Gains of (active) bi-/tri-/quad-amping

[nicoleise]

Hi guys,


First post, hope it's in the right place. I'm in the process of building a 9.4.4 living room home cinema system, and prioritize good 2ch performance for listening to music the most. I'll be using DSP regardless and amplification will be class D. So bi-amping in this sense will be through seperate boxes with separate PSUs, not assigning an extra channel in an AVR.

My LR speakers (JBL Ti10k) are difficult to drive, they have relatively low sensitivity, their impedance is low and their power rating is 400W. They are quad-amp-able four-way, five driver speakers and the terminals are under the speaker, so planning in due time seems sensible for hidden wiring in the build.


In researching this, what I read about bi-amping becomes contradictory in my scenario.

I read that using an amp channel for "just" a tweeter is a waste since this driver isn't demanding at all. This makes sense but also entails more than one driver sharing an amp channel and thus entails leaving the crossover network in place.

But I also read that active is the way to go amongst others to be rid of the crossover network to avoid the losses herein and to allow the amp to "see" the driver directly, as well as to be able to do individual crossover frequencies and time alignment. This also seems to make sense, but its another direction.

I get that I could technically leave the crossover network in place and just bypass the drivers I'd use active bi-amping for.


I get that it's not really possible to quantify how much quality will improve if any, but I'd like to ask your advice - perhaps in a "what would you do/recommend"-way?


Thanks and KR,
Nicolai

 

[AcuDefTechGuy]

These are passive speakers with internal crossovers. They have dual 8” woofers.

I would just use a 100--300 WPC amp and not do any kind of b-amp.

Usually I think the only drivers worth bi-amp are the big woofers that are dual 10”-12”. I don’t think dual 8” woofers are worth bi-amp.

 

[lovinthehd]

The specs I found indicated it's rated 6 ohm and 91dB sensitivity so don't seem particularly hard to drive. Is it worth 8 amps and the crossovers? I'd just use a good powerful amp rather than go that route....

ps Interesting looking speakers, hadn't seen those JBLs before....

 

[TLS Guy]

Hi guys,


First post, hope it's in the right place. I'm in the process of building a 9.4.4 living room home cinema system, and prioritize good 2ch performance for listening to music the most. I'll be using DSP regardless and amplification will be class D. So bi-amping in this sense will be through seperate boxes with separate PSUs, not assigning an extra channel in an AVR.

My LR speakers (JBL Ti10k) are difficult to drive, they have relatively low sensitivity, their impedance is low and their power rating is 400W. They are quad-amp-able four-way, five driver speakers and the terminals are under the speaker, so planning in due time seems sensible for hidden wiring in the build.


In researching this, what I read about bi-amping becomes contradictory in my scenario.

I read that using an amp channel for "just" a tweeter is a waste since this driver isn't demanding at all. This makes sense but also entails more than one driver sharing an amp channel and thus entails leaving the crossover network in place.

But I also read that active is the way to go amongst others to be rid of the crossover network to avoid the losses herein and to allow the amp to "see" the driver directly, as well as to be able to do individual crossover frequencies and time alignment. This also seems to make sense, but its another direction.

I get that I could technically leave the crossover network in place and just bypass the drivers I'd use active bi-amping for.


I get that it's not really possible to quantify how much quality will improve if any, but I'd like to ask your advice - perhaps in a "what would you do/recommend"-way?


Thanks and KR,
Nicolai

You have missed a step. You have to replicate the passive crossovers with active ones ahead of the amps. I doubt you know how to design and build that. But if you do there are advantages. But you will really have to know what you are doing. Unless you do this perfectly, you will have a huge quality downgrade and likely blow some drivers.

Here is the passive crossover circuit you would have to replicate as an active circuit.

 

[nicoleise]

Thanks for the replies so far.

Usually I think the only drivers worth bi-amp are the big woofers that are dual 10”-12”. I don’t think dual 8” woofers are worth bi-amp.

If I consider before/after active bi-amping, what strikes me as the difference is essentially removing the crossover from the speaker. While obviously there's some lower limit to feasibility (as with the tweeter example in my OP), I'd imagine the choice riding on the crossover network rather than the size of the woofers.

On the other hand, I recognize that (as a general rule) larger drivers may require more power and crossover parts that may be more lossy.

Is this the reasoning, it would you care to elaborate or point me to something (I'm not lazy, don't mind reading on my own, just don't know where to look for more on that)?

The specs I found indicated it's rated 6 ohm and 91dB sensitivity so don't seem particularly hard to drive. Is it worth 8 amps and the crossovers?

Precisely the question on my mind, and also why I imagine some hybrid like bi-amping or tri-amping if at all.

But the specs for these speakers are oddly misguided. For example there are two sets of specs, both on JBLs letterhead, where the sensitivity and crossover points vary.

In addition, a printed review I now can't (re)find suggested desparity between the specs and reality, and measured as low as 2-point-something ohms impedance. I believe he quoted a sensitivity if 86 dB.

While I haven't yet measured these myself, I'll suggest that the sensitivity is not 91 dB and the old Harman Kardon AVR630 they are temporarily hooked up to seems to "run out of tap" much sooner than other speakers I have had hooked up to it.

But whether the "fix" for this and the best sound quality barring the point if diminishing returns is through one or more amps per speaker, I really can't tell.

You have missed a step. You have to replicate the passive crossovers with active ones ahead of the amps. I doubt you know how to design and build that. But if you do there are advantages. But you will really have to know what you are doing. Unless you do this perfectly, you will have a huge quality downgrade and likely blow some drivers.

Here is the passive crossover circuit you would have to replicate as an active circuit.

I don't know of any other way to do active bi-amping, so I thought it was pretty much implicit in "active bi-amping"? (Asking if I'm overlooking an alternative)

Your link doesn't work for me, but I know the crossover network schematic.

If not doing full quad amping, which seems excessive to me, but rather some "hybrid bi-amping ", I wouldn't have to recreate the entire network sonically though, "just" fx the "handoff"/crossover points to where the crossover takes over.

For now, just trying to establish what might be considered "worthwhile" sonically.

 

[TLS Guy]

Thanks for the replies so far.



If I consider before/after active bi-amping, what strikes me as the difference is essentially removing the crossover from the speaker. While obviously there's some lower limit to feasibility (as with the tweeter example in my OP), I'd imagine the choice riding on the crossover network rather than the size of the woofers.

On the other hand, I recognize that (as a general rule) larger drivers may require more power and crossover parts that may be more lossy.

Is this the reasoning, it would you care to elaborate or point me to something (I'm not lazy, don't mind reading on my own, just don't know where to look for more on that)?



Precisely the question on my mind, and also why I imagine some hybrid like bi-amping or tri-amping if at all.

But the specs for these speakers are oddly misguided. For example there are two sets of specs, both on JBLs letterhead, where the sensitivity and crossover points vary.

In addition, a printed review I now can't (re)find suggested desparity between the specs and reality, and measured as low as 2-point-something ohms impedance. I believe he quoted a sensitivity if 86 dB.

While I haven't yet measured these myself, I'll suggest that the sensitivity is not 91 dB and the old Harman Kardon AVR630 they are temporarily hooked up to seems to "run out of tap" much sooner than other speakers I have had hooked up to it.

But whether the "fix" for this and the best sound quality barring the point if diminishing returns is through one or more amps per speaker, I really can't tell.



I don't know of any other way to do active bi-amping, so I thought it was pretty much implicit in "active bi-amping"? (Asking if I'm overlooking an alternative)

Your link doesn't work for me, but I know the crossover network schematic.

If not doing full quad amping, which seems excessive to me, but rather some "hybrid bi-amping ", I wouldn't have to recreate the entire network sonically though, "just" fx the "handoff"/crossover points to where the crossover takes over.

For now, just trying to establish what might be considered "worthwhile" sonically.

It is not just the crossover points you have to get right, but the slopes also. Both have to be exact. It is clear to me that this project is beyond your current level of competence, and so you what you will do, will be a massive downgrade. So you would need an intensive period of study. The problem is that to design this you are getting to university level study.

Remember you will not only be designing the crossover, but the power supplies, and making sure they are safe and won't burn the house down.

This is also reverse engineering and actually tougher than starting from scratch. If you want active speakers, then select suitable drivers, design the cabinets, drivers, and design the optimal crossovers and select the appropriate power amps. Reverse engineering is always the most challenging.

If you want active speakers, then buy or build them. There are active speakers about.

 

[highfigh]

This link shows the specs and crossover schematic with 200Hz, 1200Hz and 3500Hz. It also shows sensitivity at 90dB/W/M and 40Hz-22KHz ±2dB response and amplification of 50-400W recommended amplifier power.

file:///C:/Users/USER/Downloads/hfe_jbl_ti10k_technical_en.pdf

 

[highfigh]

Thanks for the replies so far.



If I consider before/after active bi-amping, what strikes me as the difference is essentially removing the crossover from the speaker. While obviously there's some lower limit to feasibility (as with the tweeter example in my OP), I'd imagine the choice riding on the crossover network rather than the size of the woofers.

On the other hand, I recognize that (as a general rule) larger drivers may require more power and crossover parts that may be more lossy.

Is this the reasoning, it would you care to elaborate or point me to something (I'm not lazy, don't mind reading on my own, just don't know where to look for more on that)?



Precisely the question on my mind, and also why I imagine some hybrid like bi-amping or tri-amping if at all.

But the specs for these speakers are oddly misguided. For example there are two sets of specs, both on JBLs letterhead, where the sensitivity and crossover points vary.

In addition, a printed review I now can't (re)find suggested desparity between the specs and reality, and measured as low as 2-point-something ohms impedance. I believe he quoted a sensitivity if 86 dB.

While I haven't yet measured these myself, I'll suggest that the sensitivity is not 91 dB and the old Harman Kardon AVR630 they are temporarily hooked up to seems to "run out of tap" much sooner than other speakers I have had hooked up to it.

But whether the "fix" for this and the best sound quality barring the point if diminishing returns is through one or more amps per speaker, I really can't tell.



I don't know of any other way to do active bi-amping, so I thought it was pretty much implicit in "active bi-amping"? (Asking if I'm overlooking an alternative)

Your link doesn't work for me, but I know the crossover network schematic.

If not doing full quad amping, which seems excessive to me, but rather some "hybrid bi-amping ", I wouldn't have to recreate the entire network sonically though, "just" fx the "handoff"/crossover points to where the crossover takes over.

For now, just trying to establish what might be considered "worthwhile" sonically.

Ideally, you would want to test the crossover to see the effect of this design- the tweaking that occurs outside of circuit modeling is where they get the results they chose and I suspect the slopes and component values wouldn't come from crossover design software without modifications. Maybe someone who has BassBox Pro could test my ideas on this.

WRT "I wouldn't have to recreate the entire network sonically though, "just" fx the "handoff"/crossover points to where the crossover takes over."- which crossover point? If you're not doing this for the sound, what's the point? 90dB sensitivity and 6 Ohm nominal sensitivity aren't terrible- you should be able to achieve decent listening SPL without replacing the passive crossover circuits and regardless of whether you bi-amp or go all-in on four-way amplification, you'll need to replicate the crossover responses and balance the power to each band. With a good amplifier, 110dB should be easy enough- pick one and enjoy it but I don't think going half way is going to yield the results you want or should expect. If you like the sound, replacing the passive crossovers with active will be tricky- it's not as simple as picking a crossover point and setting the levels because again, the design may not be as straightforward as it would be coming directly from crossover design software. Using software and not testing or tweaking would seem to be a lazy way of designing speakers.

 

[AcuDefTechGuy]

On the other hand, I recognize that (as a general rule) larger drivers may require more power and crossover parts that may be more lossy.

When I say "worth it", I'm talking about getting enough bass to be worth it - to bother with bi-amping.

Dual 10" and especially dual 12" woofers can give you a lot of bass like subwoofers can. They are worth it.

But smaller woofers won't give you as much bass. So it's not worth it to me.

 

[nicoleise]

It is not just the crossover points you have to get right, but the slopes also. Both have to be exact. It is clear to me that this project is beyond your current level of competence, and so you what you will do, will be a massive downgrade. So you would need an intensive period of study. The problem is that to design this you are getting to university level study.

Remember you will not only be designing the crossover, but the power supplies, and making sure they are safe and won't burn the house down.

This is also reverse engineering and actually tougher than starting from scratch. If you want active speakers, then select suitable drivers, design the cabinets, drivers, and design the optimal crossovers and select the appropriate power amps. Reverse engineering is always the most challenging.

If you want active speakers, then buy or build them. There are active speakers about.

I don't understand what you're talking about, but you seem to have inserted the assumption that I'm intending to build some DIY powered line level crossover design?

As indicated initially in my first post, I'll use DSP and class D amplification anyways and am (for this intent and purpose) simply wondering about the sonic benefits and whether those are worthwhile the extra DSP and amp channels.

But my question really is about the sonic differences, as mentioned. The electronics are not a concern to me.

 

[nicoleise]

This link shows the specs and crossover schematic with 200Hz, 1200Hz and 3500Hz. It also shows sensitivity at 90dB/W/M and 40Hz-22KHz ±2dB response and amplification of 50-400W recommended amplifier power.

file:///C:/Users/USER/Downloads/hfe_jbl_ti10k_technical_en.pdf

Thanks.
I can't see your link as it points to a file on your computer, but I know the specs. As mentioned, there are two sets of specs though.

The other set of specs has:
- 250 Hz, 1000 Hz, 4000 Hz crossover points
- Sensitivity 91 dB
- 30 Hz - 30 kHz frequency response.
- 10-400 W recommended amplification power.

Despite this, measurements from a review I read suggests the sensitivity to be 86 dB according to the reviewer (who was going by the above set of specs and also doubted the 30 Hz FR from 2x 8" drivers).

It just so happens that another set of similar speakers I have had hooked up to the same amplifier currently driving the Ti10k's are 91 dB, and they are much louder at the same volume settings, so while I have not yet measured, I'm inclined to believe the review statement of 86 dB.

Haven't measured it myself yet, the room they are currently in isn't suited for that. But eventually, I'll find out.

 

[lovinthehd]

If you have the measurement gear, that would be a good start.

 

[nicoleise]

Ideally, you would want to test the crossover to see the effect of this design- the tweaking that occurs outside of circuit modeling is where they get the results they chose and I suspect the slopes and component values wouldn't come from crossover design software without modifications. Maybe someone who has BassBox Pro could test my ideas on this.

WRT "I wouldn't have to recreate the entire network sonically though, "just" fx the "handoff"/crossover points to where the crossover takes over."- which crossover point? If you're not doing this for the sound, what's the point? 90dB sensitivity and 6 Ohm nominal sensitivity aren't terrible- you should be able to achieve decent listening SPL without replacing the passive crossover circuits and regardless of whether you bi-amp or go all-in on four-way amplification, you'll need to replicate the crossover responses and balance the power to each band. With a good amplifier, 110dB should be easy enough- pick one and enjoy it but I don't think going half way is going to yield the results you want or should expect. If you like the sound, replacing the passive crossovers with active will be tricky- it's not as simple as picking a crossover point and setting the levels because again, the design may not be as straightforward as it would be coming directly from crossover design software. Using software and not testing or tweaking would seem to be a lazy way of designing speakers.

Thanks for this useful post (too).

So, the point (or rather the question for me is whether there is a point) is indeed sound. As mentioned, these speakers seem fairly demanding to me, and I'm building a home cinema from scratch since my older 7.1 gear isn't really too useful any longer - AVR doesn't have HDMI to name s simple issue. In addition to these speakers I also intend to install 6 Ti2k surrounds (just normally amped though, even though they support bi-amping. It seems it'd be very diminishing returns).

So in any case, I'll be needing new/more amplification and I plan to use DSP.

I've read a bunch of articles (on this site as well) about bi-amping, and understand that there may be some (in some cases largely subjective) advantage to passive bi-amping, when done with separate amplifiers (or rather separate power supplies), as opposed to fx assigning multiple amp channels in a receiver that in the end taxes the same PSU anyways.

Moving on to active bi-amping, it seems to yield a greater benefit. Some articles attribute this to bypassing the components in the crossover that contribute to the load the amplifier "sees", some to the benefit of the amplifier "seeing" (their terminology, not mine) the driver directly as the load. Essentially two sides of the same coin. Some also touch on the fact that when the filtering happens pre-amplifier, the amp only has to amplify the signal it actually needs for that driver, not stuff that would just get filtered away in the crossover when passively bi-amping.

This makes sense to me as a blanket statement. I really like these speakers and their sound, and expect to enjoy them for many years to come.

So I would be happy (but probably curious) if I simply hooked them up single amped to a powerful amp (say; 250 W). But I'm wondering (as I've never experienced active bi-amping on this type of speaker) whether it actually is a substantial improvement or not. And obviously, it's a great deal of work to find out.

Thus looking for experience and impressions.

As far as the process goes, I haven't yet studied it entirely, but I'd imagine something like measuring the speaker in open air, placing the speakers in room and optimizing their placement. Then reference measurements. And then fx remove the crossover from one speaker and change it to active bi-amping whilst using the passive speaker as reference. Potentially driving the passive speaker with the bridges/jumpers removed and take measurements to understand what the crossover network is essentially feeding to each driver. And then imitating this with the "active" speaker through DSP and adjust with measurements and critical listening. And when happy, implement on the other speaker as well.

I'll study this much more if relevant, but for now as mentioned, it's more about whether it's generally believed to be worth while and thus to get some impressions and experiences of people who tried it or heard systems similarly setup.

 

[nicoleise]

When I say "worth it", I'm talking about getting enough bass to be worth it - to bother with bi-amping.

Dual 10" and especially dual 12" woofers can give you a lot of bass like subwoofers can. They are worth it.

But smaller woofers won't give you as much bass. So it's not worth it to me.

I see. Thanks for the clarification.

As I'm going to be installing four subwoofers in this room also, my goal with this isn't really "quantity of bass". If bi-amping increases the fidelity of the bass, I'd put that down as an advantage though.

I've had dual 10" speakers, and family members still have dual 8s or single 15s. I get what you're saying.

I have no complaints about the bass output in these speakers, its more the case that I wonder if the top end could benefit from the amp not also driving the bass woofers.

EDIT: I should add that it takes cranking the volume up quite a bit to make them actually liven up in the bass region, more so than e.g. my dual 10s. So one potentially positive side effect of bi-amping might be to boost the bass region (perhaps only a variable degree and at lower volumes - difficult to say as it shouldn't turn into the loudness function or sound like a Sonos speaker). But much of this I suspect would be possible with a DSP regardless of bi-amping.

 

[ryanosaur]

I knew this thread would be fun on a rainy day!


hile powered/active bass systems exist paired with passive mid/high networks, the benefit is pretty much always questionable.

The benefit, if any is to be had, is that through practiced measurement and filter design you can perhaps outdo the original passive network in delivering a more flat FR. You would be able to tailor it to your preferences if you choose to.

Choosing to hybrid it seems like a cop out.

There are Amp modules available that can be paired with add-on modules which will allow you to match gain between different power output levels. Pascal comes to mind for this. Also Hypex Fusion can do 3-way options.
The nice thing about Hypex is they have the DSp built in, otherwise, to really do this properly you would need a 2 in 8 out DSP processor.

Short version, put a good strong Amp on these, keep them passive. Unless you really have a bone to pick with the sound and think you can design the active filters better.

 

[lovinthehd]

I think active bi-amping is best for a speaker you build from the ground up rather than try and out-do the original design of a passive speaker. A Crown XLS 2502 would have plenty of power.

 

[ryanosaur]

Could go crown, but I’d say look at the Hypex options from Buckeye if here in the US. The new NCx-500s would be my top choice.

 

[TLS Guy]

I think active bi-amping is best for a speaker you build from the ground up rather than try and out-do the original design of a passive speaker. A Crown XLS 2502 would have plenty of power.

That is exactly correct. The basis of all good speaker design starts with driver selection. You have to have an eye for what is easily achievable. Starting off trying to make an active version of that crossover is a huge uphill challenge.

All speakers are best conceived by starting from ground zero. Mucking about with an existing design is very unlikely to result in improvement and most likely the opposite.

All my designs whether active or passive start from the ground up, or ground zero if you like.

If the OP wants an active speaker he needs to design and build one, or buy one.

 

[nicoleise]

I knew this thread would be fun on a rainy day!


hile powered/active bass systems exist paired with passive mid/high networks, the benefit is pretty much always questionable.

The benefit, if any is to be had, is that through practiced measurement and filter design you can perhaps outdo the original passive network in delivering a more flat FR. You would be able to tailor it to your preferences if you choose to.

Choosing to hybrid it seems like a cop out.

There are Amp modules available that can be paired with add-on modules which will allow you to match gain between different power output levels. Pascal comes to mind for this. Also Hypex Fusion can do 3-way options.
The nice thing about Hypex is they have the DSp built in, otherwise, to really do this properly you would need a 2 in 8 out DSP processor.

Short version, put a good strong Amp on these, keep them passive. Unless you really have a bone to pick with the sound and think you can design the active filters better.

Thanks for a stellar reply! You make an excellent point with the "bone to pick" statement.

I really don't, to be honest. I'm very happy with the sound, especially when I first heard them on a substantially more powerful amp than my current amp.

I never make rash buying decisions, I might research for years before buying a second hand car. Yet I knew within 30 seconds of listening to these speakers, that I wasn't going to leave empty-handed.

I always look for the most ideal answer to everything (probably there's an undiagnosed condition there ), and I have approached this in the same way:

1) What is the most ideal way to drive a speaker?
2) Which obstacles exist in my case?
3) How do I go about them?
4) (finally) Is it worthwhile? (Diminishing returns)

Your answer legitimately made me see the "problem" from a different perspective.

So, thanks! I'll go look for a power amp...

 

[ryanosaur]

1) What is the most ideal way to drive a speaker?

So, thanks! I'll go look for a power amp...

I know that first question wasn't a real ask...

But I'm just going to set this down here and you can decide what's right for you:

Buckeye Amps

Buckeye Amps utilizes the most advanced audio amplifier technologies available. Authorized seller for Hypex and Purifi Class D amplifiers. Based in the US. Free shipping and worldwide service!

www.buckeyeamp.com