What to upgrade - power amp or add sub

carl425

Novice Member
My primary music system consists of a PC, Schiit Modi & Vali, Adcom GFA 535 and a pair of Elac Unifi Reference speakers. I'm feeling a little short on bass. The prime suspect is the Adcom since it's on the edge of the power the Elacs need. I'm thinking I can optionally add a subwoofer and the Adcom would suffice driving only frequencies above 80 hz. This would also be cheaper than a new amp as I've got my eye on the Schiit Vidar. The room is only 10x13 so I'm considering the Emotiva SE8.

Another opportunity is the HT system which is in a 13x16 room and has a Definitive Technology Supercube II. I could move it to the music system and upgrade the HT sub with something new.

What are your opinions?
 
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dogfonos

Well-known Member
First thoughts are to add the DT Supercube II into the music system as a test to hear how well it integrates with the Elac main speakers and also to judge the system's overall sound quality as both the DT and Emotiva subs use passive radiator(s) and therefore may have some common sound characteristics related to the design.

Adding a sub rather than purchasing a higher powered amp (to drive the Elac speakers) will also give the benefit of active bass - any speaker actively driven is a big plus in my book, especially at the bass end. And you're correct in saying that a sub would relieve the Elacs from reproducing deep bass - another big plus, IMO. The only potential issue with adding a sub to the setup may be the sonic integration of the subwoofer with the Elac speakers, hence my suggestion of trying out your DT sub with the Elacs before purchasing another sub.

Whilst I don't use a subwoofer, in my music system, my personal preference would be for a sealed box sub without passive radiator(s) although for home theatre, I would either use a large sealed box sub (possibly multiples) or smaller ported/passive radiator designs. True sealed box bass has a great time-domain response so will likely sound that bit tighter and better defined than passive radiator and ported speaker bass. If you opt for a sealed box sub, consider ones with a 10" driver for your room size for music.
 

artograffi

Novice Member
My primary music system consists of a PC, Schiit Modi & Vali, Adcom GFA 535 and a pair of Elac Unifi Reference speakers. I'm feeling a little short on bass. The prime suspect is the Adcom since it's on the edge of the power the Elacs need. I'm thinking I can optionally add a subwoofer and the Adcom would suffice driving only frequencies above 80 hz. This would also be cheaper than a new amp as I've got my eye on the Schiit Vidar. The room is only 10x13 so I'm considering the Emotiva SE8.

Another opportunity is the HT system which is in a 13x16 room and has a Definitive Technology Supercube II. I could move it to the music system and upgrade the HT sub with something new.

What are your opinions?
I have a similar problem. I have a very old but amazing pair of huge speakers designed as prototypes . The y two halves. The bass is no longer good whereas the top half from about 200hz upwards is still superb. So I’m thinking if a subwoofer. I have a CAT tube preamp, Vincent monoblocs , am Accuphase CD player which I’m using just as a
DAC as it won’t play CDs anymore plus a Stratosphere turntable , Graham arm and Transfiguration pickup. Do I need a passive or active sub and what is the best way to connect or do I need two subs to take over the bass from each speaker? Sorry this is long. I’m new here so please forgive me!
 

dogfonos

Well-known Member
Just to check my understanding of your situation…

Each channel of the current speakers consists of two physically separate boxes and the crossover frequency between the two boxes (i.e. “bass box” and the “higher range box”) is about 200Hz? And the performance of the bass boxes has deteriorated? I take it there is currently a passive crossover that divides the frequency range between the “bass boxes” and the “higher range” speakers?

If this is the case then, in theory, you could replace both bass boxes with either one or two subwoofers as you suggest. There are very few domestically orientated (i.e. of reasonable size and appearance) passive subs on the market. Even if you could get hold of a pair, the subs sensitivity needs to be considered as it may not match the sensitivity of your “higher range” speakers. Active bass is superior to passive bass anyway so, if you’re determined to keep the old speakers going, an active sub (or subs) would likely be the better option to replace the “bass boxes”. There are, however, a couple of issues to address with this approach.

Firstly, most subs are designed to reproduce frequencies from around 100Hz downwards. Many subs don’t have a good frequency response up to 200Hz, though it’s possible a few do. So you need a sub that has a flat-ish frequency response to 200Hz, preferably a little beyond that too. The crossover frequency control (i.e. low-pass filter) of subs I’m familiar with have a maximum setting of around 120 – 150Hz, which falls short of the 200Hz+ required to match your “higher range” speakers. I think this could be a big stumbling block. And how sure are you that the crossover point is 200Hz - could it be higher stll?

Connecting the active sub into the existing setup needs consideration because, as I understand it, the “higher range” speakers aren’t intended to accept signals below about 200Hz. Now, if the existing crossover can be retained (or at least the high-pass filter section that feeds the “higher range” speakers) then the “higher range” speakers should remain protected. A common way of connecting one or two active subs to a stereo amplifier (or two mono amps) that doesn’t have a dedicated subwoofer outlet is to connect the sub to the amp’s speaker terminals (i.e. a high level sub connection). With this connection method, the active sub doesn’t draw appreciable power from the amp.

Good luck in finding a sub designed for frequencies up to 200Hz+. A better solution may be to get your existing “bass boxes” fixed. I imagine the “bass box” problem is with either the drivers themselves or the crossover. Companies like Wilmslow Audio and Falcon Acoustics can carry out repairs, or suggest replacements, for both.
 

artograffi

Novice Member
Just to check my understanding of your situation…

Each channel of the current speakers consists of two physically separate boxes and the crossover frequency between the two boxes (i.e. “bass box” and the “higher range box”) is about 200Hz? And the performance of the bass boxes has deteriorated? I take it there is currently a passive crossover that divides the frequency range between the “bass boxes” and the “higher range” speakers?

If this is the case then, in theory, you could replace both bass boxes with either one or two subwoofers as you suggest. There are very few domestically orientated (i.e. of reasonable size and appearance) passive subs on the market. Even if you could get hold of a pair, the subs sensitivity needs to be considered as it may not match the sensitivity of your “higher range” speakers. Active bass is superior to passive bass anyway so, if you’re determined to keep the old speakers going, an active sub (or subs) would likely be the better option to replace the “bass boxes”. There are, however, a couple of issues to address with this approach.

Firstly, most subs are designed to reproduce frequencies from around 100Hz downwards. Many subs don’t have a good frequency response up to 200Hz, though it’s possible a few do. So you need a sub that has a flat-ish frequency response to 200Hz, preferably a little beyond that too. The crossover frequency control (i.e. low-pass filter) of subs I’m familiar with have a maximum setting of around 120 – 150Hz, which falls short of the 200Hz+ required to match your “higher range” speakers. I think this could be a big stumbling block. And how sure are you that the crossover point is 200Hz - could it be higher stll?

Connecting the active sub into the existing setup needs consideration because, as I understand it, the “higher range” speakers aren’t intended to accept signals below about 200Hz. Now, if the existing crossover can be retained (or at least the high-pass filter section that feeds the “higher range” speakers) then the “higher range” speakers should remain protected. A common way of connecting one or two active subs to a stereo amplifier (or two mono amps) that doesn’t have a dedicated subwoofer outlet is to connect the sub to the amp’s speaker terminals (i.e. a high level sub connection). With this connection method, the active sub doesn’t draw appreciable power from the amp.

Good luck in finding a sub designed for frequencies up to 200Hz+. A better solution may be to get your existing “bass boxes” fixed. I imagine the “bass box” problem is with either the drivers themselves or the crossover. Companies like Wilmslow Audio and Falcon Acoustics can carry out repairs, or suggest replacements, for both.
Thanks fir all that. I’m guessing about the speaker crossing over at 200 and it could well be 100 or lower. Because they are huge snd very heavy moving the bass boxes would be a real problem. It would be lovely if I could just replace the old drivers in the bass boxes but getting someone to do it would be incredibly difficult.
I agree active subs would be better if I go down that route. I don’t think the bass boxes go down further than 40hz if that.two actives would be easiest I guess. To replace these speakers completely would cost a fortune which I don’t have. Ok still enjoy listening to the system apart from the bas specially using the turntable which is my best source.
 

dogfonos

Well-known Member
’m guessing about the speaker crossing over at 200 and it could well be 100 or lower.

Even without proper test gear, you can determine the crossover frequency between bass box and higher range box by using sinewave test tones/signals. How you do this depends on sources you can utilize. Sinewave test signals in 10Hz steps from around 20Hz up to the crossover frequency would work fine. I don't know to what extent the bass boxes are compromised but, if they were working normally, when the volume coming from the bass box and the higher range box are equal, that's the crossover frequency.

I don't know if there are domestically orientated active subs that can be set to play above about 120 - 150Hz so if the crossover frequency of your current speakers is higher than that...happy hunting.

It would be lovely if I could just replace the old drivers in the bass boxes but getting someone to do it would be incredibly difficult.
Could you DIY - assuming replacement drivers are available (Wilmslow Audio or Falcon Acoustics would advise)? Most speakers are designed so that the drivers are pretty easy to remove, though the problem here could be a suitable replacement.
 

artograffi

Novice Member
Even without proper test gear, you can determine the crossover frequency between bass box and higher range box by using sinewave test tones/signals. How you do this depends on sources you can utilize. Sinewave test signals in 10Hz steps from around 20Hz up to the crossover frequency would work fine. I don't know to what extent the bass boxes are compromised but, if they were working normally, when the volume coming from the bass box and the higher range box are equal, that's the crossover frequency.

I don't know if there are domestically orientated active subs that can be set to play above about 120 - 150Hz so if the crossover frequency of your current speakers is higher than that...happy hunting.


Could you DIY - assuming replacement drivers are available (Wilmslow Audio or Falcon Acoustics would advise)? Most speakers are designed so that the drivers are pretty easy to remove, though the problem here could be a suitable replacement.
I’m not good at diy. I’m a bit disabled with a bad back. The drivers are Kef 12. I dint mind if the subs aren’t very domestically acceptable considering the speakers are anything but.
image.jpg
Incidentally I’m 75 and a female lol.
 

dogfonos

Well-known Member
Wow! Amazing speaker design. Judging by the size, they look like they were made for an extremely large room or small hall. What is your room size/floor area? You have some very high-end gear which deserves great speakers though I can't predict the sort of sound you're currently getting (in a typical domestic sized room, I'm assuming?) from these amazing-looking speakers. Looking at the drive unit layout, I'd be surprised if they gave a decent stereo image or accurate soundstage but I would expect them to have a great sense of scale, impact and authority.

One thought strikes me: the cabinet finish of the bass box doesn't match the higher range box. And it appears to be a little wider than the higher range box too. Was this bass box added at a later date? Was there originally another bass box or did the speaker originally consist solely of the higher range box? Reason I ask is because at least one of the drivers, possibly two, in the higher range box looks to be an 8" bass driver (or at the very least, a 8" bass/midrange driver). I wonder if the higher range box is actually a full range speaker in it's own right and that the bass box was added later to provide a bit more depth/welly (to use a technical term!). If that's the case, then the 8" drivers in the higher range box may not be fed through a high pass crossover and so is fed a full range signal from the amp which means the higher range box will likely reproduce bass - at a guess, to below 100Hz - so a typical hifi active subwoofer set to reproduce frequencies below around 100 Hz should work just fine in combination with the higher range box.

I assume you have two sets of these speakers (i.e. a stereo pair)?

Clearly, if you love the sound of these speakers then it's best to consider a repair because it will be impossible for anyone to predict their sound in your listening room/space and therefore impossible to suggest similar sounding modern alternatives. Unless the 8" drivers in the higher range box are fed a full range signal, then replacing the bass box with a sub, of any kind, is hit and miss due to the unknown crossover frequency of your speakers and the inability of all quality subs that I'm aware of (though I'm not particularly familiar with the hifi/home theatre subwoofer market) to handle frequencies above about 120 - 150Hz.

This 12" KEF bass driver in the bass box is a late 1970's design called the KEF B300. A quick Google says it was used in the KEF 105.2 and CS9 speakers. I haven't checked but I'd imagine a suitable replacement would be available. Only thing is, the bass section of the existing crossover might be faulty so replacing bass drivers may not correct the problem.

I appreciate that shipping (two?) large bass boxes off to a specialist repairer is a pain and will cost a bit, but I would confidently say that the aforementioned Wilmslow Audio or Falcon Acoustics will effect a solution. No harm in giving them a call to hear what they suggest. Alternatively, there's a consumer electronics repairer in Herne Bay (R J Electronics, Herne Bay | Tv Repairs - Yell) who may be able to help. This is not a personal recommendation of R J Electronics as I've never used them. Good luck with your quest.
 

artograffi

Novice Member
Wow! Amazing speaker design. Judging by the size, they look like they were made for an extremely large room or small hall. What is your room size/floor area? You have some very high-end gear which deserves great speakers though I can't predict the sort of sound you're currently getting (in a typical domestic sized room, I'm assuming?) from these amazing-looking speakers. Looking at the drive unit layout, I'd be surprised if they gave a decent stereo image or accurate soundstage but I would expect them to have a great sense of scale, impact and authority.

One thought strikes me: the cabinet finish of the bass box doesn't match the higher range box. And it appears to be a little wider than the higher range box too. Was this bass box added at a later date? Was there originally another bass box or did the speaker originally consist solely of the higher range box? Reason I ask is because at least one of the drivers, possibly two, in the higher range box looks to be an 8" bass driver (or at the very least, a 8" bass/midrange driver). I wonder if the higher range box is actually a full range speaker in it's own right and that the bass box was added later to provide a bit more depth/welly (to use a technical term!). If that's the case, then the 8" drivers in the higher range box may not be fed through a high pass crossover and so is fed a full range signal from the amp which means the higher range box will likely reproduce bass - at a guess, to below 100Hz - so a typical hifi active subwoofer set to reproduce frequencies below around 100 Hz should work just fine in combination with the higher range box.

I assume you have two sets of these speakers (i.e. a stereo pair)?

Clearly, if you love the sound of these speakers then it's best to consider a repair because it will be impossible for anyone to predict their sound in your listening room/space and therefore impossible to suggest similar sounding modern alternatives. Unless the 8" drivers in the higher range box are fed a full range signal, then replacing the bass box with a sub, of any kind, is hit and miss due to the unknown crossover frequency of your speakers and the inability of all quality subs that I'm aware of (though I'm not particularly familiar with the hifi/home theatre subwoofer market) to handle frequencies above about 120 - 150Hz.

This 12" KEF bass driver in the bass box is a late 1970's design called the KEF B300. A quick Google says it was used in the KEF 105.2 and CS9 speakers. I haven't checked but I'd imagine a suitable replacement would be available. Only thing is, the bass section of the existing crossover might be faulty so replacing bass drivers may not correct the problem.

I appreciate that shipping (two?) large bass boxes off to a specialist repairer is a pain and will cost a bit, but I would confidently say that the aforementioned Wilmslow Audio or Falcon Acoustics will effect a solution. No harm in giving them a call to hear what they suggest. Alternatively, there's a consumer electronics repairer in Herne Bay (R J Electronics, Herne Bay | Tv Repairs - Yell) who may be able to help. This is not a personal recommendation of R J Electronics as I've never used them. Good luck with your quest.
These speakers were prototypes hence not pretty with nice veneer like the proper manufactured ones. They do give a surprising good stereo image. The great thing about them is there lack of colours toon. I’ve just moved to a much smaller place and my room is only 17’x about 13’ so rather small for my speakers but they still sound good.the man who designed them is a very good friend but he’s quite old ( even older than me ) and I’d never get them moved .
The 8” is a bass and low mud. Definitely not full range. They were all fine together snd the bass boxes and covered in Formica lol. My friend often said he was annoyed that mine sounded better than his.
Only one bass driver is faulty and buzzes on loud signals . They don’t go very low and my room isn’t ideal either but I really do fancy a sub and to get those low notes that give me that thrill.
 

artograffi

Novice Member
First thoughts are to add the DT Supercube II into the music system as a test to hear how well it integrates with the Elac main speakers and also to judge the system's overall sound quality as both the DT and Emotiva subs use passive radiator(s) and therefore may have some common sound characteristics related to the design.

Adding a sub rather than purchasing a higher powered amp (to drive the Elac speakers) will also give the benefit of active bass - any speaker actively driven is a big plus in my book, especially at the bass end. And you're correct in saying that a sub would relieve the Elacs from reproducing deep bass - another big plus, IMO. The only potential issue with adding a sub to the setup may be the sonic integration of the subwoofer with the Elac speakers, hence my suggestion of trying out your DT sub with the Elacs before purchasing another sub.

Whilst I don't use a subwoofer, in my music system, my personal preference would be for a sealed box sub without passive radiator(s) although for home theatre, I would either use a large sealed box sub (possibly multiples) or smaller ported/passive radiator designs. True sealed box bass has a great time-domain response so will likely sound that bit tighter and better defined than passive radiator and ported speaker bass. If you opt for a sealed box sub, consider ones with a 10" driver for your room size for music.
I just want to apologise for my phone doing weird and stupid spelling like mud instead of mid and colourstion instead of the rubbish it put. Hopefully you can translate what I really meant to say. Lol
 

dogfonos

Well-known Member
my room is only 17’x about 13’ so rather small for my speakers

I have to say that's some understatement! Still, the main point is that you enjoy their sound and wish to keep them - and add a subwoofer to the system. Setting aside my reservations, as detailed in earlier posts, about the best value sub for music listening in the UK is probably the BK Electronics P12-300SB which is available in Forward Firing (FF) or Downward Firing (DF) versions:


There are several glowing reviews of this sub.

BK Electronics also sell a version of this sub with added passive radiator (P12-300SB-PR) for extra oomph. This sub also gets excellent reviews and, although it would work well with music systems, it is arguably better suited to TV and film:


Both the BK subs mentioned connect to the amplifier's speaker terminals with bare wire, although I dare say one could add other connectors to suit the amp's terminals. Both subs would work well and give all the bass you need in a 20 - 25sqm room. Of course, alternative subs are available. Avforums has a dedicated subwoofer forum which may be of interest:

 

artograffi

Novice Member
I have to say that's some understatement! Still, the main point is that you enjoy their sound and wish to keep them - and add a subwoofer to the system. Setting aside my reservations, as detailed in earlier posts, about the best value sub for music listening in the UK is probably the BK Electronics P12-300SB which is available in Forward Firing (FF) or Downward Firing (DF) versions:


There are several glowing reviews of this sub.

BK Electronics also sell a version of this sub with added passive radiator (P12-300SB-PR) for extra oomph. This sub also gets excellent reviews and, although it would work well with music systems, it is arguably better suited to TV and film:


Both the BK subs mentioned connect to the amplifier's speaker terminals with bare wire, although I dare say one could add other connectors to suit the amp's terminals. Both subs would work well and give all the bass you need in a 20 - 25sqm room. Of course, alternative subs are available. Avforums has a dedicated subwoofer forum which may be of interest:

Thank you for yourrrply and interest. After a bit of research I also came to the conclusion that a Bk sun was the way to go and you have just confirmed how good they are. I do scour ebay as can rarely afford full price.
So would I need ordinary speaker cable to connect the sub to the power amp?
I have to say that's some understatement! Still, the main point is that you enjoy their sound and wish to keep them - and add a subwoofer to the system. Setting aside my reservations, as detailed in earlier posts, about the best value sub for music listening in the UK is probably the BK Electronics P12-300SB which is available in Forward Firing (FF) or Downward Firing (DF) versions:


There are several glowing reviews of this sub.

BK Electronics also sell a version of this sub with added passive radiator (P12-300SB-PR) for extra oomph. This sub also gets excellent reviews and, although it would work well with music systems, it is arguably better suited to TV and film:


Both the BK subs mentioned connect to the amplifier's speaker terminals with bare wire, although I dare say one could add other connectors to suit the amp's terminals. Both subs would work well and give all the bass you need in a 20 - 25sqm room. Of course, alternative subs are available. Avforums has a dedicated subwoofer forum which may be of interest:

thank you. I have decided that BK is the brand to go with for a subwoofer. I need to scour eBay as I’m not well off lol. Please can I ask wide I just get ordinate speaker cable to go from the sub into the power amps? The power amps are just next to each speaker so they are a fair distance apart. I really know nothing about subs so need any advice I can get. It will all depend whether I can get the finance. It could take a while but I will get one hopefully one day. Thank for the link to the info about subs. I’ll definitely read it.
I’m a bit vague tonight I’m afraid so sorry if this lacks cohesion!
 

dogfonos

Well-known Member
After a bit of research I also came to the conclusion that a Bk sun was the way to go and you have just confirmed how good they are. I do scour ebay as can rarely afford full price.

...then you may have noticed that BK Electronics sell their "Grade B" stock under the name Colosussxb:


By all accounts, imperfections on Grade B subwoofers sold by Colosussxb are barely noticeable, though I have no personal experience of this.

So would I need ordinary speaker cable to connect the sub to the power amp?

BK Electronics/Colosussxb can supply a suitable cable with three conductors to connect their subwoofers to your amplifiers. This is it:


I'm unclear if this cable is provided with the sub or an optional extra.

At the subwoofer end, the cable terminates in a Neutrik connection that plugs into the sub whilst at the other end, there are three bare wire conductors. Two conductors connect to the speaker terminals of one power amp and the third conductor connects to the other power amp. However, because your power amps are a distance apart, one of the three conductors in the supplied cable will probably need to be extended to reach the furthest power amp. Note that your power amps do not power the connected subwoofer as such, the sub simply takes the music signal and uses its own in-built amplifier to power the subwoofer driver (if that makes sense), so the sub places no extra load on your amps. This means that any thin copper wire can be used to extend one of the conductors to reach the furthest amp - it certainly doesn't need to be thick speaker cable, that would be pointless overkill. Any thin copper insulated wire would do.
 

artograffi

Novice Member
...then you may have noticed that BK Electronics sell their "Grade B" stock under the name Colosussxb:


By all accounts, imperfections on Grade B subwoofers sold by Colosussxb are barely noticeable, though I have no personal experience of this.



BK Electronics/Colosussxb can supply a suitable cable with three conductors to connect their subwoofers to your amplifiers. This is it:


I'm unclear if this cable is provided with the sub or an optional extra.

At the subwoofer end, the cable terminates in a Neutrik connection that plugs into the sub whilst at the other end, there are three bare wire conductors. Two conductors connect to the speaker terminals of one power amp and the third conductor connects to the other power amp. However, because your power amps are a distance apart, one of the three conductors in the supplied cable will probably need to be extended to reach the furthest power amp. Note that your power amps do not power the connected subwoofer as such, the sub simply takes the music signal and uses its own in-built amplifier to power the subwoofer driver (if that makes sense), so the sub places no extra load on your amps. This means that any thin copper wire can be used to extend one of the conductors to reach the furthest amp - it certainly doesn't need to be thick speaker cable, that would be pointless overkill. Any thin copper insulated wire would do.
Hi thank fir your reply. No I didn’t know about Bk grade b stock. What you told me about the speaker cable is very helpful. Which connector do you put the third strand? Red or black? Or does it not matter?
I understand about the sun having it’s own amp. So it will not be taking any power from my monoblocs. Is what you suggest better than connecting to the preamp.
The other thing I was wondering is I had two subs so basically taking over from the. Bass boxes then I presume each sub would connect to each power amp. All this is dependant on me getting a sub or two 😂 but in the end I’m pretty determined. I am guessing I can balance the sound with the various knobs on the subwoofer.
 

dogfonos

Well-known Member
Which connector do you put the third strand? Red or black? Or does it not matter?

The BK Electronics website explains the "high-level" connection here (on page 3):


This diagram is for a different BK sub but it has the same input layout as BK's other subs.
I don't know how you would wire two subs up to your monoblock amps using the sub's high-level input. Perhaps a forum user who has done this could advise?

Is what you suggest better than connecting to the preamp.

Don't know if one is better than the other. I'm not familiar with CAT preamps so I wouldn't like to second guess.

I am guessing I can balance the sound with the various knobs on the subwoofer.

Yes, the sound could be balanced using the subs' controls. For your room, two subs would be massive overkill for music listening but then most folk with a room your size would be listening on a pair of two-way standmount speaker with a single 6.5" bass/mid driver per cabinet (or possibly an 8" bass/mid driver per cabinet should a bassier balance be preferred).

In the back of my mind, I'm still concerned that replacing the existing KEF bass boxes with one or two subs might leave a hole in the frequency response because the subs won't produce frequencies high enough to "mate up" with your main speakers. Unless you can be certain that the main speakers reproduce sounds as low as 100 - 120Hz, then you're taking quite a risk.
 

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