Best way to bi-amp two way speakers?

[mike7877]

Amplifier I have right now: Topping LA90 Discrete

Amplifier I'm thinking of using for bi-amping:
2x LA90 Discrete, OR
Benchmark AHB2

I snipped the above from the LA90 Discrete's manual.

The difference in gain between normal and bridged operation is exactly 6dB, additional gain in bridged.
What I was thinking of doing to address this, is connect the XLR outputs on my L70 or A70 Pro to the single amp responsible for the highs (2.1kHz-20kHz, 3rd order Butterworth) and then using the left RCA output for the additional LA90 Discrete powering the left woofer, and right for the other. I think this should do it... am I right to assume this will work?

You might have noticed, I have two fairly similar and capable headphone amp/preamp units. This is by design - I can't be constantly hooking and unhooking + moving one unit up to multiple times per day, every day -it'll wear out the jacks. And I'm not a particularly clumsy person, but moving something thousands of times within a few years, an accident or three are bound to happen lol.

If I choose to use a single Benchmark AHB2 instead, is my only option to use both the L70 and A70 Pro, one for each amplifier?

I was thinking of maybe using a resistor to match the AHB2's gain to the LA90. If I calculate both the input and output impedance, this is possible, right? Is this something that technically inclined people do on occasion when they want to match gain in a system? Or does using a resistor in this manner cause undesired operation of any kind? If not, is there a type of resistor that can be physically trimmed (I don't mean a potentiometer - I actually have a Nobsound NS-05P with a decent potentiometer in it, but now that my system is so perfect, when I put it in the signal path - even when the volume is up all the way - it changes the sound in a way that's hard to describe. It doesn't lose detail, it's not overtly unbalanced... the sound is less impactful and imaging suffers. I guess that wasn't too hard lol. Anyway, I think this has to do with all of the additional contact points (input and output jacks, their connection to the board inside, those traces connections to the pins of the pot, everything inside the pot... A single resistor + a physically trimmable resistor soldered together and made part of a custom interconnect cable I put together using silver content solder seems like a safer bet than the Nobsound... BTW I used this Nobsound thing for a few years with more regularly spec'd gear (not bad stuff by any means - $1000-3000 amplifiers, $1000-3000 speakers, but no THD+n 0.00005% stuff lol) and in every case it was better to use it in place of active preamps, so it says a lot (to me anyway) that I don't want to use it


So... thoughts? Will the gain match up if I use RCA to the two LA90 Discretes in bridge mode for the woofer while using XLR to the one operating normally and driving the tweeters? Is a resistor a viable option to match the HBA2?

 

[DVDdoug]

Your crossover (hardware or software) should have level adjustments.

- I can't be constantly hooking and unhooking + moving one unit up to multiple times per day, every day -it'll wear out the jacks.

What? How does that relate to bi-amping? (You can "split" the signal and run it into your crossover/power amps and your headphone amp.)

 

[Chrispy]

Passive bi-amping more yields a "why"? What speakers?

 

[tmtomh]

There's no point in bi-amping a passive speaker. All you get is more power - and if you have a Benchmark AHB2 already, you've got plenty of power just by hooking that single amp up to your speakers.

 

[Chrispy]

There's no point in bi-amping a passive speaker. All you get is more power - and if you have a Benchmark AHB2 already, you've got plenty of power just by hooking that single amp up to your speakers.

Then you don't gain significant power either that way. Best solution is a more powerful amp generally, and the AHB2 might be somewhat limited in that regard

 

[tmtomh]

Then you don't gain significant power either that way. Best solution is a more powerful amp generally, and the AHB2 might be somewhat limited in that regard

Given that we don't know the listening room size, the listening distance, the speaker sensitivity, or the desired listening SPL, we have no idea how much power the OP needs.

 

[Chrispy]

Given that we don't know the listening room size, the listening distance, the speaker sensitivity, or the desired listening SPL, we have no idea how much power the OP needs.

True. All the parameters that change with all those variables for typical rooms come into play, rather than just some idiotic advertisement as to "power"

 

[Doodski]

@mike7877 have you considered a active crossover system with your speakers? Are you using PEQ (parametric equalizer)?

 

[mike7877]

Given that we don't know the listening room size, the listening distance, the speaker sensitivity, or the desired listening SPL, we have no idea how much power the OP needs.

True. All the parameters that change with all those variables for typical rooms come into play, rather than just some idiotic advertisement as to "power"

The room right now is 10x12x8ft (LWH), the speakers 85dB/W, 8 ohm, sealed design (mentioning because although inefficient, it's an easy load if the volts are there). I do plan on putting the speakers into a bigger room eventually - if I don't move that'll be 14x20x10.

There's no point in bi-amping a passive speaker. All you get is more power - and if you have a Benchmark AHB2 already, you've got plenty of power just by hooking that single amp up to your speakers.

Then you don't gain significant power either that way. Best solution is a more powerful amp generally, and the AHB2 might be somewhat limited in that regard

Yeah, that's what I want - more power. I have heard that there can be mild differences in clarity (especially at higher levels). There's definitely a benefit when the woofers are driven to clipping by a transient and the tweeter isn't affected. I can't remember if the wire I have is 7 or 9 gauge total - it's braided, low capacitance wire, with all of it connected on the amplifier side, and on the speaker side 1/3 of the wires are terminated with a spade which goes to the tweeter, and the remaining 2/3 go to the woofer.

Since I'd like the amp I get to have similar characteristics to the LA90 Discrete I have already, there isn't really much for me to choose from... Buying two AHB2s and running them in bridge mode is a bit more than I'd like to spend, but another two LA90 D would be fine.

Your crossover (hardware or software) should have level adjustments.


What? How does that relate to bi-amping? (You can "split" the signal and run it into your crossover/power amps and your headphone amp.)

For now the system's going to remain passive. I really like the sound of the E70 Velvet, and I've come to understand that you can't use two of the same DACs to power different drivers in the same speaker (timing isn't exact enough, there can be lobing and other bad stuff). The passive crossovers are really good, all components properly oriented and spaced - custom made low gauge air core inductors, high end audio caps

It doesn't seem you read my post... don't feel bad, I don't think anyone else did either lol- when the LA90 Discrete is in bridge mode, its gain is 6dB higher than stereo. I was asking if I could use the RCA out from the preamp to go to the bridged woofer amps, and the XLR to the stereo tweeters amp to level match. You think this would work?

 

[mike7877]

@mike7877 have you considered a active crossover system with your speakers? Are you using PEQ (parametric equalizer)?

I have, but not yet. I'm interested, but I just got and turns out really like the E70 Velvet, and the passive crossovers in the speakers are actually really good... all components are properly oriented and spaced - custom made low gauge air core inductors, high end audio caps, everything 1% or better, 3rd order Butterworth (maximally flat) design

 

[mike7877]

@mike7877 have you considered a active crossover system with your speakers? Are you using PEQ (parametric equalizer)?

The only EQ I've got on them is to extend their frequency response by an octave. I have a 12dB low shelf with a Q of 1.07 centered on 68Hz. I'm still refining it, but it seems to be doing well. Sounds great! Since it's a sealed design I can't stick bungs in their air ducts to reduce the 25-40Hz region when it gets overwhelming, so I actually have a Q 1.42 centered on 28Hz which I bring up and down between -4dB and -10dB, depending

edit: I don't always run the EQ, it's on when I feel like it. It's kind of like having my speakers, and then a bigger version of my speakers that can't go as loud lol. Speaker A and Speaker B lol

 

[Doodski]

I have, but not yet. I'm interested, but I just got and turns out really like the E70 Velvet, and the passive crossovers in the speakers are actually really good... all components are properly oriented and spaced - custom made low gauge air core inductors, high end audio caps, everything 1% or better, 3rd order Butterworth (maximally flat) design

No matter the crossover components capacitive and inductive reactance is reactance and it is near exactly effectively the same no matter how much you spend on crossosver caps and inductors. When you remove all that reactance you get improvements that matter. Bi-Amping is not much of a change in effective listening tests.

 

[Doodski]

The only EQ I've got on them is to extend their frequency response by an octave. I have a 12dB low shelf with a Q of 1.07 centered on 68Hz. I'm still refining it, but it seems to be doing well. Sounds great! Since it's a sealed design I can't stick bungs in their air ducts to reduce the 25-40Hz region when it gets overwhelming, so I actually have a Q 1.42 centered on 28Hz which I bring up and down between -4dB and -10dB, depending

Oh cool. Good that you have EQ/PEQ. makes a major improvement.

 

[mike7877]

No matter the crossover components capacitive and inductive reactance is reactance and it is near exactly effectively the same no matter how much you spend on crossosver caps and inductors. When you remove all that reactance you get improvements that matter. Bi-Amping is not much of a change in effective listening tests.

Yeah, I know, I know... it'll be better. I'm just saying all the really bad parts aren't there and it functions as it should. Active will definitely be better - if I send TOSLINK from the same stream and the same device to two E70 Velvets, do you think they'd decode in sync?

About bi-amping... the main reason I'm bi-amping is to increase power. That's 95% of the reason. I do expect that not having the woofer attached to the same wire (and amplifier) as the tweeter will result in extremely minor improvements in sound (especially at higher levels), but it's not my motivation. When clipping from a transient hits a woofer, and the tweeter's amp isn't affected, that will result in a benefit too. I don't often play music so loud that there's clipping, and I expect once I have an extra 120-180W for each woofer, it'll be even less common

 

[mike7877]

Oh cool. Good that you have EQ/PEQ. makes a major improvement.

Yes, it's great. Especially now that they're fully customizable. I've been using Equalizer APO, latest version, and the way that imaging remains completely unaffected when I adjust the low end to counteract the 12dB/oct rolloff is absolutely amazing. Before that EQ, I couldn't find something that was transparent regarding imaging... Electri-Q was something I used for a while back in the 2007-2017 days, but when I started getting equipment better than Audigy 2 ZS Notebook and AKG K240, Mission M34, Infinity SM-112, its limitations became very apparent. Nothing else did much better than it either, until Equalizer APO. I'm sure there are others that are good, I just stopped looking when I found it lol

 

[Mnyb]

Lots a bass boost means lots of power , so your right there .

I’m not convinced that you can get the gain exactly rigth between the amps , but maybe fine tune with an EQ shelf afterwards ? ( measure ) .

Get a powerful purify or 500x amp instead of bi amping ? That’s cheaper than two AHB2

 

[Chrispy]

Yeah, that's what I want - more power. I have heard that there can be mild differences in clarity (especially at higher levels). There's definitely a benefit when the woofers are driven to clipping by a transient and the tweeter isn't affected. I can't remember if the wire I have is 7 or 9 gauge total - it's braided, low capacitance wire, with all of it connected on the amplifier side, and on the speaker side 1/3 of the wires are terminated with a spade which goes to the tweeter, and the remaining 2/3 go to the woofer.

Then get more power than a 100wpc amp. Go crazy, easy to get a far more powerful amp now for less money than the Benchmark. The Benchmark is a very nice piece, but...

 

[Doodski]

The room right now is 10x12x8ft (LWH), the speakers 85dB/W, 8 ohm, sealed design (mentioning because although inefficient, it's an easy load if the volts are there). I do plan on putting the speakers into a bigger room eventually - if I don't move that'll be 14x20x10.

Then get more power than a 100wpc amp. Go crazy, easy to get a far more powerful amp now for less money than the Benchmark. The Benchmark is a very nice piece, but...

The volts are not there unless you buy very high wattage amp(s). No getting around that. Watts RMS = (Vpeak * 0.707) ^2 / R load
Your speakers whatever they are are simply inefficient.
Your present room is not a difficult space.

 

[mike7877]

The volts are not there unless you buy very high wattage amp(s). No getting around that. Watts RMS = (Vpeak * 0.707) ^2 / R load
Your speakers whatever they are are simply inefficient.
Your present room is not a difficult space.

LA90 Discrete puts out 106V peak to peak into 8 ohms, which works out to 175W - not overly loud, but pretty good. 85dB/W means 100W makes 105dB. 200W is 108, and 108dB is actually each speaker's rating (total, so probably pink noise split at 2.1kHz). I think 175 below 2.1kHz and 52 above (LA90 Discretes configured as described) is probably right on to match the speaker... 227W total, 85dB/W, 108dB max continuous rating.

I don't plan to eq in the bigger room at highish levels if you're thinking that - I have two subs I'll be using in there - a couple KEF Kube 10s. They're also sealed design and DSP'd for the -3dB point to be at 21 or 24Hz (can't remember 100%). The only problem is their crossover is 24dB/oct which doesn't match the speakers' 12... I could add another 12 using the EQ which matches the natural rolloff of the mains, then set the sub crossover to meet...

Each Kube has a 300W RMS amp and effortlessly bottoms the woofers (likely not a small feat because they seem to be able to move close to 4cm peak to peak)

Lots a bass boost means lots of power , so your right there .

I’m not convinced that you can get the gain exactly rigth between the amps , but maybe fine tune with an EQ shelf afterwards ? ( measure ) .

Get a powerful purify or 500x amp instead of bi amping ? That’s cheaper than two AHB2

Ah, yes, I could use an eq shelf at the crossover point... it's not ideal, but I could try it

 

[mike7877]

Then get more power than a 100wpc amp. Go crazy, easy to get a far more powerful amp now for less money than the Benchmark. The Benchmark is a very nice piece, but...

I'm also thinking of two LA90 Discretes in bridge mode, one for each woofer. Would be closer to 200W (180W 8 ohm bridged 1% THD). The speakers continuous SPL is 108dB each, and their efficiency is 85dB - 200W into 85dB/W speakers makes 108dB. I know that 108dB continuous speakers can handle transients 6-10dB higher, and, unlike most class ab amps, the peak rating of the LA90 Discrete is literally the same as its continuous rating (it's voltage limited...), but 200W RMS/peak is still a decent amount. Definitely not limitless, but I do have another system which goes louder (140W into 91dB/W speakers in a 12x16x8ft room). It's not as high fidelity or ideally set up, but if I need loud loud, that's there