thylantyr said:When the project is completed.
Perceive owner: Shin
Perceive designer: Scott
LOL
When your not getting the right results after 2 different drivers that are very well regarded then clearly I either have highish standards and/or I don't know as much as I think I know 😉 Its not a weakness taking others advice and letting them guide you, if anything its a strength.
That's what these forums are for, asking for advice, debating, posting idea's and showing results.
If you get hung up on not taking others advice then you'll never learn anything. I only started building speakers just over 2 years so I've clearly got a hell of lot more to learn, advice is a godsend to me. Without the likes of Scott, Rich, Al and anyone else who's offered a suggestion whilst building these speakers, I'd bet my life they wouldn't sound so god damn good.
I'm very good at the woodwork/finishing and can build virtually anything but that's where my prowess ends and others take up the slack 😀
I keep coming back to the idea of using the PD2150, only really using it's rock 'n roll sensitivity. Instead of boosting the bottom via BR, passive radiators or active filters, just use it as it is, and roll off the frequencies above 20Hz. Yes, so you lose the 98dB efficiency, but you could practically get 90dB flat to 20Hz...
thylantyr said:When the project is completed.
Perceive owner: Shin
Perceive designer: Scott
(I realize the humor here, but this is a good "segway" into something that I feel needs to be addressed - generally, not specifically to you thylantyr. So with that in mind..)
..Some of the basics behind the design perhaps, but..
I think you are discounting Shin a LOT here - there is the obvious cool esthetic and the superb craftsmenship that is *all* Shin.
But beyond that, most of the limitations were spec'ed by Shin, and its those limitations that ultimatly decide the nature of the project.
Consider the design started with the dual-ring revelator tweeter. This is not a tweeter I would have ever recomended (..not because it isn't good, but rather it isn't *that* good for the money). So it kind'a starts from that point - i.e. whats the best midrange to pair with that tweeter? Considering numerous qualities I think Shin did in fact purchase the best possible midrange to acompany it - and furthermore HE was the one that initially suggested it (..I was just one among many that happened to agree).
Then we went onto midbass drivers - and again Shin had drivers in mind and specifically wanted to go the LT route. After a few disasters, he eventually came to realize that that much assist down low was a "no-no" AND that small motor HiFi driver's were not satisfactory here. My suggestion just happended to fundamentally coincide with what he ended up with, even though he neither used the midbass driver I spec'ed (215 GMF) or the use of an aperiodic vent. (..so still quite different.)
..and so here we are with the subs.. (..again my first choice would have been a multi-driver cardoid.)
The funny thing is that while the process isn't much different with others - the final outcome is. I.E. I've made a LOT of other recomendations to other people and though some of them have a few similarities, I think you would be hard pressed to find even moderatly similar recomendations when taken as a whole. (i.e. everyone is going to be at *least* a little bit different - and its this diversity I find appealing.)
Now the reason I mention all this is certainly not to be defensive, (I realize the humor here), or to even praise Shin's creations (..one of the few acomplishments here that needs no praise), instead its to highlight that the design process is not an imeadiate solution - but rather an evolution that requires flexibility on the part of all participants and is ultimatly about what the builder actually *wants*. Sometimes others forget this (perhaps having their own agenda) - and are not working *with* the builder. Thats a real shame when that happens. Sure, IF the builder follows through with the such "suggestions" then they may in fact end-up with something excellent, BUT its likely it will not give that "deep-down" satisifaction that comes from both being included in the design process and ultimatly providing the "character" that the builder was actually after.
well just my perspective..
ScottG said:
And perspective is everything 😉
I thought it would be interesting to add some EQ to the driver and also compare it to the mighty PD2150.
Here are the options I plugged into the EQ filters:
An externally hosted image should be here but it was not working when we last tested it.
There's basically one band of PEQ with a broad Q and -14dB gain, this is centered right around 300hz. The aim of this is to drop the level to my lowest common denominator - 20hz.
The 13dB of gain is just to level match to the PD 2150, its worth noting that the excursion plot *is* shown with this included.
And finally there's a steep Butterworth 8th order highpass at 16hz(which I won't use, a highpass that low is disgusting for the sound IMO).
All figures are for a single sub and the BC driver *has* the above EQ settings applied in all plots
Response
An externally hosted image should be here but it was not working when we last tested it.
Maximum SPL
These figures are great for 12" mounted in a 63ltr cabinet tuned to 19hz. The 125ltr sealed PD2150 in a critically damped aligment loses out by 4dB at 20hz but above 27hz it powers away, as you would expect from a 21" vs. 12". The PD2150 in a vented enclosure is a true power house but the enclosure is HUGE at 400ltrs tuned to 20hz.
An externally hosted image should be here but it was not working when we last tested it.
Excursion
These excursion plots are level matched at 20hz between the PD and the B&C drivers, that's why the BC is working harder - its a case of 21" vs. 12". Take a look at the maxSPL chart for a better idea of what the limit is for each.
An externally hosted image should be here but it was not working when we last tested it.
Port Velocity
6.5mtrs per second peak @ 17.5hz and an SPL of 92dB @ 20hz:
An externally hosted image should be here but it was not working when we last tested it.
At the the excursion limits of the driver(110dB @ 20hz) we see things get very ugly:
An externally hosted image should be here but it was not working when we last tested it.
This is why I avoid ported 😀
I've been working on your design for a while now - hopefully I'll have it finished sometime tomorrow (..it will take a few posts worth).
In the mean time - nice comparison!
just a couple things to add though..
63 ltr's and 125 are not exactly the same.. 😉 A better comparison would be the 2 B&C drivers vs. the one PD driver.
You'll have an additional 3db from the port firing at the floor (which elevates the 20 Hz response).
You also need to show the impeadance of port and driver in-box at the same time to see the real load it presents to the amp (..and also the PD in box). Also since the driver is rms at 2000 watts use that for your driver's spec. (on the apples to apples basis) if you hadn't already. Also note that the air-load from certain methods of porting will lower impeadance at port resonance relative to a modeled response (..and of course velocity will also be altered).
Finally for max values (and HT) the comparison was excellent, but for music listening try them both without eq. looking at the 1/watt 1/meter response. In other words whats the efficency of the system at lower power levels throughout the passband, but particularly at 20 Hz (without eq.)? (..and this is when you start having a "glimpse" at non-linear distortion operation at average levels.)
In the mean time - nice comparison!
just a couple things to add though..
63 ltr's and 125 are not exactly the same.. 😉 A better comparison would be the 2 B&C drivers vs. the one PD driver.
You'll have an additional 3db from the port firing at the floor (which elevates the 20 Hz response).
You also need to show the impeadance of port and driver in-box at the same time to see the real load it presents to the amp (..and also the PD in box). Also since the driver is rms at 2000 watts use that for your driver's spec. (on the apples to apples basis) if you hadn't already. Also note that the air-load from certain methods of porting will lower impeadance at port resonance relative to a modeled response (..and of course velocity will also be altered).
Finally for max values (and HT) the comparison was excellent, but for music listening try them both without eq. looking at the 1/watt 1/meter response. In other words whats the efficency of the system at lower power levels throughout the passband, but particularly at 20 Hz (without eq.)? (..and this is when you start having a "glimpse" at non-linear distortion operation at average levels.)
Look forward to it 🙂
Just took a quick look.
1w/1m at 20hz is 80dB. The PD2150 is 90dB in the same conditions. Cabinet details are 63ltr/19hz tune and 400ltr/20hz tune respectively. That PD takes up an insane amount of space and for what? Its easy to that you could fit 4 maybe 5 12TXB's into that same volume. Of course its also a fair bit more money but if you main limitation is space then...
With two subs this will of course rise to 86dB and if the 3dB gain from the port is included at 19hz then we're looking at 88-89db for 20hz 1w/1m. That pretty good considering the constraints your working with. Including a conservative 3dB room gain and its an easy 91-2dB while coasting along with only a watt. I've measured what I consider my average listening level and its mostly 80-90dB. Distortion should be excellent at those levels considering the above.
Its not really the distortion that I'm worried about though, its the snappy, tight and free sounding bass that I'm really hoping for.
ScottG said:
It will do that in 400ltr enclosure tuned to 20hz with 1w/1m. No chance for sealed though, its more like ~78dB with 125ltr.
errrggg.. looks like it won't be until sometime tomorrow before I finish this up.. 🙁
(it will be..hmm, shall we say - "lengthy") 😉
(it will be..hmm, shall we say - "lengthy") 😉
ShinOBIWAN said:
I'm just
'ing.... 
Make a subarray. The drivers chosen don't have to be awesome
as the sum 'of the array' does the hard work.
The array can be tall and look evil for the fear factor, compliments
the mains better as people run scared.
The array can offer more than you need so when you don't
need more now but later do need more, you have it.
I disagree on the array. I've learnt that there is no substitute for quality. Using multiple cheap drivers is a false economy because you just end up having to use lots of them to avoid driving them unlinearly and to get the desired SPL because they have poor Xmax. You get as good if not better results with a smaller form factor by using less of but much higher quality drivers.
The better drivers tend to have much higher BL than cheap ones as well, and I feel that this parameter contributes that feeling of slam that cheap drivers just can't muster.
The better drivers tend to have much higher BL than cheap ones as well, and I feel that this parameter contributes that feeling of slam that cheap drivers just can't muster.
ScottG said:
No rush Scott.
"Done when its done" Is something every DIY probably says to themselves at least once 🙂
thylantyr said:
I'm just
Make a subarray. The drivers chosen don't have to be awesome
as the sum 'of the array' does the hard work.
The array can be tall and look evil for the fear factor, compliments
the mains better as people run scared.
The array can offer more than you need so when you don't
need more now but later do need more, you have it.
Many a true word said in jest 😉
An array would likely be large and I have to agree with Rich, quantity doesn't always equal quality.
ShinOBIWAN said:
I use a Velodyne SMS-1 to give some boost at lower frequencies, also the Velodyne has a microphone and a parametric equalizer for room correction which makes it very easy to get a seamless integration with the main speakers.
I have yet to build the braced cabinets, but in a simple prototype closed box they gave natural un-stressed bass that is just there. A Peerless XLS-12 +slave sounded in comparison rather coloured and stressed. 😀
I use AutoCAD.
ShinOBIWAN said:
And tylantyr may not be practicing what he preaches. Isn't he the guy with a whole bunch of 15" Lambda Apollo's - not exacty cheap drivers.
Sheldon
I shoulda put a couple of smiley faces in there. I was just trying to tease tylantyr a bit. I did check, and at one time he did have 10 pieces of Lambda 15" Apollo. Maybe he'll tell us what he eventually came up with.
Sheldon
Sheldon
Sheldon said:
Thy's project is still progressing. As I understand he needs a larger number of expensive drivers for large line arrays. I think he's just bought the last of the treble units needed and now has all the amplification and drive units required with the rest of the work being cabinets etc.
He's got around 5 hobbies that keep him busy but they should be pretty awesome once finished though.
Part 1 Episode III The Empire...... 😀
I'll start with the port here because it poses some serious design limitations and because getting it done *right* isn't as simple as purchasing a ready-made port (..though it isn't exactly difficult either).
1. The port needs to be downward "firing" (considering gain and system compliance) - FAR preferably at a platform rather than at the floor itself (so you can avoid airflow constriction). This means you'll have a platform (perhaps only an inch thick) PLUS about an inch and a half air-space from the base of the cabinet to the platform. The cabinet elevation should be derived from some sort of very rigid feet (I use the cheap speaker spikes *inverted* for this, but its up to you). (Note: its also *VERY* nice to have the ability to alter the air-space via raising an lowering the cabinet from the platform.) You can also move these "feet" a little further "in" (towards the center of the cabinet) to give the look that its floating from most angles (..again, up to you). You will also want "feet" of some sort on the platform - but it isn't needed to do anything more than be rigid and raise the platform off of the floor itself.) Both the platform and the air-space (in combination with downward "firing") are VERY important to getting "tight", "fast" bass (..and having the ability to adjust the amount of air-space aids this process).
2. The port shouldn't have any bends - this means that 56 cm length of the port should be terminated flush with the base of the cabinet (no flared extension needed or even desired). Typically the port "entrance" should be well away from the cabinets walls - a good "rule of thumb" would be 1/3rd the length of port for a fairly long port like this - i.e. around 18 cm. This then means that from the external base of the cabinet the interior "top" of the cabinet should be 56 + 18 ='s 74 cm or about 29 inches - based on a *guess*. For the total sub height of course you'll need to include the platform (its rise) and the air-space - so you are looking at about 32-33 inches in height (i.e. a nice sidetable size). Now this doesn't mean that you actually NEED 18 cm internally - this is where you might want to do some experimentation if you think the result is a little higher than you like. (..this is all about internal compression near the port entrance.) Another thing you could do here is use a very small plastic funnel attached to the interior top wall right above the pipe (..with about 2 inches of clearance between the "drip" end of the funnel and the port entrance - the funnel filled with silcone caulk.) Of course you don't need an actual funnel - just something that is cone shaped and has a low friction exterior.
3. Good port construction needs several things:
A. It needs to be *extremely* rigid, far more than your average suppliers port offerings. Think metal or thick pro"plumbing"-grade pvc pipe.
B. It needs to be isolated from the internal enviorment of the cabinet (with the obvious exception of the entrance).
C. It needs to be dampened externally.
D. It needs to be coupled to the cabinet both rigidly AND be relativly immune to cabinet vibrations.
E. It needs a VERY low friction internal surface.
F. It needs some short (about 4 inches) poly drinking straws shoved up the port exit (flush) - giving the exit's cross-section a honeycomb look.
You'll have to find the 3 inch internal diameter pipe that meets "A. & E.'s" requirements.. Of course it doesn't have to be 3 inches, it could be more (and it would be better if it was more), BUT that is the minimum I would recomend. (..and of course if you do go for a larger diameter port then you'll need to use the model program of your choice to make the adjustment with respect to length.) Port velocity will of course be effected with power compression as well at very high spl's, BUT the air-load provided by the platform/cabinet air-space will alter this and the straws will additionally alter exit turbulance.
Anyway..
For B. C. & D. I use 2 pipes - 1 for my actual port, the other as an outer "sleeve" for the port. In-between the two I fill with silicone caulk (..hmm, where have we heard that before?). (..typically the net result is anywhere from a half inch to 2 inches of surrounding caulk, depending on the size of the "sleeve".) It does a great job and its easy to do. It does however reduce some volume from the cabinet. In truth the "sleeve" doesn't have to be a "pipe" at all - it could be a box, but this usually isn't as good when considering airflow in the cabinet. My preference for the "sleeve" is almost always larger pro-plumbing pvc pipe (cut to length in-store).
The lengths of the pipe ("sleeve" and port) will not be identical. From the port entry they will be "flush" together. The "sleeve" will extend most of the length of the port and then stop and couple to the *interior* wall (bottom panel) of the cabinet. The port however will extend further and couple to *exterior* cabinet (bottom panel). The cabinet wall should NEVER be touching the port except at the exterior where the port is coupled to it. (..i.e. the diameter of the cabinet's hole for the port should be just *very slightly* larger than the external diameter of the port.)
At least with pvc plumbing there are coupling pieces that can be glued to the pipe and then screwed to the respective cabinet position - as for other pipes.. you'll have to find coupling pieces for them (..as you likely did for the "pole" on the perceives).
The low friction nature of the pipe can be tested with flower - if you dust it on and the flower slides out, (obviously when the pipe is vented perpedicular to the ground), with little or no coating to the pipe, then its probably good. It can always be improved with waxing and buffing.
The straws are pretty much self-explanatory. Obviously if the straws have corregated "bends" make sure you don't use that portion of the straw. When stuffed in place they should stay-put, but some times I'll coat them lightly with glue (the plumbers primer/cleaner and glue).
I'll start with the port here because it poses some serious design limitations and because getting it done *right* isn't as simple as purchasing a ready-made port (..though it isn't exactly difficult either).
1. The port needs to be downward "firing" (considering gain and system compliance) - FAR preferably at a platform rather than at the floor itself (so you can avoid airflow constriction). This means you'll have a platform (perhaps only an inch thick) PLUS about an inch and a half air-space from the base of the cabinet to the platform. The cabinet elevation should be derived from some sort of very rigid feet (I use the cheap speaker spikes *inverted* for this, but its up to you). (Note: its also *VERY* nice to have the ability to alter the air-space via raising an lowering the cabinet from the platform.) You can also move these "feet" a little further "in" (towards the center of the cabinet) to give the look that its floating from most angles (..again, up to you). You will also want "feet" of some sort on the platform - but it isn't needed to do anything more than be rigid and raise the platform off of the floor itself.) Both the platform and the air-space (in combination with downward "firing") are VERY important to getting "tight", "fast" bass (..and having the ability to adjust the amount of air-space aids this process).
2. The port shouldn't have any bends - this means that 56 cm length of the port should be terminated flush with the base of the cabinet (no flared extension needed or even desired). Typically the port "entrance" should be well away from the cabinets walls - a good "rule of thumb" would be 1/3rd the length of port for a fairly long port like this - i.e. around 18 cm. This then means that from the external base of the cabinet the interior "top" of the cabinet should be 56 + 18 ='s 74 cm or about 29 inches - based on a *guess*. For the total sub height of course you'll need to include the platform (its rise) and the air-space - so you are looking at about 32-33 inches in height (i.e. a nice sidetable size). Now this doesn't mean that you actually NEED 18 cm internally - this is where you might want to do some experimentation if you think the result is a little higher than you like. (..this is all about internal compression near the port entrance.) Another thing you could do here is use a very small plastic funnel attached to the interior top wall right above the pipe (..with about 2 inches of clearance between the "drip" end of the funnel and the port entrance - the funnel filled with silcone caulk.) Of course you don't need an actual funnel - just something that is cone shaped and has a low friction exterior.
3. Good port construction needs several things:
A. It needs to be *extremely* rigid, far more than your average suppliers port offerings. Think metal or thick pro"plumbing"-grade pvc pipe.
B. It needs to be isolated from the internal enviorment of the cabinet (with the obvious exception of the entrance).
C. It needs to be dampened externally.
D. It needs to be coupled to the cabinet both rigidly AND be relativly immune to cabinet vibrations.
E. It needs a VERY low friction internal surface.
F. It needs some short (about 4 inches) poly drinking straws shoved up the port exit (flush) - giving the exit's cross-section a honeycomb look.
You'll have to find the 3 inch internal diameter pipe that meets "A. & E.'s" requirements.. Of course it doesn't have to be 3 inches, it could be more (and it would be better if it was more), BUT that is the minimum I would recomend. (..and of course if you do go for a larger diameter port then you'll need to use the model program of your choice to make the adjustment with respect to length.) Port velocity will of course be effected with power compression as well at very high spl's, BUT the air-load provided by the platform/cabinet air-space will alter this and the straws will additionally alter exit turbulance.
Anyway..
For B. C. & D. I use 2 pipes - 1 for my actual port, the other as an outer "sleeve" for the port. In-between the two I fill with silicone caulk (..hmm, where have we heard that before?). (..typically the net result is anywhere from a half inch to 2 inches of surrounding caulk, depending on the size of the "sleeve".) It does a great job and its easy to do. It does however reduce some volume from the cabinet. In truth the "sleeve" doesn't have to be a "pipe" at all - it could be a box, but this usually isn't as good when considering airflow in the cabinet. My preference for the "sleeve" is almost always larger pro-plumbing pvc pipe (cut to length in-store).
The lengths of the pipe ("sleeve" and port) will not be identical. From the port entry they will be "flush" together. The "sleeve" will extend most of the length of the port and then stop and couple to the *interior* wall (bottom panel) of the cabinet. The port however will extend further and couple to *exterior* cabinet (bottom panel). The cabinet wall should NEVER be touching the port except at the exterior where the port is coupled to it. (..i.e. the diameter of the cabinet's hole for the port should be just *very slightly* larger than the external diameter of the port.)
At least with pvc plumbing there are coupling pieces that can be glued to the pipe and then screwed to the respective cabinet position - as for other pipes.. you'll have to find coupling pieces for them (..as you likely did for the "pole" on the perceives).
The low friction nature of the pipe can be tested with flower - if you dust it on and the flower slides out, (obviously when the pipe is vented perpedicular to the ground), with little or no coating to the pipe, then its probably good. It can always be improved with waxing and buffing.
The straws are pretty much self-explanatory. Obviously if the straws have corregated "bends" make sure you don't use that portion of the straw. When stuffed in place they should stay-put, but some times I'll coat them lightly with glue (the plumbers primer/cleaner and glue).
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