Soundscape Posted September 29, 2020 Share Posted September 29, 2020 Hi guys, I am looking to upgrade yhe power amp for my Gradient SW 63 subs and looking for suggestions. I am currently running the subs with a Quad 405 Mk2, which is fine a normal listening levels but runs out of steam as the volume goes up. The power amps are fed by a Modwright SWLP hybrid valve preamp that is connected to a Gradient active crossover, which splits the signal and feeds the sub amp frequencies up to 120Hz, with the rest going to a Naksa 100 power amp that drives the ESL63s. I am very happy with the set up overall, the gain structure is a perfect match for the ESLs and sounds amazing even with the volume all the way up to 11 , however at these levels the Quad amp completely loses the plot. 100 Watts gives me plenty of gain, so I'm looking for an amp that is around the 100 watt mark that also possesses the drive and grip to control two 12" drivers per sub at high levels. There is a Bryston 3b in the classifieds that looks the goods, and the price is right, so perhaps I have already answered my question. However being the OCD audiophile like many of us are, I have done some goggling and found various recommendations, ranging from Quad 606 (Gradient recommended), Crown K series (no noisy cooling fans!!) , Alesis Pro amps, Class D amps etc etc. Cosmetics doesn't bother me much and my budget is relatively modest. Perhaps someone with technical knowledge could point me in the right direction (eg volts vs current drive)? Thanks for reading. Over to you! Cheers, Dave Link to comment Share on other sites More sharing options...
andyr Posted September 29, 2020 Share Posted September 29, 2020 56 minutes ago, Soundscape said: Hi guys, I am looking to upgrade yhe power amp for my Gradient SW 63 subs and looking for suggestions. I am currently running the subs with a Quad 405 Mk2, which is fine a normal listening levels but runs out of steam as the volume goes up. The power amps are fed by a Modwright SWLP hybrid valve preamp that is connected to a Gradient active crossover, which splits the signal and feeds the sub amp frequencies up to 120Hz, with the rest going to a Naksa 100 power amp that drives the ESL63s. I am very happy with the set up overall, the gain structure is a perfect match for the ESLs and sounds amazing even with the volume all the way up to 11 , however at these levels the Quad amp completely loses the plot. 100 Watts gives me plenty of gain, so I'm looking for an amp that is around the 100 watt mark that also possesses the drive and grip to control two 12" drivers per sub at high levels. There is a Bryston 3b in the classifieds that looks the goods, and the price is right, so perhaps I have already answered my question. However being the OCD audiophile like many of us are, I have done some goggling and found various recommendations, ranging from Quad 606 (Gradient recommended), Crown K series (no noisy cooling fans!!) , Alesis Pro amps, Class D amps etc etc. Cosmetics doesn't bother me much and my budget is relatively modest. Perhaps someone with technical knowledge could point me in the right direction (eg volts vs current drive)? Thanks for reading. Over to you! Cheers, Dave Looking up a 3b, Dave, I find it is only just a bit more powerful than your existing Quad 405 II. So I would suggest that won't give you much. You don't need finesse for a sub amp - you just need grunt. So I suggest the ideal amp is a Class D - like, say, a Hypex NC500. Someone like @mwhouston could make you up one. Andy 1 Link to comment Share on other sites More sharing options...
niss_man Posted September 29, 2020 Share Posted September 29, 2020 What is the efficiency of the subs in question? Link to comment Share on other sites More sharing options...
Hifiplus Posted September 29, 2020 Share Posted September 29, 2020 Isnt that 3B 110volt which would need a massive stepdown transformer? Ive got a 4 channel class d amp spare for sale if interested. Link to comment Share on other sites More sharing options...
Soundscape Posted September 29, 2020 Author Share Posted September 29, 2020 5 hours ago, niss_man said: What is the efficiency of the subs in question? Great question. I don't know! I can't seem to find that information. Link to comment Share on other sites More sharing options...
Soundscape Posted September 29, 2020 Author Share Posted September 29, 2020 3 hours ago, Hifiplus said: Isnt that 3B 110volt which would need a massive stepdown transformer? Ive got a 4 channel class d amp spare for sale if interested. I thought it had a switchable power supply but I could be wrong Link to comment Share on other sites More sharing options...
Soundscape Posted September 29, 2020 Author Share Posted September 29, 2020 Further reading reveals that Gradient are now selling a new crossover system with integrated power amps using Hypex Ice power modules, so perhaps Class D is the way to go. Link to comment Share on other sites More sharing options...
Soundscape Posted September 29, 2020 Author Share Posted September 29, 2020 I found a data sheet for the drivers used in the subs. 89.3db @ 2.83v/m. There are two drivers per sub arrange as a dipole and the wiring is configured so they can be driven in series or parallel Link to comment Share on other sites More sharing options...
Nada Posted September 29, 2020 Share Posted September 29, 2020 Is it your Quad amp that is the actual problem? Could it be the sub? Your Gradient SW 63 is an open baffle design. Usual recommendations for subwoofer amps may not fit at all well. Open baffles let the woofer oscillate relatively freely and reach the maximum displacement at low frequencies with relatively low watts. The issue you have may not be with your Quad amp power but be with the open baffle sub. Solutions 1. limit low frequencies if you use computer audio and a DAC eg- cut steeply below 40Hz then try 50Hz 2. Borrow a high power amp to test if it is an amp issue, but be careful not to exceed the driver Xmax. If that actually improves things look at a Class-D amp and wire the drivers in parallel for a 4ohm impedance 3. Ask someone who uses Hornresp to model the theoretical power needs and output vs Xmax Link to comment Share on other sites More sharing options...
Cloth Ears Posted September 29, 2020 Share Posted September 29, 2020 19 hours ago, Soundscape said: ... Quad 405 Mk2, ...runs out of steam as the volume goes up...the Quad amp completely loses the plot. Can you describe what you mean by this? Probably easier if you turn off the Naksa in order to describe this better. And then, while you are listening just to your subs, maybe try the Naksa in place of the Quad to see if it also has the same issue. I'm guessing what someone else has said - that it's a driver issue, rather than an amp issue. If you feed too much low-end signal to an open baffle, the Peerless drivers will start to distort and then break. Modelling shows that anything below about 35Hz @100W could be causing you an issue - are you able to add a high-pass (2nd order @35Hz) filter in the signal path? Another option would be to replace the drivers with a driver designed for open baffle (which the Peerless are not). That last octave is elusive when you're using open baffles to create it. You could always get one of those 'normal' box subwoofers to handle the last octave and then you'd have a system that really rocks... Link to comment Share on other sites More sharing options...
stereo coffee Posted September 29, 2020 Share Posted September 29, 2020 (edited) 19 hours ago, Soundscape said: Hi guys, I am looking to upgrade yhe power amp for my Gradient SW 63 subs and looking for suggestions. I am currently running the subs with a Quad 405 Mk2, which is fine a normal listening levels but runs out of steam as the volume goes up. The power amps are fed by a Modwright SWLP hybrid valve preamp that is connected to a Gradient active crossover, which splits the signal and feeds the sub amp frequencies up to 120Hz, with the rest going to a Naksa 100 power amp that drives the ESL63s. I am very happy with the set up overall, the gain structure is a perfect match for the ESLs and sounds amazing even with the volume all the way up to 11 , however at these levels the Quad amp completely loses the plot. 100 Watts gives me plenty of gain, so I'm looking for an amp that is around the 100 watt mark that also possesses the drive and grip to control two 12" drivers per sub at high levels. There is a Bryston 3b in the classifieds that looks the goods, and the price is right, so perhaps I have already answered my question. However being the OCD audiophile like many of us are, I have done some goggling and found various recommendations, ranging from Quad 606 (Gradient recommended), Crown K series (no noisy cooling fans!!) , Alesis Pro amps, Class D amps etc etc. Cosmetics doesn't bother me much and my budget is relatively modest. Perhaps someone with technical knowledge could point me in the right direction (eg volts vs current drive)? Thanks for reading. Over to you! Cheers, Dave Hi Dave The Bryston 3b unfortunately has much higher than needed input sensitivity ie 2v for full output , your quad 405 mk2 features a quarter of that sensitivity - just 500mv for full output. Best not to change the sensitivity matching that is presently about right. When you say it completely loses the plot, may just need a higher quality op amp in its input stage. The opa604 op amp https://www.ti.com/lit/ds/symlink/opa604.pdf ( source from the main electronic suppliers like Farnell, DigiKey. or Mouser) is easy on the pocket to try. But after that you should try a higher current model power amp with the the same 500mv sensitivity Edited September 29, 2020 by stereo coffee Link to comment Share on other sites More sharing options...
Soundscape Posted September 30, 2020 Author Share Posted September 30, 2020 Thanks for the replies gentlemen. You have given me some food for thought. I will try switching the amps to see if that make a difference first. I take the point about the issue probably being the drivers/open baffle setup, thanks for pointing that out. Perhaps I am simply asking too much from the subs? When I crank the volume the bass turns into a muddy distorted mess. And it does seem to be the lowest octaves where the problem lies. I shall experiment some more and take on board the advice given. Cheers! 1 Link to comment Share on other sites More sharing options...
Nada Posted October 21, 2020 Share Posted October 21, 2020 I did some crude modelling for the Gradient "sub" and although the driver used is pretty good for OB it exceeded its Xmax displacement limit under 60Hz at half maximum power. That could cause massive distortion with harmonics contaminating both bass and lower mids. On the other hand it could be the Quad amp losing grip. Its only rated for 100W at 8-ohm whereas the drivers can soak up 220W at 8-ohm and there's two a side. If you Gradient is wired in series that will be a 16-ohm load so the Quad will be stymied at 50W. To test this Id suggest wiring the Gradients in parallel and borrowing a D-class amp. For source use digital input using Foobar tone generator function to work out at what frequencies the issue kicks in. Then use the Foobar 30 band graphic equaliser with music to make a high pass filter that sounds good. With a bit of luck this will sort you out. Only limited music has signifiant energy under 60Hz. Even the lowest electric bass bottom string mainly puts out energy wit the second harmonic at about 82Hz. As long as you dont need dance music, movie rumblings or explosive kick drum you might be very happy. Link to comment Share on other sites More sharing options...
blakey72 Posted October 21, 2020 Share Posted October 21, 2020 Redgum plate amps perhaps: https://www.redgumaudio.com/ Link to comment Share on other sites More sharing options...
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