Hello. After a long time of thinking about ordering and building an ACA I finally plunged half way in and bought one that was already completed.
The ACA has been in my audio chain for about 10 days now and I am thrilled with the results. The improvements to my mids and highs, soundstage, instrument separation, detail and much more are surprising to me. The bottom end is tight with detail but lacking real oomph and overall dynamics are mildly absent.
I also note that to get 80-90 db at my listening position I have the ACA tapped out and I would like to have it running at a lower load. I am currently using very efficient Tekton Double Impact speakers being fed from Roon to a PSAudio DirectStream Jr. to a Emotiva XSP-1 pre-amp and Transparent cabling.
Being an audiophool, I now want to pursue the path to adding some dynamics overall and kick in the low end. In the past I have used big solid state A/B power in the form of older Bryston 4Bs run in mono, NAD 2200, Sansui G9000DB and other sundry A/B power. So I am used to having lots of room on the volume dial and in your face dynamics. I listen to all types of music (especially well recorded music!).
This is where I request some comments/advice from the collective minds herein. I am definitely going to order and build my next piece. But which one to do? Please comment on the three scenarios below or suggest your own.
1. Build an ACA and run in mono to get 15 amps of class A per side. Would this supply enough appreciable power to increase the grip on the bottom end and lift the dynamics while giving headroom on the volume dial?
2. Consider biamping with another ACA or a F-5T v2. If this is a reasonable path how would I control the balance between the amps while biamping. I ask this because I biamped this week with the ACA on the mids/highs and the NAD 2200 on the lows. It did not work well as the volume of the bottom end overran the highs and mids. I tried altering the signal via the preamp and it helped but no, it was not agreeable.
3. Or do I go all out with two F-5T v3 in mono.
Keep in mind that I have built speakers in the past but not amplifiers. I am handy with tools and soldering but no in depth knowledge of caps, etc. I like to learn however.
Thank you in advance for any comments.
The ACA has been in my audio chain for about 10 days now and I am thrilled with the results. The improvements to my mids and highs, soundstage, instrument separation, detail and much more are surprising to me. The bottom end is tight with detail but lacking real oomph and overall dynamics are mildly absent.
I also note that to get 80-90 db at my listening position I have the ACA tapped out and I would like to have it running at a lower load. I am currently using very efficient Tekton Double Impact speakers being fed from Roon to a PSAudio DirectStream Jr. to a Emotiva XSP-1 pre-amp and Transparent cabling.
Being an audiophool, I now want to pursue the path to adding some dynamics overall and kick in the low end. In the past I have used big solid state A/B power in the form of older Bryston 4Bs run in mono, NAD 2200, Sansui G9000DB and other sundry A/B power. So I am used to having lots of room on the volume dial and in your face dynamics. I listen to all types of music (especially well recorded music!).
This is where I request some comments/advice from the collective minds herein. I am definitely going to order and build my next piece. But which one to do? Please comment on the three scenarios below or suggest your own.
1. Build an ACA and run in mono to get 15 amps of class A per side. Would this supply enough appreciable power to increase the grip on the bottom end and lift the dynamics while giving headroom on the volume dial?
2. Consider biamping with another ACA or a F-5T v2. If this is a reasonable path how would I control the balance between the amps while biamping. I ask this because I biamped this week with the ACA on the mids/highs and the NAD 2200 on the lows. It did not work well as the volume of the bottom end overran the highs and mids. I tried altering the signal via the preamp and it helped but no, it was not agreeable.
3. Or do I go all out with two F-5T v3 in mono.
Keep in mind that I have built speakers in the past but not amplifiers. I am handy with tools and soldering but no in depth knowledge of caps, etc. I like to learn however.
Thank you in advance for any comments.
Build a second ACA - If you're a careful person and can follow instructions it's not hard.
In my system the very lowest bass notes come from a subwoofer & plate amp combination but that's taking it's signal from the ACA speaker cables driving the full range drivers. Point being the bass signal from the ACA is very good the limiting factor will be the power. I'm loving it. At the moment I'm using Cambridge DAC magic plus to drive the ACA but have all the parts ordered not for the Korg Nutube buffer. Integrated Valve amp has taken a back seat!
In my system the very lowest bass notes come from a subwoofer & plate amp combination but that's taking it's signal from the ACA speaker cables driving the full range drivers. Point being the bass signal from the ACA is very good the limiting factor will be the power. I'm loving it. At the moment I'm using Cambridge DAC magic plus to drive the ACA but have all the parts ordered not for the Korg Nutube buffer. Integrated Valve amp has taken a back seat!
Well that settles it! Thanks for the input, Mark and Jim. Over to the Aleph J build thread I go...
Worked splendidly well for me. Just took a bit more time to get it built. Being a noob, I was so glad that I started with the ACA first to cut my teeth on. The other advantage was that I had a functioning system with DIY stamped on it. That meant that I didn't have any crazy pressure to build the Aleph J.
I'm planning to gift on the ACA to one of the family, so that it won't be unloved.
Those speakers are incredible. LOVE. Just awesome.
(BTW—not to derail this thread—I had a DAC magic for years...and one day it just died—I replaced it with a Schiit Bifrost and the difference in my system was like letting the sun in a room—I couldn't believe it. I'm sure there's some tech reason for this, probably related to the programming and signal conversion...but I don't know it in detail....)
Hello,
I have the 4 ohm version of the Tekton DI. I thought all of the DIs were 4 ohm but apparently not. Thanks.
4 ohms are challenging for the ACA. Your lack of bass impact might come from that.
That said are these speaker bi-ampable? If so get a second ACA, biamp horizontally. One ACA for left Speaker, one for right.
Thank you mcgillroy for your thoughts. When I ordered my DIs I got the upgrade to be able to biamp. Do you think that another ACA biamped horizontally will suffice? Will it give enough boost to the punch of the low end and the overall dynamics? I was leaning this way in my thoughts but I have the voice in my head asking ‘will it be enough?’.
Have you run an efficient 4 ohm speaker in this mode and been satisfied?
It's complicated.
My own speakers are Markaudio Alpair 6p's in a Needle TQWT enclosure. 4 ohms and about 85db sensitivity. A modified 24V ACA can drive these at satisfactory levels but we are talking small speakers with little cone surface in a 16sqm room at relatively low listening levels. DAC is an Abacus AroioDAC for DAC-Hat for Raspberry which I wholeheartedly recommend.
To my ears this setup sounds really good and people visiting are impressed. But it's not a party system for sure.
So we are talking 50 in2 vs 880 in2 cone area, TQTW vs ported, 85 vs 98db sensitivity etc, etc. Your speakers are in a completely different league and I guess your room is much bigger.
So Apples to Bananas truly.
If you are in overall happy with the ACAs sound horizontal bi-amping is worth a try. Given the low cost of an ACA and their resale value there is little risk in it.
Other options you could consider are the "ACA with Premium Parts" thread here on diyaudio. There you will find some more info on how to build a modified ACA which has a little more grunt for lower impedance speakers.
Or get a bigger amp. F5, F7, M2 - there are many options in Pass-land.
If you got the dough just order a Pass XA25 and don't look back.
Well said. Apples to Bananas is usually the case.
I am happy with the ACA sound and, as I said, I am leaning that way. I was unaware of the thread you mention regarding premium parts so I will definitely have a read of that. I am also unaware of the M2.
This would be a lot simpler if the dough was around for a XA25!
Observations ACA and rated speaker system impedance
These are only my personal observations. I am not sure there is a right or wrong answer to your question with the ACA working into 4 ohms.
You can take a 4 ohm resistor and connect it to the speaker terminals of the ACA. Put a say 20 cycle sine wave at the input of the ACA. Let it come up to operating temp. Measure the output voltage of the ACA at the terminals. Let it run for days on end and come back and measure it again and the amp will be still be blissfully producing the 20 cycle sine wave at the same voltage. So can it drive a 4 ohm load for hours and even days on end. Indeed!
Driving a single driver, rated for 4 ohms. Like a woofer. Is entirely different than driving a speaker system with a passive crossover in between the amplifier output and the speaker's driver input.
A single woofer, measured with conventional speaker driving wisdom may be 4 ohms below the drivers point of resonance. Spike to several dozen ohms at resonance. Then fall back down to around 4 ohms just past resonance and then begins a gradual upward trend as frequency increases. For my example woofer I will say I see a rise to 80 ohms at 35 hertz. Then at 45 cycles it is 3 ohms and it climbs steadily to 12 ohms at the end of the drivers useable frequency of 1700 hertz. In the frequencies I need it to operate in it averages 12 ohms.
So a single driver is only 4 ohms for a very short duration of time and at a specific frequency. Be it an ACA or any other amp. Be it class A, A/B or any of the other classes. It only has to work into 4 ohms for a very short period of time. Unless you are listening at the driver's resonant frequency to a sine wave for hours on end. The amplifier won't see very much 4 ohm action.
I've found that an active crossover, and an independent ACA for each driver (yep - I have 4 of them for a 2 way speaker system) yields outstanding results.
I had not bad, just sort of ho-hum results with 2 ACAs driving the speaker system as it came out of the box utilizing its inbuilt passive crossovers. They were rated at "4 ohms nominal" but when you lump all of the drivers, and coils and caps of the crossover together into one impedance. You find that the constant changing resistance and inductance of the woofer, combined with the constant changing components in the passive crossover cause the overall system to misbehave.
If I am trying to drive any point with all of this babbling. It is that you have to evaluate the entire system. And eliminate as much of anything that sits between the driver terminals and the output of the amp as you can.
Get the active crossover kit from the diy store and get 3 more ACAs and drive the speaker cabinets drivers, independently. I bought my active crossover before the one in the store here came out. So I can't vouch for its performance but some pretty smart people put it together as a kit and I expect it works really well.
If you get it all working and your drivers are efficient. A watt is crazy loud.
Again, my personal observations. If you have drivers that when measured independently (as they all are) can produce high sound pressure levels at 1 watt. You should have outstanding results. If you don't. Adding more power probably is not the answer, unless you are trying to entertain a football stadium.
It is normally the stuff (crossovers) that sit between the amplifier and the driver that cause the amps to misbehave.
Hope this helps!
These are only my personal observations. I am not sure there is a right or wrong answer to your question with the ACA working into 4 ohms.
You can take a 4 ohm resistor and connect it to the speaker terminals of the ACA. Put a say 20 cycle sine wave at the input of the ACA. Let it come up to operating temp. Measure the output voltage of the ACA at the terminals. Let it run for days on end and come back and measure it again and the amp will be still be blissfully producing the 20 cycle sine wave at the same voltage. So can it drive a 4 ohm load for hours and even days on end. Indeed!
Driving a single driver, rated for 4 ohms. Like a woofer. Is entirely different than driving a speaker system with a passive crossover in between the amplifier output and the speaker's driver input.
A single woofer, measured with conventional speaker driving wisdom may be 4 ohms below the drivers point of resonance. Spike to several dozen ohms at resonance. Then fall back down to around 4 ohms just past resonance and then begins a gradual upward trend as frequency increases. For my example woofer I will say I see a rise to 80 ohms at 35 hertz. Then at 45 cycles it is 3 ohms and it climbs steadily to 12 ohms at the end of the drivers useable frequency of 1700 hertz. In the frequencies I need it to operate in it averages 12 ohms.
So a single driver is only 4 ohms for a very short duration of time and at a specific frequency. Be it an ACA or any other amp. Be it class A, A/B or any of the other classes. It only has to work into 4 ohms for a very short period of time. Unless you are listening at the driver's resonant frequency to a sine wave for hours on end. The amplifier won't see very much 4 ohm action.
I've found that an active crossover, and an independent ACA for each driver (yep - I have 4 of them for a 2 way speaker system) yields outstanding results.
I had not bad, just sort of ho-hum results with 2 ACAs driving the speaker system as it came out of the box utilizing its inbuilt passive crossovers. They were rated at "4 ohms nominal" but when you lump all of the drivers, and coils and caps of the crossover together into one impedance. You find that the constant changing resistance and inductance of the woofer, combined with the constant changing components in the passive crossover cause the overall system to misbehave.
If I am trying to drive any point with all of this babbling. It is that you have to evaluate the entire system. And eliminate as much of anything that sits between the driver terminals and the output of the amp as you can.
Get the active crossover kit from the diy store and get 3 more ACAs and drive the speaker cabinets drivers, independently. I bought my active crossover before the one in the store here came out. So I can't vouch for its performance but some pretty smart people put it together as a kit and I expect it works really well.
If you get it all working and your drivers are efficient. A watt is crazy loud.
Again, my personal observations. If you have drivers that when measured independently (as they all are) can produce high sound pressure levels at 1 watt. You should have outstanding results. If you don't. Adding more power probably is not the answer, unless you are trying to entertain a football stadium.
It is normally the stuff (crossovers) that sit between the amplifier and the driver that cause the amps to misbehave.
Hope this helps!
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Hi Tjw59,
Thank you for your thoughts. They certainly gave me some paths to follow and research. I was intrigued by your discussion of the ohm reading at different frequencies. I am unaware of that but will set aside time on the weekend to absorb the ideas.
I like your suggestion of the 4 ACA. I was already mulling that over but not with an active equalizer. I was going to run them through the existing passive system already set up by the manufacturer of the speaker. I like your idea to make as clean a path between amp and driver as possible.
I will look at the active crossover you suggest but I will start with another ACA and see where that gets me.
Your thoughts help to fill in gaps in my knowledge. Thanks again.