Hi all...
If I had two of these:
...and wanted to replace the 8" mid-bass drivers with say two of these (or similar):
...would this be something worth pursuing? Is this even worth trying to model with Hornresp (something I haven't learned to do yet) or would I be better off just building a true MEH (Synergy) horn?
Reason I ask is I have access to a pair of KPT-305-MB's and want to replace my Bohlender-Graebener (BG) Radia SA-320 in-wall's with something more dynamic and move to point source type presentation.
Thanks in advance!
Mark
If I had two of these:
KPT-305
SINGLE 8-INCH TRACTRIX® HORN-LOADED MID-BASS DEVICE
The KPT-305 is utilized as a mid-bass device in the 4-way fully horn-loaded KPT-MCM-4-Grand and the KPT-745. It augments the low frequency sections of these speaker systems for effortless, distortion free bass in large auditoriums...and wanted to replace the 8" mid-bass drivers with say two of these (or similar):
B&C 8CXN51 8" Professional Neodymium Coaxial Speaker 100 x 100 8 Ohm
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...would this be something worth pursuing? Is this even worth trying to model with Hornresp (something I haven't learned to do yet) or would I be better off just building a true MEH (Synergy) horn?
Reason I ask is I have access to a pair of KPT-305-MB's and want to replace my Bohlender-Graebener (BG) Radia SA-320 in-wall's with something more dynamic and move to point source type presentation.
Thanks in advance!
Mark
Greets!
Hmm, good question! A quick look at the specs indicates you could do a lot worse, though assume this system is quite pricey to many DIYers, otherwise an obviously H.E. ready made, proven 2 way horn design.
My main 'problem' with it from a purely technical POV is that even in a fairly large room is the lack of physical closeness to the woofer(s).
Of course this can be solved by adding them to the horn as some have done, but at a glance seems considerably more work than on a simple slab sided WG, so being basically lazy (mom told folks I was born lazy and had a relapse!) and the fact that I prefer a WG's CD to the Tractrix's beaming makes doing a MEH a 'no brainer' for me. Of course IMNSHO/FWIW/YMMV. 😉
Hmm, good question! A quick look at the specs indicates you could do a lot worse, though assume this system is quite pricey to many DIYers, otherwise an obviously H.E. ready made, proven 2 way horn design.
My main 'problem' with it from a purely technical POV is that even in a fairly large room is the lack of physical closeness to the woofer(s).
Of course this can be solved by adding them to the horn as some have done, but at a glance seems considerably more work than on a simple slab sided WG, so being basically lazy (mom told folks I was born lazy and had a relapse!) and the fact that I prefer a WG's CD to the Tractrix's beaming makes doing a MEH a 'no brainer' for me. Of course IMNSHO/FWIW/YMMV. 😉
Here is a picture of the mid-bass module I refer to above (highlighted in red)... sometimes I need visuals to know what someone is talking about. I'm asking about taking the existing 8" driver out of the horn and replacing it with a coaxial one in order to cover everything down to the crossover to a sub. Sort of a MEH treatment without having to cut holes in an expensive horn. Of course I have full expectations that Murphy's law would kick in and that any 8" driver I choose to replace the existing one would not bolt directly onto the horn 😒
I'd rather do what @Cask05 did with a K-402 on the Klipsch forum but I don't have access to any of those... only the mid-bass units.
I'd rather do what @Cask05 did with a K-402 on the Klipsch forum but I don't have access to any of those... only the mid-bass units.
Thanks GM... can you explain what you mean by the "lack of physical closeness to the woofer(s)".
Your last point is an avenue I'm exploring as well. I have a friend who is a cabinet maker and I've been in discussions with him to make me some full-range size horns using @bwaslo spreadsheet. I have more money than time these days otherwise I'd buy a decent table saw and go for it myself. In addition, whatever direction I go I will be building these flush into my wall (giant garage is other side so I have the room for "bump outs"). Have a feeling that will be a challenge to do in a way the wife will accept (which basically means hidden)!
Ah! When I searched KP-305, its manual listed a K-402 horn...........in your case, no clue how well it will perform with so little available info, but then with sufficient DSP, who cares anymore? Do recommend comparing its tweeter DI chart to the K-402's to make sure it expands 'fast' enough to not 'choke'/'pinch' it in its intended passband.
You're welcome!
A typical horn/woofer cab has too long a physical distance between their acoustical center lines to sum as one at <1/4 WL of the XO point like in a MEH.
'Sounds' like an excellent long range plan! Note that a T-shirt, etc., ink screen printer can make ordinary acoustically transparent enough grill cloth into 'painted' works of art, so get SWMBO to choose what 'paintings' to put on the wall 'for the win'! 😉
Actually, what you have posted is a KPT-XII, which has a much bigger throat than the K-402 horn.
The KPT-XII is not made anymore so if you're going to use these with a cone-type coaxial driver, you'll have to source a couple of old used XII horns if you can find them. The K-402 horn is the horn above the XII horn in your horn stack picture that's posted above.
The KPT-305 midbass module uses the same horn as the Jubilee--the K-402--which has a 2" diameter throat. If you're set on using the KPT-305, then I' recommend using a Celestion Axi2050 driver, which has good output on a K-402 horn down to 250 Hz--but it requires a DSP crossover to flatten the SPL response.
At 250 Hz, if you're thinking about crossing to a bass bin you'll be pretty close to 1/4 wavelength (13.6 inches or 34.5 cm) with the centerline of the woofers, perhaps 1/2 wavelength instead of 1/4 wavelength, but nevertheless it's better than separating the woofers from the higher frequency driver centerlines by a much larger amount.
Chris
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Thanks for responding Chris. I think Klipsch has changed some things up since you last looked?
https://www.klipsch.com/pro/cinema/parts-upgrades
Have a look at the description (not the picture-it's obviously wrong) of the KPT-305. I've been talking with the Klipsch pro distributor in my area (I live in Fayetteville, Arkansas) and I don't think you can buy a K-402 horn with the 2" diameter throat that is not part of a stack anymore.... only the mid bass module is available separately (again as per what the distributor tells me). It's a shame really as I would have liked to build what you did over on the Klipsch forum. 😢
That said, based on what GM has said about using the mid-bass horn with a coaxial driver in place of the original 8" woofer, I will not pursue that avenue. Instead I think I will still follow what you did as closely as I can using Bill's spreadsheet (I have a version you worked up that gets close to a K-402.. i.e. 220 hz cut-off).
In my shoes, would you choose the Celestion or the BMS dual driver? All active with DSP is my plan. Would you also still use the Crites 15's? I drive close the Crites all the time on my way to Little Rock and was could easily pop in and pick up 4 woofers... save on shipping!
BTW... thanks for all you have contributed!
Hooking up a coaxial cone driver with compression driver to a midbass horn will not work very well as the tweeter horn area expansion has a massive discontinuity. This is formed by the end of the tweeter horn, the throat chamber of the midbass horn and the throat of the midbass horn. A better solution is to move the driver forwards so the throat of the horn meets the compression driver horn. Then the cone driver is fed into the horn via bandpass ports. This however does require some fabrication.
That was what I suspected. Out of curiosity, do you know how a driver such as the one I posted above (B&C 8CXN51 8" Professional Neodymium Coaxial Speaker 100 x 100 8 Ohm) is intended to be used?
The K-402 horn is the one in the KPT-305 midbass module. I own one--and that's now the center K-402-MEH loudspeaker in my 5.2 setup.
If you are being prevented from buying the KPT-305 midbass module in the Fayetteville area, I recommend going instead to Cinequip (American Cinema Equipment) in Oregon to buy one--and ask to speak to Spencer. Note that they're about $1500+ (USD) each, if the price hasn't gone up in the latest inflation spiral.
You apparently can still buy a KPT-402-HF assembly from Klipsch, but it has no box--only a stand and a 2" compression driver that I don't recommend (the K-691). You'd have to build a box around the K-402 to make it work like a KPT-305.
Klipsch is getting greedy so they are trying to find ways to prevent you from having a loudspeaker that acoustically is equal to the new Jubilee ($35K USD a pair). They are not your friend (nor is the dealer in Fayetteville apparently).
The KPT-XII horn is not made anymore. It has a 12" throat, and was discontinued about 2010. Just ask Roy on the K-forum or any of the guys that own first generation Jubilee/Profession hardware. I know a guy that regrets selling his KPT-XIIs from around the 2010 timeframe to "upgrade" to the KPT-305 for his MWM stacks in his home (mark1101). He has said many times that he cannot buy XIIs anymore. I believe him.
I really do recommend an MEH version over what you are proposing--however. The acoustics are much better.
Chris
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Another challenge will be the toe-in most would want for a horn system, generally pointing to around the center of the listening area. A horn/soffit extension would be needed to avoid reflections and diffraction from the inner edge of the horn off the hole in the wall.
Co-ax woofer/HFhorn are generally flush mounted, though DSL does use drivers similar to the B&C8CXN51 in the 8" SH100 and 12" SM80, the horn basically a continuation of the cone profile.
Not the best examples of pattern control compared to a dedicated horn design, but the virtual single source point may still be an improvement over a separate horn/woofer when both vertical and horizontal dispersion are considered.
Art
I think William Cowan's solution is probably the best approach if you're trying to embed an MEH into a flush mount arrangement. Proper toe-in is critical. Trust me.
Chris
You actually hit upon one of my questions I was going to ask. I was thinking I'd need to toe-in the speakers a bit and you have confirmed it. Seems workable however...
Someday I might build your SYnTripP design for my pool area (complete overkill I'm sure)... learned a lot from your threads! Thanks Art
The Celestions have been expensive relative to the BMS 4592ND (dual diaphragm) 2" drivers. The offsetting cost of an additional amplifier channel should be factored in, however.
I do not recommend using the BMS 4592ND driver with a passive crossover as the high frequency diaphragm needs delay relative to the midrange diaphragm (about 0.146 ms when crossed at 6 kHz). Otherwise, if you try to use a 4592 ND without HF diaphragm delay (i.e., bi-amped) you're going to hear a timbre shift relative to a Celestion Axi2050 or TAD 4002 driver.
There are many options available for woofers. I'd look for an 8-ohm (nominal) impedance woofer so that you run them in parallel to hold down the required voltage from the woofer channels--perhaps a lesson learned with the prototype. To start, I'd look around for a 15" woofer with a free air resonance around 25-35 Hz and a Qts of 0.25-0.3--if you can find one. If you can't find an 8 ohm woofer with those parameters, then a Klipsch K-33 clone driver or the Crites 1526 will work as 4-ohm drivers. The last time I looked, the Klipsch K-43 driver used on professional bass bins has a Qts that's too high (i.e., too heavy a cone and/or too small a motor).
I'd first look at the woofer that you select using Hornresp. I posted the Hornresp input parameter screenshots that I used for the K-402-MEH in the Klipsch thread on this subject--that might save you some time.
Chris
just thinking out loud here but can this delay be acomplished with an allpass network or mismatched filter order?
Found 11:
http://www.loudspeakerdatabase.com/search/15.0_size_in_15.0/8_z_8/25_fs_35/0.25_qts_0.30
Any favorites among these?
Take your pick from the xmax and price combinations. For my uses, I'd look at the price first, then look at the xmax and the free air resonance (lower is usually better at this range of Qts). You might have different design and/or implementation needs.
Chris
If you're that into passive networks, I suppose you could do that...but I value having the further transient isolation of have two amplifier channels (i.e., bi-amping) on the two different diaphragms. It sounds cleaner to my ears--and is free from back EMF and acoustic feedback issues on a shared electrical circuit, IME. YMMV.
Chris