Someone check my work? Eminence BP102-4 into a Len Moskowitz cab

kraigo · #1 12-03-2010, 01:23 PM

I have a cab that I've been running the wrong driver in for years because the original driver was long out of production.

I built the original cab. It's the Len Moskowitz compact 1x10, the cab from this article: http://www.core-sound.com/bottom-article.html

The quick stats are that the cab is 1.6 ft^3, tuned to 31 Hz. The crossover is 24 dB/octave at 800 Hz. It's a four ohm cab.

The woofer that's in there now is an eight ohm Dayton. It's a bit mid heavy, but has been working surprisingly well.

The speaker I just ordered is an Eminence BP102-4. T/S parameters can be found here: http://www.eminence.com/pdf/LEGEND-BP102-4.pdf. The WDR file that I've created is available on request. I'd like to have someone (greenboy) host it.

My results are that I'll have an F3 around 52Hz and have about a -3dB hole at about 725Hz. Low B handling should be excellent.

These guys had the best price on the BP102-4, BTW: http://www.bltsound.com/

Anyway, if anyone is curious enough to model this and let me know if I've made a colossal blunder, I'd certainly appreciate it.

KO

greenboy · #2 12-03-2010, 02:37 PM

Hmmm, I used to have that driver up in there. Until zeronyne, moderator over at the Bass Player Mag lowdownlowdown forum actually restores my ftp access login (lost during change from software compatible with Windows 7 64-bit, and a catastrophic hard drive failure), well, I'm screwed for hosting anything else.

billfitzmaurice · #3 12-03-2010, 02:55 PM

Quote:

Originally Posted by kraigo

Anyway, if anyone is curious enough to model this and let me know if I've made a colossal blunder, I'd certainly appreciate it.

KO

BP102 will work a lot better than the original specified Peerless. But being a 1x10 don't expect miracles.
I don't take lightly to criticizing other designers work, but this one was totally flawed, from the choice of drivers to the 3/4" MDF construction.

kraigo · #4 12-03-2010, 09:09 PM

To be fair to Len:

1) This was his first bass cab.

2) This was before the internet exploded and finding driver parameters was as easy as going to the manufacturer's web site.

3) The Vance Dickason book was one of the few resources available to a beginning speaker designer.

4) The cab isn't really that bad.

5) That article was a very good first introduction to a lot of the concepts involved in speaker design and it really taught me, and probably a lot of others, quite a bit.

Thanks for the reply, both of you. This cab does fine for what I need it to do. It's for small church gigs and coffee houses.

KO

Growly Lytes · #5 12-05-2010, 08:58 PM

Good Ta Hear
BP102 Rockin

kraigo · #6 12-09-2010, 06:49 PM

The speaker came in today. The Dayton (Parts Express) woofer has a much larger magnet structure than the Eminence BP102-4

I left it in free air and ran a swept sine wave from 34Hz (Fs of the BP102-4) up two octaves for a little over an hour at a moderate volume to loosen the surround. Yes this will happen naturally through playing, but I wanted to give it a head start and it was cheap and easy to do.

Then I took the signal generator software and dumped a swept sine wave from 30 Hz to 2K Hz. I put an omni small diaphragm condenser about two feet back and recorded the eight ohm Dayton in the cab. I left everything in place and swapped out the speaker and repeated.

Perhaps the results won't surprise anyone: Below the crossover frequency the BP102-4 is about 3 db louder than the Dayton. This is surely due to the fact that the BP102-4 is a four ohm speaker and the Dayton is an eight ohm. A bit more surprising to me, being a relative novice at crossovers is that above the crossover frequency the mid horn was about 3 db louder when it was running against the (8 ohm) Dayton than it is now with the (4 ohm) Eminence.

The end result is that the cab now has more sensitivity from 30 Hz to 800 Hz (crossover frequency) and less sensitivity from 800 Hz on up. I'm still not sure if this was completely necessary. I'll probably appreciate the enhanced low end for tone, but I suspect that I might miss the enhanced midrange for hearing myself.

Still, all in all it's a nice sounding little cab. No, it doesn't do loud. It's moderately small, it sounds nice and for those times that you aren't duking it out with a guitarist and drummer, it's a really nice option to have.

KO

Added: My fretless five string sounds awesome through this thing. It really is a nice balanced cab, to this hack's ear anyway.

kraigo · #7 12-09-2010, 07:25 PM

I might add that I was pretty surprised to see how many weird peaks and valleys there were in the recordings. The happened at roughly the same time to both the Dayton and Eminence tracks. I don't really think they were the result of the cab, but the result of the room. I _WAS_ using omni mics, after all.

KO

Bassdirty · #8 12-09-2010, 07:36 PM

Quote:

Originally Posted by kraigo

.... compact 1x10...
... Low B handling should be excellent...

Quote:

Originally Posted by billfitzmaurice

But being a 1x10 don't expect miracles.
.

+1

JMO?

BurningSkies · #9 12-09-2010, 07:45 PM

Quote:

Originally Posted by kraigo

Perhaps the results won't surprise anyone: Below the crossover frequency the BP102-4 is about 3 db louder than the Dayton. This is surely due to the fact that the BP102-4 is a four ohm speaker and the Dayton is an eight ohm. A bit more surprising to me, being a relative novice at crossovers is that above the crossover frequency the mid horn was about 3 db louder when it was running against the (8 ohm) Dayton than it is now with the (4 ohm) Eminence.

Possibly explained by summing in the area of the crossover?

kraigo · #10 12-09-2010, 08:02 PM

BassDirty: Yes you can get good low frequency response in a 1x10. You just can't get it loud in a small cabinet. The cab is of moderate size, smaller than a 2x10 but still pretty ample for a 1x10. The drivers (the original Peerless, the Parts Express driver and the BP102) all put out copious amounts of low end at the expense of volume.

This cab gets used in situations where I'm not dealing with rock and roll volumes. It sounds really, really good. Very full, very even. And I can overpower it pretty easily with an amp that does "only" 400 watts at four ohms (my ancient AMP BH-420). That's OK as long as I know I'm not duking it out with a rock drummer and a Marshall stack.

KO

kraigo · #11 12-09-2010, 08:05 PM

Quote:

Originally Posted by BurningSkies

Possibly explained by summing in the area of the crossover?

It's too late to mic up each driver separately to observe cross over effects. I tend to think it has more to do with the way that the eight ohm driver was loading the crossover.

If you're so inclined I could MP3 resultant recordings and e-mail them to you.

KO

kraigo · #12 12-09-2010, 08:09 PM

Does anyone know of a software signal generator that displays frequency as it sweeps? I'm going to be doing a fair amount of testing for both free air resonance and cabinet tuning and none of the tone generators I've found will do it. I'm going to have to set up a softsynth and cross reference musical tones to their attendant frequency, which is moderately course (half step resolution), unless I find something a hell of a lot better than I've found so far.

KO

billfitzmaurice · #13 12-09-2010, 08:18 PM

Quote:

Originally Posted by kraigo

Perhaps the results won't surprise anyone: Below the crossover frequency the BP102-4 is about 3 db louder than the Dayton. This is surely due to the fact that the BP102-4 is a four ohm speaker and the Dayton is an eight ohm. A bit more surprising to me, being a relative novice at crossovers is that above the crossover frequency the mid horn was about 3 db louder when it was running against the (8 ohm) Dayton than it is now with the (4 ohm) Eminence.

Are you using the 8 ohm woofer with a 4 ohm crossover? If so the transfer function will be AFU, as will be the resulting response.

kraigo · #14 12-09-2010, 08:22 PM

Quote:

Originally Posted by billfitzmaurice

Are you using the 8 ohm woofer with a 4 ohm crossover? If so the transfer function will be AFU, as will be the resulting response.

Indeed I was. Not any more - it's four ohm all the way now. Not that the added efficiency means anything given amps of today, but the response seems more even to my heathen ears.

KO

Growly Lytes · #15 02-16-2011, 07:02 PM

They have their natural bass within, if you want more mid cut the bass back.
Yes they do lack some mids & highs but this can be a great thing.As ive learnt from listening & playing them & reading other posts im not the only one in the "anti-highs" boat.I cant stand highs & whatever the BP has in the mids is enough that i can hear it & the highs are there but arent in your face like some tens.
Why do so many bass players cut out their tweeters or use only 15` speakers with no mid drivers or tweeters ?
Its because they produce that low-end thump that you feel when you play.
BP102 wont give you that top-end glassy sound but they have that piano precision sound, clean & rumbly.Clarity & thump in the lower registers under 800hz.If you want more then the BP can give in the mids & highs use a mid & tweeter with them you cant go wrong.Though for me they kill it "as is".
They were made to be played with no eq " imo.....flat eq. Thats when they sound great to me !

kraigo · #16 02-16-2011, 07:52 PM

I typically play an Alder bodied P-Bass (maple neck) with flats fingerstyle. My cab has a mid that can get into the 7KHz range as I recall, but the signal isn't very toppy. I don't mind a modern cab. I like to have the low end available to the cab, but I usually keep the amp voiced neutral.

Nothing Earth shattering. I'm happy with the BP102-4. I have the mid's L-Pad turned all the way up though. I don't think I'd like the 102 without more upper mids being picked up by something.

Added: The eight ohm speaker I took out has more low end handling than the BP102 and more power handling. I'm going to build some small three way full range cabs out of the pair I have.

will33 · #17 02-16-2011, 08:14 PM

Quote:

Originally Posted by kraigo

Indeed I was. Not any more - it's four ohm all the way now. Not that the added efficiency means anything given amps of today, but the response seems more even to my heathen ears.

KO

-1

For a simple example, use this calculator http://www.diyaudioandvideo.com/Calculator/XOver/ and look at how far off your part values are halving the impedance of the driver use, let alone everything else that goes into a crossover. The differences you're hearing have more to do with true crossedover frequencies, electrical mishaps and many more things than I have the knowledge to explain than they do with 3db sensitivity differences or even response profiles of the speakers used.

The bp102 will likely be the superior choice if incorporated properly.

kraigo · #18 02-17-2011, 06:40 AM

The cab was originally designed to be four ohm through and through. The woofer died of abuse and boneheadedness early in its life cycle. I ended up with a regular gig where a 1x10 would be ideal and it would be convenient to just leave a cab. I found a great deal on a 10" woofer and put it in the cab. It was eight ohm. In theory it was a bad thing to do, but in practice it worked out OK. I think the woofer was handling the bulk of the signal and the crossover/mid weren't a huge issue. It covered the gig for well over five years with no real issues.

But when I found the BP102-4 as well as an identical woofer to the one currently in the cab it seemed the only thing to do was to get the BP102 and put that cab right while freeing up the existing woofer for other duties. Like I said, the cab has changed for the better now that the impedances are back to what the crossover was designed for.

In short, I don't think the post deserved the '-1'.

KO