoustic frequency response measurement of the high pass and low pass sections, then reverse the phase going to the subwoofer and take an acoustic measurement of both the high and low pass systems. Vary the phase knob as needed to get a null which is as deep as possible at the crossover frequency. Once you get there, flip the phase back on the subwoofer.
This will work and get reasonable results. Doing it with digital filters will give better to much better results, depending on a few different factors. It doesn't make sense to me, to take a speaker system which is among the best ever built and skimp on the crossover functions to save a few dollars. Before spending any money, I would go purchase a copy of the current LDC (Loudspeaker Design Cookbook) by Vance Dickason. Read through the chapters on crossovers. This will show you how simply putting an 80Hz HP and LP filter on the subwoofer and satellite speaker, does not give you the ruler flat acoustic response that a very basic textbook makes it look like you will get. The crossover functions in your receiver are only going to have very basic, textbook filters in them. You are going to have to be able to EQ the response from both speakers, that when the crossover filter in your receiver are applied to them, that the electroacoustic responses have the shape required, so that the resulting response is flat. This will be trivial to do with a proper DSP doing everything.
The variable phase control on your subwoofer is probably an analog control. Given that, it doesn't actually work very well, especially if the crossover frequency is moved away from 80Hz. A digital filter is going to function vastly more accurately by comparison. This will make summation through the crossover region better.
The technique quoted above about using an RTA and adjusting the phase control until there is the most output possible at the crossover frequency, is total waste of time and should never be used. The only proper technique is to take a 100% unsmoothed acoustic frequency response measurement of the high pass and low pass sections, then reverse the phase going to the subwoofer and take an acoustic measurement of both the high and low pass systems. Vary the phase knob as needed to get a null which is as deep as possible at the crossover frequency. Once you get there, flip the phase back on the subwoofer.
This will work and get reasonable results. Doing it with digital filters will give better to much better results, depending on a few different factors. It doesn't make sense to me, to take a speaker system which is among the best ever built and skimp on the crossover functions to save a few dollars. Before spending any money, I would go purchase a copy of the current LDC (Loudspeaker Design Cookbook) by Vance Dickason. Read through the chapters on crossovers. This will show you how simply putting an 80Hz HP and LP filter on the subwoofer and satellite speaker, does not give you the ruler flat acoustic response that a very basic textbook makes it look like you will get. The crossover functions in your receiver are only going to have very basic, textbook filters in them. You are going to have to be able to EQ the response from both speakers, that when the crossover filter in your receiver are applied to them, that the electroacoustic responses have the shape required, so that the resulting response is flat. This will be trivial to do with a proper DSP doing everything.
Thanks again for the tips Jack!
I get what you're saying about the irrationality of putting low quality components up stream of such high end speakers. Then again given the $20 price paid I am still spending 10x on the upstream components! Either way at the moment I can't justify outlaying a lot of cash (6x8 minidsp) so I'm gonna try to give your technique for phase alignment a try along with the setup I described. The minidsp has plenty of EQ capabilities both before and after the digital crossover, so I'll be able to EQ the woofer and tweeter independently. I picked up the components on craigslist this weekend!
While this setup won't let these speakers achieve their full potential, perhaps I'll be able to create the best $200 system on the planet.
I get what you're saying about the irrationality of putting low quality components up stream of such high end speakers. Then again given the $20 price paid I am still spending 10x on the upstream components! Either way at the moment I can't justify outlaying a lot of cash (6x8 minidsp) so I'm gonna try to give your technique for phase alignment a try along with the setup I described. The minidsp has plenty of EQ capabilities both before and after the digital crossover, so I'll be able to EQ the woofer and tweeter independently. I picked up the components on craigslist this weekend!
While this setup won't let these speakers achieve their full potential, perhaps I'll be able to create the best $200 system on the planet.