OT: design ideas for bass horns for PA

Hey all. I recently got a deal on a bunch of 15inch seismic audio drivers. I was thinking of building some bass cabinets in the style and philosophy of the older altec and jbl bins. I would like to use them for my dj/sound reinforcement gigs. Currently im running with all vintage amps and processing (altec, crown, shure, some tube and solid state). My speakers are newer though, and I haven't been impressed with their bass response at long range. I have heard that bass horn designs are good at throwing sound over longer distances, so im definitely game to try building some. There would be a size and weight limit, as I would prefer to be able to move them without a crane. So yeah, if anyone is willing to enlighten a noob on bass horns I would appreciate it. Some designs Ive been looking at specifically were the old peavey sp2s and 3s, as well as the Altec a7. Sorry for the rambling post, Im just kinda thinking aloud. Oh btw, I already tried posting about this on Audiokarma, but you all know how things go down over there....in speaker land, if you arent hacking up organ tone cabinets or identifying some random crap speakers from the 80s or discussing some new 105,000 gold rimmed speakers with nuclear powered field coils your shunned.

Definitely off topic here.

I suggest: Speakerplans.com they have a forum, also a place called dancetech.

How about one of these?
Push-Pull Double 15 Subwoofer Pic - Les Hudson - High Efficiency Speaker Asylum

Quote:

---

Oh btw, I already tried posting about this on Audiokarma, but you all know how things go down over there....in speaker land, if you arent hacking up organ tone cabinets or identifying some random crap speakers from the 80s or discussing some new 105,000 gold rimmed speakers with nuclear powered field coils your shunned.

---

You're right, i do know how things go down over there. But, i don't think you have a clue.

I find it hard to believe you were shunned at AK, it's a well moderated site especially where "attitude" is concerned. That said, it's usually considered bad etiquette to bitch about one forum on another.

Quote:

---

I recently got a deal on a bunch of 15inch seismic audio drivers.

---

Actually, the seller got the deal. You got a deal on an opportunity to learn something valuable, if you choose to embrace this objectively.

If you were offended because somebody revealed that the drivers you want to load in well engineered horn systems designed for well engineered drivers are actually cheap crap, then you either need to pull out the spec sheets and analysis data for the woofers and prove them wrong, or you need to take a closer look at the woofers themselves and consider a plan B.

I wasted the time to bother looking for Theile/Small parameters for Seismic Audio woofers on their cheesy website.

Guess what i found?

Under "technical specifications" they simply list the physical dimensions of the drivers. There are a few reasons a company doesn't post actual specs of their speakers. The 3 biggest are a) lack of quality control and consistent manufacturing methods which prevents parameters from being held to any respectable tolerance. b) the actual parameters/performance is so poor that posting is negative advertising. c) a "white van" company that sells cheap crap in fancy packaging to willing stooges where actual technical specifications and performance are not relevant to generating profit.

Quote:

---

I have heard that bass horn designs are good at throwing sound over longer distances, so im definitely game to try building some

---

There is some truth here, horns control directivity which can result in getting more sound where you want it, not just bass. But, you need to have an understanding of how woofers/drivers react to their environment and further understand that there are woofers which perform their best in a horn, as well as woofers that have no business in a horn at all. This is one of the reasons that it is CRITICAL to know a woofer's parameters before you can have any idea what kind of alignment it will work best in.

My advice to the OP is to "ask the questions", there's no such thing as a stupid one. There are a lot of folks both here and at AK with a lot of knowledge to share. All you have to do is show them an open mind.

My other bit of advice to the OP is to remember that the inflection of tone in the written word is near impossible to interpret. If a response seems snotty, snobby, or disrespectful, be careful about taking it personally as often times it isn't meant that way at all.

Patience grasshopper!!!!!!!!!!!!!!!!!

you might get one of these -


Dayton Audio DATS Dayton Audio Test System 390-806



`````````````````````````````````````````



seismic audio is billed as musical instrument stuff.

i was thinking about getting the cast frame 10",

just to see what they are like.


http://www.hostboard.com/forums/hbmc...jpg?1319702842

no the seller did not bill them to me as high quality. I found the specs and Ive done some tests myself; they are not co
pletly terrible but are not anything special. They are quake-15s. I only mentioned a deal because it was overstock and I got 4 for the price of one. I really do apologize for the bad mouthing, AK is a good site, just gets annoying at times.

Just looking at the page and the quoted 90 dB sensitivity would scare me off.

MCM is a much better source for cheap stuff. Honestly, I would sell them. But from there on your own.

Steel framed units in general are shorter xMax, which is gonna severely limit them in any modern horn. If I had to use them, I'd just do simple bass reflexes, and upgrade at the first opportunity.

Quote:

---

Originally Posted by tomt

you might get one of these -


Dayton Audio DATS Dayton Audio Test System 390-806



`````````````````````````````````````````



seismic audio is billed as musical instrument stuff.

i was thinking about getting the cast frame 10",

just to see what they are like.

---

Do yourself a favor Tom, get these instead.

MCM Audio Select 10'' Die Cast Woofer with Paper Cone and Cloth Surround - 100W RMS 8ohm | 55-2961 (552961) | MCM Audio Select


Sensitivity: 96dB (W/M)
Impedance: 8ohm
Re: 7.2ohm
Le: 0.989mH
Frequency response: 52Hz~4KHz
Fs: 52Hz
Qts: 0.29
Qes: 0.324
Qms: 2.6
Vas: 55.8 liters
Xmax: 3.5mm
better yet
MCM Audio Select 10'' Die Cast Professional Woofer - 250W RMS | 55-2981 (552981) | MCM Audio Select

Rigid die cast frame
Treated paper cone
Treated cloth accordion surround
2" high temperature voice coil
40oz. vented magnet Specifications:
Sensitivity: 93dB (W/M)
Impedance: 8ohm
Re: 6.3ohm
Frequency response:
35Hz~3.5KHz
Fs: 41.8Hz
Qts: 0.54
Qes: 0.655
Qms: 3.08
Vas: 58.08 liters
Xmax: 6.5mm

What is a good sensitivity to look for in better drivers? I probably will do what you said and just throw these in reflexes and procure some better drivers at a later date.

96-98 dB/2.83 V/m

GM

To expand on GM's post, let's take the lowest figure he posted of 96. Yours are 90. A good woofer will be as loud with 75 watts as yours are with 300. Crap woofers will kill your headroom as the amp is working harder.

That, or use four 90 dB speakers at 4x the space, cost in lieu of just one 96 dB speaker.

GM

i had a pair of altec 421-8lf's that measured with the 'woofer tester2' at 104db/watt

Quote:

---

Originally Posted by valhallax

i had a pair of altec 421-8lf's that measured with the 'woofer tester2' at 104db/watt

---

At the one meter distance? 104 sounds high for those. In an A7 box the horn should be worth maybe 5 db.

with the woofer tester one places the woofer in a stand and it measures the parameters. we set up for a gig, they were in a-5 cabs, after several hours of the drummers dm pro trigger rig, the eff was down 6 dbs. those were pre sub days...
ive also rea where early woofers tolerances were so tight, to gain effeciency, that the coils would lock up after getting hot

The old coils were not heatsinked well. If overpowered they go 'out of round' and can rub or lock up.

Quote:

---

Originally Posted by valhallax

with the woofer tester one places the woofer in a stand and it measures the parameters.

---

But the measurement has to be taken SOMEWHERE, ie at some distance from the cone. If you measure a foot from the cone, you will need to knock off 4.5 dB or so. Otherwise you can not communicate with others, and your box designs simulation will be off. TS parameters efficiency is at one watt/one metre, and all box design programs I know of use that standard.

Doesn't the woofer tester just calculate by using a comparison sweep? It doesn't measure efficiency as far as I know. It makes an educated guess.

the only 'one watt at one meter' physical tests were done with the bf titan 48s i built and ran several woofers through. took awhile setting up the test rig, learned a little tho

The woofer tester I have (DATS), does impedance sweeps, and then calculates t/s params from that. You just connect it straight up to the VC, and it generates the sweep, and measures the drivers response via electrical feedback from the VC. Here's a sample display of a t/s param measure I recently did on an Altec Model 14 woofer:

http://www.hostboard.com/forums/

You're correct OG, that it does not calculate efficiency, rather you have to supply that in order to get at Vas. Or there are several other methods to get there as well (added mass is a typical one). This particular test kit also has a signal generator, oscilloscope, and L/C/R tester included... very handy. I recommend it.