Hi, its been a while last time i posted here
Recently i made a DIY project. i wanted to have speakers like the 4351 from Kenrik's
So i made some with what i had.
I picked up Goldwood GW15PC-4, strictly because the specs on paper was convincing and relatively similar to the JBL 2235h. i know, i know, they are cheap woofers and there isnt much to believe in, but anyway, this is what i had, they where cheap and easy to get.
So
I entered the parameters into WINISD and builded the enclosure accordingly.
Front/back is 1" mdf, sides are multiply 18mm veneer. all braced inside, very strong. glued and screwed. i didnt cheaped on this part.
I followed what win isd told me
about 11ft3 and a tuning FS of 30hz
that made 6x 3" port of about 8.5" long
which is almost the same "close" basic dimensions as a 4350/4351 when compared so in my head i was not far from something that would work
They play loud and clean, it moves tons of bass in the house (powered byt a BGW7000)
But i had some doubts abut the Goldwoods and their published specs. Altough they play tons of bass, i feel that it is not as expected.
Cross over took me 2 year to calculate, test, design and build. lets focus on the bass section plz.
I recently bought a DATS V3. I took the woofers out and promply tested them. Turns out that with broken in woofers, the VAS has almost doubled. published spec is 4.4ft3 and the DATS measures 6.5ft3
I then mesured the sweep impedance to test the FS
it came out as 22hz !!
i know some times a woofer with a high Q can have the enclosure FS tuned below speaker FS...but 22hz i think its quite low
I then decided to shave a bit the ports
i shaved around -2inches on the 6 of them into one enclosure and came with a FS of 25....still far from the WINISD predicted 30hz.
i re-measured many times the internal volume and i am 100% dead sure it is 11.5ft3.
moderate 1" dacron on the walls
picture: measurement of the FS before shaving off the ports. and the speaker enclosure itself.
should i leave them this way ?
am i right to aim at raising a bit the FS to flaten out the frequency response from 30hz and up ?
how come the final FS is so low ?
What should i believe in, the goldwood specs, the DATS V3 ? WINISD ?
thanks for any guidance (or not if you think they are ok like that)
Recently i made a DIY project. i wanted to have speakers like the 4351 from Kenrik's
So i made some with what i had.
I picked up Goldwood GW15PC-4, strictly because the specs on paper was convincing and relatively similar to the JBL 2235h. i know, i know, they are cheap woofers and there isnt much to believe in, but anyway, this is what i had, they where cheap and easy to get.
So
I entered the parameters into WINISD and builded the enclosure accordingly.
Front/back is 1" mdf, sides are multiply 18mm veneer. all braced inside, very strong. glued and screwed. i didnt cheaped on this part.
I followed what win isd told me
about 11ft3 and a tuning FS of 30hz
that made 6x 3" port of about 8.5" long
which is almost the same "close" basic dimensions as a 4350/4351 when compared so in my head i was not far from something that would work
They play loud and clean, it moves tons of bass in the house (powered byt a BGW7000)
But i had some doubts abut the Goldwoods and their published specs. Altough they play tons of bass, i feel that it is not as expected.
Cross over took me 2 year to calculate, test, design and build. lets focus on the bass section plz.
I recently bought a DATS V3. I took the woofers out and promply tested them. Turns out that with broken in woofers, the VAS has almost doubled. published spec is 4.4ft3 and the DATS measures 6.5ft3
I then mesured the sweep impedance to test the FS
it came out as 22hz !!
i know some times a woofer with a high Q can have the enclosure FS tuned below speaker FS...but 22hz i think its quite low
I then decided to shave a bit the ports
i shaved around -2inches on the 6 of them into one enclosure and came with a FS of 25....still far from the WINISD predicted 30hz.
i re-measured many times the internal volume and i am 100% dead sure it is 11.5ft3.
moderate 1" dacron on the walls
picture: measurement of the FS before shaving off the ports. and the speaker enclosure itself.
should i leave them this way ?
am i right to aim at raising a bit the FS to flaten out the frequency response from 30hz and up ?
how come the final FS is so low ?
What should i believe in, the goldwood specs, the DATS V3 ? WINISD ?
thanks for any guidance (or not if you think they are ok like that)
DATS guesses the TS from the impedance curve (ref: the author). It also collapes the T/S curves in a different, much less useful, place than teh factory.
Usable for matching drivers i would not use the number sit provides to do the loudspeaker design.
And i understnd (never used it), recommends an alignment. Did you look at other possibilities, i wouldn’t trust WinISD to choose.
How does your build sound?
The mid, tweeter, and super tweeter should be as close as possible. and if not in a vertical array you want to build mirror imaged pairs.
dave
i never ever said i used dats to make my speaker. i bought it many month after i made them.
i try to make correlation about the final FS of my enclosure, and in between the manufacturer TS, what WINISD suggested me to do and what dats tells me.
mid and tweets has nothing to do here about my question. i dont know why you tell me about that ?!??
i try to make correlation about the final FS of my enclosure, and in between the manufacturer TS, what WINISD suggested me to do and what dats tells me.
mid and tweets has nothing to do here about my question. i dont know why you tell me about that ?!??
PatAllen ... I'd just keep cutting the ports till you get what you like. The difference between the predicted port length and reality has do with the actual driver parameters in the enclosure and that WinISD uses a "flared one end" default when it calculates port length. You're past all of that anyway. Just keep cutting till the FR is what you can live with in room. The enclosure is tuned low now ... sounds like you want it tuned higher. Take another inch off each port.
I don*t know DATS, but measuring TSP is usualy not a real problem. You can do it with some wire, a resistor and a multimeter.
If you have "strange" drivers from the low budget class, better measure both or all 4 of them.
An fs lower than 25 Hz for a driver with such an suspension seems odd. You rather except something like 40Hz.
Do you have a measuring microphone? This may give some idea what is happening, too.
PS with TSP measuring programs the calibration and the (real!) static resistance of the voice coil are critical. Things often go wrong with these.
If you have "strange" drivers from the low budget class, better measure both or all 4 of them.
An fs lower than 25 Hz for a driver with such an suspension seems odd. You rather except something like 40Hz.
Do you have a measuring microphone? This may give some idea what is happening, too.
PS with TSP measuring programs the calibration and the (real!) static resistance of the voice coil are critical. Things often go wrong with these.
i have an old spectrum analyser that i am carrying on since the early 90's whan i was doing car audio (sa3050, it went to the CES and 12v show few times with me lool...when its batteries where still keeping up) , many scope, generators and whats not...the only missing link is REW (which i am about to get soon)
thoses speakers are rated from manufacturer at 33hz fs...they measure 30 after beign broken in a lot. its the only measure thing i am 100% sure about.
before i had DATs i measured it myself with my generator, scope and limiting resistor just like you said...no big deal. they came at 30hz, same as DATS tells me
theses speakers can really move tons of bass, dont get me wrong. i am experiencing, thats it. i thought that DATS would tell me a bit more about what i did but at the end it just confuses me more. i just dont know why it went to a 22HZ fs while winisd told me i would do 30 with the volume and port size/lengts
22hz for a bass reflex like that was a bit low imho, maybe funny in a house like mine, but i really aimed at 30hz. i shaved the ports from their initial 11 inches down to 8 now down to 7, and its at 27hz now. it sounds less "dull" id say...
lo vas olvidar makes the whole house move on its basement i can tell you.
thoses speakers are rated from manufacturer at 33hz fs...they measure 30 after beign broken in a lot. its the only measure thing i am 100% sure about.
before i had DATs i measured it myself with my generator, scope and limiting resistor just like you said...no big deal. they came at 30hz, same as DATS tells me
theses speakers can really move tons of bass, dont get me wrong. i am experiencing, thats it. i thought that DATS would tell me a bit more about what i did but at the end it just confuses me more. i just dont know why it went to a 22HZ fs while winisd told me i would do 30 with the volume and port size/lengts
22hz for a bass reflex like that was a bit low imho, maybe funny in a house like mine, but i really aimed at 30hz. i shaved the ports from their initial 11 inches down to 8 now down to 7, and its at 27hz now. it sounds less "dull" id say...
lo vas olvidar makes the whole house move on its basement i can tell you.
Hi Pat,
I think the last two posts may give you what you need moving forward. But I wanted to point out what seems to be some confusion in your terminology, which makes it hard to know exactly what you need help with.
The VAS probably never changed. If you did not measure them before, they were probably different from the published specs to begin with. Note, even if VAS is off the other TS parameters may be off too and the box modelling still may come out to be close. (Of course this isn't always the case - I had a Tang Band driver where the difference between published specs and actuals made a signfificant difference in the needed cabinet volume.)
Fs is a TS parameter of the driver (Free-air resonance) and is unrelated to the box.
I think you mean Fb - which is the typical notation for the frequency of the box tuning. Note, the tuning of the box is unrelated to the driver. However, you can tell what the tuning is by looking at the point between the peaks of the impedance curve - which is what you have done above.
Note, you have two issues.
1. The tuning of the box is not what you thought it was, if you want to change it you need to change your port length. This is unrelated to the driver you are using.
2. The TS parameters are not what you thought they were based on the published specs. Therefore, the Fb you were aiming for may not be the Fb that you really want now that you know the actual TS parameters. So before you mess with the port length trying to get Fb to your original target of 30Hz, you should put the actual TS parameters into WinISD and re-model it.
DATS V3 measures TS parameters, WinISD does not. WinISD takes the TS parameters (from DATS or published specs) and allows you to determine your desired box model (transfer function, box tuning, etc.). If you put in accurate inputs (i.e., actual parameters from DATS) then WinISD can generate accurate ouputs. WinISD has always given me very accurate estimates including port lengths for the desired box tuning.
I think the last two posts may give you what you need moving forward. But I wanted to point out what seems to be some confusion in your terminology, which makes it hard to know exactly what you need help with.
The VAS probably never changed. If you did not measure them before, they were probably different from the published specs to begin with. Note, even if VAS is off the other TS parameters may be off too and the box modelling still may come out to be close. (Of course this isn't always the case - I had a Tang Band driver where the difference between published specs and actuals made a signfificant difference in the needed cabinet volume.)
Fs is a TS parameter of the driver (Free-air resonance) and is unrelated to the box.
I think you mean Fb - which is the typical notation for the frequency of the box tuning. Note, the tuning of the box is unrelated to the driver. However, you can tell what the tuning is by looking at the point between the peaks of the impedance curve - which is what you have done above.
Note, you have two issues.
1. The tuning of the box is not what you thought it was, if you want to change it you need to change your port length. This is unrelated to the driver you are using.
2. The TS parameters are not what you thought they were based on the published specs. Therefore, the Fb you were aiming for may not be the Fb that you really want now that you know the actual TS parameters. So before you mess with the port length trying to get Fb to your original target of 30Hz, you should put the actual TS parameters into WinISD and re-model it.
You should believe in the actual DATS V3 TS parameters over published specs. DATS V3 is quite accurate. (Vas can be a bit tricky, but as long as you are doing things right, DATS is good.)
DATS V3 measures TS parameters, WinISD does not. WinISD takes the TS parameters (from DATS or published specs) and allows you to determine your desired box model (transfer function, box tuning, etc.). If you put in accurate inputs (i.e., actual parameters from DATS) then WinISD can generate accurate ouputs. WinISD has always given me very accurate estimates including port lengths for the desired box tuning.
i really meant to talk about the tuning of the box itself from what win isd told me. sorry if it wasnt clear but i believe my explainations where. but now i realise that this program by default use flared ends which may explain a lot why i am having always lower box FB (not fs sorry).
fwiw i dont have OCD....i can make difference in between what DATS and WIN does, ie one measure and one not.
fwiw i dont have OCD....i can make difference in between what DATS and WIN does, ie one measure and one not.
one other aspect of my own confusion is, once i measured the speakers (all 4 of them), the TS paramerers where quite off...once entered into WIN it got red flaged as if there where something wrong.
the expected/calculated VAS from WINISD was "ok" 4.4ft3 but from the DATS measurements it was like 6+ so as soon as i entered manualy the vas in WINISD and checked data accuracy it got red tagged...so it confuses me, either DATS is wrong, or WINISD...the woofer itself just throw out to dats what it really is i believe. what do you think ?
the expected/calculated VAS from WINISD was "ok" 4.4ft3 but from the DATS measurements it was like 6+ so as soon as i entered manualy the vas in WINISD and checked data accuracy it got red tagged...so it confuses me, either DATS is wrong, or WINISD...the woofer itself just throw out to dats what it really is i believe. what do you think ?
Yes, but teh default isn't a huge flare like a precision port. I would think the difference in port length due to the default flare vs no flare would be pretty small - like 1/4" or 1/2" (?)
WinISD has some accuracy checks on the TS parameters to a few decimal places of precision. Many are related by mathematical formulas, so if you know two of them, then the third should follow mathematically. If you are entering in with one or two decimals of precision, then it might get flagged. The best way is to turn "auto-calculate unkowns" on and enter the minimal number of parameters needed. Look at this tutuorial ( https://midwestaudio.club/resources/winisd-a-beginners-tutorial/ ), about 1/3 of the way down, and it recommends the following order.
- I enter either diameter (Dd) or radiating area (Sd)
- I enter the drivers DC resistance (Re)
- I enter the drivers Qes
- I enter the drivers Qms
- I enter the drivers Vas
- I enter the drivers Fs
- enter the drivers Xmax
WinISD has improved a lot over time and the predictions are quite exact. If the input data don't fit reality, the simulation suffers. WinISD does not know how solid and air tight your cabinet is, for example.
The good thing about vented cabinets is the option to tune the ports. So if the simulation is not spot on, you can simply change this parameter. Some say you always have to do some small changes, no matter how good the simulation is.
So a flared or straight cut port is not that important in the end. Flared ports are more a band aid for too narrow ports and can prevent noise if air velocity get's too high. Nice to have but not needed in any case. WinISD gives quite practical values for ports.
If you have a microphone, (it does not have to be expensive) near field measurements of cone and port will give you an idea how near you are to your desired optimum. The more you measure, the more you will realize how these data match up to what you hear.
Some of the downsides may become options, if you look close. With a microphone you can match the port tuning to your room, this will result in a better response than a speaker optimized for the free field or the anechoic chamber.
The good thing about vented cabinets is the option to tune the ports. So if the simulation is not spot on, you can simply change this parameter. Some say you always have to do some small changes, no matter how good the simulation is.
So a flared or straight cut port is not that important in the end. Flared ports are more a band aid for too narrow ports and can prevent noise if air velocity get's too high. Nice to have but not needed in any case. WinISD gives quite practical values for ports.
If you have a microphone, (it does not have to be expensive) near field measurements of cone and port will give you an idea how near you are to your desired optimum. The more you measure, the more you will realize how these data match up to what you hear.
Some of the downsides may become options, if you look close. With a microphone you can match the port tuning to your room, this will result in a better response than a speaker optimized for the free field or the anechoic chamber.
the predictions where matching the data sheet of the speaker, but not the DATS ones, specifically the VAS. as soon as a manipulate the vas it get red flaged, 0 or 9 digits doesnt matter. i had quite a lot of arguments with the guy at Parts express about the goldwood and the potential inacuracy of the (already spoken for on other forums and on their own web site) bad or false TS, at the end i had to tweak the SD and the cms value to "comply" with the original values...i dont really agree with that "lets do freaking guesses and rule of broken thumb" method while we have tools, suposedely factory measurement and judgment.....i hate thoses Goldwood since day one, maybe i am biased.
Just had a look at the data for the Goldwood speaker chassis. The data are from 2003... 20 years old. All to common... I even found data sheets from 1997 in 2022 offers at other places.
This is a known problem with long time produced Chinese products. They are build from the cheapest parts and materials the factory can source in the darkest parts of Asia.
You can be sure that not even a single part of such a chassis today will be the from the same source it came from in 2003. A Chinese manager does not even understand why this could make any difference, as he has no clue what he is building and selling or how physics around it work. "Look good, make cheap" is all Mr. China boss knows, "very good copy from famous speaker", "we sell quick". Trust me, this is the reality.
Make no mistake, these Chinese products can work quite well if used right, but don't expect any continuity, like you have been used to if buying JBL or EV or Scandinavian chassis.
Anything, like magnet material, cone pulp, even glue and iron for the magnet assemply, they all change driver parameter. The late that produced the inside parts will be CNC controlled today, not hand adjusted as 20 years ago. So tollerances are quite different today. At least one thing got better...
The "Goldwood" trade company doesn't care for what they sell as well, otherwise they would measure any new lot for consistancy and could easily update the data. They make about 60$ on every chassis they sell to you for $120, so measuring one piece a year is too expensive from such little profit. Takes about 15 minutes done right, but there is no one qualified enough in such companies. They don't even know if they sell a good product or complete junk.
So, yes, you can buy cheap drivers, you may find a pearl, but check data by making your own measurements. From each driver you buy and maybe return them if identical ones measure completely different.
This is a known problem with long time produced Chinese products. They are build from the cheapest parts and materials the factory can source in the darkest parts of Asia.
You can be sure that not even a single part of such a chassis today will be the from the same source it came from in 2003. A Chinese manager does not even understand why this could make any difference, as he has no clue what he is building and selling or how physics around it work. "Look good, make cheap" is all Mr. China boss knows, "very good copy from famous speaker", "we sell quick". Trust me, this is the reality.
Make no mistake, these Chinese products can work quite well if used right, but don't expect any continuity, like you have been used to if buying JBL or EV or Scandinavian chassis.
Anything, like magnet material, cone pulp, even glue and iron for the magnet assemply, they all change driver parameter. The late that produced the inside parts will be CNC controlled today, not hand adjusted as 20 years ago. So tollerances are quite different today. At least one thing got better...
The "Goldwood" trade company doesn't care for what they sell as well, otherwise they would measure any new lot for consistancy and could easily update the data. They make about 60$ on every chassis they sell to you for $120, so measuring one piece a year is too expensive from such little profit. Takes about 15 minutes done right, but there is no one qualified enough in such companies. They don't even know if they sell a good product or complete junk.
So, yes, you can buy cheap drivers, you may find a pearl, but check data by making your own measurements. From each driver you buy and maybe return them if identical ones measure completely different.
hi, what do you have in mind about the microphone ? ihave an SA3050A spectrum analyser, but by todays standard it is quite old and unprecise since the display uses LEDS....is there a way i can measure the port velocity or anything else i am missing other than measuring at 1m ? thanks
i just can more than agree with you about the Goldwoods and their cheap characteristics...i am poor and made the project with them, that doesnt mean i have to stick with them i can buy something else to make the project "better"....fwiw i took one of my old JBL 2225H, 100% original, never reconed and in like new condition and tested it with the DATS, the result is schoking, most if not all data matches 100% the 1983 spec sheet from JBL....good stuf back then i guess....
Have you ever used REW or Arta? There are many measurments that will give you an idea how your speaker works and how you can improve it to match your situation. All you need is a microphone you probably already have. REW is the most easy to use IMO.
Measuring very close to the chassis and port will tell you about the result of the tune in the cabinet.
On the other side, in room response shows how all of that works out in your situation. Your audible impressions will get a readable base to improve things. Even the most linear speaker can give quite bumpy, unfavorable response if it interacts with the room. So you may advance from tuning a chassis to a cabinet to tuning the speaker to the room, This makes more sense for the final result.
Measuring very close to the chassis and port will tell you about the result of the tune in the cabinet.
On the other side, in room response shows how all of that works out in your situation. Your audible impressions will get a readable base to improve things. Even the most linear speaker can give quite bumpy, unfavorable response if it interacts with the room. So you may advance from tuning a chassis to a cabinet to tuning the speaker to the room, This makes more sense for the final result.
Hi, no i dont use rew, the mic i have is a xlr phantom powered mic, so there is no way for now to connect it to my pc or laptop unless i buy an expensive adaptor so i am about to get a usb mic and eventualy REW .
two things i consider in short term
1-system will get bi-amped, with a variable crossover. this will give me more freedom to adjust and tune it all.
2-i am about to drop the money to get locally cheap JBL 2225J/H that needs recone, and thus will get reconed in 2235H. Will toss away the Goldwoods. I want 2235H since the begining so....this wont be cheap either.
today i will try to stuff things into one cabinet to shave some internal volume and see how the FB is affected. Maybe my calculations or the net internal volume is much bigger than anticipated, plus the dacron filling,...things needs to ger adjusted i guess. i still need to understand why my FB is/was 22hz instead of 30 (per WINISD simulation)
thanks....
two things i consider in short term
1-system will get bi-amped, with a variable crossover. this will give me more freedom to adjust and tune it all.
2-i am about to drop the money to get locally cheap JBL 2225J/H that needs recone, and thus will get reconed in 2235H. Will toss away the Goldwoods. I want 2235H since the begining so....this wont be cheap either.
today i will try to stuff things into one cabinet to shave some internal volume and see how the FB is affected. Maybe my calculations or the net internal volume is much bigger than anticipated, plus the dacron filling,...things needs to ger adjusted i guess. i still need to understand why my FB is/was 22hz instead of 30 (per WINISD simulation)
thanks....
I suppose you got a laptop with a phone out and a microphone in. You sure have a connection wire with these small 3.5 mm stereo jack connectors at both sides. Install REW, plug the cable into mic in and phone out for a loop test and start with the calibration (right upper hand "preferences"). You will get an idea how it works and how simple it is.
If you still have an old laptop around, that seems too slow, installing a cheap SSD should speed it up like 200%. If this fit's for you, look for a tutorial and use a well known SSD brand. A 20$ 120Gb from Amazon should do. Win 7 will be fine, just don't use it for the internet any more.
For a microphone:
There are various USB audio interfaces which support phantom powered xlr directly.
This plus your old mic is more universal than a USB microphone. Even as the USB mic is usually simpler on first sight. Maybe read a little about it and decide what suits you best.
A new USB interface with 48V should start around $70. I would advise to get a better model, but used if you don't mind.
The problem with these devices is not the function, but the driver support. It depends on which Windows version (or Mac) you use for measuring and your audio stuff.
I can recommend FOCUSRITE products, a "Scarlet 2i2" from the first series is perfect for anything audio, as they have very good driver support.
So if you go this way, PLEASE first check driver situation, then buy. If you have an older laptop running Win7 (just for audio) like me, you have less problems.
Get information about the driver support of and how it works BEFORE you buy. I can not emphasize this enough. With a bad or wrong driver you will waste endless time. Ask me how I know...
If you still have an old laptop around, that seems too slow, installing a cheap SSD should speed it up like 200%. If this fit's for you, look for a tutorial and use a well known SSD brand. A 20$ 120Gb from Amazon should do. Win 7 will be fine, just don't use it for the internet any more.
For a microphone:
There are various USB audio interfaces which support phantom powered xlr directly.
This plus your old mic is more universal than a USB microphone. Even as the USB mic is usually simpler on first sight. Maybe read a little about it and decide what suits you best.
A new USB interface with 48V should start around $70. I would advise to get a better model, but used if you don't mind.
The problem with these devices is not the function, but the driver support. It depends on which Windows version (or Mac) you use for measuring and your audio stuff.
I can recommend FOCUSRITE products, a "Scarlet 2i2" from the first series is perfect for anything audio, as they have very good driver support.
So if you go this way, PLEASE first check driver situation, then buy. If you have an older laptop running Win7 (just for audio) like me, you have less problems.
Get information about the driver support of and how it works BEFORE you buy. I can not emphasize this enough. With a bad or wrong driver you will waste endless time. Ask me how I know...
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With the old JBL monitors, just like in North America, we have a strong fan base in Germany. In the last years a lot of talented speaker builders have restored such speakers. The drivers still have surprising potential, but to say it very carefull: The x-overs of all these vintage JBL are out of date. Not the parts, but the whole cirquit. As today, every hobbyist can measure things JBL coud not during development, you can get results much better than original.
This, which is most important, without loosing the signature and excitement they had at "their time". In fact modified they turn out to still be some of today's most impressive speakers. Of course, they profit from high quality gear and music sources we have today, even for very little money. If we are honest, not everthing was better in the old times, at least in audio.
This, which is most important, without loosing the signature and excitement they had at "their time". In fact modified they turn out to still be some of today's most impressive speakers. Of course, they profit from high quality gear and music sources we have today, even for very little money. If we are honest, not everthing was better in the old times, at least in audio.