a lot depends on the actual driver itself. Negative output resistance and cancellation of the voice coil resistance will certainly reduce suspension and box compliance non linearities but as Bl runs out of steam at the extremes of excursion, distortion could be a lot worse.
Taking the biggest number there, that's a bit less than 4m, 2 doublings of distance: 102dB at 1m; 96, 2m; 90dB at 4m. So, speaker working at 102db, if 90dB sensitivity need 16W to be pumped into it by the amp, nothing very scary about that, decent speakers are rated 10 times that.
And that's being generous - 4m is getting well down the room, lots of room reflections should give above the 90dB listening position level.
Frank
Nothing scary perhaps... advertized power ratings are meaningless unless a pro/archetectual spec from a standard measurement method. However, the thd is higher than often expected. period. When I asked JBL for distortion numbers, they would not give it to me. saying there is no standard that is adhered to by all.
Just as likely they didnt want to scare people not used to seeing high distortion... besides being used to compare with others' numbers which were not done under similar conditions.
Play with the numbers but in a large room volume and on the dead side and 86-88db eff and see what you get. I mean actually do it... yes, get up from the arm chair and measure driver distortion at loud listening levels in the real home. tell me what you get. I would like to know which have the lowest distortion. makers giving T-S and a few numbers and freq response is avoiding the problem of high distortion in their drivers. There seems to be some debate with thd and audibility with speakers. The effect of motional feedback is more than thd, its damping and freq response and who knows what else that is audible. For another time. back to JC and special tests beyond Im/THD... take it away, John.
Last edited:
I bow to your proof. I hope my citing AES etc was not misconstrued as denying such important truths.It's not about Wavebourn's symptoms, but about Wavebourn's proof that speakers generate audible distortions that increase with excursion.
Even completely blind person can't deny the fact when hears a sub, while in case of woofers can stubbornly cite AES and similar gurus.
But I just realised your sub is a horn built into the floor. I've only had experience of one such system in da old days so this is much more interesting then Marshy's 2x15" units. (sorry Mr. Marsh)
What is the design cutoff? Flare? The mouth diameter? Do you have a back chamber?
Coming back to your -ve resistance .. Does it reduce the distortion you hear on the 10Hz with increasing level?
Genuine questions all. Not trying to make any point but hoping to learn.
Genuine questions all. Not trying to make any point but hoping to learn.
Before I can tell you any specific details Richard you have to listen and decide if you like it or not. Many things are made against common rules of dumbs.
The big old JBL units with Alnico magnets had some of the lowest distortion at high levels I know of. Dunno what's good today.
Have you got a target spl & distortion? What size is the room?
Wave's criteria, that you shouldn't be able to hear the sub when the sofa is shaking and the walls rattling is actually quite a good one. Even holds at 50Hz.
Do you actually need 10Hz at high level? Going from 16Hz to 10Hz is VERY expensive in size & power requirements. There are good musical reasons for high level 16Hz cos 32' organ stops.
Also do consider stereo subs.
In a cathedral, when the organist dances on the pedals, you feel the bass flow through you. Your trousers might flap but its not unpleasant. Using mono subs, as with most HT systems, converts the pleasant trouser flapping particle velocity to unpleasant "pressure in the head" sensations.
Of course very few recordings capture this properly but you can with a Mk4 Calrec Soundfield or TetraMic.
target
My abode was designed and build to commercial standards. Steel I-beams used to tie the main room together, for example. It is rock solid. about 30' by 13' and ceiling is sloped from 13 -18 feet high. Nothing much vibrates unless it is me.
I dont need 10Hz. I want -3db at 30Hz - clean and strong. No compression at listening levels.
Id love to help get more recordings done with Soundfield system!!
I have stereo subs. I have now 4- 15 inch cerwin vega on the bass. Subs for below 40-50Hz will be two 18 inchers (TC Sounds 5400 Ultra.... with 3KW digital amp for them - so they claim). With electronic crossovers and seperate amps on everything, I should have the freq extension, dynamic range and accuracy with low distortion drives (below 0.1% at loud levels... 90+ db), I'll be a happy camper to the end of my days on this cosmic speck of dust. But it aint easy... but I'm getting there. Maybe going to try planar/ribbon array drivers for the range 180Hz and above if they are low distortion with dynamic range. Only because the HiFiman headphones (HE500) sound so darn good... compared to the Sennheiser (HD800). I would like to have low driver distortion as much as possible... I dont care all that much for the masking issues or how sensitive one is to H2 et al. Those are real hearing phenoms but for myself, those discussions only help maintain the status quo with driver development. Thx-RNM
My abode was designed and build to commercial standards. Steel I-beams used to tie the main room together, for example. It is rock solid. about 30' by 13' and ceiling is sloped from 13 -18 feet high. Nothing much vibrates unless it is me.
I dont need 10Hz. I want -3db at 30Hz - clean and strong. No compression at listening levels.
Id love to help get more recordings done with Soundfield system!!
I have stereo subs. I have now 4- 15 inch cerwin vega on the bass. Subs for below 40-50Hz will be two 18 inchers (TC Sounds 5400 Ultra.... with 3KW digital amp for them - so they claim). With electronic crossovers and seperate amps on everything, I should have the freq extension, dynamic range and accuracy with low distortion drives (below 0.1% at loud levels... 90+ db), I'll be a happy camper to the end of my days on this cosmic speck of dust. But it aint easy... but I'm getting there. Maybe going to try planar/ribbon array drivers for the range 180Hz and above if they are low distortion with dynamic range. Only because the HiFiman headphones (HE500) sound so darn good... compared to the Sennheiser (HD800). I would like to have low driver distortion as much as possible... I dont care all that much for the masking issues or how sensitive one is to H2 et al. Those are real hearing phenoms but for myself, those discussions only help maintain the status quo with driver development. Thx-RNM
Last edited:
That's a big room if a trifle narrow. Good for the ELS63s though I gather your priorities are not in the direction of their strengths.
Well the Celestion A3s or Duntech Sovereigns might play music to your satisfaction in that room but certainly can't compete for HT.
How are the 15"s & 18"s mounted? I would be tempted to wall or ceiling mount (provided the ceiling is solid) and use the whole roof space as the box. Stereo subs can share the space provided they themselves are spaced. At those frequencies and in that room, corner ceiling mounting is probably best.
If you do ceiling mount, make provisions to physically turn the drive units over regularly. They will creep over time. Turning them over will give audibly less distortion for a while.
Are you doing your own electroic xover & EQ? Might be better to run the 15"s & 18"s in parallel below 50Hz rather than crossing over.
Wave, its called Blumlein fig-8s at 90. Have a look for organ recordings on ambisonia. Can you arrange stereo subs?
Do you hear a difference in distortion at 10Hz when you switch the -ve resistance in/out on your system? I'm really interested in the details as this will probably double my knowledge of such systems.
Alas, I won't be able to come & hear it soon but I hope to before I die. Thanks for the invitation.
As a contrast, and I've mentioned it before, this is one of the better captures of a good system working the room well: Manfrotto FIG RIG 595B test video - REY AUDIO RM-7V in KENRICK SOUND showroom - YouTube.
Frank
Good luck with that, John! This is a public forum where discussion is encouraged.Perhaps a blog would better fit your needs?
I think there are quite a few of us who are listening . . . we might just be making less noise.
Personally I'm getting towards the point where I've tried all the stuff that is intellectually obvious so if I want to make further progress with my audio design I have to get into the esoteric stuff
Mikelm, I am glad that someone is listening. Actually, I learn a lot from others, and some here have put their time and money where their opinions are. More than me, in my old age, and with my apartment.
Still, I can hear small differences in electronics that defy straightforward measurement.
To do this, I use my STAX Lambda Pro headphones with a direct coupled vacuum tube based headphone amp. I recently used this set-up to evaluate a new product for a famous client. The STAX beat out Sennheiser, Grado, Audeze (barely), and Denon headphones priced up to $1000.
AND, I can still hear differences in seemingly almost identical circuits.
This is very useful for me, but I have to admit, that I could hear a lot better, 40 years ago. The STAX headphones make it possible for me to still hear these differences, as these headphones were also the ones that originally showed me what the Bybee Purifiers were all about, and the limitations of Alps pots (even though I still use them, myself, in my less exotic products) for example.
Whatever difference I hear, it is beyond the measurements that I can easily do, and I can measure IM or Harmonic to about 1 part in 1 million, with noise averaging to remove the residual noise, and I can accurately note the whole harmonic spread. I really think that is low enough for THAT sort of test.
Still, there must be SOMETHING that will measure the differences in two line stages (for example) and give me direct evidence of why one sounds better than another. I'm open to serious suggestions.
Still, I can hear small differences in electronics that defy straightforward measurement.
To do this, I use my STAX Lambda Pro headphones with a direct coupled vacuum tube based headphone amp. I recently used this set-up to evaluate a new product for a famous client. The STAX beat out Sennheiser, Grado, Audeze (barely), and Denon headphones priced up to $1000.
AND, I can still hear differences in seemingly almost identical circuits.
This is very useful for me, but I have to admit, that I could hear a lot better, 40 years ago. The STAX headphones make it possible for me to still hear these differences, as these headphones were also the ones that originally showed me what the Bybee Purifiers were all about, and the limitations of Alps pots (even though I still use them, myself, in my less exotic products) for example.
Whatever difference I hear, it is beyond the measurements that I can easily do, and I can measure IM or Harmonic to about 1 part in 1 million, with noise averaging to remove the residual noise, and I can accurately note the whole harmonic spread. I really think that is low enough for THAT sort of test.
Still, there must be SOMETHING that will measure the differences in two line stages (for example) and give me direct evidence of why one sounds better than another. I'm open to serious suggestions.
That's the reason why i run horns at home. Other examples:
audiopavillon enceintes hi-fi francaises hr percus duo de pavillons avant garde de 68cm horn - YouTube
Modern Horn Speakers played Excerpt from The Nutcracker Suite - YouTube
PIONEER EXCLUSIVE model 2402 Special Polished Walnut Sunburst 2 - YouTube
Yes, the dynamics are there, first step taken care of; however, even through the deficiencies of YouTube playback I can hear the next problem that has to be knocked over, the "oversharpness" of the treble, as some may call it. Which is why a lot of people pull back from this sort of replay - it's not a problem with using horns per se but the fact that the easy dynamics exposes more vividly the underlying system distortions ...
Frank
I envy you your sophisticated real world measuring equipment.
When designing with the aid of spice I always test fourier up to H20 and I have noticed that if spice predicts that H10 - H20 is around -130db it sounds much better than if spice predicts H10 - H20 is only -100db !
I am very curious to know just how low you can engineer your actual H10 - H20 power amp levels in real life and what you regard as sufficiently low ( beyond which no further improvement can be heard ).
I am current aiming between -125db to -150db in spice. (edit - but I have no idea how this translates in real life )
mike
p.s. Pity I sold my stax phones 30 years ago !
Last edited:
John, seriously, we all do. The important word is "small".
Have-you listened to the links i had provided to recordings of some audio enclosures outputs ? In front of such a disaster, don't you believe we can focus our attention to something else than "sound of cables" ?
Listening "small differences", there is a moment where we invent them.
I run a Rotel RC 850 preamp. (because it has all the commutations i need) I have changed the electronic inside, using current feed-back op amps with a high speed booster able to drive a loudspeaker, and resistance arrays to tune the volume. When it is near impossible to make the difference with a strait wire, what i have to worry more about ?
With all the money saved, comparing with some "high end" products, i can work on the acoustical treatment of my room and my enclosures. And more important than all, buy records.
Absolutly agree. I had suppressed any tweeter on my 2 way system, and worked a lot to remove all the harshness and nasal effects of the horn. I use wooden spherical horns, it goes up to 16Kz very flat and in a very credible (natural) way.
You can notice, in the pioneer video, that, moving the mike's camera, there is a moment where the female voice is absolutely natural.
That what i'm now looking for, instead of impressive high trebles or deep basses. Easy listening, separation between instrument, high instant dynamic (ease) and less room's effects as possible. Nothing can beat good (rare) horns in that quest when you have suppressed the 'duck' effects.
I was very interested by those bad recordings, as they reveal instant all the huge problems of each systems: peaks in high and trebles, induced room resonances etc. without to be impressed and biased by the high volumes or beauty of some details...
Will use this kind of test intensively for my future mods.
- Status
- Not open for further replies.