AN Std 8 + SI Super T-Amp = Weak Bass?

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Hi, first post!

I'm a DIY audio newbie. About a year ago, I read that TNT review of the Sonic Impact T-Amp, and had to have one. My goal was to use my computer as the source (lossless, CD-quality FLAC), and have the best sound possible at a reasonable price.

I received the Super version of the T-Amp as a gift. Also based on a review on the TNT audio site, I ended up buying the Audio Nirvana Standard 8" Full Range speakers. I built the "1.3" cabinet with plans from the CommonSense Audio website.

For reference, I've never really had any "hi-fi" or "audiophile" quality equipment. FWIW, I've got Paradigm Monitor 5's powered by a Pioneer Elite stereo amp as my "reference" system (also using computer FLAC as source).

Anyway, I've been running the Super T-Amp amp and Audio Nirvana speakers about 30 hours now. They sound great, except that the bass seems rather weak. The bass doesn't sound bad, just not nearly as prominent as the highs and mids. For example, as a guitar player, I think the guitar sounds really well-defined, very realistic. But the bass just isn't there. Example: I played Metallica's "One"---there's that intense double kick-drum breakdown in the middle of the song---the effect was kind of lost.

I've been doing some Internet research, and from what I've gleaned, neither the Sonic Impact nor the Audio Nirvana speakers are strong on bass. So as a combo, I probably should have expected this.

So I'm basically looking for suggestions as to what I could do to get some more bass out of this setup without spending a lot of money. I'd rather not use a sub, as I don't have the room---the "1.3" cabinets are really already too big! Likewise, I've seen lots of suggestions for the "BIB" (bigger is better) cabinets. Again, in my little apartment, that's just not practical.

So I'm wondering if there's a better (but not bigger!) cabinet I can build for the AN drivers? Or perhaps use a different amp? One idea is to pair the T-Amp with those Insignia NS-B2111 speakers from Best Buy, and get something like the Panasonic XR55S for my Audio Nirvana speakers. Just random ideas from the random information I've been reading! :)

Any thoughts or suggestions would be much appreciated!

Thanks,
Matt
 
Hi Matt,

I'm afraid you have a problem mate, because we can't break the laws of physics. The amp is fine, no problems there. The Super T doesn't have the LF issues the el-cheapo version suffers from. Your major problem is / are the drivers. The AN units are low Q drivers, of limited excursion. That means that they have a very powerful motor, and don't move very far. They're basically over-damped in the bass, and they need a big box (and preferably a horn, whatever it claims on the commonsenseaudio site) to generate any bass heft -bigger than the 1.3. If you can let me know what the vent dimensions are, I can run a model in MathCAD on what exactly it's doing.

As is, you could stick a fairly large resistor on them, which will bring the LF up a bit, but the amp will probably run out of steam. Try a 3ohm resistor in the + lead to the driver. That will probably help a bit.

Another separate issue is baffle-step. You'll have a ~3db loss below about 450Hz; correcting for this with a simple compensation circuit will help make the speaker better balanced.

Best
Scott
 
Another separate issue is baffle-step. You'll have a ~3db loss below about 450Hz; correcting for this with a simple compensation circuit will help make the speaker better balanced.

Agreed.


By looking at the spec sheet it appears that the driver runs hot in the mid and highs on top of the natural acoustic baffle step. You may end up needing 10dB to get it sounding balanced. But let your ears are the judge, do what sounds best. As-is, it appears the speaker puts out 100-110dB from 1.5k to 15kHz. Where as 100-500Hz is 90-92ish dB @1W. The compensation will bring the upper frequencies down to the level of the midbass. When all is said and done your speaker will probably be about 90-91dB efficient, but much more balanced. If your worried about the loss in efficiency start with 6dB of compensation rather than 10.

Here is a helpfull spreadsheet.
http://www.quarter-wave.com/General/BSC_Calculator.xls
 
OK, well, that puts box tuning to ~65Hz -it's working more like a small MLTL. See attached. Moderately well balanced, apart from the peak at cut-off, which isn't ideal, but extension isn't great.
 

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To improve LF extension, you could increase the vent length to 3.5in (there are plenty of pipes / ports available you should be able to utilise). You'll loose a bit of LF gain, but gain about 17Hz of extension, with a box tuning of about 48Hz, which is pretty reasonable for this driver in a relatively small / short cabinet.

I suspect baffle-step loss is probably causing you some problems too, especially in conjunction with the driver's naturally rising response. I suggest you put a 3ohm resistor in parallel with a 1mH inductor in the + lead to the driver. That should help flatten things out nicely. In conjunction with the increased vent length, it should give an anechoic LF response similar to the attached. To adjust the level of correction, increase or decrease the value of the resistor. Unfortunately, no voice-coil inductance figure is published for the driver, so setting a zobel value is tricky. FWIW, I'd probably try a 3uf cap in series with a 9ohm resistor across the + & - terminals. That should help a bit too. Overall, you should find the sound better balanced, with improved extension.

Hope that helps
Scott
 

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Scottmoose & Jeb-D: thank you very much for all your help and suggestions! I'm definitely going to continue to hack on these speakers/enclosures a bit.

In the meantime, I have one more question: I've heard about listener fatigue, but don't believe I've ever experienced it... until last night.

I finally got a chance to listen to this setup for more than 30 minutes or so. I was listening to FLAC audio files (i.e. lossless CD quality). I also upgraded my computer's soundcard to an M-Audio Audiophile 2496. I never had the Super T-Amp above 9:00 o'clock on the volume control.

After about two hours of listening, I thought my ears kind of hurt. It wasn't really pain, it was just that my ears felt really sensitive, and sounds made me feel uncomfortable. Turning the volume down relieved the discomfort. I kept turning the volume down, until it was below typical speaking volume. I honestly don't think I had the music up too loud at all prior to this. And the sensation was different than I've experienced from being around music that's too loud for long periods of time (e.g. such as at a concert).

From what I've heard, listening fatigue is more likely when there are too many high frequencies in the sound. I don't know if this is accurate or not, but it fits with the behavior of these speakers as we've discussed thus far (i.e. too much emphasis on the high notes).

Anyway, just looking for thoughts or ideas... does my description sound like listening fatigue? And if so, would the mods you've suggested help alleviate this (as it flattens the frequency curve on the high side)?

Thanks again!
Matt
 
Yes that sounds like listening fatigue. After a while listening makes you feel uncomfortable due to some imbalance in the sound. As Scott said, try a compensation circuit. Their not that expensive or difficult to build and you can always remove it.


www.partsexpress.com carries the parts you will need. I usually use Jantzen inductors and capacitors they are good performance and inexpensive. Air core inductors are recommended. You can first build them in line with the speaker cables for tweak ability before installing them into the enclosure if you should decide to do so.

Honestly, I've had compensation circuits take some full-rangers from sounding like a POS factory car system from the 80's to something you get excited about every time you have a chance to listen.

Do it...Do it.
 
I think your only real option is a horn. My ANS super 8's in a horn put out so much low end that it can shake pictures on my walls. This driver will never work properly in a Bass reflex, ever (for those that disagree, think about the 30 watt max and the limited xmax of the driver. It just won't have the oomph to get going, regardless of what Dave at Common Sense says) An MLTL might do better but you would need more amp as the t-amp only puts out about 4 really clean watts and about 6 so so watts. After baffle step correction circuits you would end up with an 88 DB efficient speaker. Once again, you will need more power and you are still limited by xmax and 30 watts handling. A horn is really your only option. I actually run my ANS8's in a 35 Hz horn and run them with a heavily modded (but not too much different from a super t-amp) t-amp. Not to much of a problem up to a certain level. Definitely louder than I would listen to but they do begin to fall apart. Through my 300B's (a type of low powered tube amp if you don't know) I can get more in every way. Still, for symphonic listening, I switch over to my Cambridge Audio Azur Amp. That has enough power for the transients. Rock is a little easier to handle than big symphony but is still in the same realm.

So, in the end, build a horn. My model one is not a bad horn but my 3 (which the plans for will be available this week) should be far better. Or, look at one of Scott's horns for the 208. The ANS super 8 should work very well in them without any modifications. After building some horns, if you want loud and clean then I would suggest looking at a new amp, (if you are strapped for cash) like the Cambridge Audio Azur 340A. This is an integrated amp with 40 watts per channel of super clean power. Not to mention, it is the only true audiophile grade amp available for 329 bux new (anywhere).

Good Luck!

Tom
 
Scottmoose said:
An alternative would be to build one of Nelson Pass's Zen or First Watt amps, which in terms of performance per £ are off the map, and would be a superlative match to the AN drivers. The F2 would be my choice for use with those units.


That's an excellent point Scott. I didn't even think of that. Do you think with this driver's rising response that that would be enough to make the difference though? From 100 Hz this driver has a 10 DB rise! This transfers to a minimum of 6-8 db to deal with. It is a wonderful driver but suffers from all the same problems of the Lowthers and old Altec drivers. I could be wrong but this is what makes this driver not particularly attractive to BIB apps as well. I think though that I may be overly concerned with flat responses. I just don't like Sax or guitar to sound like it is sitting on my head. :xeye:

Thanks!

Tom
 
I meant in conjunction with a differnt type of cabinet.

One of Nelson's amps would certainly help whatever cabinet they're loaded in, though if they're mounted in something requiring a BSC circuit, then the latter will need to be changed from the usual type if one of the current-source amps is used.

Generally I'd prefer to horn load these drivers -a long horn which will help take down the HF would be ideal. Should do well in a BIB or a more usual style of BLH.
 
Matt, the plans for the Model III are up. Have a look. They may be exactly what you are looking for. AFAIK they are the smallest enclosures I have seen (for the level of performance). (Of course that was my intent when I designed them, I didn't want huge enclosures as I have been dealing with since I bought the ANS8s. The model 1 was a monster and took up a good deal of floorspace. I decided to go up. 62 inches high is not unreasonable though). Good luck!

Here is the link if you are interested, and a small rendering at the bottom of this post: http://www.box.net/shared/u4rs0mntw0

Tom
 

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I haven't had a chance to play with this setup since my initial post (both my fiancee and I are looking for new jobs and looking to move). I'm hoping we get into a house soon, where I'll have room to work on more projects like this. Right now, I just don't have the space to build a horn or BIB.

But, I'm still curious... it looks like the horn is the way to go, but I'm not sure my wood working skills (and tools!) are at the level needed to do a decent job. E.g., there's quite a jump in complexity from the CommonSenseAudio 1.3 to Harderror's Model III.

But the BIB boxes look more accessible (read: easier) to me. How do you suppose a BIB would compare to a horn for this driver?

I still plan to play with compensation circuits though, just need more time!

Finally... I took a quick glance at the First Pass F2 amps on the web. They look great, but the $2k+ pricetag is getting away from my original goal of having great sound at a low price. :)

Thanks again for all the help and feedback everyone!

Matt
 
The BIB is a horn. Depending on how big you go, you'll be flat to the high 20Hz regions; bass has massive air & space, rather like dipole woofers (don't ask me why, the physics is the exact reverse, but that's what they sound like), timing like quicksilver.

Re the F2, you can build one yourself for about £100 (~$200). My mate Ed did just that. All the plans you need are on the web, or here, in the Pass Labs section of the forum.
 
I'm currently running a set of AN super 8 cast frames in a 1.3 cabinets. To balance the sound for my ears, I’m running a 2.5mH inductor and a 8 ohm resistor in parallel. It really made a major difference. Before the baffle step correction it was on the shouty side.
 
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