Bombadil wrote: "It "might" be true that your lack of "oomph" can fixed via a subwoofer. But it is my experience that when it comes to classical music, a lot of wattage is needed through the midrange."

I was on the same page until I read about the SUB configuration possibilities, which should definitely alleviate the "oomph" limitation. Evidently, this is not a black and white argument and a combination of variables are in place here, as you point out.

Rosco65 wrote: "... it is almost impossible to avoid instantaneous clipping during replay of musically-demanding pieces."

With 20 dB headroom needs in those demanding passages and my limited Triode-configured Inspire (which sounds magnificent when those demands are tamed), better bass management and power may alleviate the resulting "oomph" limitations, in part due to the benign clipping nature of the Triode-strapped tube amp (and all tube amps in general). Although this avenue may not suffice, it will certainly improve the much important bass management, an added benefit affecting even the already quite good acoustic jazz experience.

pstrisik wrote: "I understand from living "up here" in Alaska. Shipping is painful. I imagine even worse for you. Is "down there" Brazil? That memory is from some time ago when we might have had a similar discussion about other equipment, unless that was someone else."

I lived in Sao Paulo for a few years and that is where I acquired the Velodyne SUB, 10 years ago. I'm currently stationed in Panama City, Central America.

Would stuffing the SUB port on my Velodyne pose any risk to it? I'll try that first and learn from the experience. But, I'm convinced an improved SUB platform is a must in my case. Thanks for the valuable inputs.

I wouldn't think it would cause harm unless you were pushing it to audible distortion. Good question for Velodyne or on a forum if there is one.

A platform would likely help. I use a Herbie's product for the sub feet. I'd like to try platforms, but not motivated enough to do it.

I used the term "platform" to mean a bass sub-system or configuration beyond the usual single SUB arrangement. I was not referring to the actual SUBs' physical foundations. Given the Inspire amp's unique SQ but limited by its power (especially in Triode), I'm convinced more sophisticated and thorough bass management is optimal. My wrong choice of words, sorry.

An emily litella moment but there's an audiophile nerd joke in there somewhere!



http://i.imgur.com/8Os99y7m.jpg

Just noticed this post. We sure are running our Inspires in different configurations. Running 6V6 in single ended triode mode will probably produce about 4 watts per channel, maybe 4.5 wpc.

I know people who love that setup.

No need for a switch as you are running in both single-ended and triode. Switches are typically employed to switch between triode and ultralinear, which usually doubles the power output. My Inspire is single-ended pentode.

I do have a triode tube amp, but it is push-pull, producing about 18-20 wpc with two EL34/6CA7/KT77 tubes per channel.

In my Triode-strapped amp (same as FloridaBoy's), I can't appreciate the 6V6's, which sound anemic (must be the speakers). Instead, the KT-77 / KT-88's are best all around, with the 6P3S-E and 6550's in a second tier, maybe along the 350B also. No 6V6s for me though.

My KT88 (non-triode) puts out about 5wpc using a 6V6. Wired for triode I wouldn't expect more than 2-3wpc. I would expect maybe 6-8wpc from a triode wired KT77.

There are some inherent compromises when choosing low-powered single ended amps. We must choose very high efficiency (>98dB) speakers with their demands on space and presentation, or we must accept the ultimate limitations in output for speakers of moderately high (90-96dB) efficiency. One workaround is to compromise: choose a speaker we like but has 90-96dB efficiency and/or choose an amp with greater output. I have found my PSE to be a near-ideal compromise at ~20wpc. I get 13 dB of gain which allows me to listen at 85dB (relative nearfield) and have 20dB of headroom with speakers of 92dB.

One challenge is to get the bass power we like with low powered tube amps. Most high-efficiency drivers are ill-suited for deep bass reproduction. And those that are well-suited (like big JBL drivers) still like a bit more power than their stated efficiency would suggest. My personal approach has been to focus on getting everything above 50hz right using my tube gear and turning to the brute-force method of active bass support.

I absolutely agree with your points. Furthermore, I don't think I'm missing anything if I can enjoy the larger and nicer sounding (at least in my rig) KT-77 and KT-88's (as well as others), with the nice presentation of my speakers. The 6V6 is a tube I really don't appreciate much, even in my other integrated tube amp which is purposefully designed for that tube.

The bass sub-system is a must in these low-powered but otherwise excellent Inspire units, and this is the avenue I'll be adopting after being made aware of by Peter and yourself. Having a Triode configuration makes things even more delightful for that magical mid-range, at the cost of requiring more oomph through a really balanced active SUB sub-system. In any event, once I have this SUB platform installed and dialed-in then I'll consider further power considerations, if required, which I frankly doubt.

Perhaps it would produce just 3 watts or so. I have seen single-ended triode 6V6 amps advertised as producing 4. But I don't know about the Inspire.

I'd love to have the equipment on hand to measure output. I have 4 amps I'd love to test.

I sure that there is often a difference between advertised power vs. actual output power. There are also some designers who cane the snot out of tubes to get more power but usually at the expense of some other characteristics (such as sonics or tube life). A perfect example is the venerable 300B SET. The traditional operating points provide about 8 wpc. Some designers have gotten 10 or 12 wpc from the tube, but almost everyone else returns to the sweet spot of 8 wpc.

This (http://www.enjoythemusic.com/magazine/manufacture/1108/) link includes a table showing the relative output power for different "triodes", including the triode-wired 6V6 and EL85. Both of these tubes would give an honest 5 wpc when run in SEP, but probably less than 2 wpc when run as SET. With any triode-wired beam power tube, we can reasonably expect output power to be 40% of the pentode/tetrode output power.

Dennis has provided actual test results for different tube combinations for his KT**HO series amps ( there is an image of the results buried in this thread somewhere). In the non-triode KT amps (15w OPT Version) output power ranges from 5 wpc (5Y3 6V6) to 12 wpc (5AR4 KT88). I would expect a triode-wired version to 2 wpc to 6 wpc (maybe 8 wpc for a KT88).

I know my 17wpc KT88 Inspire drives tubes hard. I probably won't get as much tube life as will those with the standard 12wpc version. I wonder if my dissatisfaction with 6V6 tubes in it could be a result of driving them harder? They sound very forward in the midrange, grating even. I've tried three different brands and they all sound pretty much the same. Given that my amp drives tubes about 40% over typical values, I'm guessing that the 6V6s are pushing close to 7wpc - given that KT88s in the standard amp produce 12wpc and are pushed to 17 in my amp. It goes that 6V6s doing 5wpc in the standard are also going to be pushed harder in mine.

Musica Amantum has gone into some lengths describing the sounds of various tubes at the stock output points in his amp. IIRC he has indicated that some tubes (KT88, KT77) seem to like "hot" operating points while others prefer to run a bit more conservatively.

Dennis' current amp lineup uses the same operating points for all tubes. It occurs to me that not all tubes will be operated in their best range. I get the feeling that getting 7 wpc from 6V6's may not be the best choice. Frankly, if I wanted 7wpc from a tube with this character I would choose a 6L6 instead.

You can always send the amp to Dennis to have it "turned down" to a normal 12 wpc version. What you will end up with is an amp that is known to sound great but has the twin advantages of extra space to fit bigger capacitors (or an IIPS with tube rectification) and output transformers with the potential for better bass. I would rather give up a couple of watts for much better sound, including the improved overload characteristics of the IIPS at power limits. You could have a really nice 10 wpc KT77 amp that would sound much bigger than it is.

However, if you want the extra power of the 17 wpc version, I would recommend the PSE instead. I don't know current pricing, but at the time I bought mine (early adopter and frequent flyer, so my price may be different than today) the PSE was about 30% higher than the 17 wpc KT88HO. The PSE, even when run at 10 wpc (parallel 6V6GT with 5Y3GT) sounds far more powerful than my KT88HO with a 5AR4 and KT88's (12 wpc).

I believe for a given (fixed) set of design tube operating conditions, there is a normal distribution between SQ (vertical Axis) and Max plate current (horizontal axis). At the center of such distribution you get the best SQ at about the mid-range of increasing max plate currents. If the operating points set is moved to the left of that curve, the sweet spot will involve the smaller (less Max plate current) tubes, like 6L6 and even 6V6. If it goes the other way, larger tubes would be best ... It is a trade-off decision based on application practicalities (otherwise, Dennis's parts inventory would grow exponentially!)

In the Triode-strapped configuration, the KT-77, and very close by the KT-88 (slightly to the right of the center in that curve), rule, given the existing operating conditions. 6L6, to the left of that curve's center, start to be sub-optimized too. Even if one has highly revealing (i.e. sensitive) speakers, other than being more audible, 6V6's, far down to the left, for example, would still not be operating optimally.

I would suggest the Opt to tube-roll and dial-in those tube specs which favor the 17 Watt Pentode design (probably farther to the right, featuring higher max plate current). I would expect less stress on larger tubes and an improved sweet-spot for that amp's given operating points. This is merely a SQ observation, not considering practicalities or SPLs.

To my ears, in my 17wpc Inspire, both KT88s and KT120s sound great. Transparent, beautiful vocals with good (not great), well-defined bass. KT66s sound pretty good too. Haven't had a chance yet to listen to my Gold Lion KT77s, the JJ KT77s have been fairly good.

Less successful, to my ears and in my system, are 6V6, 6P3S-e, 5881, EL34, 6CA7.

Give those KT-77's a listen (let them burn-in for a while, though). If these sound anywhere near my Triode Inspire in your amp, you'll really like them. Once I dialed-in the KT-77 and KT-88 with their respective ideal rectifiers and input tubes, the KT-66 and even the 6P3S-E lost plenty of ground.

Still trying to decide (if at all) between Rythmik L12 and F12 SUBs, since what I have read around seems to indicate that, in smaller rooms, single 12" driver units should have enough power. Of course, the stereo effect of 2 SUBs is even better, but non-essential. The only apparent condition is to have larger than 5" drivers in the mains (my mains have single 10" Eminence drivers, so these fulfill this caveat and is the reason I'm not considering dual 8" options yet since the Eminence drivers project nice mid-bass). This would represent the first stage of a full bass sub-system build-up, spreading the investment over time.

I'm just wondering why my Velodyne, although having a single 8" driver and only 160 Watts RMS, sounds "boomy" after a certain volume level. This weekend, I'll try to stuff the front-firing port on the Velodyne to see what happens.

Another consideration is the F12 has two options: F12 and F12G, the latter a design by GR Research, which is presumably better for cross-overs above 80 Hz. Since I use the RED MOD high pass filters at 100 Hz, does this mean the 20 Hz range difference will have better extension with the F12G?

Any further orientation from Peter, Rosco65 (to complement your great original contributions under the present perspective), or anyone else with SUB experience, would be appreciated.

Just because your Velodyne has only an 8" driver and just 160 watts, does not mean it has a flat response curve from 40-100Hz, or that it has low distortion. It could have a mid-bass bump in the 60 to 80Hz region which could make it sound boomy. Or its overall THD level might climb at a particular volume level. Some subs produce muddy bass.

Have you tested the output using a SPL meter and reference tones? I use a Radio Shack SPL meter and a Rives Audio test CD to "dial in" the crossover point and volume setting on my subwoofer.

I had Dennis put a third set of outputs on my LP-27a specifically for using subs to augment the low end and to facilitate my desire to use the LP-27a with other monoblock amplifiers such as McIntosh MC30's and Acrosound UL II's. Works like a charm.

Just to make sure again, this is how I have the SUB setup in my system:

The pair of extra outputs in my LP-27a (L + R) go into the Line-In (L + R) in the SUB (line-level connection). Then I just dial-in the cross-over knob to 100 Hz (as I have the filters at 100 Hz going into the Inspire amp). Does this sound right?

Right. I'm sort of disappointed now with the Velodyne, because the more attention I pay to it, the more I feel it does not project musical bass but a boomy sound. When my mains project mid-bass, these sound much better, but not powerful enough. Instead, the SUB makes that boomy sound which I have to keep at low volumes to avoid the "noise".

I believe the conclusion is I need a really musical SUB, but I've been hesitating to get another one and end up with the same boomy results ...

No I haven't, but I believe it is pretty easy to mix the bass volume with the mains using your ears. Also, cross-over is mathematical with the filters in the Inspire amp at 100 Hz. That is the ideal SUB range to work at with this model: 34 to 100 Hz.

I may need to find a better SUB location in the room, but since it is currently between the mains, closer to the right-hand loudspeaker, in front of the sweet-spot and aligned with both speakers' drivers plane, the booming should not exist anyway, as it is not close to any walls.

In my situation, the SUB is either booming or so quiet that it does nothing for the bass at the low volume I need to keep it to avoid that booming. I don't hear bass, but an annoying "boom boom". Ever since I implemented the filters, the mains have nicely increased their musical contributions above 100 Hz, but evidently the Inspire does not have the pep to make them play louder so the good bass above 100 Hz is there, but weak. When increasing mains' volume, mid-range and highs overcome the bass sounds above 100 Hz. If I had a musical SUB I would probably cross it at 120 Hz to fill that weak gap between 100 Hz and 120 Hz from the Inspire-supported mains. That is why I am considering a sealed Rythmik 12FG for its alleged better extension into that realm.

In any event, my SUB really sucks and the filters have made me realize this more so as the mains are much better now in the overall baseline.

Exactly.

Well, thanks for getting that out of the way :thumbsup: BTW, has anyone any experience with the other popular alternative from SVS, the SB-2000? I believe this is not servo-controlled, which is a drawback, but I've read good reviews about it.

I use a Martin Logan Dynamo 700 which fits in perfectly with my setup. Very musical and controlled. No boomy bass. For my office I have a tiny pinnacle subsonic w/dual 8"s. Sealed also. It doesn't go so low, but the bass is very tight and controlled which IMO is worth the ultra low end trade off.

Experiment more with placement. May change things significantly.

You're trying to balance the sound of a pair of high efficiency speakers with a single, ported 8" subwoofer with a 160 watt amp. My initial reaction is that you're overdriving this "subwoofer" and hearing the one-note boom of the bass port.

But let's see what we need from our subwoofer: let's say your mains are 95dB driven by a 6wpc (KT77 triode) amp. You're getting about 7dB from your amp, so you are looking at 102dB from each speaker. With two speakers you are looking at 105dB output above 100hz in your system.

Assuming the 160 watts from your Velodyne is truthful, we can expect 22dB of gain from your subwoofer amp. With a typical driver of efficiency of 85dB, we should see a maximum output of 107dB. That assumes that the specs from Velodyne are accurate, which I do not. A look at a current equivalent model does not give frequency response or specs. I can only assume that that this 8" vented subwoofer is not performing any sonic miracles. In other words, you don't have enough (or a high enough quality) subwoofer to match your Tektons. This is aside from the fact that many manufacturers have moved to sealed subs for music.

Now on to Rythmik: the F12 line comprises the F12 aluminum driver and the F12G paper driver designed by Danny Ritchie of GR research. The latter may not have the ultimate high power capability of the aluminum driver, but that is not really a concern for us. If we are crossing over higher or are trying to match paper-coned midbass drivers, the F12G would be my choice. If, like most users, you are using the subwoofer for HT (which is probably 90% of the subwoofer market) with a high-powered AVR, the aluminum cone in a vented enclosure might be a better choice.

On the L12 vs. F12G: The L12 uses an off-the-shelf paper driver that Brian describes as very light (good) in a sealed enclosure that is powered by a 300w Hypex amp with both stereo line level and mono LFE inputs. This amp is similar to that used in my F8 (using 300w per driver) and likely Peter's single-driver midbass speakers. The F12/F12G uses the class a/b A370 amp that also has speaker level inputs as well as more bass controls. Brian has indicated that the output specs of the L12 are the same as the F12.

Brian adds in a another forum's megathread about Rythmik subwoofers:

"Originally Posted by Flatliner View Post

F12G with paper cone uses a cast frame? whereas the paper cone driver in the LV12R (and L12/LV12 upcoming subs) use the less expensive stamped frame. Cast versus stamped frame is one of the things which I always considered as an indication of price level/ quality (though I'm very happy with the LV12R thus far). Aluminum versus paper cone in itself does not seem to matter as much (both have pro's and con's from what I have read on your site).

"The cast frame adds to the cost. I was a bit concerned that the stamp frame gasket may add too much coloration. However, this particular gasket that the supplier selects is heavier duty (thicker gauge steel). After i tested it against F12, it is close in terms of sound quality. I think the customers can hear the improvement too. The forumula that we have to make servo subs sound good are all in these entry level subwoofers. And from LV12/L12 to F12 you can get incremental improvement. In the ideal world, I would like to have everyone move to the D-, E- and F- series subs. But there are customers with limited budget. We need to do our best within that budget. It is a different challenge to us."

If you have a few days, I would recommend diving into the Rythmik megathread on the other forum, currentlfy at 1,018 pages.

My personal opinion:

Brian at Rythmik is probably the guy to go to for boutique high performance subwoofer at a reasonable cost. Both Louis Chochos and Jim Salk have used his products in their completed speakers. All models are of very high quality.

Now, when we add value to the equation things become even more compelling:

The Velodyne 8" ported subwoofer has an 8" driver driven by a 180 watt amp promising response to 32hz, all for $459 plus shipping.

The Rythmik L12 sealed subwoofer has a 12" driver driven by a 300 watt amp promising response to 18hz, all for $539 shipped in Conus. As a added bonus, the L12 is small enough to ship by parcel post (no doubt intentional to keep the shipping costs down).

In your case, simply replacing your Velodyne with an L12 sealed subwoofer would be a great leap forward at a bargain price. You could add a second L12 for stereo later. I am of the opinion that from a value standpoint, two L12's will cost about the same as a single F8 or F12G and would offer better performance in your case.

Two points: Your ears are probably not as good as you would like them to be when trying to dial in your subwoofers. You're flying blind and would be better using a microphone and measurement app to help you zero in. Additionally, the crossover between the sub and mains is not a brick wall filter: with 6 or 12dB/octave filters you still get a lot of output below and above the corner frequency. You may need to spread the overlap the low pass and high pass frequencies in your room and with your equipment.

Another point is to not get hung up on what you "should" be hearing and focus on what you are actually hearing. You may need to move your sub around and/or treat the room to tame some of your bass demons. I would argue that some of your boominess may be room-related and may require some specific bass trapping.

Rosco65 wrote: "In your case, simply replacing your Velodyne with an L12 sealed subwoofer would be a great leap forward at a bargain price. You could add a second L12 for stereo later. I am of the opinion that from a value standpoint, two L12's will cost about the same as a single F8 or F12G and would offer better performance in your case".

Excellent points made based on your sensible arguments. This sounds like a plan! Thanks for the thorough explanation, again.

Good points here too. My room is well-treated, with absorption and diffusers on the walls, but I lack bass traps in the upper corners. I also need to play around with the SUB at different (feasible) positions to find the less boomy location, but definitely this is a paliative until I replace it with the first L12, and eventually a second one. Thanks for your support.

When incorporating a sub into one of my systems, I set up my trusty Radio Shack analog SPL meter and then play a Stereophile CD of test tones. I usually run the scales several times - from 20Hz to 1000Hz, while adjusting my crossover point and volume levels. This can never be perfect, due to room/speaker/amp effects. I usually aim to set the sub's volume level at close to an average of 1dB below my main speakers, as I like the bass to be there, but not overwhelm.

Yes, it seems that may be the case here. I know the Velodyne I have is for HT applications and not for music, but I thought more or less these would assist in music nevertheless. I have been dissatisfied with it and unless location makes a big difference, the Velodyne will be retired. BTW, I've never heard this SUB do that low / deep vibrating thing, just bursts of boomy sounds which detract from the clean and tight mains' mid-bass work. Shame the Inspire does not have the power to make the mains' bass sound at ideal levels.

I got lucky with a cheap "sub." Picked up a little Energy "subwoofer" which has an 8" driver and about a 100 watt amp. It is really more of a woofer, as it doesn't do much below 40Hz. $40 off of Craigslist.

I use it with my Inspire SE EL84 amp, which produces almost no low bass and little mid-bass. When I set my preamp to filter sub-100Hz from going to the SE EL84 and setup the sub as described earlier, at -1dB from my average output from 100-300Hz, it does a very nice job of filling in the lower bass. Also this frees my SE EL84 from even seeing the low bass, which enables it to play louder and cleaner.

In my small system using Focal Aria 906 bookshelf speakers (approx 88dB efficiency), the 4wpc Inspire does okay when using the sub. Without the sub, not so much, easily driven into clipping on low notes. I have a pair of more efficient monitors, DIY speakers using full range Fostex FE206E banana pulp drivers. These play louder but I don't like them. Should sell them off.

Got Inspired all right!
 

Yo, does anyone actually have any luck reaching Mr. Had through his eBay channel? I gave up after trying a few different ways with no response or replies over 90 days. Originally, I wanted to buy one of his newer custom build spec Inspire amps for my smaller speakers - oh well. Since I could not reach him, decided to try and buy one of his former amps for my big speakers from back in the day when he was at Cary. Now have the Cary V-12R, wow. It's a keeper - with NOS tube and more updated coupling cap upgrades, this baby is a keeper, sounds amazing with the right speakers in Ultralinear or Triode modes. Thanks Dennis, wherever you are :)

After my tube-rolling progress during the last 6 months, I had unconsciously raised the bar so now the unfit SUB contribution has become evident. I just hope upgrading the bass sub-system will remove my dissatisfaction with the lack of oomph during demanding passages. Everything else is just great with the gear. I'm sure your point is valid, as I now believe any decent SUB by today's standards ought to outperform mine, it is just a matter of optimizing its contributions through placing and adjustments. Over time, I should try the stereo configuration to see what is all the fuzz about, but like Rosco65 stated, just replacing my SUB with a decent, capable one should make a significant difference.

Great review on that amp here:

http://www.audioreview.com/cat/ampli...2_1583crx.aspx

Of course, this is a power monster compared to the Inspire line. BTW, Dennis used to reply quite promptly in the recent past, so I could not tell why he has not replied to you yet. Congrats on your clever purchase.

Thanks Music Amantem.

Appreciate the link. Some of the base V12 and V12i units in the review were okay, and once they came out with the "V-12" with the fixes, then it became a contender according to a few folks I've met since that keep them in rotation and managed to hang on to their R models. And, picking up a nice 12/12i can be upgraded to the V-12R. I'm still playing with the different UL/Triode modes and NOS tubes. Doing some of the more modern coupling caps, hexfreds, bypass caps here in a few weeks to see if I can take it to another level. Still have a hankering for a nice little low watt SET amp too down the road. Seen a few of the DH amps come up on eBay, but I would only consider it if I could send it in and get it checked, upgraded by the creator himself. Thx.

That amp reminds me of the Mesa "Baron", a strange trip into home audio by the Mesa people. Which also makes me wonder if the maker of my fave guitar amp, a Burriss "Royal Bluesman" (it's blue), could, or would, make a stereo amp. This guitar amp is a small "lunchbox" style head that's a hand wired Class A single ended masterpiece of 18 watts…even has a spring reverb behind the face plate…maybe Dennis could make a guitar amp as I refuse to plug a guitar into the HO (maybe I should try…I can do without reverb for a few minutes).

After trying 50Hz and 70Hz High Pass Harrison FMOD's in my system I have removed them from the signal chain. Testing with a SPL meter and the Rives Audio Test CD, I found that the FMOD's lowered the input signal to my amp at frequencies above the FMOD crossover point.