Well not ONLY / OR better
You want the TH to be build like it is modeled. NOT using reflectors leaves you with "extensions" in each corner, thus NOT the TH you have simmed. Why recalculating and changing simms "until you drop" and discuss about the smallest change, draw a TH in millimeters, while on the other hand ditch an important aspect of "build what you simm". I have seen lengthly discussion on this topic stating "the reflectors have no use, because of to long wavelength" while, strange enough, we all can see reflectors being used in quality products like the Danley TH's. So they DO/MUST have their use, it is more a matter of "how much" each reflector will solve a build mismatch. I do not think that adding complexity in a build will be applied by these companies, while they have no use (commercially that would be a tiny bit weird, won't it?). The "we will miss volume" soundbite can be easily corrected by making the TH a tiny bit wider. At low volume, you may not be able to hear a big difference, at higher volumes, we found it to be noticeable.
Same discussion goes for type of wood and braces.
Bottom line, their can (and mostly will) be more than one reason for each of these build issues to apply. I do not favor the principle, "if we find one reason NOT to do it, we will not listen and look to other reasons that say, we need to do it. I would like to keep learning.
A few rules i favor,
- use the birch ply wood (15 or 18 mm / 13 ply) screws and glue,
- apply braces on all panels that have a "one side load" (one side of the panel is the TH inside, the other side is out side of the TH, which you can also see in most Danley products)
- and use reflectors, at least on the second, third (and fourth) corner. Air is not only sound waves, but also particles that move at speed in a straight line until it hits an obstacle and bounce away from it at the same angle that it had while approaching the object. So 90 degrees will result in a full bounce back. They start at low speed at the driver and increase in speed while approaching the mouth (principle of a horn: High pressure&low speed transferred to low pressure&high speed)
kind regards,
Frans
The main reason for my post was the fact that the Danley product does not have a number or reflectors as seen in stewins post. The ones that he does have are placed as so the distance between them is greater than 1/4 wavelength in the passband (42 inches on the rear wall, about a 1/4 wavelength of 80hz)
Hi Frans!
"At low volume, you may not be able to hear a big difference, at higher volumes, we found it to be noticeable"
May I add that we should listen as the instrument plays thru it and not only look if the measurement curve is apparently OK, and that's the reason to use it...think why and what it does to the cabinet.
Regards,
"At low volume, you may not be able to hear a big difference, at higher volumes, we found it to be noticeable"
May I add that we should listen as the instrument plays thru it and not only look if the measurement curve is apparently OK, and that's the reason to use it...think why and what it does to the cabinet.
Regards,
OK, point taken. Would you see a draw back other than volume, to leave them as they are now?
regards,
Frans
High Pasc,
Fully support that. I've seen commercial designs that show nice graphs but they sound poor.
- Would it be an idea to have a "golden rules for TH" with all the info found so far.
- I also started working on a first best shot for a TH by means of a excel sheet. I know they already exist, but we could take it much further and have them predict the best starting point by means of inputting low corner and size of driver.
regards,
Frans
and use reflectors, at least on the second, third (and fourth) corner. Air is not only sound waves, but also particles that move at speed in a straight line until it hits an obstacle and bounce away from it at the same angle that it had while approaching the object. So 90 degrees will result in a full bounce back. They start at low speed at the driver and increase in speed while approaching the mouth (principle of a horn: High pressure&low speed transferred to low pressure&high speed)
FWIW none of the POC THs I've built used reflectors and they both sound fine AND are pretty good matches for the HornResp sims within the passband (which makes sense, because none of the reflectors approach the TH's upper passband in wavelength). Outside of the passband there are some differences, but I don't care about those.
The Danley only has the one reflector in the upper back corner where the handles are. Other cabs they build have large pockets of air along the expansion...
The Lord giveth and the Lord taketh away
And it's possible that its major purpose there is simply to section off the box there so that the handles don't introduce air leaks into the enclosure.
Unless their size is approaching the wavelengths within the horn's passband, or they are serving some other non-audio related purpose, reflectors in a bass horn are IMO a waste of time and effort.
circle is correct
Hi epa,
That's how I checked the mods I did to the baffles,as long as it gets bigger as you go it seems to work ok. They punch good, make your pants legs shake,lol
build note, If you drill locator holes for the screws in the last outside panel it makes putting the last side on real ez and you don't have to hunt the internal edges and you can be dead center of the baffle edge.
Have a great day!
NS
hi no smoking
i dont know the measurements of stewins drawing,but it looks like yours are a bit shorter.
i one draws a circel from the end of q it should be clear.
yours seem to work great so its a non isue
Hi epa,
That's how I checked the mods I did to the baffles,as long as it gets bigger as you go it seems to work ok. They punch good, make your pants legs shake,lol
build note, If you drill locator holes for the screws in the last outside panel it makes putting the last side on real ez and you don't have to hunt the internal edges and you can be dead center of the baffle edge.
Have a great day!
NS
good day to all. this is a picture of the two cabs i built. i used the original design before lerning about all of the internal bracing. i used all four of the reflectors and went back in later and installed two braces where i could.this is a picture from when i first started the build and had to ink in the reflectors and added braces, sorry for not having a proper picture.
http://www.diyaudio.com/forums/attachment.php?attachmentid=399802&stc=1&d=1392381194
i am using 18sound 2400s in them and recently added new equipment to my system. i havnt hardly used these while waiting to upgrade my system
here is a list of what i have now
two th18 subs loaded with 18sound 2400s
two jbell12 tops (dayton 310-8 and selenium 220ti-8 compression drivers)
two dual 18 cabinets
two single 18 sub cabinets
beringher inuke nu6000dsp
crown macrotech 3600
crown macrotech 2402
qsc rmx 2450
DBX driverack DRPA+
Firstly i would like to know if the th18s will be ok without the remainder of the bracing as they have been glued and cannot be opened without major damage. also would the 18sound 2400s be ok using in these cabs and if so set to what hpf and lpf as to not burn them up.
if anyone out there has had experience with the driverack drpa+ would you be able to help me with setting up my system properly so as not to damage anything.
if any of this is not supposed to be posted here i do apologise but i really do need some professional opinions. i have learned alot by reading this forum but want to be sure not to damage my system.
thank you all and have a great day
http://www.diyaudio.com/forums/attachment.php?attachmentid=399802&stc=1&d=1392381194
i am using 18sound 2400s in them and recently added new equipment to my system. i havnt hardly used these while waiting to upgrade my system
here is a list of what i have now
two th18 subs loaded with 18sound 2400s
two jbell12 tops (dayton 310-8 and selenium 220ti-8 compression drivers)
two dual 18 cabinets
two single 18 sub cabinets
beringher inuke nu6000dsp
crown macrotech 3600
crown macrotech 2402
qsc rmx 2450
DBX driverack DRPA+
Firstly i would like to know if the th18s will be ok without the remainder of the bracing as they have been glued and cannot be opened without major damage. also would the 18sound 2400s be ok using in these cabs and if so set to what hpf and lpf as to not burn them up.
if anyone out there has had experience with the driverack drpa+ would you be able to help me with setting up my system properly so as not to damage anything.
if any of this is not supposed to be posted here i do apologise but i really do need some professional opinions. i have learned alot by reading this forum but want to be sure not to damage my system.
thank you all and have a great day
Attachments
Two sides of the same coin. The reflectors change the volume so yes there is a difference. But we have all seen models that take every little corner and crevice into account, and then a simpler model produce the same response curve.
Short but sweet it matters in some situations and not in others.
It's what makes this stuff so interesting!
Correct expansion is less important than correct volume. I think jbell proved that fact with his ss15. I think he stated he lost dB when he added reflectors to the enclosure. In order for reflectors to work, he would have to increase the size of the enclosure, which would kill the single sheet status.
The extra cabinet stiffness the reflectors impart may slightly increase upper response at high level, but the cabinet volume is reduced by the reflectors, reducing LF output by a tiny bit.
The horn path length remains the same, so the LF cutoff does not change.
Looks like a good argument to me for not including reflectors, if the bracing provides enough stiffness already.