|Yamaha NS-1000M Updated
I've had a few classic speakers now, including Tannoy Cheviots, Celestion 66 Monitors and the Yamaha NS-1000M. They were all good in their day, have some good attributes and a pleasant sound. But compared to modern designs, they are ultimately flawed or coloured and no amount of tweaking can disguise this. I reached this conclusion after hearing many examples of each, either in stock, renovated or highly modified form.
As much as I like the Yamaha NS-1000M speakers, I don't see them through rose tinted specs and I'm well aware of their short comings. Namely, a bass that rolls off quickly, having a -3dB point of only 52Hz. Similarly a tweeter with a ragged bottom end and which rolls off sharply at around 14kHz, being some 6dB down by 20kHz (Response graph in Yamaha manual and confirmed by Troels Grevensen's measurements). The mid driver is slightly compromised, by being pushed to its upper limit to achieve a high crossover point, which disguises the tweeters short comings.
The essence of the NS-1000M is the superb beryllium dome mid range, also, while not deep, through use of a sealed enclosure, it has a clean, tight bass and the overall dispersion characteristics are excellent.
For some time I have been contemplating an improved and modernized version of this speaker, the "NS-1000M Updated". The results from my NS-1000M upgrades and semi active projects have contributed ideas towards this goal. By using the superb mid range and adding a better tweeter and woofer, I hope to achieve this. The project does take an unexpected turn, so read on.
The Scanspeak 12" bass (As used in my semi active project) works well in a similar volume to the Yamaha but goes significantly deeper. It's an easy choice, as it continues the tradition of using a sealed enclosure, so has all the benefits, namely the ability to work well in a less than ideal room size/shape.
The first speakers I ever built, were a Wilmslow Audio 2-way floor standing kit, using a 10" Peerless mid/bass and the now famous Peerless HDS Tweeter. What sticks in my mind about these speakers was the superb top end, which was light, airy and free from distortion. They had the rising response associated with this tweeter, which at the time I was not knowledgeable enough to tackle. But the memory of this tweeter has stuck with me and I have not heard better in the 30 years that have passed since I built them. Several people have since tamed the rising response of the HDS Tweeter using a simple wave guide, a fact that has not eluded me and I have wanted to re-visit this driver for several years. The HDS also has a similar impedance and sensitivity to the Yamaha mid range and they have a very wide overlap in their frequency response allowing a lot of freedom in selecting the crossover point. This seems the ideal project for it.
I am also very fond of the Fountek Neo X range of ribbon tweeters, that I used in my semi active project. They don't measure as well as the HDS but sound good subjectively and are not spity like many low cost ribbons. I have these in reserve should the HDS not work out.
Therefore the parameters and starting point for this project:
Peerless HDS Tweeter/waveguide - Gives a cleaner, more extended top end (F3 21kHz).
Yamaha Beryllium Dome Midrange - Basically this is good, improve by reducing the top x-over point.
Scanspeak 12" Bass in 55L sealed enclosure - Deeper bass (F3 38Hz) but still detailed and clean.
Active Digital Crossover - Highly tweekable to optimize the response of each driver.
So moving from a +/-3dB response of 52Hz-17Khz to 38Hz-21kHz. With some DSP bass lift an option, to get even lower if desired, the driver is easily capable, both on power handling and XMax.
They could end up looking something like this:
A quick run down of the drivers