Tower bi-amp with front channels or front and sub channels?

[bulskin]

Set-up:
Denon x4500h AVR
Monolith m5100x 5-channel amp
NHT 2.5i towers

With the key components listed up top, I plan to set-up a 6.0.4 (maybe 6.2.4, please read on) Atmos layout. Originally I was going to use the AVR and amp assign with 7.1 + bi-amp (for front towers) and then use the Monolith amp for my 4 height speakers. I reached out to Denon and confirmed that the 11 pre-outs on the AVR are always active no matter what amp assignment you set-up so I figured this would be possible. However, with this setting, Audyssey will not run correctly because the AVR thinks you only have, at most, 2 height channels since there is no way in the manual speaker settings to tell it that you are using an external amp in order to get all 4 heights (only allows you to pick 2 with this amp assignment).

With this, I decided to pivot and amp assign using the 11.1 set-up in the AVR and choosing the pre-outs (external amp) to power only the front towers. Since my external amp has 5 channels at 90W each, I was going to just proceed to bi-amp the towers with pre-outs coming only from the front channels of the AVR (w/RCA splitters). Since I do not currently have any subwoofers, I would just put the front speakers to LARGE so that they would get the full range signal. However, I started to wonder if it would be better to use the front pre-outs only for the mid/tweeter of the towers and then use the 2 sub pre-outs of the AVR for the woofers in the towers. Since my external amp does not have the ability to adjust gain, my thinking is that I would be able to adjust each woofer level independently from the other front drivers using the sub levels in the AVR settings.

Looking for advice as to which way to go and why.


Thanks,
Nick

 

[lovinthehd]

Passive bi-amping like this is a waste of wire. Your setup/calibration will work with your external amp with an appropriate amp assign setting. Without a sub large would probably be a good setting until you get one....

 

[j_garcia]

The AVR x-over in conjunction with the speaker's built in components, which are still active when passive biamping, will leave you with an unknown blend from top to bottom. I don't think I'd do it that way since they are not powered subs in the towers, even though it looks like they have output down to 20Hz. The 2.5i does appear to be fairly low sensitivity (86dB), so I'd rather just drive it full range off the amp. Your tweeters don't benefit from gobs of power since they don't really need it. If it is bass you are after, a sub would be a good addition at some point, as you won't get the same kind of bass from these towers as you would with a good sub by throwing power at them.

 

[bulskin]

The AVR x-over in conjunction with the speaker's built in components, which are still active when passive biamping, will leave you with an unknown blend from top to bottom. I don't think I'd do it that way since they are not powered subs in the towers, even though it looks like they have output down to 20Hz. The 2.5i does appear to be fairly low sensitivity (86dB), so I'd rather just drive it full range off the amp. Your tweeters don't benefit from gobs of power since they don't really need it. If it is bass you are after, a sub would be a good addition at some point, as you won't get the same kind of bass from these towers as you would with a good sub by throwing power at them.

Thank you. I wasn't bi-amping them necessarily to get a ton more bass but more so because they are power hungry and I don't have enough power in one channel to really make them shine. My AVR has 125w per channel and my external has only 90w per channel. I know these towers sound better with power closer to their recommended 200w max. With that said, it sounds like bi-amping them as large fronts is the best option and I definitely plan to build a sub in the not so distant future.

 

[lovinthehd]

There's really no point to that external amp as it is little different from your avr's amp and possibly not quite as good (thinking maybe at 4 ohm the external might have a slight advantage, but not sure).....except perhaps to take some load off the avr. Hope you don't think passive bi-amping doubles power or anything like that....

If you play loud, then a higher output/wattage amp can be better than a lower one. Otherwise, not so much.

 

[bulskin]

There's really no point to that external amp as it is little different from your avr's amp and possibly not quite as good (thinking maybe at 4 ohm the external might have a slight advantage, but not sure).....except perhaps to take some load off the avr. Hope you don't think passive bi-amping doubles power or anything like that....

If you play loud, then a higher output/wattage amp can be better than a lower one. Otherwise, not so much.

 

[bulskin]

I need the external amp either way if I want an 11 channel (actually 10 since I only have 1 rear surround) atmos set-up because my AVR only has 9 internal amps but can process 11 channels. I could use all 9 AVR channels for my base layer speakers and then the external for the 4 height channels but I don't know if 125w is enough for those inefficient towers.

When you said passive bi-amping doesn't mean more power, I am not sure I understand...say I split the pre-out from my AVR front right channel and send it to 2 of the channels on the external amp then bi-amp my towers with those 2 90w channels, wouldn't that mean I am sending 180w to those front towers in total (90 for the uppers and 90 for the woofer)? As opposed to just using the 125w from my single AVR internal amp.

 

[TLS Guy]

Thank you. I wasn't bi-amping them necessarily to get a ton more bass but more so because they are power hungry and I don't have enough power in one channel to really make them shine. My AVR has 125w per channel and my external has only 90w per channel. I know these towers sound better with power closer to their recommended 200w max. With that said, it sounds like bi-amping them as large fronts is the best option and I definitely plan to build a sub in the not so distant future.

It won't increase your power significantly at all. The top end will only take what it needs, which will be not close to the power available. You are just making a complication with zero benefit and actually a downside, since the amps will have different sensitivities. 125 watts versus 200 watts is less than 3db. This idea of a speaker needing power to make it shine, is also nonsense. A speaker will shine if it is any good, if itis lousy, it will sound lousy whatever you drive them with.

I have taken a look at those speakers, and the design is not promising at all. It is a three way with 8" woofer, 6" mid and a tweeter. Crossover points are 100 Hz and 3.3 KHz. Having designed many speakers over the years, I can tell that is trouble with a big T. A passive crossover at 100 Hz is just inviting all sorts of problems. In addition it will make it hard, if not impossible to integrate with a sub.

Not only that the speaker is rolling off 24 db per octave at 75Hz, as ported speakers generally roll of 24 db per octave, if they are QB4 boxes, which this obviously is. It is 11 db down by 50 Hz. To top it off there is a 7.5 db peak at 100 H right at the crossover point.

The choices some designers make just never ceases to amaze me.

I can not find an impedance curve, but from the design I bet it is not pretty, and could quite likely be an amp buster with a crossover at 100 Hz.

 

[lovinthehd]

I need the external amp either way if I want an 11 channel (actually 10 since I only have 1 rear surround) atmos set-up because my AVR only has 9 internal amps but can process 11 channels. I could use all 9 AVR channels for my base layer speakers and then the external for the 4 height channels but I don't know if 125w is enough for those inefficient towers.

When you said passive bi-amping doesn't mean more power, I am not sure I understand...say I split the pre-out from my AVR front right channel and send it to 2 of the channels on the external amp then bi-amp my towers with those 2 90w channels, wouldn't that mean I am sending 180w to those front towers in total (90 for the uppers and 90 for the woofer)? As opposed to just using the 125w from my single AVR internal amp.

No, you're still sending 90w to two parts of the passive crossover, with likely no particular advantage doing so....the upper frequency drivers don't need the power and the possible additional power for the lower frequency driver is miniscule, maybe 1dB?

 

[bulskin]

No, you're still sending 90w to two parts of the passive crossover, with likely no particular advantage doing so....the upper frequency drivers don't need the power and the possible additional power for the lower frequency driver is miniscule, maybe 1dB?

Oh, wow that is definitely not what I was thinking. I assumed when I bi-amped them in the past using just my AVR, I was doubling the power because they seemed to be much louder. Thanks for the information.

 

[bulskin]

It won't increase your power significantly at all. The top end will only take what it needs, which will be not close to the power available. You are just making a complication with zero benefit and actually a downside, since the amps will have different sensitivities. 125 watts versus 200 watts is less than 3db. This idea of a speaker needing power to make it shine, is also nonsense. A speaker will shine if it is any good, if itis lousy, it will sound lousy whatever you drive them with.

I have taken a look at those speakers, and the design is not promising at all. It is a three way with 8" woofer, 6" mid and a tweeter. Crossover points are 100 Hz and 3.3 KHz. Having designed many speakers over the years, I can tell that is trouble with a big T. A passive crossover at 100 Hz is just inviting all sorts of problems. In addition it will make it hard, if not impossible to integrate with a sub.

Not only that the speaker is rolling off 24 db per octave at 75Hz, as ported speakers generally roll of 24 db per octave, if they are QB4 boxes, which this obviously is. It is 11 db down by 50 Hz. To top it off there is a 7.5 db peak at 100 H right at the crossover point.

The choices some designers make just never ceases to amaze me.

I can not find an impedance curve, but from the design I bet it is not pretty, and could quite likely be an amp buster with a crossover at 100 Hz.

www.audioexcite.com » NHT 2.5i review part 2

This is a pretty good detailed review of these speakers. I have always thought they sounded good and have read good things about them (other than requiring lots of power). Wonder if you still have concerns with the design after reading this article or not. They were gifted to me and I never thought about having to replace them.

 

[lovinthehd]

Oh, wow that is definitely not what I was thinking. I assumed when I bi-amped them in the past using just my AVR, I was doubling the power because they seemed to be much louder. Thanks for the information.

Expectation bias probably had a part in that, hard to imagine more than a 1dB advantage.....which isn't particularly noticeable.

 

[TLS Guy]

www.audioexcite.com » NHT 2.5i review part 2

This is a pretty good detailed review of these speakers. I have always thought they sounded good and have read good things about them (other than requiring lots of power). Wonder if you still have concerns with the design after reading this article or not. They were gifted to me and I never thought about having to replace them.

That confirms what I suspected. There is a a nasty peak at crossover and then a rapid roll off. There is a nasty impedance drop to 3.5 ohms at that peak, which is apart from the tuning peaks of the box box and its null in the mid forties. I strongly suspect that the 100 Hz crossover is actually in resonance. That would discourage me from connecting any of my amps to it.

The mid to tweeter crossover seems well managed.

Probably the only way to salvage that speaker is to get two subs. I would just connect to the mid and tweeter crossover and just use the mids and tweeter of those speakers, and cross to the subs at 150 Hz. It would be preferable to use two subs one next to each speaker. That will get rid of that total mess created by that 100 Hz passive crossover. The reviewer did state that bass peak was audible and I bet it is. That is the very definition of one note bass.