@weltersys The specs i have are directly from the Lase oem, Also lase displays the same spec on the web page. I originally went the reflex route for the smaller size I can stack myself, I currently have 4 so maybe in the horns they would reach down to 30hz. I`ve never used horn resp but ill figure it out, I was hoping maybe someone had experience with this combo already.
@GM "Based on your published specs, near enough dead on for a T/S max flat alignment : Vb = Vas, Fb = Fs, so tuned too low and assume the box is too big."
Are you saying the tuning is to low for this driver? That output below fs diminishes?
@GM "Based on your published specs, near enough dead on for a T/S max flat alignment : Vb = Vas, Fb = Fs, so tuned too low and assume the box is too big."
Are you saying the tuning is to low for this driver? That output below fs diminishes?
Correct! I made my assumption based on your complaint WRT its poor LF performance relative to the posted specs and now knowing the specs you posted as supposedly close enough, then you did tune it too low (30 Hz vs the driver's 41 Hz Fs tuning) and since the sim looks quite flat the box is apparently too big, so either a Vb = Vas, Fb = Fs as 'close enough' or do the math..............
T/S max flat alignment:
Vented net volume (Vb) (L) = 20*Vas*Qts'^3.3
(Ft^3 = (Vb)/~28.31685)
Vented box tuning (Fb) (Hz) = 0.42*Fs*Qts'^-0.96
F3 (Hz) = Fs*0.28*Qts'^-1.4
(Qts'): (Qts) + any added series resistance (Rs)
As I said, the Fb of the Keystone is around 36Hz. It's output is around -10dB at 30 Hz, not useful if you want it loud that low, boosting more than a few Hz below Fb just wastes power and makes the cone flap.
The LASE site I looked at yesterday listed the voice coil size as 4", having found the TS parameters for the "New! LASE LF-3600 18", I see they agree with the "SD-LF18X451" you posted in #1634.
However, those TS parameters are not at all the same as the RCF LF18X451, which has 30Hz Fs and VAS almost twice as large, 220L vs 124.4L.
At any rate, your "clone" may look like the RCF, but looks can be decieving
@weltersys thanks for the input, I understand I have a clone and not to expect the same performance as the original. My question was if tuning below fs was the issue with reduced output down low as I’ve heard some say you can and some say no which @GM answered. I do see the keystone is tuned to 36hz but I’ve always been under the impression that mutual coupling will add lf extension with horns, and if solid 30hz was achievable with 4 cabs? Maybe the Th18 as @BP1Fanatic suggest would be suited better? Sorry I didn’t mean to hijack the thread🤣
Well, you do get more due to the tap, but where you really gain below Fs is when designing for arrays.
None that I can recall, but haven't followed the myriad Paraflex designs that I assume exist on FB as I've noticed some truly huge 'wall of sound' systems around the world.
No, the low corner of multiple tapped horns (TH) of any type won’t drop by 6Hz going from one to four cabinets, perhaps one Hz. The Keystone has more frontal area than the XocTH18, so could be expected to have more forward gain than an equal number of TH18.
Front loaded horn (FLH) mouths are usually built “undersized”, the output at Fc (horn cutoff frequency) is often -6dB (or more) below the upper peak. When multiple FLH are used their increased mouth area increases the low end down to Fc in additional to the expected +6dB for each doubling of cabinets and power.
The more “flat” response in the FLH array makes it sound like there is more relative low end, which is taken for low frequency (LF) extension. The actual LF corner frequency may not have dropped any more than 2 Hz from 1 to 4 cabinets.
TH frequency response does not change as much as FLH in array, very little to no drop in LF corner frequency, however TH may exhibit more forward directivity than FLH or bass reflex (BR) of similar frontal area.
Directionality of FLH, TH or BR cabinets can be altered by physical location and proximity, or digital delay, cardioid patterns can be created if desired.
Normally we expect drivers with larger VAS and lower Fs to perform better in a larger cabinet at low tunings than a smaller VAS higher FS would. In turn, the smaller VAS higher FS should perform better in a smaller cabinet.
In contrast, the RCF 18” LXF451 and the Lase LF18-3600 “clone” simulate almost identically in tunings below and above Fs, larger or smaller cabinet volumes than the VAS.
337L is about the gross volume of the Keystone, 186L half the size.
I did BR simulations of 35Hz Fb (same as the Keystone sim Fb) 186L and 30Hz in 337L & 186L.
The 337L 30Hz Fb BR has +3dB at 30Hz compared to the Keystone, but -5dB (or more) less output at 100 Hz.
The 186L 30Hz Fb BR is -3dB LF reduction, output at 30 Hz no more than the 35Hz tuning, and about -3dB at 40Hz.
The 186L 35Hz Fb BR uses more voltage (power) to achieve -2 to -3 dB less output than the Keystone, though two cabinets with two drivers could achieve +2 to +3 dB more level using three times the power.
Both the RCF 18” LXF451 and the Lase LF18-3600 perform equally well in the Keystone simulation, and favorably to the B&C 18SW115-4, output difference mainly due to the 18SW115 greater Xmax/Xvar.
The Keystone exit can’t be modeled exactly using Hornresp. The actual measured response tilts up from around 40Hz to 100Hz, the upper 120-160Hz peaks at lower level than the 100Hz response.
The RCF 18” LXF451 and the Lase LF18-3600 both appear to be more sensitive than the heavier 18SW115-4, approximately 1180watts compared to 1921watts required to reach Xmax/Xvar.
I know the 18SW115-4 has low distortion below Xmax/Xvar, having never heard or tested the RCF and Lase, can’t vouch for them, but they look good in the simulations.
Art
Not that they have reported.
It would require a lot more bracing to make 1/2" ply as stiff as 3/4".
The reports of wood deflection and level loss at high volume in smaller TH subs using 1/2" and added build complexity to save a few pounds is not worth it.
Zwiller,
Each of the BC front loaded horn (FLH) enclosures has a mouth exit best suited to the application.
I tested over 20 different shapes and areas before deciding on the Keystone tapped horn exit.
Several years later found it interesting to see Danley Sound Labs using a keystone shaped exit on their DBH-218LF:
The DBH-218LF exit shape was simply a result of using a side exit on a FLH:
At any rate, after extensive testing and evaluation, I don't think any of the DSL FLH exit shapes would result in overall better response for the TH Keystone Sub, but don't let that deter you from trying them yourself!
Art
The BC ("Boundary Coupled") front loaded horn drivers are located about 1/4 wavelength distance from the exit, the exit shape is relatively unimportant, but location in the boundary is.
The Keystone sub's mouth shape, area and location was dictated by the position of the two sides of the driver relative to the exit.
When the rear path length was extended, in the "Tall" version, the location and area had to be changed to retain decent response past 100Hz and keep the Fb low.
Art