Bass Optimizer level, etc.

[andyadler]

Hello everyone. I’ve just taken delivery of a TN1220, hooked it up to my system for some initial auditions, etc. All seems in order, but I want to make sure I’m using the Bass Optimizer in the proper/best fashion.



My setup includes an admittedly venerable Lexicon CP-1+ as my preamp, and an NAD SA-3 subwoofer amplifier, which has built-in low and high-pass filters. I’ve run a pair of interconnects from the CP-1+’s main-out jacks to the Bass Optimizer’s input jacks, and another pair of interconnects from the Optimizer’s output jacks to the SA-3’s line-in jacks. The SA-3 is thus filtering out low frequencies from the main amplifier (typically a conrad-johnson MV-50). I can set the subwoofer’s crossover point manually (my main speakers are Spica TC-50s), and _also_ control the subwoofer amp output level from the SA-3’s front control knob.



The “complicating” factor in all this is the Optimizer’s level control. In my configuration, it’s not only affecting the subwoofer gain, but also my main volume levels. I see from another message posted here that the optimizer’s 1 o’clock setting is essentially unity gain. So if I leave the level set at this point, can I control the subwoofer output from the SA-3’s gain control? Or is there some other way of connecting the optimizer that I’m not thinking of that would be a better option. The Lexicon does have a single (summed-to-mono) output channel, but I don’t want to use this because I would give up the high and low-pass filtration flexibility of my present set up.





I should add, BTW, that the 1220 sounds quite impressive in its present configuration, so I may indeed be doing everything correctly. But I’m open to suggestions.







Many thanks in advance,





aa.

[Sasha_G]

The “complicating” factor in all this is the Optimizer’s level control. In my configuration, it’s not only affecting the subwoofer gain, but also my main volume levels.
Are you using a Y connector back into the preamp?

Sounds like you are using a Y connectors to put the Bass Optimizer output back into your Lexicon CP-1+ PRE-INs. This would be the only way the volume level would effect your main amp (as opposed to your subwoofer's amp).

If so, your system should have the Y connectors before the bass optimizer, not after it. The signal going back into the PRE-INs should NOT be influenced by the bass optimizer this way.

[andyadler]

Hello Sasha, and thanks for the reply. I'm _not_ using any Y-connectors, however, so perhaps my explanation was less than completely clear. To clarify: If I were not using the Bass Optimizer, I'd simply running a pair of interconnects from the Lexicon's Main-outs to the Main-ins of the NHT SA-3 subwoofer amplifier. Another pair of interconnects would then feed the filtered signal to my main amplifier. At the rear of the SA-3 are rotary controls for High Pass & Low Pass filtration, plus adjustable phase. I'm setting the high pass at 80 Hz for the Spicas, with the low pass roughly the same.

The Bass Optimizer simply goes between the Lexicon and the SA-3, which is why the optimizer's level control affects the main-amplifier volume. Now, I'm not finding this necessarily to be a problem, because the sound seems fine. Again, though, I have the sensation that there might be an alternative setup. Whatever I do, I do _not_ want to give up the high and low-pass filtering offered by the SA-3 -- in other words, I don't want to run my Spicas full range, nor have my main amplifier handle low-bass frequencies.

Nudge me in the right direction, if need be....


best...aa.

[DavidD]

I had the same question Sasha had, but I think I see now. You're putting the Optimizer before the SA-3 splits the high level content to your main amplifier. If this is correct, the ideal solution would be to put the Optimizer after the SA-3, but you can't do that because there is nothing but speaker wire after the SA-3. So, I suggest you leave things as they are. Leave the Optimizer on Unity gain, and adjust the subwoofer level from the SA-3.

[andyadler]

David -- You're correct -- since the SA-3 is an _integrated_ amplifier & high-low pass filter, there doesn't seem a way to place the Bass Optimizer further down the chain. But as long as the optimizer is supplying the necessary equlization, I'm not too concerned. I was a bit worried about inserting another device + interconnects in the signal path, but the sound I'm getting doesn't seem to inclyde any added artifacts. It's an astonishing improvement, really, compared to the halfway measure I'd been employing (an old NHT passive woofer system intended to augment the company's original Model 1s from about 16 years ago).

take care...aa

[andyadler]

Along the same lines, I concede that I'm not especially about having a gain stage applied to my full-range signal before it splits into high and low-pass paths. My instinct is that this can't help but degrade the overal sound somehow, though it's also enrirely possible that in practice whatever compromises arise are inaudible.

Does the Bass Optimizer itself provide gain (via opamps?), or is that accomplished through my main & subwooder amplifiers? I'm a bit hazy as to exactly where in the signal chain things happen, and how best to balance level controls on the Lexicon, SA-3 and optimizer to achieve the best results. For instance, will "unity gain" on the optimizer provide enough extension to the sub? I haven't yet gotten out my Radio Shack SPL meter to set levels -- what's the best way of going about this, do you think? I don't have a huge array of test discs handy (the only one I could immediately find, actually, was Stereophile's Test CD #3 from almost 10 years ago). Right now I'm tending to make level adjustments simply by ear.

Part of me is now considering selling the SA-3 on eBay and buying, for instance, Hsu's 500 watt amp/crossover. But I don't want to go that route unless I've absolutely convinced myself that my present setup won't do a sufficient job.


thanks...aa.

[DavidD]

I should probably keep my mouth and keyboard shut and let the Hsu guys answer, but here goes anyway. I don't think the gain control will affect your extension. I imagine it just controls the output level. Unity gain should leave the input siginal level unchanged.

With a sub of the quality of the 1220, a setup disc and SPL meter are very important. Our ears are very poor at matching bass levels.

[andyadler]

Oh, I'm all in favor of open mouths, David, so please continue to plunge right in (I'm pretty sure Sasha & Co. won't mind).

I'm still wondering if applying gain to my full-range signal -- as opposed to only the post-low-pass signal -- will cause my performance to suffer. Obviously the Bass Optimizer was intended to sit between a low-pass-filtered signal and an amplifier, which as you observed isn't possible with the all-in-the-same-chassis NHT SA-3. So I have to live with my potentially compromised setup, or start again essentially from scratch. The latter route would end up costing me about $1,200 (TN1220HO + Hsu 500-watt amp), minus, of course, whatever I can get for an excellent-condition SA-3. This assumes that I keep the TN1220, as opposed to starting over with, say, a VTF-3MKII. But I like the increased flexibility of the TN1220 + external amp, the ease of moving this sub around (vs a very heavy box), and the lack of enclosure colorations intrinsic to Hsu's elegantly simple cylinder. I'd also like the option of adding a second TN1220 in parallel with the first, and the large Hsu amp would allow that.

Still, that's more money than I had intended to spend at this point, which makes me hesitate. Also, can you tell me (Sasha will hopefully chime in here) whether the Bass Optimizer _itself_ provides gain, or is just a filtering conduit that directs the subwoofer amp to provide needed equlization.

To be honest, right now I'm so tickled at the improved sound in my listening room -- even without much additional placement trials and level-setting -- that I haven't completely considered all my options. This is one acoustical revelation -- another recent one for me being a recently-acquired set of Etymotics ER-4P intra-canal earphones. Remarkable things, these.

Let me know what you think (and, by the way, could you tell me what your Hsu setup consists of?).



thanks...aa.

[DavidD]

As I said, I don't think it should cause any degradation, but I have no personal experience with the bass optimizer. If you are very uncomfortable with the present situation and don't want to spend the money for the excellent 500 watt amp, you could try asking Hsu to send you another optimizer configured as a high pass filter. You could insert it before your "regular" optimizer and filter out the stuff inteded for your main speakers.

A somewhat more expensive option (but still significantly less than the 500 watt amp) is to return your optimizer in favor of the Hsu High End Crossover. From reading the material, it provides a higher quality crossover and also includes the functions of the optimizer. You could still use your NHT amp, but you wouldn't want to use its crossover. Talk to Hsu before you do, just so you understand what you're getting.

As far as my Hsu equipment, I have a TN1225, which is no longer made. It is a shorter version of the TN1220, with extension only to 25Hz. I'm powering it with a Hsu 250 watt amp. Although they still make a 250 watt amplifier, mine is an older version, also no longer made.

[Sorny]

The Bass Optimizer has a Class-A gain stage and applies up to 15dB gain to the signal (this is covered in the manual, and is listed on the product description page here on the HSU website). I cannot answer, however, whether or not it is a suited for a full range signal in an application such as yours. I suspect it is not doing harm when set for unity gain at ~1:00 position.

Sorny

[andyadler]

Sorny -- Your post reminds me that for some reason there was _no_ documentation enclosed with the optimizer, just the unit itself. Not that much is needed, of course.

So at unity gain the optimizer is still providing equlization of frequencies below 35Hz, plus infrasonic filtering, but just not adding any additional gain, correct?


thanks...aa

[Sorny]

So at unity gain the optimizer is still providing equlization of frequencies below 35Hz, plus infrasonic filtering, but just not adding any additional gain, correct?


To the best of my knowledge, that is correct.

Sorny

[Michael Bain]

Yeah, that sounds about right.

[Active Speaker]

Andy,

Return the optimizer, sell the SA-3, & get the 500 watt amp. Despite the money, you WILL NOT be disappointed! I just bought the 1220/500 watt amp combo, hooked it to my system using the hi-pass crossover, and it is AMAZING! I measured it flat (within +/- 1 db from 50 - 20 hz (it comes set at 51 hz)! I, too, was reluctant to part with equipment and outlay more money, but I just can't believe how good the resulting sound is! I also can't believe that so many people are buying the VTF & STF series instead of the TN; in my opinion, its only weakness is that it is top heavy. But, it is sonically transparent, powerful, quiet at all times, flat in frequency response, stylish, light, etc... You are absolutely correct about the flexibility the 500 watt amp gives you. This combo is WELL worth the money; I'm going to add another subwoofer down the road.

[andyadler]

I'm moving closer to going just that route (returning the Optimizer and buying the 500-watt amplifier), though I'm not _completely_ convinced that's the best route for me. I happen to like the SA-3 quite a bit for several reasons: easily variable high-pass options (don't have to do the manual plug-in module thingy the Hsu amp requires), polarity can be adjusted at 0, 90, 180 and 270-degrees, infinitely variable low-pass, etc. The amp is rated at 250 watts with a fair degree of dynamic headroom, as I recall. Still, I remain a bit uneasy about having the Optimizer in my main singnal path. Perhaps it's acoustical paranoia...


I also wonder that, if I end up adding another TN1220, having two separate amplifiers would be advantageous over a single unit, because (as another series of messages here suggested) you could vary gain for each independently, potentially useful if you locate the subs in different areas of your listening room. Do you think that's a valid argument? And finally, is the crossover network built into the Hsu 500-watt amp (who makes this for them, anyway?) the same quality as Hsu's separate "audiophile" outboard crossover?


thanks, and take care,


aa.

[andyadler]

Well, guess what: I've gone and ordered the 500-watter; it should arrive Thursday. I'm going to compare its performance in my system vis-a-vis the NHT SA-3/Bass Optimizer. Assuming it's clearly superior, I'll keep it. if I can't tell the difference, or if for some off reason is actually doesn't sound as good, it'll go back to Hsu. In any event I'm hanging on to the TN1220. I'd much rather have a realtively lightwewight unit such as this, with its inherent enclosure rigidity, than a large box I can't easily move myself (and which lacks an integral high-pass crossover).

On another point, I'd very much appreciate it if you could jog my brain on the subject of measuring/balancing sub & main-sepeaker levels. I have teh Hsu BAS test CD-R with the various pink noise and warble-tone tracks, the trusty RS SPL meter, and whT I thought was a reasonable understanding of what's fundamentally required. But I can't seem to get how I'm supposed to arrive at a "refererence" level, what initial gain to set, etc. I tried initially by playing pink noise through my main-channel speakers at a moderate volume level, and then setting the level on the meter at 75 db. Then, with only the sub channel active and playing a 60Hz tone, I adjusted the SA-3's level control until I also was at 75 db (I got this level from a quick read-through of the 500-watt amp's PDF-formatted manual online here). This would appear to put the sub and main channels in nominal balance, but it's immediately apparent that there's far too little output from the sub. Obviously I'm missing something very basic along the way, but I'm just too dense (or tired) to figure out what. So any calibration advice would be appreciated.


best...aa.

[DavidD]

It sounds like your general procedure for matching the levels is pretty good. There could be a couple of things going on here. I can't tell for sure from your description whether your main channels are active when you're measuring your sub.

If they are:

In your current setup, what is the high pass crossover set to on your SA-3? As your pass the crossover frequency, your main speakers don't just cut off. Instead they gradually reduce in level as your sub increases in level. If you measure the level at too high a frequency, you might be getting much more mains than sub. Then when the mains are reduced or eliminated at lower frequency, the sub level might be too low.

If the mains aren't active:

This might be a perceptual problem. Our ears aren't as sensitive to low frequencies as they are to high frequenciess. So we might perceive a balanced bass level as too low relative to higher frequencies. Many people like to turn the bass up a bit to compensate. When you're considering the bass level, don't forget to consider the meter correction factors.

[andyadler]

David: Neither my main nor my side-channel speakers were active during my subwoofer calibration attempts, just the sub. I'm going to have another go at it sometime this weekend when my brain is fresher and I have more time.


thanks...aa

[Active Speaker]

AA,

Try using the Stereophile Test CD 1; it has warble tones from 1000 down to 20 hz. Set the volume control with the sub "on" until the spl meter reads 80 hz. Then simply write down what you get on each track, and add values for the rs meter low frequencies.

What is the steepness of the SA-3's crossover? Generally, "variable" active crossovers are much less desirable than "set" active crossover frequencies. Also, it is generally far better to use higher order crossover frequencies (3rd order, 18 db per octave, or 4th order, 24 db per octave) unless your speakers use drivers that are unusually flat. As I understand it, the Hsu amp uses a very high quality crossover in the amp that either equals or exceeds the crossover in the high end crossover. I built all of my own speakers before purchasing the 1220; my main speakers are actively crossed and are flat to within +/- 1 db. I am very impressed with the 1220/500 watt amp combo as I've said before. After experiencing the sonic improvements in "stereo" that I'm experiencing, I can't believe that Hsu is leaning more toward the box subs. I guess that the main reason is that they are "selling"!! My advice is to grab the TN before they stop making it! It is KILLER for BOTH music AND HOME THEATER!

[andyadler]

Latest update: The 500-watt amp arrived today, and it's now playing in the system. I'll say one thing: Hsu doesn't make it easy on anyone who wants to experiment with different high/low-pass settings -- I didn't realize that I'd have to insert three pesky crossover modules (each with those spindly legs) for each setting. I swapped out the stock 51Hz modules for 75Hz ones (better suited to my smallish Spicas); I don't think I'll be doing much fiddling around after this).

Of course what matters is how this all sounds, and after a couple of hours of semi-critical listening, I have to concede that the bass sounds markedly tighter and well-defined below 40Hz than it did with the Bass Optimizer module inserted between my processor-outs and the NHT SA-3. Imaging also seems improved, though I may not have levels _precisely_ matched, and it's difficult to do a real A/B comparison. Still, the results are encouraging enough that -- pending a few more days' worth of evaluation -- it looks like I'll be keeping the big amp and returning the Optimizer. Now all I need is a second TN1220...


best...aa.

[andyadler]

Latest update: The 500-watt amp arrived today, and it's now playing in the system. I'll say one thing: Hsu doesn't make it easy on anyone who wants to experiment with different high/low-pass settings -- I didn't realize that I'd have to insert three pesky crossover modules (each with those spindly legs) for each setting. I swapped out the stock 51Hz modules for 75Hz ones (better suited to my smallish Spicas); I don't think I'll be doing much fiddling around after this).

Of course what matters is how this all sounds, and after a couple of hours of semi-critical listening, I have to concede that the bass sounds markedly tighter and well-defined below 40Hz than it did with the Bass Optimizer module inserted between my processor-outs and the NHT SA-3. Imaging also seems improved, though I may not have levels _precisely_ matched, and it's difficult to do a real A/B comparison. Still, the results are encouraging enough that -- pending a few more days' worth of evaluation -- it looks like I'll be keeping the big amp and returning the Optimizer. Now all I need is a second TN1220...


best...aa.