cabinet components questions. crossovers

in case some of you didnt catch it, eric and i were having some back and forth about ohms law. it was a good excercise as this is important information for bassists to be familiar with. eric posted a lot of useful information there.

the question arose about what was going on with my rig.

two speaker jacks comming out of the back of the amp, paralled with a minimum load of 4 ohms.

i have 2, 8 ohm cabinets, one with an extension out jack paralled.

either way, amp to cabinet - amp to cabinet, or, amp to cabinet to cabinet, its still paralleled @ 4 ohms.

so why do the speakers sound so much clearer, amp to cabinet to cabinet?

eric stated that it might have something to do with the crossover in the cabinet with the out extension jack. i'm thinking yeah, but it only crosses over to the hf driver. i'm also thinking that the key is to have a low frequency crossover to the bottom 15" cabinet, so the problem is that there isnt one.

heres the problem .............

i continue to search for information on function, specs and installation of crossovers ... i think the original hartke crossover is not the right specs for what i'm trying to do with it (with higher wattage, aftermarket speakers). i have no idea how they work or what all the specs numbers mean. i wouldnt know what i was looking for to purchase one. all i do know is they help the correct frequencies go to the right speakers for those frequencies. i.e. low frequencies would be crossed over to my 15", the mid frequencies would go to my 10"s and another crossover would send the high frequencies to my hf driver.

the best information and place to buy them thus far is .....
http://usspeaker.com/crossovernetworks1.htm
i've dealt with them before and they are a big help and have decent prices.

if anyone can give me some direction as to where to educate myself about these devices or someone who would help me with it, iddid be much appreciated and i'll forward such findings to the bass tremolo fanatics message board.

thanx.

this was quite helpful .......

http://www.termpro.com/articles/xover2.html

Great links, MadMike!

And I apologize for not being able to further clarify what is happening with your set-up. I wish I had the answer, since I want to know what exactly is going on.

no problem. i believe you were right ... its the original crossover in the hartke. its not the right crossover for what i'm trying to do with it.

since i dont know much of anything about crossovers, i'm trying to educate myself so i can get the right one (or two). dealing with frequencies and Hz is something that i'm really not familiar with.

a crossover will distribute the range of sound across the frequencies of drivers that i have in my rig for a cleaner sound.

took me some time; there is very little information out there. i believe this is because companies just want you to buy bass rigs complete or, if you have a problem, just buy a new head or cab.

for me ... the rigs that i would prefer to use i just cant afford. mesa, hughes and kettner and ashdown come to mind. with my budget, i just gotta make the best with what i got meaning replacement speakers and hf drivers, cabinet manipulation and different components.

again, eric was right. with the different aftermarket speakers and hf driver i was using in a stock sampson setup, the right frequencies werent going to the right speakers from the original crossover. i set out to find out how to fix this. heres the short answer ... because thats what i got that got me to the solution.

most important and remember this ...... higher frequency watts are easy. if you have a speaker thats 300W thats sensitive from 63Hz - 3.7kHz and a speaker thats 300W sensitive from 40Hz - 2kHz driven equally (wired) the wattage is gonna go to the higher frequency more easily and drive (overdrive in my case) that speaker while the low end, 40Hz - 2kHz speaker will be signifigantly lower db's.

i dont understand the spec parameters and equations to determine what crossover would provide what i was looking for. i sat with a calculator and numbers scribbled in a notebook with ameture and pro tech mumbo jumbo for about 2 weeks and i couldnt get it right. i needed some help so i contacted a tech a u.s. speaker (link in message above). i told him what i was dealing with and gave him the specs and without hesitation he told me to purchase this one ...........

http://usspeaker.com/px-ii5k0-1.htm

bam!

i installed this crossover yeaterday. it took 15 minutes to install. now, i havent had the chance to drive it at top level, but i did crank it once and first thing i noticed was reaching a pretty high level with the gain only at 1/4 ... much better than before. the hf driver and 10"s arent sucking all the power, for lack of better technical terminology. to reach this level before it needed to be turned up almost half and thats when the drivers would start to distort. i was suprised with no filters or effects, bass right into the amp, how clean and warm the tone was at a flat eq. rumbley, rumbley .........

$100 part making my rig sound this good. i was looking at going out and spending $3000 on a new mesa rig. this rig sounds just as good ... if not better than now.

i'm anxious to drive it at practice tomorrow to see just how loud i can go before the tone deteriorates. if everything is correct (all the specs match up?) it shud be more than i'de need for practice or a gig. i mean, i'm pushing 3ooW (with pre's and leveled effects) into 1000W worth of drivers ... it shud handle a lot!

the tech said the new crossover shud get me there. if its still not there (i like a lot of bottom end ... we are bass players, arent we?) u.s. speaker also recommended this one for my 15" cab ..........

http://usspeaker.com/px-b250-1.htm

i think i may need it, being a kahler user and divebombing ... gotta handle those lower frequencies.

i'll post my results.

i hope this will be helpful to anyone having similar problems. i was frustrated with the lack of information out there, but i need to let everyone know ... there are people out there who know their stuff and if i ask them, they are willing to help.

Ah-ha! Excellent sleuthing, MadMike!

So now we know that it's not only the crossover that governs how much each speaker gets hit with, but also the exact frequency response and sensitivity of the speakers themselves. Honestly, I had no idea that this was a factor, but now it makes perfect sense. It sounds like these are important things to consider when installing aftermarket speakers and/or crossovers.

You know, now that you've brought this to light, I do recall replacing speakers in some of my older cabs, and it seemed that there were times when the new speaker would either be louder, or not as loud as the others were. Like, say, in a 4x10. One of the 10's would blow, and I would buy some other brand of replacement speaker, only to discover that it clearly sounded different from the others. But since my rig was usually so loud to begin with, I never bothered to wonder why this was happening, instead merely writing it off as a condition of there being a different brand of speaker matched with the original ones.

all aftermarket speaker models and brands have different frequency ratings and i also believe that thos frequencies change with runs of batches.

example ... and eminence delta 10b i bought 2 years ago will sound slightly different than the new one i just bought. very slight and probably only an uptight perfectionist like myself would notice it or be annoyed by it. (i never claimed to be well)

ex#2 ... eminence delta 10b and a peavey sheffield 10 with the same specs will sound totally different if you could hear both at once ... and you wouldnt because the eminence would be louder (based on my experience only buying one delta on the cheap ... i needed to buy both and let go of the sheffields ... anyone wanna buy some 10" sheffields?).

then theres the issue i was having

my issue was different types of drivers. my speaker set up had much more options available for the wattage to go to higher frequency drivers ... i.e. the rx-22 (500Hz - 20kHz) and the 2 eminence delta 10b's (63Hz - 3.7kHz). the wattage was never making it to the 15" (where all the boom comes from) and going to the hf driver too much distorting it. i was getting alot of squealing high end (fun but not right) and limited lows. i'm lucky i didnt blow up my hf driver.

i'm going to practice now ................

i just re read my message and i'm realizing that i'm turning into a nerd.

"oooooh, the freqencies reverbirate with the synthesis process to induct into the copolymer of the polyvinylchloraphill ... glaven!"

i just need the glasses with the tape and i'll be good.

Welcome to my world!

So it seems prudent that if one were going to really go all out when re-doing a speaker cabinet (assuming one had the finances and the wherewithal to do this), that you would want to replace all of the speakers with the exact same type. I realize that this is impractical for many of us, and even overkill. Like if you had an 8x10 with a horn, that could get expensive, wasteful, and time-consuming, especially if you had only blown one of the speakers. A 4x10 less so, and a 2x15 even less so. Heck, at that point, it almost makes more sense to simply replace the cabinet.

Of course, the simplest solution would be to find the OEM parts to replace any blown components, but I realize this isn't always possible, especially with older gear. Or to replace the blown component with whatever was available, and simply learn to live with the differences. But this doesn't sound so great to me, especially now that you've pointed out the folly of doing it like this, MadMike.

true, true.

remember ... a lot of these speakers are designed as replacements for popular cabinets like kruegers and ampegs. sure, the batch runs would be slightly different but i think the differences would be less noticible per how many speakers are going with the replacement ... like 1 of 2 replacement in a 2x10 would be more noticable than 1 of 6 or 8 in a 6x or 8x10. what specs are correct? i'm not that much of a nerd yet ... thus my point of calling techs like they have working at u.s. speaker. they shud be able to get you something close, if not exact, instead of going out and buying a new ampeg cab ... they are pretty expensive.

i've always had trouble with the one speaker replacement matchups in 2x10 and 4x10's. in some instances, it was really noticable ... like, ew, that sounds horrible noticable.

with the new crossover ... my rig sounds great! practice yesterday was awesome. on multiple occasions my guitar player said ... "turn it down!". aaahahahahahahahahahaha!

getting much cleaner response at higher levels. i gotta go thru and change all my effect eq's now because i was pushing the low end to come out. most effect banks, i just turned the eq off or set it to flat and it sounded great.

i'm still gonna get the low end crossover because theres still too much power (low end frequencies) going to the 10's than i'de like. and also thought about like what eric was saying ... just get a new cabinet. this 15" i got is a getterby and isnt ported or volume (l x w x h) tuned correctly ... i may never get the proper sound out of it that i would get out of a deeper cabinet. more stuff to learn.

If you're going to replace your 1x15 anyways, you could always experiment with porting it yourself first to see if you might be able to get it to sound good. I don't mean going crazy with a tuned can, or anything. Just finding a spot on the front panel to punch a hole through. A hole about 3" across should yield some good results.

heres the deal with the 15" cab and the research i did.

i downloaded the winISD beta for speaker design. i tried out a few and this one seems to be the most easiest to use for an ameture like me.

i entered the specs for my 15" peavey black widow in the library and entered the existing cabinet dimensions of 24"W x 24"H x 13.5"D and got these results for optimum ports .......

1 port with 4.5" diameter requires a vent length of .92" (the cab walls are already .75") to get a vent mach of .15 (ideal being .1)

a 4.5" port wont fit with a 15" speaker in a 24" x 24" cab. ha!

this cab is single ported already without depth (.75"; theres no tube) at 2.5" diameter ... perhaps this is why bass is lacking.

lemme try a dual port spec .............

nice!

2 ports with 2.5 diameter with a vent length of .77" yields a vent mach of .12.

..... i just need more speed holes!

i think like eric and i were discussing ... its just time for me to go out and buy a new bottom cab ... this carvin is like 25 years old! i gotta do some shopping around to find the right one.

but if i'm going to buy a new cab ... then i can do some experimenting with this one!

That's the spirit!