Help me out Dr. Spec!

tryrrthg

can you supply me with the link where you downloaded the 1/12 octave frequency generator downloaded off the Shiva Sonotube webpage. Each tone is 10 seconds long, and the sweep ran from 10 Hz to 71 Hz?

I can't seem to find it anywhere and I don't have an email address that will allow you to send me a 7 meg file... So if you could supply the link, that would be great!

Thanks!

Dr. Spec

I'll post it when I get home - don't have it at work. I'll also give you the RS correction factors webpage.

Doc

Dr. Spec

Originally posted by Dr. Spec
I'll post it when I get home - don't have it at work. I'll also give you the RS correction factors webpage.

Doc

http://www2.markfitzsimmons.com:8000/gomer/

http://members.tripod.com/~terryctheater/shivaphotoalbum/page11.html

I have the Excel spreadsheet if you need it, which graphs your data. I even modified a version of it for the RS meter. Send me PM, and I'll give it to you.

tryrrthg

Thanks a lot Dr. Spec! I'll have to get my hands on a Radio Shack meter.

you can send me that excel file to tryrrthg@hotmail.com hopefully if will fit in my hotmail inbox. THANKS AGAIN!

Right now I have the PSW450. I am really liking what you have to say about the SVS subs. However a friend of mine owns an REL Storm III and he says (and a lot of people say) that REL works better for music... How good does SVS sound for music?

Luckily I own a pretty nice set of speakers so I don't HAVE to get a sub anytime soon, but don't tell my future wife that!

Dr. Spec

I've said it once, and I'll say it again. A great sub does everything well. If the sub has a flat FR, low THD, good transient response, deep extension, and high dynamic range, it will sound great on everything.

I would say low THD and flat FR are the two most important factors in determining how the ear perceives the musical detail from hard to reproduce stuff like an acoustic bass guitar or kettle drums. Low THD and flat FR = faithful reproduction of the input signal.

Of course, many musical bass notes have transients well into the 100 Hz and higher range, and these also greatly affect how the ear perceives the notes. The transition to the mains, and the quality of the mains is a very important and often ignored factor on evaluating "musical" bass.

I have never felt my SVS took a back seat to music - it does everything well. Subtle changes in bass texture and tone and transients are faithfully reproduced and are very natural sounding.

I have never heard REL, so I can't say. There is no Tweeter near me. REL has a good reputation, but seems very high priced for what they offer. I can't seem to find an objective review of one from an independent tester like Ferstler, Nousaine, or Johnson. I would imagine much of the carefully orchestrated REL mystique would evaporate under the harsh light of objectivity.

Bottom line - it's your money - you be the judge. I'm all about value and performance/dollar ratio. If there are any takers in upstate NY, I'll stack my $800 SVS against any single driver REL sub any day of the week in any measurable performance category and also with subjective evaluations of HT and music. When the dust settles I'll post the results win or lose. Any takers?

Dr. Spec

BTW, I'll forward those Excel files to you when I get home tonight. You definitely need the correction factors for the low bass FR sweeps.

I would imagine the PSW450 will have an in room F3 of around 32 Hz. I had dual PSW350s at one time and I liked them for anything above 35 Hz. Below that, they are totally outclassed by the single SVS.

There is no substitute for cubic inches and flat extension to below 20 Hz - the difference between the two subs is amazing at anything below 35 Hz. The SVS plays notes the Polks completely ignored - and it does it with such effortless authority it's hard to describe. There is a whole world of sound below 30 Hz that many, many enthusiasts have never heard properly reproduced. I thought the extension of my Polks was fine for HT until I demo'd a bunch of really top end subs. Man was I wrong.

Most recent revelation: Black Hawk Down - "Irene". An HTF member measured strong content to 8 Hz with an RTA sound analyzer on copter lift off when the whiskey glass is shaking.

I am flat to 11 Hz with one port plugged and the SS filter set to 12 Hz. I normally run all three ports open and the SS filter set to 20 Hz for safe loud playback. But for the "Irene" scene, I tuned it to 11 Hz and cut loose at a loud (but not too loud) playback - WOW! There is some amazing subsonic stuff down there!

Before and after testing showed an average SPL increase of 3 dB at the same master volume setting with the lower tune. You can't hear it, but you can sure feel it. Cone excursion gets really extreme below the tuning point, so I had to be careful, but that was scene was worth it! Good stuff!!

tryrrthg

Thanks again! You've always got great reads about bass response! the only real problem I have with SVS is the subs are so ugly! I wish they would make an affordable sub that can be stained to the buyers liking... I think that is the BEST idea I've seen yet!

I've been looking DIY subs all morning and really wish I could try this and not waste my money. I like the way REL looks (plain box, nice wood, downward firing woofer). I just like the idea of being able to make the sub look like I want it to... I've been adire audio's site all morning looking at their CAD diagrams for Shiva and Tempest subs. How do you think these would stack up to SVS?

http://www.adireaudio.com/tech_papers/shiva_apps.htm

http://www.adireaudio.com/tech_papers/tempest_apps.htm

Dr. Spec

The Adire is excellent stuff. The best value out there hands down is DIY.

You can build an Adire that will outperform an SVS. In fact, the Tempest in a properly vented enclosure with a 750w amp would probably beat a CS+ or Ultra. The xMax of the Tempest is "only" 16 mm, but it's a big cone and moves a LOT of air, as Ron-P will attest.

I doubt the Shiva would outperform the TC Sounds dB-12 or TV-12 driver - I noticed they are not listed in the Shiva's competitor's box - there may be a reason why :-). The Shiva is probably a very close match to the SVS ISD in the CS and PCi line.

If I was going DIY, I wouldn't eff around - my driver would be the Tumult - hands down no questions asked.

But the Shiva or the Tempest in your own properly built and tuned enclosure will provide excellent bass for very little money. Adire is top shelf stuff and used my MANY DIY enthusiasts.

Also, the new Stryke AV12 or AV15 by TC Sounds are worth a very hard look and I think would offer an edge over the Shiva and Tempest - at least on paper with xMax and Vd.

tryrrthg

They've got some great deals at the Stryke audio web site on the AV15 and a 350 watt plate amp...

Question: so would the AV15 (or any other 15" driver) work in the enclosure on pages 9-11 on this file? or is it just for the Tempest?

http://www.adireaudio.com/Files/VentedTempestApplications.PDF

I've proably got some major learning to do before I could take on a project like this...

Dr. Spec

Originally posted by tryrrthg
They've got some great deals at the Stryke audio web site on the AV15 and a 350 watt plate amp...

Question: so would the AV15 (or any other 15" driver) work in the enclosure on pages 9-11 on this file? or is it just for the Tempest?

http://www.adireaudio.com/Files/VentedTempestApplications.PDF

I've proably got some major learning to do before I could take on a project like this...

The T/S parameters need to be the same. I haven't checked them - you can do that. I wouldn't substitute drivers without checking with Adire and Stryke. The Tempest is a fine woofer - I'd use it with the Adire enclosure without hesitation.

Doc

Dr. Spec

Also, go here and check out their partially and fully finished box subs. They carry the Adire and Stryke lines also.

http://www.acoustic-visions.com/index.htm

phoneisbusy

Originally posted by Dr. Spec


http://www2.markfitzsimmons.com:8000/gomer/

http://members.tripod.com/~terryctheater/shivaphotoalbum/page11.html

I have the Excel spreadsheet if you need it, which graphs your data. I even modified a version of it for the RS meter. Send me PM, and I'll give it to you.

Dr. Spec,

Thanks for posting the URLs. the markfitzsimmons.com url doesn't seem to work for me. Is the link working for you? If so, I'll have to see if there's something wonky with the internet connection at work...

I'm guessing the site has the test tones in mp3/wav format for burning to a CD?

regards

Dave

Dr. Spec

I just tried your posted link and it works fine. There is a hotlink on that page called "1/12 octave.zip". Download that file to your hard drive (6 meg) and then unzip it. It contains 41 mp3 files in 1/12 octave increments from 10-100 Hz, each one 10 seconds long. Burn all the files to a CD (keep track of their order), and you're off to the races.

I made my disc to the 100 Hz tone burns first, then it goes from 10-94 after that. Reason being, you can set a reference volume at 100 Hz through the mains, and then evaluate not only your FR, but also your transition to the mains from the sub. It will reveal any phase problems at the filter point. It will also show you the true volume differential between the mains and the sub better than a single test tone will.

phoneisbusy

Originally posted by Dr. Spec
I just tried your posted link and it works fine. There is a hotlink on that page called "1/12 octave.zip". Download that file to your hard drive (6 meg) and then unzip it. It contains 41 mp3 files in 1/12 octave increments from 10-100 Hz, each one 10 seconds long. Burn all the files to a CD (keep track of their order), and you're off to the races.

I made my disc to the 100 Hz tone burns first, then it goes from 10-94 after that. Reason being, you can set a reference volume at 100 Hz through the mains, and then evaluate not only your FR, but also your transition to the mains from the sub. It will reveal any phase problems at the filter point. It will also show you the true volume differential between the mains and the sub better than a single test tone will.

Got it. Had to get a friend to grab it for me.

Thanks again!

Dave

tryrrthg

Where can I get a variable crossover for a DIY sub that will let me crossover lower than 40hz? my sub would be mostly for music and I only want the sub to fill in the low end. my main speakers can get into the high 30hz's just fine, I need the sub to start from there... Any help?

Dr. Spec

Getting into the high 30's at high volumes is a completely different story.

FR curves are run at low volumes and look very different at high volumes. The smaller drivers in most mains have trouble filling a room at say 40 Hz with power you can feel. I'd go higher than 40 - maybe 70 or 80. What mains are you using?

hoosier21

Originally posted by tryrrthg
Where can I get a variable crossover for a DIY sub that will let me crossover lower than 40hz?

Paradigm has a unit called the X-30, it's lowest point is 35hz, it can be had on the ney (used) for 100.00-130.00. It is the unit made for their Servo-15, nice little package. I have two of these and never used either, I hope to put them to use on my second DIY sub project this spring.

tryrrthg

Thanks guys!

I have Dynaudio 1.3mkII's, they can crank out some pretty impressive bass for their size...

The only subs I can find that crossover that low are REL. A friend of mine has the Dynaudio 1.3SE (almost the same speaker as mine) and an REL Storm III. he has his crossover set in the high 20hz's...

Dr. Spec

I would run a low volume FR sweep on the mains to see where they start to actually roll off.

Note the F3 point and repeat the sweep at a higher volume (representative of your anticipated playback levels - whatever that is) and see if the F3 is the same and if the speaks can handle it without apparent strain.

A word of caution, at the higher anticipated playback volume you can really heat up the VC's on a continuous sweep, so I would terminate each tone immediately after I obtained a steady reading and let the VC's cool for 30 seconds between tones, just to be safe.

Once you have determined the actual F3 of the mains at the anticipated playback volume, I would low pass the sub a bit higher than that point for a smooth transition. The SPL of the mains and the sub should be the same just above and just below the filter point, respectively.

Arbitrarily selecting a lower-than-normal filter point for the sub without actually seeing what the mains are capable of could possibly create a hole in the FR.

tryrrthg

Thanks! That's kind of what I was thinking... I haven't gotten to run the frequency sweep on my mains yet because my CD burner died over the weekend. I had to order a new one...

I guess I'm not as worried about finding a sub that will blend with my standmounts as I am worried that a few years down the road I'd like to have some nice floor standing speakers. They will hit much lower and will need a crossover from a sub that can get into the high 20's. of course after I get a better sub I may like the sub/standmount combo and never go back to floorstanding speakers...

thanks again guys!