I am trying to use an existing wood enclosure of 0.30 cubic feet interior area to house two 3 inch full range speakers that have specs calling for .02 cubic feet sealed, .05 cubic feet vented area.
Here is what the speaker specifications say:
"Optimum Cabinet Size (determined using BassBox 6 Pro High Fidelity suggestion)
An enclosure 4 inches cubed would have a volume of 0.3 x 0.3 x 0.3 feet = .037 cubic feet, not too far off the .02 and .05 cu feet volume in the spec.
Would it be a mistake to put these speakers in the larger enclosure that I already have?
Here is what the speaker specifications say:
"Optimum Cabinet Size (determined using BassBox 6 Pro High Fidelity suggestion)
- Sealed Volume0.02 ft.³
- Sealed F3166 Hz
- Vented Volume0.05 ft.³
- Vented F382 Hz"
An enclosure 4 inches cubed would have a volume of 0.3 x 0.3 x 0.3 feet = .037 cubic feet, not too far off the .02 and .05 cu feet volume in the spec.
Would it be a mistake to put these speakers in the larger enclosure that I already have?
Yes It is. Even without box.
To make it simple, the specs of the driver gives you the type of the cabinet size of the load and type of the load (vented, sealed, etc) and how to play with it from this ideal base to setup the sound. It's the same even without box as you can see the listening room as a box itself !
In your case, it's relativly simple if the cabinet is sealed to reduce the volume of your enclosure by filling it with hard piece of wood by calculating the difference volume with the ideal one the simulation gives. It's even more simple as you can remove from the cabinet this piece of wood to listen to by yourself the difference.
It is more difficult if the load is vented as also the size of the vented port is an important parameter which has to be calculated as well.
You should have a look at Thiel & Small parameters on Wikipédia. There is also an excellent book to understand the basic of a speaker : speaker designing Cook book (Something like that) by V. Dickason, a classic than all the speaker diyers have all around the world. The Wikipédia will answer you enough if you don't want to tune more than your actual speaker.
To make it simple, the specs of the driver gives you the type of the cabinet size of the load and type of the load (vented, sealed, etc) and how to play with it from this ideal base to setup the sound. It's the same even without box as you can see the listening room as a box itself !
In your case, it's relativly simple if the cabinet is sealed to reduce the volume of your enclosure by filling it with hard piece of wood by calculating the difference volume with the ideal one the simulation gives. It's even more simple as you can remove from the cabinet this piece of wood to listen to by yourself the difference.
It is more difficult if the load is vented as also the size of the vented port is an important parameter which has to be calculated as well.
You should have a look at Thiel & Small parameters on Wikipédia. There is also an excellent book to understand the basic of a speaker : speaker designing Cook book (Something like that) by V. Dickason, a classic than all the speaker diyers have all around the world. The Wikipédia will answer you enough if you don't want to tune more than your actual speaker.
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Excellent! That's easy to add wood blocks inside the enclosure. I take it then that the space in the enclosure can be irregular, doesnt have to be symmetrical or rectangular - just need the correct volume of air space?
The enclosure is an old time radio cabinet - I will make it into a bluetooth speaker, using two 3 inch full range speakers inside (using a bluetooth/amplifier board).
How does putting two speakers inside affect the volume requirement - do I need double the space one speaker would require?
The enclosure is an old time radio cabinet - I will make it into a bluetooth speaker, using two 3 inch full range speakers inside (using a bluetooth/amplifier board).
How does putting two speakers inside affect the volume requirement - do I need double the space one speaker would require?
Yes, but experiment with 1" foam pads will also work AND gain you the benefit of reducing reflections and cabinet resonances. According to the sales literature, these sheets ADD volume though. I'd stick a sheet or two in and measure, before adhering. You don't need to cover the entire inner enclosure. Good results can be had with covering 1/3rd to 1/2 of a panel at a time to reduce standing waves and cabinet vibrations. I had assumed this was possible and then I saw Magico doing this with very similar (if not identical) materials. Maybe a combination of the sheets and wooden blocks will do it for you. Measurements are king! 🙂
Usually. The exceptions to this are if you have restrictive channels between sections, then it will appear that the box is larger at some frequencies than others. This is, in effect, a resonant tuned cavity. However joining several large sections together is safe.
Also, flat surfaces parallel to the driver run the risk of creating standing waves. So generally, you don't want to have a board 1" from the rear of the driver, which then opens up to an additional space.
Yes, you must add the volume requirement. That is, if each speaker requires 0.3 cubic feet, then two in an enclosure will require 0.6. Mind you this only works for identical, and symmetrically placed drivers. Alter either of those restrictions and this all goes pooh. 🙂
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Thank you so much Eldam and Erik. now I get it, I will create a sealed airtight enclosure, adding blocks of wood to achieve the specified interior volume.
I would like to use two of these speakers: http://www.parts-express.com/fountek-fr89ex-3-neodymium-full-range-speaker-driver--296-721
and a TDA7492P 50W+50W bluetooth/stereo amp board.
The speaker is rated 25 watts RMS and the amp 50 Watts per channel.
I see from the TDA7492P specs here http://www.st.com/web/en/resource/technical/document/datasheet/CD00211320.pdf
that at the 20 VDC I will be using for the board with 8 ohm speakers and THD at 10% the power output is 26.5 watts. Can these speakers can handle the power assuming I listen to classical type music?
The enclosure has a precut 7 1/2 inch wide opening for the original oval speaker, which I will replace with two 3" speakers that fit perfectly side by side.
It might be difficult to find 3" or 3 1/2" speakers to handle more power if that is a requirement.
Or maybe instead of 8 ohm speakers would 4 ohm speakers present a better option for power handling?
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The load of the driver given at PE is for 1 driver.
If you putt 2 you need a twice bigger cabinet.
Or find a driver which need half of the advised volume to allow you to putt 2 in the previous cabinet size.
There is more chance the new driver will have a lack of bass in relation to the one you want to replace. I believe this is possible to find the same shape today than the old driver. Look for in the car driver and look for the lowest F3 you can find for your sealed load like you made with your first post.
The Fr88Ex is a much better driver than the FR89ex. Both will not make too much bass in such load you describe imho ! The FR88Ex is an excellent driver and you can find a good design with only one per box and enough bass with a newer cabinet or an already kit (flat pack e.g.) : you can find both at P.E. . Your chalenge is to find the driver which feet to the volume of your box as you understood. Try also some Vifa driver like TC9 : as good as cheap ! (I don't know of the load needed : check it by yourself at P.E.). But a newer design will give you better result. To fix the old you have, you goal should be to manage the budget as low as possible to stay coherent with the whole system.
The power of the amp will not give you a lower bass. But the amp you link is certainly enough for the talked drivers. I advise you to ask in the Clas D amp section once you finish the caqbinet.
If the cabinet you have has only one driver, which is my understanding of your first post, you may ask in the Full Range section.
In your shoes, I wil stay on a same shape than the original driver with a car driver or a TV driver which are easy to find yet !
I will not buy expensive speaker in an old design without a big experience as the result without it is not given by the driver price.
If you putt 2 you need a twice bigger cabinet.
Or find a driver which need half of the advised volume to allow you to putt 2 in the previous cabinet size.
There is more chance the new driver will have a lack of bass in relation to the one you want to replace. I believe this is possible to find the same shape today than the old driver. Look for in the car driver and look for the lowest F3 you can find for your sealed load like you made with your first post.
The Fr88Ex is a much better driver than the FR89ex. Both will not make too much bass in such load you describe imho ! The FR88Ex is an excellent driver and you can find a good design with only one per box and enough bass with a newer cabinet or an already kit (flat pack e.g.) : you can find both at P.E. . Your chalenge is to find the driver which feet to the volume of your box as you understood. Try also some Vifa driver like TC9 : as good as cheap ! (I don't know of the load needed : check it by yourself at P.E.). But a newer design will give you better result. To fix the old you have, you goal should be to manage the budget as low as possible to stay coherent with the whole system.
The power of the amp will not give you a lower bass. But the amp you link is certainly enough for the talked drivers. I advise you to ask in the Clas D amp section once you finish the caqbinet.
If the cabinet you have has only one driver, which is my understanding of your first post, you may ask in the Full Range section.
In your shoes, I wil stay on a same shape than the original driver with a car driver or a TV driver which are easy to find yet !
I will not buy expensive speaker in an old design without a big experience as the result without it is not given by the driver price.
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I now understand that if two identical speakers occupy the same enclosure the enclosure should be double the cubic inches recommended for one speaker...but....
in this case I am putting the left and right stereo speaker in the same enclosure, so they will not be working together with identical signals.
So does that change the way to think about desired cubic area of the enclosure?
in this case I am putting the left and right stereo speaker in the same enclosure, so they will not be working together with identical signals.
So does that change the way to think about desired cubic area of the enclosure?
The problem with the FR88ex is that it only rates 15 watts RMS, vs 25 watts for the FR89ex so I dont think it can handle the 50 watts per channel of the amp (actually, is expected put out 26 watts per channel at 10% THD given use of a 20 volt power adapter).
I havent found a mono bluetooth amp board so I think my only choice is to put two 3"" or 3 1/2 " speakers side by side to use the existing opening. No real stereo effect but at least I can make use of the amplifiers power.
You are right, these speakers are too expensive, but they are small enough to fit and seem to have enough power handling for the amp.
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you might want to consider these. HiVi B3S 3" Shielded Aluminum Driver Square Frame
They are cheap but a well known high value three inch.
I have used similar 3" drivers with similar power rating for classical with more power than you're talking about and had no issues. Dont expect any bass. I personally find a three inch on its own quite disappointing unless you have a sub.
They are cheap but a well known high value three inch.
I have used similar 3" drivers with similar power rating for classical with more power than you're talking about and had no issues. Dont expect any bass. I personally find a three inch on its own quite disappointing unless you have a sub.
If you proceed like that you will have a non pleasant result but a loss of money ! This story of 15 or 25 W doesn't tell you the whole story, and you're certainly don't look for power if you are saving such cabinet from the garbadge. If you need a good sound enough with powered amp/speaks , it's better to buy this for the same budget : Behringer MS16 - Thomann UK : plug your source, end of the story : you will be pleased by the sound.
Ok I understand now ! you want to save the aesthetic of your standalone cabinet, it's pretty and you want to keep it ! Notice it has a funy wave guide in front of the grill 🙂
I already saw the same shape of speaker you need with two tweeters embeded in front of the oval cone with the passive filter for channel summation for the standalone oval woofer !
I believe it was for TV, but not sure ! You may source that one. It's stay cheap and will give you better result with this box than the two drivers you plan to purchase ! IMHO.
Ok I understand now ! you want to save the aesthetic of your standalone cabinet, it's pretty and you want to keep it ! Notice it has a funy wave guide in front of the grill 🙂
I already saw the same shape of speaker you need with two tweeters embeded in front of the oval cone with the passive filter for channel summation for the standalone oval woofer !
I believe it was for TV, but not sure ! You may source that one. It's stay cheap and will give you better result with this box than the two drivers you plan to purchase ! IMHO.
I found a picture to illustrtate my thought : RETROSOUND Speaker 5''x7'', 127x178mm (pair), Neodym | STEREO - SVC | 127mm x 178mm (5" x 7") oval | Coaxial Speakers | Loudspeakers
there are at any prices, here it is just a picture I googled fastly !
Did you try also the ressource of forums specialised in old radio, they should have already the solution ! Here the diffivulty is the radio has a little volume for what people like to do here. I don't remember to have seen a mono point source speaker for desktop computer for instance which could match your need !
there are at any prices, here it is just a picture I googled fastly !
Did you try also the ressource of forums specialised in old radio, they should have already the solution ! Here the diffivulty is the radio has a little volume for what people like to do here. I don't remember to have seen a mono point source speaker for desktop computer for instance which could match your need !
oh, technically yes! 🙂 You should separate the enclosure then!
One thing to think about though, you could approach this more as an open baffle design.
If you are using smaller drivers, say 5" or smaller in a larger enclosure, you could get away with it with a little EQ and leaving the back wide open. I know very little about the technicallities of an OB design though. It's just a thought.
Best,
Erik
Thanks for the help Eldam, sharing your expertise. I just bought the kindle book: "Introduction to loudspeaker design by John Murphy" and will finish it tomorrow, I hope, so I can get a better background. Based on your input, the project is on hold pending getting a better design that will have a good probability of having good sound.
Although this oval speaker you found will fit the cabinet well, specifications are not provided. I'll look for others that are similar.
I really would like to use this cabinet if a good design can be worked out, once completed (maybe the wood refinished), it will be very classy, a real retro look.
You advise the two full range speakers side by side wont have good sound. Also poor bass. I am going to investigate the idea of a woofer/tweeter combination with crossover.
Also I will look into bridging this amplifier to be able to use it as mono without the stereo separation complicating the design.
I will also look at the old radio forums, as you suggest, and see if someone has tackled this already.
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Thanks Erik. I'm going to look into your idea of separating the cabinet for left and right stereo speakers. Maybe add a crossover and woofer. I need to learn about open back and vented enclosures now.
So many angles. I had no idea. But if there is a way to get good sound with this cabinet, I am going to find it and do it. You have helped me know a bit more about what I now need to study.
You're welcome Skyler,
I'm not an expert here, just an enthusiast fascinated by sound reproduction.
The link I provided was just to illustrate the concept I talked about, I'm not advising this driver in particular !
The advice of Erik can work as well, he advertised you about bass limitation already, but will ask wood work to allow a proof front bafle with two holes for the drivers ! Some works with cheap foam sandwiched paper with a cutter 😉.
There are certainly a lot of way to proceed, the experienced enthusiasts could give here.
You should keep in mind the following ideas imho :
keep the budget low
look at the specs at Part Express about the cubic size load
Try to find a driver with the advised load which go the lowest possible in the low end
Stereo effect is hard to produce when comming from a mono cabinet !
If it's not a one shoot project, keep your money for a kit if you plan to invest time with the sound reproduction efficienty as main goal.
DIY can cost more than brand new sometimes. Look at the first prices with JBL, Behringer e.g. for a good sound quality/cost ratio ! (a lot of good amplified speakers on the markett).
Good luck with your project, this little radio is nice and I'm sure many have already suceed with similar project and good sound enough 🙂.
I'm not an expert here, just an enthusiast fascinated by sound reproduction.
The link I provided was just to illustrate the concept I talked about, I'm not advising this driver in particular !
The advice of Erik can work as well, he advertised you about bass limitation already, but will ask wood work to allow a proof front bafle with two holes for the drivers ! Some works with cheap foam sandwiched paper with a cutter 😉.
There are certainly a lot of way to proceed, the experienced enthusiasts could give here.
You should keep in mind the following ideas imho :
keep the budget low
look at the specs at Part Express about the cubic size load
Try to find a driver with the advised load which go the lowest possible in the low end
Stereo effect is hard to produce when comming from a mono cabinet !
If it's not a one shoot project, keep your money for a kit if you plan to invest time with the sound reproduction efficienty as main goal.
DIY can cost more than brand new sometimes. Look at the first prices with JBL, Behringer e.g. for a good sound quality/cost ratio ! (a lot of good amplified speakers on the markett).
Good luck with your project, this little radio is nice and I'm sure many have already suceed with similar project and good sound enough 🙂.
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You could probably build a box inside the cabinet with the electronics surrounding it. You might even be able to remove the original baffle and replace it with your new enclosure that will have a similar grill covering. I would go with ported for bass extension and efficiency. Also, there is usually not a problem putting 2 like speakers in 1 enclosure because low frequencies are almost always recorded in both channels. Have you decided on a Bluetooth module? If it is strictly a Bluetooth speaker, consider getting a USB Bluetooth audio receiver like the one below. They aren't plagued with the noise that some of the modules have.
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Quote: I am going to investigate the idea of a woofer/tweeter combination with crossover.
I just had an idea, it might be neat to put the woofer and tweeter in your retro radio cabinet, refinish it make it look old-school cool etc. Display it prominently on a nice shelf towards the left side of your room. Then build another box with same internal volume and baffle width, same drivers, and hide it somewhere towards the right side of the room.
I just had an idea, it might be neat to put the woofer and tweeter in your retro radio cabinet, refinish it make it look old-school cool etc. Display it prominently on a nice shelf towards the left side of your room. Then build another box with same internal volume and baffle width, same drivers, and hide it somewhere towards the right side of the room.
I am in the process of reading a book about speaker enclosure design, and had concluded that my idea was just not feasible. No way to get good sound. Your idea just might be doable if I can find woofer and full range speakers to fit side by side in the 3.5" x 7" opening. But the woofer, at 3.5 inch diameter would be too small, no? If the woofer faces out the rear wouldnt the timing of the front speaker and rear woofer be off, mieeting the ear out of sync?
I read yesterday that even bluetooth 4 sound quality is significantly below what it be if it was a wired system. .
A 3.5" woofer would be more like a glorified midrange. And I never had that idea! Can you post a picture with something for scale ? I honestly am confused.
While you are looking at enclosure design, a transmission line may be something that works for you. Bose has used them with success in their "Wave" series of radios. If your project is that small it couldn't hurt.
Best,
Erik
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