# Rebuild of old front speakers (again)



## bob_cook101 (Dec 3, 2009)

I'm starting to rebuild a pair of speakers that I originally built back in the 70's. These originally started out with 8" woofers, (2) 4" midrange and a radio shack horn tweeter and a crossover. I later tried 12" woofers and have since gone to a 10" woofer, a single mid and kept the old horn. The system has just never had the bass and fullness that I would like so I'm looking to rebuild again. I enjoy woodworking and electronics and I'm comfortable doing both and look forward to spending some garage time.

The cabinets outer shell is made of laminated 3/4 MDF with a good quality 1/2 plywood so they are 1-1/4" thick and are finished with a "Fine line" veneer. Currently the baffle and back are 3/4 plywood which I'll probably replace with 2 layers of 3/4 MDF. Inside cabinet dimensions are 14"w 12"d 28"h. When I went with the 10" woofers I sectioned the bottom part of the cabinets and added a false back to reduce the volume to 14"w 8.5"d 22"h (all inside dimensions). I also added 2 ports based on the mfg recommendations. I bought the 10" woofers from speakerworks (dot net) part 10he67 expecting to have some really good results. Lets just say it's a work in progress at this point.

Now on to my problems/questions. I think that part of my problem comes from cheap mid range drivers, the old horns and a cheap crossover. The mids I have are Pyle part PDMR5 which have a higher efficiency than the woofers at 92db vs the 87.9 for the woofers. I played around with resistors in an lpad configuration which helped some. I also downloaded a free test program that I can use with my laptop and a microphone and did some testing. The results show spikes and dips all over the place with 30db variation from 70hz to 3000hz. There is a notable decrease at 350hz and a big increase at 400-500hz. Above 3000hz the level is fairly stable. In doing the testing I could tell that the mids were producing a lot of sound as low as 200hz although they are rated to 450 and crossed over at 800hz. What a mess huh?

A couple of other issues is that the drivers are not flush mounted. The tweeter and mid are mounted to the baffle from the front (not recessed flush) and the woofers are mounted to the back of the 3/4" baffle and with the gasket on the front that makes them really recessed. The original configuration had 2 mid range speakers in a row (horizontally) between the woofer and horn. When I went with one mid I left the speaker offset to the side from the others. In what I have been reading lately this is not good either.

So now it's time to start on some improvements. I want to keep the woofers since they are still in excellent condition, and seem to be of good quality and were fairly costly at $70ea. I can't find detailed specs on the mid range or horns and don't mind replacing them if someone has a good recommendation. I have read a lot lately about speaker building but I can't determine if the woofers are really suited for what I'm trying to do and I don't know how to pick a mid and tweeter and design a good crossover. I know building a crossover can be a lot of trial and error and don't mind as long as it doesn't get too expensive.

The other improvements I have planned are to go with 2 layers of 3/4" MDF on the baffle and replace the back with 3/4" MDF and add some internal bracing. Place all of the drivers in line and recess them so they are flush mounted and build a custom crossover. 

I would also welcome any advice on the size and placement of a port. The mfg recommendations differ vastly from what I have found in online calculators.

These speakers are used as the front mains in a 5.1 home theater system. We like to watch movies, TV programs and listen to CD's and FM in stereo. The room has a lot of hard surfaces with wood floor.

My center channel is a variation of the Cynosure project that I saw on parts express that I built last spring. It was a good project, all 3/4" MDF painted black and it sounds really nice. I tested it with the free program and the results are fairly flat from about 90hz on up. 

My sub is a KLH 12" 200w powered unit that is hidden in the corner of the room to the left of the entertainment center. I know a lot of people say let the sub do the work but I want the front mains to participate a good bit more than they currently do.

Receiver is Denon AVR-591 rated 75w at 8 ohms or 120w at 6 ohms. This receiver has the program to plug in a mike and it should auto calibrate all of the speakers. When I run it the results don't come out to my liking so I end up making some changes based on what sounds good. I'm hoping that after this rebuild I'll have better results.

This is my first post on any forum about this and any input is welcome. At present the speakers are dismantled and I'm going to start on the bracing and new baffles and backs. 

So to sum it up 
1. Are the woofers I have good for this application? I have the specs or you can find them on the net easily enough.
2.	Is the cabinet close to the size I should have for these woofers?
3.	Ported or sealed and if ported what size? I currently have (2) 1-3/4” x 4” ports in each cabinet. 
4.	Should I replace the mids and tweeters? If so with what?
5.	Any recommendations on crossover components?
6.	I would like to do all of this for under $100 or so unless the woofers have to be replaced.


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## fusseli (May 1, 2007)

What are you doing your measurements with? Have you measured or verified any t/s parameters on the woofers you'd like to keep? That being said, can you post all the specs you have on them? I looked up the Eminence 10HE67 and plugged into WinISD, and it looks like that woofer should play great and flat down to 30Hz (not too shabby!). Your ports are waaaaay too small though, you probably get a lot of port compression at high output levels. Strongly consider going to a single 4" vent or larger (4"x11" would keep the same tune). Vented is the way to stay for those drivers, also. Your cabs are a great size and tune for them, you just need bigger ports.

So, your cabs are about 2.7cuft and are tuned around 30Hz. Definately big enough for some decent output down to your subs range. The response decrease you mention at 350Hz could very well be baffle step if your current setup isn't compensated. If that's indeed the case then you're certainly missing out on appropriate lower midrange and upper bass efficiency. Judging by your woofer/cab combo, if you crossed these mains at 40Hz to your sub, you'd be able to rock pretty good. Your woofers in your cabs will handle well over 100W RMS with an HPF at 30Hz or above (109dB down to 30Hz... not too shabby at all!!).

You mentioned the name Pyle, so ya, I'd recommend you use about anything else. So you want new mids, tweets, and a suitable 3-way crossover? That might be tough to squeeze out of $100.

Oh an also, Denon makes a good AVR so I think you're pretty set with that. Also noteworthy, I think that these mains of yours should easily outstrip your 12" 200W sub when all is said and done. Do you keep your speakers in corners or against the wall? This is a pretty important factor. If the room is big and has lots of hard surfaces, you could probably clean up the sound a bit just by adding some discrete dampening to the place to get rid of some reflections...


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## 1Michael (Nov 2, 2006)

bob_cook101 said:


> When I went with one mid I left the speaker offset to the side from the others. In what I have been reading lately this is not good either.
> I don't know how to pick a mid and tweeter and design a good crossover. I know building a crossover can be a lot of trial and error and don't mind as long as it doesn't get too expensive.
> 
> 4.	Should I replace the mids and tweeters? If so with what?
> ...


The first issue I see is that you have changed out drivers which almost always requires a new Xover. Xovers are designed for the specific drivers, baffle and box. Then you removed one of the mids which, while having 2 mids is a very bad idea sound wise, would require again, a new Xover. Then I see you want to fix this for under 100$. Good luck with that.
I recommend you save up some more money and build something that has already been designed or get something from a store because what you propose will guaranty a bad listening experience:T
You can expect to pay at least the cost of the drivers. or in my world twice the cost of drivers for a Xover. 

https://sites.google.com/site/undefinition/diy-faqs-provendesigns


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## bob_cook101 (Dec 3, 2009)

Thanks for the quick replies. 

Michael, I would not mind building a proven design as I did in my center channel but I already have some good woofers and want to keep the cabinets since I have had them for so long. If I could find a design using this woofer I'm all in. In doing a google I didn't find anything about this driver, not even a mention.

Fusseli, The program I used is AUDMES and is a free download. I used an old microphone and it showed some results that seem to be correct. I used the frequency response tab to run a test at first but the results appeared a bit off from what I was hearing. I started running a test tone from Winisdbeta and just recorded the result shown on the spectrum analyzer tab on paper. I ran several tests from 40hz to 3000hz with and without the sub and then disconnected the horns, ran a test and disconnected the mids and ran a test. I even bypassed the crossover and ran some tones from 40 to 1000. I did this to see if the xovers were attenuating the sound but they were not. I have been reading a lot about speaker building and know not to send low frequencies to a tweeter and things like that but I just don't understand the magic of selecting a mid and tweeter and really don't understand the magic of how to design a xover. 

I should probably do some testing of the woofers while they are out of the box but don't really know where to start. Any suggestions are welcome as I have not seen anything online as of yet.

About your suggestion on the ports. I did hear some wind noise coming from the ports at low freq so bigger ports are probably in order. When you say 4" x 11" or larger, should I build the port in to the cabinet like in an "L" shape (side view) using MDF? I certainly don't mind doing that but probably need some guidelines as to where to locate it as I have read that port size and placement is very important. If it is to be a plastic port, I would need to use an elbow to get the length.

You also commented on the box size but I think the dimensions you were looking at were the overall inside dimensions as I had reduced the volume for the woofer (based on the mfg recommendations) to 1.2cuft. Do I need to knock out the material I installed to get the volume back up?

The room is 16' x 20' the speakers are on the sides of the Ent. center about 1' off the back wall and are 
about 6' apart. We have a large rug, leather couch, loveseat and 2 fabric chairs in the room. I have been wondering about adding something to absorb some sound. If I put some material behind the couches and behind the Ent. center (it's over 6' tall and 9' wide) would that help or does it need to be "in sight" of the speakers?

One last question, with this woofer is it a consideration to go with a 2 way system? I'm thinking not since the woofer cuts off at 1000hz. It would make the xover simpler. And as far as $100, I can go more I just don't want to get too crazy. I know xover components can get expensive but one thing I was thinking that may help is to make some adjustments in the receiver as there are a bunch of ranges of frequencies that can be adjusted. 

Thanks

Bob


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## 1Michael (Nov 2, 2006)

bob_cook101 said:


> In doing a google I didn't find anything about this driver, not even a mention.


No TS specs, no Xover. That means you will have to buy test equipment leaving no money left to solve the problem.


bob_cook101 said:


> and really don't understand the magic of how to design a xover.


That leaves one choice, a proven design, which means starting over.



bob_cook101 said:


> One last question, with this woofer is it a consideration to go with a 2 way system?


No.
The bottom line here is you do not have the capability to redesign this speakers Xover so contemplating porting or not is moot.


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## bob_cook101 (Dec 3, 2009)

Michael, I may have left out a few key items here. I have always used xovers but other than my center project I have always bought them pre-made. I now know that it is best to build a xover but I just don't understand how to calculate one nor do I understand how to properly select a mid and tweeter. I thought I could just cross at 800hz because my woofer is only rated to 1000hz and the mid is good to 7000hz so I could cross again at 5000hz and everything would sound great. The more I read the more I realize that there is a lot of science and math to this and even then trial and error to get it right. 

I do have the specs on the woofers and you can find them by doing a search for Eminence 10HE67. I bought them from a web site called Speakerworks back in 2004. The site is still selling these and they are US made so I was hopeful that they would work well. I just could not find anyone that has a tested application for these or I would not be on this site posting questions.

I probably should have started out by saying I'm not looking to build anything that is "Studio" quality here but I figure if I can use the woofers and I already have the cabinets I should be able go get a decent sounding pair put together without spending too much. The center channel sounds nice and I think I have just over $200 invested counting wood, parts, paint and all.


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## fusseli (May 1, 2007)

bob_cook101 said:


> Thanks for the quick replies.
> 
> Michael, I would not mind building a proven design as I did in my center channel but I already have some good woofers and want to keep the cabinets since I have had them for so long. If I could find a design using this woofer I'm all in. In doing a google I didn't find anything about this driver, not even a mention.
> 
> ...


I'd be happy to help you pull together a new design, but you're really going to need to re-evaluate your budget. Me helping you would entail fully simulated design though given the situation, which isn't a big deal considering the power and acclaim of the Jeff Bagby software. It'd be feasible to go economy on the Xover components, your call. I can about gaurantee something produced by simulation will sound a lot better than your current setup, albeit not a perfectly flat +/-1dB as a "proven design" should be. As far as your measurements go, with an old mic hooked up to a computer in-room, only take those as gee-whiz info. There's an extremely small chance those measurements will be accurate enough to design off of unless there's something about your measurement setup and skills you're not telling me hahaha. The EQ and other things on your AVR will be useful in the end, but shouldn't need to be relied upon for a legitimate speaker.

There are tweeters that can cross down to almost 1kHz, but it's gonna be close. Impossible to tell if the woofer can really handle that high without a response chart, all I found at Speakerworks are the T/S parameters for the Eminence 10HE67. Can you dig up a manual or spec sheet for it? You're probably better off sticking with the 3-way idea,although you're right it will be a more complex Xover. I quickly ran the recommended cab volume of 1.2cuft and 3x13" round port, and it looks fine. Doesn't play as low as the 2.7cuft, how did you block off that much internal volume?? The 4" diameter port I mentioned isn't necessary with the smaller box size, the 3" is just barely big enough though. You could use a vent-kit from Partsexpress or do a recess+chamfer with some PVC pipe.

That's a good thing that you like your speakers out into the room a bit, but as they are in their current form it's probably not helping anything. That will be good to know though when applying BSC to the Xover. I don't know what kind of dampening you have available or how aesthetic you like things. That's probably out of the question though due to the very limited budget.

Can you post pictures of your cabs and complete outer gemetry and dimensions?


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