Post by: Michael Fraioli on January 24, 2006, 03:40:45 PM
Im new here so if i posted this in the wrong spot or anythign sorry you can yell at me. anyways. I am looking to build a sub cabinet size is not to much of an issue but i dont want some more then 300lbs. I want to build a cabinet that can hit somewhere areound the 20hz range on up to maybe 100 very most anyone have any good designs or things to consider for me to do this. i realize i need a sub and an amp that will drop to that level without losing -10db so im just looking for some help and suggestions since you all are the pros here thanks anyone who can help
Post by: Antone Atmarama Bajor on January 24, 2006, 07:48:09 PM
And what SPL level do you want at 20Hz (1/2 space)?
It Cost me~ 1000$ to build two of my BS-212 subs. A pair are capable of reproducing 20Hz @ ~117dB @ 1000W 1m. They measure 23 5/16" Deep x 40 13/16" Tall x 24 1/4" wide. They could be made smaller but I wanted to play with differential Driver loading to reduce even order Harmonic distortion so part of the outer dimension is caused by a recessed area in the face.
http://srforums.prosoundweb.com/index.php/m/80905/8490/?SQ=b b0e5b8a95b673c0d1fdaf63b0007716
http://srforums.prosoundweb.com/index.php/m/82403/8490/?SQ=3 21e52d2824847ab1b4342c2215b062e
There are other good driver options that would require much larger cabinets. The BS-212 was designed to go as low as possible but also be reasonably portable. I haven't weighed them but I doubt they are over 200lbs.
It would take 4 of them to come close to the output as 1 Danley soundlabs DTS-20 at 20Hz and require 2X the power. The cost difference would probably be made up in amplifier dollars spent except it will take you a long time to build your own.
http://www.danleysoundlabs.com/DTS20.html
What is your application?
Sealed subs using a linkwitz transform or dual integrator EQ Can go very low with relatively low distortion, but maximum SPL is limited.
The average Horn sub would be Unmanageably large.
The same is true for most reflex cabs and group delay gets pretty extreme around resonance the lower you try to go.
Passive Radiators have really weird phase and group delay issues. I don't think its very easy for the average DIYer to build an optimal passive Radiator.
If you don't mind building some Huge 40cu ft cabs the Adire Tumults and maybe the Acoupower drivers are good but expensive options.
I still think for convenience of cabinet size and cost the LAB12 drivers are still the best bang for the buck.
Good luck!
Antone-
Post by: Weogo Reed on January 24, 2006, 09:05:38 PM
You could simply buy some Danley TH-20s :
http://www.danleysoundlabs.com/DTS20.html
Good health, Weogo
Post by: Antone Atmarama Bajor on January 25, 2006, 01:24:45 PM
!Antone-
Post by: Michael Fraioli on January 27, 2006, 04:52:37 PM
Post by: Michael Fraioli on January 27, 2006, 04:57:18 PM
Post by: John Chiara on January 27, 2006, 05:16:52 PM
| Michael Fraioli wrote on Fri, 27 January 2006 16:52 |
well thanks for the help the danley sub seems great and im interested in purchasing it but more then 7 feet tall damn thats a lil big. Be honest with u all i am putting this in my 14'x16'and celing is 8ft bedroom i know this is excessive yatta yatta yatta but i liek my music loud period. i looked at this subs specs and it didnt seem to require that much power 500w rms which i could use just a crown xls202 in bridge mono mode you can pick those up for $225. im not really looking for 4 subs or i would consider your design 1 or 2 subs of any size would be great im trying to keep the enclosure no more then 36"wide 36" deep and maybe 5'-6' tall any more ideas or references anyone has? |
You can lay the DTS 20 on its side.
Post by: Antone Atmarama Bajor on January 27, 2006, 05:53:48 PM
If you want to achieve full scale cinema LFE headroom to 20Hz (-3 to 6dB @ 30Hz normally). You would need banded pink noise at about 95dB at listening position (in the LFE range with 20dB of headroom). If you wanted to reproduce 20Hz -3dB from full scale you would need 112dB at 20Hz at listening position available. Listening position maybe only 1 meter from the sub and room gain may give added sensitivity in the sub octaves.
A pair of Labs in a vented cab may just get you there if you are sitting 1 meter from them. Most people won't be doing that.
The mains center and surrounds need to be 85dB banded pink with 20dB headroom at listening position. But how many people listen to movies full scale at home in their bedroom?
I'm getting ready to build my friend a Dual lab Sealed sub using a likwitz transform I should be able to get 104dB @ 20Hz, 1/4 space loaded into his cinder-block wall I should get ~110dB @ 20Hz. A pair 1/4 space loaded should get 116dB @ 20Hz
1 driver aiming forward and one aiming at the floor mounted in the box differentially. The primary enclosure needs to be a well stuffed 14.78" Cube (internal dimensions) I'm making it 24" tall to get the Magnet of the backwards down firing woofer off the floor.
Cost of the 2 drivers ~300$ 3/4 or 1" MDF ~ 30$. You would need either a linkwitz transform circuit made for it www.linkwitzlab.com (He has a spreadsheet for designing the appropriate circuit), or play with some parametric filters, or get or make a Dual integrator ELF type circuit (This will limit your Flat response upper end to whatever the cabs box resonance is so not really appropriate for an LFE application)
If you just want your setup for music I don't think you'll find much source material with significant recorded energy bellow the upper 30's of Hz. Especially older recordings.
Good luck whatever you plan on doing.
Antone-
Post by: Ivan Beaver on January 27, 2006, 09:39:43 PM
Post by: Antone Atmarama Bajor on January 29, 2006, 03:25:15 PM
I think a pair or more of lab 12s in a sealed enclosure would be much more cost effective an a lot smaller you could build a dual integrator circuit for them really easily. In fact I think the guy who runs the ESP audio website has a schematic for one there.
I think the main concept behind the Infra/Elf system is that they want to operate the driver bellow box resonance so that it doesn't color the sound and THD is supposedly low. And the Dual integrator is supposed to exhibit only a mild phase shift Vs. using other types of filters.
Does anyone here know how different the phase shift between and integrator and a linkwitz transform circuit is???
Antone-
Post by: Michael Fraioli on January 31, 2006, 10:14:49 AM
Post by: Michael Fraioli on January 31, 2006, 10:34:33 AM
Post by: Michael Fraioli on January 31, 2006, 01:23:35 PM
Post by: Antone Atmarama Bajor on January 31, 2006, 03:07:11 PM
1 Adire 18" on the other hand should be able to produce 20Hz at 110 dB in a 5cu' sealed Sub. Again you would need a linkwitz transform or some type of specialized EQ to flatten the response. Of course room gain and boundary loading can change things to an extent.
The output would be about the same as making two of dual 12" Lab subs in a sealed cab. 1 Adire 18" costs about the Same as 4 Labs.
You would want the labs clustered together not separated by any distance greater than 1/3 a wavelength of its operating bandwidth.
The Adires are nice subs though. Just pricey.
Antone-
Post by: peter.golde on January 31, 2006, 03:07:30 PM
http://home.comcast.net/~infinitelybaffled/
Post by: Antone Atmarama Bajor on January 31, 2006, 03:18:33 PM
Dont forget to Dampen your Rafters.
Antone-
Post by: Dave Rickard on February 01, 2006, 02:13:33 PM
| Michael Fraioli wrote on Tue, 31 January 2006 08:14 |
haha yes i realize you can lay it on its side who wants something 7 ft long laying across there room |
Buy a pair and use them for your bedframe! Or a single and adapt your current frame.
A massaging bed!!!
Post by: Michael Fraioli on February 01, 2006, 02:50:07 PM
Post by: Michael Fraioli on February 01, 2006, 02:55:02 PM
Post by: Mark Seaton on February 01, 2006, 05:58:14 PM
| Antone Atmarama Bajor wrote on Tue, 31 January 2006 14:07 |
I wouldn't bother with the ADIRE 12" its extra power handling and XMAX doesn't make up for how much less sensitivity it has than the LAB 12 And its more than 2X the price. 1 Adire 18" on the other hand should be able to produce 20Hz at 110 dB in a 5cu' sealed Sub. Again you would need a linkwitz transform or some type of specialized EQ to flatten the response. Of course room gain and boundary loading can change things to an extent. The output would be about the same as making two of dual 12" Lab subs in a sealed cab. 1 Adire 18" costs about the Same as 4 Labs. |
This isn't quite right. The Tumult 18" will have more than 2x the volume displacement of a pair of LAB12s. In other words, for displacement you're looking at 1 Tumult = 4 LAB12s.
The high power density and relative cost of the LAB12 make it a very potent performer in most any "loaded" design like a reflex, including passive radiator, and of course a proper horn. For a sealed design, there are many other options out there. Parts Express seems to have some of the best deals right now, with a few others offering some good value at higher performance levels.
If really interested in playing around in the 20Hz range, check out some of the home theater related sites and forums. 20Hz in the home is more of an expectation than a novelty of high performance systems. Other than a few of Danley's offerings or a truckload of Bag End subs, the pro market is pretty weak below 35Hz, let alone 25Hz.
I'll post a separate reply to Michael directly.
Post by: Mark Seaton on February 01, 2006, 06:14:38 PM
| Michael Fraioli wrote on Wed, 01 February 2006 13:50 |
well that dont sound half bad these lab subs are sounding better and better so 20 hz at a 2 meter listening position at around 115db round about with an enclosure no bigger then 36" wide 60" tall and 36" deep how many subs what size and what series would i need? and what kind of amp and eq do you recommend with it? do u have specs or links to any of this? and any idea how to build the box maybe a cad drawing or some thing hand drawn and scanned in so i know how to build this beast? thanks antone big help! |
Hi Michael,
First, your question is relates more to home theater than to pro-audio. In the confines of your small room, it won't be hard to get pretty serious output to 20Hz. You did mention a budget of ~$1200? That does start imposing some limits and narrowing things down. There are a couple of subs from online manufacturers which will deliver decent 20Hz output for that sort of money. SVS's PB12-Plus/2 or Hsu's soon to be released VTF-HO would likely be the easiest routes, although 2 or more of the SVS cylindar subs might also fit the budget.
You have also talked about DIY. If you are willing to build, and especially if you are willing to make a decent size box, that will certainly give you the most bang/buck. Parts Express have a variety of 12 & 15 inch drivers in their Dayton family that could work great for very reasonable price, and they even have some nice plate amps for startlingly cheap $/W.
For what you describe, use multiple drivers so you don't have to worry about power handling. From there, you could go with 2-8 drivers depending on your fancy. Best bang for buck would be a pair of 15" drivers in the right size box. If you have to keep the size down, most of the 12" drivers will be beter suited to what you want. In a small room like you have, I would lean towards 4 12" or 2 15" drivers in sealed boxes with appropriate EQ. Having Smaart you are a long way ahead of many others making the EQ option much more useful.
I suggest you look through this forum and see if some of the projects there give you some ideas. If you can make some decisions as to what size and costs you can live with, I'm sure they can help you out, and I swing through when I can as well:
HT Guide Forum: Mission Possible DIY
Hope this helps.
Post by: Dave Rickard on February 01, 2006, 06:48:10 PM
| Michael Fraioli wrote on Wed, 01 February 2006 12:55 |
but i dono if would help u in coming up with a design for me if ud be so kind...or maybe there is a design already out there? |
Post here. Good guys, good advice.
http://www.pesupport.com/cgi-bin/config.pl
Dave
Post by: Michael Fraioli on February 02, 2006, 09:06:03 AM
Post by: Dave Rickard on February 02, 2006, 10:56:40 AM
First the suggestions are too big, now they're too expensive, yada, yada... TANSTAAFL!!! (google that)
Go to the Parts Express forum and ask. Ask for measurements, they've got them.
Dave
Post by: Mark Seaton on February 02, 2006, 01:56:08 PM
| Michael Fraioli wrote on Thu, 02 February 2006 08:06 |
you keep reffering to going to home audio but i have yet to find any home audio products that giuve you any sort of specs that are worth a shit. i have an infinity alpha1200 right now it says it plays down to 29hz...umm yeah maybe at -10db but they dont even give you those type of specs so its a shot in the dark thats y i think pro audio is the way to go so i can see exactly how the sub will perform before i waste my money on it. im seriously considering antones ideas and goin with the lab subs they are in my price budget not to large of an enclosure and from the specs he had mentioned they sound what i am looking for now i just need to have some design so i can build the cabinet |
The majority of retail manufacturers are just starting to catch up with real performance quantification. I've personally been quite involved toward that end on the home theater front since I started working with Tom Danley maybe 5 years ago now. Head over to AVS Forum and see all the discussion about measurements and real performance in the Subwoofer forum. The hi-fi audio sector is still blissfully ignorant of what's happening with the serious home theater installations. Unfortunately the jewelery like hi-fi stereo market gets more press. Serious contractors, installers and designers are operating on a level that you will never be exposed to in most retailers spare a few.
For examples of real measurements, check out the article that really led the pack: Way Down Deep, Ultimate AV Magazine - Keith Yates
Keith designs some of the highest performance home theaters in existence. He did this article more as a survey to collect more data for his design work, and offered to do it as a 3 part article with Ultimate AV just before they went web only. There were also 2-3 parts in Home Theater Magazine on some less expensive subwoofers. Among probably a dozen more very highly respected people, both Tom Danley and myself gave input on the test methods. A little input from everyone was taken into account, although there is a limit to how much data they could present in print and what the public was ready to digest.
When I provided the link to the HT Guide at the end of the last post, realize that is hardly a "hi-fi" or just home theater forum. Those are serious DIYers, some of which employ 12, 12" subwoofers or 18, 15" woofers in large infinite baffle designs. They value measurements and expect real performance, even if a few have slightly esoteric tastes.
The SVS products currently offer one of the best alternatives to DIY for under $2k. They were in fact spawned from two DIYers building sonotube based subwoofer designs. In a few months I will have a first subwoofer in production as well that will be quite potent with a pair of sealed 15" drivers and ~1500W. While I feel it will offer a great value, it will be above your intended price range at $1995 just as the DTS-20 (I had some input on that package & design goals before Tom made it reality - originally conceived for Home Theater) is out of your intended price range. All of these have a good deal of performance data available with a bit of searching. Generally much more useful and meaningful information than you will find in common professional data and spec sheets.
The founders of SVS, myself, Keith Yates's report linked above, and a handful of others have been pushing reviewers to expand the data provided. We also can't forget the past reviews done by Don Keele and Tom Nousaine who both provided insight into the real performance of subwoofers. More recently a member of some of the forums I mentioned had started measuring and posting his results on the forums. His methods have evolved, and he was then asked to be a reviewer for Secrets of Home Theater and Hi Fidelity, and online publication. Check out how far his current reviews have come: Product Review: SVS PB12-Plus Subwoofer
If you are inclined towards the DIY realm, and you don't put a dollar value on your time invested, with a little research you can easily exceed the performance of most anything you can buy for 2x the parts cost. You obviously trade off the certainty in what you will be getting unless you copy the design of another. If this is the route you are interested in, start looking at how large a box or boxes you are willing to deal with and ask for options with that available volume, room size, and general budget range. If you follow some input from the forums, it is unlikely you will not be very impressed.
Regards,
Post by: Gareth James on February 02, 2006, 09:27:04 PM
You say the Danley DTS-20 is too tall at 7', but a LABsub would be ok... The DTS-20 is tall but has a small footprint at 17" square, you could stand it in a corner or lay it down the side of a wall as suggested.
The LABsub is likely to fill most of your room by the sounds, its footprint is around 4 times that of the DTS-20 and no amount of moving it round is going to change the fact it takes a lot of space.
You also mention you are looking to spend no more than 1000 dollars on amp and sub, in which case i don't think the labsub or dts-20 are within your reach.
I would definitely recommend looking at infinite baffle designs within your budget area.
Good luck!
Post by: Antone Atmarama Bajor on February 03, 2006, 06:24:17 AM
A sub built with the LAB 12 Driver. Its a great driver for the price.
As Mark Seaton. pointed out Dayton also makes some decent inexpensive drivers. I think one of them measures almost the same as the Lab 12 and is cheaper. I would model it against the labs but my hard drive with all of my modeling software on it died so until I reinstall Its not happening.
I'm just a babe in the woods when it comes to a lot of speaker stuff. Mark and many others here have a bit more Real world Experience than I. So their advice is more than valid.
I have never personally investigated an (not so) infinite baffle design but not everyone has the option to cut holes in their walls or Ceiling. And I don't think efficiency, Linearity of response, power bandwidth, or phase response/group delay is improved so why would you do it? But I don't know this so prove me wrong.
I wouldn't say that the Sealed Lab 12 box is Pro Audio even though the driver was designed for a very specific pro audio application. It would take too many to reach pro SPL levels to be practical.
I have not built the sealed box that I have been talking about yet but I am about too. I have done the modeling I can give internal volumes and basic dimensions. I choose to build differential so it makes design a little more cumbersome I suppose. But you don't have too.
Did you say you wanted to achieve 20Hz at 115dB @ 2 Meters? That may take 4 sealed Dual 12 Cabs. Depending on your room gain. As you loose 6dB every doubling of distance or is it 3dB indoors? Though you may have 12dB per octave room gain starting at 40Hz that means 20Hz will be 12dB louder at 1 meter Plus the 1/4 space loading gain. So some of it depends.
In an infinite room with a perfect wall floor intersection 4 sealed dual Lab 12 subs you would have 125dB RMS 20Hz @ 1 Meter. Of course no room boundary or speaker is perfect. And you will probably get more gain @ 20Hz depending on room.
Anyhow I'm tired MSG me and I'll try and get you the specifics. Also read the forums that Mark linked you too. And the infinite baffle stuff.
I'm not sure which 15 Mark suggests. The Adire is pretty cool for some applications. The Adire 18 is cool too but les maneuverable.
Educate your self the best you can and make an informed decision because noting can be more important than rattling your neighbors teeth!
Antone-
Post by: Antone Atmarama Bajor on February 03, 2006, 06:39:01 AM
I will have to do my full power sweeps but I suspect the
BS-212 has a much lower THD across the board too. Maybe I should send Keith a pair. But I already know that Tom has everyone licked with his DTS-20 (I do want to see the THD and group delay/phase data though).
Unfortunately my nice large open field is now a Swamp so I can't do any good tests until it drys for a month or so.
Too bad they're too big for the average living room.
Antone-
Post by: Michael Fraioli on February 16, 2006, 08:14:40 AM
Post by: Antone Atmarama Bajor on February 16, 2006, 05:13:50 PM
I'll try and set one up for you (and the lab community) with all of the dimensions.
I don't know if I should try and set things up to prevent the design to be used by others for profit.
If anyone has any idea how I set up a limited public domain copyright situation let me know.
The BS-212 is rather large still a sealed sub would need a little more support equipment to flatten its response.
As far as amplifiers go. I'm not sure what to recommend I'm trying to figure out if I'm having Issues with my Alesis Matica 900 I get some funny popping happening while playing Bass through them or LFE signals. I've been having good results with the AB amplifier we have in my shop I've never made the drivers pop or chunk and thunk with the AB. But I need to make more thorough tests. I could just be overexcurding the driver.
Hopefully I can get everything ready in the next couple of days.
There is much room for improvement. I didn't to any butt joints everything is screws and glue blocks. I used wood flooring adhesive so the joints would maintain flexibility while working with it.
Get you the info soon.
Antone-
Post by: Too Tall (Curtis H. List) on February 22, 2006, 03:31:49 PM
| Michael Fraioli wrote on Fri, 27 January 2006 16:52 |
well thanks for the help the danley sub seems great and im interested in purchasing it but more then 7 feet tall damn thats a lil big. Be honest with u all i am putting this in my 14'x16'and celing is 8ft bedroom i know this is excessive yatta yatta yatta but i liek my music loud period. i looked at this subs specs and it didnt seem to require that much power 500w rms which i could use just a crown xls202 in bridge mono mode you can pick those up for $225. im not really looking for 4 subs or i would consider your design 1 or 2 subs of any size would be great im trying to keep the enclosure no more then 36"wide 36" deep and maybe 5'-6' tall any more ideas or references anyone has? |
If you want to put it in the attic you need to look here-
http://ibsubwoofers.proboards51.com/
Post by: Mark Coward on March 01, 2006, 11:27:51 AM
http://www.billfitzmaurice.com/plans/product_info.php/produc ts_id/23?osCsid=c8742cac94abb4cf9eadc660b99b742a
Some guys are using these for PA subs too, loaded with the Eminence HL10c which is sort of like a 10" LAB sub. Should be able to build these for around $200 per cab for driver and materials, maybe a little more depending on how you want to finish them.
Forum here:
http://audioroundtable.com/BillFitzmaurice/
Post by: Michael Fraioli on March 01, 2006, 12:58:50 PM
Post by: Duane Massey on March 01, 2006, 05:34:31 PM
Post by: Joe Jones on March 02, 2006, 05:53:41 PM
Post by: Ivan Beaver on March 02, 2006, 07:32:47 PM
You don't get something for nothing.
Post by: Duane Massey on March 03, 2006, 01:11:09 AM
Post by: Joe Jones on March 03, 2006, 09:46:06 AM
| Quote: |
In the aforementioned example, to get the 20Hz to be as loud as the higher freq, you will be delivering over 10 watts to the driver. |
Obviously, but so what, if both the woofer and the amp are able to do that with headroom to spare, which they can. 110dB at 20 Hz is do-able with 100 watts, but that's at least 10dB higher than I'd expect to go before every item in my house not nailed or glued down would have fallen on the floor and a good deal of the ceiling and wall plaster too. 10 watts is enough to get it done. More than that brings to mind jokes involving Dolly Parton.
| Quote: |
I don't think anybody publishes specs of their sub with an EQ dialed in (except maybe someone who spec'd a processor as part of the whole system, which is not what most of us here are interested in). |
Look around the JBL, Meyer,EAW,Turbosound or just about any high end site and look at the top of the line systems. For the tops few of them have any charts, and the one's that do are with processing becasue they won't work without it. Most of them don't show any charts at all for subs.
Post by: Tom Danley on March 03, 2006, 12:19:33 PM
You have hit on one of the more “sad” situations in audio, many of the largest companies seem to participate too (I.M.O.)
On the other hand, you have to understand, this isn’t like medicine where a life in the balance and you get in trouble for selling “BS” (alternately, Bad Sound).
If you were a Madison Ave. type, knowing that the average buyer goes by numbers and reputation what would you do?
I mean if by careful presentation, one could give the impression that your product were 10 or 100 or more times more powerful that it really was, would you present the numbers that way?
Obviously artful presentation is cheaper than R&D or a new idea and that leaves more budget for building a reputation through advertising & image building etc.
A few common practices, which I think, are questionable.
For example, by measuring a subwoofer to several hundred Hz or even higher, one can get a much higher sensitivity than is present in the subwoofer range (where it is used).
This is a common practice.
By stating a 1 Meter sensitivity as an unqualified number, one is in theory providing the output of the speaker where its used, based on input power and response, yet this common practice essentially negates this possibility of this being accurate.
A similar situation is often true for what + - 3 dB and – 10dB means when you measure real products and compare to the data sheets.
By stating a sensitivity as above and using DSP or EQ to correct the response, one takes a step further from knowing how much the speaker can do.
Take the case of an imaginary speaker.
It has a sensitivity of 110dB 1 W 1M, (which is the figure at its highest at 400Hz).
At 40Hz, lets say it is really 95dB, a mere 15 dB less or 1/30 the output of what the spec would suggest.
So now one see’s a measured response flat to 40Hz and stated sensitivity of 110dB one assumes that with a rated 1000W, one could get to 30dB + 110dB = 140dB.
Most companies go on to assume that since the rated power pink noise signal has peaks that are +6 over the average level, that the peak output is 146 dB, see, all the math adds up.
In reality, assuming no excursion limiting or power compression, you really have 95dB + 30dB for a maximum output of 125 dB at 40Hz and if one actually measures the real SPL with a peak hold meter, one finds the actual peak SPL is usually around 1/100 the acoustic power one calcualtes.
Again, this is the common, if they are honest, they will say Max SPL “calculated”.
Your right too, room for these “errors” largely goes away “IF” a measured response curve is given, made in standard repeatable condition.
It makes it easy to look at any frequency and say “the sensitivity at 40Hz is X” and the –3 dB point is Y.
The reason this is not the norm in what otherwise likes to think of itself, as a “technical industry” is pretty obvious, the room for this kind of monkey business goes away.
Tom Danley
Post by: Duane Massey on March 03, 2006, 12:26:04 PM
Most of the commercially available vented and band-pass subs are not particularly impressive. The DIY'ers on this forum are typically looking for a better performance, but there's a lot of disparity on what that really means.
For some, 20hz at 125db in their living room is the holy grail. For others, 30hz at 110db at 30 meters is the moving target.
Regardless, it's all about the cabinet, not the electronics.
Post by: John Roberts {JR} on March 03, 2006, 02:41:47 PM
| Tom Danley wrote on Fri, 03 March 2006 11:19 |
Hi Joe You have hit on one of the more “sad” situations in audio, many of the largest companies seem to participate too (I.M.O.) On the other hand, you have to understand, this isn’t like medicine where a life in the balance and you get in trouble for selling “BS” (alternately, Bad Sound). If you were a Madison Ave. type, knowing that the average buyer goes by numbers and reputation what would you do? I mean if by careful presentation, one could give the impression that your product were 10 or 100 or more times more powerful that it really was, would you present the numbers that way? Obviously artful presentation is cheaper than R&D or a new idea and that leaves more budget for building a reputation through advertising & image building etc. A few common practices, which I think, are questionable. For example, by measuring a subwoofer to several hundred Hz or even higher, one can get a much higher sensitivity than is present in the subwoofer range (where it is used). This is a common practice. By stating a 1 Meter sensitivity as an unqualified number, one is in theory providing the output of the speaker where its used, based on input power and response, yet this common practice essentially negates this possibility of this being accurate. A similar situation is often true for what + - 3 dB and – 10dB means when you measure real products and compare to the data sheets. By stating a sensitivity as above and using DSP or EQ to correct the response, one takes a step further from knowing how much the speaker can do. Take the case of an imaginary speaker. It has a sensitivity of 110dB 1 W 1M, (which is the figure at its highest at 400Hz). At 40Hz, lets say it is really 95dB, a mere 15 dB less or 1/30 the output of what the spec would suggest. So now one see’s a measured response flat to 40Hz and stated sensitivity of 110dB one assumes that with a rated 1000W, one could get to 30dB + 110dB = 140dB. Most companies go on to assume that since the rated power pink noise signal has peaks that are +6 over the average level, that the peak output is 146 dB, see, all the math adds up. In reality, assuming no excursion limiting or power compression, you really have 95dB + 30dB for a maximum output of 125 dB at 40Hz and if one actually measures the real SPL with a peak hold meter, one finds the actual peak SPL is usually around 1/100 the acoustic power one calcualtes. Again, this is the common, if they are honest, they will say Max SPL “calculated”. Your right too, room for these “errors” largely goes away “IF” a measured response curve is given, made in standard repeatable condition. It makes it easy to look at any frequency and say “the sensitivity at 40Hz is X” and the –3 dB point is Y. The reason this is not the norm in what otherwise likes to think of itself, as a “technical industry” is pretty obvious, the room for this kind of monkey business goes away. Tom Danley |
At the risk of sounding like an apologist for the status quo or diverting the blame away from the merchandiser.... consumers by their buying behavior strongly reward such questionable marketing practices.
In most cases the consumers don't posses the skill set to properly evaluate raw specifications or much interest to acquire those skills. In general they will buy what they perceive is a good value based on a historical reputation and a superficial comparison of some presumably comparable specifications.
I believe all reputable (?) companies invest time and energy in trying to present meaningful, comparable specs. There is often a catch 22 where companies are afraid (for good reason) to look like they losing in a direct comparison to a major competitor. While a salesman who is prepared with supporting explanations and a customer willing to listen can overcome such apparent but not real misses on a specification, in the larger flow of business the opportunity to educate and correct such flawed interpretations rarely presents.
The manufacturer to survive must both make an excellent product, and do make sure the product also "looks good" in spec sheet comparisons. This can become a circular finger pointing exercise with few willing to be the lonely, and sure to lose sales, honest man. This can be even harder for companies with solid engineering but a weaker reputation. In that case presenting specifications more conservatively than competitors will surely be interpreted as a lesser performing product.
In the case of transducers (speakers and microphones) being able to evaluate specifications is IMO rather important as these are the weakest link in SR. Even the best loudspeakers involve engineering tradeoffs or compromises to dial in the loudspeaker for a target application. i.e. a great studio monitor, is different than a great FOH cabinet for solo use, vs FOH cabinets for arraying... etc.
Consumers are advised to invest what little attention span they are willing to spend on learning about loudspeaker tradeoffs and how to read specifications important for their applications. IMO this will be far better use of their precious (to them) time than yet another un-scientific power amp, or mic preamp shootout.
Stepping down from soapbox now.
JR
PS: BTW, a good start is to read every word written by Mr. Danley.
Post by: Joe Jones on March 03, 2006, 03:15:11 PM
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Joe, that's the idea of this forum. Most of us are interested in subs that don't require such radical processing. The idea is for the cabinet to do all the work, not the woofer. It's not difficult with today's technology to take any box with a woofer that can pass 20hz (even at 15db down) and smooth out the response to a +/-1db flat line, but you give up so much in dynamic range that it's not very practical for serious applications, not to mention the fact that you'll be beating the crap out of the woofer. |
Duane, you should go back a ways and re-read the thread, especially this:
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Yes well you must have missed one of the replies where i said the bedroom its going in is about 14'x 16' haha |
I agree that you do have to use the right tool for the job at hand, that's why I gig with four Tuba 36s, but I'm sure not going to use them in my livingroom, which is about the same size as his. I thought the idea of this forum was to offer advice, and I don't think that should be limited to telling the guy he has to put four Labs in his bedroom or that he can only get what he wants by spending two thousand bucks. Other options exist.
Post by: Duane Massey on March 03, 2006, 04:37:40 PM
I would agree that most manufacturers do go to a great deal of time and expense to document their products, but there has been a common tendency to omit the less-flattering numbers and "dumbing-down" the printed specs. There is no industry standard, and never has been. Even the 1w/1m is suspect, because there is really not a common way of measuring this.
That's one of the benefits I am gaining from this forum; I will be doing some testing on some cabinets in the next 3-4 weeks, and I will be asking for suggestions on what methods are preferred by most sound people. Numbers don't mean a whole lot if you can't compare the same test results.