I can't get no satisfaction... - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 31st March 2003, 09:48 PM   #1
diyAudio Member
 
nobody special's Avatar
 
Join Date: Oct 2002
Location: USA
Default I can't get no satisfaction...

Here's the deal:
I have a set of MTM's that I built a few years back when I didn't know quite what I know now about speaker building. I find myself not listening to my system much anymore for music, because it just sounds flat and lifeless to me. The midrange on these MTM's is good, and the sweet spot is nice, but I notice some combing effect, and it's driving me crazy! the bass is also lacking- especially the midbass. They sound too thin. I have come to the conclusion that I will leave this setup for my video / home theater, and build something else. I am under the impression that an augmented full range system would be my best bet- with a fullrange driver covering the critical 100-5kHz region, augmented by a tweeter of some sort, and a woofer on the bottom (possibly a TL?) Biamping or triamping is defenitely an option.
This is the idea I had in mind, but I am basically open to any suggestions... I NEED HELP FINDING MUSICAL NIRVANA! I really want to enjoy my system again. I am on somewhat of a budget, but it's not severe- more or less nothing super exotic, but I will consider all options. Let me know what you all think, if you don't mind. TIA.
Steve
  Reply With Quote
Old 31st March 2003, 10:01 PM   #2
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Just out of curiosity, did you compensate for spreading loss in your original xover? Failure to do so is an extremely common beginner error and one which can really rob music of vitality.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 31st March 2003, 10:12 PM   #3
diyAudio Member
 
nobody special's Avatar
 
Join Date: Oct 2002
Location: USA
Quote:
Originally posted by SY
Just out of curiosity, did you compensate for spreading loss in your original xover? Failure to do so is an extremely common beginner error and one which can really rob music of vitality.
Not quite sure what you mean there...
Are you talking bafflestep?
I had the crossover designed by madisound. The design is as follows:
two Vifa P17WJ's paralleled, and a Morel MDT-33 tweeter. The design looks pretty textbook- simple 2nd order @2200Hz with impedance compensation on the woofers. I think I went wrong by putting them in very narrow tower cabinets and tuning them lower for extension. Plus, for some unknown reason, the ports are high on the front of the cabinet, so there is not much floor reinforcement going on there, and little backwall reinforcement. I think the combination killed my upper bass and lower mids. The spacing on the MTM arrangement is fairly tight- both woofers hugging the tweeter. I still think the seperation of the woofers is causing some wierdness in the midrange. When you're in the sweet spot, they image unbelievably well. So well that they put a lot of speakers in the $1200- $2000 range to shame. The problems are with the weak midbass, which makes them sound very forward, and with the slight combing effect (which I will admit I am somewhat more sensitive about than other people). I was thinking of rebuilding them in wider cabinets with a more standard tuning in a standard MMT arrangement. What do you think?
  Reply With Quote
Old 31st March 2003, 10:21 PM   #4
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
Well, if you're using a cabinet that's narrower than the designer of the xover assumed, yeah, you'll get some mid-bass weakness. A simple thing to try is a passive RC eq circuit between pre and power amps. You can do the spreading loss (or baffle step, if you prefer) compensation electronically and it may save you some wood-cutting.

One more thing- with that driver combo, I'd be mightly tempted to go for an acoustic 4th L-R xover. These are some good drivers and a little bit of care can make them really sing.

When you say "combin," do you mean side-to-side or up-and-down?
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 31st March 2003, 10:22 PM   #5
diyAudio Member
 
apassgear's Avatar
 
Join Date: Nov 2002
Location: Viña del Mar, Torreon
Many times dull sound comes as a result of poor inductor quality with high DCR and core losses (if any).

Try some low DCR inductors and have all crossover connections soldered.

If the sound is still dull you can also try solid core speaker wire of good cross section.

What type of capacitors do you have on the crossover?
  Reply With Quote
Old 31st March 2003, 10:32 PM   #6
diyAudio Member
 
nobody special's Avatar
 
Join Date: Oct 2002
Location: USA
Sy,
Why would you go for the 4th order L-R? What would the benefits be?
Would you keep the MTM arrangement?
I really do like the tweeter (it is very natural), and I am happy with the midrange clarity I get... I just think I blew it in the cabinet design. Thanks for the suggestions, and please keep them coming. I am definitely open to redesigning what I have. As far as the comb effects go, it is in the horizontal "side to side" plane. Move an inch off the sweet spot, and there is a definite "dead" spot somewhere near or slightly above the crossover frequency. Move a little more and it's normal. It sends me up a wall sometimes!

Apassgear,

I used good quality low esr caps (multiple paralleled on the tweeter with a small value bypass). The inductors are also high quality heavy gage (on the woofer). I used an 18 gage on the tweeter, which is what the design called for (the filter was calculated using this value resistance). They are all perfect lay air core types.

Thanks for the comments... I look forward to hearing more.

Steve
  Reply With Quote
Old 31st March 2003, 10:56 PM   #7
diyAudio Member
 
apassgear's Avatar
 
Join Date: Nov 2002
Location: Viña del Mar, Torreon
Quote:
Originally posted by nobody special

Apassgear,

I used good quality low esr caps (multiple paralleled on the tweeter with a small value bypass). The inductors are also high quality heavy gage (on the woofer). I used an 18 gage on the tweeter, which is what the design called for (the filter was calculated using this value resistance). They are all perfect lay air core types.

Thanks for the comments... I look forward to hearing more.

Steve

Runing // midbass speakers the amp will see a low impedance which will call for some heavy amps.

Is your amp capable of supplying the needed power?

Other ideas are that something on the crossover is sucking power, once again, when running low impedance speakers your inductor should be a very low DCR type, I'm speaking of something like 0.02 Ohms maximum cored inductors with no saturation problems.

Of course capacitor are also resposible for power losses.

What type of capacitors are you using?
  Reply With Quote
Old 31st March 2003, 10:58 PM   #8
SY is offline SY  United States
diyAudio Moderator
 
SY's Avatar
 
Join Date: Oct 2002
Location: Chicagoland
Blog Entries: 1
The 4th LR will give you better control of the polar pattern. Typically, lower distortion and better power handling, too. It tends to be not as sensitive as other types to frequency response errors due to offsets in acoustic center between the drivers.

The caveat is that, as with other xover transfer functions, what you need to shoot for is a acoustic 4th order LR. In general, that will NOT be the same as an electrical 4th order LR, since the drivers contribute their own rolloffs.

MTMs tend to have narrower vertical dispersion than MMTs, but less lobing. That sounds a bit contradictory, but isn't; the rolloffs as you get out of the "beam" tend to be smoother with well-executed MTMs. Try reworking the xover, leaving the wood alone and see if you like that. Easy and reversable stuff first. If the vertical dispersion is still too narrow for your taste, then you can redo the cabinet.

Your combing may be a cabinet diffraction issue. Try some thick felt around the cabinet edges (on the front baffle) and see if that helps.
__________________
And while they may not be as strong as apes, don't lock eyes with 'em, don't do it. Puts 'em on edge. They might go into berzerker mode; come at you like a whirling dervish, all fists and elbows.
  Reply With Quote
Old 1st April 2003, 01:45 AM   #9
diyAudio Member
 
nobody special's Avatar
 
Join Date: Oct 2002
Location: USA
Quote:
Originally posted by apassgear



Runing // midbass speakers the amp will see a low impedance which will call for some heavy amps.

Is your amp capable of supplying the needed power?

Other ideas are that something on the crossover is sucking power, once again, when running low impedance speakers your inductor should be a very low DCR type, I'm speaking of something like 0.02 Ohms maximum cored inductors with no saturation problems.

Of course capacitor are also resposible for power losses.

What type of capacitors are you using?

Unfortunately, I am using a cheap receiver right now. It is a push-pull A/B design though, so it should be able to handle the load. Other amps I have tried made no difference in the bass. My inductors are the heaviest I could find. I think they are 12 or 14 gage on the woofers. The caps are Solen.
  Reply With Quote
Old 1st April 2003, 01:54 AM   #10
diyAudio Member
 
nobody special's Avatar
 
Join Date: Oct 2002
Location: USA
Quote:
Originally posted by SY
The 4th LR will give you better control of the polar pattern. Typically, lower distortion and better power handling, too. It tends to be not as sensitive as other types to frequency response errors due to offsets in acoustic center between the drivers.

The caveat is that, as with other xover transfer functions, what you need to shoot for is a acoustic 4th order LR. In general, that will NOT be the same as an electrical 4th order LR, since the drivers contribute their own rolloffs.

MTMs tend to have narrower vertical dispersion than MMTs, but less lobing. That sounds a bit contradictory, but isn't; the rolloffs as you get out of the "beam" tend to be smoother with well-executed MTMs. Try reworking the xover, leaving the wood alone and see if you like that. Easy and reversable stuff first. If the vertical dispersion is still too narrow for your taste, then you can redo the cabinet.

Your combing may be a cabinet diffraction issue. Try some thick felt around the cabinet edges (on the front baffle) and see if that helps.

I guess it won't hurt anything to try the fourth order. Actually, I had originally intended to go that route, but was told by Madisound that they prefer to find the optimum crossover for the drivers I specified (they actually were a little unfriendly and inflexible... I guess the customer isn't always right).
I really have to go back through the loudspeaker design cookbook and read up on this again. It has been a while.
As far as diffraction goes, I don't think it is the enclosure. They have 3/4" quarter rounded edges. Then again, I'm not so sure that a 3/4" radius would be effective at the frequencies I am having problems with, and felt is cheap. I'll give it a try.
The one thing going for me (and one of the reasons I chose the drivers) is that these drivers have a fairly smooth and wide response, so they should be easy to work with. I still think the cabinet is a problem. They're ugly anyway- it's a good excuse to start over. I think I will try lowering the xover point a little. With a fourth order and MDT-33's, it shouldn't be a problem.
Thanks again for the help (Sy and apassgear)
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



New To Site? Need Help?

All times are GMT. The time now is 05:30 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright ©1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2